draft-ietf-mmusic-connection-precon-00.txt   draft-ietf-mmusic-connection-precon-01.txt 
MMUSIC Working Group G. Camarillo
SIPPING Working Group G. Camarillo
Internet-Draft Ericsson Internet-Draft Ericsson
Expires: March 19, 2005 September 18, 2004 Expires: June 2, 2005 December 2, 2004
Connection-Establishment Preconditions in the Session Initiation Connection-Establishment Preconditions in the Session Initiation
Protocol (SIP) Protocol (SIP)
draft-ietf-mmusic-connection-precon-00.txt draft-ietf-mmusic-connection-precon-01.txt
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2004).
Abstract Abstract
This document defines the connection-establishment precondition type This document defines the connection-establishment precondition type
for the SIP preconditions framework. Connection-establishment for the SIP preconditions framework. Connection-establishment
preconditions are met when a transport connection (e.g., a TCP preconditions are met when a transport connection (e.g., a TCP
connection) is successfully established between two endpoints. connection) is successfully established between two endpoints.
Table of Contents Table of Contents
skipping to change at page 3, line 8 skipping to change at page 3, line 8
8. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 8. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
9. Security Considerations . . . . . . . . . . . . . . . . . . . 6 9. Security Considerations . . . . . . . . . . . . . . . . . . . 6
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . 6 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . 6
11. Normative References . . . . . . . . . . . . . . . . . . . . 6 11. Normative References . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . 8 Intellectual Property and Copyright Statements . . . . . . . . 8
1. Introduction 1. Introduction
RFC 3312 [3] defines a framework for preconditions for SIP [2], RFC 3312 [3] defines a framework for preconditions for SIP [2],
which is updated by [4]. This document defines a new precondition which is updated by [5]. This document defines a new precondition
type for that framework: connection-establishment preconditions. type for that framework: connection-establishment preconditions.
UAs (User Agents) use connection-establishment preconditions when UAs (User Agents) use connection-establishment preconditions when
they need to know whether a transport connection (e.g., a TCP they need to know whether a transport connection (e.g., a TCP
connection) has been established successfully and is ready to carry connection) has been established successfully and is ready to carry
user data. user data.
We define the connection-establishment precondition type following We define the connection-establishment precondition type following
the guidelines provided in [4] to extend the SIP preconditions the guidelines provided in [5] to extend the SIP preconditions
framework. framework.
2. Terminology 2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED", In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
described in BCP 14, RFC 2119 [1] and indicate requirement levels for described in BCP 14, RFC 2119 [1] and indicate requirement levels for
compliant implementations. compliant implementations.
3. Precondition Tag 3. Precondition Tag
The precondition tag associated with the connection-establishment The precondition tag associated with the connection-establishment
preconditions is "conn". This precondition tag is registered with the preconditions is "conn". This precondition tag is registered with
IANA in Section 10. the IANA in Section 10.
4. Status Type 4. Status Type
RFC 3312 [3] defines two status types, end-to-end and segmented, but RFC 3312 [3] defines two status types, end-to-end and segmented, but
only the end-to-end status type applies to connection-establishment only the end-to-end status type applies to connection-establishment
preconditions. So, connection-establishment preconditions MUST use preconditions. So, connection-establishment preconditions MUST use
the end-to-end status type and MUST NOT use the segmented status the end-to-end status type and MUST NOT use the segmented status
type. type.
5. Direction Tag 5. Direction Tag
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6. Precondition Strength 6. Precondition Strength
RFC 3312 [3] defines optional and mandatory preconditions, but only RFC 3312 [3] defines optional and mandatory preconditions, but only
mandatory preconditions apply to connection-establishment mandatory preconditions apply to connection-establishment
preconditions. So, connection-establishment preconditions MUST NOT preconditions. So, connection-establishment preconditions MUST NOT
use optional preconditions. use optional preconditions.
7. Suspending and Resuming Session Establishment 7. Suspending and Resuming Session Establishment
According to [4], documents defining new precondition types need to According to [5], documents defining new precondition types need to
describe the behavior of UAs from the moment session establishment is describe the behavior of UAs from the moment session establishment is
suspended due to a set of preconditions until is resumed when these suspended due to a set of preconditions until is resumed when these
preconditions are met. preconditions are met.
While session establishment is suspended due to While session establishment is suspended due to
connection-establishment preconditions, user agents SHOULD not send connection-establishment preconditions, user agents SHOULD not send
any user data over any media stream. Additionally, the UAS (User any user data over the media streams affected by the preconditions.
Agent Server) SHOULD NOT alert the called user. Additionally, the UAS (User Agent Server) SHOULD NOT alert the called
user.
Offers with connection-establishment preconditions in re-INVITEs or Offers with connection-establishment preconditions in re-INVITEs or
UPDATEs follow the rules given in Section 6 of RFC 3312 [3]. UPDATEs follow the rules given in Section 6 of RFC 3312 [3].
Both user agents SHOULD continue using the old session parameters Both user agents SHOULD continue using the old session parameters
until all the mandatory preconditions are met. At that moment, until all the mandatory preconditions are met. At that moment,
the user agents can begin using the new session parameters. the user agents can begin using the new session parameters.
8. Example 8. Example
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| | | |
| | | |
| | | |
| | B's radio | | B's radio
|<---TCP Connection Establishment--->+ bearer is up |<---TCP Connection Establishment--->+ bearer is up
| | B sends TCP SYN | | B sends TCP SYN
| | | |
| | | |
| 180 Ringing | TCP connection | 180 Ringing | TCP connection
|<-----------------------------------+ is up |<-----------------------------------+ is up
| | B alerts the use | | B alerts the user
| | | |
Figure 1: Message flow with two types of preconditions Figure 1: Message flow with two types of preconditions
A sends an INVITE requesting connection-establishment preconditions. A sends an INVITE requesting connection-establishment preconditions.
The setup attribute in the offer is set to holdconn because A cannot The setup attribute in the offer is set to holdconn because A cannot
send or receive any data before setting up a radio bearer for the send or receive any data before setting up a radio bearer for the
connection. connection.
B agrees to use connection-establishment preconditions by sending a B agrees to use connection-establishment preconditions by sending a
183 (Session Progress) response. The setup attribute in the answer is 183 (Session Progress) response. The setup attribute in the answer
also set to holdconn because B, like A, cannot send or receive any is also set to holdconn because B, like A, cannot send or receive any
data before setting up a radio bearer for the connection. data before setting up a radio bearer for the connection.
When A's radio bearer is ready, A sends an UPDATE to B with a setup When A's radio bearer is ready, A sends an UPDATE to B with a setup
attribute with a value of actpass. This attribute indicates that A attribute with a value of actpass. This attribute indicates that A
can perform an active or a passive TCP open. A is letting B choose can perform an active or a passive TCP open. A is letting B choose
which endpoint will initiate the connection. which endpoint will initiate the connection.
Since B's radio bearer is not ready yet, B chooses to be the one Since B's radio bearer is not ready yet, B chooses to be the one
initiating the connection and indicates so with a setup attribute initiating the connection and indicates so with a setup attribute
with a value of active. At a later point, when B's radio bearer is with a value of active. At a later point, when B's radio bearer is
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callee and sends a 180 (Ringing) response. callee and sends a 180 (Ringing) response.
9. Security Considerations 9. Security Considerations
An attacker adding preconditions to a session description or An attacker adding preconditions to a session description or
modifying existing preconditions could keep sessions from being modifying existing preconditions could keep sessions from being
established. An attacker removing preconditions from a session established. An attacker removing preconditions from a session
description could force sessions to be established without meeting description could force sessions to be established without meeting
mandatory preconditions. mandatory preconditions.
It is thus STRONGLY RECOMMENDED that integrity protection be applied It is thus strongly RECOMMENDED that integrity protection be applied
to the SDP session descriptions. S/MIME is the natural choice to to the SDP session descriptions. S/MIME [4] is the natural choice to
provide such end-to-end integrity protection, as described in RFC provide such end-to-end integrity protection, as described in RFC
3261 [2]. 3261 [2].
10. IANA Considerations 10. IANA Considerations
This document defines a new precondition type: This document defines a new precondition type:
connection-establishment. It needs to be registered by the IANA connection-establishment. It needs to be registered by the IANA
under: under the registry for Precondition Types used with SIP.
http://www.iana.org/assignments/sip-precond-types
Pecondition-Type Description Reference Pecondition-Type Description Reference
---------------- ----------------------------------- --------- ---------------- ----------------------------------- ---------
conn Connection-establishment preconditions [RFCXXXX] conn Connection-establishment preconditions [RFCXXXX]
11 Normative References 11 Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[2] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., [2] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP: Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002. Session Initiation Protocol", RFC 3261, June 2002.
[3] Camarillo, G., Marshall, W. and J. Rosenberg, "Integration of [3] Camarillo, G., Marshall, W. and J. Rosenberg, "Integration of
Resource Management and Session Initiation Protocol (SIP)", RFC Resource Management and Session Initiation Protocol (SIP)", RFC
3312, October 2002. 3312, October 2002.
[4] Camarillo, G., "Interactions of Preconditions with Session [4] Peterson, J., "S/MIME Advanced Encryption Standard (AES)
Mobility in the Session Initiation Protocol (SIP)", Requirement for the Session Initiation Protocol (SIP)", RFC
draft-ietf-sip-rfc3312-update-00 (work in progress), November 3853, July 2004.
2003.
[5] Camarillo, G., "Update to the Session Initiation Protocol (SIP)
Preconditions Framework", draft-ietf-sip-rfc3312-update-03 (work
in progress), September 2004.
Author's Address Author's Address
Gonzalo Camarillo Gonzalo Camarillo
Ericsson Ericsson
Hirsalantie 11 Hirsalantie 11
Jorvas 02420 Jorvas 02420
Finland Finland
EMail: Gonzalo.Camarillo@ericsson.com EMail: Gonzalo.Camarillo@ericsson.com
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