draft-ietf-mext-rfc3775bis-08.txt   draft-ietf-mext-rfc3775bis-09.txt 
IETF Mobile IP Working Group C. Perkins (Ed.) IETF Mobile IP Working Group C. Perkins (Ed.)
Internet-Draft Tellabs Inc. Internet-Draft Tellabs Inc.
Obsoletes: 3775 (if approved) D. Johnson Obsoletes: 3775 (if approved) D. Johnson
Expires: April 8, 2011 Rice University Intended status: Standards Track Rice University
J. Arkko Expires: April 8, 2011 J. Arkko
Ericsson Ericsson
Oct 05, 2010 Oct 05, 2010
Mobility Support in IPv6 Mobility Support in IPv6
draft-ietf-mext-rfc3775bis-08.txt draft-ietf-mext-rfc3775bis-09.txt
Abstract Abstract
This document specifies Mobile IPv6, a protocol which allows nodes to This document specifies Mobile IPv6, a protocol which allows nodes to
remain reachable while moving around in the IPv6 Internet. Each remain reachable while moving around in the IPv6 Internet. Each
mobile node is always identified by its home address, regardless of mobile node is always identified by its home address, regardless of
its current point of attachment to the Internet. While situated away its current point of attachment to the Internet. While situated away
from its home, a mobile node is also associated with a care-of from its home, a mobile node is also associated with a care-of
address, which provides information about the mobile node's current address, which provides information about the mobile node's current
location. IPv6 packets addressed to a mobile node's home address are location. IPv6 packets addressed to a mobile node's home address are
transparently routed to its care-of address. The protocol enables transparently routed to its care-of address. The protocol enables
IPv6 nodes to cache the binding of a mobile node's home address with IPv6 nodes to cache the binding of a mobile node's home address with
its care-of address, and to then send any packets destined for the its care-of address, and to then send any packets destined for the
mobile node directly to it at this care-of address. To support this mobile node directly to it at this care-of address. To support this
operation, Mobile IPv6 defines a new IPv6 protocol and a new operation, Mobile IPv6 defines a new IPv6 protocol and a new
destination option. All IPv6 nodes, whether mobile or stationary, destination option. All IPv6 nodes, whether mobile or stationary,
can communicate with mobile nodes. This document obsoletes RFC 3775. can communicate with mobile nodes. This document obsoletes RFC 3775.
Status of this Memo Status of this Memo
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skipping to change at page 2, line 17 skipping to change at page 2, line 17
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 7
2. Comparison with Mobile IP for IPv4 . . . . . . . . . . . . . 8 2. Comparison with Mobile IP for IPv4 . . . . . . . . . . . . . 9
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 9 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1. General Terms . . . . . . . . . . . . . . . . . . . . . . 9 3.1. General Terms . . . . . . . . . . . . . . . . . . . . . . 10
3.2. Mobile IPv6 Terms . . . . . . . . . . . . . . . . . . . . 11 3.2. Mobile IPv6 Terms . . . . . . . . . . . . . . . . . . . . 12
4. Overview of Mobile IPv6 . . . . . . . . . . . . . . . . . . . 15 4. Overview of Mobile IPv6 . . . . . . . . . . . . . . . . . . . 16
4.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 15 4.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 16
4.2. New IPv6 Protocol . . . . . . . . . . . . . . . . . . . . 17 4.2. New IPv6 Protocol . . . . . . . . . . . . . . . . . . . . 18
4.3. New IPv6 Destination Option . . . . . . . . . . . . . . . 18 4.3. New IPv6 Destination Option . . . . . . . . . . . . . . . 19
4.4. New IPv6 ICMP Messages . . . . . . . . . . . . . . . . . 18 4.4. New IPv6 ICMP Messages . . . . . . . . . . . . . . . . . 19
4.5. Conceptual Data Structure Terminology . . . . . . . . . . 19 4.5. Conceptual Data Structure Terminology . . . . . . . . . . 20
4.6. Unique-Local Addressability . . . . . . . . . . . . . . . 19 4.6. Unique-Local Addressability . . . . . . . . . . . . . . . 20
5. Overview of Mobile IPv6 Security . . . . . . . . . . . . . . 21 5. Overview of Mobile IPv6 Security . . . . . . . . . . . . . . 22
5.1. Binding Updates to Home Agents . . . . . . . . . . . . . 21 5.1. Binding Updates to Home Agents . . . . . . . . . . . . . 22
5.2. Binding Updates to Correspondent Nodes . . . . . . . . . 22 5.2. Binding Updates to Correspondent Nodes . . . . . . . . . 23
5.2.1. Node Keys . . . . . . . . . . . . . . . . . . . . . . 22 5.2.1. Node Keys . . . . . . . . . . . . . . . . . . . . . . 23
5.2.2. Nonces . . . . . . . . . . . . . . . . . . . . . . . 23 5.2.2. Nonces . . . . . . . . . . . . . . . . . . . . . . . 24
5.2.3. Cookies and Tokens . . . . . . . . . . . . . . . . . 23 5.2.3. Cookies and Tokens . . . . . . . . . . . . . . . . . 24
5.2.4. Cryptographic Functions . . . . . . . . . . . . . . . 24 5.2.4. Cryptographic Functions . . . . . . . . . . . . . . . 25
5.2.5. Return Routability Procedure . . . . . . . . . . . . 24 5.2.5. Return Routability Procedure . . . . . . . . . . . . 25
5.2.6. Authorizing Binding Management Messages . . . . . . . 29 5.2.6. Authorizing Binding Management Messages . . . . . . . 30
5.2.7. Updating Node Keys and Nonces . . . . . . . . . . . . 31 5.2.7. Updating Node Keys and Nonces . . . . . . . . . . . . 32
5.2.8. Preventing Replay Attacks . . . . . . . . . . . . . . 32 5.2.8. Preventing Replay Attacks . . . . . . . . . . . . . . 33
5.2.9. Handling Interruptions to Return Routability . . . . 32 5.2.9. Handling Interruptions to Return Routability . . . . 33
5.3. Dynamic Home Agent Address Discovery . . . . . . . . . . 33 5.3. Dynamic Home Agent Address Discovery . . . . . . . . . . 34
5.4. Mobile Prefix Discovery . . . . . . . . . . . . . . . . . 33 5.4. Mobile Prefix Discovery . . . . . . . . . . . . . . . . . 34
5.5. Payload Packets . . . . . . . . . . . . . . . . . . . . . 33 5.5. Payload Packets . . . . . . . . . . . . . . . . . . . . . 34
6. New IPv6 Protocol, Message Types, and Destination Option . . 35 6. New IPv6 Protocol, Message Types, and Destination Option . . 36
6.1. Mobility Header . . . . . . . . . . . . . . . . . . . . . 35 6.1. Mobility Header . . . . . . . . . . . . . . . . . . . . . 36
6.1.1. Format . . . . . . . . . . . . . . . . . . . . . . . 35 6.1.1. Format . . . . . . . . . . . . . . . . . . . . . . . 36
6.1.2. Binding Refresh Request Message . . . . . . . . . . . 37 6.1.2. Binding Refresh Request Message . . . . . . . . . . . 38
6.1.3. Home Test Init Message . . . . . . . . . . . . . . . 38 6.1.3. Home Test Init Message . . . . . . . . . . . . . . . 39
6.1.4. Care-of Test Init Message . . . . . . . . . . . . . . 39 6.1.4. Care-of Test Init Message . . . . . . . . . . . . . . 40
6.1.5. Home Test Message . . . . . . . . . . . . . . . . . . 40 6.1.5. Home Test Message . . . . . . . . . . . . . . . . . . 41
6.1.6. Care-of Test Message . . . . . . . . . . . . . . . . 41 6.1.6. Care-of Test Message . . . . . . . . . . . . . . . . 42
6.1.7. Binding Update Message . . . . . . . . . . . . . . . 43 6.1.7. Binding Update Message . . . . . . . . . . . . . . . 44
6.1.8. Binding Acknowledgement Message . . . . . . . . . . . 45 6.1.8. Binding Acknowledgement Message . . . . . . . . . . . 46
6.1.9. Binding Error Message . . . . . . . . . . . . . . . . 48 6.1.9. Binding Error Message . . . . . . . . . . . . . . . . 49
6.2. Mobility Options . . . . . . . . . . . . . . . . . . . . 49 6.2. Mobility Options . . . . . . . . . . . . . . . . . . . . 50
6.2.1. Format . . . . . . . . . . . . . . . . . . . . . . . 49 6.2.1. Format . . . . . . . . . . . . . . . . . . . . . . . 50
6.2.2. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 50 6.2.2. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 51
6.2.3. PadN . . . . . . . . . . . . . . . . . . . . . . . . 51 6.2.3. PadN . . . . . . . . . . . . . . . . . . . . . . . . 52
6.2.4. Binding Refresh Advice . . . . . . . . . . . . . . . 51 6.2.4. Binding Refresh Advice . . . . . . . . . . . . . . . 52
6.2.5. Alternate Care-of Address . . . . . . . . . . . . . . 51 6.2.5. Alternate Care-of Address . . . . . . . . . . . . . . 52
6.2.6. Nonce Indices . . . . . . . . . . . . . . . . . . . . 52 6.2.6. Nonce Indices . . . . . . . . . . . . . . . . . . . . 53
6.2.7. Binding Authorization Data . . . . . . . . . . . . . 53 6.2.7. Binding Authorization Data . . . . . . . . . . . . . 54
6.3. Home Address Option . . . . . . . . . . . . . . . . . . . 54
6.4. Type 2 Routing Header . . . . . . . . . . . . . . . . . . 56 6.3. Home Address Option . . . . . . . . . . . . . . . . . . . 55
6.4.1. Format . . . . . . . . . . . . . . . . . . . . . . . 56 6.4. Type 2 Routing Header . . . . . . . . . . . . . . . . . . 57
6.5. ICMP Home Agent Address Discovery Request Message . . . . 58 6.4.1. Format . . . . . . . . . . . . . . . . . . . . . . . 57
6.6. ICMP Home Agent Address Discovery Reply Message . . . . . 59 6.5. ICMP Home Agent Address Discovery Request Message . . . . 59
6.7. ICMP Mobile Prefix Solicitation Message Format . . . . . 60 6.6. ICMP Home Agent Address Discovery Reply Message . . . . . 60
6.8. ICMP Mobile Prefix Advertisement Message Format . . . . . 61 6.7. ICMP Mobile Prefix Solicitation Message Format . . . . . 61
7. Modifications to IPv6 Neighbor Discovery . . . . . . . . . . 65 6.8. ICMP Mobile Prefix Advertisement Message Format . . . . . 62
7.1. Modified Router Advertisement Message Format . . . . . . 65 7. Modifications to IPv6 Neighbor Discovery . . . . . . . . . . 66
7.2. Modified Prefix Information Option Format . . . . . . . . 65 7.1. Modified Router Advertisement Message Format . . . . . . 66
7.3. New Advertisement Interval Option Format . . . . . . . . 67 7.2. Modified Prefix Information Option Format . . . . . . . . 66
7.4. New Home Agent Information Option Format . . . . . . . . 68 7.3. New Advertisement Interval Option Format . . . . . . . . 68
7.5. Changes to Sending Router Advertisements . . . . . . . . 70 7.4. New Home Agent Information Option Format . . . . . . . . 69
8. Requirements for Types of IPv6 Nodes . . . . . . . . . . . . 72 7.5. Changes to Sending Router Advertisements . . . . . . . . 71
8.1. All IPv6 Nodes . . . . . . . . . . . . . . . . . . . . . 72 8. Requirements for Types of IPv6 Nodes . . . . . . . . . . . . 73
8.2. IPv6 Nodes with Support for Route Optimization . . . . . 72 8.1. All IPv6 Nodes . . . . . . . . . . . . . . . . . . . . . 73
8.3. All IPv6 Routers . . . . . . . . . . . . . . . . . . . . 74 8.2. IPv6 Nodes with Support for Route Optimization . . . . . 73
8.4. IPv6 Home Agents . . . . . . . . . . . . . . . . . . . . 74 8.3. All IPv6 Routers . . . . . . . . . . . . . . . . . . . . 75
8.5. IPv6 Mobile Nodes . . . . . . . . . . . . . . . . . . . . 76 8.4. IPv6 Home Agents . . . . . . . . . . . . . . . . . . . . 75
9. Correspondent Node Operation . . . . . . . . . . . . . . . . 78 8.5. IPv6 Mobile Nodes . . . . . . . . . . . . . . . . . . . . 77
9.1. Conceptual Data Structures . . . . . . . . . . . . . . . 78 9. Correspondent Node Operation . . . . . . . . . . . . . . . . 79
9.2. Processing Mobility Headers . . . . . . . . . . . . . . . 79 9.1. Conceptual Data Structures . . . . . . . . . . . . . . . 79
9.3. Packet Processing . . . . . . . . . . . . . . . . . . . . 79 9.2. Processing Mobility Headers . . . . . . . . . . . . . . . 80
9.3.1. Receiving Packets with Home Address Option . . . . . 79 9.3. Packet Processing . . . . . . . . . . . . . . . . . . . . 80
9.3.2. Sending Packets to a Mobile Node . . . . . . . . . . 80 9.3.1. Receiving Packets with Home Address Option . . . . . 80
9.3.3. Sending Binding Error Messages . . . . . . . . . . . 82 9.3.2. Sending Packets to a Mobile Node . . . . . . . . . . 81
9.3.4. Receiving ICMP Error Messages . . . . . . . . . . . . 82 9.3.3. Sending Binding Error Messages . . . . . . . . . . . 83
9.4. Return Routability Procedure . . . . . . . . . . . . . . 83 9.3.4. Receiving ICMP Error Messages . . . . . . . . . . . . 83
9.4.1. Receiving Home Test Init Messages . . . . . . . . . . 83 9.4. Return Routability Procedure . . . . . . . . . . . . . . 84
9.4.2. Receiving Care-of Test Init Messages . . . . . . . . 83 9.4.1. Receiving Home Test Init Messages . . . . . . . . . . 84
9.4.3. Sending Home Test Messages . . . . . . . . . . . . . 84 9.4.2. Receiving Care-of Test Init Messages . . . . . . . . 84
9.4.4. Sending Care-of Test Messages . . . . . . . . . . . . 84 9.4.3. Sending Home Test Messages . . . . . . . . . . . . . 85
9.5. Processing Bindings . . . . . . . . . . . . . . . . . . . 84 9.4.4. Sending Care-of Test Messages . . . . . . . . . . . . 85
9.5.1. Receiving Binding Updates . . . . . . . . . . . . . . 84 9.5. Processing Bindings . . . . . . . . . . . . . . . . . . . 85
9.5.2. Requests to Cache a Binding . . . . . . . . . . . . . 87 9.5.1. Receiving Binding Updates . . . . . . . . . . . . . . 85
9.5.3. Requests to Delete a Binding . . . . . . . . . . . . 87 9.5.2. Requests to Cache a Binding . . . . . . . . . . . . . 88
9.5.4. Sending Binding Acknowledgements . . . . . . . . . . 88 9.5.3. Requests to Delete a Binding . . . . . . . . . . . . 88
9.5.5. Sending Binding Refresh Requests . . . . . . . . . . 89 9.5.4. Sending Binding Acknowledgements . . . . . . . . . . 89
9.6. Cache Replacement Policy . . . . . . . . . . . . . . . . 89 9.5.5. Sending Binding Refresh Requests . . . . . . . . . . 90
10. Home Agent Operation . . . . . . . . . . . . . . . . . . . . 91 9.6. Cache Replacement Policy . . . . . . . . . . . . . . . . 90
10.1. Conceptual Data Structures . . . . . . . . . . . . . . . 91 10. Home Agent Operation . . . . . . . . . . . . . . . . . . . . 92
10.2. Processing Mobility Headers . . . . . . . . . . . . . . . 92 10.1. Conceptual Data Structures . . . . . . . . . . . . . . . 92
10.3. Processing Bindings . . . . . . . . . . . . . . . . . . . 92 10.2. Processing Mobility Headers . . . . . . . . . . . . . . . 93
10.3.1. Primary Care-of Address Registration . . . . . . . . 92 10.3. Processing Bindings . . . . . . . . . . . . . . . . . . . 93
10.3.2. Primary Care-of Address De-Registration . . . . . . . 96 10.3.1. Primary Care-of Address Registration . . . . . . . . 93
10.4. Packet Processing . . . . . . . . . . . . . . . . . . . . 97 10.3.2. Primary Care-of Address De-Registration . . . . . . . 97
10.4.1. Intercepting Packets for a Mobile Node . . . . . . . 97 10.4. Packet Processing . . . . . . . . . . . . . . . . . . . . 98
10.4.2. Processing Intercepted Packets . . . . . . . . . . . 99 10.4.1. Intercepting Packets for a Mobile Node . . . . . . . 98
10.4.3. Multicast Membership Control . . . . . . . . . . . . 100 10.4.2. Processing Intercepted Packets . . . . . . . . . . . 100
10.4.4. Stateful Address Autoconfiguration . . . . . . . . . 101 10.4.3. Multicast Membership Control . . . . . . . . . . . . 101
10.4.5. Handling Reverse Tunneled Packets . . . . . . . . . . 102 10.4.4. Stateful Address Autoconfiguration . . . . . . . . . 102
10.4.6. Protecting Return Routability Packets . . . . . . . . 102 10.4.5. Handling Reverse Tunneled Packets . . . . . . . . . . 103
10.5. Dynamic Home Agent Address Discovery . . . . . . . . . . 103 10.4.6. Protecting Return Routability Packets . . . . . . . . 103
10.5.1. Receiving Router Advertisement Messages . . . . . . . 103 10.5. Dynamic Home Agent Address Discovery . . . . . . . . . . 104
10.6. Sending Prefix Information to the Mobile Node . . . . . . 106 10.5.1. Receiving Router Advertisement Messages . . . . . . . 104
10.6.1. List of Home Network Prefixes . . . . . . . . . . . . 106 10.6. Sending Prefix Information to the Mobile Node . . . . . . 107
10.6.2. Scheduling Prefix Deliveries . . . . . . . . . . . . 106 10.6.1. List of Home Network Prefixes . . . . . . . . . . . . 107
10.6.3. Sending Advertisements . . . . . . . . . . . . . . . 108 10.6.2. Scheduling Prefix Deliveries . . . . . . . . . . . . 107
10.6.4. Lifetimes for Changed Prefixes . . . . . . . . . . . 109 10.6.3. Sending Advertisements . . . . . . . . . . . . . . . 109
11. Mobile Node Operation . . . . . . . . . . . . . . . . . . . . 110 10.6.4. Lifetimes for Changed Prefixes . . . . . . . . . . . 110
11.1. Conceptual Data Structures . . . . . . . . . . . . . . . 110 11. Mobile Node Operation . . . . . . . . . . . . . . . . . . . . 111
11.2. Processing Mobility Headers . . . . . . . . . . . . . . . 111 11.1. Conceptual Data Structures . . . . . . . . . . . . . . . 111
11.3. Packet Processing . . . . . . . . . . . . . . . . . . . . 112 11.2. Processing Mobility Headers . . . . . . . . . . . . . . . 112
11.3.1. Sending Packets While Away from Home . . . . . . . . 112 11.3. Packet Processing . . . . . . . . . . . . . . . . . . . . 113
11.3.2. Interaction with Outbound IPsec Processing . . . . . 115 11.3.1. Sending Packets While Away from Home . . . . . . . . 113
11.3.3. Receiving Packets While Away from Home . . . . . . . 117 11.3.2. Interaction with Outbound IPsec Processing . . . . . 116
11.3.4. Routing Multicast Packets . . . . . . . . . . . . . . 118 11.3.3. Receiving Packets While Away from Home . . . . . . . 118
11.3.5. Receiving ICMP Error Messages . . . . . . . . . . . . 120 11.3.4. Routing Multicast Packets . . . . . . . . . . . . . . 119
11.3.6. Receiving Binding Error Messages . . . . . . . . . . 120 11.3.5. Receiving ICMP Error Messages . . . . . . . . . . . . 121
11.4. Home Agent and Prefix Management . . . . . . . . . . . . 121 11.3.6. Receiving Binding Error Messages . . . . . . . . . . 121
11.4.1. Dynamic Home Agent Address Discovery . . . . . . . . 121 11.4. Home Agent and Prefix Management . . . . . . . . . . . . 122
11.4.2. Sending Mobile Prefix Solicitations . . . . . . . . . 122 11.4.1. Dynamic Home Agent Address Discovery . . . . . . . . 122
11.4.3. Receiving Mobile Prefix Advertisements . . . . . . . 123 11.4.2. Sending Mobile Prefix Solicitations . . . . . . . . . 123
11.5. Movement . . . . . . . . . . . . . . . . . . . . . . . . 124 11.4.3. Receiving Mobile Prefix Advertisements . . . . . . . 124
11.5.1. Movement Detection . . . . . . . . . . . . . . . . . 124 11.5. Movement . . . . . . . . . . . . . . . . . . . . . . . . 125
11.5.2. Home Link Detection . . . . . . . . . . . . . . . . . 127 11.5.1. Movement Detection . . . . . . . . . . . . . . . . . 125
11.5.3. Forming New Care-of Addresses . . . . . . . . . . . . 127 11.5.2. Home Link Detection . . . . . . . . . . . . . . . . . 128
11.5.4. Using Multiple Care-of Addresses . . . . . . . . . . 128 11.5.3. Forming New Care-of Addresses . . . . . . . . . . . . 128
11.5.5. Returning Home . . . . . . . . . . . . . . . . . . . 129 11.5.4. Using Multiple Care-of Addresses . . . . . . . . . . 129
11.6. Return Routability Procedure . . . . . . . . . . . . . . 131 11.5.5. Returning Home . . . . . . . . . . . . . . . . . . . 130
11.6.1. Sending Test Init Messages . . . . . . . . . . . . . 131 11.6. Return Routability Procedure . . . . . . . . . . . . . . 132
11.6.2. Receiving Test Messages . . . . . . . . . . . . . . . 132 11.6.1. Sending Test Init Messages . . . . . . . . . . . . . 132
11.6.3. Protecting Return Routability Packets . . . . . . . . 133 11.6.2. Receiving Test Messages . . . . . . . . . . . . . . . 133
11.7. Processing Bindings . . . . . . . . . . . . . . . . . . . 133 11.6.3. Protecting Return Routability Packets . . . . . . . . 134
11.7.1. Sending Binding Updates to the Home Agent . . . . . . 133 11.7. Processing Bindings . . . . . . . . . . . . . . . . . . . 134
11.7.2. Correspondent Registration . . . . . . . . . . . . . 136 11.7.1. Sending Binding Updates to the Home Agent . . . . . . 134
11.7.3. Receiving Binding Acknowledgements . . . . . . . . . 139 11.7.2. Correspondent Registration . . . . . . . . . . . . . 137
11.7.4. Receiving Binding Refresh Requests . . . . . . . . . 141 11.7.3. Receiving Binding Acknowledgements . . . . . . . . . 140
11.8. Retransmissions and Rate Limiting . . . . . . . . . . . . 142 11.7.4. Receiving Binding Refresh Requests . . . . . . . . . 142
12. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 144 11.8. Retransmissions and Rate Limiting . . . . . . . . . . . . 143
13. Protocol Configuration Variables . . . . . . . . . . . . . . 145 12. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 145
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 146 13. Protocol Configuration Variables . . . . . . . . . . . . . . 146
15. Security Considerations . . . . . . . . . . . . . . . . . . . 149 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 147
15.1. Threats . . . . . . . . . . . . . . . . . . . . . . . . . 149 15. Security Considerations . . . . . . . . . . . . . . . . . . . 150
15.2. Features . . . . . . . . . . . . . . . . . . . . . . . . 151 15.1. Threats . . . . . . . . . . . . . . . . . . . . . . . . . 150
15.3. Binding Updates to Home Agent . . . . . . . . . . . . . . 153 15.2. Features . . . . . . . . . . . . . . . . . . . . . . . . 152
15.4. Binding Updates to Correspondent Nodes . . . . . . . . . 155 15.3. Binding Updates to Home Agent . . . . . . . . . . . . . . 154
15.4.1. Overview . . . . . . . . . . . . . . . . . . . . . . 155 15.4. Binding Updates to Correspondent Nodes . . . . . . . . . 156
15.4.2. Achieved Security Properties . . . . . . . . . . . . 156 15.4.1. Overview . . . . . . . . . . . . . . . . . . . . . . 156
15.4.3. Comparison to Regular IPv6 Communications . . . . . . 157 15.4.2. Achieved Security Properties . . . . . . . . . . . . 157
15.4.4. Replay Attacks . . . . . . . . . . . . . . . . . . . 159 15.4.3. Comparison to Regular IPv6 Communications . . . . . . 158
15.4.5. Denial-of-Service Attacks . . . . . . . . . . . . . . 159 15.4.4. Replay Attacks . . . . . . . . . . . . . . . . . . . 160
15.4.6. Key Lengths . . . . . . . . . . . . . . . . . . . . . 160 15.4.5. Denial-of-Service Attacks . . . . . . . . . . . . . . 160
15.5. Dynamic Home Agent Address Discovery . . . . . . . . . . 161 15.4.6. Key Lengths . . . . . . . . . . . . . . . . . . . . . 161
15.6. Mobile Prefix Discovery . . . . . . . . . . . . . . . . . 162 15.5. Dynamic Home Agent Address Discovery . . . . . . . . . . 162
15.7. Tunneling via the Home Agent . . . . . . . . . . . . . . 162 15.6. Mobile Prefix Discovery . . . . . . . . . . . . . . . . . 163
15.8. Home Address Option . . . . . . . . . . . . . . . . . . . 163 15.7. Tunneling via the Home Agent . . . . . . . . . . . . . . 163
15.9. Type 2 Routing Header . . . . . . . . . . . . . . . . . . 163 15.8. Home Address Option . . . . . . . . . . . . . . . . . . . 164
16. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 165 15.9. Type 2 Routing Header . . . . . . . . . . . . . . . . . . 164
17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 166 16. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 166
18. References . . . . . . . . . . . . . . . . . . . . . . . . . 167 17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 167
18.1. Normative References . . . . . . . . . . . . . . . . . . 167 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 168
18.2. Informative References . . . . . . . . . . . . . . . . . 168 18.1. Normative References . . . . . . . . . . . . . . . . . . 168
Appendix A. Future Extensions . . . . . . . . . . . . . . . . . 171 18.2. Informative References . . . . . . . . . . . . . . . . . 169
A.1. Piggybacking . . . . . . . . . . . . . . . . . . . . . . 171 Appendix A. Future Extensions . . . . . . . . . . . . . . . . . 172
A.2. Triangular Routing . . . . . . . . . . . . . . . . . . . 171 A.1. Piggybacking . . . . . . . . . . . . . . . . . . . . . . 172
A.3. New Authorization Methods . . . . . . . . . . . . . . . . 171 A.2. Triangular Routing . . . . . . . . . . . . . . . . . . . 172
A.4. Neighbor Discovery Extensions . . . . . . . . . . . . . . 171 A.3. New Authorization Methods . . . . . . . . . . . . . . . . 172
Appendix B. Changes since RFC 3775 . . . . . . . . . . . . . . . 173 A.4. Neighbor Discovery Extensions . . . . . . . . . . . . . . 172
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 176 Appendix B. Changes since RFC 3775 . . . . . . . . . . . . . . . 174
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 177
1. Introduction 1. Introduction
This document specifies a protocol which allows nodes to remain This document specifies a protocol which allows nodes to remain
reachable while moving around in the IPv6 Internet. Without specific reachable while moving around in the IPv6 Internet. Without specific
support for mobility in IPv6 [5], packets destined to a mobile node support for mobility in IPv6 [5], packets destined to a mobile node
would not be able to reach it while the mobile node is away from its would not be able to reach it while the mobile node is away from its
home link. In order to continue communication in spite of its home link. In order to continue communication in spite of its
movement, a mobile node could change its IP address each time it movement, a mobile node could change its IP address each time it
moves to a new link, but the mobile node would then not be able to moves to a new link, but the mobile node would then not be able to
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This document obsoletes RFC 3775. Issues with the original document This document obsoletes RFC 3775. Issues with the original document
have been observed during integration, testing and deployment of RFC have been observed during integration, testing and deployment of RFC
3775. A more detailed list of the changes since RFC 3775 may be 3775. A more detailed list of the changes since RFC 3775 may be
found in Appendix B. found in Appendix B.
2. Comparison with Mobile IP for IPv4 2. Comparison with Mobile IP for IPv4
The design of Mobile IP support in IPv6 (Mobile IPv6) benefits both The design of Mobile IP support in IPv6 (Mobile IPv6) benefits both
from the experiences gained from the development of Mobile IP support from the experiences gained from the development of Mobile IP support
in IPv4 (Mobile IPv4) [31] [24] [25], and from the opportunities in IPv4 (Mobile IPv4) [30] [23] [24], and from the opportunities
provided by IPv6. Mobile IPv6 thus shares many features with Mobile provided by IPv6. Mobile IPv6 thus shares many features with Mobile
IPv4, but is integrated into IPv6 and offers many other improvements. IPv4, but is integrated into IPv6 and offers many other improvements.
This section summarizes the major differences between Mobile IPv4 and This section summarizes the major differences between Mobile IPv4 and
Mobile IPv6: Mobile IPv6:
o There is no need to deploy special routers as "foreign agents", as o There is no need to deploy special routers as "foreign agents", as
in Mobile IPv4. Mobile IPv6 operates in any location without any in Mobile IPv4. Mobile IPv6 operates in any location without any
special support required from the local router. special support required from the local router.
o Support for route optimization is a fundamental part of the o Support for route optimization is a fundamental part of the
protocol, rather than a nonstandard set of extensions. protocol, rather than a nonstandard set of extensions.
o Mobile IPv6 route optimization can operate securely even without o Mobile IPv6 route optimization can operate securely even without
pre-arranged security associations. It is expected that route pre-arranged security associations. It is expected that route
optimization can be deployed on a global scale between all mobile optimization can be deployed on a global scale between all mobile
nodes and correspondent nodes. nodes and correspondent nodes.
o Support is also integrated into Mobile IPv6 for allowing route o Support is also integrated into Mobile IPv6 for allowing route
optimization to coexist efficiently with routers that perform optimization to coexist efficiently with routers that perform
"ingress filtering" [28]. "ingress filtering" [26].
o The IPv6 Neighbor Unreachability Detection assures symmetric o The IPv6 Neighbor Unreachability Detection assures symmetric
reachability between the mobile node and its default router in the reachability between the mobile node and its default router in the
current location. current location.
o Most packets sent to a mobile node while away from home in Mobile o Most packets sent to a mobile node while away from home in Mobile
IPv6 are sent using an IPv6 routing header rather than IP IPv6 are sent using an IPv6 routing header rather than IP
encapsulation, reducing the amount of resulting overhead compared encapsulation, reducing the amount of resulting overhead compared
to Mobile IPv4. to Mobile IPv4.
o Mobile IPv6 is decoupled from any particular link layer, as it o Mobile IPv6 is decoupled from any particular link layer, as it
uses IPv6 Neighbor Discovery [18] instead of ARP. This also uses IPv6 Neighbor Discovery [17] instead of ARP. This also
improves the robustness of the protocol. improves the robustness of the protocol.
o The use of IPv6 encapsulation (and the routing header) removes the o The use of IPv6 encapsulation (and the routing header) removes the
need in Mobile IPv6 to manage "tunnel soft state". need in Mobile IPv6 to manage "tunnel soft state".
o The dynamic home agent address discovery mechanism in Mobile IPv6 o The dynamic home agent address discovery mechanism in Mobile IPv6
returns a single reply to the mobile node. The directed broadcast returns a single reply to the mobile node. The directed broadcast
approach used in IPv4 returns separate replies from each home approach used in IPv4 returns separate replies from each home
agent. agent.
3. Terminology 3. Terminology
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [1]. document are to be interpreted as described in RFC 2119 [1].
3.1. General Terms 3.1. General Terms
IP IP
Internet Protocol Version 6 (IPv6). Internet Protocol Version 6 (IPv6).
node node
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First (size, input) First (size, input)
Some formulas in this specification use a functional form "First Some formulas in this specification use a functional form "First
(size, input)" to indicate truncation of the "input" data so that (size, input)" to indicate truncation of the "input" data so that
only the first "size" bits remain to be used. only the first "size" bits remain to be used.
3.2. Mobile IPv6 Terms 3.2. Mobile IPv6 Terms
These terms are intended to be compatible with the definitions given These terms are intended to be compatible with the definitions given
in RFC 3753[38]. However, if there is any conflict, the definitions in RFC 3753[37]. However, if there is any conflict, the definitions
given here should be considered to supersede those in RFC 3753. given here should be considered to supersede those in RFC 3753.
home address home address
A unicast routable address assigned to a mobile node, used as the A unicast routable address assigned to a mobile node, used as the
permanent address of the mobile node. This address is within the permanent address of the mobile node. This address is within the
mobile node's home link. Standard IP routing mechanisms will mobile node's home link. Standard IP routing mechanisms will
deliver packets destined for a mobile node's home address to its deliver packets destined for a mobile node's home address to its
home link. Mobile nodes can have multiple home addresses, for home link. Mobile nodes can have multiple home addresses, for
instance when there are multiple home prefixes on the home link. instance when there are multiple home prefixes on the home link.
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are described starting from Section 6.5. are described starting from Section 6.5.
This document is written under the assumption that the mobile node is This document is written under the assumption that the mobile node is
configured with the home prefix for the mobile node to be able to configured with the home prefix for the mobile node to be able to
discover a home agent and configure a home address. This might be discover a home agent and configure a home address. This might be
limiting in deployments where the home agent and the home address for limiting in deployments where the home agent and the home address for
the mobile node needs to be assigned dynamically. Additional the mobile node needs to be assigned dynamically. Additional
mechanisms have been specified for the mobile node to dynamically mechanisms have been specified for the mobile node to dynamically
configure a home agent, a home address and the home prefix. These configure a home agent, a home address and the home prefix. These
mechanisms are described in "Mobile IPv6 Bootstrapping in Split mechanisms are described in "Mobile IPv6 Bootstrapping in Split
Scenario" [22] and "MIP6 bootstrapping for the Integrated Scenario" Scenario" [21] and "MIP6 bootstrapping for the Integrated Scenario"
[35]. [34].
4.2. New IPv6 Protocol 4.2. New IPv6 Protocol
Mobile IPv6 defines a new IPv6 protocol, using the Mobility Header Mobile IPv6 defines a new IPv6 protocol, using the Mobility Header
(see Section 6.1). This Header is used to carry the following (see Section 6.1). This Header is used to carry the following
messages: messages:
Home Test Init Home Test Init
Home Test Home Test
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agent. In order to make this possible, it is necessary that the home agent. In order to make this possible, it is necessary that the home
address of the mobile node is visible in the Binding Updates and address of the mobile node is visible in the Binding Updates and
Acknowledgements. The home address is used in these packets as a Acknowledgements. The home address is used in these packets as a
source or destination, or in the Home Address destination option or source or destination, or in the Home Address destination option or
the type 2 routing header. the type 2 routing header.
As with all IPsec security associations in this specification, manual As with all IPsec security associations in this specification, manual
configuration of security associations MUST be supported. The shared configuration of security associations MUST be supported. The shared
secrets used MUST be random and unique for different mobile nodes, secrets used MUST be random and unique for different mobile nodes,
and MUST be distributed off-line to the mobile nodes. Automatic key and MUST be distributed off-line to the mobile nodes. Automatic key
management with IKEv2 [44] MAY be supported as described in [20]. management with IKEv2 [43] MAY be supported as described in [19].
Section 11.3.2 discusses how IKEv2 connections to the home agent need Section 11.3.2 discusses how IKEv2 connections to the home agent need
a careful treatment of the addresses used for transporting IKEv2. a careful treatment of the addresses used for transporting IKEv2.
This is necessary to ensure that a Binding Update is not needed This is necessary to ensure that a Binding Update is not needed
before the IKEv2 exchange which is needed for securing the Binding before the IKEv2 exchange which is needed for securing the Binding
Update. Update.
More detailed descriptions and examples using IPsec to protect More detailed descriptions and examples using IPsec to protect
communications between the mobile node and the home agent have been communications between the mobile node and the home agent have been
published [20]. published [11][19].
5.2. Binding Updates to Correspondent Nodes 5.2. Binding Updates to Correspondent Nodes
The protection of Binding Updates sent to correspondent nodes does The protection of Binding Updates sent to correspondent nodes does
not require the configuration of security associations or the not require the configuration of security associations or the
existence of an authentication infrastructure between the mobile existence of an authentication infrastructure between the mobile
nodes and correspondent nodes. Instead, a method called the return nodes and correspondent nodes. Instead, a method called the return
routability procedure is used to assure that the right mobile node is routability procedure is used to assure that the right mobile node is
sending the message. This method does not protect against attackers sending the message. This method does not protect against attackers
who are on the path between the home network and the correspondent who are on the path between the home network and the correspondent
node. However, attackers in such a location are capable of node. However, attackers in such a location are capable of
performing the same attacks even without Mobile IPv6. The main performing the same attacks even without Mobile IPv6. The main
advantage of the return routability procedure is that it limits the advantage of the return routability procedure is that it limits the
potential attackers to those having an access to one specific path in potential attackers to those having an access to one specific path in
the Internet, and avoids forged Binding Updates from anywhere else in the Internet, and avoids forged Binding Updates from anywhere else in
the Internet. For a more in depth explanation of the security the Internet. For a more in depth explanation of the security
properties of the return routability procedure, see Section 15. properties of the return routability procedure, see Section 15.
Also, consult [41] Also, consult [40]
The integrity and authenticity of the Binding Update messages to The integrity and authenticity of the Binding Update messages to
correspondent nodes is protected by using a keyed-hash algorithm. correspondent nodes is protected by using a keyed-hash algorithm.
The binding management key, Kbm, is used to key the hash algorithm The binding management key, Kbm, is used to key the hash algorithm
for this purpose. Kbm is established using data exchanged during the for this purpose. Kbm is established using data exchanged during the
return routability procedure. The data exchange is accomplished by return routability procedure. The data exchange is accomplished by
use of node keys, nonces, cookies, tokens, and certain cryptographic use of node keys, nonces, cookies, tokens, and certain cryptographic
functions. Section 5.2.5 outlines the basic return routability functions. Section 5.2.5 outlines the basic return routability
procedure. Section 5.2.6 shows how the results of this procedure are procedure. Section 5.2.6 shows how the results of this procedure are
used to authorize a Binding Update to a correspondent node. used to authorize a Binding Update to a correspondent node.
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Home and care-of keygen tokens are produced by the correspondent node Home and care-of keygen tokens are produced by the correspondent node
based on its currently active secret key (Kcn) and nonces, as well as based on its currently active secret key (Kcn) and nonces, as well as
the home or care-of address (respectively). A keygen token is valid the home or care-of address (respectively). A keygen token is valid
as long as both the secret key (Kcn) and the nonce used to create it as long as both the secret key (Kcn) and the nonce used to create it
are valid. are valid.
5.2.4. Cryptographic Functions 5.2.4. Cryptographic Functions
By default in this specification, the function used to compute hash By default in this specification, the function used to compute hash
values is SHA1 [16]. Message Authentication Codes (MACs) are then values is SHA1 [10]. Message Authentication Codes (MACs) are then
computed using HMAC_SHA1 [26] [16]. HMAC_SHA1(K,m) denotes such a computed using HMAC_SHA1 [25][10]. HMAC_SHA1(K,m) denotes such a MAC
MAC computed on message m with key K. computed on message m with key K.
5.2.5. Return Routability Procedure 5.2.5. Return Routability Procedure
The Return Routability Procedure enables the correspondent node to The Return Routability Procedure enables the correspondent node to
obtain some reasonable assurance that the mobile node is in fact obtain some reasonable assurance that the mobile node is in fact
addressable at its claimed care-of address as well as at its home addressable at its claimed care-of address as well as at its home
address. Only with this assurance is the correspondent node able to address. Only with this assurance is the correspondent node able to
accept Binding Updates from the mobile node which would then instruct accept Binding Updates from the mobile node which would then instruct
the correspondent node to direct that mobile node's data traffic to the correspondent node to direct that mobile node's data traffic to
its claimed care-of address. its claimed care-of address.
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the following we define the security measures taken to protect these, the following we define the security measures taken to protect these,
and to prevent their use in attacks against other parties. and to prevent their use in attacks against other parties.
This specification limits the use of the Home Address destination This specification limits the use of the Home Address destination
option to the situation where the correspondent node already has a option to the situation where the correspondent node already has a
Binding Cache entry for the given home address. This avoids the use Binding Cache entry for the given home address. This avoids the use
of the Home Address option in attacks described in Section 15.1. of the Home Address option in attacks described in Section 15.1.
Mobile IPv6 uses a type of routing header specific to Mobile IPv6. Mobile IPv6 uses a type of routing header specific to Mobile IPv6.
This type provides the necessary functionality but does not open This type provides the necessary functionality but does not open
vulnerabilities discussed in Section 15.1 and RFC 5095 [43]. vulnerabilities discussed in Section 15.1 and RFC 5095 [42].
Tunnels between the mobile node and the home agent are protected by Tunnels between the mobile node and the home agent are protected by
ensuring proper use of source addresses, and optional cryptographic ensuring proper use of source addresses, and optional cryptographic
protection. The mobile node verifies that the outer IP address protection. The mobile node verifies that the outer IP address
corresponds to its home agent. The home agent verifies that the corresponds to its home agent. The home agent verifies that the
outer IP address corresponds to the current location of the mobile outer IP address corresponds to the current location of the mobile
node (Binding Updates sent to the home agents are secure). The home node (Binding Updates sent to the home agents are secure). The home
agent identifies the mobile node through the source address of the agent identifies the mobile node through the source address of the
inner packet. (Typically, this is the home address of the mobile inner packet. (Typically, this is the home address of the mobile
node, but it can also be a link-local address, as discussed in node, but it can also be a link-local address, as discussed in
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137 Expired care-of nonce index 137 Expired care-of nonce index
138 Expired nonces 138 Expired nonces
139 Registration type change disallowed 139 Registration type change disallowed
TBD Invalid Care-of Address TBD Invalid Care-of Address
Up-to-date values of the Status field are to be specified in the Up-to-date values of the Status field are to be specified in the
IANA registry of assigned numbers [10]. IANA registry of assigned numbers [28].
Key Management Mobility Capability (K) Key Management Mobility Capability (K)
If this bit is cleared, the protocol used by the home agent for If this bit is cleared, the protocol used by the home agent for
establishing the IPsec security associations between the mobile establishing the IPsec security associations between the mobile
node and the home agent does not survive movements. It may then node and the home agent does not survive movements. It may then
have to be rerun. (Note that the IPsec security associations have to be rerun. (Note that the IPsec security associations
themselves are expected to survive movements.) themselves are expected to survive movements.)
Correspondent nodes MUST set the K bit to 0. Correspondent nodes MUST set the K bit to 0.
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routing headers. routing headers.
6.5. ICMP Home Agent Address Discovery Request Message 6.5. ICMP Home Agent Address Discovery Request Message
The ICMP Home Agent Address Discovery Request message is used by a The ICMP Home Agent Address Discovery Request message is used by a
mobile node to initiate the dynamic home agent address discovery mobile node to initiate the dynamic home agent address discovery
mechanism, as described in Section 11.4.1. The mobile node sends the mechanism, as described in Section 11.4.1. The mobile node sends the
Home Agent Address Discovery Request message to the Mobile IPv6 Home- Home Agent Address Discovery Request message to the Mobile IPv6 Home-
Agents anycast address [7] for its own home subnet prefix. (Note Agents anycast address [7] for its own home subnet prefix. (Note
that the currently defined anycast addresses may not work with all that the currently defined anycast addresses may not work with all
prefix lengths other than those defined in RFC 4291 [15] [36].) prefix lengths other than those defined in RFC 4291 [15] [35].)
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum | | Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier | Reserved | | Identifier | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type Type
144 144
Code Code
0 0
Checksum Checksum
The ICMP checksum [17]. The ICMP checksum [16].
Identifier Identifier
An identifier to aid in matching Home Agent Address Discovery An identifier to aid in matching Home Agent Address Discovery
Reply messages to this Home Agent Address Discovery Request Reply messages to this Home Agent Address Discovery Request
message. message.
Reserved Reserved
This field is unused. It MUST be initialized to zero by the This field is unused. It MUST be initialized to zero by the
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Type Type
145 145
Code Code
0 0
Checksum Checksum
The ICMP checksum [17]. The ICMP checksum [16].
Identifier Identifier
The identifier from the invoking Home Agent Address Discovery The identifier from the invoking Home Agent Address Discovery
Request message. Request message.
Reserved Reserved
This field is unused. It MUST be initialized to zero by the This field is unused. It MUST be initialized to zero by the
sender and MUST be ignored by the receiver. sender and MUST be ignored by the receiver.
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Type Type
146 146
Code Code
0 0
Checksum Checksum
The ICMP checksum [17]. The ICMP checksum [16].
Identifier Identifier
An identifier to aid in matching a future Mobile Prefix An identifier to aid in matching a future Mobile Prefix
Advertisement to this Mobile Prefix Solicitation. Advertisement to this Mobile Prefix Solicitation.
Reserved Reserved
This field is unused. It MUST be initialized to zero by the This field is unused. It MUST be initialized to zero by the
sender and MUST be ignored by the receiver. sender and MUST be ignored by the receiver.
The Mobile Prefix Solicitation messages may have options. These The Mobile Prefix Solicitation messages may have options. These
options MUST use the option format defined in Neighbor Discovery (RFC options MUST use the option format defined in Neighbor Discovery (RFC
4861 [18]). This document does not define any option types for the 4861 [17]). This document does not define any option types for the
Mobile Prefix Solicitation message, but future documents may define Mobile Prefix Solicitation message, but future documents may define
new options. Home agents MUST silently ignore any options they do new options. Home agents MUST silently ignore any options they do
not recognize and continue processing the message. not recognize and continue processing the message.
6.8. ICMP Mobile Prefix Advertisement Message Format 6.8. ICMP Mobile Prefix Advertisement Message Format
A home agent will send a Mobile Prefix Advertisement to a mobile node A home agent will send a Mobile Prefix Advertisement to a mobile node
to distribute prefix information about the home link while the mobile to distribute prefix information about the home link while the mobile
node is traveling away from the home network. This will occur in node is traveling away from the home network. This will occur in
response to a Mobile Prefix Solicitation with an Advertisement, or by response to a Mobile Prefix Solicitation with an Advertisement, or by
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Type Type
147 147
Code Code
0 0
Checksum Checksum
The ICMP checksum [17]. The ICMP checksum [16].
Identifier Identifier
An identifier to aid in matching this Mobile Prefix Advertisement An identifier to aid in matching this Mobile Prefix Advertisement
to a previous Mobile Prefix Solicitation. to a previous Mobile Prefix Solicitation.
M M
1-bit Managed Address Configuration flag. When set, hosts use the 1-bit Managed Address Configuration flag. When set, hosts use the
administered (stateful) protocol for address autoconfiguration in administered (stateful) protocol for address autoconfiguration in
addition to any addresses autoconfigured using stateless address addition to any addresses autoconfigured using stateless address
autoconfiguration. The use of this flag is described in [18] autoconfiguration. The use of this flag is described in [17]
[19]. [18].
O O
1-bit Other Stateful Configuration flag. When set, hosts use the 1-bit Other Stateful Configuration flag. When set, hosts use the
administered (stateful) protocol for autoconfiguration of other administered (stateful) protocol for autoconfiguration of other
(non-address) information. The use of this flag is described in (non-address) information. The use of this flag is described in
[18] [19]. [17] [18].
Reserved Reserved
This field is unused. It MUST be initialized to zero by the This field is unused. It MUST be initialized to zero by the
sender and MUST be ignored by the receiver. sender and MUST be ignored by the receiver.
The Mobile Prefix Advertisement messages may have options. These The Mobile Prefix Advertisement messages may have options. These
options MUST use the option format defined in Neighbor Discovery (RFC options MUST use the option format defined in Neighbor Discovery (RFC
4861 [18]). This document defines one option which may be carried in 4861 [17]). This document defines one option which may be carried in
a Mobile Prefix Advertisement message, but future documents may a Mobile Prefix Advertisement message, but future documents may
define new options. Mobile nodes MUST silently ignore any options define new options. Mobile nodes MUST silently ignore any options
they do not recognize and continue processing the message. they do not recognize and continue processing the message.
Prefix Information Prefix Information
Each message contains one or more Prefix Information options. Each message contains one or more Prefix Information options.
Each option carries the prefix(es) that the mobile node should use Each option carries the prefix(es) that the mobile node should use
to configure its home address(es). Section 10.6 describes which to configure its home address(es). Section 10.6 describes which
prefixes should be advertised to the mobile node. prefixes should be advertised to the mobile node.
The Prefix Information option is defined in Section 4.6.2 of The Prefix Information option is defined in Section 4.6.2 of
Neighbor Discovery (RFC 4861 [18]), with modifications defined in Neighbor Discovery (RFC 4861 [17]), with modifications defined in
Section 7.2 of this specification. The home agent MUST use this Section 7.2 of this specification. The home agent MUST use this
modified Prefix Information option to send home network prefixes modified Prefix Information option to send home network prefixes
as defined in Section 10.6.1. as defined in Section 10.6.1.
If the Advertisement is sent in response to a Mobile Prefix If the Advertisement is sent in response to a Mobile Prefix
Solicitation, the home agent MUST copy the Identifier value from that Solicitation, the home agent MUST copy the Identifier value from that
message into the Identifier field of the Advertisement. message into the Identifier field of the Advertisement.
The home agent MUST NOT send more than one Mobile Prefix The home agent MUST NOT send more than one Mobile Prefix
Advertisement message per second to any mobile node. Advertisement message per second to any mobile node.
The M and O bits MUST be cleared if the Home Agent DHCPv6 support is The M and O bits MUST be cleared if the Home Agent DHCPv6 support is
not provided. If such support is provided then they are set in not provided. If such support is provided then they are set in
concert with the home network's administrative settings. concert with the home network's administrative settings.
7. Modifications to IPv6 Neighbor Discovery 7. Modifications to IPv6 Neighbor Discovery
7.1. Modified Router Advertisement Message Format 7.1. Modified Router Advertisement Message Format
Mobile IPv6 modifies the format of the Router Advertisement message Mobile IPv6 modifies the format of the Router Advertisement message
[18] by the addition of a single flag bit to indicate that the router [17] by the addition of a single flag bit to indicate that the router
sending the Advertisement message is serving as a home agent on this sending the Advertisement message is serving as a home agent on this
link. The format of the Router Advertisement message is as follows: link. The format of the Router Advertisement message is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum | | Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |M|O|H| Reserved| Router Lifetime | | Cur Hop Limit |M|O|H| Reserved| Router Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time | | Reachable Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer | | Retrans Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ... | Options ...
+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-+-
This format represents the following changes over that originally This format represents the following changes over that originally
specified for Neighbor Discovery [18]: specified for Neighbor Discovery [17]:
Home Agent (H) Home Agent (H)
The Home Agent (H) bit is set in a Router Advertisement to The Home Agent (H) bit is set in a Router Advertisement to
indicate that the router sending this Router Advertisement is also indicate that the router sending this Router Advertisement is also
functioning as a Mobile IPv6 home agent on this link. functioning as a Mobile IPv6 home agent on this link.
Reserved Reserved
Reduced from a 6-bit field to a 5-bit field to account for the Reduced from a 6-bit field to a 5-bit field to account for the
addition of the above bit. addition of the above bit.
7.2. Modified Prefix Information Option Format 7.2. Modified Prefix Information Option Format
Mobile IPv6 requires knowledge of a router's global address in Mobile IPv6 requires knowledge of a router's global address in
building a Home Agents List as part of the dynamic home agent address building a Home Agents List as part of the dynamic home agent address
discovery mechanism. discovery mechanism.
However, Neighbor Discovery [18] only advertises a router's link- However, Neighbor Discovery [17] only advertises a router's link-
local address, by requiring this address to be used as the IP Source local address, by requiring this address to be used as the IP Source
Address of each Router Advertisement. Address of each Router Advertisement.
Mobile IPv6 extends Neighbor Discovery to allow a router to advertise Mobile IPv6 extends Neighbor Discovery to allow a router to advertise
its global address, by the addition of a single flag bit in the its global address, by the addition of a single flag bit in the
format of a Prefix Information option for use in Router Advertisement format of a Prefix Information option for use in Router Advertisement
messages. The format of the Prefix Information option is as follows: messages. The format of the Prefix Information option is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
skipping to change at page 66, line 29 skipping to change at page 67, line 29
| | | |
+ + + +
| | | |
+ Prefix + + Prefix +
| | | |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This format represents the following changes over that originally This format represents the following changes over that originally
specified for Neighbor Discovery [18]: specified for Neighbor Discovery [17]:
Router Address (R) Router Address (R)
1-bit router address flag. When set, indicates that the Prefix 1-bit router address flag. When set, indicates that the Prefix
field contains a complete IP address assigned to the sending field contains a complete IP address assigned to the sending
router. The indicated prefix is given by the first Prefix Length router. The indicated prefix is given by the first Prefix Length
bits of the Prefix field. The router IP address has the same bits of the Prefix field. The router IP address has the same
scope and conforms to the same lifetime values as the advertised scope and conforms to the same lifetime values as the advertised
prefix. This use of the Prefix field is compatible with its use prefix. This use of the Prefix field is compatible with its use
in advertising the prefix itself, since Prefix Advertisement uses in advertising the prefix itself, since Prefix Advertisement uses
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independent of the processing required for the On-Link (L) and independent of the processing required for the On-Link (L) and
Autonomous Address-Configuration (A) flag bits. Autonomous Address-Configuration (A) flag bits.
Reserved1 Reserved1
Reduced from a 6-bit field to a 5-bit field to account for the Reduced from a 6-bit field to a 5-bit field to account for the
addition of the above bit. addition of the above bit.
In a Router Advertisement, a home agent MUST, and all other routers In a Router Advertisement, a home agent MUST, and all other routers
MAY, include at least one Prefix Information option with the Router MAY, include at least one Prefix Information option with the Router
Address (R) bit set. Neighbor Discovery (RFC 4861 [18]) specifies Address (R) bit set. Neighbor Discovery (RFC 4861 [17]) specifies
that, when including all options in a Router Advertisement causes the that, when including all options in a Router Advertisement causes the
size of the Advertisement to exceed the link MTU, multiple size of the Advertisement to exceed the link MTU, multiple
Advertisements can be sent, each containing a subset of the Neighbor Advertisements can be sent, each containing a subset of the Neighbor
Discovery options. Also, when sending unsolicited multicast Router Discovery options. Also, when sending unsolicited multicast Router
Advertisements more frequently than the limit specified in RFC 4861, Advertisements more frequently than the limit specified in RFC 4861,
the sending router need not include all options in each of these the sending router need not include all options in each of these
Advertisements. However, in both of these cases the router SHOULD Advertisements. However, in both of these cases the router SHOULD
include at least one Prefix Information option with the Router include at least one Prefix Information option with the Router
Address (R) bit set in each such advertisement, if this bit is set in Address (R) bit set in each such advertisement, if this bit is set in
some advertisement sent by the router. some advertisement sent by the router.
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Reserved Reserved
This field is unused. It MUST be initialized to zero by the This field is unused. It MUST be initialized to zero by the
sender and MUST be ignored by the receiver. sender and MUST be ignored by the receiver.
Advertisement Interval Advertisement Interval
32-bit unsigned integer. The maximum time, in milliseconds, 32-bit unsigned integer. The maximum time, in milliseconds,
between successive unsolicited Router Advertisement messages sent between successive unsolicited Router Advertisement messages sent
by this router on this network interface. Using the conceptual by this router on this network interface. Using the conceptual
router configuration variables defined by Neighbor Discovery [18], router configuration variables defined by Neighbor Discovery [17],
this field MUST be equal to the value MaxRtrAdvInterval, expressed this field MUST be equal to the value MaxRtrAdvInterval, expressed
in milliseconds. in milliseconds.
Routers MAY include this option in their Router Advertisements. A Routers MAY include this option in their Router Advertisements. A
mobile node receiving a Router Advertisement containing this option mobile node receiving a Router Advertisement containing this option
SHOULD utilize the specified Advertisement Interval for that router SHOULD utilize the specified Advertisement Interval for that router
in its movement detection algorithm, as described in Section 11.5.1. in its movement detection algorithm, as described in Section 11.5.1.
This option MUST be silently ignored for other Neighbor Discovery This option MUST be silently ignored for other Neighbor Discovery
messages. messages.
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This option MUST be silently ignored for other Neighbor Discovery This option MUST be silently ignored for other Neighbor Discovery
messages. messages.
If both the Home Agent Preference and Home Agent Lifetime are set to If both the Home Agent Preference and Home Agent Lifetime are set to
their default values specified above, this option SHOULD NOT be their default values specified above, this option SHOULD NOT be
included in the Router Advertisement messages sent by this home included in the Router Advertisement messages sent by this home
agent. agent.
7.5. Changes to Sending Router Advertisements 7.5. Changes to Sending Router Advertisements
The Neighbor Discovery protocol specification [18] limits routers to The Neighbor Discovery protocol specification [17] limits routers to
a minimum interval of 3 seconds between sending unsolicited multicast a minimum interval of 3 seconds between sending unsolicited multicast
Router Advertisement messages from any given network interface Router Advertisement messages from any given network interface
(limited by MinRtrAdvInterval and MaxRtrAdvInterval), stating that: (limited by MinRtrAdvInterval and MaxRtrAdvInterval), stating that:
"Routers generate Router Advertisements frequently enough that "Routers generate Router Advertisements frequently enough that
hosts will learn of their presence within a few minutes, but not hosts will learn of their presence within a few minutes, but not
frequently enough to rely on an absence of advertisements to frequently enough to rely on an absence of advertisements to
detect router failure; a separate Neighbor Unreachability detect router failure; a separate Neighbor Unreachability
Detection algorithm provides failure detection." Detection algorithm provides failure detection."
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o MinRtrAdvInterval 0.03 seconds o MinRtrAdvInterval 0.03 seconds
o MaxRtrAdvInterval 0.07 seconds o MaxRtrAdvInterval 0.07 seconds
In the case where the minimum intervals and delays are used, the mean In the case where the minimum intervals and delays are used, the mean
time between unsolicited multicast router advertisements is 50ms. time between unsolicited multicast router advertisements is 50ms.
Use of these modified limits MUST be configurable (see also the Use of these modified limits MUST be configurable (see also the
configuration variable MinDelayBetweenRas in Section 13 which may configuration variable MinDelayBetweenRas in Section 13 which may
also have to be modified accordingly). Systems where these values also have to be modified accordingly). Systems where these values
are available MUST NOT default to them, and SHOULD default to values are available MUST NOT default to them, and SHOULD default to values
specified in Neighbor Discovery (RFC 4861 [18]). Knowledge of the specified in Neighbor Discovery (RFC 4861 [17]). Knowledge of the
type of network interface and operating environment SHOULD be taken type of network interface and operating environment SHOULD be taken
into account in configuring these limits for each network interface. into account in configuring these limits for each network interface.
This is important with some wireless links, where increasing the This is important with some wireless links, where increasing the
frequency of multicast beacons can cause considerable overhead. frequency of multicast beacons can cause considerable overhead.
Routers SHOULD adhere to the intervals specified in RFC 4861 [18], if Routers SHOULD adhere to the intervals specified in RFC 4861 [17], if
this overhead is likely to cause service degradation. this overhead is likely to cause service degradation.
Additionally, the possible low values of MaxRtrAdvInterval may cause Additionally, the possible low values of MaxRtrAdvInterval may cause
some problems with movement detection in some mobile nodes. To some problems with movement detection in some mobile nodes. To
ensure that this is not a problem, Routers SHOULD add 20ms to any ensure that this is not a problem, Routers SHOULD add 20ms to any
Advertisement Intervals sent in RAs, which are below 200 ms, in order Advertisement Intervals sent in RAs, which are below 200 ms, in order
to account for scheduling granularities on both the MN and the to account for scheduling granularities on both the MN and the
Router. Router.
Note that multicast Router Advertisements are not always required in Note that multicast Router Advertisements are not always required in
skipping to change at page 71, line 40 skipping to change at page 72, line 40
layers. Router advertisements in such networks SHOULD be sent only layers. Router advertisements in such networks SHOULD be sent only
when solicited. In such networks it SHOULD be possible to disable when solicited. In such networks it SHOULD be possible to disable
unsolicited multicast Router Advertisements on specific interfaces. unsolicited multicast Router Advertisements on specific interfaces.
The MinRtrAdvInterval and MaxRtrAdvInterval in such a case can be set The MinRtrAdvInterval and MaxRtrAdvInterval in such a case can be set
to some high values. to some high values.
Home agents MUST include the Source Link-Layer Address option in all Home agents MUST include the Source Link-Layer Address option in all
Router Advertisements they send. This simplifies the process of Router Advertisements they send. This simplifies the process of
returning home, as discussed in Section 11.5.5. returning home, as discussed in Section 11.5.5.
Note that according to Neighbor Discovery (RFC 4861 [18]), Note that according to Neighbor Discovery (RFC 4861 [17]),
AdvDefaultLifetime is by default based on the value of AdvDefaultLifetime is by default based on the value of
MaxRtrAdvInterval. AdvDefaultLifetime is used in the Router Lifetime MaxRtrAdvInterval. AdvDefaultLifetime is used in the Router Lifetime
field of Router Advertisements. Given that this field is expressed field of Router Advertisements. Given that this field is expressed
in seconds, a small MaxRtrAdvInterval value can result in a zero in seconds, a small MaxRtrAdvInterval value can result in a zero
value for this field. To prevent this, routers SHOULD keep value for this field. To prevent this, routers SHOULD keep
AdvDefaultLifetime in at least one second, even if the use of AdvDefaultLifetime in at least one second, even if the use of
MaxRtrAdvInterval would result in a smaller value. MaxRtrAdvInterval would result in a smaller value.
8. Requirements for Types of IPv6 Nodes 8. Requirements for Types of IPv6 Nodes
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o The node SHOULD allow route optimization to be administratively o The node SHOULD allow route optimization to be administratively
enabled or disabled. The default SHOULD be enabled. enabled or disabled. The default SHOULD be enabled.
8.3. All IPv6 Routers 8.3. All IPv6 Routers
All IPv6 routers, even those not serving as a home agent for Mobile All IPv6 routers, even those not serving as a home agent for Mobile
IPv6, have an effect on how well mobile nodes can communicate: IPv6, have an effect on how well mobile nodes can communicate:
o Every IPv6 router SHOULD be able to send an Advertisement Interval o Every IPv6 router SHOULD be able to send an Advertisement Interval
option (Section 7.3) in each of its Router Advertisements [18], to option (Section 7.3) in each of its Router Advertisements [17], to
aid movement detection by mobile nodes (as in Section 11.5.1). aid movement detection by mobile nodes (as in Section 11.5.1).
The use of this option in Router Advertisements SHOULD be The use of this option in Router Advertisements SHOULD be
configurable. configurable.
o Every IPv6 router SHOULD be able to support sending unsolicited o Every IPv6 router SHOULD be able to support sending unsolicited
multicast Router Advertisements at the faster rate described in multicast Router Advertisements at the faster rate described in
Section 7.5. If the router supports a faster rate, the used rate Section 7.5. If the router supports a faster rate, the used rate
MUST be configurable. MUST be configurable.
o Each router SHOULD include at least one prefix with the Router o Each router SHOULD include at least one prefix with the Router
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In order for a mobile node to operate correctly while away from home, In order for a mobile node to operate correctly while away from home,
at least one IPv6 router on the mobile node's home link must function at least one IPv6 router on the mobile node's home link must function
as a home agent for the mobile node. The following additional as a home agent for the mobile node. The following additional
requirements apply to all IPv6 routers that serve as a home agent: requirements apply to all IPv6 routers that serve as a home agent:
o Every home agent MUST be able to maintain an entry in its Binding o Every home agent MUST be able to maintain an entry in its Binding
Cache for each mobile node for which it is serving as the home Cache for each mobile node for which it is serving as the home
agent (Section 10.1 and Section 10.3.1). agent (Section 10.1 and Section 10.3.1).
o Every home agent MUST be able to intercept packets (using proxy o Every home agent MUST be able to intercept packets (using proxy
Neighbor Discovery [18]) addressed to a mobile node for which it Neighbor Discovery [17]) addressed to a mobile node for which it
is currently serving as the home agent, on that mobile node's home is currently serving as the home agent, on that mobile node's home
link, while the mobile node is away from home (Section 10.4.1). link, while the mobile node is away from home (Section 10.4.1).
o Every home agent MUST be able to encapsulate [6] such intercepted o Every home agent MUST be able to encapsulate [6] such intercepted
packets in order to tunnel them to the primary care-of address for packets in order to tunnel them to the primary care-of address for
the mobile node indicated in its binding in the home agent's the mobile node indicated in its binding in the home agent's
Binding Cache (Section 10.4.2). Binding Cache (Section 10.4.2).
o Every home agent MUST support decapsulating [6] reverse tunneled o Every home agent MUST support decapsulating [6] reverse tunneled
packets sent to it from a mobile node's home address. Every home packets sent to it from a mobile node's home address. Every home
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o The node MUST allow route optimization to be administratively o The node MUST allow route optimization to be administratively
enabled or disabled. The default SHOULD be enabled. enabled or disabled. The default SHOULD be enabled.
o The node MAY support the multicast address listener part of a o The node MAY support the multicast address listener part of a
multicast group membership protocol as described in multicast group membership protocol as described in
Section 11.3.4. If this support is provided, the mobile node MUST Section 11.3.4. If this support is provided, the mobile node MUST
be able to receive tunneled multicast packets from the home agent. be able to receive tunneled multicast packets from the home agent.
o The node MAY support stateful address autoconfiguration mechanisms o The node MAY support stateful address autoconfiguration mechanisms
such as DHCPv6 [30] on the interface represented by the tunnel to such as DHCPv6 [29] on the interface represented by the tunnel to
the home agent. the home agent.
9. Correspondent Node Operation 9. Correspondent Node Operation
9.1. Conceptual Data Structures 9.1. Conceptual Data Structures
IPv6 nodes with route optimization support maintain a Binding Cache IPv6 nodes with route optimization support maintain a Binding Cache
of bindings for other nodes. A separate Binding Cache SHOULD be of bindings for other nodes. A separate Binding Cache SHOULD be
maintained by each IPv6 node for each of its unicast routable maintained by each IPv6 node for each of its unicast routable
addresses. The Binding Cache MAY be implemented in any manner addresses. The Binding Cache MAY be implemented in any manner
consistent with the external behavior described in this document, for consistent with the external behavior described in this document, for
example by being combined with the node's Destination Cache as example by being combined with the node's Destination Cache as
maintained by Neighbor Discovery [18]. When sending a packet, the maintained by Neighbor Discovery [17]. When sending a packet, the
Binding Cache is searched before the Neighbor Discovery conceptual Binding Cache is searched before the Neighbor Discovery conceptual
Destination Cache [18]. Destination Cache [17].
Each Binding Cache entry conceptually contains the following fields: Each Binding Cache entry conceptually contains the following fields:
o The home address of the mobile node for which this is the Binding o The home address of the mobile node for which this is the Binding
Cache entry. This field is used as the key for searching the Cache entry. This field is used as the key for searching the
Binding Cache for the destination address of a packet being sent. Binding Cache for the destination address of a packet being sent.
o The care-of address for the mobile node indicated by the home o The care-of address for the mobile node indicated by the home
address field in this Binding Cache entry. address field in this Binding Cache entry.
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node MUST silently discard the message. node MUST silently discard the message.
o The MH Type field MUST have a known value (Section 6.1.1). o The MH Type field MUST have a known value (Section 6.1.1).
Otherwise, the node MUST discard the message and issue a Binding Otherwise, the node MUST discard the message and issue a Binding
Error message as described in Section 9.3.3, with Status field set Error message as described in Section 9.3.3, with Status field set
to 2 (unrecognized MH Type value). to 2 (unrecognized MH Type value).
o The Payload Proto field MUST be IPPROTO_NONE (59 decimal). o The Payload Proto field MUST be IPPROTO_NONE (59 decimal).
Otherwise, the node MUST discard the message and SHOULD send ICMP Otherwise, the node MUST discard the message and SHOULD send ICMP
Parameter Problem, Code 0, directly to the Source Address of the Parameter Problem, Code 0, directly to the Source Address of the
packet as specified in RFC 4443 [17]. Thus no Binding Cache packet as specified in RFC 4443 [16]. Thus no Binding Cache
information is used in sending the ICMP message. The Pointer information is used in sending the ICMP message. The Pointer
field in the ICMP message SHOULD point at the Payload Proto field. field in the ICMP message SHOULD point at the Payload Proto field.
o The Header Len field in the Mobility Header MUST NOT be less than o The Header Len field in the Mobility Header MUST NOT be less than
the length specified for this particular type of message in the length specified for this particular type of message in
Section 6.1. Otherwise, the node MUST discard the message and Section 6.1. Otherwise, the node MUST discard the message and
SHOULD send ICMP Parameter Problem, Code 0, directly to the Source SHOULD send ICMP Parameter Problem, Code 0, directly to the Source
Address of the packet as specified in RFC 4443 [17]. (The Binding Address of the packet as specified in RFC 4443 [16]. (The Binding
Cache information is again not used.) The Pointer field in the Cache information is again not used.) The Pointer field in the
ICMP message SHOULD point at the Header Len field. ICMP message SHOULD point at the Header Len field.
Subsequent checks depend on the particular Mobility Header. Subsequent checks depend on the particular Mobility Header.
9.3. Packet Processing 9.3. Packet Processing
This section describes how the correspondent node sends packets to This section describes how the correspondent node sends packets to
the mobile node, and receives packets from it. the mobile node, and receives packets from it.
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9.3.2. Sending Packets to a Mobile Node 9.3.2. Sending Packets to a Mobile Node
Before sending any packet, the sending node SHOULD examine its Before sending any packet, the sending node SHOULD examine its
Binding Cache for an entry for the destination address to which the Binding Cache for an entry for the destination address to which the
packet is being sent. If the sending node has a Binding Cache entry packet is being sent. If the sending node has a Binding Cache entry
for this address, the sending node SHOULD use a type 2 routing header for this address, the sending node SHOULD use a type 2 routing header
to route the packet to this mobile node (the destination node) by way to route the packet to this mobile node (the destination node) by way
of its care-of address. However, the sending node MUST NOT do this of its care-of address. However, the sending node MUST NOT do this
in the following cases: in the following cases:
o When sending an IPv6 Neighbor Discovery [18] packet. o When sending an IPv6 Neighbor Discovery [17] packet.
o Where otherwise noted in Section 6.1. o Where otherwise noted in Section 6.1.
When calculating authentication data in a packet that contains a type When calculating authentication data in a packet that contains a type
2 routing header, the correspondent node MUST calculate the AH 2 routing header, the correspondent node MUST calculate the AH
authentication data as if the following were true: The routing header authentication data as if the following were true: The routing header
contains the care-of address, the destination IPv6 address field of contains the care-of address, the destination IPv6 address field of
the IPv6 header contains the home address, and the Segments Left the IPv6 header contains the home address, and the Segments Left
field is zero. The IPsec Security Policy Database lookup MUST based field is zero. The IPsec Security Policy Database lookup MUST based
on the mobile node's home address. on the mobile node's home address.
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The Home Address field in the Binding Error message MUST be copied The Home Address field in the Binding Error message MUST be copied
from the Home Address field in the Home Address destination option of from the Home Address field in the Home Address destination option of
the offending packet, or set to the unspecified address if no such the offending packet, or set to the unspecified address if no such
option appeared in the packet. option appeared in the packet.
Note that the IPv6 Source Address and Home Address field values Note that the IPv6 Source Address and Home Address field values
discussed above are the values from the wire, i.e., before any discussed above are the values from the wire, i.e., before any
modifications possibly performed as specified in Section 9.3.1. modifications possibly performed as specified in Section 9.3.1.
Binding Error messages SHOULD be subject to rate limiting in the same Binding Error messages SHOULD be subject to rate limiting in the same
manner as is done for ICMPv6 messages [17]. manner as is done for ICMPv6 messages [16].
9.3.4. Receiving ICMP Error Messages 9.3.4. Receiving ICMP Error Messages
When the correspondent node has a Binding Cache entry for a mobile When the correspondent node has a Binding Cache entry for a mobile
node, all traffic destined to the mobile node goes directly to the node, all traffic destined to the mobile node goes directly to the
current care-of address of the mobile node using a routing header. current care-of address of the mobile node using a routing header.
Any ICMP error message caused by packets on their way to the care-of Any ICMP error message caused by packets on their way to the care-of
address will be returned in the normal manner to the correspondent address will be returned in the normal manner to the correspondent
node. node.
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index, sequence number being out of window (Section 9.5.1), or index, sequence number being out of window (Section 9.5.1), or
insufficiency of resources (Section 9.5.2), a Binding insufficiency of resources (Section 9.5.2), a Binding
Acknowledgement MUST be sent. If the node accepts the Binding Acknowledgement MUST be sent. If the node accepts the Binding
Update, the Binding Acknowledgement SHOULD NOT be sent. Update, the Binding Acknowledgement SHOULD NOT be sent.
If the node accepts the Binding Update and creates or updates an If the node accepts the Binding Update and creates or updates an
entry for this binding, the Status field in the Binding entry for this binding, the Status field in the Binding
Acknowledgement MUST be set to a value less than 128. Otherwise, the Acknowledgement MUST be set to a value less than 128. Otherwise, the
Status field MUST be set to a value greater than or equal to 128. Status field MUST be set to a value greater than or equal to 128.
Values for the Status field are described in Section 6.1.8 and in the Values for the Status field are described in Section 6.1.8 and in the
IANA registry of assigned numbers [10]. IANA registry of assigned numbers [28].
If the Status field in the Binding Acknowledgement contains the value If the Status field in the Binding Acknowledgement contains the value
136 (expired home nonce index), 137 (expired care-of nonce index), or 136 (expired home nonce index), 137 (expired care-of nonce index), or
138 (expired nonces) then the message MUST NOT include the Binding 138 (expired nonces) then the message MUST NOT include the Binding
Authorization Data mobility option. Otherwise, the Binding Authorization Data mobility option. Otherwise, the Binding
Authorization Data mobility option MUST be included, and MUST meet Authorization Data mobility option MUST be included, and MUST meet
the specific authentication requirements for Binding Acknowledgements the specific authentication requirements for Binding Acknowledgements
as defined in Section 5.2. as defined in Section 5.2.
If the Source Address field of the IPv6 header that carried the If the Source Address field of the IPv6 header that carried the
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Section 9.1. Section 9.1.
The Home Agents List is maintained by each home agent, recording The Home Agents List is maintained by each home agent, recording
information about each router on the same link that is acting as a information about each router on the same link that is acting as a
home agent. This list is used by the dynamic home agent address home agent. This list is used by the dynamic home agent address
discovery mechanism. A router is known to be acting as a home agent, discovery mechanism. A router is known to be acting as a home agent,
if it sends a Router Advertisement in which the Home Agent (H) bit is if it sends a Router Advertisement in which the Home Agent (H) bit is
set. When the lifetime for a list entry (defined below) expires, set. When the lifetime for a list entry (defined below) expires,
that entry is removed from the Home Agents List. The Home Agents that entry is removed from the Home Agents List. The Home Agents
List is similar to the Default Router List conceptual data structure List is similar to the Default Router List conceptual data structure
maintained by each host for Neighbor Discovery [18]. The Home Agents maintained by each host for Neighbor Discovery [17]. The Home Agents
List MAY be implemented in any manner consistent with the external List MAY be implemented in any manner consistent with the external
behavior described in this document. behavior described in this document.
Each home agent maintains a separate Home Agents List for each link Each home agent maintains a separate Home Agents List for each link
on which it is serving as a home agent. A new entry is created or an on which it is serving as a home agent. A new entry is created or an
existing entry is updated in response to receipt of a valid Router existing entry is updated in response to receipt of a valid Router
Advertisement in which the Home Agent (H) bit is set. Each Home Advertisement in which the Home Agent (H) bit is set. Each Home
Agents List entry conceptually contains the following fields: Agents List entry conceptually contains the following fields:
o The link-local IP address of a home agent on the link. This o The link-local IP address of a home agent on the link. This
address is learned through the Source Address of the Router address is learned through the Source Address of the Router
Advertisements [18] received from the router. Advertisements [17] received from the router.
o One or more global IP addresses for this home agent. Global o One or more global IP addresses for this home agent. Global
addresses are learned through Prefix Information options with the addresses are learned through Prefix Information options with the
Router Address (R) bit set and received in Router Advertisements Router Address (R) bit set and received in Router Advertisements
from this link-local address. Global addresses for the router in from this link-local address. Global addresses for the router in
a Home Agents List entry MUST be deleted once the prefix a Home Agents List entry MUST be deleted once the prefix
associated with that address is no longer valid [18]. associated with that address is no longer valid [17].
o The remaining lifetime of this Home Agents List entry. If a Home o The remaining lifetime of this Home Agents List entry. If a Home
Agent Information Option is present in a Router Advertisement Agent Information Option is present in a Router Advertisement
received from a home agent, the lifetime of the Home Agents List received from a home agent, the lifetime of the Home Agents List
entry representing that home agent is initialized from the Home entry representing that home agent is initialized from the Home
Agent Lifetime field in the option (if present); otherwise, the Agent Lifetime field in the option (if present); otherwise, the
lifetime is initialized from the Router Lifetime field in the lifetime is initialized from the Router Lifetime field in the
received Router Advertisement. If Home Agents List entry lifetime received Router Advertisement. If Home Agents List entry lifetime
reaches zero, the entry MUST be deleted from the Home Agents List. reaches zero, the entry MUST be deleted from the Home Agents List.
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the home address of the mobile node. the home address of the mobile node.
The home agent MUST mark this Binding Cache entry as a home The home agent MUST mark this Binding Cache entry as a home
registration to indicate that the node is serving as a home agent for registration to indicate that the node is serving as a home agent for
this binding. Binding Cache entries marked as a home registration this binding. Binding Cache entries marked as a home registration
MUST be excluded from the normal cache replacement policy used for MUST be excluded from the normal cache replacement policy used for
the Binding Cache (Section 9.6) and MUST NOT be removed from the the Binding Cache (Section 9.6) and MUST NOT be removed from the
Binding Cache until the expiration of the Lifetime period. Binding Cache until the expiration of the Lifetime period.
Unless this home agent already has a binding for the given home Unless this home agent already has a binding for the given home
address, the home agent MUST perform Duplicate Address Detection [19] address, the home agent MUST perform Duplicate Address Detection [18]
on the mobile node's home link before returning the Binding on the mobile node's home link before returning the Binding
Acknowledgement. This ensures that no other node on the home link Acknowledgement. This ensures that no other node on the home link
was using the mobile node's home address when the Binding Update was using the mobile node's home address when the Binding Update
arrived. If this Duplicate Address Detection fails for the given arrived. If this Duplicate Address Detection fails for the given
home address or an associated link local address, then the home agent home address or an associated link local address, then the home agent
MUST reject the complete Binding Update and MUST return a Binding MUST reject the complete Binding Update and MUST return a Binding
Acknowledgement to the mobile node, in which the Status field is set Acknowledgement to the mobile node, in which the Status field is set
to 134 (Duplicate Address Detection failed). When the home agent to 134 (Duplicate Address Detection failed). When the home agent
sends a successful Binding Acknowledgement to the mobile node, the sends a successful Binding Acknowledgement to the mobile node, the
home agent assures to the mobile node that its address(es) will be home agent assures to the mobile node that its address(es) will be
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The lifetime of the Binding Cache entry depends on a number of The lifetime of the Binding Cache entry depends on a number of
factors: factors:
o The lifetime for the Binding Cache entry MUST NOT be greater than o The lifetime for the Binding Cache entry MUST NOT be greater than
the Lifetime value specified in the Binding Update. the Lifetime value specified in the Binding Update.
o The lifetime for the Binding Cache entry MUST NOT be greater than o The lifetime for the Binding Cache entry MUST NOT be greater than
the remaining valid lifetime for the subnet prefix in the mobile the remaining valid lifetime for the subnet prefix in the mobile
node's home address specified with the Binding Update. The node's home address specified with the Binding Update. The
remaining valid lifetime for this prefix is determined by the home remaining valid lifetime for this prefix is determined by the home
agent based on its own Prefix List entry [18]. agent based on its own Prefix List entry [17].
The remaining preferred lifetime SHOULD NOT have any impact on the The remaining preferred lifetime SHOULD NOT have any impact on the
lifetime for the Binding Cache entry. lifetime for the Binding Cache entry.
The home agent MUST remove a binding when the valid lifetime of The home agent MUST remove a binding when the valid lifetime of
the prefix associated with it expires. the prefix associated with it expires.
o The home agent MAY further decrease the specified lifetime for the o The home agent MAY further decrease the specified lifetime for the
binding, for example based on a local policy. The resulting binding, for example based on a local policy. The resulting
lifetime is stored by the home agent in the Binding Cache entry, lifetime is stored by the home agent in the Binding Cache entry,
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10.4.1. Intercepting Packets for a Mobile Node 10.4.1. Intercepting Packets for a Mobile Node
While a node is serving as the home agent for a mobile node it MUST While a node is serving as the home agent for a mobile node it MUST
attempt to intercept packets on the mobile node's home link that are attempt to intercept packets on the mobile node's home link that are
addressed to the mobile node. addressed to the mobile node.
In order to do this, when a node begins serving as the home agent it In order to do this, when a node begins serving as the home agent it
MUST have performed Duplicate Address Detection (as specified in MUST have performed Duplicate Address Detection (as specified in
Section 10.3.1), and subsequently it MUST multicast onto the home Section 10.3.1), and subsequently it MUST multicast onto the home
link a Neighbor Advertisement message [18] on behalf of the mobile link a Neighbor Advertisement message [17] on behalf of the mobile
node. For the home address specified in the Binding Update, the home node. For the home address specified in the Binding Update, the home
agent sends a Neighbor Advertisement message [18] to the all-nodes agent sends a Neighbor Advertisement message [17] to the all-nodes
multicast address on the home link to advertise the home agent's own multicast address on the home link to advertise the home agent's own
link-layer address for this IP address on behalf of the mobile node. link-layer address for this IP address on behalf of the mobile node.
If the Link-Layer Address Compatibility (L) flag has been specified If the Link-Layer Address Compatibility (L) flag has been specified
in the Binding Update, the home agent MUST do the same for the link- in the Binding Update, the home agent MUST do the same for the link-
local address of the mobile node. local address of the mobile node.
All fields in each Neighbor Advertisement message SHOULD be set in All fields in each Neighbor Advertisement message SHOULD be set in
the same way they would be set by the mobile node if it was sending the same way they would be set by the mobile node if it was sending
this Neighbor Advertisement [18] while at home, with the following this Neighbor Advertisement [17] while at home, with the following
exceptions: exceptions:
o The Target Address in the Neighbor Advertisement MUST be set to o The Target Address in the Neighbor Advertisement MUST be set to
the specific IP address for the mobile node. the specific IP address for the mobile node.
o The Advertisement MUST include a Target Link-layer Address option o The Advertisement MUST include a Target Link-layer Address option
specifying the home agent's link-layer address. specifying the home agent's link-layer address.
o The Router (R) bit in the Advertisement MUST be set to zero. o The Router (R) bit in the Advertisement MUST be set to zero.
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advertisement. advertisement.
Any node on the home link that receives one of the Neighbor Any node on the home link that receives one of the Neighbor
Advertisement messages (described above) will update its Neighbor Advertisement messages (described above) will update its Neighbor
Cache to associate the mobile node's address with the home agent's Cache to associate the mobile node's address with the home agent's
link layer address, causing it to transmit any future packets link layer address, causing it to transmit any future packets
normally destined to the mobile node to the mobile node's home agent. normally destined to the mobile node to the mobile node's home agent.
Since multicasting on the local link (such as Ethernet) is typically Since multicasting on the local link (such as Ethernet) is typically
not guaranteed to be reliable, the home agent MAY retransmit this not guaranteed to be reliable, the home agent MAY retransmit this
Neighbor Advertisement message up to MAX_NEIGHBOR_ADVERTISEMENT (see Neighbor Advertisement message up to MAX_NEIGHBOR_ADVERTISEMENT (see
[18]) times to increase its reliability. It is still possible that [17]) times to increase its reliability. It is still possible that
some nodes on the home link will not receive any of the Neighbor some nodes on the home link will not receive any of the Neighbor
Advertisements, but these nodes will eventually be able to detect the Advertisements, but these nodes will eventually be able to detect the
link-layer address change for the mobile node's address through use link-layer address change for the mobile node's address through use
of Neighbor Unreachability Detection [18]. of Neighbor Unreachability Detection [17].
While a node is serving as a home agent for some mobile node, the While a node is serving as a home agent for some mobile node, the
home agent uses IPv6 Neighbor Discovery [18] to intercept unicast home agent uses IPv6 Neighbor Discovery [17] to intercept unicast
packets on the home link addressed to the mobile node. In order to packets on the home link addressed to the mobile node. In order to
intercept packets in this way, the home agent MUST act as a proxy for intercept packets in this way, the home agent MUST act as a proxy for
this mobile node and reply to any received Neighbor Solicitations for this mobile node and reply to any received Neighbor Solicitations for
it. When a home agent receives a Neighbor Solicitation, it MUST it. When a home agent receives a Neighbor Solicitation, it MUST
check if the Target Address specified in the message matches the check if the Target Address specified in the message matches the
address of any mobile node for which it has a Binding Cache entry address of any mobile node for which it has a Binding Cache entry
marked as a home registration. marked as a home registration.
If such an entry exists in the home agent's Binding Cache, the home If such an entry exists in the home agent's Binding Cache, the home
agent MUST reply to the Neighbor Solicitation with a Neighbor agent MUST reply to the Neighbor Solicitation with a Neighbor
Advertisement giving the home agent's own link-layer address as the Advertisement giving the home agent's own link-layer address as the
link-layer address for the specified Target Address. In addition, link-layer address for the specified Target Address. In addition,
the Router (R) bit in the Advertisement MUST be set to zero. Acting the Router (R) bit in the Advertisement MUST be set to zero. Acting
as a proxy in this way allows other nodes on the mobile node's home as a proxy in this way allows other nodes on the mobile node's home
link to resolve the mobile node's address and for the home agent to link to resolve the mobile node's address and for the home agent to
defend these addresses on the home link for Duplicate Address defend these addresses on the home link for Duplicate Address
Detection [18]. Detection [17].
10.4.2. Processing Intercepted Packets 10.4.2. Processing Intercepted Packets
For any packet sent to a mobile node from the mobile node's home For any packet sent to a mobile node from the mobile node's home
agent (in which the home agent is the original sender of the packet), agent (in which the home agent is the original sender of the packet),
the home agent is operating as a correspondent node of the mobile the home agent is operating as a correspondent node of the mobile
node for this packet and the procedures described in Section 9.3.2 node for this packet and the procedures described in Section 9.3.2
apply. The home agent then uses a routing header to route the packet apply. The home agent then uses a routing header to route the packet
to the mobile node by way of the primary care-of address in the home to the mobile node by way of the primary care-of address in the home
agent's Binding Cache. agent's Binding Cache.
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forwarding, described in the previous section. If this support is forwarding, described in the previous section. If this support is
not provided, multicast group membership control messages are not provided, multicast group membership control messages are
silently ignored. silently ignored.
In order to forward multicast data packets from the home network to In order to forward multicast data packets from the home network to
all the proper mobile nodes, the home agent SHOULD be capable of all the proper mobile nodes, the home agent SHOULD be capable of
receiving tunneled multicast group membership control information receiving tunneled multicast group membership control information
from the mobile node in order to determine which groups the mobile from the mobile node in order to determine which groups the mobile
node has subscribed to. These multicast group membership messages node has subscribed to. These multicast group membership messages
are Listener Report messages specified in MLD [8] or in other are Listener Report messages specified in MLD [8] or in other
protocols such as [39]. protocols such as [38].
The messages are issued by the mobile node, but sent through the The messages are issued by the mobile node, but sent through the
reverse tunnel to the home agent. These messages are issued whenever reverse tunnel to the home agent. These messages are issued whenever
the mobile node decides to enable reception of packets for a the mobile node decides to enable reception of packets for a
multicast group or in response to an MLD Query from the home agent. multicast group or in response to an MLD Query from the home agent.
The mobile node will also issue multicast group control messages to The mobile node will also issue multicast group control messages to
disable reception of multicast packets when it is no longer disable reception of multicast packets when it is no longer
interested in receiving multicasts for a particular group. interested in receiving multicasts for a particular group.
To obtain the mobile node's current multicast group membership the To obtain the mobile node's current multicast group membership the
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section and the multicast forwarding in Section 10.4.2 are to be section and the multicast forwarding in Section 10.4.2 are to be
achieved. At the time of this writing it was thought that a full achieved. At the time of this writing it was thought that a full
IPv6 multicast router function would be necessary on the home agent, IPv6 multicast router function would be necessary on the home agent,
but it may be possible to achieve the same effects through a "proxy but it may be possible to achieve the same effects through a "proxy
MLD" application coupled with kernel multicast forwarding. This may MLD" application coupled with kernel multicast forwarding. This may
be the subject of future specifications. be the subject of future specifications.
10.4.4. Stateful Address Autoconfiguration 10.4.4. Stateful Address Autoconfiguration
This section describes how home agents support the use of stateful This section describes how home agents support the use of stateful
address autoconfiguration mechanisms such as DHCPv6 [30] from the address autoconfiguration mechanisms such as DHCPv6 [29] from the
mobile nodes. If this support is not provided, then the M and O bits mobile nodes. If this support is not provided, then the M and O bits
must remain cleared on the Mobile Prefix Advertisement Messages. Any must remain cleared on the Mobile Prefix Advertisement Messages. Any
mobile node which sends DHCPv6 messages to the home agent without mobile node which sends DHCPv6 messages to the home agent without
this support will not receive a response. this support will not receive a response.
If DHCPv6 is used, packets are sent with link-local source addresses If DHCPv6 is used, packets are sent with link-local source addresses
either to a link-scope multicast address or a link-local address. either to a link-scope multicast address or a link-local address.
Mobile nodes desiring to locate a DHCPv6 service may reverse tunnel Mobile nodes desiring to locate a DHCPv6 service may reverse tunnel
standard DHCPv6 packets to the home agent. Since these link-scope standard DHCPv6 packets to the home agent. Since these link-scope
packets cannot be forwarded onto the home network, it is necessary packets cannot be forwarded onto the home network, it is necessary
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10.5.1. Receiving Router Advertisement Messages 10.5.1. Receiving Router Advertisement Messages
For each link on which a router provides service as a home agent, the For each link on which a router provides service as a home agent, the
router maintains a Home Agents List recording information about all router maintains a Home Agents List recording information about all
other home agents on that link. This list is used in the dynamic other home agents on that link. This list is used in the dynamic
home agent address discovery mechanism; the mobile node uses the list home agent address discovery mechanism; the mobile node uses the list
as described in Section 11.4.1. The information for the list is as described in Section 11.4.1. The information for the list is
learned through receipt of the periodic unsolicited multicast Router learned through receipt of the periodic unsolicited multicast Router
Advertisements, in a manner similar to the Default Router List Advertisements, in a manner similar to the Default Router List
conceptual data structure maintained by each host for Neighbor conceptual data structure maintained by each host for Neighbor
Discovery [18]. In the construction of the Home Agents List, the Discovery [17]. In the construction of the Home Agents List, the
Router Advertisements are from each (other) home agent on the link Router Advertisements are from each (other) home agent on the link
and the Home Agent (H) bit is set in them. and the Home Agent (H) bit is set in them.
On receipt of a valid Router Advertisement, as defined in the On receipt of a valid Router Advertisement, as defined in the
processing algorithm specified for Neighbor Discovery [18], the home processing algorithm specified for Neighbor Discovery [17], the home
agent performs the following steps in addition to any steps already agent performs the following steps in addition to any steps already
required of it by Neighbor Discovery: required of it by Neighbor Discovery:
o If the Home Agent (H) bit in the Router Advertisement is not set, o If the Home Agent (H) bit in the Router Advertisement is not set,
delete the sending node's entry in the current Home Agents List delete the sending node's entry in the current Home Agents List
(if one exists). Skip all the following steps. (if one exists). Skip all the following steps.
o Otherwise, extract the Source Address from the IP header of the o Otherwise, extract the Source Address from the IP header of the
Router Advertisement. This is the link-local IP address on this Router Advertisement. This is the link-local IP address on this
link of the home agent sending this Advertisement [18]. link of the home agent sending this Advertisement [17].
o Determine the preference for this home agent. If the Router o Determine the preference for this home agent. If the Router
Advertisement contains a Home Agent Information Option, then the Advertisement contains a Home Agent Information Option, then the
preference is taken from the Home Agent Preference field in the preference is taken from the Home Agent Preference field in the
option; otherwise, the default preference of 0 MUST be used. option; otherwise, the default preference of 0 MUST be used.
o Determine the lifetime for this home agent. If the Router o Determine the lifetime for this home agent. If the Router
Advertisement contains a Home Agent Information Option, then the Advertisement contains a Home Agent Information Option, then the
lifetime is taken from the Home Agent Lifetime field in the lifetime is taken from the Home Agent Lifetime field in the
option; otherwise, the lifetime specified by the Router Lifetime option; otherwise, the lifetime specified by the Router Lifetime
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o If more than one global IP address is associated with a home o If more than one global IP address is associated with a home
agent, these addresses SHOULD be listed in a randomized order. agent, these addresses SHOULD be listed in a randomized order.
o The home agent SHOULD reduce the number of home agent IP addresses o The home agent SHOULD reduce the number of home agent IP addresses
so that the packet fits within the minimum IPv6 MTU [5]. The home so that the packet fits within the minimum IPv6 MTU [5]. The home
agent addresses selected for inclusion in the packet SHOULD be agent addresses selected for inclusion in the packet SHOULD be
those from the complete list with the highest preference. This those from the complete list with the highest preference. This
limitation avoids the danger of the Reply message packet being limitation avoids the danger of the Reply message packet being
fragmented (or rejected by an intermediate router with an ICMP fragmented (or rejected by an intermediate router with an ICMP
Packet Too Big message [17]). Packet Too Big message [16]).
10.6. Sending Prefix Information to the Mobile Node 10.6. Sending Prefix Information to the Mobile Node
10.6.1. List of Home Network Prefixes 10.6.1. List of Home Network Prefixes
Mobile IPv6 arranges to propagate relevant prefix information to the Mobile IPv6 arranges to propagate relevant prefix information to the
mobile node when it is away from home, so that it may be used in mobile node when it is away from home, so that it may be used in
mobile node home address configuration and in network renumbering. mobile node home address configuration and in network renumbering.
In this mechanism, mobile nodes away from home receive Mobile Prefix In this mechanism, mobile nodes away from home receive Mobile Prefix
Advertisement messages. These messages include Prefix Information Advertisement messages. These messages include Prefix Information
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If there are multiple home agents, differences in the advertisements If there are multiple home agents, differences in the advertisements
sent by different home agents can lead to an inability to use a sent by different home agents can lead to an inability to use a
particular home address when changing to another home agent. In particular home address when changing to another home agent. In
order to ensure that the mobile nodes get the same information from order to ensure that the mobile nodes get the same information from
different home agents, it is preferred that all of the home agents on different home agents, it is preferred that all of the home agents on
the same link be configured in the same manner. the same link be configured in the same manner.
To support this, the home agent monitors prefixes advertised by To support this, the home agent monitors prefixes advertised by
itself and other home agents on the home link. In Neighbor Discovery itself and other home agents on the home link. In Neighbor Discovery
(RFC 4861 [18]) it is acceptable for two routers to advertise (RFC 4861 [17]) it is acceptable for two routers to advertise
different sets of prefixes on the same link. For home agents, the different sets of prefixes on the same link. For home agents, the
differences should be detected for a given home address because the differences should be detected for a given home address because the
mobile node communicates only with one home agent at a time and the mobile node communicates only with one home agent at a time and the
mobile node needs to know the full set of prefixes assigned to the mobile node needs to know the full set of prefixes assigned to the
home link. All other comparisons of Router Advertisements are as home link. All other comparisons of Router Advertisements are as
specified in Section 6.2.7 of RFC 4861. specified in Section 6.2.7 of RFC 4861.
10.6.2. Scheduling Prefix Deliveries 10.6.2. Scheduling Prefix Deliveries
A home agent serving a mobile node will schedule the delivery of the A home agent serving a mobile node will schedule the delivery of the
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relying on Mobile IPv6. If application running on the mobile node relying on Mobile IPv6. If application running on the mobile node
has no particular knowledge that the communication being sent fits has no particular knowledge that the communication being sent fits
within this general type of communication, however, the mobile within this general type of communication, however, the mobile
node should not use its care-of address as the source of the node should not use its care-of address as the source of the
packet in this way. packet in this way.
The choice of the most efficient communications method is The choice of the most efficient communications method is
application specific, and outside the scope of this specification. application specific, and outside the scope of this specification.
The APIs necessary for controlling the choice are also out of The APIs necessary for controlling the choice are also out of
scope. One example of such an API is described in the IPv6 Socket scope. One example of such an API is described in the IPv6 Socket
API for Source Address Selection specification [42]. API for Source Address Selection specification [41].
o While not at its home link, the mobile node MUST NOT use the Home o While not at its home link, the mobile node MUST NOT use the Home
Address destination option when communicating with link-local Address destination option when communicating with link-local
peers. peers.
Similarly, the mobile node MUST NOT use the Home Address Similarly, the mobile node MUST NOT use the Home Address
destination option for IPv6 Neighbor Discovery [18] packets. destination option for IPv6 Neighbor Discovery [17] packets.
Detailed operation of these cases is described later in this section Detailed operation of these cases is described later in this section
and also discussed in [32]. and also discussed in [31].
For packets sent by a mobile node while it is at home, no special For packets sent by a mobile node while it is at home, no special
Mobile IPv6 processing is required. Likewise, if the mobile node Mobile IPv6 processing is required. Likewise, if the mobile node
uses any address other than one of its home addresses as the source uses any address other than one of its home addresses as the source
of a packet sent while away from home, no special Mobile IPv6 of a packet sent while away from home, no special Mobile IPv6
processing is required. In either case, the packet is simply processing is required. In either case, the packet is simply
addressed and transmitted in the same way as any normal IPv6 packet. addressed and transmitted in the same way as any normal IPv6 packet.
For packets sent by the mobile node sent while away from home using For packets sent by the mobile node sent while away from home using
the mobile node's home address as the source, special Mobile IPv6 the mobile node's home address as the source, special Mobile IPv6
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* Change the Source Address field in the packet's IPv6 header to * Change the Source Address field in the packet's IPv6 header to
one of the mobile node's care-of addresses. This will one of the mobile node's care-of addresses. This will
typically be the mobile node's current primary care-of address, typically be the mobile node's current primary care-of address,
but MUST be an address assigned to the interface on the link but MUST be an address assigned to the interface on the link
being used. being used.
By using the care-of address as the Source Address in the IPv6 By using the care-of address as the Source Address in the IPv6
header, with the mobile node's home address instead in the Home header, with the mobile node's home address instead in the Home
Address option, the packet will be able to safely pass through any Address option, the packet will be able to safely pass through any
router implementing ingress filtering [28]. router implementing ingress filtering [26].
Reverse Tunneling Reverse Tunneling
This is the mechanism which tunnels the packets via the home This is the mechanism which tunnels the packets via the home
agent. It is not as efficient as the above mechanism, but is agent. It is not as efficient as the above mechanism, but is
needed if there is no binding yet with the correspondent node. needed if there is no binding yet with the correspondent node.
This mechanism is used for packets that have the mobile node's This mechanism is used for packets that have the mobile node's
home address as the Source Address in the IPv6 header, or with home address as the Source Address in the IPv6 header, or with
multicast control protocol packets as described in Section 11.3.4. multicast control protocol packets as described in Section 11.3.4.
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However, such an exchange is not required, as long as the result However, such an exchange is not required, as long as the result
of the authentication calculation remains the same. of the authentication calculation remains the same.
When an automated key management protocol is used to create new When an automated key management protocol is used to create new
security associations for a peer, it is important to ensure that the security associations for a peer, it is important to ensure that the
peer can send the key management protocol packets to the mobile node. peer can send the key management protocol packets to the mobile node.
This may not be possible if the peer is the home agent of the mobile This may not be possible if the peer is the home agent of the mobile
node and the purpose of the security associations would be to send a node and the purpose of the security associations would be to send a
Binding Update to the home agent. Packets addressed to the home Binding Update to the home agent. Packets addressed to the home
address of the mobile node cannot be used before the Binding Update address of the mobile node cannot be used before the Binding Update
has been processed. For the default case of using IKEv2 [44] as the has been processed. For the default case of using IKEv2 [43] as the
automated key management protocol, such problems can be avoided by automated key management protocol, such problems can be avoided by
the following requirements when communicating with its home agent: the following requirements when communicating with its home agent:
o When the mobile node is away from home, it MUST use its care-of o When the mobile node is away from home, it MUST use its care-of
address as the Source Address of all packets it sends as part of address as the Source Address of all packets it sends as part of
the key management protocol (without use of Mobile IPv6 for these the key management protocol (without use of Mobile IPv6 for these
packets, as suggested in Section 11.3.1). packets, as suggested in Section 11.3.1).
The Key Management Mobility Capability (K) bit in Binding Updates and The Key Management Mobility Capability (K) bit in Binding Updates and
Acknowledgements can be used to avoid the need to rerun IKEv2 upon Acknowledgements can be used to avoid the need to rerun IKEv2 upon
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In order to receive packets sent to some multicast group, a mobile In order to receive packets sent to some multicast group, a mobile
node must join that multicast group. One method, in which a mobile node must join that multicast group. One method, in which a mobile
node MAY join the group, is via a (local) multicast router on the node MAY join the group, is via a (local) multicast router on the
foreign link being visited. In this case, the mobile node MUST use foreign link being visited. In this case, the mobile node MUST use
its care-of address and MUST NOT use the Home Address destination its care-of address and MUST NOT use the Home Address destination
option when sending MLD packets [8]. option when sending MLD packets [8].
Alternatively, a mobile node MAY join multicast groups via a bi- Alternatively, a mobile node MAY join multicast groups via a bi-
directional tunnel to its home agent. The mobile node tunnels its directional tunnel to its home agent. The mobile node tunnels its
multicast group membership control packets (such as those defined in multicast group membership control packets (such as those defined in
[8] or in [39]) to its home agent, and the home agent forwards [8] or in [38]) to its home agent, and the home agent forwards
multicast packets down the tunnel to the mobile node. A mobile node multicast packets down the tunnel to the mobile node. A mobile node
MUST NOT tunnel multicast group membership control packets until (1) MUST NOT tunnel multicast group membership control packets until (1)
the mobile node has a binding in place at the home agent, and (2) the the mobile node has a binding in place at the home agent, and (2) the
latter sends at least one multicast group membership control packet latter sends at least one multicast group membership control packet
via the tunnel. Once this condition is true, the mobile node SHOULD via the tunnel. Once this condition is true, the mobile node SHOULD
assume it does not change as long as the binding does not expire. assume it does not change as long as the binding does not expire.
A mobile node that wishes to send packets to a multicast group also A mobile node that wishes to send packets to a multicast group also
has two options: has two options:
1. Send directly on the foreign link being visited. 1. Send directly on the foreign link being visited.
To do this, the application uses the care-of address as a source To do this, the application uses the care-of address as a source
address for multicast traffic, just as it would use a stationary address for multicast traffic, just as it would use a stationary
address. This requires that the application either knows the address. This requires that the application either knows the
care-of address, or uses an API such as the IPv6 Socket API for care-of address, or uses an API such as the IPv6 Socket API for
Source Address Selection specification [42] to request that the Source Address Selection specification [41] to request that the
care-of address be used as the source address in transmitted care-of address be used as the source address in transmitted
packets. The mobile node MUST NOT use Home Address destination packets. The mobile node MUST NOT use Home Address destination
option in such traffic. option in such traffic.
2. Send via a tunnel to its home agent. 2. Send via a tunnel to its home agent.
Because multicast routing in general depends upon the Source Because multicast routing in general depends upon the Source
Address used in the IPv6 header of the multicast packet, a mobile Address used in the IPv6 header of the multicast packet, a mobile
node that tunnels a multicast packet to its home agent MUST use node that tunnels a multicast packet to its home agent MUST use
its home address as the IPv6 Source Address of the inner its home address as the IPv6 Source Address of the inner
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11.4.3. Receiving Mobile Prefix Advertisements 11.4.3. Receiving Mobile Prefix Advertisements
Section 10.6 describes the operation of a home agent to support boot Section 10.6 describes the operation of a home agent to support boot
time configuration and renumbering a mobile node's home subnet while time configuration and renumbering a mobile node's home subnet while
the mobile node is away from home. The home agent sends Mobile the mobile node is away from home. The home agent sends Mobile
Prefix Advertisements to the mobile node while away from home, giving Prefix Advertisements to the mobile node while away from home, giving
"important" Prefix Information options that describe changes in the "important" Prefix Information options that describe changes in the
prefixes in use on the mobile node's home link. prefixes in use on the mobile node's home link.
The Mobile Prefix Solicitation is similar to the Router Solicitation The Mobile Prefix Solicitation is similar to the Router Solicitation
used in Neighbor Discovery [18], except it is routed from the mobile used in Neighbor Discovery [17], except it is routed from the mobile
node on the visited network to the home agent on the home network by node on the visited network to the home agent on the home network by
usual unicast routing rules. usual unicast routing rules.
When a mobile node receives a Mobile Prefix Advertisement, it MUST When a mobile node receives a Mobile Prefix Advertisement, it MUST
validate it according to the following test: validate it according to the following test:
o The Source Address of the IP packet carrying the Mobile Prefix o The Source Address of the IP packet carrying the Mobile Prefix
Advertisement is the same as the home agent address to which the Advertisement is the same as the home agent address to which the
mobile node last sent an accepted home registration Binding Update mobile node last sent an accepted home registration Binding Update
to register its primary care-of address. Otherwise, if no such to register its primary care-of address. Otherwise, if no such
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Otherwise, the advertisement is unsolicited, and MUST be Otherwise, the advertisement is unsolicited, and MUST be
discarded. In this case the mobile node SHOULD send a Mobile discarded. In this case the mobile node SHOULD send a Mobile
Prefix Solicitation. Prefix Solicitation.
Any received Mobile Prefix Advertisement not meeting these tests MUST Any received Mobile Prefix Advertisement not meeting these tests MUST
be silently discarded. be silently discarded.
For an accepted Mobile Prefix Advertisement, the mobile node MUST For an accepted Mobile Prefix Advertisement, the mobile node MUST
process Managed Address Configuration (M), Other Stateful process Managed Address Configuration (M), Other Stateful
Configuration (O), and the Prefix Information Options as if they Configuration (O), and the Prefix Information Options as if they
arrived in a Router Advertisement [18] on the mobile node's home arrived in a Router Advertisement [17] on the mobile node's home
link. (This specification does not, however, describe how to acquire link. (This specification does not, however, describe how to acquire
home addresses through stateful protocols.) Such processing may home addresses through stateful protocols.) Such processing may
result in the mobile node configuring a new home address, although result in the mobile node configuring a new home address, although
due to separation between preferred lifetime and valid lifetime, such due to separation between preferred lifetime and valid lifetime, such
changes should not affect most communications by the mobile node, in changes should not affect most communications by the mobile node, in
the same way as for nodes that are at home. the same way as for nodes that are at home.
This specification assumes that any security associations and This specification assumes that any security associations and
security policy entries that may be needed for new prefixes have been security policy entries that may be needed for new prefixes have been
pre-configured in the mobile node. Note that while dynamic key pre-configured in the mobile node. Note that while dynamic key
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reachable, in which case the mobile node must discover a new default reachable, in which case the mobile node must discover a new default
router (usually on a new link). However, this detection only occurs router (usually on a new link). However, this detection only occurs
when the mobile node has packets to send, and in the absence of when the mobile node has packets to send, and in the absence of
frequent Router Advertisements or indications from the link-layer, frequent Router Advertisements or indications from the link-layer,
the mobile node might become unaware of an L3 handover that occurred. the mobile node might become unaware of an L3 handover that occurred.
Therefore, the mobile node should supplement this method with other Therefore, the mobile node should supplement this method with other
information whenever it is available to the mobile node (e.g., from information whenever it is available to the mobile node (e.g., from
lower protocol layers). lower protocol layers).
When the mobile node detects an L3 handover, it performs Duplicate When the mobile node detects an L3 handover, it performs Duplicate
Address Detection [19] on its link-local address, selects a new Address Detection [18] on its link-local address, selects a new
default router as a consequence of Router Discovery, and then default router as a consequence of Router Discovery, and then
performs Prefix Discovery with that new router to form new care-of performs Prefix Discovery with that new router to form new care-of
address(es) as described in Section 11.5.3. It then registers its address(es) as described in Section 11.5.3. It then registers its
new primary care-of address with its home agent as described in new primary care-of address with its home agent as described in
Section 11.7.1. After updating its home registration, the mobile Section 11.7.1. After updating its home registration, the mobile
node then updates associated mobility bindings in correspondent nodes node then updates associated mobility bindings in correspondent nodes
that it is performing route optimization with as specified in that it is performing route optimization with as specified in
Section 11.7.2. Section 11.7.2.
Due to the temporary packet flow disruption and signaling overhead Due to the temporary packet flow disruption and signaling overhead
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receive Router Advertisements with the same link-local source receive Router Advertisements with the same link-local source
address. This might be common if routers use the same link-local address. This might be common if routers use the same link-local
address on multiple interfaces. This issue can be avoided when address on multiple interfaces. This issue can be avoided when
routers use the Router Address (R) bit, since that provides a routers use the Router Address (R) bit, since that provides a
global address of the router. global address of the router.
In addition, the mobile node should consider the following events as In addition, the mobile node should consider the following events as
indications that an L3 handover may have occurred. Upon receiving indications that an L3 handover may have occurred. Upon receiving
such indications, the mobile node needs to perform Router Discovery such indications, the mobile node needs to perform Router Discovery
to discover routers and prefixes on the new link, as described in to discover routers and prefixes on the new link, as described in
Section 6.3.7 of Neighbor Discovery (RFC 4861 [18]). Section 6.3.7 of Neighbor Discovery (RFC 4861 [17]).
o If Router Advertisements that the mobile node receives include an o If Router Advertisements that the mobile node receives include an
Advertisement Interval option, the mobile node may use its Advertisement Interval option, the mobile node may use its
Advertisement Interval field as an indication of the frequency Advertisement Interval field as an indication of the frequency
with which it should expect to continue to receive future with which it should expect to continue to receive future
Advertisements from that router. This field specifies the minimum Advertisements from that router. This field specifies the minimum
rate (the maximum amount of time between successive rate (the maximum amount of time between successive
Advertisements) that the mobile node should expect. If this Advertisements) that the mobile node should expect. If this
amount of time elapses without the mobile node receiving any amount of time elapses without the mobile node receiving any
Advertisement from this router, the mobile node can be sure that Advertisement from this router, the mobile node can be sure that
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When an MN detects that it has arrived on a new link using the When an MN detects that it has arrived on a new link using the
movement detection algorithm in use (Section 11.5.1,) or on movement detection algorithm in use (Section 11.5.1,) or on
bootstrapping, it performs the following steps to determine if it is bootstrapping, it performs the following steps to determine if it is
on the home link. on the home link.
o The MN performs the procedure described in Section 11.5.3 and o The MN performs the procedure described in Section 11.5.3 and
configures an address. It also keeps track of all the on-link configures an address. It also keeps track of all the on-link
prefix(es) received in the RA along with their prefix lengths. prefix(es) received in the RA along with their prefix lengths.
o If the home prefix has not been statically configured the MN uses o If the home prefix has not been statically configured the MN uses
some form of bootstrapping procedure (e.g. RFC5026 [22]) to some form of bootstrapping procedure (e.g. RFC5026 [21]) to
determine the home prefix. determine the home prefix.
o Given the availability of the home prefix, the MN checks whether o Given the availability of the home prefix, the MN checks whether
or not the home prefix matches one of the prefixes received in the or not the home prefix matches one of the prefixes received in the
RA. If it does, the MN concludes that it is connected to the home RA. If it does, the MN concludes that it is connected to the home
link. link.
11.5.3. Forming New Care-of Addresses 11.5.3. Forming New Care-of Addresses
After detecting that it has moved a mobile node SHOULD generate a new After detecting that it has moved a mobile node SHOULD generate a new
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registered with its home agent), but it MAY have an additional registered with its home agent), but it MAY have an additional
care-of address for any or all of the prefixes on its current link. care-of address for any or all of the prefixes on its current link.
Furthermore, since a wireless network interface may actually allow a Furthermore, since a wireless network interface may actually allow a
mobile node to be reachable on more than one link at a time (i.e., mobile node to be reachable on more than one link at a time (i.e.,
within wireless transmitter range of routers on more than one within wireless transmitter range of routers on more than one
separate link), a mobile node MAY have care-of addresses on more than separate link), a mobile node MAY have care-of addresses on more than
one link at a time. The use of more than one care-of address at a one link at a time. The use of more than one care-of address at a
time is described in Section 11.5.4. time is described in Section 11.5.4.
As described in Section 4, in order to form a new care-of address, a As described in Section 4, in order to form a new care-of address, a
mobile node MAY use either stateless [19] or stateful (e.g., DHCPv6 mobile node MAY use either stateless [18] or stateful (e.g., DHCPv6
[30]) Address Autoconfiguration. If a mobile node needs to use a [29]) Address Autoconfiguration. If a mobile node needs to use a
source address (other than the unspecified address) in packets sent source address (other than the unspecified address) in packets sent
as a part of address autoconfiguration, it MUST use an IPv6 link- as a part of address autoconfiguration, it MUST use an IPv6 link-
local address rather than its own IPv6 home address. local address rather than its own IPv6 home address.
RFC 4862 [19] specifies that in normal processing for Duplicate RFC 4862 [18] specifies that in normal processing for Duplicate
Address Detection, the node SHOULD delay sending the initial Neighbor Address Detection, the node SHOULD delay sending the initial Neighbor
Solicitation message by a random delay between 0 and Solicitation message by a random delay between 0 and
MAX_RTR_SOLICITATION_DELAY. Since delaying DAD can result in MAX_RTR_SOLICITATION_DELAY. Since delaying DAD can result in
significant delays in configuring a new care-of address when the significant delays in configuring a new care-of address when the
Mobile Node moves to a new link, the Mobile Node preferably SHOULD Mobile Node moves to a new link, the Mobile Node preferably SHOULD
NOT delay DAD when configuring a new care-of address. The Mobile NOT delay DAD when configuring a new care-of address. The Mobile
Node SHOULD delay according to the mechanisms specified in RFC 4862 Node SHOULD delay according to the mechanisms specified in RFC 4862
unless the implementation has a behavior that desynchronizes the unless the implementation has a behavior that desynchronizes the
steps that happen before the DAD in the case that multiple nodes steps that happen before the DAD in the case that multiple nodes
experience handover at the same time. Such desynchronizing behaviors experience handover at the same time. Such desynchronizing behaviors
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Acknowledge (A) bits set its home agent, as described on Acknowledge (A) bits set its home agent, as described on
Section 11.7.1. Section 11.7.1.
To assist with smooth handovers, a mobile node SHOULD retain its To assist with smooth handovers, a mobile node SHOULD retain its
previous primary care-of address as a (non-primary) care-of address, previous primary care-of address as a (non-primary) care-of address,
and SHOULD still accept packets at this address, even after and SHOULD still accept packets at this address, even after
registering its new primary care-of address with its home agent. registering its new primary care-of address with its home agent.
This is reasonable, since the mobile node could only receive packets This is reasonable, since the mobile node could only receive packets
at its previous primary care-of address if it were indeed still at its previous primary care-of address if it were indeed still
connected to that link. If the previous primary care-of address was connected to that link. If the previous primary care-of address was
allocated using stateful Address Autoconfiguration [30], the mobile allocated using stateful Address Autoconfiguration [29], the mobile
node may not wish to release the address immediately upon switching node may not wish to release the address immediately upon switching
to a new primary care-of address. to a new primary care-of address.
Whenever a mobile node determines that it is no longer reachable Whenever a mobile node determines that it is no longer reachable
through a given link, it SHOULD invalidate all care-of addresses through a given link, it SHOULD invalidate all care-of addresses
associated with address prefixes that it discovered from routers on associated with address prefixes that it discovered from routers on
the unreachable link which are not in the current set of address the unreachable link which are not in the current set of address
prefixes advertised by the (possibly new) current default router. prefixes advertised by the (possibly new) current default router.
11.5.5. Returning Home 11.5.5. Returning Home
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intercept all packets sent to the mobile's home address and tunnel intercept all packets sent to the mobile's home address and tunnel
them to the previously registered care-of address. them to the previously registered care-of address.
In this home registration, the mobile node MUST set the Acknowledge In this home registration, the mobile node MUST set the Acknowledge
(A) and Home Registration (H) bits, set the Lifetime field to zero, (A) and Home Registration (H) bits, set the Lifetime field to zero,
and set the care-of address for the binding to the mobile node's own and set the care-of address for the binding to the mobile node's own
home address. The mobile node MUST use its home address as the home address. The mobile node MUST use its home address as the
source address in the Binding Update. source address in the Binding Update.
When sending this Binding Update to its home agent, the mobile node When sending this Binding Update to its home agent, the mobile node
must be careful in how it uses Neighbor Solicitation [18] (if needed) must be careful in how it uses Neighbor Solicitation [17] (if needed)
to learn the home agent's link-layer address, since the home agent to learn the home agent's link-layer address, since the home agent
will be currently configured to intercept packets to the mobile will be currently configured to intercept packets to the mobile
node's home address using Proxy Neighbor Discovery (Proxy ND). In node's home address using Proxy Neighbor Discovery (Proxy ND). In
particular, the mobile node is unable to use its home address as the particular, the mobile node is unable to use its home address as the
Source Address in the Neighbor Solicitation until the home agent Source Address in the Neighbor Solicitation until the home agent
stops defending the home address. stops defending the home address.
Neighbor Solicitation by the mobile node for the home agent's address Neighbor Solicitation by the mobile node for the home agent's address
will normally not be necessary, since the mobile node has already will normally not be necessary, since the mobile node has already
learned the home agent's link-layer address from a Source Link-Layer learned the home agent's link-layer address from a Source Link-Layer
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the Binding Acknowledgement from the home agent may require the Binding Acknowledgement from the home agent may require
performing Neighbor Discovery, and the mobile node may not be able to performing Neighbor Discovery, and the mobile node may not be able to
distinguish Neighbor Solicitations coming from the home agent from distinguish Neighbor Solicitations coming from the home agent from
other Neighbor Solicitations. Note that a race condition exists other Neighbor Solicitations. Note that a race condition exists
where both the mobile node and the home agent respond to the same where both the mobile node and the home agent respond to the same
solicitations sent by other nodes; this will be only temporary, solicitations sent by other nodes; this will be only temporary,
however, until the Binding Update is accepted. however, until the Binding Update is accepted.
After receiving the Binding Acknowledgement for its Binding Update to After receiving the Binding Acknowledgement for its Binding Update to
its home agent, the mobile node MUST multicast onto the home link (to its home agent, the mobile node MUST multicast onto the home link (to
the all-nodes multicast address) a Neighbor Advertisement [18], to the all-nodes multicast address) a Neighbor Advertisement [17], to
advertise the mobile node's own link-layer address for its own home advertise the mobile node's own link-layer address for its own home
address. The Target Address in this Neighbor Advertisement MUST be address. The Target Address in this Neighbor Advertisement MUST be
set to the mobile node's home address, and the Advertisement MUST set to the mobile node's home address, and the Advertisement MUST
include a Target Link-layer Address option specifying the mobile include a Target Link-layer Address option specifying the mobile
node's link-layer address. The mobile node MUST multicast such a node's link-layer address. The mobile node MUST multicast such a
Neighbor Advertisement for each of its home addresses, as defined by Neighbor Advertisement for each of its home addresses, as defined by
the current on-link prefixes, including its link-local address. The the current on-link prefixes, including its link-local address. The
Solicited Flag (S) in these Advertisements MUST NOT be set, since Solicited Flag (S) in these Advertisements MUST NOT be set, since
they were not solicited by any Neighbor Solicitation. The Override they were not solicited by any Neighbor Solicitation. The Override
Flag (O) in these Advertisements MUST be set, indicating that the Flag (O) in these Advertisements MUST be set, indicating that the
Advertisements SHOULD override any existing Neighbor Cache entries at Advertisements SHOULD override any existing Neighbor Cache entries at
any node receiving them. any node receiving them.
Since multicasting on the local link (such as Ethernet) is typically Since multicasting on the local link (such as Ethernet) is typically
not guaranteed to be reliable, the mobile node MAY retransmit these not guaranteed to be reliable, the mobile node MAY retransmit these
Neighbor Advertisements [18] up to MAX_NEIGHBOR_ADVERTISEMENT times Neighbor Advertisements [17] up to MAX_NEIGHBOR_ADVERTISEMENT times
to increase their reliability. It is still possible that some nodes to increase their reliability. It is still possible that some nodes
on the home link will not receive any of these Neighbor on the home link will not receive any of these Neighbor
Advertisements, but these nodes will eventually be able to recover Advertisements, but these nodes will eventually be able to recover
through use of Neighbor Unreachability Detection [18]. through use of Neighbor Unreachability Detection [17].
Note that the tunnel via the home agent typically stops operating at Note that the tunnel via the home agent typically stops operating at
the same time that the home registration is deleted. the same time that the home registration is deleted.
11.6. Return Routability Procedure 11.6. Return Routability Procedure
This section defines the rules that the mobile node must follow when This section defines the rules that the mobile node must follow when
performing the return routability procedure. Section 11.7.2 performing the return routability procedure. Section 11.7.2
describes the rules when the return routability procedure needs to be describes the rules when the return routability procedure needs to be
initiated. initiated.
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protocol will not be able to protect care-of addresses in the IPv6 protocol will not be able to protect care-of addresses in the IPv6
header. (Mobile IPv6 implementations that know they are using header. (Mobile IPv6 implementations that know they are using
IPsec AH to protect a particular message might avoid this option. IPsec AH to protect a particular message might avoid this option.
For brevity the usage of AH is not discussed in this document.) For brevity the usage of AH is not discussed in this document.)
o If the mobile node's link-local address has the same interface o If the mobile node's link-local address has the same interface
identifier as the home address for which it is supplying a new identifier as the home address for which it is supplying a new
care-of address, then the mobile node SHOULD set the Link-Local care-of address, then the mobile node SHOULD set the Link-Local
Address Compatibility (L) bit. Address Compatibility (L) bit.
o If the home address was generated using RFC 4941 [21], then the o If the home address was generated using RFC 4941 [20], then the
link local address is unlikely to have a compatible interface link local address is unlikely to have a compatible interface
identifier. In this case, the mobile node MUST clear the Link- identifier. In this case, the mobile node MUST clear the Link-
Local Address Compatibility (L) bit. Local Address Compatibility (L) bit.
o If the IPsec security associations between the mobile node and the o If the IPsec security associations between the mobile node and the
home agent have been established dynamically, and the mobile node home agent have been established dynamically, and the mobile node
has the capability to update its endpoint in the used key has the capability to update its endpoint in the used key
management protocol to the new care-of address every time it management protocol to the new care-of address every time it
moves, the mobile node SHOULD set the Key Management Mobility moves, the mobile node SHOULD set the Key Management Mobility
Capability (K) bit in the Binding Update. Otherwise, the mobile Capability (K) bit in the Binding Update. Otherwise, the mobile
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address. Therefore, the mobile node MUST treat the creation of a new address. Therefore, the mobile node MUST treat the creation of a new
binding with the home agent using an existing home address, the same binding with the home agent using an existing home address, the same
as creation of a new home address. In the unlikely event that the as creation of a new home address. In the unlikely event that the
mobile node's home address is autoconfigured as the IPv6 address of mobile node's home address is autoconfigured as the IPv6 address of
another network node on the home network, the home agent will reply another network node on the home network, the home agent will reply
to the mobile node's subsequent Binding Update with a Binding to the mobile node's subsequent Binding Update with a Binding
Acknowledgement containing a Status of 134 (Duplicate Address Acknowledgement containing a Status of 134 (Duplicate Address
Detection failed). In this case, the mobile node MUST NOT attempt to Detection failed). In this case, the mobile node MUST NOT attempt to
re-use the same home address. It SHOULD continue to register the re-use the same home address. It SHOULD continue to register the
care-of addresses for its other home addresses, if any. Mechanisms care-of addresses for its other home addresses, if any. Mechanisms
outlined in "Mobile IPv6 Bootstrapping in Split Scenario" [22] allow outlined in "Mobile IPv6 Bootstrapping in Split Scenario" [21] allow
mobile nodes to acquire new home addresses to replace the one for mobile nodes to acquire new home addresses to replace the one for
which Status 134 was received. which Status 134 was received.
11.7.2. Correspondent Registration 11.7.2. Correspondent Registration
When the mobile node is assured that its home address is valid, it When the mobile node is assured that its home address is valid, it
can initiate a correspondent registration with the purpose of can initiate a correspondent registration with the purpose of
allowing the correspondent node to cache the mobile node's current allowing the correspondent node to cache the mobile node's current
care-of address. This procedure consists of the return routability care-of address. This procedure consists of the return routability
procedure followed by a registration. procedure followed by a registration.
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Min: 0.03 seconds Min: 0.03 seconds
MinMobPfxAdvInterval Default: 600 seconds MinMobPfxAdvInterval Default: 600 seconds
InitialBindackTimeoutFirstReg Default: 1.5 seconds InitialBindackTimeoutFirstReg Default: 1.5 seconds
Home agents MUST allow the first three variables to be configured by Home agents MUST allow the first three variables to be configured by
system management, and mobile nodes MUST allow the last variable to system management, and mobile nodes MUST allow the last variable to
be configured by system management. be configured by system management.
The default value for InitialBindackTimeoutFirstReg has been The default value for InitialBindackTimeoutFirstReg has been
calculated as 1.5 times the default value of RetransTimer, as calculated as 1.5 times the default value of RetransTimer, as
specified in Neighbor Discovery (RFC 4861 [18]) times the default specified in Neighbor Discovery (RFC 4861 [17]) times the default
value of DupAddrDetectTransmits, as specified in Stateless Address value of DupAddrDetectTransmits, as specified in Stateless Address
Autoconfiguration (RFC 4862 [19]) Autoconfiguration (RFC 4862 [18])
The value MinDelayBetweenRAs overrides the value of the protocol The value MinDelayBetweenRAs overrides the value of the protocol
constant MIN_DELAY_BETWEEN_RAS, as specified in Neighbor Discovery constant MIN_DELAY_BETWEEN_RAS, as specified in Neighbor Discovery
(RFC 4861 [18]). This variable SHOULD be set to MinRtrAdvInterval, (RFC 4861 [17]). This variable SHOULD be set to MinRtrAdvInterval,
if MinRtrAdvInterval is less than 3 seconds. if MinRtrAdvInterval is less than 3 seconds.
14. IANA Considerations 14. IANA Considerations
This document defines a new IPv6 protocol, the Mobility Header, This document defines a new IPv6 protocol, the Mobility Header,
described in Section 6.1. This protocol has been assigned protocol described in Section 6.1. This protocol has been assigned protocol
number 135. number 135.
This document also creates a new name space "Mobility Header Type", This document also creates a new name space "Mobility Header Type",
for the MH Type field in the Mobility Header. The current message for the MH Type field in the Mobility Header. The current message
skipping to change at page 146, line 33 skipping to change at page 147, line 33
4 Care-of Test 4 Care-of Test
5 Binding Update 5 Binding Update
6 Binding Acknowledgement 6 Binding Acknowledgement
7 Binding Error 7 Binding Error
Future values of the MH Type can be allocated using Standards Action Future values of the MH Type can be allocated using Standards Action
or IESG Approval [23]. or IESG Approval [22].
Furthermore, each mobility message may contain mobility options as Furthermore, each mobility message may contain mobility options as
described in Section 6.2. This document defines a new name space described in Section 6.2. This document defines a new name space
"Mobility Option" to identify these options. The current mobility "Mobility Option" to identify these options. The current mobility
options are defined starting from Section 6.2.2 and are the options are defined starting from Section 6.2.2 and are the
following: following:
0 Pad1 0 Pad1
1 PadN 1 PadN
2 Binding Refresh Advice 2 Binding Refresh Advice
3 Alternate Care-of Address 3 Alternate Care-of Address
4 Nonce Indices 4 Nonce Indices
5 Authorization Data 5 Authorization Data
Future values of the Option Type can be allocated using Standards Future values of the Option Type can be allocated using Standards
Action or IESG Approval [23]. Action or IESG Approval [22].
Finally, this document creates a third new name space "Status Code" Finally, this document creates a third new name space "Status Code"
for the Status field in the Binding Acknowledgement message. The for the Status field in the Binding Acknowledgement message. The
current values are listed in Section 6.1.8 and are the following: current values are listed in Section 6.1.8 and are the following:
0 Binding Update accepted 0 Binding Update accepted
1 Accepted but prefix discovery necessary 1 Accepted but prefix discovery necessary
128 Reason unspecified 128 Reason unspecified
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137 Expired care-of nonce index 137 Expired care-of nonce index
138 Expired nonces 138 Expired nonces
139 Registration type change disallowed 139 Registration type change disallowed
TBD Invalid Care-of Address TBD Invalid Care-of Address
Future values of the Status field can be allocated using Standards Future values of the Status field can be allocated using Standards
Action or IESG Approval [23]. Action or IESG Approval [22].
All fields labeled "Reserved" are only to be assigned through All fields labeled "Reserved" are only to be assigned through
Standards Action or IESG Approval. Standards Action or IESG Approval.
This document also defines a new IPv6 destination option, the Home This document also defines a new IPv6 destination option, the Home
Address option, described in Section 6.3. This option has been Address option, described in Section 6.3. This option has been
assigned the Option Type value 0xC9. assigned the Option Type value 0xC9.
This document also defines a new IPv6 type 2 routing header, This document also defines a new IPv6 type 2 routing header,
described in Section 6.4. The value 2 has been allocated by IANA. described in Section 6.4. The value 2 has been allocated by IANA.
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o The Home Agent Address Discovery Request message, described in o The Home Agent Address Discovery Request message, described in
Section 6.5; Section 6.5;
o The Home Agent Address Discovery Reply message, described in o The Home Agent Address Discovery Reply message, described in
Section 6.6; Section 6.6;
o The Mobile Prefix Solicitation, described in Section 6.7; and o The Mobile Prefix Solicitation, described in Section 6.7; and
o The Mobile Prefix Advertisement, described in Section 6.8. o The Mobile Prefix Advertisement, described in Section 6.8.
This document also defines two new Neighbor Discovery [18] options, This document also defines two new Neighbor Discovery [17] options,
which have been assigned Option Type values within the option which have been assigned Option Type values within the option
numbering space for Neighbor Discovery messages: numbering space for Neighbor Discovery messages:
o The Advertisement Interval option, described in Section 7.3; and o The Advertisement Interval option, described in Section 7.3; and
o The Home Agent Information option, described in Section 7.4. o The Home Agent Information option, described in Section 7.4.
15. Security Considerations 15. Security Considerations
15.1. Threats 15.1. Threats
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Service attack. For example, the correspondent node might be a Service attack. For example, the correspondent node might be a
site that will send a high-bandwidth stream of video to anyone who site that will send a high-bandwidth stream of video to anyone who
asks for it. Note that the use of flow-control protocols such as asks for it. Note that the use of flow-control protocols such as
TCP does not necessarily defend against this type of attack, TCP does not necessarily defend against this type of attack,
because the attacker can fake the acknowledgements. Even keeping because the attacker can fake the acknowledgements. Even keeping
TCP initial sequence numbers secret does not help, because the TCP initial sequence numbers secret does not help, because the
attacker can receive the first few segments (including the ISN) at attacker can receive the first few segments (including the ISN) at
its own address, and only then redirect the stream to the victim's its own address, and only then redirect the stream to the victim's
address. These types of attacks may also be directed to networks address. These types of attacks may also be directed to networks
instead of nodes. Further variations of this threat are described instead of nodes. Further variations of this threat are described
elsewhere [29] [34]. elsewhere [27] [33].
An attacker might also attempt to disrupt a mobile node's An attacker might also attempt to disrupt a mobile node's
communications by replaying a Binding Update that the node had communications by replaying a Binding Update that the node had
sent earlier. If the old Binding Update was accepted, packets sent earlier. If the old Binding Update was accepted, packets
destined for the mobile node would be sent to its old location as destined for the mobile node would be sent to its old location as
opposed to its current location. opposed to its current location.
A malicious mobile node associated to multiple home agents could A malicious mobile node associated to multiple home agents could
create a routing loop amongst them. This can be achieved when a create a routing loop amongst them. This can be achieved when a
mobile node binds one home address located on a first home agent mobile node binds one home address located on a first home agent
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Address destination option, a new routing header type (type 2), Address destination option, a new routing header type (type 2),
and uses tunneling headers in the payload packets. The protocol and uses tunneling headers in the payload packets. The protocol
must protect against potential new threats involving the use of must protect against potential new threats involving the use of
these mechanisms. these mechanisms.
Third parties become exposed to a reflection threat via the Home Third parties become exposed to a reflection threat via the Home
Address destination option, unless appropriate security Address destination option, unless appropriate security
precautions are followed. The Home Address destination option precautions are followed. The Home Address destination option
could be used to direct response traffic toward a node whose IP could be used to direct response traffic toward a node whose IP
address appears in the option. In this case, ingress filtering address appears in the option. In this case, ingress filtering
would not catch the forged "return address" [37] [41]. would not catch the forged "return address" [36] [40].
A similar threat exists with the tunnels between the mobile node A similar threat exists with the tunnels between the mobile node
and the home agent. An attacker might forge tunnel packets and the home agent. An attacker might forge tunnel packets
between the mobile node and the home agent, making it appear that between the mobile node and the home agent, making it appear that
the traffic is coming from the mobile node when it is not. Note the traffic is coming from the mobile node when it is not. Note
that an attacker who is able to forge tunnel packets would that an attacker who is able to forge tunnel packets would
typically also be able to forge packets that appear to come typically also be able to forge packets that appear to come
directly from the mobile node. This is not a new threat as such. directly from the mobile node. This is not a new threat as such.
However, it may make it easier for attackers to escape detection However, it may make it easier for attackers to escape detection
by avoiding ingress filtering and packet tracing mechanisms. by avoiding ingress filtering and packet tracing mechanisms.
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The above mechanisms do not show that the care-of address given in The above mechanisms do not show that the care-of address given in
the Binding Update is correct. This opens the possibility for the Binding Update is correct. This opens the possibility for
Denial-of-Service attacks against third parties. However, since the Denial-of-Service attacks against third parties. However, since the
mobile node and home agent have a security association, the home mobile node and home agent have a security association, the home
agent can always identify an ill-behaving mobile node. This allows agent can always identify an ill-behaving mobile node. This allows
the home agent operator to discontinue the mobile node's service, and the home agent operator to discontinue the mobile node's service, and
possibly take further actions based on the business relationship with possibly take further actions based on the business relationship with
the mobile node's owner. the mobile node's owner.
Note that the use of a single pair of manually keyed security Note that the use of a single pair of manually keyed security
associations conflicts with the generation of a new home address [21] associations conflicts with the generation of a new home address [20]
for the mobile node, or with the adoption of a new home subnet for the mobile node, or with the adoption of a new home subnet
prefix. This is because IPsec security associations are bound to the prefix. This is because IPsec security associations are bound to the
used addresses. While certificate-based automatic keying alleviates used addresses. While certificate-based automatic keying alleviates
this problem to an extent, it is still necessary to ensure that a this problem to an extent, it is still necessary to ensure that a
given mobile node cannot send Binding Updates for the address of given mobile node cannot send Binding Updates for the address of
another mobile node. In general, this leads to the inclusion of home another mobile node. In general, this leads to the inclusion of home
addresses in certificates in the Subject AltName field. This again addresses in certificates in the Subject AltName field. This again
limits the introduction of new addresses without either manual or limits the introduction of new addresses without either manual or
automatic procedures to establish new certificates. Therefore, this automatic procedures to establish new certificates. Therefore, this
specification restricts the generation of new home addresses (for any specification restricts the generation of new home addresses (for any
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vulnerability exists if either the sequence number space is cycled vulnerability exists if either the sequence number space is cycled
through, or if the home agent reboots and forgets its sequence through, or if the home agent reboots and forgets its sequence
numbers (and uses volatile memory to store the sequence numbers). numbers (and uses volatile memory to store the sequence numbers).
Assuming the mobile node moves continuously every 10 minutes, it Assuming the mobile node moves continuously every 10 minutes, it
takes roughly 455 days before the sequence number space has been takes roughly 455 days before the sequence number space has been
cycled through. Typical movement patterns rarely reach this high cycled through. Typical movement patterns rarely reach this high
frequency today. frequency today.
o A mobile node and its home agent belong to the same domain. If o A mobile node and its home agent belong to the same domain. If
this were not the case, manual keying would not be possible [40], this were not the case, manual keying would not be possible [39],
but in Mobile IPv6 only these two parties need to know the but in Mobile IPv6 only these two parties need to know the
manually configured keys. Similarly, we note that Mobile IPv6 manually configured keys. Similarly, we note that Mobile IPv6
employs standard block ciphers in IPsec, and is not vulnerable to employs standard block ciphers in IPsec, and is not vulnerable to
problems associated with stream ciphers and manual keying. problems associated with stream ciphers and manual keying.
o It is expected that the owner of the mobile node and the o It is expected that the owner of the mobile node and the
administrator of the home agent agree on the used keys and other administrator of the home agent agree on the used keys and other
parameters with some off-line mechanism. parameters with some off-line mechanism.
The use of IKEv2 with Mobile IPv6 is documented in more detail in The use of IKEv2 with Mobile IPv6 is documented in more detail in
[20]. The following should be observed regarding the use of IKEv2: [19]. The following should be observed regarding the use of IKEv2:
o It is necessary to prevent a mobile node from claiming another o It is necessary to prevent a mobile node from claiming another
mobile node's home address. The home agent must verify that the mobile node's home address. The home agent must verify that the
mobile node trying to negotiate the SA for a particular home mobile node trying to negotiate the SA for a particular home
address is authorized for that home address. This implies that address is authorized for that home address. This implies that
even with the use of IKEv2, a policy entry needs to be configured even with the use of IKEv2, a policy entry needs to be configured
for each home address served by the home agent. for each home address served by the home agent.
It may be possible to include home addresses in the Subject It may be possible to include home addresses in the Subject
AltName field of certificate to avoid this. However, AltName field of certificate to avoid this. However,
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available. available.
The resulting level of security is in theory the same even without The resulting level of security is in theory the same even without
this additional protection: the return routability tokens are this additional protection: the return routability tokens are
still exposed only to one path within the whole Internet. still exposed only to one path within the whole Internet.
However, the mobile nodes are often found on an insecure link, However, the mobile nodes are often found on an insecure link,
such as a public access Wireless LAN. Thus, in many cases, this such as a public access Wireless LAN. Thus, in many cases, this
addition makes a practical difference. addition makes a practical difference.
For further information about the design rationale of the return For further information about the design rationale of the return
routability procedure, see [29] [34] [33] [41]. The mechanisms used routability procedure, see [27] [33] [32] [40]. The mechanisms used
have been adopted from these documents. have been adopted from these documents.
15.4.2. Achieved Security Properties 15.4.2. Achieved Security Properties
The return routability procedure protects Binding Updates against all The return routability procedure protects Binding Updates against all
attackers who are unable to monitor the path between the home agent attackers who are unable to monitor the path between the home agent
and the correspondent node. The procedure does not defend against and the correspondent node. The procedure does not defend against
attackers who can monitor this path. Note that such attackers are in attackers who can monitor this path. Note that such attackers are in
any case able to mount an active attack against the mobile node when any case able to mount an active attack against the mobile node when
it is at its home location. The possibility of such attacks is not it is at its home location. The possibility of such attacks is not
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particular if these links are publicly accessible wireless LANs. particular if these links are publicly accessible wireless LANs.
Attacks against the routers or switches on the path are typically Attacks against the routers or switches on the path are typically
harder to accomplish. The security on layer 2 of the links plays harder to accomplish. The security on layer 2 of the links plays
then a major role in the resulting overall network security. then a major role in the resulting overall network security.
Similarly, security of IPv6 Neighbor and Router Discovery on these Similarly, security of IPv6 Neighbor and Router Discovery on these
links has a large impact. If these were secured using some new links has a large impact. If these were secured using some new
technology in the future, this could change the situation technology in the future, this could change the situation
regarding the easiest point of attack. regarding the easiest point of attack.
For a more in-depth discussion of these issues, see [41]. For a more in-depth discussion of these issues, see [40].
15.4.4. Replay Attacks 15.4.4. Replay Attacks
The return routability procedure also protects the participants The return routability procedure also protects the participants
against replayed Binding Updates. The attacker is unable replay the against replayed Binding Updates. The attacker is unable replay the
same message due to the sequence number which is a part of the same message due to the sequence number which is a part of the
Binding Update. It is also unable to modify the Binding Update since Binding Update. It is also unable to modify the Binding Update since
the MAC verification would fail after such a modification. the MAC verification would fail after such a modification.
Care must be taken when removing bindings at the correspondent node, Care must be taken when removing bindings at the correspondent node,
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Binding Update arrives. This is achieved through the construct of Binding Update arrives. This is achieved through the construct of
keygen tokens from the nonces and node keys that are not specific to keygen tokens from the nonces and node keys that are not specific to
individual mobile nodes. The keygen tokens can be reconstructed by individual mobile nodes. The keygen tokens can be reconstructed by
the correspondent node, based on the home and care-of address the correspondent node, based on the home and care-of address
information that arrives with the Binding Update. This means that information that arrives with the Binding Update. This means that
the correspondent nodes are safe against memory exhaustion attacks the correspondent nodes are safe against memory exhaustion attacks
except where on-path attackers are concerned. Due to the use of except where on-path attackers are concerned. Due to the use of
symmetric cryptography, the correspondent nodes are relatively safe symmetric cryptography, the correspondent nodes are relatively safe
against CPU resource exhaustion attacks as well. against CPU resource exhaustion attacks as well.
Nevertheless, as [29] describes, there are situations in which it is Nevertheless, as [27] describes, there are situations in which it is
impossible for the mobile and correspondent nodes to determine if impossible for the mobile and correspondent nodes to determine if
they actually need a binding or whether they just have been fooled they actually need a binding or whether they just have been fooled
into believing so by an attacker. Therefore, it is necessary to into believing so by an attacker. Therefore, it is necessary to
consider situations where such attacks are being made. consider situations where such attacks are being made.
Even if route optimization is a very important optimization, it is Even if route optimization is a very important optimization, it is
still only an optimization. A mobile node can communicate with a still only an optimization. A mobile node can communicate with a
correspondent node even if the correspondent refuses to accept any correspondent node even if the correspondent refuses to accept any
Binding Updates. However, performance will suffer because packets Binding Updates. However, performance will suffer because packets
from the correspondent node to the mobile node will be routed via the from the correspondent node to the mobile node will be routed via the
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dynamic home agent address discovery messages. Therefore the home dynamic home agent address discovery messages. Therefore the home
agent cannot verify the home address of the mobile node that agent cannot verify the home address of the mobile node that
requested the list of home agents. requested the list of home agents.
Apart from discovering the address(es) of home agents, attackers will Apart from discovering the address(es) of home agents, attackers will
not be able to learn much from this information, and mobile nodes not be able to learn much from this information, and mobile nodes
cannot be tricked into using wrong home agents, as all other cannot be tricked into using wrong home agents, as all other
communication with the home agents is secure. communication with the home agents is secure.
In cases where additional security is needed, one may consider In cases where additional security is needed, one may consider
instead the use of MIPv6 bootstrapping [22], (based on DNS SRV instead the use of MIPv6 bootstrapping [21], (based on DNS SRV
Resource Records [9]) in conjunction with security mechanisms Resource Records [9]) in conjunction with security mechanisms
suggested in these specifications. In that solution, security is suggested in these specifications. In that solution, security is
provided by the DNSSEC [12] framework. The needed pre-configured provided by the DNSSEC [12] framework. The needed pre-configured
data on the mobile node for this mechanism is the domain name of the data on the mobile node for this mechanism is the domain name of the
mobile service provider, which is marginally better than the home mobile service provider, which is marginally better than the home
subnet prefix. For the security, a trust anchor which dominates the subnet prefix. For the security, a trust anchor which dominates the
domain is needed. domain is needed.
15.6. Mobile Prefix Discovery 15.6. Mobile Prefix Discovery
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another location. Administrators should be aware of this when another location. Administrators should be aware of this when
allowing such home addresses. In particular, the outer IP address allowing such home addresses. In particular, the outer IP address
check described above is not sufficient against all attackers. The check described above is not sufficient against all attackers. The
use of encrypted tunnels is particularly useful for these kinds of use of encrypted tunnels is particularly useful for these kinds of
home addresses. home addresses.
15.8. Home Address Option 15.8. Home Address Option
When the mobile node sends packets directly to the correspondent When the mobile node sends packets directly to the correspondent
node, the Source Address field of the packet's IPv6 header is the node, the Source Address field of the packet's IPv6 header is the
care-of address. Therefore, ingress filtering [28] works in the care-of address. Therefore, ingress filtering [26] works in the
usual manner even for mobile nodes, as the Source Address is usual manner even for mobile nodes, as the Source Address is
topologically correct. The Home Address option is used to inform the topologically correct. The Home Address option is used to inform the
correspondent node of the mobile node's home address. correspondent node of the mobile node's home address.
However, the care-of address in the Source Address field does not However, the care-of address in the Source Address field does not
survive in replies sent by the correspondent node unless it has a survive in replies sent by the correspondent node unless it has a
binding for this mobile node. Also, not all attacker tracing binding for this mobile node. Also, not all attacker tracing
mechanisms work when packets are being reflected through mechanisms work when packets are being reflected through
correspondent nodes using the Home Address option. For these correspondent nodes using the Home Address option. For these
reasons, this specification restricts the use of the Home Address reasons, this specification restricts the use of the Home Address
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This implies that a device which implements the filtering of packets This implies that a device which implements the filtering of packets
should be able to distinguish between a type 2 routing header and should be able to distinguish between a type 2 routing header and
other routing headers, as required in Section 8.3. This is necessary other routing headers, as required in Section 8.3. This is necessary
in order to allow Mobile IPv6 traffic while still having the option in order to allow Mobile IPv6 traffic while still having the option
of filtering out other uses of routing headers. of filtering out other uses of routing headers.
16. Contributors 16. Contributors
Work done by Tuomas Aura, Mike Roe, Greg O'Shea, Pekka Nikander, Erik Work done by Tuomas Aura, Mike Roe, Greg O'Shea, Pekka Nikander, Erik
Nordmark, and Michael Thomas shaped the return routability protocols Nordmark, and Michael Thomas shaped the return routability protocols
described in [34]. described in [33].
Significant contributions were made by members of the Mobile IPv6 Significant contributions were made by members of the Mobile IPv6
Security Design Team, including (in alphabetical order) Gabriel Security Design Team, including (in alphabetical order) Gabriel
Montenegro, Erik Nordmark and Pekka Nikander. Montenegro, Erik Nordmark and Pekka Nikander.
17. Acknowledgements 17. Acknowledgements
We would like to thank the members of the Mobile IP, Mobility We would like to thank the members of the Mobile IP, Mobility
Extensions for IPv6, and IPng Working Groups for their comments and Extensions for IPv6, and IPng Working Groups for their comments and
suggestions on this work. We would particularly like to thank (in suggestions on this work. We would particularly like to thank (in
skipping to change at page 167, line 17 skipping to change at page 168, line 17
18.1. Normative References 18.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[2] Kent, S. and K. Seo, "Security Architecture for the Internet [2] Kent, S. and K. Seo, "Security Architecture for the Internet
Protocol", RFC 4301, December 2005. Protocol", RFC 4301, December 2005.
[3] Kent, S., "IP Authentication Header", RFC 4302, December 2005. [3] Kent, S., "IP Authentication Header", RFC 4302, December 2005.
[4] Kent, S. and R. Atkinson, "IP Encapsulating Security Payload [4] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303,
(ESP)", RFC 2406, November 1998. December 2005.
[5] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) [5] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification", RFC 2460, December 1998. Specification", RFC 2460, December 1998.
[6] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6 [6] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6
Specification", RFC 2473, December 1998. Specification", RFC 2473, December 1998.
[7] Johnson, D. and S. Deering, "Reserved IPv6 Subnet Anycast [7] Johnson, D. and S. Deering, "Reserved IPv6 Subnet Anycast
Addresses", RFC 2526, March 1999. Addresses", RFC 2526, March 1999.
[8] Deering, S., Fenner, W., and B. Haberman, "Multicast Listener [8] Deering, S., Fenner, W., and B. Haberman, "Multicast Listener
Discovery (MLD) for IPv6", RFC 2710, October 1999. Discovery (MLD) for IPv6", RFC 2710, October 1999.
[9] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for [9] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782, specifying the location of services (DNS SRV)", RFC 2782,
February 2000. February 2000.
[10] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by an On- [10] National Institute of Standards and Technology, "Secure Hash
line Database", RFC 3232, January 2002.
[11] National Institute of Standards and Technology, "Secure Hash
Standard", FIPS PUB 180-1, April 1995, Standard", FIPS PUB 180-1, April 1995,
<http://www.itl.nist.gov/fipspubs/fip180-1.htm>. <http://www.itl.nist.gov/fipspubs/fip180-1.htm>.
[11] Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec to
Protect Mobile IPv6 Signaling Between Mobile Nodes and Home
Agents", RFC 3776, June 2004.
[12] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, [12] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
"DNS Security Introduction and Requirements", RFC 4033, "DNS Security Introduction and Requirements", RFC 4033,
March 2005. March 2005.
[13] Eastlake, D., Schiller, J., and S. Crocker, "Randomness [13] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
Requirements for Security", BCP 106, RFC 4086, June 2005. Requirements for Security", BCP 106, RFC 4086, June 2005.
[14] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast [14] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005. Addresses", RFC 4193, October 2005.
[15] Hinden, R. and S. Deering, "IP Version 6 Addressing [15] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006. Architecture", RFC 4291, February 2006.
[16] Eastlake, D., "Cryptographic Algorithm Implementation [16] Conta, A., Deering, S., and M. Gupta, "Internet Control Message
Requirements for Encapsulating Security Payload (ESP) and
Authentication Header (AH)", RFC 4305, December 2005.
[17] Conta, A., Deering, S., and M. Gupta, "Internet Control Message
Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6)
Specification", RFC 4443, March 2006. Specification", RFC 4443, March 2006.
[18] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, [17] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007. September 2007.
[19] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address [18] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address
Autoconfiguration", RFC 4862, September 2007. Autoconfiguration", RFC 4862, September 2007.
[20] Devarapalli, V. and F. Dupont, "Mobile IPv6 Operation with [19] Devarapalli, V. and F. Dupont, "Mobile IPv6 Operation with
IKEv2 and the Revised IPsec Architecture", RFC 4877, IKEv2 and the Revised IPsec Architecture", RFC 4877,
April 2007. April 2007.
[21] Narten, T., Draves, R., and S. Krishnan, "Privacy Extensions [20] Narten, T., Draves, R., and S. Krishnan, "Privacy Extensions
for Stateless Address Autoconfiguration in IPv6", RFC 4941, for Stateless Address Autoconfiguration in IPv6", RFC 4941,
September 2007. September 2007.
[22] Giaretta, G., Kempf, J., and V. Devarapalli, "Mobile IPv6 [21] Giaretta, G., Kempf, J., and V. Devarapalli, "Mobile IPv6
Bootstrapping in Split Scenario", RFC 5026, October 2007. Bootstrapping in Split Scenario", RFC 5026, October 2007.
[23] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA [22] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.
18.2. Informative References 18.2. Informative References
[24] Perkins, C., "IP Encapsulation within IP", RFC 2003, [23] Perkins, C., "IP Encapsulation within IP", RFC 2003,
October 1996. October 1996.
[25] Perkins, C., "Minimal Encapsulation within IP", RFC 2004, [24] Perkins, C., "Minimal Encapsulation within IP", RFC 2004,
October 1996. October 1996.
[26] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-Hashing [25] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-Hashing
for Message Authentication", RFC 2104, February 1997. for Message Authentication", RFC 2104, February 1997.
[27] Harkins, D. and D. Carrel, "The Internet Key Exchange (IKE)", [26] Ferguson, P. and D. Senie, "Network Ingress Filtering:
RFC 2409, November 1998.
[28] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, May 2000. Address Spoofing", BCP 38, RFC 2827, May 2000.
[29] Aura, T. and J. Arkko, "MIPv6 BU Attacks and Defenses", [27] Aura, T. and J. Arkko, "MIPv6 BU Attacks and Defenses",
draft-aura-mipv6-bu-attacks-01 (work in progress), March 2002. draft-aura-mipv6-bu-attacks-01 (work in progress), March 2002.
[30] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. [28] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by an On-
line Database", RFC 3232, January 2002.
[29] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
Carney, "Dynamic Host Configuration Protocol for IPv6 Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003. (DHCPv6)", RFC 3315, July 2003.
[31] Perkins, C., "IP Mobility Support for IPv4", RFC 3344, [30] Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
August 2002. August 2002.
[32] Draves, R., "Default Address Selection for Internet Protocol [31] Draves, R., "Default Address Selection for Internet Protocol
version 6 (IPv6)", RFC 3484, February 2003. version 6 (IPv6)", RFC 3484, February 2003.
[33] Nordmark, E., "Securing MIPv6 BUs using return routability [32] Nordmark, E., "Securing MIPv6 BUs using return routability
(BU3WAY)", draft-nordmark-mobileip-bu3way-00 (work in (BU3WAY)", draft-nordmark-mobileip-bu3way-00 (work in
progress), November 2001. progress), November 2001.
[34] Roe, M., "Authentication of Mobile IPv6 Binding Updates and [33] Roe, M., "Authentication of Mobile IPv6 Binding Updates and
Acknowledgments", draft-roe-mobileip-updateauth-02 (work in Acknowledgments", draft-roe-mobileip-updateauth-02 (work in
progress), March 2002. progress), March 2002.
[35] Chowdhury, K. and A. Yegin, "MIP6-bootstrapping for the [34] Chowdhury, K. and A. Yegin, "MIP6-bootstrapping for the
Integrated Scenario", Integrated Scenario",
draft-ietf-mip6-bootstrapping-integrated-dhc-06 (work in draft-ietf-mip6-bootstrapping-integrated-dhc-06 (work in
progress), April 2008. progress), April 2008.
[36] Savola, P., "Use of /127 Prefix Length Between Routers [35] Savola, P., "Use of /127 Prefix Length Between Routers
Considered Harmful", RFC 3627, September 2003. Considered Harmful", RFC 3627, September 2003.
[37] Savola, P., "Security of IPv6 Routing Header and Home Address [36] Savola, P., "Security of IPv6 Routing Header and Home Address
Options", draft-savola-ipv6-rh-ha-security-02 (work in Options", draft-savola-ipv6-rh-ha-security-02 (work in
progress), March 2002. progress), March 2002.
[38] Manner, J. and M. Kojo, "Mobility Related Terminology", [37] Manner, J. and M. Kojo, "Mobility Related Terminology",
RFC 3753, June 2004. RFC 3753, June 2004.
[39] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2 [38] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2
(MLDv2) for IPv6", RFC 3810, June 2004. (MLDv2) for IPv6", RFC 3810, June 2004.
[40] Bellovin, S. and R. Housley, "Guidelines for Cryptographic Key [39] Bellovin, S. and R. Housley, "Guidelines for Cryptographic Key
Management", BCP 107, RFC 4107, June 2005. Management", BCP 107, RFC 4107, June 2005.
[41] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E. [40] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E.
Nordmark, "Mobile IP Version 6 Route Optimization Security Nordmark, "Mobile IP Version 6 Route Optimization Security
Design Background", RFC 4225, December 2005. Design Background", RFC 4225, December 2005.
[42] Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6 Socket [41] Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6 Socket
API for Source Address Selection", RFC 5014, September 2007. API for Source Address Selection", RFC 5014, September 2007.
[43] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation of [42] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation of
Type 0 Routing Headers in IPv6", RFC 5095, December 2007. Type 0 Routing Headers in IPv6", RFC 5095, December 2007.
[44] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, "Internet Key [43] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, "Internet Key
Exchange Protocol Version 2 (IKEv2)", RFC 5996, September 2010. Exchange Protocol Version 2 (IKEv2)", RFC 5996, September 2010.
Appendix A. Future Extensions Appendix A. Future Extensions
A.1. Piggybacking A.1. Piggybacking
This document does not specify how to piggyback payload packets on This document does not specify how to piggyback payload packets on
the binding related messages. However, it is envisioned that this the binding related messages. However, it is envisioned that this
can be specified in a separate document when issues such as the can be specified in a separate document when issues such as the
interaction between piggybacking and IPsec are fully resolved (see interaction between piggybacking and IPsec are fully resolved (see
skipping to change at page 173, line 33 skipping to change at page 174, line 33
Fixed. Fixed.
Issue #5 Wrong protocol number (2 instead of 135) used in discussion Issue #5 Wrong protocol number (2 instead of 135) used in discussion
about checksum pseudo-header. about checksum pseudo-header.
Fixed. See Section 6.1.1. Fixed. See Section 6.1.1.
Issue #8 Application using the care-of address [Julien Laganier] Issue #8 Application using the care-of address [Julien Laganier]
Cite IPv6 Socket API for Source Address Selection specification Cite IPv6 Socket API for Source Address Selection specification
[42]. See Section 11.3.4. [41]. See Section 11.3.4.
Issue #10 The usage of "HA lifetime" [Ryuji Wakikawa] Issue #10 The usage of "HA lifetime" [Ryuji Wakikawa]
The mobile node SHOULD store the list of home agents for later use The mobile node SHOULD store the list of home agents for later use
in case the home agent currently managing the mobile node's in case the home agent currently managing the mobile node's
care-of address forwarding should become unavailable. See care-of address forwarding should become unavailable. See
Section 11.4.1. Section 11.4.1.
Issue #11 De-registration when returning home [Vijay Devarapalli] Issue #11 De-registration when returning home [Vijay Devarapalli]
skipping to change at page 174, line 16 skipping to change at page 175, line 16
Fixed. See Section 4.2. Fixed. See Section 4.2.
Issue #13 Home Link Detection [Suresh Krishnan] Issue #13 Home Link Detection [Suresh Krishnan]
Proposal: add Section 11.5.2 for Home Link Detection, drawing on Proposal: add Section 11.5.2 for Home Link Detection, drawing on
Internet Draft draft-krishnan-mext-hld. Internet Draft draft-krishnan-mext-hld.
Issue #14 References to Bootstrapping [Vijay Devarapalli] Issue #14 References to Bootstrapping [Vijay Devarapalli]
Cite "Mobile IPv6 Bootstrapping in Split Scenario" [22] and "MIP6 Cite "Mobile IPv6 Bootstrapping in Split Scenario" [21] and "MIP6
bootstrapping for the Integrated Scenario" [35]. See Section 4.1. bootstrapping for the Integrated Scenario" [34]. See Section 4.1.
Issue #17 Multi-homed mobile node can cause routing loop between Issue #17 Multi-homed mobile node can cause routing loop between
home agents [Benjamin Lim] home agents [Benjamin Lim]
Added security advisory in Section 15.1, to highlight risk of Added security advisory in Section 15.1, to highlight risk of
routing loop among HAs (e.g., in 3GPP): routing loop among HAs (e.g., in 3GPP):
A malicious mobile node associated to multiple home agents could A malicious mobile node associated to multiple home agents could
create a routing loop amongst them. This would happen when a create a routing loop amongst them. This would happen when a
mobile node binds one home address located on a first home agent mobile node binds one home address located on a first home agent
skipping to change at page 174, line 49 skipping to change at page 175, line 49
according to Section 11.7.1. See Section 11.3.6. according to Section 11.7.1. See Section 11.3.6.
Issue #19 BU de-registration race condition [Kilian Weniger] Issue #19 BU de-registration race condition [Kilian Weniger]
Problem arises if de-registration arrives at Home Agent before an Problem arises if de-registration arrives at Home Agent before an
immediately preceding Binding Update. immediately preceding Binding Update.
Solution: Home Agent defers BCE removal after sending the Binding Solution: Home Agent defers BCE removal after sending the Binding
Acknowledgement. See Section 10.3.2. Acknowledgement. See Section 10.3.2.
Issue #6 Minor editorial corrections and updates Issue #6 Minor editorial corrections and updates.
Update IKE references to IKEv2
cite RFC 5996 [44] instead of RFC 2409 [27] Update IPsec and IKE references to the revised IPsec architecture
and IKEv2.
Authors' Addresses Authors' Addresses
Charles E. Perkins Charles E. Perkins
Tellabs Inc. Tellabs Inc.
3590 N. 1st Street, Suite 300 3590 N. 1st Street, Suite 300
San Jose CA 95134 San Jose CA 95134
USA USA
Email: charliep@computer.org Email: charliep@computer.org
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