SIPPING Working Group G. Camarillo
Internet-Draft Ericsson
Expires: January 6, 2005 July 8, 2004
Connection-Establishment Preconditions in the Session Initiation
Protocol (SIP)
draft-camarillo-mmusic-connection-precon-00.txt
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Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
This document defines the connection-establishment precondition type
for the SIP preconditions framework. Connection-establishment
preconditions are met when a transport connection (e.g., a TCP
connection) is successfully established between two endpoints.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Precondition Tag . . . . . . . . . . . . . . . . . . . . . . . 3
4. Status Type . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Direction Tag . . . . . . . . . . . . . . . . . . . . . . . . 3
6. Precondition Strength . . . . . . . . . . . . . . . . . . . . 4
7. Suspending and Resuming Session Establishment . . . . . . . . 4
8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
9. Security Considerations . . . . . . . . . . . . . . . . . . . 4
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
11.1 Normative References . . . . . . . . . . . . . . . . . . . . 5
11.2 Informational References . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 5
Intellectual Property and Copyright Statements . . . . . . . . 6
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1. Introduction
RFC 3312 [3] defines a framework for preconditions for SIP [2],
which is updated by [4]. This document defines a new precondition
type for that framework: connection-establishment preconditions.
UAs (User Agents) use connection-establishment preconditions when
they need to know whether a transport connection (e.g., a TCP
connection) has been established successfully and is ready to carry
user data.
We define the connection-establishment precondition type following
the guidelines provided in [4] to extend the SIP preconditions
framework.
2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
described in BCP 14, RFC 2119 [1] and indicate requirement levels for
compliant implementations.
3. Precondition Tag
The precondition tag associated with the connection-establishment
preconditions is "conn". This precondition tag is registered with the
IANA in Section 10.
4. Status Type
RFC 3312 [3] defines two status types, end-to-end and segmented, but
only the end-to-end status type applies to connection-establishment
preconditions. So, connection-establishment preconditions MUST use
the end-to-end status type and MUST NOT use the segmented status
type.
5. Direction Tag
RFC 3312 [3] defines four direction tags: none, send, recv, and
sendrecv. Once a transport connection is established, they indicate
in which directions the connection can carry user data. For example,
a successfully-established TCP connection would have an associated
direction tag of sendrecv because it can carry data in both
directions.
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6. Precondition Strength
RFC 3312 [3] defines optional and mandatory preconditions, but only
mandatory preconditions apply to connection-establishment
preconditions. So, connection-establishment preconditions MUST NOT
use optional preconditions.
7. Suspending and Resuming Session Establishment
According to [4], documents defining new precondition types need to
describe the behavior of UAs from the moment session establishment is
suspended due to a set of preconditions until is resumed when these
preconditions are met.
While session establishment is suspended due to
connection-establishment preconditions, user agents SHOULD not send
any user data over any media stream. Additionally, the UAS (User
Agent Server) SHOULD NOT alert the called user.
Offers with connection-establishment preconditions in re-INVITEs or
UPDATEs follow the rules given in Section 6 of RFC 3312 [3].
Both user agents SHOULD continue using the old session parameters
until all the mandatory preconditions are met. At that moment,
the user agents can begin using the new session parameters.
8. Examples
TBD
m=audio 20000 RTP/AVP 0
a=curr:conn e2e none
a=des:conn mandatory e2e sendrecv
9. Security Considerations
TBD.
10. IANA Considerations
TBD.
11. References
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11.1 Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
[3] Camarillo, G., Marshall, W. and J. Rosenberg, "Integration of
Resource Management and Session Initiation Protocol (SIP)", RFC
3312, October 2002.
[4] Camarillo, G., "Interactions of Preconditions with Session
Mobility in the Session Initiation Protocol (SIP)",
draft-ietf-sip-rfc3312-update-00 (work in progress), November
2003.
11.2 Informational References
Author's Address
Gonzalo Camarillo
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
EMail: Gonzalo.Camarillo@ericsson.com
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