draft-ietf-hip-multihoming-04.txt   draft-ietf-hip-multihoming-05.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: May 16, 2015 J. Arkko Expires: July 16, 2015 J. Arkko
Ericsson Research NomadicLab Ericsson Research NomadicLab
November 12, 2014 January 12, 2015
Host Multihoming with the Host Identity Protocol Host Multihoming with the Host Identity Protocol
draft-ietf-hip-multihoming-04 draft-ietf-hip-multihoming-05
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-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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 May 16, 2015. This Internet-Draft will expire on July 16, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
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outside the IETF Standards Process, and derivative works of it may outside the IETF Standards Process, and derivative works of it may
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 . . . . . . . . . . . . . . . . . 4 2. Terminology and Conventions . . . . . . . . . . . . . . . . . 4
3. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . 4 3. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Operating Environment . . . . . . . . . . . . . . . . . . 5 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Multihoming Overview . . . . . . . . . . . . . . . . . . 7 4.1. Host Multihoming . . . . . . . . . . . . . . . . . . . . 5
4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7 4.2. Site Multihoming . . . . . . . . . . . . . . . . . . . . 7
4.1. Host Multihoming . . . . . . . . . . . . . . . . . . . . 8 4.3. Dual host multihoming . . . . . . . . . . . . . . . . . . 7
4.2. Site Multihoming . . . . . . . . . . . . . . . . . . . . 9 4.4. Combined Mobility and Multihoming . . . . . . . . . . . . 8
4.3. Dual host multihoming . . . . . . . . . . . . . . . . . . 10 4.5. Initiating the Protocol in R1 or I2 . . . . . . . . . . . 8
4.4. Combined Mobility and Multihoming . . . . . . . . . . . . 10 4.6. Using LOCATOR_SETs across Addressing Realms . . . . . . . 10
4.5. Initiating the Protocol in R1 or I2 . . . . . . . . . . . 11 5. Other Considerations . . . . . . . . . . . . . . . . . . . . 10
5. Other Considerations . . . . . . . . . . . . . . . . . . . . 12 5.1. Address Verification . . . . . . . . . . . . . . . . . . 10
5.1. Address Verification . . . . . . . . . . . . . . . . . . 12 5.2. Preferred Locator . . . . . . . . . . . . . . . . . . . . 10
5.2. Preferred Locator . . . . . . . . . . . . . . . . . . . . 12 5.3. Interaction with Security Associations . . . . . . . . . 10
5.3. Interaction with Security Associations . . . . . . . . . 13 6. Processing Rules . . . . . . . . . . . . . . . . . . . . . . 13
6. Processing Rules . . . . . . . . . . . . . . . . . . . . . . 15 6.1. Sending LOCATOR_SETs . . . . . . . . . . . . . . . . . . 13
6.1. Sending LOCATORs . . . . . . . . . . . . . . . . . . . . 15 6.2. Handling Received LOCATOR_SETs . . . . . . . . . . . . . 14
6.2. Handling Received LOCATORs . . . . . . . . . . . . . . . 17 6.3. Verifying Address Reachability . . . . . . . . . . . . . 16
6.3. Verifying Address Reachability . . . . . . . . . . . . . 19 6.4. Changing the Preferred Locator . . . . . . . . . . . . . 17
6.4. Changing the Preferred Locator . . . . . . . . . . . . . 19 7. Security Considerations . . . . . . . . . . . . . . . . . . . 17
7. Security Considerations . . . . . . . . . . . . . . . . . . . 20 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 9. Authors and Acknowledgments . . . . . . . . . . . . . . . . . 18
9. Authors and Acknowledgments . . . . . . . . . . . . . . . . . 20 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 10.1. Normative references . . . . . . . . . . . . . . . . . . 18
10.1. Normative references . . . . . . . . . . . . . . . . . . 20 10.2. Informative references . . . . . . . . . . . . . . . . . 18
10.2. Informative references . . . . . . . . . . . . . . . . . 21 Appendix A. Document Revision History . . . . . . . . . . . . . 20
Appendix A. Document Revision History . . . . . . . . . . . . . 22
1. Introduction and Scope 1. Introduction and Scope
The Host Identity Protocol [I-D.ietf-hip-rfc4423-bis] (HIP) supports The Host Identity Protocol [I-D.ietf-hip-rfc4423-bis] (HIP) supports
an architecture that decouples the transport layer (TCP, UDP, etc.) an architecture that decouples the transport layer (TCP, UDP, etc.)
from the internetworking layer (IPv4 and IPv6) by using public/ from the internetworking layer (IPv4 and IPv6) by using public/
private key pairs, instead of IP addresses, as host identities. When private key pairs, instead of IP addresses, as host identities. When
a host uses HIP, the overlying protocol sublayers (e.g., transport a host uses HIP, the overlying protocol sublayers (e.g., transport
layer sockets and Encapsulating Security Payload (ESP) Security layer sockets and Encapsulating Security Payload (ESP) Security
Associations (SAs)) are instead bound to representations of these Associations (SAs)) are instead bound to representations of these
host identities, and the IP addresses are only used for packet host identities, and the IP addresses are only used for packet
forwarding. However, each host must also know at least one IP forwarding. However, each host must also know at least one IP
address at which its peers are reachable. Initially, these IP address at which its peers are reachable. Initially, these IP
addresses are the ones used during the HIP base exchange addresses are the ones used during the HIP base exchange
[I-D.ietf-hip-rfc5201-bis]. [I-D.ietf-hip-rfc5201-bis].
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. 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. The scope of this document encompasses
messaging and elements of procedure for some basic host multihoming messaging and elements of procedure for some basic host multihoming
scenarios of interest. scenarios of interest.
Another variation of multihoming that has been heavily studied site Another variation of multihoming that has been heavily studied is
multihoming. Solutions for site multihoming in IPv6 networks have site multihoming. Solutions for site multihoming in IPv6 networks
been specified by the IETF shim6 working group. The shim6 protocol have been specified by the IETF shim6 working group. The shim6
[RFC5533] bears many architectural similarities to HIP but there are protocol [RFC5533] bears many architectural similarities to HIP but
differences in the security model and in the protocol. Future there are differences in the security model and in the protocol.
versions of this draft will summarize the differences more
completely.
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 [I-D.ietf-hip-rfc5202-bis], this document largely transport format [I-D.ietf-hip-rfc5202-bis], this document largely
assumes the use of ESP and leaves other transport formats for further assumes the use of ESP and leaves other transport formats for further
study. study.
There are a number of situations where the simple end-to-end There are a number of situations where the simple end-to-end
readdressing functionality defined herein is not sufficient. These readdressing functionality defined herein is not sufficient. These
include the initial reachability of a multihomed host, location include the initial reachability of a multihomed host, location
privacy, simultaneous mobility of both hosts, and some modes of NAT privacy, simultaneous mobility of both hosts, and some modes of NAT
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Quality of Service (QoS). Transport-layer mobility triggers, and the Quality of Service (QoS). Transport-layer mobility triggers, and the
proper transport response to a HIP multihoming address change, are proper transport response to a HIP multihoming address change, are
outside the scope of this document. outside the scope of this document.
2. Terminology and Conventions 2. Terminology and Conventions
The key words "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 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Terminology is copied from [I-D.ietf-hip-rfc5206-bis]. The following terms used in this document are defined in
[I-D.ietf-hip-rfc5206-bis]: LOCATOR_SET, Locator, Address, Preferred
LOCATOR. The name of a HIP parameter containing zero or more Locator locator, and Credit Based Authorization.
fields. This parameter's name is distinguished from the Locator
fields embedded within it by the use of all capital letters.
Locator. A name that controls how the packet is routed through the
network and demultiplexed by the end host. It may include a
concatenation of traditional network addresses such as an IPv6
address and end-to-end identifiers such as an ESP SPI. It may
also include transport port numbers or IPv6 Flow Labels as
demultiplexing context, or it may simply be a network address.
Address. A name that denotes a point-of-attachment to the network.
The two most common examples are an IPv4 address and an IPv6
address. The set of possible addresses is a subset of the set of
possible locators.
Preferred locator. A locator on which a host prefers to receive
data. With respect to a given peer, a host always has one active
Preferred locator, unless there are no active locators. By
default, the locators used in the HIP base exchange are the
Preferred locators.
Credit Based Authorization. A host must verify a mobile or
multihomed peer's reachability at a new locator. Credit-Based
Authorization authorizes the peer to receive a certain amount of
data at the new locator before the result of such verification is
known.
3. Protocol Model 3. Protocol Model
This section is an overview; more detailed specification follows this The protocol model for HIP support of host multihoming extends the
section. model for host mobility described in Section 3 of
[I-D.ietf-hip-rfc5206-bis]. This section only highlights the
The overall protocol model is the same as in Section 3 of
[I-D.ietf-hip-rfc5206-bis]; this section only highlights the
differences. differences.
3.1. Operating Environment
The Host Identity Protocol (HIP) [I-D.ietf-hip-rfc5201-bis] is a key
establishment and parameter negotiation protocol. Its primary
applications are for authenticating host messages based on host
identities, and establishing security associations (SAs) for the ESP
transport format [I-D.ietf-hip-rfc5202-bis] and possibly other
protocols in the future.
+--------------------+ +--------------------+
| | | |
| +------------+ | | +------------+ |
| | Key | | HIP | | Key | |
| | Management | <-+-----------------------+-> | Management | |
| | Process | | | | Process | |
| +------------+ | | +------------+ |
| ^ | | ^ |
| | | | | |
| v | | v |
| +------------+ | | +------------+ |
| | IPsec | | ESP | | IPsec | |
| | Stack | <-+-----------------------+-> | Stack | |
| | | | | | | |
| +------------+ | | +------------+ |
| | | |
| | | |
| Initiator | | Responder |
+--------------------+ +--------------------+
Figure 1: HIP Deployment Model
The general deployment model for HIP is shown above, assuming
operation in an end-to-end fashion. This document specifies
extensions to the HIP protocol to enable end-host mobility and basic
multihoming. In summary, these extensions to the HIP base protocol
enable the signaling of new addressing information to the peer in HIP
messages. The messages are authenticated via a signature or keyed
hash message authentication code (HMAC) based on its Host Identity.
---------
| TCP | (sockets bound to HITs)
---------
|
---------
----> | ESP | {HIT_s, HIT_d} <-> SPI
| ---------
| |
---- ---------
| MH |-> | HIP | {HIT_s, HIT_d, SPI} <-> {IP_s, IP_d, SPI}
---- ---------
|
---------
| IP |
---------
Figure 2: Architecture for HIP Multihoming (MH)
Figure 2 depicts a layered architectural view of a HIP-enabled stack
using the ESP transport format. In HIP, upper-layer protocols
(including TCP and ESP in this figure) are bound to Host Identity
Tags (HITs) and not IP addresses. The HIP sublayer is responsible
for maintaining the binding between HITs and IP addresses. The SPI
is used to associate an incoming packet with the right HITs. The
block labeled "MH" is introduced below.
Consider the case when a host is multihomed (has more than one
globally routable address) and has multiple addresses available at
the HIP layer as alternative locators for fault tolerance. Examples
include the use of (possibly multiple) IPv4 and IPv6 addresses on the
same interface, or the use of multiple interfaces attached to
different service providers. Such host multihoming generally
necessitates that a separate ESP SA is maintained for each interface
in order to prevent packets that arrive over different paths from
falling outside of the ESP anti-replay window [RFC4303]. Multihoming
thus makes it possible that the bindings shown on the right side of
Figure 2 are one to many (in the outbound direction, one HIT pair to
multiple SPIs, and possibly then to multiple IP addresses). However,
only one SPI and address pair can be used for any given packet, so
the job of the "MH" block depicted above is to dynamically manipulate
these bindings. Beyond locally managing such multiple bindings, the
peer-to-peer HIP signaling protocol needs to be flexible enough to
define the desired mappings between HITs, SPIs, and addresses, and
needs to ensure that UPDATE messages are sent along the right network
paths so that any HIP-aware middleboxes can observe the SPIs. This
document does not specify the "MH" block, nor does it specify
detailed elements of procedure for how to handle various multihoming
(perhaps combined with mobility) scenarios. The "MH" block may apply
to more general problems outside of HIP. However, this document does
describe a basic multihoming case (one host adds one address to its
initial address and notifies the peer) and leave more complicated
scenarios for experimentation and future documents.
3.2. Multihoming Overview
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 parameter defined in [I-D.ietf-hip-rfc5206-bis], a host can LOCATOR_SET parameter defined in [I-D.ietf-hip-rfc5206-bis], a host
inform its peers of additional (multiple) locators at which it can be can inform its peers of additional (multiple) locators at which it
reached, and can declare a particular locator as a "preferred" can be reached. When multiple locators are available and announced
locator. Although this document defines a basic mechanism for to the peer, a host can designate a particular locator as a
multihoming, it does not define detailed policies and procedures, "preferred" locator, meaning that the host prefers that its peer send
packets to the designated address before trying an alternative
address. Although this document defines a basic mechanism for
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 pair is
available, the operation of simultaneous mobility and multihoming, available, the operation of simultaneous mobility and multihoming,
source address selection policies (beyond those specified in source address selection policies (beyond those specified in
[RFC3484]), and the implications of multihoming on transport [RFC3484]), and the implications of multihoming on transport
protocols and ESP anti-replay windows. 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
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The scenarios below assume that the two hosts have completed a single The scenarios below assume that the two hosts have completed a single
HIP base exchange with each other. Both of the hosts therefore have HIP base exchange with each other. Both of the hosts therefore have
one incoming and one outgoing SA. Further, each SA uses the same 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. 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 readdressing protocol is an asymmetric protocol where a mobile or
multihomed host informs a peer host about changes of IP addresses on multihomed host informs a peer host about changes of IP addresses on
affected SPIs. The readdressing exchange is designed to be affected SPIs. The readdressing exchange is designed to be
piggybacked on existing HIP exchanges. The majority of the packets piggybacked on existing HIP exchanges. The majority of the packets
on which the LOCATOR parameters are expected to be carried are UPDATE on which the LOCATOR_SET parameters are expected to be carried are
packets. However, some implementations may want to experiment with UPDATE packets. However, some implementations may want to experiment
sending LOCATOR parameters also on other packets, such as R1, I2, and with sending LOCATOR_SET parameters also on other packets, such as
NOTIFY. R1, I2, and NOTIFY.
The scenarios below at times describe addresses as being in either an The scenarios below at times describe addresses as being in either an
ACTIVE, VERIFIED, or DEPRECATED state. From the perspective of a 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.
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 parameter. or via the LOCATOR_SET parameter.
4.1. Host Multihoming 4.1. Host Multihoming
A (mobile or stationary) host may sometimes have more than one A (mobile or stationary) host may sometimes have more than one
interface or global address. The host may notify the peer host of interface or global address. The host may notify the peer host of
the additional interface or address by using the LOCATOR parameter. the additional interface or address by using the LOCATOR_SET
To avoid problems with the ESP anti-replay window, a host SHOULD use parameter. To avoid problems with the ESP anti-replay window, a host
a different SA for each interface or address used to receive packets SHOULD use a different SA for each interface or address used to
from the peer host when multiple locator pairs are being used receive packets from the peer host when multiple locator pairs are
simultaneously rather than sequentially. being used simultaneously rather than sequentially.
When more than one locator is provided to the peer host, the host When more than one locator is provided to the peer host, the host
SHOULD indicate which locator is preferred (the locator on which the SHOULD indicate which locator is preferred (the locator on which the
host prefers to receive traffic). By default, the addresses used in host prefers to receive traffic). By default, the addresses used in
the base exchange are preferred until indicated otherwise. the base exchange are preferred until indicated otherwise.
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
skipping to change at page 8, line 48 skipping to change at page 6, line 11
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. Although asymmetric SA configurations might be
experimented with, their usage may constrain interoperability at this experimented with, their usage may constrain interoperability at this
time. However, it is recommended that implementations attempt to time. However, it is recommended that implementations attempt to
support peers that prefer to use non-paired SAs. It is expected that support peers that prefer to use non-paired SAs.
this section and behavior will be modified in future revisions of
this protocol, once the issue and its implications are better
understood.
Consider the case between two hosts, one single-homed and one Consider the case between two hosts, one single-homed and one
multihomed. The multihomed host may decide to inform the single- multihomed. The multihomed host may decide to inform the single-
homed host about its other address. It is RECOMMENDED that the homed host about its other address. It is RECOMMENDED that the
multihomed host set up a new SA pair for use on this new address. To multihomed host set up a new SA pair for use on this new address. To
do this, the multihomed host sends a LOCATOR with an ESP_INFO, 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 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 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 Locator Type of "1" is used to associate the new address with the new
SPI. The LOCATOR parameter also contains a second Type "1" locator, SPI. The LOCATOR_SET parameter also contains a second Type "1"
that of the original address and SPI. To simplify parameter locator, that of the original address and SPI. To simplify parameter
processing and avoid explicit protocol extensions to remove locators, processing and avoid explicit protocol extensions to remove locators,
each LOCATOR parameter MUST list all locators in use on a connection each LOCATOR_SET parameter MUST list all locators in use on a
(a complete listing of inbound locators and SPIs for the host). The connection (a complete listing of inbound locators and SPIs for the
multihomed host waits for an ESP_INFO (new outbound SA) from the peer host). The multihomed host waits for an ESP_INFO (new outbound SA)
and an ACK of its own UPDATE. As in the mobility case, the peer host from the peer and an ACK of its own UPDATE. As in the mobility case,
must perform an address verification before actively using the new the peer host must perform an address verification before actively
address. Figure 3 illustrates this scenario. using the new address. Figure 1 illustrates this scenario.
Multi-homed Host Peer Host Multi-homed Host Peer Host
UPDATE(ESP_INFO, LOCATOR, 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 3: Basic Multihoming Scenario Figure 1: Basic Multihoming Scenario
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 LOCATORs 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 as the local address to which the LOCATOR plus containing the LOCATOR_SET as the local address to which the
ESP_INFO is targeted. This is because hosts may send UPDATEs with LOCATOR_SET plus ESP_INFO is targeted. This is because hosts may
the same (locator) IP address to different peer addresses -- this has send UPDATEs with the same (locator) IP address to different peer
the effect of creating multiple inbound SAs implicitly affiliated addresses -- this has the effect of creating multiple inbound SAs
with different peer source addresses. implicitly affiliated with different peer source addresses.
4.2. Site Multihoming 4.2. 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 4.1. Note that a single
interface may experience site multihoming while the host itself may interface may experience site multihoming while the host itself may
have multiple interfaces. have multiple 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 specify additional site multihoming This document does not presently additional site multihoming
extensions to HIP; further alignment with the IETF shim6 working extensions to HIP; such extensions are for further study.
group may be considered in the future.
4.3. Dual host multihoming 4.3. Dual host multihoming
Consider the case in which both hosts would like to add an additional Consider the case in which both hosts would like to add an additional
address after the base exchange completes. In Figure 4, consider address after the base exchange completes. In Figure 2, consider
that host1, which used address addr1a in the base exchange to set up that host1, which used address addr1a in the base exchange to set up
SPI1a and SPI2a, wants to add address addr1b. It would send an SPI1a and SPI2a, wants to add address addr1b. It would send an
UPDATE with LOCATOR (containing the address addr1b) to host2, using UPDATE with LOCATOR_SET (containing the address addr1b) to host2,
destination address addr2a, and a new set of SPIs would be added using destination address addr2a, and a new set of SPIs would be
between hosts 1 and 2 (call them SPI1b and SPI2b -- not shown in the added between hosts 1 and 2 (call them SPI1b and SPI2b -- not shown
figure). Next, consider host2 deciding to add addr2b to the in the figure). Next, consider host2 deciding to add addr2b to the
relationship. Host2 must select one of host1's addresses towards relationship. Host2 must select one of host1's addresses towards
which to initiate an UPDATE. It may choose to initiate an UPDATE to 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 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 mesh (four SA pairs) of SAs would exist between the two hosts. This
is the most general case; it often may be the case that hosts is the most general case; it often may be the case that hosts
primarily establish new SAs only with the peer's Preferred locator. primarily establish new SAs only with the peer's Preferred locator.
The readdressing protocol is flexible enough to accommodate this The readdressing protocol is flexible enough to accommodate this
choice. 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 4: Dual Multihoming Case in Which Each Host Uses LOCATOR to Figure 2: Dual Multihoming Case in Which Each Host Uses LOCATOR_SET
Add a Second Address to Add a Second Address
4.4. Combined Mobility and Multihoming 4.4. 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 plus ESP_INFO should be flexible enough to handle The use of LOCATOR_SET plus ESP_INFO should be flexible enough to
most such scenarios, although more complicated scenarios have not handle most such scenarios, although more complicated scenarios have
been studied so far. not been studied so far.
4.5. Initiating the Protocol in R1 or I2 4.5. Initiating the Protocol in R1 or I2
A Responder host MAY include a LOCATOR 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 parameters with the R1 signature. If the R1 packet contains LOCATOR_SET parameters
a new Preferred locator, the Initiator SHOULD directly set the new with a new Preferred locator, the Initiator SHOULD directly set the
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.
Initiator Responder Initiator Responder
R1 with LOCATOR 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 5: LOCATOR Inclusion in R1 Figure 3: LOCATOR_SET Inclusion in R1
An Initiator MAY include one or more LOCATOR 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 parameter packet, independent of whether or not there was a LOCATOR_SET
in the R1. These parameters MUST be protected by the I2 signature. parameter in the R1. These parameters MUST be protected by the I2
Even if the I2 packet contains LOCATOR parameters, the Responder MUST signature. Even if the I2 packet contains LOCATOR_SET parameters,
still send the R2 packet to the source address of the I2. The new the Responder MUST still send the R2 packet to the source address of
Preferred locator SHOULD be identical to the I2 source address. If the I2. The new Preferred locator SHOULD be identical to the I2
the I2 packet contains LOCATOR parameters, all new locators must source address. If the I2 packet contains LOCATOR_SET parameters,
undergo address verification as usual, and the ESP traffic that all new locators must undergo address verification as usual, and the
subsequently follows should use the Preferred locator. ESP traffic that subsequently follows should use the Preferred
locator.
Initiator Responder Initiator Responder
I2 with LOCATOR 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 6: LOCATOR Inclusion in I2 Figure 4: 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 parameter is present in R1. In this case, implementations LOCATOR_SET parameter is present in R1. In this case,
simultaneously using multiple pre-created R1s, indexed by Initiator implementations simultaneously using multiple pre-created R1s,
IP addresses, may inadvertently fail the puzzle solution of I2 indexed by Initiator IP addresses, may inadvertently fail the puzzle
packets due to a perceived puzzle mismatch. See, for instance, the solution of I2 packets due to a perceived puzzle mismatch. See, for
example in Appendix A of [I-D.ietf-hip-rfc5201-bis]. As a solution, instance, the example in Appendix A of [I-D.ietf-hip-rfc5201-bis].
the Responder's puzzle indexing mechanism must be flexible enough to As a solution, the Responder's puzzle indexing mechanism must be
accommodate the situation when R1 includes a LOCATOR parameter. flexible enough to accommodate the situation when R1 includes a
LOCATOR_SET parameter.
4.6. Using LOCATOR_SETs across Addressing Realms
It is possible for HIP associations to migrate to a state in which
both parties are only using locators in different addressing realms.
For example, the two hosts may initiate the HIP association when both
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. Other Considerations
5.1. Address Verification 5.1. Address Verification
An address verification method is specified in An address verification method is specified in
[I-D.ietf-hip-rfc5206-bis]. It is expected that addresses learned in [I-D.ietf-hip-rfc5206-bis]. It is expected that addresses learned in
multihoming scenarios also are subject to the same verification multihoming scenarios also are subject to the same verification
rules. rules.
skipping to change at page 13, line 7 skipping to change at page 10, line 47
In general, when multiple locators are used for a session, there is In general, when multiple locators are used for a session, there is
the question of using multiple locators for failover only or for the question of using multiple locators for failover only or for
load-balancing. Due to the implications of load-balancing on the load-balancing. Due to the implications of load-balancing on the
transport layer that still need to be worked out, this document transport layer that still need to be worked out, this document
assumes that multiple locators are used primarily for failover. An assumes that multiple locators are used primarily for failover. An
implementation may use ICMP interactions, reachability checks, or implementation may use ICMP interactions, reachability checks, or
other means to detect the failure of a locator. other means to detect the failure of a locator.
5.3. Interaction with Security Associations 5.3. Interaction with Security Associations
This document uses the HIP LOCATOR protocol parameter, specified in This document uses the HIP LOCATOR_SET protocol parameter, specified
[I-D.ietf-hip-rfc5206-bis]), that allows the hosts to exchange in [I-D.ietf-hip-rfc5206-bis]), that allows the hosts to exchange
information about their locator(s) and any changes in their information about their locator(s) and any changes in their
locator(s). The logical structure created with LOCATOR parameters locator(s). The logical structure created with LOCATOR_SET
has three levels: hosts, Security Associations (SAs) indexed by parameters has three levels: hosts, Security Associations (SAs)
Security Parameter Indices (SPIs), and addresses. indexed by Security Parameter Indices (SPIs), and addresses.
The relation between these levels for an association constructed as The relation between these levels for an association constructed as
defined in the base specification [I-D.ietf-hip-rfc5201-bis] and ESP defined in the base specification [I-D.ietf-hip-rfc5201-bis] and ESP
transform [I-D.ietf-hip-rfc5202-bis] is illustrated in Figure 7. transform [I-D.ietf-hip-rfc5202-bis] is illustrated in Figure 5.
-<- SPI1a -- -- SPI2a ->- -<- SPI1a -- -- SPI2a ->-
host1 < > addr1a <---> addr2a < > host2 host1 < > addr1a <---> addr2a < > host2
->- SPI2a -- -- SPI1a -<- ->- SPI2a -- -- SPI1a -<-
Figure 7: Relation between Hosts, SPIs, and Addresses (Base Figure 5: Relation between Hosts, SPIs, and Addresses (Base
Specification) Specification)
In Figure 7, host1 and host2 negotiate two unidirectional SAs, and In Figure 5, host1 and host2 negotiate two unidirectional SAs, and
each host selects the SPI value for its inbound SA. The addresses each host selects the SPI value for its inbound SA. The addresses
addr1a and addr2a are the source addresses that the hosts use in the addr1a and addr2a are the source addresses that the hosts use in the
base HIP exchange. These are the "preferred" (and only) addresses base HIP exchange. These are the "preferred" (and only) addresses
conveyed to the peer for use on each SA. That is, although packets conveyed to the peer for use on each SA. That is, although packets
sent to any of the hosts' interfaces may be accepted on the inbound 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 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 address learned in the base exchange (e.g., for host1, it sends a
packet on SPI2a to addr2a to reach host2), unless other mechanisms packet on SPI2a to addr2a to reach host2), unless other mechanisms
exist to learn of new addresses. exist to learn of new addresses.
In general, the bindings that exist in an implementation In general, the bindings that exist in an implementation
corresponding to this document can be depicted as shown in Figure 8. corresponding to this document can be depicted as shown in Figure 6.
In this figure, a host can have multiple inbound SPIs (and, not In this figure, a host can have multiple inbound SPIs (and, not
shown, multiple outbound SPIs) associated with another host. shown, multiple outbound SPIs) associated with another host.
Furthermore, each SPI may have multiple addresses associated with it. Furthermore, each SPI may have multiple addresses associated with it.
These addresses that are bound to an SPI are not used to lookup the 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 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 the peer host, as hints for which addresses to use to reach the host
on that SPI. The LOCATOR parameter is used to change the set of on that SPI. The LOCATOR_SET parameter is used to change the set of
addresses that a peer associates with a particular SPI. addresses that a peer associates with a particular SPI.
address11 address11
/ /
SPI1 - address12 SPI1 - address12
/ /
/ address21 / address21
host -- SPI2 < host -- SPI2 <
\ address22 \ address22
\ \
SPI3 - address31 SPI3 - address31
\ \
address32 address32
Figure 8: Relation between Hosts, SPIs, and Addresses (General Case) Figure 6: Relation between Hosts, SPIs, and Addresses (General Case)
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. For example, if the host needs to change its addresses
on SPI2, it is likely that both address21 and address22 will on SPI2, it is likely that both address21 and address22 will
simultaneously become obsolete. In a typical case, such SPIs may simultaneously become obsolete. In a typical case, such SPIs may
correspond with physical interfaces; see below. Note, however, that correspond with physical interfaces; see below. Note, however, that
especially in the case of site multihoming, one of the addresses may especially in the case of site multihoming, one of the addresses may
become unreachable while the other one still works. In the typical become unreachable while the other one still works. In the typical
case, however, this does not require the host to inform its peers case, however, this does not require the host to inform its peers
about the situation, since even the non-working address still about the situation, since even the non-working address still
logically exists. 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 8, it may seem used to lookup the incoming SA. Therefore, in Figure 6, it may seem
unnecessary for address31, for example, to be associated only with unnecessary for address31, for example, to be associated only with
SPI3 -- in practice, a packet may arrive to SPI1 via destination SPI3 -- in practice, a packet may arrive to SPI1 via destination
address address31 as well. However, the use of different source and address address31 as well. However, the use of different source and
destination addresses typically leads to different paths, with 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.
skipping to change at page 15, line 15 skipping to change at page 12, line 49
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 An address may appear on more than one SPI. This creates no
ambiguity since the receiver will ignore the IP addresses during SA ambiguity since the receiver will ignore the IP addresses during SA
lookup anyway. However, this document does not specify such cases. lookup anyway. However, this document does not specify such cases.
When the LOCATOR parameter is sent in an UPDATE packet, then the When the LOCATOR_SET parameter is sent in an UPDATE packet, then the
receiver will respond with an UPDATE acknowledgment. When the receiver will respond with an UPDATE acknowledgment. When the
LOCATOR parameter is sent in an R1 or I2 packet, the base exchange LOCATOR_SET parameter is sent in an R1 or I2 packet, the base
retransmission mechanism will confirm its successful delivery. exchange retransmission mechanism will confirm its successful
LOCATORs may experimentally be used in NOTIFY packets; in this case, delivery. LOCATOR_SETs may experimentally be used in NOTIFY packets;
the recipient MUST consider the LOCATOR as informational and not in this case, the recipient MUST consider the LOCATOR_SET as
immediately change the current preferred address, but can test the informational and not immediately change the current preferred
additional locators when the need arises. The use of the LOCATOR in address, but can test the additional locators when the need arises.
a NOTIFY message may not be compatible with middleboxes. The use of the LOCATOR_SET in a NOTIFY message may not be compatible
with middleboxes.
6. Processing Rules 6. Processing Rules
Processing rules are specified in [I-D.ietf-hip-rfc5206-bis]. Future Basic processing rules for the LOCATOR_SET parameter are specified in
versions of this document will specify multihoming-specific [I-D.ietf-hip-rfc5206-bis]. This document focuses on multihoming-
processing rules here. specific rules.
6.1. Sending LOCATORs 6.1. Sending LOCATOR_SETs
The decision of when to send LOCATORs is basically a local policy The decision of when to send a LOCATOR_SET, and which addresses to
issue. However, it is RECOMMENDED that a host send a LOCATOR include, is a local policy issue. [I-D.ietf-hip-rfc5206-bis]
whenever it recognizes a change of its IP addresses in use on an recommends that a host send a LOCATOR_SET whenever it recognizes a
active HIP association, and assumes that the change is going to last change of its IP addresses in use on an active HIP association, and
at least for a few seconds. Rapidly sending LOCATORs that force the assumes that the change is going to last at least for a few seconds.
peer to change the preferred address SHOULD be avoided. It is possible to delay the exposure of additional locators to the
peer, and to send data from previously unannounced locators, as might
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 in separate UPDATEs on interaction requires sending the same LOCATOR_SET in separate UPDATEs
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
anti-replay protection considerations. In the typical case, simply anti-replay protection considerations. In the typical case, simply
basing the grouping on actual kernel level physical and logical basing the grouping on actual kernel level physical and logical
interfaces may be the best policy. Grouping policy is outside of the interfaces may be the best policy. Grouping policy is outside of the
scope of this document. scope of this document.
Note that the purpose of announcing IP addresses in a LOCATOR is to Locators corresponding to tunnel interfaces (e.g. IPsec tunnel
provide connectivity between the communicating hosts. In most cases, interfaces or Mobile IP home addresses) or other virtual interfaces
tunnels or virtual interfaces such as IPsec tunnel interfaces or MAY be announced in a LOCATOR_SET, but implementations SHOULD avoid
Mobile IP home addresses provide sub-optimal connectivity. announcing such locators as preferred locators if more direct paths
Furthermore, it should be possible to replace most tunnels with HIP may be obtained by instead preferring locators from non-tunneling
based "non-tunneling", therefore making most virtual interfaces interfaces if such locators provide a more direct path to the HIP
fairly unnecessary in the future. Therefore, virtual interfaces peer.
SHOULD NOT be announced in general. On the other hand, there are
clearly situations where tunnels are used for diagnostic and/or
testing purposes. In such and other similar cases announcing the IP
addresses of virtual interfaces may be appropriate.
Hosts MUST NOT announce broadcast or multicast addresses in LOCATORs. Hosts MUST NOT announce broadcast or multicast addresses in
Link-local addresses MAY be announced to peers that are known to be LOCATOR_SETs. Link-local addresses MAY be announced to peers that
neighbors on the same link, such as when the IP destination address are known to be neighbors on the same link, such as when the IP
of a peer is also link-local. The announcement of link-local destination address of a peer is also link-local. The announcement
addresses in this case is a policy decision; link-local addresses of link-local addresses in this case is a policy decision; link-local
used as Preferred locators will create reachability problems when the addresses used as Preferred locators will create reachability
host moves to another link. In any case, link-local addresses MUST problems when the host moves to another link. In any case, link-
NOT be announced to a peer unless that peer is known to be on the local addresses MUST NOT be announced to a peer unless that peer is
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 parameter that serves as a complete to the SPIs, it creates a LOCATOR_SET parameter that serves as a
representation of the addresses and affiliated SPIs intended for complete representation of the addresses and affiliated SPIs intended
active use. We now describe a few cases introduced in Section 4. We for active use. We now describe a few cases introduced in Section 4.
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 SHOULD set up a new SA
pair between this new address and the preferred address of the pair between this new address and the preferred address of the
peer host. To do this, the multihomed host creates a new inbound peer host. To do this, the multihomed host creates a new inbound
SA and creates a new SPI. For the outgoing UPDATE message, it SA and creates a new SPI. For the outgoing UPDATE message, it
inserts an ESP_INFO parameter with an OLD SPI field of "0", a NEW inserts an ESP_INFO parameter with an OLD SPI field of "0", a NEW
SPI field corresponding to the new SPI, and a KEYMAT Index as SPI field corresponding to the new SPI, and a KEYMAT Index as
selected by local policy. The host adds to the UPDATE message a selected by local policy. The host adds to the UPDATE message a
LOCATOR with two Type "1" Locators: the original address and SPI LOCATOR_SET with two Type "1" Locators: the original address and
active on the association, and the new address and new SPI being SPI active on the association, and the new address and new SPI
added (with the SPI matching the NEW SPI contained in the being added (with the SPI matching the NEW SPI contained in the
ESP_INFO). The Preferred bit SHOULD be set depending on the ESP_INFO). The Preferred bit SHOULD be set depending on the
policy to tell the peer host which of the two locators is policy to tell the peer host which of the two locators is
preferred. The UPDATE also contains a SEQ parameter and preferred. The UPDATE also contains a SEQ parameter and
optionally a DIFFIE_HELLMAN parameter, and follows rekeying 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 LOCATORs, locators with Locator Type "0", and The sending of multiple LOCATOR_SETs, locators with Locator Type "0",
multiple ESP_INFO parameters is for further study. Note that the and multiple ESP_INFO parameters is for further study. Note that the
inclusion of LOCATOR 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 LOCATORs 6.2. Handling Received LOCATOR_SETs
A host SHOULD be prepared to receive a LOCATOR 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, UPDATE, and NOTIFY.
This document describes sending both ESP_INFO and LOCATOR parameters This document describes sending both ESP_INFO and LOCATOR_SET
in an UPDATE. The ESP_INFO parameter is included when there is a parameters in an UPDATE. The ESP_INFO parameter is included when
need to rekey or key a new SPI, and is otherwise included for the there is a need to rekey or key a new SPI, and is otherwise included
possible benefit of HIP-aware middleboxes. The LOCATOR parameter for the possible benefit of HIP-aware middleboxes. The LOCATOR_SET
contains a complete map of the locators that the host wishes to make parameter contains a complete map of the locators that the host
or keep active for the HIP association. wishes to make or keep active for the HIP association.
In general, the processing of a LOCATOR depends upon the packet type In general, the processing of a LOCATOR_SET depends upon the packet
in which it is included. Here, we describe only the case in which type in which it is included. Here, we describe only the case in
ESP_INFO is present and a single LOCATOR and ESP_INFO are sent in an which ESP_INFO is present and a single LOCATOR_SET and ESP_INFO are
UPDATE message; other cases are for further study. The steps below sent in an UPDATE message; other cases are for further study. The
cover each of the cases described in Section 6.1. steps below cover each of the cases described in Section 6.1.
The processing of ESP_INFO and LOCATOR parameters is intended to be The processing of ESP_INFO and LOCATOR_SET parameters is intended to
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 parameters. A host SHOULD multiple ESP_INFO and/or multiple LOCATOR_SET parameters. A host
first process the ESP_INFO before the LOCATOR, since the ESP_INFO may SHOULD first process the ESP_INFO before the LOCATOR_SET, since the
contain a new SPI value mapped to an existing SPI, while a Type "1" ESP_INFO may contain a new SPI value mapped to an existing SPI, while
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 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
ESP_INFO parameter indicates whether an SA is being rekeyed, created, ESP_INFO parameter indicates whether an SA is being rekeyed, created,
deprecated, or just identified for the benefit of middleboxes. The deprecated, or just identified for the benefit of middleboxes. The
host examines the OLD SPI and NEW SPI values in the ESP_INFO host examines the OLD SPI and NEW SPI values in the ESP_INFO
parameter: parameter:
1. (no rekeying) If the OLD SPI is equal to the NEW SPI and both 1. (no rekeying) If the OLD SPI is equal to the NEW SPI and both
correspond to an existing SPI, the ESP_INFO is gratuitous correspond to an existing SPI, the ESP_INFO is gratuitous
(provided for middleboxes) and no rekeying is necessary. (provided for middleboxes) and no rekeying is necessary.
2. (rekeying) If the OLD SPI indicates an existing SPI and the NEW 2. (rekeying) If the OLD SPI indicates an existing SPI and the NEW
SPI is a different non-zero value, the existing SA is being SPI is a different non-zero value, the existing SA is being
rekeyed and the host follows HIP ESP rekeying procedures by rekeyed and the host follows HIP ESP rekeying procedures by
creating a new outbound SA with an SPI corresponding to the NEW creating a new outbound SA with an SPI corresponding to the NEW
SPI, with no addresses bound to this SPI. Note that locators in SPI, with no addresses bound to this SPI. Note that locators in
the LOCATOR parameter will reference this new SPI instead of the the LOCATOR_SET parameter will reference this new SPI instead of
old SPI. the old SPI.
3. (new SA) If the OLD SPI value is zero and the NEW SPI is a new 3. (new SA) If the OLD SPI value is zero and the NEW SPI is a new
non-zero value, then a new SA is being requested by the peer. non-zero value, then a new SA is being requested by the peer.
This case is also treated like a rekeying event; the receiving This case is also treated like a rekeying event; the receiving
host must create a new SA and respond with an UPDATE ACK. host must create a new SA and respond with an UPDATE ACK.
4. (deprecating the SA) If the OLD SPI indicates an existing SPI and 4. (deprecating the SA) If the OLD SPI indicates an existing SPI and
the NEW SPI is zero, the SA is being deprecated and all locators the NEW SPI is zero, the SA is being deprecated and all locators
uniquely bound to the SPI are put into the DEPRECATED state. uniquely bound to the SPI are put into the DEPRECATED state.
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 parameter are processed. For each Next, the locators in the LOCATOR_SET parameter are processed. For
locator listed in the LOCATOR parameter, check that the address each locator listed in the LOCATOR_SET parameter, check that the
therein is a legal unicast or anycast address. That is, the address address therein is a legal unicast or anycast address. That is, the
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 The below assumes that all locators are of Type "1" with a Traffic
Type of "0"; other cases are for further study. Type of "0"; other cases are for further study.
For each Type "1" address listed in the LOCATOR parameter, the host For each Type "1" address listed in the LOCATOR_SET parameter, the
checks whether the address is already bound to the SPI indicated. If host checks whether the address is already bound to the SPI
the address is already bound, its lifetime is updated. If the status indicated. If the address is already bound, its lifetime is updated.
of the address is DEPRECATED, the status is changed to UNVERIFIED. If the status of the address is DEPRECATED, the status is changed to
If the address is not already bound, the address is added, and its UNVERIFIED. If the address is not already bound, the address is
status is set to UNVERIFIED. Mark all addresses corresponding to the added, and its status is set to UNVERIFIED. Mark all addresses
SPI that were NOT listed in the LOCATOR parameter as DEPRECATED. corresponding to the SPI that were NOT listed in the LOCATOR_SET
parameter as DEPRECATED.
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 parameter have either a state of UNVERIFIED or ACTIVE, and LOCATOR_SET parameter have either a state of UNVERIFIED or ACTIVE,
any old addresses on the old SA not listed in the LOCATOR parameter and any old addresses on the old SA not listed in the LOCATOR_SET
have a state of DEPRECATED. parameter have a state of DEPRECATED.
Once the host has processed the locators, if the LOCATOR parameter Once the host has processed the locators, if the LOCATOR_SET
contains a new Preferred locator, the host SHOULD initiate a change parameter contains a new Preferred locator, the host SHOULD initiate
of the Preferred locator. This requires that the host first verifies a change of the Preferred locator. This requires that the host first
reachability of the associated address, and only then changes the verifies reachability of the associated address, and only then
Preferred locator; see Section 6.4. changes the Preferred locator; see Section 6.4.
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 locator with an unsupported Locator Type is received in a LOCATOR_SET
parameter. parameter.
6.3. Verifying Address Reachability 6.3. 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 6.4. 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 LOCATOR become unreachable. Another reason may be due to receiving a
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:
1. If the new Preferred locator has ACTIVE status, the Preferred 1. If the new Preferred locator has ACTIVE status, the Preferred
locator is changed and the procedure succeeds. locator is changed and the procedure succeeds.
2. If the new Preferred locator has UNVERIFIED status, the host 2. If the new Preferred locator has UNVERIFIED status, the host
starts to verify its reachability. The host SHOULD use a starts to verify its reachability. The host SHOULD use a
different locator listed as ACTIVE until address verification different locator listed as ACTIVE until address verification
skipping to change at page 20, line 19 skipping to change at page 18, line 7
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 7. Security Considerations
Security considerations are addressed in [I-D.ietf-hip-rfc5206-bis]. Security considerations are addressed in [I-D.ietf-hip-rfc5206-bis].
8. IANA Considerations 8. IANA Considerations
None. This document has no new IANA considerations.
9. Authors and Acknowledgments 9. 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.
10. References 10. References
10.1. Normative references 10.1. Normative references
[I-D.ietf-hip-rfc5201-bis] [I-D.ietf-hip-rfc5201-bis]
Moskowitz, R., Heer, T., Jokela, P., and T. Henderson, Moskowitz, R., Heer, T., Jokela, P., and T. Henderson,
"Host Identity Protocol Version 2 (HIPv2)", draft-ietf- "Host Identity Protocol Version 2 (HIPv2)", draft-ietf-
hip-rfc5201-bis-14 (work in progress), October 2013. hip-rfc5201-bis-20 (work in progress), October 2014.
[I-D.ietf-hip-rfc5202-bis] [I-D.ietf-hip-rfc5202-bis]
Jokela, P., Moskowitz, R., and J. Melen, "Using the 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)", draft-ietf-hip- the Host Identity Protocol (HIP)", draft-ietf-hip-
rfc5202-bis-05 (work in progress), November 2013. rfc5202-bis-07 (work in progress), September 2014.
[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-06 the Host Identity Protocol", draft-ietf-hip-rfc5206-bis-07
(work in progress), July 2013. (work in progress), December 2014.
[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, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3484] Draves, R., "Default Address Selection for Internet [RFC3484] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", RFC 3484, February 2003. Protocol version 6 (IPv6)", RFC 3484, February 2003.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC
4303, December 2005.
10.2. Informative references 10.2. Informative references
[I-D.ietf-hip-rfc4423-bis] [I-D.ietf-hip-rfc4423-bis]
Moskowitz, R. and M. Komu, "Host Identity Protocol Moskowitz, R. and M. Komu, "Host Identity Protocol
Architecture", draft-ietf-hip-rfc4423-bis-08 (work in Architecture", draft-ietf-hip-rfc4423-bis-09 (work in
progress), April 2014. progress), October 2014.
[I-D.ietf-hip-rfc5204-bis] [I-D.ietf-hip-rfc5204-bis]
Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extension", draft-ietf-hip-rfc5204-bis-04 (work Rendezvous Extension", draft-ietf-hip-rfc5204-bis-05 (work
in progress), June 2014. in progress), December 2014.
[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, June 2009. Shim Protocol for IPv6", RFC 5533, June 2009.
Appendix A. Document Revision History Appendix A. Document Revision History
To be removed upon publication To be removed upon publication
+----------+--------------------------------------------------------+ +----------+--------------------------------------------------------+
| Revision | Comments | | Revision | Comments |
skipping to change at page 22, line 22 skipping to change at page 20, line 22
| draft-00 | Initial version with multihoming text imported from | | draft-00 | Initial version with multihoming text imported from |
| | RFC5206. | | | RFC5206. |
| | | | | |
| draft-01 | Document refresh; no other changes. | | draft-01 | Document refresh; no other changes. |
| | | | | |
| draft-02 | Document refresh; no other changes. | | draft-02 | Document refresh; no other changes. |
| | | | | |
| draft-03 | Document refresh; no other changes. | | draft-03 | Document refresh; no other changes. |
| | | | | |
| draft-04 | Document refresh; no other changes. | | draft-04 | Document refresh; no other changes. |
| | |
| draft-05 | Move remaining multihoming material from RFC5206-bis |
| | to this document |
| | |
| | Update lingering references to LOCATOR parameter to |
| | LOCATOR_SET |
+----------+--------------------------------------------------------+ +----------+--------------------------------------------------------+
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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