draft-ietf-hip-nat-traversal-09.txt   rfc5770.txt 
HIP Working Group M. Komu Internet Engineering Task Force (IETF) M. Komu
Internet-Draft HIIT Request for Comments: 5770 HIIT
Intended status: Experimental T. Henderson Category: Experimental T. Henderson
Expires: April 26, 2010 The Boeing Company ISSN: 2070-1721 The Boeing Company
H. Tschofenig H. Tschofenig
Nokia Siemens Networks Nokia Siemens Networks
J. Melen J. Melen
A. Keranen, Ed. A. Keranen, Ed.
Ericsson Research Nomadiclab Ericsson Research Nomadiclab
October 23, 2009 April 2010
Basic HIP Extensions for Traversal of Network Address Translators
draft-ietf-hip-nat-traversal-09.txt
Status of this Memo
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Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Basic Host Identity Protocol (HIP) Extensions for
Provisions Relating to IETF Documents in effect on the date of Traversal of Network Address Translators
publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
Abstract Abstract
This document specifies extensions to the Host Identity Protocol This document specifies extensions to the Host Identity Protocol
(HIP) to facilitate Network Address Translator (NAT) traversal. The (HIP) to facilitate Network Address Translator (NAT) traversal. The
extensions are based on the use of the Interactive Connectivity extensions are based on the use of the Interactive Connectivity
Establishment (ICE) methodology to discover a working path between Establishment (ICE) methodology to discover a working path between
two end-hosts, and on standard techniques for encapsulating two end-hosts, and on standard techniques for encapsulating
Encapsulating Security Payload (ESP) packets within the User Datagram Encapsulating Security Payload (ESP) packets within the User Datagram
Protocol (UDP). This document also defines elements of a procedure Protocol (UDP). This document also defines elements of a procedure
for NAT traversal, including the optional use of a HIP relay server. for NAT traversal, including the optional use of a HIP relay server.
With these extensions HIP is able to work in environments that have With these extensions HIP is able to work in environments that have
NATs and provides a generic NAT traversal solution to higher-layer NATs and provides a generic NAT traversal solution to higher-layer
networking applications. networking applications.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
evaluation.
This document defines an Experimental Protocol for the Internet
community. This document is a product of the Internet Engineering
Task Force (IETF). It represents the consensus of the IETF
community. It has received public review and has been approved for
publication by the Internet Engineering Steering Group (IESG). Not
all documents approved by the IESG are a candidate for any level of
Internet Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5770.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction ....................................................4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Terminology .....................................................6
3. Overview of Operation . . . . . . . . . . . . . . . . . . . . 7 3. Overview of Operation ...........................................7
4. Protocol Description . . . . . . . . . . . . . . . . . . . . . 8 4. Protocol Description ............................................8
4.1. Relay Registration . . . . . . . . . . . . . . . . . . . . 8 4.1. Relay Registration .........................................8
4.2. ICE Candidate Gathering . . . . . . . . . . . . . . . . . 10 4.2. ICE Candidate Gathering ...................................10
4.3. NAT Traversal Mode Negotiation . . . . . . . . . . . . . . 10 4.3. NAT Traversal Mode Negotiation ............................10
4.4. Connectivity Check Pacing Negotiation . . . . . . . . . . 12 4.4. Connectivity Check Pacing Negotiation .....................12
4.5. Base Exchange via HIP Relay Server . . . . . . . . . . . . 12 4.5. Base Exchange via HIP Relay Server ........................12
4.6. ICE Connectivity Checks . . . . . . . . . . . . . . . . . 15 4.6. ICE Connectivity Checks ...................................15
4.7. NAT Keepalives . . . . . . . . . . . . . . . . . . . . . . 15 4.7. NAT Keepalives ............................................16
4.8. Base Exchange without ICE Connectivity Checks . . . . . . 16 4.8. Base Exchange without ICE Connectivity Checks .............16
4.9. Initiating a Base Exchange both with and without UDP 4.9. Initiating a Base Exchange Both with and without
Encapsulation . . . . . . . . . . . . . . . . . . . . . . 17 UDP Encapsulation .........................................17
4.10. Sending Control Packets after the Base Exchange . . . . . 18 4.10. Sending Control Packets after the Base Exchange ..........18
5. Packet Formats . . . . . . . . . . . . . . . . . . . . . . . . 18 5. Packet Formats .................................................18
5.1. HIP Control Packets . . . . . . . . . . . . . . . . . . . 18 5.1. HIP Control Packets .......................................19
5.2. Connectivity Checks . . . . . . . . . . . . . . . . . . . 19 5.2. Connectivity Checks .......................................19
5.3. Keepalives . . . . . . . . . . . . . . . . . . . . . . . . 20 5.3. Keepalives ................................................20
5.4. NAT Traversal Mode Parameter . . . . . . . . . . . . . . . 20 5.4. NAT Traversal Mode Parameter ..............................21
5.5. Connectivity Check Transaction Pacing Parameter . . . . . 21 5.5. Connectivity Check Transaction Pacing Parameter ...........22
5.6. Relay and Registration Parameters . . . . . . . . . . . . 22 5.6. Relay and Registration Parameters .........................22
5.7. LOCATOR Parameter . . . . . . . . . . . . . . . . . . . . 23 5.7. LOCATOR Parameter .........................................23
5.8. RELAY_HMAC Parameter . . . . . . . . . . . . . . . . . . . 24 5.8. RELAY_HMAC Parameter ......................................25
5.9. Registration Types . . . . . . . . . . . . . . . . . . . . 24 5.9. Registration Types ........................................25
5.10. Notify Packet Types . . . . . . . . . . . . . . . . . . . 25 5.10. Notify Packet Types ......................................26
5.11. ESP Data Packets . . . . . . . . . . . . . . . . . . . . . 25 5.11. ESP Data Packets .........................................26
6. Security Considerations . . . . . . . . . . . . . . . . . . . 26 6. Security Considerations ........................................27
6.1. Privacy Considerations . . . . . . . . . . . . . . . . . . 26 6.1. Privacy Considerations ....................................27
6.2. Opportunistic Mode . . . . . . . . . . . . . . . . . . . . 26 6.2. Opportunistic Mode ........................................27
6.3. Base Exchange Replay Protection for HIP Relay Server . . . 26 6.3. Base Exchange Replay Protection for HIP Relay Server ......28
6.4. Demuxing Different HIP Associations . . . . . . . . . . . 27 6.4. Demuxing Different HIP Associations .......................28
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 7. IANA Considerations ............................................28
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 28 8. Contributors ...................................................29
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28 9. Acknowledgments ................................................29
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28 10. References ....................................................29
10.1. Normative References . . . . . . . . . . . . . . . . . . . 28 10.1. Normative References .....................................29
10.2. Informative References . . . . . . . . . . . . . . . . . . 29 10.2. Informative References ...................................30
Appendix A. Selecting a Value for Check Pacing . . . . . . . . . 30 Appendix A. Selecting a Value for Check Pacing ....................32
Appendix B. Base Exchange through a Rendezvous Server . . . . . . 31 Appendix B. Base Exchange through a Rendezvous Server .............33
Appendix C. Document Revision History . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31
1. Introduction 1. Introduction
HIP [RFC5201] is defined as a protocol that runs directly over IPv4 HIP [RFC5201] is defined as a protocol that runs directly over IPv4
or IPv6, and HIP coordinates the setup of ESP security associations or IPv6, and HIP coordinates the setup of ESP security associations
[RFC5202] that are also specified to run over IPv4 or IPv6. This [RFC5202] that are also specified to run over IPv4 or IPv6. This
approach is known to have problems traversing NATs and other approach is known to have problems traversing NATs and other
middleboxes [RFC5207]. This document defines HIP extensions for the middleboxes [RFC5207]. This document defines HIP extensions for the
traversal of both Network Address Translator (NAT) and Network traversal of both Network Address Translator (NAT) and Network
Address and Port Translator (NAPT) middleboxes. The document Address and Port Translator (NAPT) middleboxes. The document
skipping to change at page 4, line 27 skipping to change at page 4, line 27
though a recommended behavior is described in [RFC4787]. The HIP though a recommended behavior is described in [RFC4787]. The HIP
protocol extensions in this document make as few assumptions as protocol extensions in this document make as few assumptions as
possible about the behavior of the NAT devices so that NAT traversal possible about the behavior of the NAT devices so that NAT traversal
will work even with legacy NAT devices. The purpose of these will work even with legacy NAT devices. The purpose of these
extensions is to allow two HIP-enabled hosts to communicate with each extensions is to allow two HIP-enabled hosts to communicate with each
other even if one or both of the communicating hosts are in a network other even if one or both of the communicating hosts are in a network
that is behind one or more NATs. that is behind one or more NATs.
Using the extensions defined in this document, HIP end-hosts use Using the extensions defined in this document, HIP end-hosts use
techniques drawn from the Interactive Connectivity Establishment techniques drawn from the Interactive Connectivity Establishment
(ICE) methodology [I-D.ietf-mmusic-ice] to find operational paths for (ICE) methodology [RFC5245] to find operational paths for the HIP
the HIP control protocol and for ESP encapsulated data traffic. The control protocol and for ESP encapsulated data traffic. The hosts
hosts test connectivity between different locators and try to test connectivity between different locators and try to discover a
discover a direct end-to-end path between them. However, with some direct end-to-end path between them. However, with some legacy NATs,
legacy NATs, utilizing the shortest path between two end-hosts utilizing the shortest path between two end-hosts located behind NATs
located behind NATs is not possible without relaying the traffic is not possible without relaying the traffic through a relay, such as
through a relay, such as a TURN server [RFC5128]. Because relaying a Traversal Using Relay NAT (TURN) server [RFC5128]. Because
traffic increases the roundtrip delay and consumes resources from the relaying traffic increases the roundtrip delay and consumes resources
relay, with the extensions described in this document, hosts try to from the relay, with the extensions described in this document, hosts
avoid using the TURN server whenever possible. try to avoid using the TURN server whenever possible.
HIP has defined a Rendezvous Server [RFC5204] to allow for mobile HIP HIP has defined a rendezvous server [RFC5204] to allow for mobile HIP
hosts to establish a stable point-of-contact in the Internet. This hosts to establish a stable point-of-contact in the Internet. This
document defines extensions to the Rendezvous Server that solve the document defines extensions to the rendezvous server that solve the
same problems but for both NATed and non-NATed networks. The same problems, but for both NATed and non-NATed networks. The
extended Rendezvous Server, called a "HIP relay server", forwards HIP extended rendezvous server, called a "HIP relay server", forwards HIP
control packets between an Initiator and a Responder, allowing hosts control packets between an Initiator and a Responder, allowing hosts
to be located behind NATs. This behavior is in contrast to the HIP to be located behind NATs. This behavior is in contrast to the HIP
rendezvous service that forwards only the initial I1 packet of the rendezvous service that forwards only the initial I1 packet of the
base exchange; an approach which is less likely to work in a NATed base exchange; an approach that is less likely to work in a NATed
environment [RFC5128]. Therefore, when using relays to traverse environment [RFC5128]. Therefore, when using relays to traverse
NATs, HIP uses a HIP relay server for the control traffic and a TURN NATs, HIP uses a HIP relay server for the control traffic and a TURN
server for the data traffic. server for the data traffic.
The basis for the connectivity checks is ICE [I-D.ietf-mmusic-ice]. The basis for the connectivity checks is ICE [RFC5245]. [RFC5245]
[I-D.ietf-mmusic-ice] describes ICE as follows: describes ICE as follows:
"The Interactive Connectivity Establishment (ICE) methodology is a A technique for NAT traversal for UDP-based media streams (though
technique for NAT traversal for UDP-based media streams (though
ICE can be extended to handle other transport protocols, such as ICE can be extended to handle other transport protocols, such as
TCP) established by the offer/answer model. ICE is an extension TCP) established by the offer/answer model. ICE is an extension
to the offer/answer model, and works by including a multiplicity to the offer/answer model, and works by including a multiplicity
of IP addresses and ports in SDP offers and answers, which are of IP addresses and ports in SDP offers and answers, which are
then tested for connectivity by peer-to-peer connectivity checks. then tested for connectivity by peer-to-peer connectivity checks.
The IP addresses and ports included in the SDP and the The IP addresses and ports included in the SDP and the
connectivity checks are performed using the revised STUN connectivity checks are performed using the revised [Simple
specification [RFC5389], now renamed to Session Traversal Traversal of the UDP Protocol through NAT (STUN)] specification
Utilities for NAT." [RFC5389], now renamed to Session Traversal Utilities for NAT.
The standard ICE [I-D.ietf-mmusic-ice] is specified with SIP in mind The standard ICE [RFC5245] is specified with SIP in mind and it has
and it has some features that are not necessary or suitable as such some features that are not necessary or suitable as such for other
for other protocols. [I-D.rosenberg-mmusic-ice-nonsip] gives protocols. [MMUSIC-ICE] gives instructions and recommendations on
instructions and recommendations on how ICE can be used for other how ICE can be used for other protocols and this document follows
protocols and this document follows those guidelines. those guidelines.
Two HIP hosts that implement this specification communicate their Two HIP hosts that implement this specification communicate their
locators to each other in the HIP base exchange. The locators are locators to each other in the HIP base exchange. The locators are
then paired with the locators of the other endpoint and prioritized then paired with the locators of the other endpoint and prioritized
according to recommended and local policies. These locator pairs are according to recommended and local policies. These locator pairs are
then tested sequentially by both of the end hosts. The tests may then tested sequentially by both of the end-hosts. The tests may
result in multiple operational pairs but ICE procedures determine a result in multiple operational pairs but ICE procedures determine a
single preferred address pair to be used for subsequent single preferred address pair to be used for subsequent
communication. communication.
In summary, the extensions in this document define: In summary, the extensions in this document define:
o UDP encapsulation of HIP packets o UDP encapsulation of HIP packets
o UDP encapsulation of IPsec ESP packets o UDP encapsulation of IPsec ESP packets
skipping to change at page 6, line 12 skipping to change at page 6, line 12
o a number of optimizations (such as when the ICE connectivity tests o a number of optimizations (such as when the ICE connectivity tests
can be omitted) can be omitted)
2. Terminology 2. Terminology
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 [RFC2119]. document are to be interpreted as described in [RFC2119].
This document borrows terminology from [RFC5201], [RFC5206], This document borrows terminology from [RFC5201], [RFC5206],
[RFC4423], [I-D.ietf-mmusic-ice], and [RFC5389]. Additionally, the [RFC4423], [RFC5245], and [RFC5389]. Additionally, the following
following terms are used: terms are used:
Rendezvous server: Rendezvous server:
A host that forwards I1 packets to the Responder. A host that forwards I1 packets to the Responder.
HIP relay server: HIP relay server:
A host that forwards any kind of HIP control packets between the A host that forwards any kind of HIP control packets between the
Initiator and the Responder. Initiator and the Responder.
TURN server: TURN server:
A server that forwards data traffic between two end-hosts as A server that forwards data traffic between two end-hosts as
defined in [I-D.ietf-behave-turn]. defined in [RFC5766].
Locator: Locator:
As defined in [RFC5206]: "A name that controls how the packet is As defined in [RFC5206]: "A name that controls how the packet is
routed through the network and demultiplexed by the end-host. It routed through the network and demultiplexed by the end-host. It
may include a concatenation of traditional network addresses such may include a concatenation of traditional network addresses such
as an IPv6 address and end-to-end identifiers such as an ESP SPI. 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 It may also include transport port numbers or IPv6 Flow Labels as
demultiplexing context, or it may simply be a network address." demultiplexing context, or it may simply be a network address."
LOCATOR (written in capital letters): LOCATOR (written in capital letters):
skipping to change at page 7, line 43 skipping to change at page 7, line 43
+-------+ +-------+ +-------+ +-------+
| NAT | | NAT | | NAT | | NAT |
+-------+ +-------+ +-------+ +-------+
/ \ / \
/ \ / \
+-------+ +-------+ +-------+ +-------+
| Init- | | Resp- | | Init- | | Resp- |
| iator | | onder | | iator | | onder |
+-------+ +-------+ +-------+ +-------+
Figure 1: Example network configuration Figure 1: Example Network Configuration
In an example configuration depicted in Figure 1, both Initiator and In the example configuration depicted in Figure 1, both Initiator and
Responder are behind one or more NATs, and both private networks are Responder are behind one or more NATs, and both private networks are
connected to the public Internet. To be contacted from behind a NAT, connected to the public Internet. To be contacted from behind a NAT,
the Responder must be registered with a HIP relay server reachable on the Responder must be registered with a HIP relay server reachable on
the public Internet, and we assume as a starting point that the the public Internet, and we assume, as a starting point, that the
Initiator knows both the Responder's HIT and the address of one of Initiator knows both the Responder's Host Identity Tag (HIT) and the
its relay servers (how the Initiator learns of the Responder's relay address of one of its relay servers (how the Initiator learns of the
server is outside of the scope of this document, but may be through Responder's relay server is outside of the scope of this document,
DNS or another name service). but may be through DNS or another name service).
The first steps are for both the Initiator and Responder to register The first steps are for both the Initiator and Responder to register
with a relay server (need not be the same one) and gather a set of with a relay server (need not be the same one) and gather a set of
address candidates. The hosts may use TURN and STUN servers for address candidates. The hosts may use TURN and STUN servers for
gathering the candidates. Next, the HIP base exchange is carried out gathering the candidates. Next, the HIP base exchange is carried out
by encapsulating the HIP control packets in UDP datagrams and sending by encapsulating the HIP control packets in UDP datagrams and sending
them through the Responder's relay server. As part of the base them through the Responder's relay server. As part of the base
exchange, each HIP host learns of the peer's candidate addresses exchange, each HIP host learns of the peer's candidate addresses
through the ICE offer/answer procedure embedded in the base exchange. through the ICE offer/answer procedure embedded in the base exchange.
skipping to change at page 9, line 6 skipping to change at page 9, line 6
4.1. Relay Registration 4.1. Relay Registration
HIP rendezvous servers operate in non-NATed environments and their HIP rendezvous servers operate in non-NATed environments and their
use is described in [RFC5204]. This section specifies a new use is described in [RFC5204]. This section specifies a new
middlebox extension, called the HIP relay server, for operating in middlebox extension, called the HIP relay server, for operating in
NATed environments. A HIP relay server forwards HIP control packets NATed environments. A HIP relay server forwards HIP control packets
between the Initiator and the Responder. between the Initiator and the Responder.
End-hosts cannot use the HIP relay service for forwarding the ESP End-hosts cannot use the HIP relay service for forwarding the ESP
data plane. Instead, they use TURN servers [I-D.ietf-behave-turn] data plane. Instead, they use TURN servers [RFC5766].
for that.
A HIP relay server MUST silently drop packets to a HIP relay client A HIP relay server MUST silently drop packets to a HIP relay client
that has not previously registered with the HIP relay. The that has not previously registered with the HIP relay. The
registration process follows the generic registration extensions registration process follows the generic registration extensions
defined in [RFC5203] and is illustrated in Figure 2. defined in [RFC5203] and is illustrated in Figure 2.
HIP HIP HIP HIP
Relay Relay Relay Relay
Client Server Client Server
| 1. UDP(I1) | | 1. UDP(I1) |
+------------------------------------------------------->| +------------------------------------------------------->|
| | | |
| 2. UDP(R1(REG_INFO(RELAY_UDP_HIP))) | | 2. UDP(R1(REG_INFO(RELAY_UDP_HIP))) |
|<-------------------------------------------------------+ |<-------------------------------------------------------+
| | | |
| 3. UDP(I2(REG_REQ(RELAY_UDP_HIP))) | | 3. UDP(I2(REG_REQ(RELAY_UDP_HIP))) |
+------------------------------------------------------->| +------------------------------------------------------->|
| | | |
| 4. UDP(R2(REG_RES(RELAY_UDP_HIP), REG_FROM)) | | 4. UDP(R2(REG_RES(RELAY_UDP_HIP), REG_FROM)) |
|<-------------------------------------------------------+ |<-------------------------------------------------------+
| |
Figure 2: Example Registration with a HIP Relay Figure 2: Example Registration with a HIP Relay
In step 1, the relay client (Initiator) starts the registration In step 1, the relay client (Initiator) starts the registration
procedure by sending an I1 packet over UDP. It is RECOMMENDED that procedure by sending an I1 packet over UDP. It is RECOMMENDED that
the Initiator selects a random port number from the ephemeral port the Initiator select a random port number from the ephemeral port
range 49152-65535 for initiating a base exchange. Alternatively, a range 49152-65535 for initiating a base exchange. Alternatively, a
host MAY also use a single fixed port for initiating all outgoing host MAY also use a single fixed port for initiating all outgoing
connections. However, the allocated port MUST be maintained until connections. However, the allocated port MUST be maintained until
all of the corresponding HIP Associations are closed. It is all of the corresponding HIP Associations are closed. It is
RECOMMENDED that the HIP relay server listens to incoming connections RECOMMENDED that the HIP relay server listen to incoming connections
at UDP port HIPPORT. If some other port number is used, it needs to at UDP port 10500. If some other port number is used, it needs to be
be communicated to possible Initiators. known by potential Initiators.
In step 2, the HIP relay server (Responder) lists the services that In step 2, the HIP relay server (Responder) lists the services that
it supports in the R1 packet. The support for HIP-over-UDP relaying it supports in the R1 packet. The support for HIP-over-UDP relaying
is denoted by the Registration Type value RELAY_UDP_HIP (see is denoted by the Registration Type value RELAY_UDP_HIP (see
Section 5.9). Section 5.9).
In step 3, the Initiator selects the services it registers for and In step 3, the Initiator selects the services for which it registers
lists them in the REG_REQ parameter. The Initiator registers for HIP and lists them in the REG_REQ parameter. The Initiator registers for
relay service by listing the RELAY_UDP_HIP value in the request HIP relay service by listing the RELAY_UDP_HIP value in the request
parameter. parameter.
In step 4, the Responder concludes the registration procedure with an In step 4, the Responder concludes the registration procedure with an
R2 packet and acknowledges the registered services in the REG_RES R2 packet and acknowledges the registered services in the REG_RES
parameter. The Responder denotes unsuccessful registrations (if any) parameter. The Responder denotes unsuccessful registrations (if any)
in the REG_FAILED parameter of R2. The Responder also includes a in the REG_FAILED parameter of R2. The Responder also includes a
REG_FROM parameter that contains the transport address of the client REG_FROM parameter that contains the transport address of the client
as observed by the relay (Server Reflexive candidate). After the as observed by the relay (Server Reflexive candidate). After the
registration, the client sends NAT keepalives periodically to the registration, the client sends NAT keepalives, as described in
relay to keep possible NAT bindings between the client and the relay Section 4.7, periodically to the relay to keep possible NAT bindings
alive. The relay client maintains the HIP association with the relay between the client and the relay alive. The relay client maintains
server as long as it requires relaying service from it. the HIP association with the relay server as long as it requires
relaying service from it.
4.2. ICE Candidate Gathering 4.2. ICE Candidate Gathering
If a host is going to use ICE, it needs to gather a set of address If a host is going to use ICE, it needs to gather a set of address
candidates. The candidate gathering SHOULD be done as defined in candidates. The candidate gathering SHOULD be done as defined in
Section 4.1 of [I-D.ietf-mmusic-ice]. Candidates need to be gathered Section 4.1 of [RFC5245]. Candidates need to be gathered for the
for the UDP encapsulated flow of HIP and ESP traffic. This flow UDP-encapsulated flow of HIP and ESP traffic. This flow corresponds
corresponds to one ICE media stream and component. Since ICE to one ICE media stream and component. Since ICE component IDs are
component IDs are not needed, they are not explicitly signaled and ID not needed, they are not explicitly signaled and ID value of 1 SHOULD
value of 1 SHOULD be used for ICE processing, where needed. The be used for ICE processing, where needed. The Initiator takes the
Initiator takes the role of the ICE controlling agent. role of the ICE controlling agent.
The candidate gathering can be done at any time, but it needs to be The candidate gathering can be done at any time, but it needs to be
done before sending an I2 or R2 in the base exchange if ICE is to be done before sending an I2 or R2 in the base exchange if ICE is to be
used for the connectivity checks. It is RECOMMENDED that all three used for the connectivity checks. It is RECOMMENDED that all three
types of candidates (host, server reflexive and relayed) are gathered types of candidates (host, server reflexive, and relayed) are
to maximize the probability of successful NAT traversal. However, if gathered to maximize the probability of successful NAT traversal.
no TURN server is used, and the host has only a single local IP However, if no TURN server is used, and the host has only a single
address to use, the host MAY use the local address as the only host local IP address to use, the host MAY use the local address as the
candidate and the address from the REG_FROM parameter discovered only host candidate and the address from the REG_FROM parameter
during the relay registration as a server reflexive candidate. In discovered during the relay registration as a server reflexive
this case, no further candidate gathering is needed. candidate. In this case, no further candidate gathering is needed.
4.3. NAT Traversal Mode Negotiation 4.3. NAT Traversal Mode Negotiation
This section describes the usage of a new non-critical parameter This section describes the usage of a new non-critical parameter
type. The presence of the parameter in a HIP base exchange means type. The presence of the parameter in a HIP base exchange means
that the end-host supports NAT traversal extensions described in this that the end-host supports NAT traversal extensions described in this
document. As the parameter is non-critical (as defined in Section document. As the parameter is non-critical (as defined in Section
5.2.1 of [RFC5201]), it can be ignored by an end-host which means 5.2.1 of [RFC5201]), it can be ignored by an end-host, which means
that the host does not support or is not willing to use these that the host does not support or is not willing to use these
extensions. extensions.
With registration with a HIP relay it is usually sufficient to use With registration with a HIP relay, it is usually sufficient to use
UDP-ENCAPSULATION mode of NAT traversal since the relay should not be the UDP-ENCAPSULATION mode of NAT traversal since the relay is
behind a NAT. Thus, the relay SHOULD propose the UDP-ENCAPSULATION assumed to be in public address space. Thus, the relay SHOULD
mode as the preferred or only mode. The NAT traversal mode propose the UDP-ENCAPSULATION mode as the preferred or only mode.
negotiation in a HIP base exchange is illustrated in Figure 3.
The NAT traversal mode negotiation in a HIP base exchange is
illustrated in Figure 3.
Initiator Responder Initiator Responder
| 1. UDP(I1) | | 1. UDP(I1) |
+--------------------------------------------------------------->| +--------------------------------------------------------------->|
| | | |
| 2. UDP(R1(.., NAT_TRAVERSAL_MODE(list of modes), ..)) | | 2. UDP(R1(.., NAT_TRAVERSAL_MODE(list of modes), ..)) |
|<---------------------------------------------------------------+ |<---------------------------------------------------------------+
| | | |
| 3. UDP(I2(.., NAT_TRAVERSAL_MODE(selected mode), LOCATOR, ..)) | | 3. UDP(I2(.., NAT_TRAVERSAL_MODE(selected mode), LOCATOR, ..)) |
+--------------------------------------------------------------->| +--------------------------------------------------------------->|
skipping to change at page 11, line 25 skipping to change at page 11, line 28
| 4. UDP(R2(.., LOCATOR, ..)) | | 4. UDP(R2(.., LOCATOR, ..)) |
|<---------------------------------------------------------------+ |<---------------------------------------------------------------+
| | | |
Figure 3: Negotiation of NAT Traversal Mode Figure 3: Negotiation of NAT Traversal Mode
In step 1, the Initiator sends an I1 to the Responder. In step 2, In step 1, the Initiator sends an I1 to the Responder. In step 2,
the Responder responds with an R1. The NAT_TRAVERSAL_MODE parameter the Responder responds with an R1. The NAT_TRAVERSAL_MODE parameter
in R1 contains a list of NAT traversal modes the Responder supports. in R1 contains a list of NAT traversal modes the Responder supports.
The modes specified in this document are shown in Table 1 and their The modes specified in this document are shown in Table 1 and their
values in Section 5.4. values are specified in Section 5.4.
+-------------------+-----------------------------------------------+ +-------------------+-----------------------------------------------+
| Type | Purpose | | Type | Purpose |
+-------------------+-----------------------------------------------+ +-------------------+-----------------------------------------------+
| RESERVED | Reserved for future use | | RESERVED | Reserved for future use |
| | |
| UDP-ENCAPSULATION | Use only UDP encapsulation of the HIP | | UDP-ENCAPSULATION | Use only UDP encapsulation of the HIP |
| | signaling traffic and ESP (no ICE | | | signaling traffic and ESP (no ICE |
| | connectivity checks) | | | connectivity checks) |
| | |
| ICE-STUN-UDP | UDP-encapsulated control and data traffic | | ICE-STUN-UDP | UDP-encapsulated control and data traffic |
| | with ICE-based connectivity checks using STUN | | | with ICE-based connectivity checks using STUN |
| | messages | | | messages |
+-------------------+-----------------------------------------------+ +-------------------+-----------------------------------------------+
Table 1: NAT Traversal Modes Table 1: NAT Traversal Modes
In step 3, the Initiator sends an I2 that includes a In step 3, the Initiator sends an I2 that includes a
NAT_TRAVERSAL_MODE parameter. It contains the mode selected by the NAT_TRAVERSAL_MODE parameter. It contains the mode selected by the
Initiator from the list of modes offered by the Responder. If ICE Initiator from the list of modes offered by the Responder. If ICE
mode was selected, the I2 also includes the "Transport address" mode was selected, the I2 also includes the "Transport address"
locators (as defined in Section 5.7) of the Initiator in a LOCATOR locators (as defined in Section 5.7) of the Initiator in a LOCATOR
parameter. The locators in I2 are the "ICE offer". parameter. The locators in I2 are the "ICE offer".
In step 4, the Responder concludes the base exchange with an R2 In step 4, the Responder concludes the base exchange with an R2
packet. If the Initiator chose ICE NAT traversal mode, the Responder packet. If the Initiator chose ICE NAT traversal mode, the Responder
includes a LOCATOR parameter in the R2 packet. The locators in R2, includes a LOCATOR parameter in the R2 packet. The locators in R2,
encoded like the locators in I2, are the "ICE answer". If the NAT encoded like the locators in I2, are the "ICE answer". If the NAT
traversal mode selected by the Initiator is not supported by the traversal mode selected by the Initiator is not supported by the
Responder, the Responder SHOULD reply with NOTIFY packet with type Responder, the Responder SHOULD reply with a NOTIFY packet with type
NO_VALID_NAT_TRAVERSAL_MODE_PARAMETER and abort the base exchange. NO_VALID_NAT_TRAVERSAL_MODE_PARAMETER and abort the base exchange.
4.4. Connectivity Check Pacing Negotiation 4.4. Connectivity Check Pacing Negotiation
As explained in [I-D.ietf-mmusic-ice], when a NAT traversal mode with As explained in [RFC5245], when a NAT traversal mode with
connectivity checks is used, new transactions should not be started connectivity checks is used, new transactions should not be started
too fast to avoid congestion and overwhelming the NATs. too fast to avoid congestion and overwhelming the NATs.
For this purpose, during the base exchange, hosts can negotiate a For this purpose, during the base exchange, hosts can negotiate a
transaction pacing value, Ta, using a TRANSACTION_PACING parameter in transaction pacing value, Ta, using a TRANSACTION_PACING parameter in
R1 and I2 packets. The parameter contains the minimum time R1 and I2 packets. The parameter contains the minimum time
(expressed in milliseconds) the host would wait between two NAT (expressed in milliseconds) the host would wait between two NAT
traversal transactions, such as starting a new connectivity check or traversal transactions, such as starting a new connectivity check or
retrying a previous check. If a host does not include this parameter retrying a previous check. If a host does not include this parameter
in the base exchange, a Ta value of 500ms MUST be used as that host's in the base exchange, a Ta value of 500 ms MUST be used as that
minimum value. The value that is used by both of the hosts is the host's minimum value. The value that is used by both of the hosts is
higher out of the two offered values. the higher out of the two offered values.
Hosts SHOULD NOT use values smaller than 20ms for the minimum Ta, Hosts SHOULD NOT use values smaller than 20 ms for the minimum Ta,
since such values may not work well with some NATs, as explained in since such values may not work well with some NATs, as explained in
[I-D.ietf-mmusic-ice]. The Initiator MUST NOT propose a smaller [RFC5245]. The Initiator MUST NOT propose a smaller value than what
value than what the Responder offered. the Responder offered.
The minimum Ta value SHOULD be configurable, and if no value is The minimum Ta value SHOULD be configurable, and if no value is
configured, value of 500ms MUST be used. Guidelines for selecting a configured, a value of 500 ms MUST be used. Guidelines for selecting
Ta value are given in Appendix A. Currently this feature applies a Ta value are given in Appendix A. Currently this feature applies
only to the ICE-STUN-UDP NAT traversal mode, but any other mode using only to the ICE-STUN-UDP NAT traversal mode, but any other mode using
connectivity checks SHOULD utilize this feature. connectivity checks SHOULD utilize this feature.
4.5. Base Exchange via HIP Relay Server 4.5. Base Exchange via HIP Relay Server
This section describes how Initiator and Responder perform a base This section describes how the Initiator and Responder perform a base
exchange through a HIP relay server. The NAT traversal mode exchange through a HIP relay server. The NAT traversal mode
negotiation (denoted as NAT_TM in the example) was described in negotiation (denoted as NAT_TM in the example) was described in
Section 4.3 and is not repeated here. If a relay receives an R1 or Section 4.3 and is not repeated here. If a relay receives an R1 or
I2 packet without the NAT traversal mode parameter, it MUST drop it I2 packet without the NAT traversal mode parameter, it MUST drop it
and SHOULD send a NOTIFY error packet with type and SHOULD send a NOTIFY error packet with type
NO_VALID_NAT_TRAVERSAL_MODE_PARAMETER to the sender of the R1/I2. NO_VALID_NAT_TRAVERSAL_MODE_PARAMETER to the sender of the R1/I2.
It is RECOMMENDED that the Initiator sends an I1 packet encapsulated It is RECOMMENDED that the Initiator send an I1 packet encapsulated
in UDP when it is destined to an IPv4 address of the Responder. in UDP when it is destined to an IPv4 address of the Responder.
Respectively, the Responder MUST respond to such an I1 packet with a Respectively, the Responder MUST respond to such an I1 packet with a
UDP-encapsulated R1 packet and the rest of the base exchange, I2 and UDP-encapsulated R1 packet and the rest of the base exchange, I2 and
R2, MUST also use UDP encapsulation. R2, MUST also use UDP encapsulation.
I HIP relay R Initiator HIP relay Responder
| 1. UDP(I1) | | | 1. UDP(I1) | |
+----------------------------->| 2. UDP(I1(RELAY_FROM)) | +----------------------------->| 2. UDP(I1(RELAY_FROM)) |
| +------------------------------->| | +------------------------------->|
| | | | | |
| | 3. UDP(R1(RELAY_TO, NAT_TM)) | | | 3. UDP(R1(RELAY_TO, NAT_TM)) |
| 4. UDP(R1(RELAY_TO, NAT_TM)) |<-------------------------------+ | 4. UDP(R1(RELAY_TO, NAT_TM)) |<-------------------------------+
|<-----------------------------+ | |<-----------------------------+ |
| | | | | |
| 5. UDP(I2(LOCATOR, NAT_TM)) | | | 5. UDP(I2(LOCATOR, NAT_TM)) | |
+----------------------------->| 6. UDP(I2(LOCATOR, RELAY_FROM, | +----------------------------->| 6. UDP(I2(LOCATOR, RELAY_FROM, |
skipping to change at page 13, line 34 skipping to change at page 13, line 40
Figure 4: Base Exchange via a HIP Relay Server Figure 4: Base Exchange via a HIP Relay Server
In step 1 of Figure 4, the Initiator sends an I1 packet over the In step 1 of Figure 4, the Initiator sends an I1 packet over the
transport layer to the HIT of the Responder and IP address and port transport layer to the HIT of the Responder and IP address and port
of the HIP relay server. The source address is one of the locators of the HIP relay server. The source address is one of the locators
of the Initiator. of the Initiator.
In step 2, the HIP relay server receives the I1 packet. If the In step 2, the HIP relay server receives the I1 packet. If the
destination HIT belongs to a registered Responder, the relay destination HIT belongs to a registered Responder, the relay
processes the packet. Otherwise, the relay MUST drop the packet processes the packet. Otherwise, the relay MUST drop the packet
silently. The relay appends a RELAY_FROM parameter to the I1 packet silently. The relay appends a RELAY_FROM parameter to the I1 packet,
which contains the transport source address and port of the I1 as which contains the transport source address and port of the I1 as
observed by the relay. The relay protects the I1 packet with observed by the relay. The relay protects the I1 packet with
RELAY_HMAC as described in [RFC5204], except that the parameter type RELAY_HMAC as described in [RFC5204], except that the parameter type
is different (see Section 5.8). The relay changes the source and is different (see Section 5.8). The relay changes the source and
destination ports and IP addresses of the packet to match the values destination ports and IP addresses of the packet to match the values
the Responder used when registering to the relay, i.e., the reverse the Responder used when registering to the relay, i.e., the reverse
of the R2 used in the registration. The relay MUST recalculate the of the R2 used in the registration. The relay MUST recalculate the
transport checksum and forward the packet to the Responder. transport checksum and forward the packet to the Responder.
In step 3, the Responder receives the I1 packet. The Responder In step 3, the Responder receives the I1 packet. The Responder
skipping to change at page 15, line 15 skipping to change at page 15, line 21
4.6. ICE Connectivity Checks 4.6. ICE Connectivity Checks
If a HIP relay server was used, the Responder completes the base If a HIP relay server was used, the Responder completes the base
exchange with the R2 packet through the relay. However, the exchange with the R2 packet through the relay. However, the
destination address the Initiator and Responder used for the base destination address the Initiator and Responder used for the base
exchange packets belongs to the HIP relay server. Therefore, that exchange packets belongs to the HIP relay server. Therefore, that
address MUST NOT be used as a destination for ESP traffic. Instead, address MUST NOT be used as a destination for ESP traffic. Instead,
if a NAT traversal mode with ICE connectivity checks was selected, if a NAT traversal mode with ICE connectivity checks was selected,
the Initiator and Responder MUST start the connectivity checks. the Initiator and Responder MUST start the connectivity checks.
Creating the check list for the ICE connectivity checks should be Creating the checklist for the ICE connectivity checks should be
performed as described in Section 5.7 of [I-D.ietf-mmusic-ice] performed as described in Section 5.7 of [RFC5245] bearing in mind
bearing in mind that only one media stream and component is needed that only one media stream and component is needed (so there will be
(so there will be only a single checklist and all candidates should only a single checklist and all candidates should have the same
have the same component ID value). The actual connectivity checks component ID value). The actual connectivity checks MUST be
MUST be performed as described in Section 7 of [I-D.ietf-mmusic-ice]. performed as described in Section 7 of [RFC5245]. Regular mode
Regular mode SHOULD be used for the candidate nomination. SHOULD be used for the candidate nomination. Section 5.2 defines the
Section 5.2 defines the details of the STUN control packets. As a details of the STUN control packets. As a result of the ICE
result of the ICE connectivity checks, ICE nominates a single connectivity checks, ICE nominates a single transport address pair to
transport address pair to be used if an operational address pair was be used if an operational address pair was found. The end-hosts MUST
found. The end-hosts MUST use this address pair for the ESP traffic. use this address pair for the ESP traffic.
The connectivity check messages MUST be paced by the value negotiated The connectivity check messages MUST be paced by the value negotiated
during the base exchange as described in Section 4.4. If neither one during the base exchange as described in Section 4.4. If neither one
of the hosts announced a minimum pacing value, value of 500ms MUST be of the hosts announced a minimum pacing value, a value of 500 ms MUST
used. be used.
For retransmissions, the RTO value should be calculated as follows: For retransmissions, the retransmission timeout (RTO) value SHOULD be
calculated as follows:
RTO = MAX (500ms, Ta * P) RTO = MAX (500ms, Ta * (Num-Waiting + Num-In-Progress))
In the RTO formula, Ta is the value used for the connectivity check In the RTO formula, Ta is the value used for the connectivity check
pacing and P is the number of pairs in the checklist when the pacing, Num-Waiting is the number of pairs in the checklist in the
connectivity checks begin. This is identical to the formula in "Waiting" state, and Num-In-Progress is the number of pairs in the
[I-D.ietf-mmusic-ice] if there is only one checklist. "In-Progress" state. This is identical to the formula in [RFC5245]
if there is only one checklist.
If the ICE connectivity checks failed, the hosts MUST NOT send ESP If the ICE connectivity checks failed, the hosts MUST NOT send ESP
traffic to each other but MAY continue communicating using HIP traffic to each other but MAY continue communicating using HIP
packets and the locators used for the base exchange. Also, the hosts packets and the locators used for the base exchange. Also, the hosts
SHOULD notify each other about the failure with a SHOULD notify each other about the failure with a
CONNECTIVITY_CHECKS_FAILED NOTIFY packet (see Section 5.10). CONNECTIVITY_CHECKS_FAILED NOTIFY packet (see Section 5.10).
4.7. NAT Keepalives 4.7. NAT Keepalives
To prevent NAT states from expiring, communicating hosts send To prevent NAT states from expiring, communicating hosts send
periodic keepalives to each other. HIP relay servers MAY refrain periodic keepalives to each other. HIP relay servers MAY refrain
from sending keepalives if it's known that they are not behind a from sending keepalives if it's known that they are not behind a
middlebox that requires keepalives. An end-host MUST send keepalives middlebox that requires keepalives. An end-host MUST send keepalives
every 15 seconds to refresh the UDP port mapping at the NAT(s) when every 15 seconds to refresh the UDP port mapping at the NAT(s) when
the control or data channel is idle. To implement failure tolerance, the control or data channel is idle. To implement failure tolerance,
an end-host SHOULD have shorter keepalive period. an end-host SHOULD have a shorter keepalive period.
The keepalives are STUN Binding Indications if the hosts have agreed The keepalives are STUN Binding Indications if the hosts have agreed
on ICE-STUN-UDP NAT traversal mode during the base exchange. on ICE-STUN-UDP NAT traversal mode during the base exchange.
Otherwise, HIP NOTIFY packets MAY be used as keepalives. Otherwise, HIP NOTIFY packets MAY be used as keepalives.
The communicating hosts MUST send keepalives to each other using the The communicating hosts MUST send keepalives to each other using the
transport locators they agreed to use for data and signaling when transport locators they agreed to use for data and signaling when
they are in ESTABLISHED state. Also, the Initiator MUST send a they are in the ESTABLISHED state. Also, the Initiator MUST send a
NOTIFY packet to the relay to keep the NAT states alive on the path NOTIFY packet to the relay to keep the NAT states alive on the path
between the Initiator and relay when the Initiator has not received between the Initiator and relay when the Initiator has not received
any response to its I1 or I2 from the Responder in 15 seconds. any response to its I1 or I2 from the Responder in 15 seconds.
4.8. Base Exchange without ICE Connectivity Checks 4.8. Base Exchange without ICE Connectivity Checks
In certain network environments the ICE connectivity checks can be In certain network environments, the ICE connectivity checks can be
omitted to reduce initial connection set up latency because a base omitted to reduce initial connection set-up latency because a base
exchange acts as an implicit connectivity test itself. For this to exchange acts as an implicit connectivity test itself. For this to
work, the Initiator MUST be able to reach the Responder by simply UDP work, the Initiator MUST be able to reach the Responder by simply UDP
encapsulating HIP and ESP packets sent to the Responder's address. encapsulating HIP and ESP packets sent to the Responder's address.
Detecting and configuring this particular scenario is prone to Detecting and configuring this particular scenario is prone to
failure unless carefully planned. failure unless carefully planned.
In such a scenario, the Responder MAY include UDP-ENCAPSULATION NAT In such a scenario, the Responder MAY include UDP-ENCAPSULATION NAT
traversal mode as one of the supported modes in the R1 packet. If traversal mode as one of the supported modes in the R1 packet. If
the Responder has registered to a HIP relay server, it MUST also the Responder has registered to a HIP relay server, it MUST also
include a LOCATOR parameter in R1 that contains a preferred address include a LOCATOR parameter in R1 that contains a preferred address
where the Responder is able to receive UDP-encapsulated ESP and HIP where the Responder is able to receive UDP-encapsulated ESP and HIP
packets. This locator MUST be of type "Transport address", its packets. This locator MUST be of type "Transport address", its
Traffic type MUST be "both" and it MUST have the "Preferred bit" set Traffic type MUST be "both", and it MUST have the "Preferred bit" set
(see Table 2). If there is no such locator in R1, the source address (see Table 2). If there is no such locator in R1, the source address
of R1 is used as the Responder's preferred address. of R1 is used as the Responder's preferred address.
The Initiator MAY choose the UDP-ENCAPSULATION mode if the Responder The Initiator MAY choose the UDP-ENCAPSULATION mode if the Responder
listed it in the supported modes and the Initiator does not wish to listed it in the supported modes and the Initiator does not wish to
use ICE for searching for a more optimal path. In this case, the use ICE for searching for a more optimal path. In this case, the
Initiator sends the I2 with UDP-ENCAPSULATION mode in the NAT Initiator sends the I2 with UDP-ENCAPSULATION mode in the NAT
traversal mode parameter directly to the Responder's preferred traversal mode parameter directly to the Responder's preferred
address (i.e., to the preferred locator in R1 or to the address where address (i.e., to the preferred locator in R1 or to the address where
R1 was received from if there was no preferred locator in R1). The R1 was received from if there was no preferred locator in R1). The
skipping to change at page 17, line 10 skipping to change at page 17, line 24
ENCAPSULATION NAT traversal mode. Instead, if R2 and I2 are received ENCAPSULATION NAT traversal mode. Instead, if R2 and I2 are received
and processed successfully, a security association can be created and and processed successfully, a security association can be created and
UDP-encapsulated ESP can be exchanged between the hosts after the UDP-encapsulated ESP can be exchanged between the hosts after the
base exchange completes. However, the Responder SHOULD NOT send any base exchange completes. However, the Responder SHOULD NOT send any
ESP to the Initiator's address before it has received data from the ESP to the Initiator's address before it has received data from the
Initiator, as specified in Sections 4.4.2. and 6.9 of [RFC5201] and Initiator, as specified in Sections 4.4.2. and 6.9 of [RFC5201] and
in Sections 3.2.9 and 5.4 of [RFC5206]. in Sections 3.2.9 and 5.4 of [RFC5206].
Since an I2 packet with UDP-ENCAPSULATION NAT traversal mode selected Since an I2 packet with UDP-ENCAPSULATION NAT traversal mode selected
MUST NOT be sent via a relay, the Responder SHOULD reject such I2 MUST NOT be sent via a relay, the Responder SHOULD reject such I2
packets and reply with NO_VALID_NAT_TRAVERSAL_MODE_PARAMETER NOTIFY packets and reply with a NO_VALID_NAT_TRAVERSAL_MODE_PARAMETER NOTIFY
packet (see Section 5.10). packet (see Section 5.10).
If there is no answer for the I2 packet sent directly to the If there is no answer for the I2 packet sent directly to the
Responder's preferred address, the Initiator MAY send another I2 via Responder's preferred address, the Initiator MAY send another I2 via
the HIP relay server, but it MUST NOT choose UDP-ENCAPSULATION NAT the HIP relay server, but it MUST NOT choose UDP-ENCAPSULATION NAT
traversal mode for that I2. traversal mode for that I2.
4.9. Initiating a Base Exchange both with and without UDP Encapsulation 4.9. Initiating a Base Exchange Both with and without UDP Encapsulation
The Initiator MAY also try to simultaneously perform a base exchange The Initiator MAY also try to simultaneously perform a base exchange
with the Responder without UDP encapsulation. In such a case, the with the Responder without UDP encapsulation. In such a case, the
Initiator sends two I1 packets, one without and one with UDP Initiator sends two I1 packets, one without and one with UDP
encapsulation, to the Responder. The Initiator MAY wait for a while encapsulation, to the Responder. The Initiator MAY wait for a while
before sending the other I1. How long to wait and in which order to before sending the other I1. How long to wait and in which order to
send the I1 packets can be decided based on local policy. For send the I1 packets can be decided based on local policy. For
retransmissions, the procedure is repeated. retransmissions, the procedure is repeated.
The I1 packet without UDP encapsulation may arrive directly, without The I1 packet without UDP encapsulation may arrive directly, without
skipping to change at page 17, line 48 skipping to change at page 18, line 17
the Responder has successfully registered with the rendezvous the Responder has successfully registered with the rendezvous
service, the middlebox follows rendezvous procedures in [RFC5204]. service, the middlebox follows rendezvous procedures in [RFC5204].
If the Initiator receives a NAT traversal mode parameter in R1 If the Initiator receives a NAT traversal mode parameter in R1
without UDP encapsulation, the Initiator MAY ignore this parameter without UDP encapsulation, the Initiator MAY ignore this parameter
and send an I2 without UDP encapsulation and without any selected NAT and send an I2 without UDP encapsulation and without any selected NAT
traversal mode. When the Responder receives the I2 without UDP traversal mode. When the Responder receives the I2 without UDP
encapsulation and without NAT traversal mode, it will assume that no encapsulation and without NAT traversal mode, it will assume that no
NAT traversal mechanism is needed. The packet processing will be NAT traversal mechanism is needed. The packet processing will be
done as described in [RFC5201]. The Initiator MAY store the NAT done as described in [RFC5201]. The Initiator MAY store the NAT
traversal modes for future use e.g., in case of a mobility or traversal modes for future use, e.g., in case of a mobility or
multihoming event which causes NAT traversal to be used during the multihoming event that causes NAT traversal to be used during the
lifetime of the HIP association. lifetime of the HIP association.
4.10. Sending Control Packets after the Base Exchange 4.10. Sending Control Packets after the Base Exchange
After the base exchange, the end-hosts MAY send HIP control packets After the base exchange, the end-hosts MAY send HIP control packets
directly to each other using the transport address pair established directly to each other using the transport address pair established
for a data channel without sending the control packets through the for a data channel without sending the control packets through the
HIP relay server. When a host does not get acknowledgments, e.g., to HIP relay server. When a host does not get acknowledgments, e.g., to
an UPDATE or CLOSE packet after a timeout based on local policies, an UPDATE or CLOSE packet after a timeout based on local policies,
the host SHOULD resend the packet through the relay, if it was listed the host SHOULD resend the packet through the relay, if it was listed
skipping to change at page 18, line 30 skipping to change at page 18, line 46
RELAY_FROM parameter to the control packets it relays to the RELAY_FROM parameter to the control packets it relays to the
registered hosts. registered hosts.
If the HIP relay server is not willing or able to relay a HIP packet, If the HIP relay server is not willing or able to relay a HIP packet,
it MAY notify the sender of the packet with MESSAGE_NOT_RELAYED error it MAY notify the sender of the packet with MESSAGE_NOT_RELAYED error
notification (see Section 5.10). notification (see Section 5.10).
5. Packet Formats 5. Packet Formats
The following subsections define the parameter and packet encodings The following subsections define the parameter and packet encodings
for the HIP, ESP and ICE connectivity check packets. All values MUST for the HIP, ESP, and ICE connectivity check packets. All values
be in network byte order. MUST be in network byte order.
5.1. HIP Control Packets 5.1. HIP Control Packets
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port | Destination Port | | Source Port | Destination Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Checksum | | Length | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 32 bits of zeroes | | 32 bits of zeroes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
~ HIP Header and Parameters ~ ~ HIP Header and Parameters ~
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Format of UDP-encapsulated HIP Control Packets Figure 5: Format of UDP-Encapsulated HIP Control Packets
HIP control packets are encapsulated in UDP packets as defined in HIP control packets are encapsulated in UDP packets as defined in
Section 2.2 of [RFC3948], "rules for encapsulating IKE messages", Section 2.2 of [RFC3948], "IKE Header Format for Port 4500", except a
except a different port number is used. Figure 5 illustrates the different port number is used. Figure 5 illustrates the
encapsulation. The UDP header is followed by 32 zero bits that can encapsulation. The UDP header is followed by 32 zero bits that can
be used to differentiate HIP control packets from ESP packets. The be used to differentiate HIP control packets from ESP packets. The
HIP header and parameters follow the conventions of [RFC5201] with HIP header and parameters follow the conventions of [RFC5201] with
the exception that the HIP header checksum MUST be zero. The HIP the exception that the HIP header checksum MUST be zero. The HIP
header checksum is zero for two reasons. First, the UDP header header checksum is zero for two reasons. First, the UDP header
already contains a checksum. Second, the checksum definition in already contains a checksum. Second, the checksum definition in
[RFC5201] includes the IP addresses in the checksum calculation. The [RFC5201] includes the IP addresses in the checksum calculation. The
NATs unaware of HIP cannot recompute the HIP checksum after changing NATs unaware of HIP cannot recompute the HIP checksum after changing
IP addresses. IP addresses.
A HIP relay server or a Responder without a relay SHOULD listen at A HIP relay server or a Responder without a relay SHOULD listen at
UDP port HIPPORT for incoming UDP-encapsulated HIP control packets. UDP port 10500 for incoming UDP-encapsulated HIP control packets. If
some other port number is used, it needs to be known by potential
Initiators.
5.2. Connectivity Checks 5.2. Connectivity Checks
The connectivity checks are performed using STUN Binding Requests as The connectivity checks are performed using STUN Binding requests as
defined in [I-D.ietf-mmusic-ice]. This section describes the details defined in [RFC5245]. This section describes the details of the
of the parameters in the STUN messages. parameters in the STUN messages.
The Binding Requests MUST use STUN short term credentials with last The Binding requests MUST use STUN short-term credentials with the
32 bits of the HITs of the Initiator and Responder as the username last 32 bits of the HITs of the Initiator and Responder as the
fragments. The username is formed from the username fragments as username fragments. The username is formed from the username
defined in Section 7.1.1.3 of [I-D.ietf-mmusic-ice]. The 32 bit fragments as defined in Section 7.1.1.3 of [RFC5245]. The 32-bit
username fragments are expressed using lowercase hexadecimal ASCII username fragments are expressed using lowercase hexadecimal ASCII
characters. The leading zeroes MUST NOT be omitted so that the characters. The leading zeroes MUST NOT be omitted so that the
username's size is fixed (8 characters): for example, if the local username's size is fixed (8 characters); for example, if the local
HIT is 2001:15:8ebe:1aa7:42f5:b413:7237:6c0a and the remote HIT is HIT is 2001:15:8ebe:1aa7:42f5:b413:7237:6c0a and the remote HIT is
2001:18:46fa:97c0:ba5:cd77:51:47b, the local username would be 2001:18:46fa:97c0:ba5:cd77:51:47b, the local username would be
72376c0a and the remote username 0051047b. 72376c0a and the remote username 0051047b.
The STUN password is drawn from the DH keying material. Drawing of The STUN password is drawn from the Diffie-Hellman (DH) keying
HIP keys is defined in [RFC5201] Section 6.5 and drawing of ESP keys material. Drawing of HIP keys is defined in [RFC5201], Section 6.5
in [RFC5202] Section 7. Correspondingly, the hosts MUST draw and drawing of ESP keys in [RFC5202], Section 7. Correspondingly,
symmetric keys for STUN according to [RFC5201] Section 6.5. The the hosts MUST draw symmetric keys for STUN according to [RFC5201],
hosts draw the STUN key after HIP keys, or after ESP keys if ESP Section 6.5. The hosts draw the STUN key after HIP keys, or after
transform was successfully negotiated in the base exchange. Both ESP keys if ESP transform was successfully negotiated in the base
hosts draw a 128 bit key from the DH keying material, express that in exchange. Both hosts draw a 128-bit key from the DH keying material,
hexadecimal ASCII format using only lowercase letters (resulting in express that in hexadecimal ASCII format using only lowercase letters
32 numbers or lowercase letters), and use that as both the local and (resulting in 32 numbers or lowercase letters), and use that as both
peer password. [RFC5389] describes how hosts use the password for the local and peer password. [RFC5389] describes how hosts use the
message integrity of STUN messages. password for message integrity of STUN messages.
Both the username and password are expressed in ASCII hexadecimal Both the username and password are expressed in ASCII hexadecimal
format to prevent the need to run them through SASLPrep as defined in format to prevent the need to run them through SASLPrep as defined in
[RFC5389]. [RFC5389].
The connectivity checks MUST contain PRIORITY attribute. They MAY The connectivity checks MUST contain the PRIORITY attribute. They
contain USE-CANDIDATE attribute as defined in Section 7.1.1.1 of MAY contain the USE-CANDIDATE attribute as defined in Section 7.1.1.1
[I-D.ietf-mmusic-ice]. of [RFC5245].
The Initiator is always in the controlling role during a base The Initiator is always in the controlling role during a base
exchange. When two hosts are initiating a connection to each other exchange. When two hosts are initiating a connection to each other
simultaneously, HIP state machine detects it and assigns the host simultaneously, the HIP state machine detects it and assigns the host
with the larger HIT as the Responder as explained in Sections 4.4.2 with the larger HIT as the Responder as explained in Sections 4.4.2
and 6.7 in [RFC5201]. Hence, the ICE-CONTROLLED and ICE-CONTROLLING and 6.7 in [RFC5201]. Hence, the ICE-CONTROLLED and ICE-CONTROLLING
attributes are not needed to resolve role conflicts. However, the attributes are not needed to resolve role conflicts. However, the
attributes SHOULD be added to the connectivity check messages to attributes SHOULD be added to the connectivity check messages to
ensure interoperability with different ICE stacks and they can be ensure interoperability with different ICE stacks, and they can be
safely ignored on received connectivity checks. safely ignored on received connectivity checks.
5.3. Keepalives 5.3. Keepalives
The keepalives for HIP associations that are created with ICE are The keepalives for HIP associations that are created with ICE are
STUN Binding Indications, as defined in [RFC5389]. In contrast to STUN Binding Indications, as defined in [RFC5389]. In contrast to
the UDP-encapsulated HIP header, the non-ESP-marker between the UDP the UDP-encapsulated HIP header, the non-ESP-marker between the UDP
header and the STUN header is excluded. Keepalives MUST contain the header and the STUN header is excluded. Keepalives MUST contain the
FINGERPRINT STUN attribute but SHOULD NOT contain any other STUN FINGERPRINT STUN attribute but SHOULD NOT contain any other STUN
attributes and SHOULD NOT utilize any authentication mechanism. STUN attributes and SHOULD NOT utilize any authentication mechanism. STUN
messages are demultiplexed from ESP and HIP control packets using the messages are demultiplexed from ESP and HIP control packets using the
STUN markers, such as the magic cookie value and the FINGERPRINT STUN markers, such as the magic cookie value and the FINGERPRINT
attribute. attribute.
Keepalives for HIP associations created without ICE are HIP control Keepalives for HIP associations created without ICE are HIP control
packets that have NOTIFY as the packet type. The keepalive NOTIFY packets that have NOTIFY as the packet type. The keepalive NOTIFY
packets do not contain any parameters. packets do not contain any parameters.
5.4. NAT Traversal Mode Parameter 5.4. NAT Traversal Mode Parameter
Format of the NAT_TRAVERSAL_MODE parameter is similar to the format The format of the NAT_TRAVERSAL_MODE parameter is similar to the
of the ESP_TRANSFORM parameter in [RFC5202] and is shown in Figure 6. format of the ESP_TRANSFORM parameter in [RFC5202] and is shown in
This specification defines traversal mode identifiers UDP- Figure 6. This specification defines traversal mode identifiers UDP-
ENCAPSULATION and ICE-STUN-UDP. The identifier RESERVED is reserved ENCAPSULATION and ICE-STUN-UDP. The identifier RESERVED is reserved
for future use. Future specifications may define more traversal for future use. Future specifications may define more traversal
modes. modes.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Mode ID #1 | | Reserved | Mode ID #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mode ID #2 | Mode ID #3 | | Mode ID #2 | Mode ID #3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mode ID #n | Padding | | Mode ID #n | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type [ TBD by IANA: 608 ] Type 608
Length length in octets, excluding Type, Length, and padding Length length in octets, excluding Type, Length, and padding
Reserved zero when sent, ignored when received Reserved zero when sent, ignored when received
Mode ID defines the proposed or selected NAT traversal mode(s) Mode ID defines the proposed or selected NAT traversal mode(s)
The following NAT traversal mode IDs are defined: The following NAT traversal mode IDs are defined:
ID name Value ID name Value
RESERVED 0 RESERVED 0
UDP-ENCAPSULATION 1 UDP-ENCAPSULATION 1
ICE-STUN-UDP 2 ICE-STUN-UDP 2
Figure 6: Format of the NAT_TRAVERSAL_MODE parameter Figure 6: Format of the NAT_TRAVERSAL_MODE Parameter
The sender of a NAT_TRAVERSAL_MODE parameter MUST make sure that The sender of a NAT_TRAVERSAL_MODE parameter MUST make sure that
there are no more than six (6) Mode IDs in one NAT_TRAVERSAL_MODE there are no more than six (6) Mode IDs in one NAT_TRAVERSAL_MODE
parameter. Conversely, a recipient MUST be prepared to handle parameter. Conversely, a recipient MUST be prepared to handle
received NAT traversal mode parameters that contain more than six received NAT traversal mode parameters that contain more than six
Mode IDs by accepting the first six Mode IDs and dropping the rest. Mode IDs by accepting the first six Mode IDs and dropping the rest.
The limited number of Mode IDs sets the maximum size of the The limited number of Mode IDs sets the maximum size of the
NAT_TRAVERSAL_MODE parameter. The modes MUST be in preference order, NAT_TRAVERSAL_MODE parameter. The modes MUST be in preference order,
most preferred mode(s) first. most preferred mode(s) first.
5.5. Connectivity Check Transaction Pacing Parameter 5.5. Connectivity Check Transaction Pacing Parameter
The TRANSACTION_PACING parameter shown in Figure 7 contains only the The TRANSACTION_PACING parameter shown in Figure 7 contains only the
connectivity check pacing value, expressed in milliseconds, as 32 bit connectivity check pacing value, expressed in milliseconds, as a 32-
unsigned integer. bit unsigned integer.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Min Ta | | Min Ta |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type [ TBD by IANA: 610 ] Type 610
Length 4 Length 4
Min Ta the minimum connectivity check transaction pacing Min Ta the minimum connectivity check transaction pacing
value the host would use value the host would use
Figure 7: Format of the TRANSACTION_PACING parameter Figure 7: Format of the TRANSACTION_PACING Parameter
5.6. Relay and Registration Parameters 5.6. Relay and Registration Parameters
Format of the REG_FROM, RELAY_FROM and RELAY_TO parameters is shown The format of the REG_FROM, RELAY_FROM, and RELAY_TO parameters is
in Figure 8. All parameters are identical except for the type. shown in Figure 8. All parameters are identical except for the type.
REG_FROM is the only parameter covered with the signature. REG_FROM is the only parameter covered with the signature.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port | Protocol | Reserved | | Port | Protocol | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| Address | | Address |
| | | |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type [ TBD by IANA: Type REG_FROM: 950
REG_FROM: 950 RELAY_FROM: 63998
RELAY_FROM: 63998 (2^16 - 2^11 + 2^9 - 2) RELAY_TO: 64002
RELAY_TO: 64002 (2^16 - 2^11 + 2^9 + 2) ]
Length 20 Length 20
Port transport port number; zero when plain IP is used Port transport port number; zero when plain IP is used
Protocol IANA assigned, Internet Protocol number. Protocol IANA assigned, Internet Protocol number.
17 for UDP, 0 for plain IP. 17 for UDP, 0 for plain IP
Reserved reserved for future use; zero when sent, ignored Reserved reserved for future use; zero when sent, ignored
when received when received
Address an IPv6 address or an IPv4 address in "IPv4-Mapped Address an IPv6 address or an IPv4 address in "IPv4-Mapped
IPv6 address" format IPv6 address" format
Figure 8: Format of the REG_FROM, RELAY_FROM and RELAY_TO parameters Figure 8: Format of the REG_FROM, RELAY_FROM, and RELAY_TO Parameters
REG_FROM contains the transport address and protocol where the HIP
relay server sees the registration coming from. RELAY_FROM contains REG_FROM contains the transport address and protocol from which the
the address where the relayed packet was received from by the relay HIP relay server sees the registration coming. RELAY_FROM contains
server and the protocol that was used. RELAY_TO contains same the address from which the relayed packet was received by the relay
information about the address where a packet should be forwarded to. server and the protocol that was used. RELAY_TO contains the same
information about the address to which a packet should be forwarded.
5.7. LOCATOR Parameter 5.7. LOCATOR Parameter
The generic LOCATOR parameter format is the same as in [RFC5206]. The generic LOCATOR parameter format is the same as in [RFC5206].
However, presenting ICE candidates requires a new locator type. The However, presenting ICE candidates requires a new locator type. The
generic and NAT traversal specific locator parameters are illustrated generic and NAT-traversal-specific locator parameters are illustrated
in Figure 9. in Figure 9.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Type | Locator Type | Locator Length| Reserved |P| | Traffic Type | Locator Type | Locator Length| Reserved |P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator Lifetime | | Locator Lifetime |
skipping to change at page 23, line 50 skipping to change at page 24, line 38
| Priority | | Priority |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SPI | | SPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address | | Address |
| | | |
| | | |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: LOCATOR parameter Figure 9: LOCATOR Parameter
The individual fields in the LOCATOR parameter are described in The individual fields in the LOCATOR parameter are described in
Table 2. Table 2.
+-----------+----------+--------------------------------------------+ +-----------+----------+--------------------------------------------+
| Field | Value(s) | Purpose | | Field | Value(s) | Purpose |
+-----------+----------+--------------------------------------------+ +-----------+----------+--------------------------------------------+
| Type | 193 | Parameter type | | Type | 193 | Parameter type |
| Length | Variable | Length in octets, excluding Type and | | Length | Variable | Length in octets, excluding Type and |
| | | Length fields and padding | | | | Length fields and padding |
skipping to change at page 24, line 28 skipping to change at page 25, line 25
| Locator | 7 | Length of the fields after Locator | | Locator | 7 | Length of the fields after Locator |
| Length | | Lifetime in 4-octet units | | Length | | Lifetime in 4-octet units |
| Reserved | 0 | Reserved for future extensions | | Reserved | 0 | Reserved for future extensions |
| Preferred | 0 or 1 | Set to 1 for a Locator in R1 if the | | Preferred | 0 or 1 | Set to 1 for a Locator in R1 if the |
| (P) bit | | Responder can use it for the rest of the | | (P) bit | | Responder can use it for the rest of the |
| | | base exchange, otherwise set to zero | | | | base exchange, otherwise set to zero |
| Locator | Variable | Locator lifetime in seconds | | Locator | Variable | Locator lifetime in seconds |
| Lifetime | | | | Lifetime | | |
| Transport | Variable | Transport layer port number | | Transport | Variable | Transport layer port number |
| Port | | | | Port | | |
| Transport | Variable | IANA Assigned, transport layer Internet | | Transport | Variable | IANA assigned, transport layer Internet |
| Protocol | | Protocol number. Currently only UDP (17) | | Protocol | | Protocol number. Currently only UDP (17) |
| | | is supported. | | | | is supported. |
| Kind | Variable | 0 for host, 1 for server reflexive, 2 for | | Kind | Variable | 0 for host, 1 for server reflexive, 2 for |
| | | peer reflexive or 3 for relayed address | | | | peer reflexive or 3 for relayed address |
| Priority | Variable | Locator's priority as described in | | Priority | Variable | Locator's priority as described in |
| | | [I-D.ietf-mmusic-ice] | | | | [RFC5245] |
| SPI | Variable | SPI value which the host expects to see in | | SPI | Variable | Security Parameter Index (SPI) value that |
| | | incoming ESP packets that use this locator | | | | the host expects to see in incoming ESP |
| | | packets that use this locator |
| Address | Variable | IPv6 address or an "IPv4-Mapped IPv6 | | Address | Variable | IPv6 address or an "IPv4-Mapped IPv6 |
| | | address" format IPv4 address [RFC4291] | | | | address" format IPv4 address [RFC4291] |
+-----------+----------+--------------------------------------------+ +-----------+----------+--------------------------------------------+
Table 2: Fields of the LOCATOR parameter Table 2: Fields of the LOCATOR Parameter
5.8. RELAY_HMAC Parameter 5.8. RELAY_HMAC Parameter
The RELAY_HMAC parameter value has the TLV type 65520 (2^16 - 2^5 + The RELAY_HMAC parameter value has the TLV type 65520. It has the
2^4). It has the same semantics as RVS_HMAC [RFC5204]. same semantics as RVS_HMAC [RFC5204].
5.9. Registration Types 5.9. Registration Types
The REG_INFO, REG_REQ, REG_RESP and REG_FAILED parameters contain The REG_INFO, REG_REQ, REG_RESP, and REG_FAILED parameters contain
Registration Type [RFC5203] values for HIP relay server registration. Registration Type [RFC5203] values for HIP relay server registration.
The value for RELAY_UDP_HIP is 2. The value for RELAY_UDP_HIP is 2.
5.10. Notify Packet Types 5.10. Notify Packet Types
A HIP relay server and end hosts can use NOTIFY packets to signal A HIP relay server and end-hosts can use NOTIFY packets to signal
different error conditions. The new Notify Packet Types [RFC5201] different error conditions. The new Notify Packet Types [RFC5201]
defined in this document are shown below [values TBD by IANA]. The defined in this document are shown below. The Notification Data
Notification Data field for the error notifications SHOULD contain field for the error notifications SHOULD contain the HIP header of
the HIP header of the rejected packet and SHOULD be empty for the the rejected packet and SHOULD be empty for the
CONNECTIVITY_CHECKS_FAILED type. CONNECTIVITY_CHECKS_FAILED type.
NOTIFICATION PARAMETER - ERROR TYPES Value NOTIFICATION PARAMETER - ERROR TYPES Value
------------------------------------ ----- ------------------------------------ -----
NO_VALID_NAT_TRAVERSAL_MODE_PARAMETER 60 NO_VALID_NAT_TRAVERSAL_MODE_PARAMETER 60
If a HIP relay server does not forward a base exchange packet due If a HIP relay server does not forward a base exchange packet due
to missing NAT traversal mode parameter, or the Initiator selects to missing NAT traversal mode parameter, or the Initiator selects
a NAT traversal mode that the Responder did not expect, the relay a NAT traversal mode that the Responder did not expect, the relay
or the Responder may send back a NOTIFY error packet with this or the Responder may send back a NOTIFY error packet with this
type. type.
CONNECTIVITY_CHECKS_FAILED 61 CONNECTIVITY_CHECKS_FAILED 61
Used by the end hosts to signal that NAT traversal connectivity Used by the end-hosts to signal that NAT traversal connectivity
checks failed and did not produce a working path. checks failed and did not produce a working path.
MESSAGE_NOT_RELAYED 62 MESSAGE_NOT_RELAYED 62
Used by a HIP relay server to signal that is was not able or Used by a HIP relay server to signal that is was not able or
willing to relay a HIP packet. willing to relay a HIP packet.
5.11. ESP Data Packets 5.11. ESP Data Packets
[RFC3948] describes UDP encapsulation of the IPsec ESP transport and [RFC3948] describes the UDP encapsulation of the IPsec ESP transport
tunnel mode. On the wire, the HIP ESP packets do not differ from the and tunnel mode. On the wire, the HIP ESP packets do not differ from
transport mode ESP and thus the encapsulation of the HIP ESP packets the transport mode ESP, and thus the encapsulation of the HIP ESP
is same as the UDP encapsulation transport mode ESP. However, the packets is same as the UDP encapsulation transport mode ESP.
(semantic) difference to BEET mode ESP packets used by HIP is that IP However, the (semantic) difference to Bound End-to-End Tunnel (BEET)
header is not used in BEET integrity protection calculation. mode ESP packets used by HIP is that IP header is not used in BEET
integrity protection calculation.
During the HIP base exchange, the two peers exchange parameters that During the HIP base exchange, the two peers exchange parameters that
enable them to define a pair of IPsec ESP security associations (SAs) enable them to define a pair of IPsec ESP security associations (SAs)
as described in [RFC5202]. When two peers perform a UDP-encapsulated as described in [RFC5202]. When two peers perform a UDP-encapsulated
base exchange, they MUST define a pair of IPsec SAs that produces base exchange, they MUST define a pair of IPsec SAs that produces
UDP-encapsulated ESP data traffic. UDP-encapsulated ESP data traffic.
The management of encryption/authentication protocols and SPIs is The management of encryption/authentication protocols and SPIs is
defined in [RFC5202]. The UDP encapsulation format and processing of defined in [RFC5202]. The UDP encapsulation format and processing of
HIP ESP traffic is described in Section 6.1 of [RFC5202]. HIP ESP traffic is described in Section 6.1 of [RFC5202].
6. Security Considerations 6. Security Considerations
6.1. Privacy Considerations 6.1. Privacy Considerations
The locators are in plain text format in favor of inspection at HIP- The locators are in plain text format in favor of inspection at HIP-
aware middleboxes in the future. The current draft does not specify aware middleboxes in the future. The current document does not
encrypted versions of LOCATORs even though it could be beneficial for specify encrypted versions of LOCATORs, even though it could be
privacy reasons to avoid disclosing them to middleboxes. beneficial for privacy reasons to avoid disclosing them to
middleboxes.
It is also possible that end-users may not want to reveal all It is also possible that end-users may not want to reveal all
locators to each other. For example, tracking the physical location locators to each other. For example, tracking the physical location
of a multihoming end-host may become easier if it reveals all of a multihoming end-host may become easier if it reveals all
locators to its peer during a base exchange. Also, revealing host locators to its peer during a base exchange. Also, revealing host
addresses exposes information about the local topology which may not addresses exposes information about the local topology that may not
be allowed in all corporate environments. For these two reasons, an be allowed in all corporate environments. For these two reasons, an
end-host may exclude certain host addresses from its LOCATOR end-host may exclude certain host addresses from its LOCATOR
parameter. However, such behavior creates non-optimal paths when the parameter. However, such behavior creates non-optimal paths when the
hosts are located behind the same NAT. Especially, this could be hosts are located behind the same NAT. Especially, this could be
problematic with a legacy NAT that does not support routing from the problematic with a legacy NAT that does not support routing from the
private address realm back to itself through the outer address of the private address realm back to itself through the outer address of the
NAT. This scenario is referred to as the hairpin problem [RFC5128]. NAT. This scenario is referred to as the hairpin problem [RFC5128].
With such a legacy NAT, the only option left would be to use a With such a legacy NAT, the only option left would be to use a
relayed transport address from a TURN server. relayed transport address from a TURN server.
The use of HIP relay servers and TURN relays can be also useful for The use of HIP relay servers and TURN relays can be also useful for
privacy purposes. For example, a privacy concerned Responder may privacy purposes. For example, a privacy concerned Responder may
reveal only its HIP relay server and Relayed candidates to reveal only its HIP relay server and Relayed candidates to
Initiators. This same mechanism also protects the Responder against Initiators. This same mechanism also protects the Responder against
Denial-of-Service attacks by allowing the Responder to initiate new Denial-of-Service (DoS) attacks by allowing the Responder to initiate
connections even if its relays would be unavailable due to a DoS new connections even if its relays would be unavailable due to a DoS
attack. attack.
6.2. Opportunistic Mode 6.2. Opportunistic Mode
A HIP relay server should have one address per relay client when a A HIP relay server should have one address per relay client when a
HIP relay is serving more than one relay clients and supports HIP relay is serving more than one relay client and supports
opportunistic mode. Otherwise, it cannot be guaranteed that the HIP opportunistic mode. Otherwise, it cannot be guaranteed that the HIP
relay server can deliver the I1 packet to the intended recipient. relay server can deliver the I1 packet to the intended recipient.
6.3. Base Exchange Replay Protection for HIP Relay Server 6.3. Base Exchange Replay Protection for HIP Relay Server
In certain scenarios, it is possible that an attacker, or two In certain scenarios, it is possible that an attacker, or two
attackers, can replay an earlier base exchange through a HIP relay attackers, can replay an earlier base exchange through a HIP relay
server by masquerading as the original Initiator and Responder. The server by masquerading as the original Initiator and Responder. The
attack does not require the attacker(s) to compromise the private attack does not require the attacker(s) to compromise the private
key(s) of the attacked host(s). However, for this attack to succeed, key(s) of the attacked host(s). However, for this attack to succeed,
the Responder has to be disconnected from the HIP relay server. the Responder has to be disconnected from the HIP relay server.
The relay can protect itself against replay attacks by becoming The relay can protect itself against replay attacks by becoming
involved in the base exchange by introducing nonces that the end- involved in the base exchange by introducing nonces that the end-
hosts (Initiator and Responder) are required to sign. One way to do hosts (Initiator and Responder) are required to sign. One way to do
this is to add ECHO_REQUEST_M parameters to the R1 and I2 packets as this is to add ECHO_REQUEST_M parameters to the R1 and I2 packets as
described in [I-D.heer-hip-middle-auth] and drop the I2 or R2 packets described in [HIP-MIDDLE] and drop the I2 or R2 packets if the
if the corresponding ECHO_RESPONSE_M parameters are not present. corresponding ECHO_RESPONSE_M parameters are not present.
6.4. Demuxing Different HIP Associations 6.4. Demuxing Different HIP Associations
Section 5.1 of [RFC3948] describes a security issue for the UDP Section 5.1 of [RFC3948] describes a security issue for the UDP
encapsulation in the standard IP tunnel mode when two hosts behind encapsulation in the standard IP tunnel mode when two hosts behind
different NATs have the same private IP address and initiate different NATs have the same private IP address and initiate
communication to the same Responder in the public Internet. The communication to the same Responder in the public Internet. The
Responder cannot distinguish between two hosts, because security Responder cannot distinguish between two hosts, because security
associations are based on the same inner IP addresses. associations are based on the same inner IP addresses.
This issue does not exist with the UDP encapsulation of HIP ESP This issue does not exist with the UDP encapsulation of HIP ESP
transport format because the Responder uses HITs to distinguish transport format because the Responder uses HITs to distinguish
between different Initiators. between different Initiators.
7. IANA Considerations 7. IANA Considerations
This section is to be interpreted according to [RFC5226]. This section is to be interpreted according to [RFC5226].
[TO BE REMOVED: Upon publication of this document, IANA is requested
to register a UDP port from the Registered Ports range and the RFC
editor is requested to change all occurrences of port HIPPORT to the
port IANA has registered. The HIPPORT number 50500 should be used
for initial experimentation. ]
This document updates the IANA Registry for HIP Parameter Types This document updates the IANA Registry for HIP Parameter Types
[RFC5201] by assigning new HIP Parameter Type values for the new HIP [RFC5201] by assigning new HIP Parameter Type values for the new HIP
Parameters: RELAY_FROM, RELAY_TO and REG_FROM (defined in Parameters: RELAY_FROM, RELAY_TO, and REG_FROM (defined in
Section 5.6), RELAY_HMAC (defined in Section 5.8), TRANSACTION_PACING Section 5.6), RELAY_HMAC (defined in Section 5.8), TRANSACTION_PACING
(defined in Section 5.5), and NAT_TRAVERSAL_MODE (defined in (defined in Section 5.5), and NAT_TRAVERSAL_MODE (defined in
Section 5.4). Section 5.4).
This document defines an additional registration type for the HIP This document defines an additional registration type for the HIP
Registration Extension [RFC5203] that allows registering with a HIP Registration Extension [RFC5203] that allows registering with a HIP
relay server for relaying service: RELAY_UDP_HIP (defined in relay server for relaying service: RELAY_UDP_HIP (defined in
Section 5.9). Section 5.9).
This document also defines NO_VALID_NAT_TRAVERSAL_MODE_PARAMETER, This document also defines NO_VALID_NAT_TRAVERSAL_MODE_PARAMETER,
CONNECTIVITY_CHECKS_FAILED and MESSAGE_NOT_RELAYED Notify Packet CONNECTIVITY_CHECKS_FAILED, and MESSAGE_NOT_RELAYED Notify Packet
Types [RFC5201] in Section 5.10. Types [RFC5201] in Section 5.10.
The NAT_TRAVERSAL_MODE parameter has 16-bit unsigned integer fields The NAT_TRAVERSAL_MODE parameter has 16-bit unsigned integer fields
for different modes, for which IANA is to create and maintain a new for different modes, for which IANA has created and maintains a new
sub-registry entitled "HIP NAT traversal modes" under the "Host sub-registry entitled "HIP NAT Traversal Modes" under the "Host
Identity Protocol (HIP) Parameters". Initial values for the NAT Identity Protocol (HIP) Parameters". Initial values for the NAT
traversal mode registry are given in Section 5.4; future assignments traversal mode registry are given in Section 5.4; future assignments
are to be made through IETF Review [RFC5226]. Assignments consist of are to be made through IETF Review [RFC5226]. Assignments consist of
a NAT traversal mode identifier name and its associated value. [TO a NAT traversal mode identifier name and its associated value.
BE REMOVED: This registration should take place at the following
location: http://www.iana.org/assignments/hip-parameters/]
8. Contributors 8. Contributors
This draft is a product of a design team which also included Marcelo This RFC is a product of a design team that also included Marcelo
Bagnulo and Philip Matthews who both have made major contributions to Bagnulo and Philip Matthews, who both have made major contributions
this document. to this document.
9. Acknowledgments 9. Acknowledgments
Thanks for Jonathan Rosenberg and the rest of the MMUSIC WG folks for Thanks to Jonathan Rosenberg and the rest of the MMUSIC WG folks for
the excellent work on ICE. In addition, the authors would like to the excellent work on ICE. In addition, the authors would like to
thank Andrei Gurtov, Simon Schuetz, Martin Stiemerling, Lars Eggert, thank Andrei Gurtov, Simon Schuetz, Martin Stiemerling, Lars Eggert,
Vivien Schmitt, Abhinav Pathak for their contributions and Tobias Vivien Schmitt, and Abhinav Pathak for their contributions and Tobias
Heer, Teemu Koponen, Juhana Mattila, Jeffrey M. Ahrenholz, Kristian Heer, Teemu Koponen, Juhana Mattila, Jeffrey M. Ahrenholz, Kristian
Slavov, Janne Lindqvist, Pekka Nikander, Lauri Silvennoinen, Jukka Slavov, Janne Lindqvist, Pekka Nikander, Lauri Silvennoinen, Jukka
Ylitalo, Juha Heinanen, Joakim Koskela, Samu Varjonen, Dan Wing and Ylitalo, Juha Heinanen, Joakim Koskela, Samu Varjonen, Dan Wing, and
Jani Hautakorpi for their comments on this document. Jani Hautakorpi for their comments on this document.
Miika Komu is working in the Networking Research group at Helsinki Miika Komu has been working in the Networking Research group at
Institute for Information Technology (HIIT). The InfraHIP project Helsinki Institute for Information Technology (HIIT). The work has
was funded by Tekes, Telia-Sonera, Elisa, Nokia, the Finnish Defence been funded by Tekes, Telia-Sonera, Elisa, Nokia, the Finnish Defence
Forces, Ericsson, and Birdstep. Forces, Ericsson and Birdstep in InfraHIP I and II projects.
10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.ietf-behave-turn] [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Rosenberg, J., Mahy, R., and P. Matthews, "Traversal Using Requirement Levels", BCP 14, RFC 2119, March 1997.
Relays around NAT (TURN): Relay Extensions to Session
Traversal Utilities for NAT (STUN)",
draft-ietf-behave-turn-16 (work in progress), July 2009.
[I-D.ietf-mmusic-ice] [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Rosenberg, J., "Interactive Connectivity Establishment Architecture", RFC 4291, February 2006.
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols",
draft-ietf-mmusic-ice-19 (work in progress), October 2007.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol
Requirement Levels", BCP 14, RFC 2119, March 1997. (HIP) Architecture", RFC 4423, May 2006.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC5201] Moskowitz, R., Nikander, P., Jokela, P., and T.
Architecture", RFC 4291, February 2006. Henderson, "Host Identity Protocol", RFC 5201,
April 2008.
[RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol [RFC5202] Jokela, P., Moskowitz, R., and P. Nikander, "Using the
(HIP) Architecture", RFC 4423, May 2006. Encapsulating Security Payload (ESP) Transport Format
with the Host Identity Protocol (HIP)", RFC 5202,
April 2008.
[RFC5201] Moskowitz, R., Nikander, P., Jokela, P., and T. Henderson, [RFC5203] Laganier, J., Koponen, T., and L. Eggert, "Host
"Host Identity Protocol", RFC 5201, April 2008. Identity Protocol (HIP) Registration Extension",
RFC 5203, April 2008.
[RFC5202] Jokela, P., Moskowitz, R., and P. Nikander, "Using the [RFC5204] Laganier, J. and L. Eggert, "Host Identity Protocol
Encapsulating Security Payload (ESP) Transport Format with (HIP) Rendezvous Extension", RFC 5204, April 2008.
the Host Identity Protocol (HIP)", RFC 5202, April 2008.
[RFC5203] Laganier, J., Koponen, T., and L. Eggert, "Host Identity [RFC5206] Nikander, P., Henderson, T., Vogt, C., and J. Arkko,
Protocol (HIP) Registration Extension", RFC 5203, "End-Host Mobility and Multihoming with the Host
April 2008. Identity Protocol", RFC 5206, April 2008.
[RFC5204] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing
Rendezvous Extension", RFC 5204, April 2008. an IANA Considerations Section in RFCs", BCP 26,
RFC 5226, May 2008.
[RFC5206] Nikander, P., Henderson, T., Vogt, C., and J. Arkko, "End- [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
Host Mobility and Multihoming with the Host Identity (ICE): A Protocol for Network Address Translator (NAT)
Protocol", RFC 5206, April 2008. Traversal for Offer/Answer Protocols", RFC 5245,
April 2010.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
IANA Considerations Section in RFCs", BCP 26, RFC 5226, "Session Traversal Utilities for NAT (STUN)", RFC 5389,
May 2008. October 2008.
[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, [RFC5766] Rosenberg, J., Mahy, R., and P. Matthews, "Traversal
"Session Traversal Utilities for NAT (STUN)", RFC 5389, Using Relays around NAT (TURN): Relay Extensions to
October 2008. Session Traversal Utilities for NAT (STUN)", RFC 5766,
April 2010.
10.2. Informative References 10.2. Informative References
[I-D.heer-hip-middle-auth] [HIP-MIDDLE] Heer, T., Wehrle, K., and M. Komu, "End-Host
Heer, T., Wehrle, K., and M. Komu, "End-Host Authentication for HIP Middleboxes", Work in Progress,
Authentication for HIP Middleboxes", February 2009.
draft-heer-hip-middle-auth-02 (work in progress),
February 2009.
[I-D.rosenberg-mmusic-ice-nonsip] [MMUSIC-ICE] Rosenberg, J., "Guidelines for Usage of Interactive
Rosenberg, J., "Guidelines for Usage of Interactive Connectivity Establishment (ICE) by non Session
Connectivity Establishment (ICE) by non Session Initiation Protocol (SIP) Protocols", Work in Progress,
Initiation Protocol (SIP) Protocols", July 2008.
draft-rosenberg-mmusic-ice-nonsip-01 (work in progress),
July 2008.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M. [RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and
Stenberg, "UDP Encapsulation of IPsec ESP Packets", M. Stenberg, "UDP Encapsulation of IPsec ESP Packets",
RFC 3948, January 2005. RFC 3948, January 2005.
[RFC4787] Audet, F. and C. Jennings, "Network Address Translation [RFC4787] Audet, F. and C. Jennings, "Network Address Translation
(NAT) Behavioral Requirements for Unicast UDP", BCP 127, (NAT) Behavioral Requirements for Unicast UDP",
RFC 4787, January 2007. BCP 127, RFC 4787, January 2007.
[RFC5128] Srisuresh, P., Ford, B., and D. Kegel, "State of Peer-to- [RFC5128] Srisuresh, P., Ford, B., and D. Kegel, "State of Peer-
Peer (P2P) Communication across Network Address to-Peer (P2P) Communication across Network Address
Translators (NATs)", RFC 5128, March 2008. Translators (NATs)", RFC 5128, March 2008.
[RFC5207] Stiemerling, M., Quittek, J., and L. Eggert, "NAT and [RFC5207] Stiemerling, M., Quittek, J., and L. Eggert, "NAT and
Firewall Traversal Issues of Host Identity Protocol (HIP) Firewall Traversal Issues of Host Identity Protocol
Communication", RFC 5207, April 2008. (HIP) Communication", RFC 5207, April 2008.
Appendix A. Selecting a Value for Check Pacing Appendix A. Selecting a Value for Check Pacing
Selecting a suitable value for the connectivity check transaction Selecting a suitable value for the connectivity check transaction
pacing is essential for the performance of connectivity check-based pacing is essential for the performance of connectivity check-based
NAT traversal. The value should not be so small that the checks NAT traversal. The value should not be so small that the checks
cause network congestion or overwhelm the NATs. On the other hand, a cause network congestion or overwhelm the NATs. On the other hand, a
pacing value that is too high makes the checks last for a long time, pacing value that is too high makes the checks last for a long time,
thus increasing the connection setup delay. thus increasing the connection setup delay.
The Ta value may be configured by the user in environments where the The Ta value may be configured by the user in environments where the
network characteristics are known beforehand. However, if the network characteristics are known beforehand. However, if the
characteristics are not known, it is recommended that the value is characteristics are not known, it is recommended that the value is
adjusted dynamically. In this case it's recommended that the hosts adjusted dynamically. In this case, it's recommended that the hosts
estimate the RTT between them and set the minimum Ta value so that estimate the round-trip time (RTT) between them and set the minimum
only two connectivity check messages are sent on every RTT. Ta value so that only two connectivity check messages are sent on
every RTT.
One way to estimate the RTT is to use the time it takes for the HIP One way to estimate the RTT is to use the time it takes for the HIP
relay server registration exchange to complete; this would give an relay server registration exchange to complete; this would give an
estimate on the registering host's access link's RTT. Also the I1/R1 estimate on the registering host's access link's RTT. Also, the
exchange could be used for estimating the RTT, but since the R1 can I1/R1 exchange could be used for estimating the RTT, but since the R1
be cached in the network, or the relaying service can increase the can be cached in the network, or the relaying service can increase
delay notably, it is not recommended. the delay notably, it is not recommended.
Appendix B. Base Exchange through a Rendezvous Server Appendix B. Base Exchange through a Rendezvous Server
When the Initiator looks up the information of the Responder from When the Initiator looks up the information of the Responder from
DNS, it's possible that it discovers an RVS record [RFC5204]. In DNS, it's possible that it discovers a rendezvous server (RVS) record
this case, if the Initiator uses NAT traversal methods described in [RFC5204]. In this case, if the Initiator uses NAT traversal methods
this document, it MAY use its own HIP relay server to forward HIP described in this document, it MAY use its own HIP relay server to
traffic to the Rendezvous server. The Initiator will send the I1 forward HIP traffic to the rendezvous server. The Initiator will
packet using its HIP relay server which will then forward it to the send the I1 packet using its HIP relay server, which will then
RVS server of the Responder. In this case, the value of the protocol forward it to the RVS server of the Responder. In this case, the
field in the RELAY_TO parameter MUST be IP since RVS does not support value of the protocol field in the RELAY_TO parameter MUST be IP
UDP-encapsulated base exchange packets. The Responder will send the since RVS does not support UDP-encapsulated base exchange packets.
R1 packet directly to the Initiator's HIP relay server and the The Responder will send the R1 packet directly to the Initiator's HIP
following I2 and R2 packets are also sent directly using the relay. relay server and the following I2 and R2 packets are also sent
directly using the relay.
In case the Initiator is not able to distinguish which records are In case the Initiator is not able to distinguish which records are
RVS address records and which are Responder's address records (e.g., RVS address records and which are Responder's address records (e.g.,
if the DNS server did not support HIP extensions), the Initiator if the DNS server did not support HIP extensions), the Initiator
SHOULD first try to contact the Responder directly, without using a SHOULD first try to contact the Responder directly, without using a
HIP relay server. If none of the addresses is reachable, it MAY try HIP relay server. If none of the addresses are reachable, it MAY try
out them using its own HIP relay server as described above. them out using its own HIP relay server as described above.
Appendix C. Document Revision History
To be removed upon publication
+----------+--------------------------------------------------------+
| Revision | Comments |
+----------+--------------------------------------------------------+
| -00 | Initial version. |
| -01 | Draft based on RVS. |
| -02 | Draft based on Relay proxies and ICE concepts. |
| -03 | Draft based on STUN/ICE formats. |
| -04 | Issues 25-27,29-36 |
| -05 | Issues 28,40-43,47,49,51 |
| -06 | New copyright boilerplate and STUN username encoding |
| -07 | New NOTIFY error packet parameters, changed handling |
| | of I2/R2 via relay with UDP-ENCAPSULATION mode |
| -08 | Small editorial fixes regarding WGLC comments |
| -09 | Small fixes regarding IESG and Gen-ART review comments |
+----------+--------------------------------------------------------+
Authors' Addresses Authors' Addresses
Miika Komu Miika Komu
Helsinki Institute for Information Technology Helsinki Institute for Information Technology
Metsanneidonkuja 4 Metsanneidonkuja 4
Espoo Espoo
Finland Finland
Phone: +358503841531 Phone: +358503841531
Fax: +35896949768 Fax: +35896949768
Email: miika@iki.fi EMail: miika@iki.fi
URI: http://www.hiit.fi/ URI: http://www.hiit.fi/
Thomas Henderson Thomas Henderson
The Boeing Company The Boeing Company
P.O. Box 3707 P.O. Box 3707
Seattle, WA Seattle, WA
USA USA
EMail: thomas.r.henderson@boeing.com
Email: thomas.r.henderson@boeing.com
Hannes Tschofenig Hannes Tschofenig
Nokia Siemens Networks Nokia Siemens Networks
Linnoitustie 6 Linnoitustie 6
Espoo 02600 Espoo 02600
Finland Finland
Phone: +358 (50) 4871445 Phone: +358 (50) 4871445
Email: Hannes.Tschofenig@gmx.net EMail: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.com URI: http://www.tschofenig.priv.at/
Jan Melen Jan Melen
Ericsson Research Nomadiclab Ericsson Research Nomadiclab
Hirsalantie 11 Hirsalantie 11
02420 Jorvas 02420 Jorvas
Finland Finland
Phone: +358 9 2991 Phone: +358 9 2991
Email: jan.melen@ericsson.com EMail: jan.melen@ericsson.com
Ari Keranen (editor) Ari Keranen (editor)
Ericsson Research Nomadiclab Ericsson Research Nomadiclab
Hirsalantie 11 Hirsalantie 11
02420 Jorvas 02420 Jorvas
Finland Finland
Phone: +358 9 2991 Phone: +358 9 2991
Email: ari.keranen@ericsson.com EMail: ari.keranen@ericsson.com
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