[erlang-questions] SCTP support (was EPIPE and TCP sockets)
Sat Oct 13 11:45:18 CEST 2007
G Bulmer wrote:
> Newbie question.
>> Date: Fri, 12 Oct 2007 12:29:41 +1300
>> From: Bruce Fitzsimons <>
>> Subject: Re: [erlang-questions] EPIPE and TCP sockets
>> ... I'd still like to
>> use the SCTP support in Erlang to demonstrate XMPP over SCTP and see
>> what sort of improvements it might give, ...
> Is the "Erlang SCTP support" likely to give higher message
> throughput, or is this really about reliability guarantees? Is this
> OS sensitive, i.e. very much bound to the quality of SCTP
> implementation for the underlying OS?
Throughput is unlikely to be a benefit; considering we have many years
experience in TCP behaviour and tuning and not much at all with SCTP.
SCTP is a more complex protocol, but does avoid several TCP corner cases
including head of line blocking
Given that it is most used in friendly environments, I think we are
still to see what new DoS attacks SCTP could enable, but the TCP ones
are fixed and thought was given to preventing new ones.
I am most interested in SCTP to take advantage of the native connection
heart-beating, something commonly implemented in the application layer
but not present as standard in XMPP. With the "standard" TCP connection
timeout at 2 hours the TX buffer can be filling on the sending host
without the application being aware that they are not being delivered,
and there is no way to tell what quantity of data was reliably delivered
when the connection is finally terminated (Tony's problem). This
manifests in XMPP as messages being silently blackholed and presence
information that is way out of date. This only occurs when the recipient
disappears rather than terminates the TCP connection but this is fairly
common on the Internet. (I'm quite likely to be corrected here, in my
defense my Stevens is at work and the failure cases are subtle.) Most
XMPP implementations reduce the timeout length but this can never be a
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