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[SCTP-Discussion] Retransmission when congestion window is full


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  • From: Guo Marc-YGUO1 <YGUO1 AT motorola.com>
  • To: "'discussion AT sctp.de'" <discussion AT sctp.de>
  • Cc: "'Tuexen Michael'" <Michael.Tuexen AT icn.siemens.de>
  • Subject: [SCTP-Discussion] Retransmission when congestion window is full
  • Date: Wed Sep 10 18:27:02 2003
  • List-id: SCTP Discussions <discussion.sctp.de>
Title: Message
Hi,
 
I have a question about retransmission. In our system, we see that Siemens SCTP stops retransmission after a network congestion. The network traffic is heavy. End 1 with Siemens SCTP sends many packets to end 2 with other SCTP implementation. End 2  sends SACK back with some delay and end 1 receives these SACK's all together. The SACK reports that some data is lost. But end 1 only retransmit once or doesn't retransmit at all. End 1 can still send SACK back after receiving DATA from end 2. Eventually, our application resets the link.
 
I find that the fast retransmission does be kicked off after 4 gaps in the SACK. However, the stack doesn't finish retransmission, since we don't see the retransmitted data on the sniffer. There are no major errors on the log. The other SCTP implementation on end 2 had similar problem before. It was found that the stack was holding up retransmissions when congestion window is full. Do you find the same flaw in Siemens SCTP? We are using version pre19. Thanks for the help.
 
Marc Guo
Motorola, Inc

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