draft-ietf-hip-multihoming-07.txt   draft-ietf-hip-multihoming-08.txt 
Network Working Group T. Henderson, Ed. Network Working Group T. Henderson, Ed.
Internet-Draft University of Washington Internet-Draft University of Washington
Intended status: Standards Track C. Vogt Intended status: Standards Track C. Vogt
Expires: August 3, 2016 J. Arkko Expires: October 9, 2016 J. Arkko
Ericsson Research NomadicLab Ericsson Research NomadicLab
January 31, 2016 April 7, 2016
Host Multihoming with the Host Identity Protocol Host Multihoming with the Host Identity Protocol
draft-ietf-hip-multihoming-07 draft-ietf-hip-multihoming-08
Abstract Abstract
This document defines host multihoming extensions to the Host This document defines host multihoming extensions to the Host
Identity Protocol (HIP), by leveraging protocol components defined Identity Protocol (HIP), by leveraging protocol components defined
for host mobility. for host mobility.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
skipping to change at page 1, line 34 skipping to change at page 1, line 34
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 3, 2016. This Internet-Draft will expire on October 9, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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not be created outside the IETF Standards Process, except to format not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other it for publication as an RFC or to translate it into languages other
than English. than English.
Table of Contents Table of Contents
1. Introduction and Scope . . . . . . . . . . . . . . . . . . . 2 1. Introduction and Scope . . . . . . . . . . . . . . . . . . . 2
2. Terminology and Conventions . . . . . . . . . . . . . . . . . 3 2. Terminology and Conventions . . . . . . . . . . . . . . . . . 3
3. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . 4 3. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . 4
4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Host Multihoming . . . . . . . . . . . . . . . . . . . . 5 4.1. Background . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Site Multihoming . . . . . . . . . . . . . . . . . . . . 6 4.2. Multiple Addresses . . . . . . . . . . . . . . . . . . . 6
4.3. Dual host multihoming . . . . . . . . . . . . . . . . . . 7 4.3. Multiple Security Associations . . . . . . . . . . . . . 6
4.4. Combined Mobility and Multihoming . . . . . . . . . . . . 7 4.4. Host Multihoming for Fault Tolerance . . . . . . . . . . 7
4.5. Initiating the Protocol in R1 or I2 . . . . . . . . . . . 8 4.5. Host Multihoming for Load Balancing . . . . . . . . . . . 8
4.6. Using LOCATOR_SETs across Addressing Realms . . . . . . . 9 4.6. Site Multihoming . . . . . . . . . . . . . . . . . . . . 9
5. Other Considerations . . . . . . . . . . . . . . . . . . . . 9 4.7. Dual Host Multihoming . . . . . . . . . . . . . . . . . . 10
5.1. Address Verification . . . . . . . . . . . . . . . . . . 9 4.8. Combined Mobility and Multihoming . . . . . . . . . . . . 11
5.2. Preferred Locator . . . . . . . . . . . . . . . . . . . . 10 4.9. Initiating the Protocol in R1, I2, or R2 . . . . . . . . 11
5.3. Interaction with Security Associations . . . . . . . . . 10 4.10. Using LOCATOR_SETs across Addressing Realms . . . . . . . 12
6. Processing Rules . . . . . . . . . . . . . . . . . . . . . . 12 4.11. Interaction with Security Associations . . . . . . . . . 13
6.1. Sending LOCATOR_SETs . . . . . . . . . . . . . . . . . . 12 5. Processing Rules . . . . . . . . . . . . . . . . . . . . . . 13
6.2. Handling Received LOCATOR_SETs . . . . . . . . . . . . . 14 5.1. Sending LOCATOR_SETs . . . . . . . . . . . . . . . . . . 13
6.3. Verifying Address Reachability . . . . . . . . . . . . . 16 5.2. Handling Received LOCATOR_SETs . . . . . . . . . . . . . 15
6.4. Changing the Preferred Locator . . . . . . . . . . . . . 16 5.3. Verifying Address Reachability . . . . . . . . . . . . . 17
7. Security Considerations . . . . . . . . . . . . . . . . . . . 17 5.4. Changing the Preferred Locator . . . . . . . . . . . . . 18
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 6. Security Considerations . . . . . . . . . . . . . . . . . . . 18
9. Authors and Acknowledgments . . . . . . . . . . . . . . . . . 17 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 8. Authors and Acknowledgments . . . . . . . . . . . . . . . . . 19
10.1. Normative references . . . . . . . . . . . . . . . . . . 17 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.2. Informative references . . . . . . . . . . . . . . . . . 18 9.1. Normative references . . . . . . . . . . . . . . . . . . 19
Appendix A. Document Revision History . . . . . . . . . . . . . 19 9.2. Informative references . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 Appendix A. Document Revision History . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction and Scope 1. Introduction and Scope
The Host Identity Protocol [RFC7401] (HIP) supports an architecture The Host Identity Protocol [RFC7401] (HIP) supports an architecture
that decouples the transport layer (TCP, UDP, etc.) from the that decouples the transport layer (TCP, UDP, etc.) from the
internetworking layer (IPv4 and IPv6) by using public/private key internetworking layer (IPv4 and IPv6) by using public/private key
pairs, instead of IP addresses, as host identities. When a host uses pairs, instead of IP addresses, as host identities. When a host uses
HIP, the overlying protocol sublayers (e.g., transport layer sockets HIP, the overlying protocol sublayers (e.g., transport layer sockets
and Encapsulating Security Payload (ESP) Security Associations (SAs)) and Encapsulating Security Payload (ESP) Security Associations (SAs))
are instead bound to representations of these host identities, and are instead bound to representations of these host identities, and
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the HIP base exchange. the HIP base exchange.
One consequence of such a decoupling is that new solutions to One consequence of such a decoupling is that new solutions to
network-layer mobility and host multihoming are possible. Basic host network-layer mobility and host multihoming are possible. Basic host
mobility is defined in [I-D.ietf-hip-rfc5206-bis] and covers the case mobility is defined in [I-D.ietf-hip-rfc5206-bis] and covers the case
in which a host has a single address and changes its network point- in which a host has a single address and changes its network point-
of-attachment while desiring to preserve the HIP-enabled security of-attachment while desiring to preserve the HIP-enabled security
association. Host multihoming is somewhat of a dual case to host association. Host multihoming is somewhat of a dual case to host
mobility, in that a host may simultaneously have more than one mobility, in that a host may simultaneously have more than one
network point-of-attachment. There are potentially many variations network point-of-attachment. There are potentially many variations
of host multihoming possible. The scope of this document encompasses of host multihoming possible. [I-D.ietf-hip-rfc5206-bis] specifies
messaging and elements of procedure for some basic host multihoming the format of the HIP parameter (LOCATOR_SET parameter) used to
scenarios of interest. convey IP addressing information between peers, the procedures for
sending and processing this parameter to enable basic host mobility,
and procedures for an address verification mechanism. The scope of
this document encompasses messaging and elements of procedure for
some basic host multihoming scenarios of interest.
Another variation of multihoming that has been heavily studied is Another variation of multihoming that has been heavily studied is
site multihoming. Solutions for site multihoming in IPv6 networks site multihoming. Solutions for site multihoming in IPv6 networks
have been specified by the IETF shim6 working group. The shim6 have been specified by the IETF shim6 working group. The shim6
protocol [RFC5533] bears many architectural similarities to HIP but protocol [RFC5533] bears many architectural similarities to HIP but
there are differences in the security model and in the protocol. there are differences in the security model and in the protocol.
While HIP can potentially be used with transports other than the ESP While HIP can potentially be used with transports other than the ESP
transport format [RFC7402], this document largely assumes the use of transport format [RFC7402], this document largely assumes the use of
ESP and leaves other transport formats for further study. ESP and leaves other transport formats for further study.
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In host multihoming, a host has multiple locators simultaneously In host multihoming, a host has multiple locators simultaneously
rather than sequentially, as in the case of mobility. By using the rather than sequentially, as in the case of mobility. By using the
LOCATOR_SET parameter defined in [I-D.ietf-hip-rfc5206-bis], a host LOCATOR_SET parameter defined in [I-D.ietf-hip-rfc5206-bis], a host
can inform its peers of additional (multiple) locators at which it can inform its peers of additional (multiple) locators at which it
can be reached. When multiple locators are available and announced can be reached. When multiple locators are available and announced
to the peer, a host can designate a particular locator as a to the peer, a host can designate a particular locator as a
"preferred" locator, meaning that the host prefers that its peer send "preferred" locator, meaning that the host prefers that its peer send
packets to the designated address before trying an alternative packets to the designated address before trying an alternative
address. Although this document defines a basic mechanism for address. Although this document defines a basic mechanism for
multihoming, it does not define all possible policies and procedures, multihoming, it does not define all possible policies and procedures,
such as which locators to choose when more than one pair is such as which locators to choose when more than one is available, the
available, the operation of simultaneous mobility and multihoming, operation of simultaneous mobility and multihoming, source address
source address selection policies (beyond those specified in selection policies (beyond those specified in [RFC3484]), and the
[RFC3484]), and the implications of multihoming on transport implications of multihoming on transport protocols.
protocols and ESP anti-replay windows.
4. Protocol Overview 4. Protocol Overview
In this section, we briefly introduce a number of usage scenarios for In this section, we briefly introduce a number of usage scenarios for
HIP multihoming. These scenarios assume that HIP is being used with HIP multihoming. These scenarios assume that HIP is being used with
the ESP transform [RFC7402], although other scenarios may be defined the ESP transform [RFC7402], although other scenarios may be defined
in the future. To understand these usage scenarios, the reader in the future. To understand these usage scenarios, the reader
should be at least minimally familiar with the HIP protocol should be at least minimally familiar with the HIP protocol
specification [RFC7401]. However, for the (relatively) uninitiated specification [RFC7401], the use of the ESP transport format
reader, it is most important to keep in mind that in HIP the actual [RFC7402], and the HIP mobility specification
payload traffic is protected with ESP, and that the ESP SPI acts as [I-D.ietf-hip-rfc5206-bis]. However, for the (relatively)
an index to the right host-to-host context. uninitiated reader, it is most important to keep in mind that in HIP
the actual payload traffic is protected with ESP, and that the ESP
SPI acts as an index to the right host-to-host context.
The scenarios below assume that the two hosts have completed a single 4.1. Background
HIP base exchange with each other. Both of the hosts therefore have
one incoming and one outgoing SA. Further, each SA uses the same
pair of IP addresses, which are the ones used in the base exchange.
The readdressing protocol is an asymmetric protocol where a mobile or The multihoming scenarios can be explained in contrast to the non-
multihomed host informs a peer host about changes of IP addresses on multihoming case described in the base protocol specification. We
affected SPIs. The readdressing exchange is designed to be review the pertinent details here. In the base specification when
piggybacked on existing HIP exchanges. The majority of the packets used with the ESP transport format, the HIP base exchange will set up
on which the LOCATOR_SET parameters are expected to be carried are a single SA in each direction. The IP addresses associated with the
UPDATE packets. However, some implementations may want to experiment SAs are the same as those used to convey the HIP packets. For data
with sending LOCATOR_SET parameters also on other packets, such as traffic, a security policy database (SPD) and security association
R1, I2, and NOTIFY. database (SAD) will likely exist, following the IPsec architecture.
One distinction between HIP and IPsec, however, is that the host IDs,
and not the IP addresses, are conceptually used as selectors in the
SPD. In the outbound direction, as a result of SPD processing, when
an outbound SA is selected, the correct IP destination address for
the peer must also be assigned. Therefore, outbound SAs are
conceptually associated with the peer IP address that must be used as
the destination IP address below the HIP layer. In the inbound
direction, the IP addresses may be used as selectors in the SAD to
look up the SA, but they are not strictly required; the ESP SPI may
be used alone. To summarize, in the non-multihoming case, there is
only one source IP address, one destination IP address, one inbound
SA, and one outbound SA.
The scenarios below at times describe addresses as being in either an The HIP readdressing protocol [I-D.ietf-hip-rfc5206-bis] is an
ACTIVE, VERIFIED, or DEPRECATED state. From the perspective of a asymmetric protocol in which a mobile or multihomed host informs a
peer host about changes of IP addresses on affected SPIs. IP address
and ESP SPI information is carried in Locator data structures in a
HIP parameter called a LOCATOR_SET. The HIP mobility specification
[I-D.ietf-hip-rfc5206-bis] describes how the LOCATOR_SET is carried
in a HIP UPDATE packet.
To summarize the mobility elements of procedure, as background for
multihoming, the basic idea of host mobility is to communicate a
local IP address change to the peer when active HIP-maintained SAs
are in use. To do so, the IP address must be conveyed, any
association between the IP address and an inbound SA (via the SPI
index) may be conveyed, and protection against flooding attacks must
be ensured. The association of an IP address with an SPI is
performed by a Locator of type 1, which is a concatenation of an ESP
SPI with an IP address.
An address verification method is specified in
[I-D.ietf-hip-rfc5206-bis]. It is expected that addresses learned in
multihoming scenarios also are subject to the same verification
rules. The scenarios at times describe addresses as being in either
an ACTIVE, VERIFIED, or DEPRECATED state. From the perspective of a
host, newly-learned addresses of the peer must be verified before put host, newly-learned addresses of the peer must be verified before put
into active service, and addresses removed by the peer are put into a into active service, and addresses removed by the peer are put into a
deprecated state. Under limited conditions described in deprecated state. Under limited conditions described in
[I-D.ietf-hip-rfc5206-bis], an UNVERIFIED address may be used. [I-D.ietf-hip-rfc5206-bis], an UNVERIFIED address may be used.
With this background, we next describe additional protocol to
facilitate scenarios in which one or both hosts have multiple IP
addresses available. Increasingly, this is the common case with
network-connected hosts on the Internet.
4.2. Multiple Addresses
Hosts may have multiple IP addresses within different address
families (IPv4 and IPv6) and scopes available to support HIP
messaging and HIP-enabled SAs. The multiple addresses may be on a
single or multiple network interfaces. It is outside of the scope of
this document to specify how a host decides which of possibly
multiple addresses may be used to support a HIP association. Some IP
addresses may be held back from usage due to privacy, security, or
cost considerations.
When multiple IP addresses are shared with a peer, the procedures
described in the HIP mobility specification
[I-D.ietf-hip-rfc5206-bis] allow for a host to set a Preferred bit,
requesting that one of the multiple addresses be preferred for
control- or data-plane traffic. It is also permitted to leave the
Preferred bit unset for all addresses, allowing the peer to make
address selection decisions.
Hosts that use link-local addresses as source addresses in their HIP Hosts that use link-local addresses as source addresses in their HIP
handshakes may not be reachable by a mobile peer. Such hosts SHOULD handshakes may not be reachable by a mobile peer. Such hosts SHOULD
provide a globally routable address either in the initial handshake provide a globally routable address either in the initial handshake
or via the LOCATOR_SET parameter. or via the LOCATOR_SET parameter.
4.1. Host Multihoming To support mobility, as described in the HIP mobility specification
[I-D.ietf-hip-rfc5206-bis], the LOCATOR_SET may be sent in a HIP
UPDATE packet. To support multihoming, the LOCATOR_SET may also be
sent in R1, I2, or R2 packets. The reason to consider to send
LOCATOR_SET parameters in the base exchange packets is to convey all
usable addresses for fault-tolerance or load balancing
considerations.
A (mobile or stationary) host may sometimes have more than one 4.3. Multiple Security Associations
interface or global address. The host may notify the peer host of
the additional interface or address by using the LOCATOR_SET
parameter. To avoid problems with the ESP anti-replay window, a host
SHOULD use a different SA for each interface or address used to
receive packets from the peer host when multiple locator pairs are
being used simultaneously rather than sequentially.
When more than one locator is provided to the peer host, the host When multiple addresses are available between peer hosts, a question
SHOULD indicate which locator is preferred (the locator on which the that arises is whether to use one or multiple SAs. The intent of
host prefers to receive traffic). By default, the addresses used in this specification is to support different use cases but to leave the
the base exchange are preferred until indicated otherwise. policy decision to the hosts.
When one host has n addresses and the other host has m addresses, it
is possible to set up as many as (n * m) SAs in each direction. In
such a case, every combination of source and destination IP address
would have a unique SA, and the possibility of reordering of
datagrams on each SA will be lessened (ESP SAs may have an anti-
replay window sensitive to reordering). However, the downside to
creating a mesh of SAs is the signaling overhead required (for
exchanging UPDATE messages conveying ESP_INFO parameters) and the
state maintenance required in the SPD/SAD.
For load balancing, when multiple paths are to be used in parallel,
it may make sense to create different SAs for different paths. In
this use case, while a full mesh of 2 * (n * m) SAs may not be
required, it may be beneficial to create one SA pair per load-
balanced path to avoid anti-replay window issues.
For fault tolerance, it is more likely that a single SA can be used
and multiple IP addresses associated with that SA, and the
alternative addresses used only upon failure detection of the
addresses in use. Techniques for path failure detection are outside
the scope of this specification. An implementation may use ICMP
interactions, reachability checks, or other means to detect the
failure of a locator.
In summary, whether and how a host decides to leverage additional
addresses in a load-balancing or fault-tolerant manner is outside the
scope of the specification. However, in general, this document
recommends that for fault tolerance, it is likely sufficient to use a
single SA pair for all addresses, and for load balancing, to support
a different SA pair for all active paths being balanced across.
4.4. Host Multihoming for Fault Tolerance
A (mobile or stationary) host may have more than one interface or
global address. The host may choose to notify the peer host of the
additional interface or address by using the LOCATOR_SET parameter.
The LOCATOR_SET parameter may be included in an I2, R1, or R2 packet,
or may be conveyed, after the base exchange completes in an UPDATE
packet.
When more than one locator is provided to the peer host, the host MAY
indicate which locator is preferred (the locator on which the host
prefers to receive traffic). By default, the addresses used in the
base exchange are preferred until indicated otherwise. It may be the
case that the host does not express any preferred locators.
In the multihoming case, the sender may also have multiple valid In the multihoming case, the sender may also have multiple valid
locators from which to source traffic. In practice, a HIP locators from which to source traffic. In practice, a HIP
association in a multihoming configuration may have both a preferred association in a multihoming configuration may have both a preferred
peer locator and a preferred local locator, although rules for source peer locator and a preferred local locator, although rules for source
address selection should ultimately govern the selection of the address selection should ultimately govern the selection of the
source locator based on the destination locator. source locator based on the destination locator.
Although the protocol may allow for configurations in which there is Although the protocol may allow for configurations in which there is
an asymmetric number of SAs between the hosts (e.g., one host has two an asymmetric number of SAs between the hosts (e.g., one host has two
interfaces and two inbound SAs, while the peer has one interface and interfaces and two inbound SAs, while the peer has one interface and
one inbound SA), it is RECOMMENDED that inbound and outbound SAs be one inbound SA), it is RECOMMENDED that inbound and outbound SAs be
created pairwise between hosts. When an ESP_INFO arrives to rekey a created pairwise between hosts. When an ESP_INFO arrives to rekey a
particular outbound SA, the corresponding inbound SA should be also particular outbound SA, the corresponding inbound SA should be also
rekeyed at that time. Although asymmetric SA configurations might be rekeyed at that time.
experimented with, their usage may constrain interoperability at this
time. However, it is recommended that implementations attempt to
support peers that prefer to use non-paired SAs.
Consider the case between two hosts, one single-homed and one Consider the case of two hosts, one single-homed and one multihomed.
multihomed. The multihomed host may decide to inform the single- The multihomed host may decide to inform the single-homed host about
homed host about its other address. It is RECOMMENDED that the its other address(es). It may choose to do so as follows.
multihomed host set up a new SA pair for use on this new address. To
do this, the multihomed host sends a LOCATOR_SET with an ESP_INFO, If the multihomed host wishes to convey the additional address(es)
indicating the request for a new SA by setting the OLD SPI value to for fault tolerance, it should include all of its addresses in
zero, and the NEW SPI value to the newly created incoming SPI. A Locator records, indicating the Traffic Type, Locator Type, and
Locator Type of "1" is used to associate the new address with the new Preferred Locator for each address. If it wishes to bind any
SPI. The LOCATOR_SET parameter also contains a second Type "1" particular address to an existing SPI, it may do so by using a
locator, that of the original address and SPI. To simplify parameter Locator of Type 1 as specified in the HIP mobility specification
processing and avoid explicit protocol extensions to remove locators, [I-D.ietf-hip-rfc5206-bis]. It does not need to rekey the existing
each LOCATOR_SET parameter MUST list all locators in use on a SA or request additional SAs at this time.
connection (a complete listing of inbound locators and SPIs for the
host). The multihomed host waits for an ESP_INFO (new outbound SA) Figure 1 illustrates this scenario.
from the peer and an ACK of its own UPDATE. As in the mobility case,
the peer host must perform an address verification before actively Multi-homed Host Peer Host
using the new address. Figure 1 illustrates this scenario.
UPDATE(LOCATOR_SET, SEQ)
----------------------------------->
UPDATE(ACK)
<-----------------------------------
Figure 1: Basic Multihoming Scenario
In this scenario, the peer host associates the multiple addresses
with the SA pair between it and the multihomed host. It may also
undergo address verification procedures to transition the addresses
to ACTIVE statte. For inbound data traffic, it may choose to use the
addresses along with the SPI as selectors. For outbound data
traffic, it must choose among the available addresses of the
multihomed host, considering the state of address verification
[I-D.ietf-hip-rfc5206-bis] of each address, and also considering
available information about whether an address is in a working state.
4.5. Host Multihoming for Load Balancing
A multihomed host may decide to set up new SA pairs corresponding to
new addresses, for the purpose of load balancing. The decision to
load balance and the mechanism for splitting load across multiple SAs
is out of scope of this document. The scenario can be supported by
sending the LOCATOR_SET parameter with one or more ESP_INFO
parameters to initiate new ESP SAs. To do this, the multihomed host
sends a LOCATOR_SET with an ESP_INFO, indicating the request for a
new SA by setting the OLD SPI value to zero, and the NEW SPI value to
the newly created incoming SPI. A Locator Type of "1" is used to
associate the new address with the new SPI. The LOCATOR_SET
parameter also contains a second Type "1" locator, that of the
original address and SPI. To simplify parameter processing and avoid
explicit protocol extensions to remove locators, each LOCATOR_SET
parameter MUST list all locators in use on a connection (a complete
listing of inbound locators and SPIs for the host). The multihomed
host waits for a corresponding ESP_INFO (new outbound SA) from the
peer and an ACK of its own UPDATE. As in the mobility case, the peer
host must perform an address verification before actively using the
new address.
Figure 2 illustrates this scenario.
Multi-homed Host Peer Host Multi-homed Host Peer Host
UPDATE(ESP_INFO, LOCATOR_SET, SEQ, [DIFFIE_HELLMAN]) UPDATE(ESP_INFO, LOCATOR_SET, SEQ, [DIFFIE_HELLMAN])
-----------------------------------> ----------------------------------->
UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_REQUEST) UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_REQUEST)
<----------------------------------- <-----------------------------------
UPDATE(ACK, ECHO_RESPONSE) UPDATE(ACK, ECHO_RESPONSE)
-----------------------------------> ----------------------------------->
Figure 1: Basic Multihoming Scenario Figure 2: Host Multihoming for Load Balancing
In multihoming scenarios, it is important that hosts receiving In multihoming scenarios, it is important that hosts receiving
UPDATEs associate them correctly with the destination address used in UPDATEs associate them correctly with the destination address used in
the packet carrying the UPDATE. When processing inbound LOCATOR_SETs the packet carrying the UPDATE. When processing inbound LOCATOR_SETs
that establish new security associations on an interface with that establish new security associations on an interface with
multiple addresses, a host uses the destination address of the UPDATE multiple addresses, a host uses the destination address of the UPDATE
containing the LOCATOR_SET as the local address to which the containing the LOCATOR_SET as the local address to which the
LOCATOR_SET plus ESP_INFO is targeted. This is because hosts may LOCATOR_SET plus ESP_INFO is targeted. This is because hosts may
send UPDATEs with the same (locator) IP address to different peer send UPDATEs with the same (locator) IP address to different peer
addresses -- this has the effect of creating multiple inbound SAs addresses -- this has the effect of creating multiple inbound SAs
implicitly affiliated with different peer source addresses. implicitly affiliated with different peer source addresses.
4.2. Site Multihoming 4.6. Site Multihoming
A host may have an interface that has multiple globally routable IP A host may have an interface that has multiple globally routable IP
addresses. Such a situation may be a result of the site having addresses. Such a situation may be a result of the site having
multiple upper Internet Service Providers, or just because the site multiple upper Internet Service Providers, or just because the site
provides all hosts with both IPv4 and IPv6 addresses. The host provides all hosts with both IPv4 and IPv6 addresses. The host
should stay reachable at all or any subset of the currently available should stay reachable at all or any subset of the currently available
global routable addresses, independent of how they are provided. global routable addresses, independent of how they are provided.
This case is handled the same as if there were different IP This case is handled the same as if there were different IP
addresses, described above in Section 4.1. Note that a single addresses, described above in Section 4.4 and Section 4.5. Note that
interface may experience site multihoming while the host itself may a single interface may have addresses corresponding to site
have multiple interfaces. multihoming while the host itself may also have multiple network
interfaces.
Note that a host may be multihomed and mobile simultaneously, and Note that a host may be multihomed and mobile simultaneously, and
that a multihomed host may want to protect the location of some of that a multihomed host may want to protect the location of some of
its interfaces while revealing the real IP address of some others. its interfaces while revealing the real IP address of some others.
This document does not presently additional site multihoming This document does not presently additional site multihoming
extensions to HIP; such extensions are for further study. extensions to HIP; such extensions are for further study.
4.3. Dual host multihoming 4.7. Dual Host Multihoming
Consider the case in which both hosts would like to add an additional Consider the case in which both hosts are multihomed and would like
address after the base exchange completes. In Figure 2, consider to notify the peer of an additional address after the base exchange
that host1, which used address addr1a in the base exchange to set up completes. It may be the case that both hosts choose to simply
SPI1a and SPI2a, wants to add address addr1b. It would send an announce the second address in a LOCATOR_SET parameter using an
UPDATE with LOCATOR_SET (containing the address addr1b) to host2, UPDATE message exchange. It may also be the case that one or both
using destination address addr2a, and a new set of SPIs would be hosts decide to ask for new SA pairs to be created using the newly
added between hosts 1 and 2 (call them SPI1b and SPI2b -- not shown announced address. In the case that both hosts request this, the
in the figure). Next, consider host2 deciding to add addr2b to the result will be a full mesh of SAs as depicted in Figure 3. In such a
relationship. Host2 must select one of host1's addresses towards scenario, consider that host1, which used address addr1a in the base
which to initiate an UPDATE. It may choose to initiate an UPDATE to exchange to set up SPI1a and SPI2a, wants to add address addr1b. It
addr1a, addr1b, or both. If it chooses to send to both, then a full would send an UPDATE with LOCATOR_SET (containing the address addr1b)
mesh (four SA pairs) of SAs would exist between the two hosts. This to host2, using destination address addr2a, and a new ESP_INFO, and a
is the most general case; it often may be the case that hosts new set of SPIs would be added between hosts 1 and 2 (call them SPI1b
primarily establish new SAs only with the peer's Preferred locator. and SPI2b; not shown in the figure). Next, consider host2 deciding
The readdressing protocol is flexible enough to accommodate this to add addr2b to the relationship. Host2 must select one of host1's
choice. addresses towards which to initiate an UPDATE. It may choose to
initiate an UPDATE to addr1a, addr1b, or both. If it chooses to send
to both, then a full mesh (four SA pairs) of SAs would exist between
the two hosts. This is the most general case; the protocol is
flexible enough to accommodate this choice.
-<- SPI1a -- -- SPI2a ->- -<- SPI1a -- -- SPI2a ->-
host1 < > addr1a <---> addr2a < > host2 host1 < > addr1a <---> addr2a < > host2
->- SPI2a -- -- SPI1a -<- ->- SPI2a -- -- SPI1a -<-
addr1b <---> addr2a (second SA pair) addr1b <---> addr2a (second SA pair)
addr1a <---> addr2b (third SA pair) addr1a <---> addr2b (third SA pair)
addr1b <---> addr2b (fourth SA pair) addr1b <---> addr2b (fourth SA pair)
Figure 2: Dual Multihoming Case in Which Each Host Uses LOCATOR_SET Figure 3: Dual Multihoming Case in Which Each Host Uses LOCATOR_SET
to Add a Second Address to Add a Second Address
4.4. Combined Mobility and Multihoming 4.8. Combined Mobility and Multihoming
It looks likely that in the future, many mobile hosts will be It looks likely that in the future, many mobile hosts will be
simultaneously mobile and multihomed, i.e., have multiple mobile simultaneously mobile and multihomed, i.e., have multiple mobile
interfaces. Furthermore, if the interfaces use different access interfaces. Furthermore, if the interfaces use different access
technologies, it is fairly likely that one of the interfaces may technologies, it is fairly likely that one of the interfaces may
appear stable (retain its current IP address) while some other(s) may appear stable (retain its current IP address) while some other(s) may
experience mobility (undergo IP address change). experience mobility (undergo IP address change).
The use of LOCATOR_SET plus ESP_INFO should be flexible enough to The use of LOCATOR_SET plus ESP_INFO should be flexible enough to
handle most such scenarios, although more complicated scenarios have handle most such scenarios, although more complicated scenarios have
not been studied so far. not been studied so far.
4.5. Initiating the Protocol in R1 or I2 4.9. Initiating the Protocol in R1, I2, or R2
A Responder host MAY include a LOCATOR_SET parameter in the R1 packet A Responder host MAY include a LOCATOR_SET parameter in the R1 packet
that it sends to the Initiator. This parameter MUST be protected by that it sends to the Initiator. This parameter MUST be protected by
the R1 signature. If the R1 packet contains LOCATOR_SET parameters the R1 signature. If the R1 packet contains LOCATOR_SET parameters
with a new Preferred locator, the Initiator SHOULD directly set the with a new Preferred locator, the Initiator SHOULD directly set the
new Preferred locator to status ACTIVE without performing address new Preferred locator to status ACTIVE without performing address
verification first, and MUST send the I2 packet to the new Preferred verification first, and MUST send the I2 packet to the new Preferred
locator. The I1 destination address and the new Preferred locator locator. The I1 destination address and the new Preferred locator
may be identical. All new non-preferred locators must still undergo may be identical. All new non-preferred locators must still undergo
address verification once the base exchange completes. address verification once the base exchange completes. It is also
possible for the host to send the LOCATOR_SET without any Preferred
bits set, in which case the exchange will continue as normal and the
newly-learned addresses will be in an UNVERIFIED state at the
initiator.
Initiator Responder Initiator Responder
R1 with LOCATOR_SET R1 with LOCATOR_SET
<----------------------------------- <-----------------------------------
record additional addresses record additional addresses
change responder address change responder address
I2 sent to newly indicated preferred address I2 sent to newly indicated preferred address
-----------------------------------> ----------------------------------->
(process normally) (process normally)
R2 R2
<----------------------------------- <-----------------------------------
(process normally, later verification of non-preferred locators) (process normally, later verification of non-preferred locators)
Figure 3: LOCATOR_SET Inclusion in R1 Figure 4: LOCATOR_SET Inclusion in R1
An Initiator MAY include one or more LOCATOR_SET parameters in the I2 An Initiator MAY include one or more LOCATOR_SET parameters in the I2
packet, independent of whether or not there was a LOCATOR_SET packet, independent of whether or not there was a LOCATOR_SET
parameter in the R1. These parameters MUST be protected by the I2 parameter in the R1. These parameters MUST be protected by the I2
signature. Even if the I2 packet contains LOCATOR_SET parameters, signature. Even if the I2 packet contains LOCATOR_SET parameters,
the Responder MUST still send the R2 packet to the source address of the Responder MUST still send the R2 packet to the source address of
the I2. The new Preferred locator SHOULD be identical to the I2 the I2. The new Preferred locator, if set, SHOULD be identical to
source address. If the I2 packet contains LOCATOR_SET parameters, the I2 source address. If the I2 packet contains LOCATOR_SET
all new locators must undergo address verification as usual, and the parameters, all new locators must undergo address verification as
ESP traffic that subsequently follows should use the Preferred usual, and the ESP traffic that subsequently follows should use the
locator. Preferred locator.
Initiator Responder Initiator Responder
I2 with LOCATOR_SET I2 with LOCATOR_SET
-----------------------------------> ----------------------------------->
(process normally) (process normally)
record additional addresses record additional addresses
R2 sent to source address of I2 R2 sent to source address of I2
<----------------------------------- <-----------------------------------
(process normally) (process normally)
Figure 4: LOCATOR_SET Inclusion in I2 Figure 5: LOCATOR_SET Inclusion in I2
The I1 and I2 may be arriving from different source addresses if the The I1 and I2 may be arriving from different source addresses if the
LOCATOR_SET parameter is present in R1. In this case, LOCATOR_SET parameter is present in R1. In this case,
implementations simultaneously using multiple pre-created R1s, implementations simultaneously using multiple pre-created R1s,
indexed by Initiator IP addresses, may inadvertently fail the puzzle indexed by Initiator IP addresses, may inadvertently fail the puzzle
solution of I2 packets due to a perceived puzzle mismatch. See, for solution of I2 packets due to a perceived puzzle mismatch. See, for
instance, the example in Appendix A of [RFC7401]. As a solution, the instance, the example in Appendix A of [RFC7401]. As a solution, the
Responder's puzzle indexing mechanism must be flexible enough to Responder's puzzle indexing mechanism must be flexible enough to
accommodate the situation when R1 includes a LOCATOR_SET parameter. accommodate the situation when R1 includes a LOCATOR_SET parameter.
4.6. Using LOCATOR_SETs across Addressing Realms Finally, the R2 may be used to carry the LOCATOR_SET parameter. In
this case, the LOCATOR_SET is covered by the HIP_MAC_2 and
It is possible for HIP associations to migrate to a state in which HIP_SIGNATURE. Including LOCATOR_SET in R2 as opposed to R1 may have
both parties are only using locators in different addressing realms. some advantages when a host prefers not to divulge additional
For example, the two hosts may initiate the HIP association when both locators until after the I2 is successfully processed.
are using IPv6 locators, then one host may loose its IPv6
connectivity and obtain an IPv4 address. In such a case, some type
of mechanism for interworking between the different realms must be
employed; such techniques are outside the scope of the present text.
The basic problem in this example is that the host readdressing to
IPv4 does not know a corresponding IPv4 address of the peer. This
may be handled (experimentally) by possibly configuring this address
information manually or in the DNS, or the hosts exchange both IPv4
and IPv6 addresses in the locator.
5. Other Considerations
5.1. Address Verification
An address verification method is specified in
[I-D.ietf-hip-rfc5206-bis]. It is expected that addresses learned in
multihoming scenarios also are subject to the same verification
rules.
5.2. Preferred Locator
When a host has multiple locators, the peer host must decide which to
use for outbound packets. It may be that a host would prefer to
receive data on a particular inbound interface. HIP allows a
particular locator to be designated as a Preferred locator and
communicated to the peer.
In general, when multiple locators are used for a session, there is
the question of using multiple locators for failover only or for
load-balancing. Due to the implications of load-balancing on the
transport layer that still need to be worked out, this document
assumes that multiple locators are used primarily for failover. An
implementation may use ICMP interactions, reachability checks, or
other means to detect the failure of a locator.
5.3. Interaction with Security Associations
This document uses the HIP LOCATOR_SET protocol parameter, specified
in [I-D.ietf-hip-rfc5206-bis]), that allows the hosts to exchange
information about their locator(s) and any changes in their
locator(s). The logical structure created with LOCATOR_SET
parameters has three levels: hosts, Security Associations (SAs)
indexed by Security Parameter Indices (SPIs), and addresses.
The relation between these levels for an association constructed as
defined in the base specification [RFC7401] and ESP transform
[RFC7402] is illustrated in Figure 5.
-<- SPI1a -- -- SPI2a ->-
host1 < > addr1a <---> addr2a < > host2
->- SPI2a -- -- SPI1a -<-
Figure 5: Relation between Hosts, SPIs, and Addresses (Base
Specification)
In Figure 5, host1 and host2 negotiate two unidirectional SAs, and When the LOCATOR_SET parameter is sent in an UPDATE packet, then the
each host selects the SPI value for its inbound SA. The addresses receiver will respond with an UPDATE acknowledgment. When the
addr1a and addr2a are the source addresses that the hosts use in the LOCATOR_SET parameter is sent in an R1, I2, or R2 packet, the base
base HIP exchange. These are the "preferred" (and only) addresses exchange retransmission mechanism will confirm its successful
conveyed to the peer for use on each SA. That is, although packets delivery.
sent to any of the hosts' interfaces may be accepted on the inbound
SA, the peer host in general knows of only the single destination
address learned in the base exchange (e.g., for host1, it sends a
packet on SPI2a to addr2a to reach host2), unless other mechanisms
exist to learn of new addresses.
In general, the bindings that exist in an implementation 4.10. Using LOCATOR_SETs across Addressing Realms
corresponding to this document can be depicted as shown in Figure 6.
In this figure, a host can have multiple inbound SPIs (and, not
shown, multiple outbound SPIs) associated with another host.
Furthermore, each SPI may have multiple addresses associated with it.
These addresses that are bound to an SPI are not used to lookup the
incoming SA. Rather, the addresses are those that are provided to
the peer host, as hints for which addresses to use to reach the host
on that SPI. The LOCATOR_SET parameter is used to change the set of
addresses that a peer associates with a particular SPI.
address11 It is possible for HIP associations to use these mechanisms to
/ migrate their HIP associations and security associations from
SPI1 - address12 addresses in the IPv4 addressing realm to IPv6 or vice versa. It may
/ be possible for a state to arise in which both hosts are only using
/ address21 locators in different addressing realms, but in such a case, some
host -- SPI2 < type of mechanism for interworking between the different realms must
\ address22 be employed; such techniques are outside the scope of the present
\ text.
SPI3 - address31
\
address32
Figure 6: Relation between Hosts, SPIs, and Addresses (General Case) 4.11. Interaction with Security Associations
A host may establish any number of security associations (or SPIs) A host may establish any number of security associations (or SPIs)
with a peer. The main purpose of having multiple SPIs with a peer is with a peer. The main purpose of having multiple SPIs with a peer is
to group the addresses into collections that are likely to experience to group the addresses into collections that are likely to experience
fate sharing. For example, if the host needs to change its addresses fate sharing, or to perform load balancing.
on SPI2, it is likely that both address21 and address22 will
simultaneously become obsolete. In a typical case, such SPIs may
correspond with physical interfaces; see below. Note, however, that
especially in the case of site multihoming, one of the addresses may
become unreachable while the other one still works. In the typical
case, however, this does not require the host to inform its peers
about the situation, since even the non-working address still
logically exists.
A basic property of HIP SAs is that the inbound IP address is not A basic property of HIP SAs is that the inbound IP address is not
used to lookup the incoming SA. Therefore, in Figure 6, it may seem used to lookup the incoming SA. However, the use of different source
unnecessary for address31, for example, to be associated only with and destination addresses typically leads to different paths, with
SPI3 -- in practice, a packet may arrive to SPI1 via destination
address address31 as well. However, the use of different source and
destination addresses typically leads to different paths, with
different latencies in the network, and if packets were to arrive via different latencies in the network, and if packets were to arrive via
an arbitrary destination IP address (or path) for a given SPI, the an arbitrary destination IP address (or path) for a given SPI, the
reordering due to different latencies may cause some packets to fall reordering due to different latencies may cause some packets to fall
outside of the ESP anti-replay window. For this reason, HIP provides outside of the ESP anti-replay window. For this reason, HIP provides
a mechanism to affiliate destination addresses with inbound SPIs, a mechanism to affiliate destination addresses with inbound SPIs,
when there is a concern that anti-replay windows might be violated. when there is a concern that anti-replay windows might be violated.
In this sense, we can say that a given inbound SPI has an "affinity" In this sense, we can say that a given inbound SPI has an "affinity"
for certain inbound IP addresses, and this affinity is communicated for certain inbound IP addresses, and this affinity is communicated
to the peer host. Each physical interface SHOULD have a separate SA, to the peer host. Each physical interface SHOULD have a separate SA,
unless the ESP anti-replay window is loose. unless the ESP anti-replay window is extended or disabled.
Moreover, even when the destination addresses used for a particular Moreover, even when the destination addresses used for a particular
SPI are held constant, the use of different source interfaces may SPI are held constant, the use of different source interfaces may
also cause packets to fall outside of the ESP anti-replay window, also cause packets to fall outside of the ESP anti-replay window,
since the path traversed is often affected by the source address or since the path traversed is often affected by the source address or
interface used. A host has no way to influence the source interface interface used. A host has no way to influence the source interface
on which a peer sends its packets on a given SPI. A host SHOULD on which a peer sends its packets on a given SPI. A host SHOULD
consistently use the same source interface and address when sending consistently use the same source interface and address when sending
to a particular destination IP address and SPI. For this reason, a to a particular destination IP address and SPI. For this reason, a
host may find it useful to change its SPI or at least reset its ESP host may find it useful to change its SPI or at least reset its ESP
anti-replay window when the peer host readdresses. anti-replay window when the peer host readdresses.
An address may appear on more than one SPI. This creates no 5. Processing Rules
ambiguity since the receiver will ignore the IP addresses during SA
lookup anyway. However, this document does not specify such cases.
When the LOCATOR_SET parameter is sent in an UPDATE packet, then the
receiver will respond with an UPDATE acknowledgment. When the
LOCATOR_SET parameter is sent in an R1 or I2 packet, the base
exchange retransmission mechanism will confirm its successful
delivery. LOCATOR_SETs may experimentally be used in NOTIFY packets;
in this case, the recipient MUST consider the LOCATOR_SET as
informational and not immediately change the current preferred
address, but can test the additional locators when the need arises.
The use of the LOCATOR_SET in a NOTIFY message may not be compatible
with middleboxes.
6. Processing Rules
Basic processing rules for the LOCATOR_SET parameter are specified in Basic processing rules for the LOCATOR_SET parameter are specified in
[I-D.ietf-hip-rfc5206-bis]. This document focuses on multihoming- [I-D.ietf-hip-rfc5206-bis]. This document focuses on multihoming-
specific rules. specific rules.
6.1. Sending LOCATOR_SETs 5.1. Sending LOCATOR_SETs
The decision of when to send a LOCATOR_SET, and which addresses to The decision of when to send a LOCATOR_SET, and which addresses to
include, is a local policy issue. [I-D.ietf-hip-rfc5206-bis] include, is a local policy issue. [I-D.ietf-hip-rfc5206-bis]
recommends that a host send a LOCATOR_SET whenever it recognizes a recommends that a host send a LOCATOR_SET whenever it recognizes a
change of its IP addresses in use on an active HIP association, and change of its IP addresses in use on an active HIP association, and
assumes that the change is going to last at least for a few seconds. assumes that the change is going to last at least for a few seconds.
It is possible to delay the exposure of additional locators to the It is possible to delay the exposure of additional locators to the
peer, and to send data from previously unannounced locators, as might peer, and to send data from previously unannounced locators, as might
arise in certain mobility or multihoming situations. arise in certain mobility or multihoming situations.
When a host decides to inform its peers about changes in its IP When a host decides to inform its peers about changes in its IP
addresses, it has to decide how to group the various addresses with addresses, it has to decide how to group the various addresses with
SPIs. The grouping should consider also whether middlebox SPIs. The grouping should consider also whether middlebox
interaction requires sending the same LOCATOR_SET in separate UPDATEs interaction requires sending the same LOCATOR_SET in separate UPDATEs
on different paths. Since each SPI is associated with a different on different paths. Since each SPI is associated with a different
Security Association, the grouping policy may also be based on ESP Security Association, the grouping policy may also be based on ESP
skipping to change at page 13, line 38 skipping to change at page 14, line 40
are known to be neighbors on the same link, such as when the IP are known to be neighbors on the same link, such as when the IP
destination address of a peer is also link-local. The announcement destination address of a peer is also link-local. The announcement
of link-local addresses in this case is a policy decision; link-local of link-local addresses in this case is a policy decision; link-local
addresses used as Preferred locators will create reachability addresses used as Preferred locators will create reachability
problems when the host moves to another link. In any case, link- problems when the host moves to another link. In any case, link-
local addresses MUST NOT be announced to a peer unless that peer is local addresses MUST NOT be announced to a peer unless that peer is
known to be on the same link. known to be on the same link.
Once the host has decided on the groups and assignment of addresses Once the host has decided on the groups and assignment of addresses
to the SPIs, it creates a LOCATOR_SET parameter that serves as a to the SPIs, it creates a LOCATOR_SET parameter that serves as a
complete representation of the addresses and affiliated SPIs intended complete representation of the addresses and associated SPIs intended
for active use. We now describe a few cases introduced in Section 4. for active use. We now describe a few cases introduced in Section 4.
We assume that the Traffic Type for each locator is set to "0" (other We assume that the Traffic Type for each locator is set to "0" (other
values for Traffic Type may be specified in documents that separate values for Traffic Type may be specified in documents that separate
the HIP control plane from data plane traffic). Other mobility and the HIP control plane from data plane traffic). Other mobility and
multihoming cases are possible but are left for further multihoming cases are possible but are left for further
experimentation. experimentation.
1. Host multihoming (addition of an address). We only describe the 1. Host multihoming (addition of an address). We only describe the
simple case of adding an additional address to a (previously) simple case of adding an additional address to a (previously)
single-homed, non-mobile host. The host SHOULD set up a new SA single-homed, non-mobile host. The host MAY choose to simply
pair between this new address and the preferred address of the announce this address to the peer, for fault tolerance. To do
peer host. To do this, the multihomed host creates a new inbound this, the multihomed host creates a LOCATOR_SET parameter
SA and creates a new SPI. For the outgoing UPDATE message, it including the existing address and SPI as a Type "1" Locator, and
inserts an ESP_INFO parameter with an OLD SPI field of "0", a NEW the new address as a Type "0" Locator. The host sends this in an
SPI field corresponding to the new SPI, and a KEYMAT Index as UPDATE message with SEQ parameter, which is acknowledged by the
selected by local policy. The host adds to the UPDATE message a peer.
LOCATOR_SET with two Type "1" Locators: the original address and
SPI active on the association, and the new address and new SPI 2. The host MAY set up a new SA pair between this new address and an
being added (with the SPI matching the NEW SPI contained in the address of the peer host. To do this, the multihomed host
ESP_INFO). The Preferred bit SHOULD be set depending on the creates a new inbound SA and creates a new SPI. For the outgoing
policy to tell the peer host which of the two locators is UPDATE message, it inserts an ESP_INFO parameter with an OLD SPI
preferred. The UPDATE also contains a SEQ parameter and field of "0", a NEW SPI field corresponding to the new SPI, and a
optionally a DIFFIE_HELLMAN parameter, and follows rekeying KEYMAT Index as selected by local policy. The host adds to the
UPDATE message a LOCATOR_SET with two Type "1" Locators: the
original address and SPI active on the association, and the new
address and new SPI being added (with the SPI matching the NEW
SPI contained in the ESP_INFO). The Preferred bit SHOULD be set
depending on the policy to tell the peer host which of the two
locators is preferred. The UPDATE also contains a SEQ parameter
and optionally a DIFFIE_HELLMAN parameter, and follows rekeying
procedures with respect to this new address. The UPDATE message procedures with respect to this new address. The UPDATE message
SHOULD be sent to the peer's Preferred address with a source SHOULD be sent to the peer's Preferred address with a source
address corresponding to the new locator. address corresponding to the new locator.
The sending of multiple LOCATOR_SETs, locators with Locator Type "0", The sending of multiple LOCATOR_SETs is unsupported. Note that the
and multiple ESP_INFO parameters is for further study. Note that the
inclusion of LOCATOR_SET in an R1 packet requires the use of Type "0" inclusion of LOCATOR_SET in an R1 packet requires the use of Type "0"
locators since no SAs are set up at that point. locators since no SAs are set up at that point.
6.2. Handling Received LOCATOR_SETs 5.2. Handling Received LOCATOR_SETs
A host SHOULD be prepared to receive a LOCATOR_SET parameter in the A host SHOULD be prepared to receive a LOCATOR_SET parameter in the
following HIP packets: R1, I2, UPDATE, and NOTIFY. following HIP packets: R1, I2, R2, and UPDATE.
This document describes sending both ESP_INFO and LOCATOR_SET This document describes sending both ESP_INFO and LOCATOR_SET
parameters in an UPDATE. The ESP_INFO parameter is included when parameters in an UPDATE. The ESP_INFO parameter is included when
there is a need to rekey or key a new SPI, and is otherwise included there is a need to rekey or key a new SPI, and can otherwise be
for the possible benefit of HIP-aware middleboxes. The LOCATOR_SET included for the possible benefit of HIP-aware middleboxes. The
parameter contains a complete map of the locators that the host LOCATOR_SET parameter contains a complete map of the locators that
wishes to make or keep active for the HIP association. the host wishes to make or keep active for the HIP association.
In general, the processing of a LOCATOR_SET depends upon the packet In general, the processing of a LOCATOR_SET depends upon the packet
type in which it is included. Here, we describe only the case in type in which it is included. Here, we describe only the case in
which ESP_INFO is present and a single LOCATOR_SET and ESP_INFO are which ESP_INFO is present and a single LOCATOR_SET and ESP_INFO are
sent in an UPDATE message; other cases are for further study. The sent in an UPDATE message; other cases are for further study. The
steps below cover each of the cases described in Section 6.1. steps below cover each of the cases described in Section 5.1.
The processing of ESP_INFO and LOCATOR_SET parameters is intended to The processing of ESP_INFO and LOCATOR_SET parameters is intended to
be modular and support future generalization to the inclusion of be modular and support future generalization to the inclusion of
multiple ESP_INFO and/or multiple LOCATOR_SET parameters. A host multiple ESP_INFO and/or multiple LOCATOR_SET parameters. A host
SHOULD first process the ESP_INFO before the LOCATOR_SET, since the SHOULD first process the ESP_INFO before the LOCATOR_SET, since the
ESP_INFO may contain a new SPI value mapped to an existing SPI, while ESP_INFO may contain a new SPI value mapped to an existing SPI, while
a Type "1" locator will only contain a reference to the new SPI. a Type "1" locator will only contain a reference to the new SPI.
When a host receives a validated HIP UPDATE with a LOCATOR_SET and When a host receives a validated HIP UPDATE with a LOCATOR_SET and
ESP_INFO parameter, it processes the ESP_INFO as follows. The ESP_INFO parameter, it processes the ESP_INFO as follows. The
skipping to change at page 15, line 38 skipping to change at page 16, line 45
If none of the above cases apply, a protocol error has occurred and If none of the above cases apply, a protocol error has occurred and
the processing of the UPDATE is stopped. the processing of the UPDATE is stopped.
Next, the locators in the LOCATOR_SET parameter are processed. For Next, the locators in the LOCATOR_SET parameter are processed. For
each locator listed in the LOCATOR_SET parameter, check that the each locator listed in the LOCATOR_SET parameter, check that the
address therein is a legal unicast or anycast address. That is, the address therein is a legal unicast or anycast address. That is, the
address MUST NOT be a broadcast or multicast address. Note that some address MUST NOT be a broadcast or multicast address. Note that some
implementations MAY accept addresses that indicate the local host, implementations MAY accept addresses that indicate the local host,
since it may be allowed that the host runs HIP with itself. since it may be allowed that the host runs HIP with itself.
The below assumes that all locators are of Type "1" with a Traffic
Type of "0"; other cases are for further study.
For each Type "1" address listed in the LOCATOR_SET parameter, the For each Type "1" address listed in the LOCATOR_SET parameter, the
host checks whether the address is already bound to the SPI host checks whether the address is already bound to the SPI
indicated. If the address is already bound, its lifetime is updated. indicated. If the address is already bound, its lifetime is updated.
If the status of the address is DEPRECATED, the status is changed to If the status of the address is DEPRECATED, the status is changed to
UNVERIFIED. If the address is not already bound, the address is UNVERIFIED. If the address is not already bound, the address is
added, and its status is set to UNVERIFIED. Mark all addresses added, and its status is set to UNVERIFIED. Mark all addresses
corresponding to the SPI that were NOT listed in the LOCATOR_SET corresponding to the SPI that were NOT listed in the LOCATOR_SET
parameter as DEPRECATED. parameter as DEPRECATED.
For each Type "0" address listed in the LOCATOR_SET parameter, if the
status of the address is DEPRECATED, or the address was not
previously known, the status is changed to UNVERIFIED. The host MAY
choose to associate this address with one or more SAs. The
association with different SAs is a local policy decision, unless the
peer has indicated that the address is Preferred, in which case the
address should be put into use on a SA that is prioritized in the
security policy database.
As a result, at the end of processing, the addresses listed in the As a result, at the end of processing, the addresses listed in the
LOCATOR_SET parameter have either a state of UNVERIFIED or ACTIVE, LOCATOR_SET parameter have either a state of UNVERIFIED or ACTIVE,
and any old addresses on the old SA not listed in the LOCATOR_SET and any old addresses on the old SA not listed in the LOCATOR_SET
parameter have a state of DEPRECATED. parameter have a state of DEPRECATED.
Once the host has processed the locators, if the LOCATOR_SET Once the host has processed the locators, if the LOCATOR_SET
parameter contains a new Preferred locator, the host SHOULD initiate parameter contains a new Preferred locator, the host SHOULD initiate
a change of the Preferred locator. This requires that the host first a change of the Preferred locator. This requires that the host first
verifies reachability of the associated address, and only then verifies reachability of the associated address, and only then
changes the Preferred locator; see Section 6.4. changes the Preferred locator; see Section 5.4.
If a host receives a locator with an unsupported Locator Type, and If a host receives a locator with an unsupported Locator Type, and
when such a locator is also declared to be the Preferred locator for when such a locator is also declared to be the Preferred locator for
the peer, the host SHOULD send a NOTIFY error with a Notify Message the peer, the host SHOULD send a NOTIFY error with a Notify Message
Type of LOCATOR_TYPE_UNSUPPORTED, with the Notification Data field Type of LOCATOR_TYPE_UNSUPPORTED, with the Notification Data field
containing the locator(s) that the receiver failed to process. containing the locator(s) that the receiver failed to process.
Otherwise, a host MAY send a NOTIFY error if a (non-preferred) Otherwise, a host MAY send a NOTIFY error if a (non-preferred)
locator with an unsupported Locator Type is received in a LOCATOR_SET locator with an unsupported Locator Type is received in a LOCATOR_SET
parameter. parameter.
6.3. Verifying Address Reachability 5.3. Verifying Address Reachability
Address verification is defined in [I-D.ietf-hip-rfc5206-bis]. Address verification is defined in [I-D.ietf-hip-rfc5206-bis].
When address verification is in progress for a new Preferred locator, When address verification is in progress for a new Preferred locator,
the host SHOULD select a different locator listed as ACTIVE, if one the host SHOULD select a different locator listed as ACTIVE, if one
such locator is available, to continue communications until address such locator is available, to continue communications until address
verification completes. Alternatively, the host MAY use the new verification completes. Alternatively, the host MAY use the new
Preferred locator while in UNVERIFIED status to the extent Credit- Preferred locator while in UNVERIFIED status to the extent Credit-
Based Authorization permits. Credit-Based Authorization is explained Based Authorization permits. Credit-Based Authorization is explained
in [I-D.ietf-hip-rfc5206-bis]. Once address verification succeeds, in [I-D.ietf-hip-rfc5206-bis]. Once address verification succeeds,
the status of the new Preferred locator changes to ACTIVE. the status of the new Preferred locator changes to ACTIVE.
6.4. Changing the Preferred Locator 5.4. Changing the Preferred Locator
A host MAY want to change the Preferred outgoing locator for A host MAY want to change the Preferred outgoing locator for
different reasons, e.g., because traffic information or ICMP error different reasons, e.g., because traffic information or ICMP error
messages indicate that the currently used preferred address may have messages indicate that the currently used preferred address may have
become unreachable. Another reason may be due to receiving a become unreachable. Another reason may be due to receiving a
LOCATOR_SET parameter that has the "P" bit set. LOCATOR_SET parameter that has the "P" bit set.
To change the Preferred locator, the host initiates the following To change the Preferred locator, the host initiates the following
procedure: procedure:
skipping to change at page 17, line 23 skipping to change at page 18, line 41
or according to policy. This case may arise if, for example, or according to policy. This case may arise if, for example,
ICMP error messages that deprecate the Preferred locator arrive, ICMP error messages that deprecate the Preferred locator arrive,
but the peer has not yet indicated a new Preferred locator. but the peer has not yet indicated a new Preferred locator.
4. If the new Preferred locator has DEPRECATED status and there is 4. If the new Preferred locator has DEPRECATED status and there is
at least one non-deprecated address, the host selects one of the at least one non-deprecated address, the host selects one of the
non-deprecated addresses as a new Preferred locator and non-deprecated addresses as a new Preferred locator and
continues. If the selected address is UNVERIFIED, the address continues. If the selected address is UNVERIFIED, the address
verification procedure described above will apply. verification procedure described above will apply.
7. Security Considerations 6. Security Considerations
Security considerations are addressed in [I-D.ietf-hip-rfc5206-bis]. No additional security considerations beyond those outlined in
[I-D.ietf-hip-rfc5206-bis] have been identified.
8. IANA Considerations 7. IANA Considerations
This document has no new IANA considerations. This document has no requests for IANA actions.
9. Authors and Acknowledgments 8. Authors and Acknowledgments
This document contains content that was originally included in This document contains content that was originally included in
RFC5206. Pekka Nikander and Jari Arkko originated RFC5206, and RFC5206. Pekka Nikander and Jari Arkko originated RFC5206, and
Christian Vogt and Thomas Henderson (editor) later joined as co- Christian Vogt and Thomas Henderson (editor) later joined as co-
authors. Also in RFC5206, Greg Perkins contributed the initial draft authors. Also in RFC5206, Greg Perkins contributed the initial draft
of the security section, and Petri Jokela was a co-author of the of the security section, and Petri Jokela was a co-author of the
initial individual submission. initial individual submission.
The authors thank Miika Komu, Mika Kousa, Jeff Ahrenholz, and Jan The authors thank Miika Komu, Mika Kousa, Jeff Ahrenholz, and Jan
Melen for many improvements to the document. Melen for many improvements to the document. Concepts from a paper
on host multihoming across address families, by Samu Varjonen, Miika
Komu, and Andrei Gurtov, contributed to this revised version.
10. References 9. References
10.1. Normative references 9.1. Normative references
[I-D.ietf-hip-rfc5206-bis] [I-D.ietf-hip-rfc5206-bis]
Henderson, T., Vogt, C., and J. Arkko, "Host Mobility with Henderson, T., Vogt, C., and J. Arkko, "Host Mobility with
the Host Identity Protocol", draft-ietf-hip-rfc5206-bis-09 the Host Identity Protocol", draft-ietf-hip-rfc5206-bis-10
(work in progress), July 2015. (work in progress), January 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC3484] Draves, R., "Default Address Selection for Internet [RFC3484] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", RFC 3484, Protocol version 6 (IPv6)", RFC 3484,
DOI 10.17487/RFC3484, February 2003, DOI 10.17487/RFC3484, February 2003,
<http://www.rfc-editor.org/info/rfc3484>. <http://www.rfc-editor.org/info/rfc3484>.
skipping to change at page 18, line 26 skipping to change at page 20, line 5
Henderson, "Host Identity Protocol Version 2 (HIPv2)", Henderson, "Host Identity Protocol Version 2 (HIPv2)",
RFC 7401, DOI 10.17487/RFC7401, April 2015, RFC 7401, DOI 10.17487/RFC7401, April 2015,
<http://www.rfc-editor.org/info/rfc7401>. <http://www.rfc-editor.org/info/rfc7401>.
[RFC7402] Jokela, P., Moskowitz, R., and J. Melen, "Using the [RFC7402] Jokela, P., Moskowitz, R., and J. Melen, "Using the
Encapsulating Security Payload (ESP) Transport Format with Encapsulating Security Payload (ESP) Transport Format with
the Host Identity Protocol (HIP)", RFC 7402, the Host Identity Protocol (HIP)", RFC 7402,
DOI 10.17487/RFC7402, April 2015, DOI 10.17487/RFC7402, April 2015,
<http://www.rfc-editor.org/info/rfc7402>. <http://www.rfc-editor.org/info/rfc7402>.
10.2. Informative references 9.2. Informative references
[I-D.ietf-hip-rfc5204-bis]
Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extension", draft-ietf-hip-rfc5204-bis-07 (work
in progress), December 2015.
[RFC5533] Nordmark, E. and M. Bagnulo, "Shim6: Level 3 Multihoming [RFC5533] Nordmark, E. and M. Bagnulo, "Shim6: Level 3 Multihoming
Shim Protocol for IPv6", RFC 5533, DOI 10.17487/RFC5533, Shim Protocol for IPv6", RFC 5533, DOI 10.17487/RFC5533,
June 2009, <http://www.rfc-editor.org/info/rfc5533>. June 2009, <http://www.rfc-editor.org/info/rfc5533>.
Appendix A. Document Revision History Appendix A. Document Revision History
To be removed upon publication To be removed upon publication
+----------+--------------------------------------------------------+ +----------+--------------------------------------------------------+
skipping to change at page 19, line 32 skipping to change at page 21, line 32
| | | | | |
| draft-05 | Move remaining multihoming material from RFC5206-bis | | draft-05 | Move remaining multihoming material from RFC5206-bis |
| | to this document | | | to this document |
| | | | | |
| | Update lingering references to LOCATOR parameter to | | | Update lingering references to LOCATOR parameter to |
| | LOCATOR_SET | | | LOCATOR_SET |
| | | | | |
| draft-06 | Document refresh with updated references. | | draft-06 | Document refresh with updated references. |
| | | | | |
| draft-07 | Document refresh; no other changes. | | draft-07 | Document refresh; no other changes. |
| | |
| draft-08 | issues 3 and 11: Address complaints of complexity due |
| | to full mesh of SAs for multihoming. |
| | |
| | issue 5: Improve draft based on recommendations for |
| | cross-family handovers in paper by Varjonen et. al. |
| | |
| | issue 7: Clarify and distinguish between load |
| | balancing and fault tolerance use cases. |
+----------+--------------------------------------------------------+ +----------+--------------------------------------------------------+
Authors' Addresses Authors' Addresses
Thomas R. Henderson (editor) Thomas R. Henderson (editor)
University of Washington University of Washington
Campus Box 352500 Campus Box 352500
Seattle, WA Seattle, WA
USA USA
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