draft-ietf-sip-outbound-14.txt   draft-ietf-sip-outbound-15.txt 
Network Working Group C. Jennings, Ed. Network Working Group C. Jennings, Ed.
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Updates: 3261,3327 R. Mahy, Ed. Updates: 3261,3327 R. Mahy, Ed.
(if approved) Plantronics (if approved) Plantronics
Intended status: Standards Track May 25, 2008 Intended status: Standards Track June 12, 2008
Expires: November 26, 2008 Expires: December 14, 2008
Managing Client Initiated Connections in the Session Initiation Protocol Managing Client Initiated Connections in the Session Initiation Protocol
(SIP) (SIP)
draft-ietf-sip-outbound-14 draft-ietf-sip-outbound-15
Status of this Memo Status of this Memo
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have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
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This Internet-Draft will expire on November 26, 2008. This Internet-Draft will expire on December 14, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract Abstract
The Session Initiation Protocol (SIP) allows proxy servers to The Session Initiation Protocol (SIP) allows proxy servers to
initiate TCP connections and send asynchronous UDP datagrams to User initiate TCP connections or to send asynchronous UDP datagrams to
Agents in order to deliver requests. However, many practical User Agents in order to deliver requests. However, in a large number
considerations, such as the existence of firewalls and Network of real deployments, many practical considerations, such as the
Address Translators (NATs), prevent servers from connecting to User existence of firewalls and Network Address Translators (NATs) or the
Agents in this way. This specification defines behaviors for User use of TLS with server-provided certificates, prevent servers from
Agents, registrars and proxy servers that allow requests to be connecting to User Agents in this way. This specification defines
delivered on existing connections established by the User Agent. It behaviors for User Agents, registrars and proxy servers that allow
also defines keep alive behaviors needed to keep NAT bindings open requests to be delivered on existing connections established by the
and specifies the usage of multiple connections from the User Agent User Agent. It also defines keep alive behaviors needed to keep NAT
to its Registrar. bindings open and specifies the usage of multiple connections from
the User Agent to its Registrar.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4 2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4
2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 5
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Summary of Mechanism . . . . . . . . . . . . . . . . . . 6 3.1. Summary of Mechanism . . . . . . . . . . . . . . . . . . . 6
3.2. Single Registrar and UA . . . . . . . . . . . . . . . . . 6 3.2. Single Registrar and UA . . . . . . . . . . . . . . . . . 6
3.3. Multiple Connections from a User Agent . . . . . . . . . 8 3.3. Multiple Connections from a User Agent . . . . . . . . . . 8
3.4. Edge Proxies . . . . . . . . . . . . . . . . . . . . . . 10 3.4. Edge Proxies . . . . . . . . . . . . . . . . . . . . . . . 10
3.5. Keep alive Technique . . . . . . . . . . . . . . . . . . 11 3.5. Keep alive Technique . . . . . . . . . . . . . . . . . . . 11
3.5.1. CRLF Keep alive Technique . . . . . . . . . . . . . . 12 3.5.1. CRLF Keep alive Technique . . . . . . . . . . . . . . 12
3.5.2. STUN Keep alive Technique . . . . . . . . . . . . . . 12 3.5.2. STUN Keep alive Technique . . . . . . . . . . . . . . 12
4. User Agent Mechanisms . . . . . . . . . . . . . . . . . . . . 12 4. User Agent Procedures . . . . . . . . . . . . . . . . . . . . 12
4.1. Instance ID Creation . . . . . . . . . . . . . . . . . . 12 4.1. Instance ID Creation . . . . . . . . . . . . . . . . . . . 12
4.2. Registrations . . . . . . . . . . . . . . . . . . . . . . 14 4.2. Registrations . . . . . . . . . . . . . . . . . . . . . . 14
4.2.1. Initial Registrations . . . . . . . . . . . . . . . . 14 4.2.1. Initial Registrations . . . . . . . . . . . . . . . . 14
4.2.2. Subsequent REGISTER requests . . . . . . . . . . . . . 16 4.2.2. Subsequent REGISTER requests . . . . . . . . . . . . . 16
4.2.3. Non Outbound Registrations . . . . . . . . . . . . . . 16 4.2.3. Non Outbound Registrations . . . . . . . . . . . . . . 16
4.3. Sending Non-REGISTER Requests . . . . . . . . . . . . . . 16 4.3. Sending Non-REGISTER Requests . . . . . . . . . . . . . . 16
4.4. Keep-alives and Detecting Flow Failure . . . . . . . . . 17 4.4. Keep-alives and Detecting Flow Failure . . . . . . . . . . 17
4.4.1. Keep alive with CRLF . . . . . . . . . . . . . . . . . 18 4.4.1. Keep alive with CRLF . . . . . . . . . . . . . . . . . 18
4.4.2. Keep alive with STUN . . . . . . . . . . . . . . . . . 19 4.4.2. Keep alive with STUN . . . . . . . . . . . . . . . . . 19
4.5. Flow Recovery . . . . . . . . . . . . . . . . . . . . . . 20 4.5. Flow Recovery . . . . . . . . . . . . . . . . . . . . . . 20
5. Edge Proxy Mechanisms . . . . . . . . . . . . . . . . . . . . 21 5. Edge Proxy Procedures . . . . . . . . . . . . . . . . . . . . 21
5.1. Processing Register Requests . . . . . . . . . . . . . . 21 5.1. Processing Register Requests . . . . . . . . . . . . . . . 21
5.2. Generating Flow Tokens . . . . . . . . . . . . . . . . . 21 5.2. Generating Flow Tokens . . . . . . . . . . . . . . . . . . 21
5.3. Forwarding Non-REGISTER Requests . . . . . . . . . . . . 22 5.3. Forwarding Non-REGISTER Requests . . . . . . . . . . . . . 22
5.3.1. Processing Incoming Requests . . . . . . . . . . . . . 22 5.3.1. Processing Incoming Requests . . . . . . . . . . . . . 22
5.3.2. Processing Outgoing Requests . . . . . . . . . . . . . 23 5.3.2. Processing Outgoing Requests . . . . . . . . . . . . . 23
5.4. Edge Proxy Keep alive Handling . . . . . . . . . . . . . 23 5.4. Edge Proxy Keep alive Handling . . . . . . . . . . . . . . 23
6. Registrar Mechanisms . . . . . . . . . . . . . . . . . . . . . 23 6. Registrar Procedures . . . . . . . . . . . . . . . . . . . . . 24
7. Authoritative Proxy Mechanisms: Forwarding Requests . . . . . 25 7. Authoritative Proxy Procedures: Forwarding Requests . . . . . 26
8. STUN Keep alive Processing . . . . . . . . . . . . . . . . . . 26 8. STUN Keep alive Processing . . . . . . . . . . . . . . . . . . 26
8.1. Use with Sigcomp . . . . . . . . . . . . . . . . . . . . 28 8.1. Use with Sigcomp . . . . . . . . . . . . . . . . . . . . . 28
9. Example Message Flow . . . . . . . . . . . . . . . . . . . . . 28 9. Example Message Flow . . . . . . . . . . . . . . . . . . . . . 28
9.1. Subscription to configuration package . . . . . . . . . . 28 9.1. Subscription to configuration package . . . . . . . . . . 28
9.2. Registration . . . . . . . . . . . . . . . . . . . . . . 30 9.2. Registration . . . . . . . . . . . . . . . . . . . . . . . 30
9.3. Incoming call and proxy crash . . . . . . . . . . . . . . 33 9.3. Incoming call and proxy crash . . . . . . . . . . . . . . 33
9.4. Re-registration . . . . . . . . . . . . . . . . . . . . . 36 9.4. Re-registration . . . . . . . . . . . . . . . . . . . . . 36
9.5. Outgoing call . . . . . . . . . . . . . . . . . . . . . . 36 9.5. Outgoing call . . . . . . . . . . . . . . . . . . . . . . 36
10. Grammar . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10. Grammar . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38
11.1. Flow-Timer Header Field . . . . . . . . . . . . . . . . . 38 11.1. Flow-Timer Header Field . . . . . . . . . . . . . . . . . 38
11.2. 'reg-id' Contact Header Field Parameter . . . . . . . . . 39 11.2. 'reg-id' Contact Header Field Parameter . . . . . . . . . 38
11.3. SIP/SIPS URI Parameters . . . . . . . . . . . . . . . . . 39 11.3. SIP/SIPS URI Parameters . . . . . . . . . . . . . . . . . 39
11.4. SIP Option Tag . . . . . . . . . . . . . . . . . . . . . 39 11.4. SIP Option Tag . . . . . . . . . . . . . . . . . . . . . . 39
11.5. 430 (Flow Failed) Response Code . . . . . . . . . . . . . 39 11.5. 430 (Flow Failed) Response Code . . . . . . . . . . . . . 39
11.6. 439 (First Hop Lacks Outbound Support) Response Code . . 40 11.6. 439 (First Hop Lacks Outbound Support) Response Code . . . 40
11.7. Media Feature Tag . . . . . . . . . . . . . . . . . . . . 40 11.7. Media Feature Tag . . . . . . . . . . . . . . . . . . . . 40
12. Security Considerations . . . . . . . . . . . . . . . . . . . 41 12. Security Considerations . . . . . . . . . . . . . . . . . . . 41
13. Operational Notes on Transports . . . . . . . . . . . . . . . 42 13. Operational Notes on Transports . . . . . . . . . . . . . . . 42
14. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 43 14. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 43
15. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 15. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 43
15.1. Changes from 12 Version . . . . . . . . . . . . . . . . . 43 16. References . . . . . . . . . . . . . . . . . . . . . . . . . . 43
15.2. Changes from 11 Version . . . . . . . . . . . . . . . . . 43 16.1. Normative References . . . . . . . . . . . . . . . . . . . 43
15.3. Changes from 09 Version . . . . . . . . . . . . . . . . . 43 16.2. Informational References . . . . . . . . . . . . . . . . . 45
15.4. Changes from 08 Version . . . . . . . . . . . . . . . . . 43 Appendix A. Default Flow Registration Backoff Times . . . . . . . 46
15.5. Changes from 07 Version . . . . . . . . . . . . . . . . . 44 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 46
15.6. Changes from 06 Version . . . . . . . . . . . . . . . . . 44 Intellectual Property and Copyright Statements . . . . . . . . . . 48
15.7. Changes from 05 Version . . . . . . . . . . . . . . . . . 44
15.8. Changes from 04 Version . . . . . . . . . . . . . . . . . 45
15.9. Changes from 03 Version . . . . . . . . . . . . . . . . . 46
15.10. Changes from 02 Version . . . . . . . . . . . . . . . . . 47
15.11. Changes from 01 Version . . . . . . . . . . . . . . . . . 47
15.12. Changes from 00 Version . . . . . . . . . . . . . . . . . 47
16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 47
17. References . . . . . . . . . . . . . . . . . . . . . . . . . . 48
17.1. Normative References . . . . . . . . . . . . . . . . . . 48
17.2. Informational References . . . . . . . . . . . . . . . . 49
Appendix A. Default Flow Registration Backoff Times . . . . . . . 50
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 51
Intellectual Property and Copyright Statements . . . . . . . . . . 52
1. Introduction 1. Introduction
There are many environments for SIP [RFC3261] deployments in which There are many environments for SIP [RFC3261] deployments in which
the User Agent (UA) can form a connection to a Registrar or Proxy but the User Agent (UA) can form a connection to a Registrar or Proxy but
in which connections in the reverse direction to the UA are not in which connections in the reverse direction to the UA are not
possible. This can happen for several reasons, but the most likely possible. This can happen for several reasons, but the most likely
is a NAT or a firewall in between the SIP UA and the proxy. Many is a NAT or a firewall in between the SIP UA and the proxy. Many
such devices will only allow outgoing connections. This such devices will only allow outgoing connections. This
specification allows a SIP User Agent behind such a firewall or NAT specification allows a SIP User Agent behind such a firewall or NAT
to receive inbound traffic associated with registrations or dialogs to receive inbound traffic associated with registrations or dialogs
that it initiates. that it initiates.
Most IP phones and personal computers get their network Most IP phones and personal computers get their network
configurations dynamically via a protocol such as DHCP (Dynamic Host configurations dynamically via a protocol such as DHCP (Dynamic Host
Configuration Protocol). These systems typically do not have a Configuration Protocol). These systems typically do not have a
useful name in the Domain Name System (DNS), and they almost never useful name in the Domain Name System (DNS), and they almost never
have a long-term, stable DNS name that is appropriate for use in the have a long-term, stable DNS name that is appropriate for use in the
subjectAltName of a certificate, as required by [RFC3261]. However, subjectAltName of a certificate, as required by [RFC3261]. However,
these systems can still act as a Transport Layer Security (TLS) these systems can still act as a Transport Layer Security (TLS)
[RFC4346] client and form connections to a proxy or registrar which [RFC4346] client and form outbound connections to a proxy or
authenticates with a server certificate. The server can authenticate registrar which authenticates with a server certificate. The server
the UA using a shared secret in a digest challenge (as defined in can authenticate the UA using a shared secret in a digest challenge
Section 22 of RFC 3261) over that TLS connection. (as defined in Section 22 of RFC 3261) over that TLS connection.
This specification allows a SIP User Agent who has to initiate the
TLS connection to receive inbound traffic associated with
registrations or dialogs that it initiates.
The key idea of this specification is that when a UA sends a REGISTER The key idea of this specification is that when a UA sends a REGISTER
or a dialog-forming request, the proxy can later use this same request or a dialog-forming request, the proxy can later use this
network "flow"--whether this is a bidirectional stream of UDP same network "flow"--whether this is a bidirectional stream of UDP
datagrams, a TCP connection, or an analogous concept in another datagrams, a TCP connection, or an analogous concept in another
transport protocol--to forward any incoming requests that need to go transport protocol--to forward any incoming requests that need to go
to this UA in the context of the registration or dialog. to this UA in the context of the registration or dialog.
For a UA to receive incoming requests, the UA has to connect to a For a UA to receive incoming requests, the UA has to connect to a
server. Since the server can't connect to the UA, the UA has to make server. Since the server can't connect to the UA, the UA has to make
sure that a flow is always active. This requires the UA to detect sure that a flow is always active. This requires the UA to detect
when a flow fails. Since such detection takes time and leaves a when a flow fails. Since such detection takes time and leaves a
window of opportunity for missed incoming requests, this mechanism window of opportunity for missed incoming requests, this mechanism
allows the UA to register over multiple flows at the same time. This allows the UA to register over multiple flows at the same time. This
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Flow Token: An identifier which uniquely identifies a flow which can Flow Token: An identifier which uniquely identifies a flow which can
be included in a SIP URI (Uniform Resource Identifier). be included in a SIP URI (Uniform Resource Identifier).
reg-id: This refers to the value of a new header field parameter reg-id: This refers to the value of a new header field parameter
value for the Contact header field. When a UA registers multiple value for the Contact header field. When a UA registers multiple
times, each for a different flow, each concurrent registration times, each for a different flow, each concurrent registration
gets a unique reg-id value. gets a unique reg-id value.
instance-id: This specification uses the word instance-id to refer instance-id: This specification uses the word instance-id to refer
to the value of the "sip.instance" media feature tag in the to the value of the "sip.instance" media feature tag in the
Contact header field. This is a Uniform Resource Name (URN) that Contact header field. This is a Uniform Resource Name (URN) that
uniquely identifies this specific UA instance. uniquely identifies this specific UA instance.
'ob' Parameter: The 'ob' parameter is a SIP URI parameter which has ob Parameter: The 'ob' parameter is a SIP URI parameter which has
different meaning depending on context. In a Path header field different meaning depending on context. In a Path header field
value it is used by the first edge proxy to indicate that a flow value it is used by the first edge proxy to indicate that a flow
token was added to the URI. In a Contact or Route header field token was added to the URI. In a Contact or Route header field
value it indicates that the UA would like other requests in the value it indicates that the UA would like other requests in the
same dialog routed over the same flow. same dialog routed over the same flow.
outbound-proxy-set: A set of SIP URIs (Uniform Resource Identifiers) outbound-proxy-set: A set of SIP URIs (Uniform Resource Identifiers)
that represents each of the outbound proxies (often Edge Proxies) that represents each of the outbound proxies (often Edge Proxies)
with which the UA will attempt to maintain a direct flow. The with which the UA will attempt to maintain a direct flow. The
first URI in the set is often referred to as the primary outbound first URI in the set is often referred to as the primary outbound
proxy and the second as the secondary outbound proxy. There is no proxy and the second as the secondary outbound proxy. There is no
skipping to change at page 6, line 12 skipping to change at page 6, line 16
The mechanisms defined in this document are useful in several The mechanisms defined in this document are useful in several
scenarios discussed below, including the simple co-located registrar scenarios discussed below, including the simple co-located registrar
and proxy, a User Agent desiring multiple connections to a resource and proxy, a User Agent desiring multiple connections to a resource
(for redundancy, for example), and a system that uses Edge Proxies. (for redundancy, for example), and a system that uses Edge Proxies.
This entire section is non-normative. This entire section is non-normative.
3.1. Summary of Mechanism 3.1. Summary of Mechanism
The overall approach is fairly simple. Each UA has a unique Each UA has a unique instance-id that stays the same for this UA even
instance-id that stays the same for this UA even if the UA reboots or if the UA reboots or is power cycled. Each UA can register multiple
is power cycled. Each UA can register multiple times over different times over different flows for the same SIP Address of Record (AOR)
flows for the same SIP Address of Record (AOR) to achieve high to achieve high reliability. Each registration includes the
reliability. Each registration includes the instance-id for the UA instance-id for the UA and a reg-id label that is different for each
and a reg-id label that is different for each flow. The registrar flow. The registrar can use the instance-id to recognize that two
can use the instance-id to recognize that two different registrations different registrations both correspond to the same UA. The
both correspond to the same UA. The registrar can use the reg-id registrar can use the reg-id label to recognize whether a UA is
label to recognize whether a UA is creating a new flow or refreshing creating a new flow or refreshing or replacing an old one, possibly
or replacing an old one, possibly after a reboot or a network after a reboot or a network failure.
failure.
When a proxy goes to route a message to a UA for which it has a When a proxy goes to route a message to a UA for which it has a
binding, it can use any one of the flows on which a successful binding, it can use any one of the flows on which a successful
registration has been completed. A failure to deliver a request on a registration has been completed. A failure to deliver a request on a
particular flow can be tried again on an alternate flow. Proxies can particular flow can be tried again on an alternate flow. Proxies can
determine which flows go to the same UA by comparing the instance-id. determine which flows go to the same UA by comparing the instance-id.
Proxies can tell that a flow replaces a previously abandoned flow by Proxies can tell that a flow replaces a previously abandoned flow by
looking at the reg-id. looking at the reg-id.
When sending a dialog-forming request, a UA can also ask its first When sending a dialog-forming request, a UA can also ask its first
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+-----+-----+ +-----+-----+
| |
| |
+----+--+ +----+--+
| User | | User |
| Agent | | Agent |
+-------+ +-------+
User Agents which form only a single flow continue to register User Agents which form only a single flow continue to register
normally but include the instance-id as described in Section 4.1. normally but include the instance-id as described in Section 4.1.
The UA also includes a reg-id parameter which is used to allow the The UA also includes a reg-id Contact header field which is used to
registrar to detect and avoid keeping invalid contacts when a UA allow the registrar to detect and avoid keeping invalid contacts when
reboots or reconnects after its old connection has failed for some a UA reboots or reconnects after its old connection has failed for
reason. some reason.
For clarity, here is an example. Bob's UA creates a new TCP flow to For clarity, here is an example. Bob's UA creates a new TCP flow to
the registrar and sends the following REGISTER request. the registrar and sends the following REGISTER request.
REGISTER sip:example.com SIP/2.0 REGISTER sip:example.com SIP/2.0
Via: SIP/2.0/TCP 192.168.0.2;branch=z9hG4bK-bad0ce-11-1036 Via: SIP/2.0/TCP 192.0.2.2;branch=z9hG4bK-bad0ce-11-1036
Max-Forwards: 70 Max-Forwards: 70
From: Bob <sip:bob@example.com>;tag=d879h76 From: Bob <sip:bob@example.com>;tag=d879h76
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Call-ID: 8921348ju72je840.204 Call-ID: 8921348ju72je840.204
CSeq: 1 REGISTER CSeq: 1 REGISTER
Supported: path, outbound Supported: path, outbound
Contact: <sip:line1@192.168.0.2;transport=tcp>; reg-id=1; Contact: <sip:line1@192.0.2.2;transport=tcp>; reg-id=1;
;+sip.instance="<urn:uuid:00000000-0000-1000-8000-000A95A0E128>" ;+sip.instance="<urn:uuid:00000000-0000-1000-8000-000A95A0E128>"
Content-Length: 0 Content-Length: 0
The registrar challenges this registration to authenticate Bob. When The registrar challenges this registration to authenticate Bob. When
the registrar adds an entry for this contact under the AOR for Bob, the registrar adds an entry for this contact under the AOR for Bob,
the registrar also keeps track of the connection over which it the registrar also keeps track of the connection over which it
received this registration. received this registration.
The registrar saves the instance-id The registrar saves the instance-id
("urn:uuid:00000000-0000-1000-8000-000A95A0E128") and reg-id ("1") ("urn:uuid:00000000-0000-1000-8000-000A95A0E128") and reg-id ("1")
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Session Traversal Utilities for NAT (STUN) Session Traversal Utilities for NAT (STUN)
[I-D.ietf-behave-rfc3489bis] server on the SIP signaling port. [I-D.ietf-behave-rfc3489bis] server on the SIP signaling port.
Note: The STUN mechanism is very robust and allows the detection Note: The STUN mechanism is very robust and allows the detection
of a changed IP address and port. Many other options were of a changed IP address and port. Many other options were
considered, but the SIP Working Group selected the STUN-based considered, but the SIP Working Group selected the STUN-based
approach. Approaches using SIP requests were abandoned because approach. Approaches using SIP requests were abandoned because
many believed that good performance and full backwards many believed that good performance and full backwards
compatibility using this method were mutually exclusive. compatibility using this method were mutually exclusive.
4. User Agent Mechanisms 4. User Agent Procedures
4.1. Instance ID Creation 4.1. Instance ID Creation
Each UA MUST have an Instance Identifier Uniform Resource Name (URN) Each UA MUST have an Instance Identifier Uniform Resource Name (URN)
[RFC2141] that uniquely identifies the device. Usage of a URN [RFC2141] that uniquely identifies the device. Usage of a URN
provides a persistent and unique name for the UA instance. It also provides a persistent and unique name for the UA instance. It also
provides an easy way to guarantee uniqueness within the AOR. This provides an easy way to guarantee uniqueness within the AOR. This
URN MUST be persistent across power cycles of the device. The URN MUST be persistent across power cycles of the device. The
Instance ID MUST NOT change as the device moves from one network to Instance ID MUST NOT change as the device moves from one network to
another. another.
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ever have a single SIP UA present, the UUID can include the MAC ever have a single SIP UA present, the UUID can include the MAC
address and be generated at any time because it is guaranteed that address and be generated at any time because it is guaranteed that
no other UUID is being generated at the same time on that physical no other UUID is being generated at the same time on that physical
device. This means the value of the time component of the UUID device. This means the value of the time component of the UUID
can be arbitrarily selected to be any time less than the time when can be arbitrarily selected to be any time less than the time when
the device was manufactured. A time of 0 (as shown in the example the device was manufactured. A time of 0 (as shown in the example
in Section 3.2) is perfectly legal as long as the device knows no in Section 3.2) is perfectly legal as long as the device knows no
other UUIDs were generated at this time on this device. other UUIDs were generated at this time on this device.
If a URN scheme other than UUID is used, the UA MUST only use URNs If a URN scheme other than UUID is used, the UA MUST only use URNs
for which an IETF consensus RFC defines how the specific URN needs to for which an IETF RFC defines how the specific URN needs to be
be constructed and used in the sip.instance Contact parameter for constructed and used in the sip.instance Contact parameter for
outbound behavior. outbound behavior.
To convey its instance-id in both requests and responses, the UA To convey its instance-id in both requests and responses, the UA
includes a "sip.instance" media feature tag as a UA characteristic includes a "sip.instance" media feature tag as a UA characteristic
[RFC3840] . This media feature tag is encoded in the Contact header [RFC3840] . This media feature tag is encoded in the Contact header
field as the "+sip.instance" Contact header field parameter. One field as the "+sip.instance" Contact header field parameter. One
case where a UA may not want to include the sip.instance media case where a UA could prefer to omit the sip.instance media feature
feature tag at all is when it is making an anonymous request or some tag is when it is making an anonymous request or some other privacy
other privacy concern requires that the UA not reveal its identity. concern requires that the UA not reveal its identity.
[RFC3840] defines equality rules for callee capabilities [RFC3840] defines equality rules for callee capabilities
parameters, and according to that specification, the parameters, and according to that specification, the
"sip.instance" media feature tag will be compared by case- "sip.instance" media feature tag will be compared by case-
sensitive string comparison. This means that the URN will be sensitive string comparison. This means that the URN will be
encapsulated by angle brackets ("<" and ">") when it is placed encapsulated by angle brackets ("<" and ">") when it is placed
within the quoted string value of the +sip.instance Contact header within the quoted string value of the +sip.instance Contact header
field parameter. The case-sensitive matching rules apply only to field parameter. The case-sensitive matching rules apply only to
the generic usages defined in the callee capabilities [RFC3841] the generic usages defined in the callee capabilities [RFC3841]
and the caller preferences [RFC3841] specifications. When the and the caller preferences [RFC3841] specifications. When the
instance ID is used in this specification, it is effectively instance ID is used in this specification, it is "extracted" from
"extracted" from the value in the "sip.instance" media feature the value in the "sip.instance" media feature tag. Thus, equality
tag. Thus, equality comparisons are performed using the rules for comparisons are performed using the rules for URN equality that
URN equality that are specific to the scheme in the URN. If the are specific to the scheme in the URN. If the element performing
element performing the comparisons does not understand the URN the comparisons does not understand the URN scheme, it performs
scheme, it performs the comparisons using the lexical equality the comparisons using the lexical equality rules defined in
rules defined in [RFC2141]. Lexical equality could result in two [RFC2141]. Lexical equality could result in two URNs being
URNs being considered unequal when they are actually equal. In considered unequal when they are actually equal. In this specific
this specific usage of URNs, the only element which provides the usage of URNs, the only element which provides the URN is the SIP
URN is the SIP UA instance identified by that URN. As a result, UA instance identified by that URN. As a result, the UA instance
the UA instance MUST provide lexically equivalent URNs in each has to provide lexically equivalent URNs in each registration it
registration it generates. This is likely to be normal behavior generates. This is likely to be normal behavior in any case;
in any case; clients are not likely to modify the value of the clients are not likely to modify the value of the instance ID so
instance ID so that it remains functionally equivalent yet that it remains functionally equivalent yet lexicographically
lexicographically different from previous registrations. different from previous registrations.
4.2. Registrations 4.2. Registrations
4.2.1. Initial Registrations 4.2.1. Initial Registrations
At configuration time, UAs obtain one or more SIP URIs representing At configuration time, UAs obtain one or more SIP URIs representing
the default outbound-proxy-set. This specification assumes the set the default outbound-proxy-set. This specification assumes the set
is determined via any of a number of configuration mechanisms, and is determined via any of a number of configuration mechanisms, and
future specifications can define additional mechanisms such as using future specifications can define additional mechanisms such as using
DNS to discover this set. How the UA is configured is outside the DNS to discover this set. How the UA is configured is outside the
skipping to change at page 14, line 34 skipping to change at page 14, line 36
conserve battery power, for example). If the set has more than one conserve battery power, for example). If the set has more than one
URI, the UAC MUST send a REGISTER request to at least two of the URI, the UAC MUST send a REGISTER request to at least two of the
default outbound proxies from the set. UAs that support this default outbound proxies from the set. UAs that support this
specification MUST include the outbound option tag in a Supported specification MUST include the outbound option tag in a Supported
header field in a REGISTER request. Each of these REGISTER requests header field in a REGISTER request. Each of these REGISTER requests
will use a unique Call-ID. Forming the route set for the request is will use a unique Call-ID. Forming the route set for the request is
outside the scope of this document, but typically results in sending outside the scope of this document, but typically results in sending
the REGISTER such that the topmost Route header field contains a the REGISTER such that the topmost Route header field contains a
loose route to the outbound proxy URI. loose route to the outbound proxy URI.
Registration requests, other than those described in Section 4.2.3, REGISTER requests, other than those described in Section 4.2.3, MUST
MUST include an instance-id media feature tag as specified in include an instance-id media feature tag as specified in Section 4.1.
Section 4.1.
For registration requests in accordance to this specification, the UA For registration requests in accordance to this specification, the UA
MUST include a distinct reg-id parameter in the Contact header field. MUST include reg-id parameter in the Contact header field that is
Each one of these registrations will form a new flow from the UA to distinct from other reg-id parameters used from the same
the proxy. The sequence of reg-id values does not have to be +sip.instance and AOR. Each one of these registrations will form a
sequential but MUST be exactly the same sequence of reg-id values new flow from the UA to the proxy. The sequence of reg-id values
each time the UA instance power cycles or reboots so that the reg-id does not have to be sequential but MUST be exactly the same sequence
values will collide with the previously used reg-id values. This is of reg-id values each time the UA instance power cycles or reboots so
so the registrar can replace the older registrations. that the reg-id values will collide with the previously used reg-id
values. This is so the registrar can replace the older
registrations.
The UAC can situationally decide whether to request outbound The UAC can situationally decide whether to request outbound
behavior by including or omitting the 'reg-id' parameter. For behavior by including or omitting the reg-id Contact header field
example, imagine the outbound-proxy-set contains two proxies in parameter. For example, imagine the outbound-proxy-set contains
different domains, EP1 and EP2. If an outbound-style registration two proxies in different domains, EP1 and EP2. If an outbound-
succeeded for a flow through EP1, the UA might decide to include style registration succeeded for a flow through EP1, the UA might
'outbound' in its Require header field when registering with EP2, decide to include 'outbound' in its Require header field when
in order to insure consistency. Similarly, if the registration registering with EP2, in order to insure consistency. Similarly,
through EP1 did not support outbound, the UA might not register if the registration through EP1 did not support outbound, the UA
with EP2 at all. might not register with EP2 at all.
The UAC MUST indicate that it supports the Path header [RFC3327] The UAC MUST supports the Path header [RFC3327] mechanism, and
mechanism, by including the 'path' option-tag in a Supported header indicate its support by including the 'path' option-tag in a
field value in its REGISTER requests. Other than optionally Supported header field value in its REGISTER requests. Other than
examining the Path vector in the response, this is all that is optionally examining the Path vector in the response, this is all
required of the UAC to support Path. that is required of the UAC to support Path.
The UAC examines successful registration responses for the presence The UAC examines successful registration responses for the presence
of an 'outbound' option-tag in a Require header field value. of an outbound option-tag in a Require header field value. Presence
Presence of this option-tag indicates that the registrar is compliant of this option-tag indicates that the registrar is compliant with
with this specification, and that any edge proxies which needed to this specification, and that any edge proxies which needed to
participate are also compliant. If the registrar did not support participate are also compliant. If the registrar did not support
outbound, the UA may have unintentionally registered an unroutable outbound, the UA has potentially registered an un-routable contact.
contact. It is the responsiblity of the UA to remove any It is the responsibility of the UA to remove any inappropriate
inappropriate Contacts. Contacts.
If outbound registration succeeded, as indicated by the presence of If outbound registration succeeded, as indicated by the presence of
the outbound option-tag in the Require header field of a successful the outbound option-tag in the Require header field of a successful
registration response, the UA begins sending keepalives as described registration response, the UA begins sending keepalives as described
in Section 4.4. in Section 4.4.
Note that the UA needs to honor 503 (Service Unavailable) responses Note that the UA needs to honor 503 (Service Unavailable) responses
to registrations as described in [RFC3261] and [RFC3263]. In to registrations as described in [RFC3261] and [RFC3263]. In
particular, implementors should note that when receiving a 503 particular, implementors should note that when receiving a 503
(Service Unavailable) response with a Retry-After header field, the (Service Unavailable) response with a Retry-After header field, the
UA is expected to wait the indicated amount of time and retry the UA is expected to wait the indicated amount of time and retry the
registration. A Retry-After header field value of 0 is valid and registration. A Retry-After header field value of 0 is valid and
indicates the UA is expected to retry the REGISTER immediately. indicates the UA is expected to retry the REGISTER request
Implementations need to ensure that when retrying the REGISTER, they immediately. Implementations need to ensure that when retrying the
revisit the DNS resolution results such that the UA can select an REGISTER request, they revisit the DNS resolution results such that
alternate host from the one chosen the previous time the URI was the UA can select an alternate host from the one chosen the previous
resolved. time the URI was resolved.
If the registering UA receives a 439 (First Hop Lacks Outbound If the registering UA receives a 439 (First Hop Lacks Outbound
Support) response to a REGISTER request, it MAY re-attempt Support) response to a REGISTER request, it MAY re-attempt
registration without using the outbound mechanism (subject to local registration without using the outbound mechanism (subject to local
policy at the client). If the client has one or more alternate policy at the client). If the client has one or more alternate
outbound proxies available, it MAY re-attempt registration through outbound proxies available, it MAY re-attempt registration through
such outbound proxies. See Section 11.6 for more information on the such outbound proxies. See Section 11.6 for more information on the
439 response code. 439 response code.
4.2.2. Subsequent REGISTER requests 4.2.2. Subsequent REGISTER requests
Re-registrations and single Contact de-registrations use the same Registrations for refreshing a binding and for removing a binding use
instance-id and reg-id values as the corresponding initial the same instance-id and reg-id values as the corresponding initial
registration. Re-registrations which merely refresh an existing registration where the binding was added. Registrations which merely
valid registration are sent over the same flow as the original refresh an existing binding are sent over the same flow as the
registration. original registration where the binding was added.
If a re-registration is rejected with a recoverable error response, If a re-registration is rejected with a recoverable error response,
for example by a 503 (Service Unavailable) containing a Retry-After for example by a 503 (Service Unavailable) containing a Retry-After
header, the UAC SHOULD NOT tear down the corresponding flow if the header, the UAC SHOULD NOT tear down the corresponding flow if the
flow uses a connection-oriented transport such as TCP. As long as flow uses a connection-oriented transport such as TCP. As long as
"pongs" are received in response to "pings", the flow SHOULD be kept "pongs" are received in response to "pings", the flow SHOULD be kept
active until a non-recoverable error response is received. This active until a non-recoverable error response is received. This
prevents unnecessary closing and opening of connections. prevents unnecessary closing and opening of connections.
4.2.3. Non Outbound Registrations 4.2.3. Non Outbound Registrations
In an initial registration, a User Agent MUST NOT include a reg-id In an initial registration, a User Agent MUST NOT include a reg-id
header parameter in the Contact header field if the registering UA is header parameter in the Contact header field if the registering UA is
not the same instance as the UA referred to by the target Contact not the same instance as the UA referred to by the target Contact
header field. (This practice is occasionally used to install header field. (This practice is occasionally used to install
forwarding policy into registrars.) forwarding policy into registrars.)
A UAC also MUST NOT include an instance-id or reg-id parameter in a A UAC also MUST NOT include an instance-id feature taf or reg-id
request to unregister all Contacts (a single Contact header field Contact header field parameter in a request to un-register all
value with the value of "*"). Contacts (a single Contact header field value with the value of "*").
4.3. Sending Non-REGISTER Requests 4.3. Sending Non-REGISTER Requests
When a UAC is about to send a request, it first performs normal When a UAC is about to send a request, it first performs normal
processing to select the next hop URI. The UA can use a variety of processing to select the next hop URI. The UA can use a variety of
techniques to compute the route set and accordingly the next hop URI. techniques to compute the route set and accordingly the next hop URI.
Discussion of these techniques is outside the scope of this document. Discussion of these techniques is outside the scope of this document.
UAs that support this specification SHOULD include the outbound UAs that support this specification SHOULD include the outbound
option tag in a Supported header field in a non-Register request. option tag in a Supported header field in a request that is not a
REGISTER request.
The UAC performs normal DNS resolution on the next hop URI (as The UAC performs normal DNS resolution on the next hop URI (as
described in [RFC3263]) to find a protocol, IP address, and port. described in [RFC3263]) to find a protocol, IP address, and port.
For protocols that don't use TLS, if the UAC has an existing flow to For protocols that don't use TLS, if the UAC has an existing flow to
this IP address, and port with the correct protocol, then the UAC this IP address, and port with the correct protocol, then the UAC
MUST use the existing connection. For TLS protocols, there MUST also MUST use the existing connection. For TLS protocols, there MUST also
be a match between the host production in the next hop and one of the be a match between the host production in the next hop and one of the
URIs contained in the subjectAltName in the peer certificate. If the URIs contained in the subjectAltName in the peer certificate. If the
UAC cannot use one of the existing flows, then it SHOULD form a new UAC cannot use one of the existing flows, then it SHOULD form a new
flow by sending a datagram or opening a new connection to the next flow by sending a datagram or opening a new connection to the next
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Under specific circumstances, a UAC might be allowed to send STUN Under specific circumstances, a UAC might be allowed to send STUN
keep alives even if the procedures in Section 4.2 were not completed, keep alives even if the procedures in Section 4.2 were not completed,
provided that there is an explicit indication that the target first provided that there is an explicit indication that the target first
hop SIP node supports STUN keep alives. This applies for example to hop SIP node supports STUN keep alives. This applies for example to
a non-registering UA or to a case where the UA registration a non-registering UA or to a case where the UA registration
succeeded, but the response did not include the outbound option-tag succeeded, but the response did not include the outbound option-tag
in the Require header field. in the Require header field.
Note that a UA can "always" send a double CRLF (a "ping") over Note that a UA can "always" send a double CRLF (a "ping") over
connection-oriented transports as this is already allowed by Section connection-oriented transports as this is already allowed by
7.5/[RFC3261], However a UA that did not register using outbound Section 7.5/[RFC3261], However a UA that did not register using
registration cannot expect a CRLF in response (a "pong") unless the outbound registration cannot expect a CRLF in response (a "pong")
UA has an explicit indication that CRLF keepalives are supported as unless the UA has an explicit indication that CRLF keep alives are
described in this section. Likewise, a UA that did not successfully supported as described in this section. Likewise, a UA that did
register with outbound procedures needs explicit indication that the not successfully register with outbound procedures needs explicit
target first hop SIP node supports STUN keepalives before it can send indication that the target first hop SIP node supports STUN keep
any STUN messages. alives before it can send any STUN messages.
A configuration option indicating keepalive support for a specific A configuration option indicating keepalive support for a specific
target is considered an explicit indication. If these conditions are target is considered an explicit indication. If these conditions are
satisfied, the UA sends its keepalives according to the same satisfied, the UA sends its keepalives according to the same
guidelines described in the rest of this section as UAs which guidelines described in the rest of this section as UAs which
register. register.
The UA needs to detect when a specific flow fails. The UA actively The UA needs to detect when a specific flow fails. The UA actively
tries to detect failure by periodically sending keep alive messages tries to detect failure by periodically sending keep alive messages
using one of the techniques described in Section 4.4.1 or using one of the techniques described in Section 4.4.1 or
Section 4.4.2. If a flow with a registration has failed, the UA Section 4.4.2. If a flow with a registration has failed, the UA
follows the procedures in Section 4.2 to form a new flow to replace follows the procedures in Section 4.2 to form a new flow to replace
the failed one. the failed one.
When a successful registration response contains the Flow-Timer When a successful registration response contains the Flow-Timer
header field, the value of this header field is the number of seconds header field, the value of this header field is the number of seconds
the server is prepared to wait without seeing keepalives before it the server is prepared to wait without seeing keepalives before it
considers the corresponding flow dead. The UA MUST send keepalives considers the corresponding flow dead. The UA MUST send keepalives
at least as often as this number of seconds. If the UA uses the at least as often as this number of seconds. If the UA uses the
server recommended keepalive frequency it SHOULD send its keepalives server recommended keep alive frequency it SHOULD send its keep
so that the interval between each keepalive is randomly distributed alives so that the interval between each keep alive is randomly
between 80% and 100% of the server provided time. For example, if distributed between 80% and 100% of the server provided time. For
the server suggests 120 seconds, the UA would send each keepalive example, if the server suggests 120 seconds, the UA would send each
with a different frequency between 95 and 120 seconds. keep alive with a different frequency between 95 and 120 seconds.
If no Flow-Timer header field was present in a register response for If no Flow-Timer header field was present in a register response for
this flow, the UA can send keepalives at its discretion. The this flow, the UA can send keepalives at its discretion. The
sections below provide RECOMMENDED default values for these sections below provide RECOMMENDED default values for these keep
keepalives. alives.
The client needs to perform normal [RFC3263] SIP DNS resolution on The client needs to perform normal [RFC3263] SIP DNS resolution on
the URI from the outbound-proxy-set to pick a transport. Once a the URI from the outbound-proxy-set to pick a transport. Once a
transport is selected, the UA selects the keep alive approach that is transport is selected, the UA selects the keep alive approach that is
recommended for that transport. recommended for that transport.
4.4.1. Keep alive with CRLF 4.4.1. Keep alive with CRLF
This approach MUST only be used with connection oriented transports This approach MUST only be used with connection oriented transports
such as TCP or SCTP. such as TCP or SCTP.
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Response is received after 7 retransmissions (16 times the STUN "RTO" Response is received after 7 retransmissions (16 times the STUN "RTO"
timer--RTO is an estimate of round-trip time), the UA considers the timer--RTO is an estimate of round-trip time), the UA considers the
flow failed. If the XOR-MAPPED-ADDRESS in the STUN Binding Response flow failed. If the XOR-MAPPED-ADDRESS in the STUN Binding Response
changes, the UA MUST treat this event as a failure on the flow. changes, the UA MUST treat this event as a failure on the flow.
4.5. Flow Recovery 4.5. Flow Recovery
When a flow used for registration (through a particular URI in the When a flow used for registration (through a particular URI in the
outbound-proxy-set) fails, the UA needs to form a new flow to replace outbound-proxy-set) fails, the UA needs to form a new flow to replace
the old flow and replace any registrations that were previously sent the old flow and replace any registrations that were previously sent
over this flow. Each new registration MUST have the same reg-id as over this flow. Each new registration MUST have the same reg-id
the registration it replaces. This is done in much the same way as value as the registration it replaces. This is done in much the same
forming a brand new flow as described in Section 4.2; however, if way as forming a brand new flow as described in Section 4.2; however,
there is a failure in forming this flow, the UA needs to wait a if there is a failure in forming this flow, the UA needs to wait a
certain amount of time before retrying to form a flow to this certain amount of time before retrying to form a flow to this
particular next hop. particular next hop.
The amount of time to wait depends if the previous attempt at The amount of time to wait depends if the previous attempt at
establishing a flow was successful. For the purposes of this establishing a flow was successful. For the purposes of this
section, a flow is considered successful if outbound registration section, a flow is considered successful if outbound registration
succeeded, and if keep alives are in use on this flow, at least one succeeded, and if keep alives are in use on this flow, at least one
subsequent keep alive response was received. subsequent keep alive response was received.
The number of seconds to wait is computed in the following way. If The number of seconds to wait is computed in the following way. If
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To be explicitly clear on the boundary conditions: when the UA boots To be explicitly clear on the boundary conditions: when the UA boots
it immediately tries to register. If this fails and no registration it immediately tries to register. If this fails and no registration
on other flows succeed, the first retry happens somewhere between 30 on other flows succeed, the first retry happens somewhere between 30
and 60 seconds after the failure of the first registration request. and 60 seconds after the failure of the first registration request.
If the number of consecutive-failures is large enough that the If the number of consecutive-failures is large enough that the
maximum of 1800 seconds is reached, the UA will keep trying maximum of 1800 seconds is reached, the UA will keep trying
indefinitely with a random time of 15 to 30 minutes between each indefinitely with a random time of 15 to 30 minutes between each
attempt. attempt.
5. Edge Proxy Mechanisms 5. Edge Proxy Procedures
5.1. Processing Register Requests 5.1. Processing Register Requests
When an Edge Proxy receives a registration request with a reg-id When an Edge Proxy receives a registration request with a reg-id
header parameter in the Contact header field, it needs to determine header field parameter in the Contact header field, it needs to
if it (the edge proxy) will have to be visited for any subsequent determine if it (the edge proxy) will have to be visited for any
requests sent to the user agent identified in the Contact header subsequent requests sent to the user agent identified in the Contact
field, or not. If the edge proxy is the first hop, as indicated by header field, or not. If the edge proxy is the first hop, as
the Via header field, it always inserts its URI in a Path header indicated by the Via header field, it MUST insert its URI in a Path
field value as described in [RFC3327]. If it is not the first hop, header field value as described in [RFC3327]. If it is not the first
it might still decide to add itself to the Path header based on local hop, it might still decide to add itself to the Path header based on
policy. In addition, if the Edge Proxy is the first SIP node after local policy. In addition, if the Edge Proxy is the first SIP node
the UAC, the edge proxy either MUST store a "flow token" (containing after the UAC, the edge proxy either MUST store a "flow token"
information about the flow from the previous hop) in its Path URI or (containing information about the flow from the previous hop) in its
reject the request. The flow token MUST be an identifier that is Path URI or reject the request. The flow token MUST be an identifier
unique to this network flow. The flow token MAY be placed in the that is unique to this network flow. The flow token MAY be placed in
userpart of the URI. In addition, the first node MUST include an the userpart of the URI. In addition, the first node MUST include an
'ob' URI parameter in its Path header field value. If the Edge Proxy 'ob' URI parameter in its Path header field value. If the Edge Proxy
is not the first SIP node after the UAC it MUST NOT place an 'ob' URI is not the first SIP node after the UAC it MUST NOT place an ob URI
parameter in a Path header field value. The Edge Proxy can determine parameter in a Path header field value. The Edge Proxy can determine
if it is the first hop by examining the Via header field. if it is the first hop by examining the Via header field.
5.2. Generating Flow Tokens 5.2. Generating Flow Tokens
A trivial but impractical way to satisfy the flow token requirement A trivial but impractical way to satisfy the flow token requirement
in Section 5.1 involves storing a mapping between an incrementing in Section 5.1 involves storing a mapping between an incrementing
counter and the connection information; however this would require counter and the connection information; however this would require
the Edge Proxy to keep an infeasible amount of state. It is unclear the Edge Proxy to keep an infeasible amount of state. It is unclear
when this state could be removed and the approach would have problems when this state could be removed and the approach would have problems
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the HMAC and S are base64 encoded, as defined in [RFC4648], and the HMAC and S are base64 encoded, as defined in [RFC4648], and
used as the flow identifier. When using IPv4 addresses, this will used as the flow identifier. When using IPv4 addresses, this will
result in a 32-octet identifier. result in a 32-octet identifier.
5.3. Forwarding Non-REGISTER Requests 5.3. Forwarding Non-REGISTER Requests
When an Edge Proxy receives a request, it applies normal routing When an Edge Proxy receives a request, it applies normal routing
procedures with the following additions. If the Edge Proxy receives procedures with the following additions. If the Edge Proxy receives
a request where the edge proxy is the host in the topmost Route a request where the edge proxy is the host in the topmost Route
header field value, and the Route header field value contains a flow header field value, and the Route header field value contains a flow
token, the proxy may need to do additional processing described in token, the proxy MAY need to do additional processing described in
the rest of this section. Otherwise the edge proxy skips the the rest of this section. Otherwise the edge proxy skips the
procedures in this section, removes itself from the Route header procedures in this section, removes itself from the Route header
field, and continues processing the request. field, and continues processing the request.
The proxy decodes the flow token and compares the flow in the flow The proxy decodes the flow token and compares the flow in the flow
token with the source of the request to determine if this is an token with the source of the request to determine if this is an
"incoming" or "outgoing" request. "incoming" or "outgoing" request.
If the flow in the flow token identified by the topmost Route header If the flow in the flow token identified by the topmost Route header
field value matches the source IP address and port of the request, field value matches the source IP address and port of the request,
the request is an "outgoing" request, otherwise, it is an "incoming" the request is an "outgoing" request, otherwise, it is an "incoming"
request. request.
5.3.1. Processing Incoming Requests 5.3.1. Processing Incoming Requests
If the Route header value contains an 'ob' parameter, the Route If the Route header value contains an ob URI parameter, the Route
header was probably copied from the Path header in a registration. header was probably copied from the Path header in a registration.
If the Route header value contains an 'ob' parameter, and the request If the Route header value contains an ob URI parameter, and the
is a new dialog-forming request, the proxy needs to adjust the route request is a new dialog-forming request, the proxy needs to adjust
set to insure that subsequent requests in the dialog can be delivered the route set to insure that subsequent requests in the dialog can be
over a valid flow to the UA instance identified by the flow token. delivered over a valid flow to the UA instance identified by the flow
token.
A simple approach to satisfy this requirement is for the proxy to A simple approach to satisfy this requirement is for the proxy to
add a Record-Route header field value that contains the flow- add a Record-Route header field value that contains the flow-
token, by copying the URI in the Route header minus the 'ob' token, by copying the URI in the Route header minus the 'ob'
parameter. parameter.
Next, whether the Route header field contained an 'ob' parameter or Next, whether the Route header field contained an ob URI parameter or
not, the proxy removes the Route header field value and forwards the not, the proxy removes the Route header field value and forwards the
request over the 'logical flow' identified by the flow token, that is request over the 'logical flow' identified by the flow token, that is
known to deliver data to the specific target UA instance. If the known to deliver data to the specific target UA instance. If the
flow token has been tampered with, the proxy SHOULD send a 403 flow token has been tampered with, the proxy SHOULD send a 403
(Forbidden) response. If the flow no longer exists the proxy SHOULD (Forbidden) response. If the flow no longer exists the proxy SHOULD
send a 430 (Flow Failed) response to the request. send a 430 (Flow Failed) response to the request.
Proxies which used the example algorithm described in Section 5.2 to Proxies which used the example algorithm described in Section 5.2 to
form a flow token follow the procedures below to determine the form a flow token follow the procedures below to determine the
correct flow. To decode the flow token, take the flow identifier in correct flow. To decode the flow token, take the flow identifier in
the user portion of the URI and base64 decode it, then verify the the user portion of the URI and base64 decode it, then verify the
HMAC is correct by recomputing the HMAC and checking that it matches. HMAC is correct by recomputing the HMAC and checking that it matches.
If the HMAC is not correct, the request has been tampered with. If the HMAC is not correct, the request has been tampered with.
5.3.2. Processing Outgoing Requests 5.3.2. Processing Outgoing Requests
For mid-dialog requests to work with outbound UAs, the requests need For mid-dialog requests to work with outbound UAs, the requests need
to be forwarded over some valid flow to the appropriate UA instance. to be forwarded over some valid flow to the appropriate UA instance.
If the Edge Proxy receives an outgoing dialog-forming request, the If the Edge Proxy receives an outgoing dialog-forming request, the
Edge Proxy can use the presence of the "ob" parameter in the UAC's Edge Proxy can use the presence of the ob URI parameter in the UAC's
Contact URI (or topmost Route header field) to determine if the Edge Contact URI (or topmost Route header field) to determine if the Edge
Proxy needs to assist in mid-dialog request routing. Proxy needs to assist in mid-dialog request routing.
Implementation note: Specific procedures at the edge proxy to ensure Implementation note: Specific procedures at the edge proxy to ensure
that mid-dialog requests are routed over an existing flow are not that mid-dialog requests are routed over an existing flow are not
part of this specification. However, an approach such as having part of this specification. However, an approach such as having
the Edge Proxy add a Record-Route header with a flow token is one the Edge Proxy add a Record-Route header with a flow token is one
way to ensure that mid-dialog requests are routed over the correct way to ensure that mid-dialog requests are routed over the correct
flow. flow.
skipping to change at page 23, line 48 skipping to change at page 24, line 6
Section 8. Section 8.
When a server receives a double CRLF sequence between SIP messages on When a server receives a double CRLF sequence between SIP messages on
a connection oriented transport such as TCP or SCTP, it MUST a connection oriented transport such as TCP or SCTP, it MUST
immediately respond with a single CRLF over the same connection. immediately respond with a single CRLF over the same connection.
The last proxy to forward a successful registration response to a UA The last proxy to forward a successful registration response to a UA
MAY include a Flow-Timer header field if the response contains the MAY include a Flow-Timer header field if the response contains the
outbound option-tag in a Require header field value in the response. outbound option-tag in a Require header field value in the response.
6. Registrar Mechanisms 6. Registrar Procedures
This specification updates the definition of a binding in [RFC3261] This specification updates the definition of a binding in [RFC3261]
Section 10 and [RFC3327] Section 5.3. Section 10 and [RFC3327] Section 5.3.
Registrars which implement this specification MUST support the Path Registrars which implement this specification MUST support the Path
header mechanism [RFC3327]. header mechanism [RFC3327].
When receiving a REGISTER request, the registrar MUST check from its When receiving a REGISTER request, the registrar MUST check from its
Via header field if the registrar is the first hop or not. If the Via header field if the registrar is the first hop or not. If the
registrar is not the first hop, it MUST examine the Path header of registrar is not the first hop, it MUST examine the Path header of
the request. If the Path header field is missing or it exists but the request. If the Path header field is missing or it exists but
the first URI does not have an 'ob' URI parameter, then outbound the first URI does not have an ob URI parameter, then outbound
processing MUST NOT be applied to the registration. In this case, processing MUST NOT be applied to the registration. In this case,
the following processing applies: if the REGISTER request contains the following processing applies: if the REGISTER request contains
the a 'reg-id' and the 'outbound' option tag in a 'Supported' header the reg-id and the outbound option tag in a Supported header field,
field, then the registrar MUST respond to the REGISTER request with a then the registrar MUST respond to the REGISTER request with a 439
439 (First Hop Lacks Outbound Support) response; otherwise, the (First Hop Lacks Outbound Support) response; otherwise, the registrar
registrar MUST ignore the reg-id parameter of the Contact header. MUST ignore the reg-id parameter of the Contact header. See
See Section 11.6 for more information on the 439 response code. Section 11.6 for more information on the 439 response code.
A Contact header field value with an instance-id but no reg-id is A Contact header field value with an instance-id media feature tag
valid (this combination can be used in the GRUU [I-D.ietf-sip-gruu] but no reg-id header field parameter is valid (this combination can
specification), but one with a reg-id but no instance-id is not. If be used in the GRUU [I-D.ietf-sip-gruu] specification), but one with
the registrar processes a Contact header field value with a reg-id a reg-id but no instance-id is not. If the registrar processes a
but no instance-id, it simply ignores the reg-id parameter. Contact header field value with a reg-id but no instance-id, it
simply ignores the reg-id parameter.
A registration containing a reg-id parameter and a non-zero A registration containing a reg-id header field parameter and a non-
expiration is used to register a single UA instance over a single zero expiration is used to register a single UA instance over a
flow, and can also de-register any Contact header fields with zero single flow, and can also de-register any Contact header fields with
expiration. Therefore if the Contact header field contains more than zero expiration. Therefore if the Contact header field contains more
one header field value with a non-zero expiration and any of these than one header field value with a non-zero expiration and any of
header field values contain a 'reg-id' parameter, the entire these header field values contain a reg-id Contact header field
registration SHOULD be rejected with a 400 (Bad Request) response. parameter, the entire registration SHOULD be rejected with a 400 (Bad
The justification for recommending rejection versus making it Request) response. The justification for recommending rejection
mandatory is that the receiver is allowed by [RFC3261] to squelch versus making it mandatory is that the receiver is allowed by
(not respond to) excessively malformed or malicious messages. [RFC3261] to squelch (not respond to) excessively malformed or
malicious messages.
If the Contact header did not contain a 'reg-id' parameter or if that If the Contact header did not contain a reg-id Contact header field
parameter was ignored (as described above) the registrar MUST NOT parameter or if that parameter was ignored (as described above) the
include the 'outbound' option-tag in the Require header field of its registrar MUST NOT include the outbound option-tag in the Require
response. header field of its response.
The registrar MUST be prepared to receive, simultaneously for the The registrar MUST be prepared to receive, simultaneously for the
same AOR, some registrations that use instance-id and reg-id and some same AOR, some registrations that use instance-id and reg-id and some
registrations that do not. The Registrar MAY be configured with registrations that do not. The Registrar MAY be configured with
local policy to reject any registrations that do not include the local policy to reject any registrations that do not include the
instance-id and reg-id, or with Path header field values that do not instance-id and reg-id, or with Path header field values that do not
contain the 'ob' parameter. If the Contact header field does not contain the ob URI parameter. If the Contact header field does not
contain a '+sip.instance' media feature parameter, the registrar contain a '+sip.instance' media feature parameter, the registrar
processes the request using the Contact binding rules in [RFC3261]. processes the request using the Contact binding rules in [RFC3261].
When a '+sip.instance' media feature parameter and a reg-id parameter When a '+sip.instance' media feature parameter and a reg-id Contact
are present in a Contact header field of a REGISTER request (after header field parameter are present in a Contact header field of a
the Contact header validation as described above), the corresponding REGISTER request (after the Contact header validation as described
binding is between an AOR and the combination of the instance-id above), the corresponding binding is between an AOR and the
(from the +sip.instance media feature parameter) and the value of combination of the instance-id (from the +sip.instance media feature
reg-id parameter. The registrar MUST store in the binding the parameter) and the value of reg-id Contact header field parameter
Contact URI, all the Contact head field parameters, and any Path parameter. The registrar MUST store in the binding the Contact URI,
header field values. (Even though the Contact URI is not used for all the Contact header field parameters, and any Path header field
binding comparisons, it is still needed by the authoritative proxy to values. (Even though the Contact URI is not used for binding
form the target set.) The Registrar MUST include the 'outbound' comparisons, it is still needed by the authoritative proxy to form
option-tag (defined in Section 11.2) in a Require header field value the target set.) The Registrar MUST include the outbound option-tag
in its response to the REGISTER request. (defined in Section 11.4) in a Require header field value in its
response to the REGISTER request.
If the UAC has a direct flow with the registrar, the registrar MUST If the UAC has a direct flow with the registrar, the registrar MUST
store enough information to uniquely identify the network flow over store enough information to uniquely identify the network flow over
which the request arrived. For common operating systems with TCP, which the request arrived. For common operating systems with TCP,
this would typically just be the handle to the file descriptor where this would typically just be the handle to the file descriptor where
the handle would become invalid if the TCP session was closed. For the handle would become invalid if the TCP session was closed. For
common operating systems with UDP this would typically be the file common operating systems with UDP this would typically be the file
descriptor for the local socket that received the request, the local descriptor for the local socket that received the request, the local
interface, and the IP address and port number of the remote side that interface, and the IP address and port number of the remote side that
sent the request. The registrar MAY store this information by adding sent the request. The registrar MAY store this information by adding
skipping to change at page 25, line 39 skipping to change at page 25, line 49
If the registrar receives a re-registration for a specific If the registrar receives a re-registration for a specific
combination of AOR, instance-id and reg-id values, the registrar MUST combination of AOR, instance-id and reg-id values, the registrar MUST
update any information that uniquely identifies the network flow over update any information that uniquely identifies the network flow over
which the request arrived if that information has changed, and SHOULD which the request arrived if that information has changed, and SHOULD
update the time the binding was last updated. update the time the binding was last updated.
To be compliant with this specification, registrars which can receive To be compliant with this specification, registrars which can receive
SIP requests directly from a UAC without intervening edge proxies SIP requests directly from a UAC without intervening edge proxies
MUST implement the same keep alive mechanisms as Edge Proxies MUST implement the same keep alive mechanisms as Edge Proxies
(Section 5.4). Registrars with a direct flow with a UA MAY include a (Section 5.4). Registrars with a direct flow with a UA MAY include a
Flow-Timer header in a 200-class registration response which includes Flow-Timer header in a 2XX class registration response which includes
the outbound option-tag in the Require header. the outbound option-tag in the Require header.
7. Authoritative Proxy Mechanisms: Forwarding Requests 7. Authoritative Proxy Procedures: Forwarding Requests
When a proxy uses the location service to look up a registration When a proxy uses the location service to look up a registration
binding and then proxies a request to a particular contact, it binding and then proxies a request to a particular contact, it
selects a contact to use normally, with a few additional rules: selects a contact to use normally, with a few additional rules:
o The proxy MUST NOT populate the target set with more than one o The proxy MUST NOT populate the target set with more than one
contact with the same AOR and instance-id at a time. contact with the same AOR and instance-id at a time.
o If a request for a particular AOR and instance-id fails with a 430 o If a request for a particular AOR and instance-id fails with a 430
(Flow Failed) response, the proxy SHOULD replace the failed branch (Flow Failed) response, the proxy SHOULD replace the failed branch
with another target (if one is available) with the same AOR and with another target (if one is available) with the same AOR and
instance-id, but a different reg-id. instance-id, but a different reg-id.
o If the proxy receives a final response from a branch other than a o If the proxy receives a final response from a branch other than a
408 (Request Timeout) or a 430 (Flow Failed) response, the proxy 408 (Request Timeout) or a 430 (Flow Failed) response, the proxy
MUST NOT forward the same request to another target representing MUST NOT forward the same request to another target representing
the same AOR and instance-id. The targeted instance has already the same AOR and instance-id. The targeted instance has already
provided its response. provided its response.
skipping to change at page 26, line 43 skipping to change at page 26, line 51
set that use that flow (regardless of AOR). Examples of this are a set that use that flow (regardless of AOR). Examples of this are a
TCP socket closing or receiving a destination unreachable ICMP error TCP socket closing or receiving a destination unreachable ICMP error
on a UDP flow. Similarly, if a proxy closes a file descriptor, it on a UDP flow. Similarly, if a proxy closes a file descriptor, it
MUST invalidate all the bindings in the target set with flows that MUST invalidate all the bindings in the target set with flows that
use that file descriptor. use that file descriptor.
8. STUN Keep alive Processing 8. STUN Keep alive Processing
This section describes changes to the SIP transport layer that allow This section describes changes to the SIP transport layer that allow
SIP and STUN [I-D.ietf-behave-rfc3489bis] Binding Requests to be SIP and STUN [I-D.ietf-behave-rfc3489bis] Binding Requests to be
mixed over the same flow. This constitues a new STUN usage. The mixed over the same flow. This constitutes a new STUN usage. The
STUN messages are used to verify that connectivity is still available STUN messages are used to verify that connectivity is still available
over a UDP flow, and to provide periodic keep alives. Note that over a UDP flow, and to provide periodic keep alives. These STUN
these STUN keep alives are always sent to the next SIP hop. STUN keep alives are always sent to the next SIP hop. STUN messages are
messages are not delivered end-to-end. not delivered end-to-end.
The only STUN messages required by this usage are Binding Requests, The only STUN messages required by this usage are Binding Requests,
Binding Responses, and Binding Error Responses. The UAC sends Binding Responses, and Binding Error Responses. The UAC sends
Binding Requests over the same UDP flow that is used for sending SIP Binding Requests over the same UDP flow that is used for sending SIP
messages. These Binding Requests do not require any STUN attributes messages. These Binding Requests do not require any STUN attributes.
except the XOR-MAPPED-ADDRESS and never use any form of The corresponding Binding Responses do not require any STUN
authentication. The UAS, proxy, or registrar responds to a valid attributes except the XOR-MAPPED-ADDRESS. The UAS, proxy, or
Binding Request with a Binding Response which MUST include the XOR- registrar responds to a valid Binding Request with a Binding Response
MAPPED-ADDRESS attribute. which MUST include the XOR-MAPPED-ADDRESS attribute.
If a server compliant to this section receives SIP requests on a If a server compliant to this section receives SIP requests on a
given interface and UDP port, it MUST also provide a limited version given interface and UDP port, it MUST also provide a limited version
of a STUN server on the same interface and UDP port. of a STUN server on the same interface and UDP port.
It is easy to distinguish STUN and SIP packets sent over UDP, It is easy to distinguish STUN and SIP packets sent over UDP,
because the first octet of a STUN Binding method has a value of 0 because the first octet of a STUN Binding method has a value of 0
or 1 while the first octet of a SIP message is never a 0 or 1. or 1 while the first octet of a SIP message is never a 0 or 1.
Because sending and receiving binary STUN data on the same ports used Because sending and receiving binary STUN data on the same ports used
for SIP is a significant and non-backwards compatible change to RFC for SIP is a significant and non-backwards compatible change to RFC
3261, this section requires a number of checks before sending STUN 3261, this section requires a number of checks before sending STUN
messages to a SIP node. If a SIP node sends STUN requests (for messages to a SIP node. If a SIP node sends STUN requests (for
example due to incorrect configuration) despite these warnings, the example due to incorrect configuration) despite these warnings, the
node could be blacklisted for UDP traffic. node could be blacklisted for UDP traffic.
A SIP node MUST NOT send STUN requests over a flow unless it has an A SIP node MUST NOT send STUN requests over a flow unless it has an
explicit indication that the target next hop SIP server claims to explicit indication that the target next hop SIP server claims to
support this specification. Note that UACs MUST NOT use an ambiguous support this specification. UACs MUST NOT use an ambiguous
configuration option such as "Work through NATs?" or "Do Keep configuration option such as "Work through NATs?" or "Do Keep
alives?" to imply next hop STUN support. A UAC MAY use the presence alives?" to imply next hop STUN support. A UAC MAY use the presence
of an 'ob' parameter in the Path header in a registration response as of an ob URI parameter in the Path header in a registration response
an indication that its first edge proxy supports the keep alives as an indication that its first edge proxy supports the keep alives
defined in this document. defined in this document.
Typically, a SIP node first sends a SIP request and waits to Typically, a SIP node first sends a SIP request and waits to
receive a 200-class response over a flow to a new target receive a 2XX class response over a flow to a new target
destination, before sending any STUN messages. When scheduled for destination, before sending any STUN messages. When scheduled for
the next NAT refresh, the SIP node sends a STUN request to the the next NAT refresh, the SIP node sends a STUN request to the
target. target.
Once a flow is established, failure of a STUN request (including its Once a flow is established, failure of a STUN request (including its
retransmissions) is considered a failure of the underlying flow. For retransmissions) is considered a failure of the underlying flow. For
SIP over UDP flows, if the XOR-MAPPED-ADDRESS returned over the flow SIP over UDP flows, if the XOR-MAPPED-ADDRESS returned over the flow
changes, this indicates that the underlying connectivity has changed, changes, this indicates that the underlying connectivity has changed,
and is considered a flow failure. and is considered a flow failure.
skipping to change at page 28, line 31 skipping to change at page 28, line 35
both zeroes. This, combined with the magic cookie, aids in both zeroes. This, combined with the magic cookie, aids in
differentiating STUN packets from other protocols when STUN is differentiating STUN packets from other protocols when STUN is
multiplexed with other protocols on the same port. multiplexed with other protocols on the same port.
9. Example Message Flow 9. Example Message Flow
Below is an example message flow illustrating most of the concepts Below is an example message flow illustrating most of the concepts
discussed in this specification. In many cases, Via, Content-Length discussed in this specification. In many cases, Via, Content-Length
and Max-Forwards headers are omitted for brevity and readability. and Max-Forwards headers are omitted for brevity and readability.
In these examples, "EP1" and "EP2" are outbound proxies, and "Proxy"
is the authoritativeProxy.
The section is subdivided into independent calls flows: however, The section is subdivided into independent calls flows: however,
they are structured in sequential order of an hypothetical sequence they are structured in sequential order of an hypothetical sequence
of call flows. of call flows.
9.1. Subscription to configuration package 9.1. Subscription to configuration package
If the outbound proxy set is already configured on Bob's UA, then If the outbound proxy set is already configured on Bob's UA, then
this subsection can be skipped. Otherwise, if the outbound proxy set this subsection can be skipped. Otherwise, if the outbound proxy set
is learned through the configuration package, Bob's UA sends a is learned through the configuration package, Bob's UA sends a
SUBSCRIBE request for the UA profile configuration package SUBSCRIBE request for the UA profile configuration package
skipping to change at page 29, line 22 skipping to change at page 29, line 24
5)| |<--NOTIFY------------------------| 5)| |<--NOTIFY------------------------|
6)|<--NOTIFY--| | | | 6)|<--NOTIFY--| | | |
7)|---200 OK->| | | | 7)|---200 OK->| | | |
8)| |---200 OK ---------------------->| 8)| |---200 OK ---------------------->|
| | | | | | | | | |
Example Message #1: Example Message #1:
SUBSCRIBE sip:00000000-0000-1000-8000-AABBCCDDEEFF@example.com SUBSCRIBE sip:00000000-0000-1000-8000-AABBCCDDEEFF@example.com
SIP/2.0 SIP/2.0
Via: SIP/2.0/TCP 192.168.1.2;branch=z9hG4bKnlsdkdj2 Via: SIP/2.0/TCP 192.0.2.2;branch=z9hG4bKnlsdkdj2
Max-Forwards: 70 Max-Forwards: 70
From: <anonymous@example.com>;tag=23324 From: <anonymous@example.com>;tag=23324
To: <sip:00000000-0000-1000-8000-AABBCCDDEEFF@example.com> To: <sip:00000000-0000-1000-8000-AABBCCDDEEFF@example.com>
Call-ID: nSz1TWN54x7My0GvpEBj Call-ID: nSz1TWN54x7My0GvpEBj
CSeq: 1 SUBSCRIBE CSeq: 1 SUBSCRIBE
Event: ua-profile ;profile-type=device Event: ua-profile ;profile-type=device
;vendor="example.com";model="uPhone";version="1.1" ;vendor="example.com";model="uPhone";version="1.1"
Expires: 0 Expires: 0
Supported: path, outbound Supported: path, outbound
Accept: message/external-body, application/x-uPhone-config Accept: message/external-body, application/x-uPhone-config
Contact: <sip:192.168.1.2;transport=tcp;ob> Contact: <sip:192.0.2.2;transport=tcp;ob>
;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>" ;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>"
Content-Length: 0 Content-Length: 0
In message #2, EP1 adds the following Record-Route header: In message #2, EP1 adds the following Record-Route header:
Record-Route: Record-Route:
<sip:GopIKSsn0oGLPXRdV9BAXpT3coNuiGKV@ep1.example.com;lr> <sip:GopIKSsn0oGLPXRdV9BAXpT3coNuiGKV@ep1.example.com;lr>
In message #5, the configuration server sends a NOTIFY with an In message #5, the configuration server sends a NOTIFY with an
external URL for Bob to fetch his configuration. The NOTIFY has a external URL for Bob to fetch his configuration. The NOTIFY has a
Subscription-State header that ends the subscription. Subscription-State header that ends the subscription.
Message #5 Message #5
NOTIFY sip:192.168.1.2;transport=tcp;ob SIP/2.0 NOTIFY sip:192.0.2.2;transport=tcp;ob SIP/2.0
Via: SIP/2.0/TCP 192.0.2.5;branch=z9hG4bKn81dd2 Via: SIP/2.0/TCP 192.0.2.5;branch=z9hG4bKn81dd2
Max-Forwards: 70 Max-Forwards: 70
To: <anonymous@example.com>;tag=23324 To: <anonymous@example.com>;tag=23324
From: <sip:00000000-0000-1000-8000-AABBCCDDEEFF@example.com>;tag=0983 From: <sip:00000000-0000-1000-8000-AABBCCDDEEFF@example.com>;tag=0983
Call-ID: nSz1TWN54x7My0GvpEBj Call-ID: nSz1TWN54x7My0GvpEBj
CSeq: 1 NOTIFY CSeq: 1 NOTIFY
Route: <sip:GopIKSsn0oGLPXRdV9BAXpT3coNuiGKV@ep1.example.com;lr> Route: <sip:GopIKSsn0oGLPXRdV9BAXpT3coNuiGKV@ep1.example.com;lr>
Subscription-State: terminated;reason=timeout Subscription-State: terminated;reason=timeout
Event: ua-profile Event: ua-profile
Content-Type: message/external-body; access-type="URL" Content-Type: message/external-body; access-type="URL"
skipping to change at page 31, line 32 skipping to change at page 31, line 32
| | | | | | | | | |
In message #9, Bob's UA sends its first registration through the In message #9, Bob's UA sends its first registration through the
first edge proxy in the outbound-proxy-set by including a loose first edge proxy in the outbound-proxy-set by including a loose
route. The UA includes an instance-id and reg-id in its Contact route. The UA includes an instance-id and reg-id in its Contact
header field value. Note the option-tags in the Supported header. header field value. Note the option-tags in the Supported header.
Message #9 Message #9
REGISTER sip:example.com SIP/2.0 REGISTER sip:example.com SIP/2.0
Via: SIP/2.0/TCP 192.168.1.2;branch=z9hG4bKnashds7 Via: SIP/2.0/TCP 192.0.2.2;branch=z9hG4bKnashds7
Max-Forwards: 70 Max-Forwards: 70
From: Bob <sip:bob@example.com>;tag=7F94778B653B From: Bob <sip:bob@example.com>;tag=7F94778B653B
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Call-ID: 16CB75F21C70 Call-ID: 16CB75F21C70
CSeq: 1 REGISTER CSeq: 1 REGISTER
Supported: path, outbound Supported: path, outbound
Route: <sip:ep1.example.com;lr> Route: <sip:ep1.example.com;lr>
Contact: <sip:bob@192.168.1.2;transport=tcp>;reg-id=1 Contact: <sip:bob@192.0.2.2;transport=tcp>;reg-id=1
;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>" ;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>"
Content-Length: 0 Content-Length: 0
Message #10 is similar. EP1 removes the Route header field value, Message #10 is similar. EP1 removes the Route header field value,
decrements Max-Forwards, and adds its Via header field value. Since decrements Max-Forwards, and adds its Via header field value. Since
EP1 is the first edge proxy, it adds a Path header with a flow token EP1 is the first edge proxy, it adds a Path header with a flow token
and includes the 'ob' parameter. and includes the 'ob' parameter.
Path: <sip:VskztcQ/S8p4WPbOnHbuyh5iJvJIW3ib@ep1.example.com;lr;ob> Path: <sip:VskztcQ/S8p4WPbOnHbuyh5iJvJIW3ib@ep1.example.com;lr;ob>
Since the response to the REGISTER (message #11) contains the Since the response to the REGISTER (message #11) contains the
outbound option-tag in the Require header field, Bob's UA will know outbound option-tag in the Require header field, Bob's UA will know
that the registrar used outbound binding rules. The response also that the registrar used outbound binding rules. The response also
contains the currently active Contacts, the Path for the current contains the currently active Contacts, the Path for the current
registration. registration.
Message #11 Message #11
SIP/2.0 200 OK SIP/2.0 200 OK
Via: SIP/2.0/TCP 192.0.2.15;branch=z9hG4bKnuiqisi Via: SIP/2.0/TCP 192.0.2.15;branch=z9hG4bKnuiqisi
Via: SIP/2.0/TCP 192.168.1.2;branch=z9hG4bKnashds7 Via: SIP/2.0/TCP 192.0.2.2;branch=z9hG4bKnashds7
From: Bob <sip:bob@example.com>;tag=7F94778B653B From: Bob <sip:bob@example.com>;tag=7F94778B653B
To: Bob <sip:bob@example.com>;tag=6AF99445E44A To: Bob <sip:bob@example.com>;tag=6AF99445E44A
Call-ID: 16CB75F21C70 Call-ID: 16CB75F21C70
CSeq: 1 REGISTER CSeq: 1 REGISTER
Supported: path, outbound Supported: path, outbound
Require: outbound Require: outbound
Contact: <sip:bob@192.168.1.2;transport=tcp>;reg-id=1;expires=3600 Contact: <sip:bob@192.0.2.2;transport=tcp>;reg-id=1;expires=3600
;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>" ;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>"
Path: <sip:VskztcQ/S8p4WPbOnHbuyh5iJvJIW3ib@ep1.example.com;lr;ob> Path: <sip:VskztcQ/S8p4WPbOnHbuyh5iJvJIW3ib@ep1.example.com;lr;ob>
Content-Length: 0 Content-Length: 0
The second registration through EP2 (message #13) is similar other The second registration through EP2 (message #13) is similar other
than the Call-ID has changed, the reg-id is 2, and the Route header than the Call-ID has changed, the reg-id is 2, and the Route header
goes through EP2. goes through EP2.
Message #13 Message #13
REGISTER sip:example.com SIP/2.0 REGISTER sip:example.com SIP/2.0
Via: SIP/2.0/TCP 192.168.1.2;branch=z9hG4bKnqr9bym Via: SIP/2.0/TCP 192.0.2.2;branch=z9hG4bKnqr9bym
Max-Forwards: 70 Max-Forwards: 70
From: Bob <sip:bob@example.com>;tag=755285EABDE2 From: Bob <sip:bob@example.com>;tag=755285EABDE2
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Call-ID: E05133BD26DD Call-ID: E05133BD26DD
CSeq: 1 REGISTER CSeq: 1 REGISTER
Supported: path, outbound Supported: path, outbound
Route: <sip:ep2.example.com;lr> Route: <sip:ep2.example.com;lr>
Contact: <sip:bob@192.168.1.2;transport=tcp>;reg-id=2 Contact: <sip:bob@192.0.2.2;transport=tcp>;reg-id=2
;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>" ;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>"
Content-Length: 0 Content-Length: 0
Likewise in message #14, EP2 adds a Path header with flow token and Likewise in message #14, EP2 adds a Path header with flow token and
'ob' parameter. 'ob' parameter.
Path: <sip:wazHDLdIMtUg6r0I/oRZ15zx3zHE1w1Z@ep2.example.com;lr;ob> Path: <sip:wazHDLdIMtUg6r0I/oRZ15zx3zHE1w1Z@ep2.example.com;lr;ob>
Message #16 tells Bob's UA that outbound registration was successful, Message #16 tells Bob's UA that outbound registration was successful,
and shows both Contacts. Note that only the Path corresponding to and shows both Contacts. Note that only the Path corresponding to
the current registration is returned. the current registration is returned.
Message #16 Message #16
SIP/2.0 200 OK SIP/2.0 200 OK
Via: SIP/2.0/TCP 192.168.1.2;branch=z9hG4bKnqr9bym Via: SIP/2.0/TCP 192.0.2.2;branch=z9hG4bKnqr9bym
From: Bob <sip:bob@example.com>;tag=755285EABDE2 From: Bob <sip:bob@example.com>;tag=755285EABDE2
To: Bob <sip:bob@example.com>;tag=49A9AD0B3F6A To: Bob <sip:bob@example.com>;tag=49A9AD0B3F6A
Call-ID: E05133BD26DD Call-ID: E05133BD26DD
Supported: path, outbound Supported: path, outbound
Require: outbound Require: outbound
CSeq: 1 REGISTER CSeq: 1 REGISTER
Contact: <sip:bob@192.168.1.2;transport=tcp>;reg-id=1;expires=3600 Contact: <sip:bob@192.0.2.2;transport=tcp>;reg-id=1;expires=3600
;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>" ;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>"
Contact: <sip:bob@192.168.1.2;transport=tcp>;reg-id=2;expires=3600 Contact: <sip:bob@192.0.2.2;transport=tcp>;reg-id=2;expires=3600
;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>" ;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>"
Path: <sip:wazHDLdIMtUg6r0I/oRZ15zx3zHE1w1Z@ep2.example.com;lr;ob> Path: <sip:wazHDLdIMtUg6r0I/oRZ15zx3zHE1w1Z@ep2.example.com;lr;ob>
Content-Length: 0 Content-Length: 0
9.3. Incoming call and proxy crash 9.3. Incoming call and proxy crash
In this example, after registration, EP1 crashes and reboots. Before In this example, after registration, EP1 crashes and reboots. Before
Bob's UA notices that its flow to EP1 is no longer responding, Alice Bob's UA notices that its flow to EP1 is no longer responding, Alice
calls Bob. Bob's authoritative proxy first tries the flow to EP1, but calls Bob. Bob's authoritative proxy first tries the flow to EP1, but
EP1 no longer has a flow to Bob so it responds with a 430 Flow Failed EP1 no longer has a flow to Bob so it responds with a 430 Flow Failed
skipping to change at page 34, line 19 skipping to change at page 34, line 19
Call-ID: klmvCxVWGp6MxJp2T2mb Call-ID: klmvCxVWGp6MxJp2T2mb
CSeq: 1 INVITE CSeq: 1 INVITE
Bob's proxy rewrites the Request-URI to the Contact URI used in Bob's Bob's proxy rewrites the Request-URI to the Contact URI used in Bob's
registration, and places the path for one of the registrations registration, and places the path for one of the registrations
towards Bob's UA instance into a Route header field. This Route goes towards Bob's UA instance into a Route header field. This Route goes
through EP1. through EP1.
Message #22 Message #22
INVITE sip:bob@192.168.1.2;transport=tcp SIP/2.0 INVITE sip:bob@192.0.2.2;transport=tcp SIP/2.0
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
From: Alice <sip:alice@a.example>;tag=02935 From: Alice <sip:alice@a.example>;tag=02935
Call-ID: klmvCxVWGp6MxJp2T2mb Call-ID: klmvCxVWGp6MxJp2T2mb
CSeq: 1 INVITE CSeq: 1 INVITE
Route: <sip:VskztcQ/S8p4WPbOnHbuyh5iJvJIW3ib@ep1.example.com;lr;ob> Route: <sip:VskztcQ/S8p4WPbOnHbuyh5iJvJIW3ib@ep1.example.com;lr;ob>
Since EP1 just rebooted, it does not have the flow described in the Since EP1 just rebooted, it does not have the flow described in the
flow token. It returns a 430 Flow Failed response. flow token. It returns a 430 Flow Failed response.
Message #23 Message #23
skipping to change at page 34, line 42 skipping to change at page 34, line 42
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
From: Alice <sip:alice@a.example>;tag=02935 From: Alice <sip:alice@a.example>;tag=02935
Call-ID: klmvCxVWGp6MxJp2T2mb Call-ID: klmvCxVWGp6MxJp2T2mb
CSeq: 1 INVITE CSeq: 1 INVITE
The proxy deletes the binding for this path and tries to forward the The proxy deletes the binding for this path and tries to forward the
INVITE again, this time with the path through EP2. INVITE again, this time with the path through EP2.
Message #24 Message #24
INVITE sip:bob@192.168.1.2;transport=tcp SIP/2.0 INVITE sip:bob@192.0.2.2;transport=tcp SIP/2.0
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
From: Alice <sip:alice@a.example>;tag=02935 From: Alice <sip:alice@a.example>;tag=02935
Call-ID: klmvCxVWGp6MxJp2T2mb Call-ID: klmvCxVWGp6MxJp2T2mb
CSeq: 1 INVITE CSeq: 1 INVITE
Route: <sip:wazHDLdIMtUg6r0I/oRZ15zx3zHE1w1Z@ep2.example.com;lr;ob> Route: <sip:wazHDLdIMtUg6r0I/oRZ15zx3zHE1w1Z@ep2.example.com;lr;ob>
In message #25, EP2 needs to add a Record-Route header field value, In message #25, EP2 needs to add a Record-Route header field value,
so that any subsequent in-dialog messages from Alice's UA arrive at so that any subsequent in-dialog messages from Alice's UA arrive at
Bob's UA. EP2 can determine it needs to Record-Route since the Bob's UA. EP2 can determine it needs to Record-Route since the
request is a dialog-forming request and the Route header contained a request is a dialog-forming request and the Route header contained a
flow token and an 'ob' parameter. This Record-Route information is flow token and an 'ob' parameter. This Record-Route information is
passed back to Alice's UA in the responses (messages #26, 27, and 28) passed back to Alice's UA in the responses (messages #26, 27, and 28)
Message #25 Message #25
INVITE sip:bob@192.168.1.2;transport=tcp SIP/2.0 INVITE sip:bob@192.0.2.2;transport=tcp SIP/2.0
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
From: Alice <sip:alice@a.example>;tag=02935 From: Alice <sip:alice@a.example>;tag=02935
Call-ID: klmvCxVWGp6MxJp2T2mb Call-ID: klmvCxVWGp6MxJp2T2mb
CSeq: 1 INVITE CSeq: 1 INVITE
Record-Route: Record-Route:
<sip:wazHDLdIMtUg6r0I/oRZ15zx3zHE1w1Z@ep2.example.com;lr> <sip:wazHDLdIMtUg6r0I/oRZ15zx3zHE1w1Z@ep2.example.com;lr>
Message #26 Message #26
SIP/2.0 200 OK SIP/2.0 200 OK
skipping to change at page 35, line 36 skipping to change at page 35, line 36
<sip:wazHDLdIMtUg6r0I/oRZ15zx3zHE1w1Z@ep2.example.com;lr> <sip:wazHDLdIMtUg6r0I/oRZ15zx3zHE1w1Z@ep2.example.com;lr>
At this point, both UAs have the correct route-set for the dialog. At this point, both UAs have the correct route-set for the dialog.
Any subsequent requests in this dialog will route correctly. For Any subsequent requests in this dialog will route correctly. For
example, the ACK request in message #29 is sent form Alice's UA example, the ACK request in message #29 is sent form Alice's UA
directly to EP2. The BYE request in message #31 uses the same route- directly to EP2. The BYE request in message #31 uses the same route-
set. set.
Message #29 Message #29
ACK sip:bob@192.168.1.2;transport=tcp SIP/2.0 ACK sip:bob@192.0.2.2;transport=tcp SIP/2.0
To: Bob <sip:bob@example.com>;tag=skduk2 To: Bob <sip:bob@example.com>;tag=skduk2
From: Alice <sip:alice@a.example>;tag=02935 From: Alice <sip:alice@a.example>;tag=02935
Call-ID: klmvCxVWGp6MxJp2T2mb Call-ID: klmvCxVWGp6MxJp2T2mb
CSeq: 1 ACK CSeq: 1 ACK
Route: <sip:wazHDLdIMtUg6r0I/oRZ15zx3zHE1w1Z@ep2.example.com;lr> Route: <sip:wazHDLdIMtUg6r0I/oRZ15zx3zHE1w1Z@ep2.example.com;lr>
Message #31 Message #31
BYE sip:bob@192.168.1.2;transport=tcp SIP/2.0 BYE sip:bob@192.0.2.2;transport=tcp SIP/2.0
To: Bob <sip:bob@example.com>;tag=skduk2 To: Bob <sip:bob@example.com>;tag=skduk2
From: Alice <sip:alice@a.example>;tag=02935 From: Alice <sip:alice@a.example>;tag=02935
Call-ID: klmvCxVWGp6MxJp2T2mb Call-ID: klmvCxVWGp6MxJp2T2mb
CSeq: 2 BYE CSeq: 2 BYE
Route: <sip:wazHDLdIMtUg6r0I/oRZ15zx3zHE1w1Z@ep2.example.com;lr> Route: <sip:wazHDLdIMtUg6r0I/oRZ15zx3zHE1w1Z@ep2.example.com;lr>
9.4. Re-registration 9.4. Re-registration
Somewhat later, Bob's UA sends keepalives to both its edge proxies, Somewhat later, Bob's UA sends keepalives to both its edge proxies,
but it discovers that the flow with EP1 failed. Bob's UA re- but it discovers that the flow with EP1 failed. Bob's UA re-
skipping to change at page 36, line 33 skipping to change at page 36, line 33
Message #38 Message #38
REGISTER sip:example.com SIP/2.0 REGISTER sip:example.com SIP/2.0
From: Bob <sip:bob@example.com>;tag=7F94778B653B From: Bob <sip:bob@example.com>;tag=7F94778B653B
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Call-ID: 16CB75F21C70 Call-ID: 16CB75F21C70
CSeq: 2 REGISTER CSeq: 2 REGISTER
Supported: path, outbound Supported: path, outbound
Route: <sip:ep1.example.com;lr> Route: <sip:ep1.example.com;lr>
Contact: <sip:bob@192.168.1.2;transport=tcp>;reg-id=1 Contact: <sip:bob@192.0.2.2;transport=tcp>;reg-id=1
;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>" ;+sip.instance="<urn:uuid:00000000-0000-1000-8000-AABBCCDDEEFF>"
In message #39, EP1 inserts a Path header with a new flow token: In message #39, EP1 inserts a Path header with a new flow token:
Path: <sip:3yJEbr1GYZK9cPYk5Snocez6DzO7w+AX@ep1.example.com;lr;ob> Path: <sip:3yJEbr1GYZK9cPYk5Snocez6DzO7w+AX@ep1.example.com;lr;ob>
9.5. Outgoing call 9.5. Outgoing call
Finally, Bob makes an outgoing call to Alice. Bob's UA includes an Finally, Bob makes an outgoing call to Alice. Bob's UA includes an
'ob' parameter in its Contact URI in message #42. EP1 adds a Record- 'ob' parameter in its Contact URI in message #42. EP1 adds a Record-
skipping to change at page 37, line 30 skipping to change at page 37, line 30
| | | | | | | | | |
Message #42 Message #42
INVITE sip:alice@a.example SIP/2.0 INVITE sip:alice@a.example SIP/2.0
From: Bob <sip:bob@example.com>;tag=ldw22z From: Bob <sip:bob@example.com>;tag=ldw22z
To: Alice <sip:alice@a.example> To: Alice <sip:alice@a.example>
Call-ID: 95KGsk2V/Eis9LcpBYy3 Call-ID: 95KGsk2V/Eis9LcpBYy3
CSeq: 1 INVITE CSeq: 1 INVITE
Route: <sip:ep1.example.com;lr> Route: <sip:ep1.example.com;lr>
Contact: <sip:bob@192.168.1.2;transport=tcp;ob> Contact: <sip:bob@192.0.2.2;transport=tcp;ob>
In message #43, EP1 adds the following Record-Route header. In message #43, EP1 adds the following Record-Route header.
Record-Route: Record-Route:
<sip:3yJEbr1GYZK9cPYk5Snocez6DzO7w+AX@ep1.example.com;lr> <sip:3yJEbr1GYZK9cPYk5Snocez6DzO7w+AX@ep1.example.com;lr>
When EP1 receives the BYE (message #50) from Bob's UA, it can tell When EP1 receives the BYE (message #50) from Bob's UA, it can tell
that the request is an "outgoing" request (since the source of the that the request is an "outgoing" request (since the source of the
request matches the flow in the flow token) and simply deletes its request matches the flow in the flow token) and simply deletes its
Route header field value and forwards the request on to Alice's UA. Route header field value and forwards the request on to Alice's UA.
Message #50 Message #50
BYE sip:alice@a.example SIP/2.0 BYE sip:alice@a.example SIP/2.0
From: Bob <sip:bob@example.com>;tag=ldw22z From: Bob <sip:bob@example.com>;tag=ldw22z
To: Alice <sip:alice@a.example>;tag=plqus8 To: Alice <sip:alice@a.example>;tag=plqus8
Call-ID: 95KGsk2V/Eis9LcpBYy3 Call-ID: 95KGsk2V/Eis9LcpBYy3
CSeq: 2 BYE CSeq: 2 BYE
Route: <sip:3yJEbr1GYZK9cPYk5Snocez6DzO7w+AX@ep1.example.com;lr> Route: <sip:3yJEbr1GYZK9cPYk5Snocez6DzO7w+AX@ep1.example.com;lr>
Contact: <sip:bob@192.168.1.2;transport=tcp;ob> Contact: <sip:bob@192.0.2.2;transport=tcp;ob>
10. Grammar 10. Grammar
This specification defines a new header field, new Contact header This specification defines a new header field, new Contact header
field parameters, reg-id and +sip.instance. The grammar includes the field parameters, reg-id and +sip.instance. The grammar includes the
definitions from RFC 3261 [RFC3261] and includes the definition of definitions from RFC 3261 [RFC3261] and includes the definition of
uric from RFC 3986 [RFC3986]. uric from RFC 3986 [RFC3986].
Note: The "=/" syntax used in this ABNF indicates an extension of Note: The "=/" syntax used in this ABNF indicates an extension of
the production on the left hand side. the production on the left hand side.
skipping to change at page 38, line 39 skipping to change at page 38, line 39
The value of the reg-id MUST NOT be 0 and MUST be less than 2**31. The value of the reg-id MUST NOT be 0 and MUST be less than 2**31.
11. IANA Considerations 11. IANA Considerations
11.1. Flow-Timer Header Field 11.1. Flow-Timer Header Field
This specification defines a new SIP header field "Flow-Timer" whose This specification defines a new SIP header field "Flow-Timer" whose
syntax is defined in Section 10. syntax is defined in Section 10.
RFC Number: RFC XXXX Header Name compact Reference
----------------- ------- ---------
Header Field Name: Flow-Timer Flow-Timer [RFCXXXX]
Compact Form: none
[NOTE TO RFC Editor: Please replace AAAA with [NOTE TO RFC Editor: Please replace XXXX with
the RFC number of this specification.] the RFC number of this specification.]
11.2. 'reg-id' Contact Header Field Parameter 11.2. 'reg-id' Contact Header Field Parameter
This specification defines a new Contact header field parameter This specification defines a new Contact header field parameter
called reg-id in the "Header Field Parameters and Parameter Values" called reg-id in the "Header Field Parameters and Parameter Values"
sub-registry as per the registry created by [RFC3968]. The syntax is sub-registry as per the registry created by [RFC3968]. The syntax is
defined in Section 10. The required information is: defined in Section 10. The required information is:
Header Field Parameter Name Predefined Reference Predefined
Values Header Field Parameter Name Values Reference
____________________________________________________________________ ---------------------- --------------------- ---------- ---------
Contact reg-id No [RFC AAAA] Contact reg-id No [RFCXXXX]
[NOTE TO RFC Editor: Please replace AAAA with [NOTE TO RFC Editor: Please replace XXXX with
the RFC number of this specification.] the RFC number of this specification.]
11.3. SIP/SIPS URI Parameters 11.3. SIP/SIPS URI Parameters
This specification augments the "SIP/SIPS URI Parameters" sub- This specification augments the "SIP/SIPS URI Parameters" sub-
registry as per the registry created by [RFC3969]. The required registry as per the registry created by [RFC3969]. The required
information is: information is:
Parameter Name Predefined Values Reference Parameter Name Predefined Values Reference
____________________________________________ -------------- ----------------- ---------
ob No [RFC AAAA] ob No [RFCXXXX]
[NOTE TO RFC Editor: Please replace AAAA with [NOTE TO RFC Editor: Please replace XXXX with
the RFC number of this specification.] the RFC number of this specification.]
11.4. SIP Option Tag 11.4. SIP Option Tag
This specification registers a new SIP option tag, as per the This specification registers a new SIP option tag, as per the
guidelines in Section 27.1 of RFC 3261. guidelines in Section 27.1 of RFC 3261.
Name: outbound Name: outbound
Description: This option-tag is used to identify UAs and Registrars Description: This option-tag is used to identify UAs and Registrars
which support extensions for Client Initiated Connections. A UA which support extensions for Client Initiated Connections. A UA
skipping to change at page 40, line 9 skipping to change at page 40, line 4
This document registers a new SIP response code (430 Flow Failed), as This document registers a new SIP response code (430 Flow Failed), as
per the guidelines in Section 27.4 of [RFC3261]. This response code per the guidelines in Section 27.4 of [RFC3261]. This response code
is used by an Edge Proxy to indicate to the Authoritative Proxy that is used by an Edge Proxy to indicate to the Authoritative Proxy that
a specific flow to a UA instance has failed. Other flows to the same a specific flow to a UA instance has failed. Other flows to the same
instance could still succeed. The Authoritative Proxy SHOULD attempt instance could still succeed. The Authoritative Proxy SHOULD attempt
to forward to another target (flow) with the same instance-id and to forward to another target (flow) with the same instance-id and
AOR. This response code is defined by the following information, AOR. This response code is defined by the following information,
which has been added to the method and response-code sub-registry which has been added to the method and response-code sub-registry
under http://www.iana.org/assignments/sip-parameters. under http://www.iana.org/assignments/sip-parameters.
Response Code Number: 430
Default Reason Phrase: Flow Failed Response Code Reference
------------------------------------------ ---------
Request Failure 4xx
430 Flow Failed [RFCXXXX]
[NOTE TO RFC Editor: Please replace XXXX with
the RFC number of this specification.]
11.6. 439 (First Hop Lacks Outbound Support) Response Code 11.6. 439 (First Hop Lacks Outbound Support) Response Code
This document registers a new SIP response code (439 First Hop Lacks This document registers a new SIP response code (439 First Hop Lacks
Outbound Support), as per the guidelines in Section 27.4 of Outbound Support), as per the guidelines in Section 27.4 of
[RFC3261]. This response code is used by a registrar to indicate [RFC3261]. This response code is used by a registrar to indicate
that it supports the 'outbound' feature described in this that it supports the 'outbound' feature described in this
specifcation, but that the first outbound proxy that the user is specification, but that the first outbound proxy that the user is
attempting to register through does not. Note that this response attempting to register through does not. Note that this response
code is only appropriate in the case that the registering user agent code is only appropriate in the case that the registering user agent
advertises support for outbound processing by including the advertises support for outbound processing by including the outbound
'outbound' option tag in a 'Supported' header field. Proxies MUST option tag in a Supported header field. Proxies MUST NOT send a 439
NOT send a 439 response to any requests that do not contain a response to any requests that do not contain a reg-id parameter and
'reg-id' parameter and an 'outbound' option tag in a 'Supported' an outbound option tag in a Supported header field. This response
header field. This response code is defined by the following code is defined by the following information, which has been added to
information, which has been added to the method and response-code the method and response-code sub-registry under
sub-registry under http://www.iana.org/assignments/sip-parameters. http://www.iana.org/assignments/sip-parameters.
Response Code Number: 439
Default Reason Phrase: First Hop Lacks Outbound Support Response Code Reference
------------------------------------------ ---------
Request Failure 4xx
439 First Hop Lacks Outbound Support [RFCXXXX]
[NOTE TO RFC Editor: Please replace XXXX with
the RFC number of this specification.]
11.7. Media Feature Tag 11.7. Media Feature Tag
This section registers a new media feature tag, per the procedures This section registers a new media feature tag, per the procedures
defined in [RFC2506]. The tag is placed into the sip tree, which is defined in [RFC2506]. The tag is placed into the sip tree, which is
defined in [RFC3840]. defined in [RFC3840].
Media feature tag name: sip.instance Media feature tag name: sip.instance
ASN.1 Identifier: New assignment by IANA. ASN.1 Identifier: New assignment by IANA.
skipping to change at page 41, line 9 skipping to change at page 41, line 14
The feature tag is intended primarily for use in the following The feature tag is intended primarily for use in the following
applications, protocols, services, or negotiation mechanisms: This applications, protocols, services, or negotiation mechanisms: This
feature tag is most useful in a communications application, for feature tag is most useful in a communications application, for
describing the capabilities of a device, such as a phone or PDA. describing the capabilities of a device, such as a phone or PDA.
Examples of typical use: Routing a call to a specific device. Examples of typical use: Routing a call to a specific device.
Related standards or documents: RFC XXXX Related standards or documents: RFC XXXX
[[Note to IANA: Please replace XXXX with the RFC number of this [Note to IANA: Please replace XXXX with the RFC number of this
specification.]] specification.]
Security Considerations: This media feature tag can be used in ways Security Considerations: This media feature tag can be used in ways
which affect application behaviors. For example, the SIP caller which affect application behaviors. For example, the SIP caller
preferences extension [RFC3841] allows for call routing decisions to preferences extension [RFC3841] allows for call routing decisions to
be based on the values of these parameters. Therefore, if an be based on the values of these parameters. Therefore, if an
attacker can modify the values of this tag, they might be able to attacker can modify the values of this tag, they might be able to
affect the behavior of applications. As a result, applications which affect the behavior of applications. As a result, applications which
utilize this media feature tag SHOULD provide a means for ensuring utilize this media feature tag SHOULD provide a means for ensuring
its integrity. Similarly, this feature tag should only be trusted as its integrity. Similarly, this feature tag should only be trusted as
valid when it comes from the user or user agent described by the tag. valid when it comes from the user or user agent described by the tag.
skipping to change at page 43, line 18 skipping to change at page 43, line 22
1. Must be able to detect that a UA supports these mechanisms. 1. Must be able to detect that a UA supports these mechanisms.
2. Support UAs behind NATs. 2. Support UAs behind NATs.
3. Support TLS to a UA without a stable DNS name or IP address. 3. Support TLS to a UA without a stable DNS name or IP address.
4. Detect failure of a connection and be able to correct for this. 4. Detect failure of a connection and be able to correct for this.
5. Support many UAs simultaneously rebooting. 5. Support many UAs simultaneously rebooting.
6. Support a NAT rebooting or resetting. 6. Support a NAT rebooting or resetting.
7. Minimize initial startup load on a proxy. 7. Minimize initial startup load on a proxy.
8. Support architectures with edge proxies. 8. Support architectures with edge proxies.
15. Changes 15. Acknowledgments
Note to RFC Editor: Please remove this whole section.
15.1. Changes from 12 Version
Lots of editorials comments. Allows for sending keep-alive based on
presence of ob parameter and/or through explicit configuration.
Clarified treatment of recoverable error responses to REGISTER
regarding keeping flows active.
15.2. Changes from 11 Version
Added 439 response code to handle "Require: outbound" with first
outbound proxy that doesn't insert ";ob".
15.3. Changes from 09 Version
Make outbound consistent with the latest version of STUN 3489bis
draft. The STUN keepalive section of outbound is now a STUN usage
(much less formal).
Fixed references.
15.4. Changes from 08 Version
UAs now include the 'ob' parameter in their Contact header for non-
REGISTER requests, as a hint to the Edge Proxy (so the EP can Record-
Route with a flow-token for example).
Switched to CRLF for keepalives of connection-oriented transports
after brutal consensus at IETF 68.
Added timed-keepalive parameter and removed the unnecessary keep-tcp
param, per consensus at IETF68.
Removed example "Algorithm 1" which only worked over SIPS, per
consensus at IETF68.
Deleted text about probing and validating with options, per consensus
at IETF68.
Deleted provision for waiting 120 secs before declaring flow stable,
per consensus at IETF68.
fixed example UUIDs
15.5. Changes from 07 Version
Add language to show the working group what adding CRLF keepalives
would look like.
Changed syntax of keep-alive=stun to keep-stun so that it was easier
to support multiple tags in the same URI.
15.6. Changes from 06 Version
Added the section on operational selection of transports.
Fixed various editorial typos.
Put back in requirement flow token needs to be unique to flow as it
had accidentally been dropped in earlier version. This did not
change any of the flow token algorithms.
Reordered some of the text on STUN keepalive validation to make it
clearer to implementors. Did not change the actual algorithm or
requirements. Added note to explain how if the proxy changes, the
revalidation will happen.
15.7. Changes from 05 Version
Mention the relevance of the 'rport' parameter.
Change registrar verification so that only first-hop proxy and the
registrar need to support outbound. Other intermediaries in between
do not any more.
Relaxed flow-token language slightly. Instead of flow-token saving
specific UDP address/port tuples over which the request arrived, make
language fuzzy to save token which points to a 'logical flow' that is
known to deliver data to that specific UA instance.
Added comment that keep-stun could be added to Path.
Added comment that battery concerns could motivate longer TCP
keepalive intervals than the defaults.
Scrubbed document for avoidable lowercase may, should, and must.
Added text about how Edge Proxies could determine they are the first
hop.
15.8. Changes from 04 Version
Moved STUN to a separate section. Reference this section from within
the relevant sections in the rest of the document.
Add language clarifying that UA MUST NOT send STUN without an
explicit indication the server supports STUN.
Add language describing that UA MUST stop sending STUN if it appears
the server does not support it.
Defined a 'sip-stun' option tag. UAs can optionally probe servers
for it with OPTIONS. Clarified that UAs SHOULD NOT put this in a
Proxy-Require. Explain that the first-hop MUST support this option-
tag.
Clarify that SIP/STUN in TLS is on the "inside". STUN used with
Sigcomp-compressed SIP is "outside" the compression layer for UDP,
but wrapped inside the well-known shim header for TCP-based
transports.
Clarify how to decide what a consecutive registration timer is. Flow
must be up for some time (default 120 seconds) otherwise previous
registration is not considered successful.
Change UAC MUST-->SHOULD register a flow for each member of outbound-
proxy-set.
Reworded registrar and proxy in some places (introduce the term
"Authoritative Proxy").
Loosened restrictions on always storing a complete Path vector back
to the registrar/authoritative proxy if a previous hop in the path
vector is reachable.
Added comment about re-registration typically happening over same
flow as original registration.
Changed 410 Gone to new response code 430 Flow Failed. Was going to
change this to 480 Temporarily Unavailable. Unfortunately this would
mean that the authoritative proxy deletes all flows of phones who use
480 for Do Not Disturb. Oops!
Restored sanity by restoring text which explains that registrations
with the same reg-id replace the old registration.
Added text about the 'ob' parameter which is used in Path header
field URIs to make sure that the previous proxy that added a Path
understood outbound processing. The registrar doesn't include
Supported: outbound unless it could actually do outbound processing
(ex: any Path headers have to have the 'ob' parameter).
Added some text describing what a registration means when there is an
instance-id, but no reg-id.
15.9. Changes from 03 Version
Added non-normative text motivating STUN vs. SIP PING, OPTIONS, and
Double CRLF. Added discussion about why TCP Keepalives are not
always available.
Explained more clearly that outbound-proxy-set can be "configured"
using any current or future, manual or automatic configuration/
discovery mechanism.
Added a sentence which prevents an Edge Proxy from forwarding back
over the flow over which the request is received if the request
happens to contain a flow token for that flow. This was an
oversight.
Updated example message flow to show a fail-over example using a new
dialog-creating request instead of a mid-dialog request. The old
scenario was leftover from before the outbound / gruu reorganization.
Fixed tags, Call-IDs, and branch parameters in the example messages.
Made the ABNF use the "=/" production extension mechanism recommended
by Bill Fenner.
Added a table in an appendix expanding the default flow recovery
timers.
Incorporated numerous clarifications and rewordings for better
comprehension.
Fixed many typos and spelling steaks.
15.10. Changes from 02 Version
Removed Double CRLF Keepalive
Changed ;sip-stun syntax to ;keepalive=stun
Fixed incorrect text about TCP keepalives.
15.11. Changes from 01 Version
Moved definition of instance-id from GRUU[I-D.ietf-sip-gruu] draft to
this draft.
Added tentative text about Double CRLF Keepalive
Removed pin-route stuff
Changed the name of "flow-id" to "reg-id"
Reorganized document flow
Described the use of STUN as a proper STUN usage
Added 'outbound' option-tag to detect if registrar supports outbound
15.12. Changes from 00 Version
Moved TCP keepalive to be STUN.
Allowed SUBSCRIBE to create flow mappings. Added pin-route option
tags to support this.
Added text about updating dialog state on each usage after a
connection failure.
16. Acknowledgments
Francois Audet acted as document shepherd for this draft, tracking Francois Audet acted as document shepherd for this draft, tracking
hundreds of comments and incorporating many grammatical fixes as well hundreds of comments and incorporating many grammatical fixes as well
as prodding the editors to "get on with it". Jonathan Rosenberg, as prodding the editors to "get on with it". Jonathan Rosenberg,
Erkki Koivusalo, and Byron Campben provided many comments and useful Erkki Koivusalo, and Byron Campen provided many comments and useful
text. Dave Oran came up with the idea of using the most recent text. Dave Oran came up with the idea of using the most recent
registration first in the proxy. Alan Hawrylyshen co-authored the registration first in the proxy. Alan Hawrylyshen co-authored the
draft that formed the initial text of this specification. draft that formed the initial text of this specification.
Additionally, many of the concepts here originated at a connection Additionally, many of the concepts here originated at a connection
reuse meeting at IETF 60 that included the authors, Jon Peterson, reuse meeting at IETF 60 that included the authors, Jon Peterson,
Jonathan Rosenberg, Alan Hawrylyshen, and Paul Kyzivat. The TCP Jonathan Rosenberg, Alan Hawrylyshen, and Paul Kyzivat. The TCP
design team consisting of Chris Boulton, Scott Lawrence, Rajnish design team consisting of Chris Boulton, Scott Lawrence, Rajnish
Jain, Vijay K. Gurbani, and Ganesh Jayadevan provided input and text. Jain, Vijay K. Gurbani, and Ganesh Jayadevan provided input and text.
Nils Ohlmeier provided many fixes and initial implementation Nils Ohlmeier provided many fixes and initial implementation
experience. In addition, thanks to the following folks for useful experience. In addition, thanks to the following folks for useful
comments: Francois Audet, Flemming Andreasen, Mike Hammer, Dan Wing, comments: Francois Audet, Flemming Andreasen, Mike Hammer, Dan Wing,
Srivatsa Srinivasan, Dale Worely, Juha Heinanen, Eric Rescorla, Srivatsa Srinivasan, Dale Worely, Juha Heinanen, Eric Rescorla,
Lyndsay Campbell, Christer Holmberg, Kevin Johns, Jeroen van Bemmel, Lyndsay Campbell, Christer Holmberg, Kevin Johns, Jeroen van Bemmel,
Derek MacDonald and Dean Willis. Derek MacDonald and Dean Willis.
17. References 16. References
17.1. Normative References 16.1. Normative References
[I-D.ietf-behave-rfc3489bis] [I-D.ietf-behave-rfc3489bis]
Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for (NAT) (STUN)", "Session Traversal Utilities for (NAT) (STUN)",
draft-ietf-behave-rfc3489bis-15 (work in progress), draft-ietf-behave-rfc3489bis-15 (work in progress),
February 2008. February 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
skipping to change at page 49, line 38 skipping to change at page 45, line 22
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005. RFC 3986, January 2005.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122, Unique IDentifier (UUID) URN Namespace", RFC 4122,
July 2005. July 2005.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
17.2. Informational References 16.2. Informational References
[I-D.ietf-sip-gruu] [I-D.ietf-sip-gruu]
Rosenberg, J., "Obtaining and Using Globally Routable User Rosenberg, J., "Obtaining and Using Globally Routable User
Agent (UA) URIs (GRUU) in the Session Initiation Protocol Agent (UA) URIs (GRUU) in the Session Initiation Protocol
(SIP)", draft-ietf-sip-gruu-15 (work in progress), (SIP)", draft-ietf-sip-gruu-15 (work in progress),
October 2007. October 2007.
[I-D.ietf-sipping-config-framework] [I-D.ietf-sipping-config-framework]
Channabasappa, S., "A Framework for Session Initiation Channabasappa, S., "A Framework for Session Initiation
Protocol User Agent Profile Delivery", Protocol User Agent Profile Delivery",
skipping to change at page 51, line 5 skipping to change at page 46, line 31
Appendix A. Default Flow Registration Backoff Times Appendix A. Default Flow Registration Backoff Times
The base-time used for the flow re-registration backoff times The base-time used for the flow re-registration backoff times
described in Section 4.5 are configurable. If the base-time-all-fail described in Section 4.5 are configurable. If the base-time-all-fail
value is set to the default of 30 seconds and the base-time-not- value is set to the default of 30 seconds and the base-time-not-
failed value is set to the default of 90 seconds, the following table failed value is set to the default of 90 seconds, the following table
shows the resulting amount of time the UA will wait to retry shows the resulting amount of time the UA will wait to retry
registration. registration.
+-------------------+--------------------+--------------------+ +-------------------+--------------------+---------------------+
| # of reg failures | all flows unusable | >1 non-failed flow | | # of reg failures | all flows unusable | >1 non-failed flow |
+-------------------+--------------------+--------------------+ +-------------------+--------------------+---------------------+
| 0 | 0 secs | 0 secs | | 0 | 0 s | 0 s |
| 1 | 30-60 secs | 90-180 secs | | 1 | 30-60 s | 90-180 s |
| 2 | 1-2 mins | 3-6 mins | | 2 | 1-2 min | 3-6 min |
| 3 | 2-4 mins | 6-12 mins | | 3 | 2-4 min | 6-12 min |
| 4 | 4-8 mins | 12-24 mins | | 4 | 4-8 min | 12-24 min |
| 5 | 8-16 mins | 15-30 mins | | 5 | 8-16 min | 15-30 min |
| 6 or more | 15-30 mins | 15-30 mins | | 6 or more | 15-30 min | 15-30 min |
+-------------------+--------------------+--------------------+ +-------------------+--------------------+---------------------+
Authors' Addresses Authors' Addresses
Cullen Jennings (editor) Cullen Jennings (editor)
Cisco Systems Cisco Systems
170 West Tasman Drive 170 West Tasman Drive
Mailstop SJC-21/2 Mailstop SJC-21/2
San Jose, CA 95134 San Jose, CA 95134
USA USA
skipping to change at page 52, line 44 skipping to change at line 2186
attempt made to obtain a general license or permission for the use of attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at this standard. Please address the information to the IETF at
ietf-ipr@ietf.org. ietf-ipr@ietf.org.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
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