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Re: [Sip] Impossible to use real persistent connection with sip

Mark Watson wrote:
I fail to see the problem.

Servers can close the connection whenever they like. pc=1 tells the server to keep the connection for longer. Longer than what ? Longer than it would have done otherwise ??

If the server closes the connection, it presumably had a good reason. Asking it nicely to ignore its own good reasons does not seem very useful to me.

Perhaps we should recommend that servers do not close connections without a good reason ? Should we recommend that they do not initiate connections without a good reason ? or that they should not reject connections without a good reason ? Why should we believe there are servers which will arbitrarily close connections for no reason, servers that are so stupid they need a new parameter to tell them not to do this ?
Mark:

I don't think anyone is suggesting that every connection a server
opens actively to a downstream entity or accepts passively from an
upstream client remain open forever.

The essence of the problem simply is that two high-signaling traffic
proxies (or a UAC and its default outbound proxy) would like to keep
a TCP (or TLS) connection open for traffic between them.  This
alleviates negotiating TLS security keys or TCP 3-way handshake for
each transaction going between them.

Admittedly, this was not too much a problem when UDP was the preferred
mode of transport for SIP signaling.  However, for good reasons, TCP is
becoming the preferred transport.  So I don't see why we can't have some
thought put into investigating this problem.

Section 18 of rfc3261 correctly instructs implementors to close
connections after a certain time (64*T1).  It also recognizes that
two proxies in a peering relationship will actually have two
connections open towards each other (which can be avoided).  And it
also rightly defines "persistence" to mean a transaction duration.
rfc3261 must ensure that the transactional integrity of SIP is
preserved, and it does.

All that is being done now is an attempt to investigate an extension
that will enable "persistence" to mean some duration longer than
a transaction's lifetime.  Exactly how long, how to negotiate it (or
not) is what comes next.

Cheers.

- vijay
--
Vijay K. Gurbani  vkg@{lucent.com,research.bell-labs.com,acm.org}
Wireless Networks Group/Internet Software and Services
Lucent Technologies/Bell Labs Innovations, 2000 Lucent Lane, Rm 6G-440
Naperville, Illinois 60566     Voice: +1 630 224 0216

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