[sctp-dev] Strange closing of SCTP channel

[Jens Carlberg]

Hi!

I and a colleague are working with an application, working as SCTP server. We're seeing a strange behaviour we fail to understand, where the SCTP link closes on the server side when we are using a test client, without any reason we can perceive. When used with a "real" client, the link has no such problems. Also, the test client works well when used over the loopback interface.

The sequence looks like this:
* The server starts and accepts incoming connections.
* The client starts and connects, getting a SCTP channel. We have dumped the network traffic and can see the complete startup sequence from INIT to COOKIE_ACK.
* The client sends a request (a telecom protocol using SCTP as transport). The server sends a response. After this the link should stay open, waiting for further communication.
* After a second or two, we can see in our application that SCTP delivers a notification, a AssociationChangeNotification with COMM_LOST. There is no packet corresponding to this in the network traffic dump we have looked at.
* After about 30 seconds, the client sends a HEARTBEAT and gets an ABORT back.

When using a "real" client or loopback interface, there is no notification delivered and the link stays up. We have gotten a network dump for the "real" client case, but not for the loopback interface.

We are using...
* Java 1.6.18 with the SCTP from Java 7.
* Linux 2.6.32.12 with a hight refresh rate (1000 Hz instead of 250)
* lksctp-tools-1.0.10-2.1 and lksctp-tools-devel-1.0.10-2.1


Under what circumstances will a notification be generated? Can there be traffic we doesn't see, since we only look for traffic to/from the client? Can there be notification generated by other events?

We include the two network dumps we have collected.


///Best regards,
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JENS CARLBERG
Software Designer

Ericsson AB
FU Radio System I&V, LI/EAB/FJZ/TE
Datalinjen 4
SE-58112 Linköping, Sweden
Phone +46 107114141
SMS/MMS +46 761497941
jens.carlberg at ericsson.com
www.ericsson.com


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