[MMUSIC] RTSP 2.0: Section 18.20: Sequence numbering.
Elwyn Davies <elwynd@folly.org.uk> Wed, 09 October 2013 15:13 UTC
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From: Elwyn Davies <elwynd@folly.org.uk>
To: "mmusic (E-mail)" <mmusic@ietf.org>, Magnus Westerlund <magnus.westerlund@ericsson.com>
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Date: Wed, 09 Oct 2013 16:16:20 +0100
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Subject: [MMUSIC] RTSP 2.0: Section 18.20: Sequence numbering.
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In the proces of checking the changes from v34 to v37, I found that there have been some changes to the CSeq specification (Section 18.20) that seem a bit garbled. In para 1, it is stated: > For each new RTSP request an agent creates the CSeq value > MUST be incremented by one. Then later: > Agents receiving a request over a reliable transport with an in-order > delivery MUST ignore how the sequence value increments, i.e. it can > increment with other values than 1. and > Proxies that aggregate several client sessions on the same transport > will have to ensure that the requests sent towards a particular > server have a joint sequence number space. A proxy having one client > with concurrent sessions with two different servers using the same > client proxy connection can avoid rewriting on the proxy to server > connection. The first requirement is contradicted by the second and third stories. We also have: > It also enables detecting loss of a request > and await a retransmission prior to processing a sub-sequent request > when using unreliable transport. I understood that RTSP/2.0 is only specified to run over reliable transports, so this either requires some usage of the subjunctive mood or maybe deletion. However, having non-sequential CSeq values would indeed screw up any future usage of unreliable transport. I wonder if this can be handled by changing the increment requirement so that it applies to requests sent down a given server connection (or channel). Then if unreliable transports ever did come back, the sequencing would still work on a per source/destination address/port quadruple (or whatever), while giving unique (but not necessarily integer sequential) numbering on the multiplexed connections. Anyway, I think that this section needs another pass to sort out the inconsistencies. Regards, Elwyn
- [MMUSIC] RTSP 2.0: Section 18.20: Sequence number… Elwyn Davies
- Re: [MMUSIC] RTSP 2.0: Section 18.20: Sequence nu… Ross Finlayson
- Re: [MMUSIC] RTSP 2.0: Section 18.20: Sequence nu… Magnus Westerlund
- Re: [MMUSIC] RTSP 2.0: Section 18.20: Sequence nu… Magnus Westerlund
- Re: [MMUSIC] RTSP 2.0: Section 18.20: Sequence nu… Elwyn Davies
- Re: [MMUSIC] RTSP 2.0: Section 18.20: Sequence nu… Magnus Westerlund