Indication of Support for Keep-Alive
RFC 6223
Internet Engineering Task Force (IETF) C. Holmberg
Request for Comments: 6223 Ericsson
Category: Standards Track April 2011
ISSN: 2070-1721
Indication of Support for Keep-Alive
Abstract
This specification defines a new Session Initiation Protocol (SIP)
Via header field parameter, "keep", which allows adjacent SIP
entities to explicitly negotiate usage of the Network Address
Translation (NAT) keep-alive mechanisms defined in SIP Outbound, in
cases where SIP Outbound is not supported, cannot be applied, or
where usage of keep-alives is not implicitly negotiated as part of
the SIP Outbound negotiation.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6223.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Holmberg Standards Track [Page 1]
RFC 6223 Keep-Alive April 2011
Table of Contents
1. Introduction ....................................................2
1.1. Use-Case: Dialog from Non-Registered UAs ...................3
1.2. Use-Case: SIP Outbound Not Supported .......................3
1.3. Use-Case: SIP Dialog Initiated Outbound Flows ..............3
2. Conventions .....................................................3
3. Definitions .....................................................4
4. User Agent and Proxy Behavior ...................................4
4.1. General ....................................................4
4.2. Lifetime of Keep-Alives ....................................5
4.2.1. General .............................................5
4.2.2. Keep-Alives Associated with Registration ............5
4.2.3. Keep-Alives Associated with Dialog ..................6
4.3. Behavior of a SIP Entity Willing to Send Keep-Alives .......6
4.4. Behavior of a SIP Entity Willing to Receive Keep-Alives ....7
5. Keep-Alive Frequency ............................................8
6. Connection Reuse ................................................9
7. Examples ........................................................9
7.1. General ....................................................9
7.2. Keep-Alive Negotiation Associated with
Registration: UA-Proxy .....................................9
7.3. Keep-Alive Negotiation Associated with Dialog: UA-Proxy ...11
7.4. Keep-Alive Negotiation Associated with Dialog: UA-UA ......13
8. Grammar ........................................................15
8.1. General ...................................................15
8.2. ABNF ......................................................15
9. IANA Considerations ............................................15
9.1. "keep" Via Header Field Parameter .........................15
10. Security Considerations .......................................15
11. Acknowledgements ..............................................16
12. References ....................................................17
12.1. Normative References .....................................17
12.2. Informative References ...................................17
1. Introduction
Section 3.5 of SIP Outbound [RFC5626] defines two keep-alive
mechanisms. Even though the keep-alive mechanisms are separated from
the rest of the SIP Outbound mechanism, SIP Outbound does not define
a mechanism to explicitly negotiate usage of the keep-alive
mechanisms. In some cases, usage of keep-alives can be implicitly
negotiated as part of the SIP Outbound negotiation.
However, there are SIP Outbound use-cases where usage of keep-alives
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