[SFtrack] Updated: (XECS-1589) SipXecs does not gracefully handle broken TCP streams
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http://track.sipfoundry.org/browse/XECS-1589?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dale R. Worley updated XECS-1589:
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Attachment: reboot2.pcap
Attachment reboot2.pcap is a similar trace. The SUBSCRIBE is frame 845 and the
NOTIFY is frame 850.
> SipXecs does not gracefully handle broken TCP streams
> -----------------------------------------------------
>
> Key: XECS-1589
> URL: http://track.sipfoundry.org/browse/XECS-1589
> Project: sipXecs
> Issue Type: Improvement
> Environment: sipXecs 3.10
> Reporter: Brad Marusiak
> Assignee: Dale R. Worley
> Attachments: polycomRepro.pcap, reboot1.pcap, reboot2.pcap,
> sipx-snapshot.zip
>
>
> Restating Brad's analysis to clarify where sipX needs improvement:
> First, the Polycom phone on rebooting is not properly tearing down its TCP
> connection. On a restart we attempt to unSUBSCRIBE from the BLF dialog
> (packet 93) but the TCP stream is never concluded with a FIN tagged packet.
> Ideally the phone should terminate the TCP stream to ensure that the other
> SIP element does not attempt to use the stream afterward, but that cannot be
> enforced, as the phone may restart due to a power failure.
> Second, on restart after the phone re-registers and resubscribes, the sipX
> server (RLS) is sending the CSEQ 0 NOTIFY (packet 718) in answer to the new
> SUBSCRIBE (#716). sipX does not initiate a new TCP stream because it believes
> that the old TCP stream is still working.
> The TCP packet's contents will not be successfully received, since the phone
> does not know of the TCP stream. The phone returns an RST packet to sipX.
> The sipX SIP stack returns a transmission failure to the RLS "Subscribe
> Server" which terminates the subscription but the SIP stack does not attempt
> to re-send the NOTIFY in any way.
> After 30 minutes have elapsed, the phone will initiate its resubscribe. As
> the RLS has destroyed the subscription, the phone will receive a 481
> response, in which case it should attempt a new subscription. Alternatively,
> the phone may attempt a new subscription outright. In either case, the phone
> establishes a new subscription.
> Note that in SIP the NOTIFYs of a SUBSCRIBE are NOT required to be returned
> by any particular transport or stream, other than as specified by the Contact
> URL of the SUBSCRIBE.
> Technically, that sipX does not gracefully handle broken TCP connections is
> probably not out-of-specification, but as seen above, it can cause
> operational problems. We should have a better strategy to handle broken TCP
> connections.
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