[tcpm] RE: draft-moncaster-tcpm-rcv-cheat-02 probabilistic test

Alfred Hönes <ah@tr-sys.de> Fri, 16 November 2007 18:59 UTC

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From: Alfred =?hp-roman8?B?SM5uZXM=?= <ah@tr-sys.de>
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Subject: [tcpm] RE: draft-moncaster-tcpm-rcv-cheat-02 probabilistic test
To: jheffner@psc.edu, toby.moncaster@bt.com
Date: Fri, 16 Nov 2007 19:58:10 +0100 (MEZ)
References: <473B28E0.6040602@psc.edu>
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At Fri, 16 Nov 2007 10:51:27 -0000 , <toby.moncaster at bt.com>  wrote:

> * Those receivers that are seeking to conceal congestion losses must
> have decided they don't need the missing data. This suggests either
> they are streaming media off the sender or they are collaborating
> with the sender.  ...

That is exactly the scenario supported by the Space Communication
Transport Protocol (SCPS-TP) "BETS" extension to TCP, now shortly
discussed in Section 6.5.4 of draft-moncaster-tcpm-rcv-cheat-02:
The reciever does not need outdated data, and it announces this
(and supporting protocol behavior) by negotiating BETS via TCP
option #20; and thus, the sender is aware or the possibility of
receiving ACKs for data not arrived at the receiver, and can
suppress the test.

I suggest that particular applications interested in this "Real-Time
Streaming over TCP" should consider implementing enough parts of
SCPS-TP to support BETS to coordinate sender and receiver behavior
in a manner tailored to these specific requirements.
Partial implementation of SCPS-TP is facilitated by the fact that
most TCP extensions of SCPS-TP have to be negotiated per connection;
if you do not have implemented a feature, just don't negotiate it!

  Alfred.


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