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Hi,

I have used SCTP pre-release 12 (including the patch issued by Andreas
Jungmaier, in his reply on "Network status change in Pre 12", sent on the
21st June) and deployed the following scenario:
A dual-path communication between "terminal" and "echo_server", while
simulating a network failure.
The both sides were dual-homed and were connected via two LANs. After the
association was established, the path 0 was declared as primary path. Then I
sent several packets from the terminal to the echo server, whilst receiving
SACKs and DATA, all the time using the primary path 0 for transmits and
retransmits. After a while, I decided to provoke a failure of the path 0 by
pulling out the cable from the hub. Immediately after the network failure, I
created new data packets at the terminal side. The first data chunk after
the network failure, was sent at the relative moment, approximately t = 15
sec. Because the SCTP entity at the terminal side did not yet detect the
path 0 failure, it continued to consider this path as primary and thus sent
the packet through the path 0. But, the terminal did not receive an
acknowledgement for the sent data chunk, and the terminal SCTP entity
decided to retransmit the lost data chunk via the secondary path (i.e., path
1). The moment of the retransmission of this chunk is approximately t = 16
sec. Hence, the retransmission via path 1 occurred about 1 sec after the
initial attempt to transmit the packet via path 0. The round-trip time
seemed to be around 0.7 msec, thus more than 1000 times shorter.

The questions are:
Why was the retransmission via the secondary path so much delayed?
Should it not occur, in principle, immediately after the retransmission
timer expiration?
What parameters does that 'failover-duration' depend on?

Best regards,
Marjan Bozinovski

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• RE: [SCTP-Discussion] Off Topic - M2UA/M2PA open source, Tuexen Michael, 07/13/2001
  • [SCTP-Discussion] Path failure management, Marjan Bozinovski, 07/13/2001
    • Re: [SCTP-Discussion] Path failure management, Michael Tüxen, 07/13/2001
      • Re: [SCTP-Discussion] Path failure management, Marjan Bozinovski, 07/14/2001
        • [SCTP-Discussion] Unclear statement, Marjan Bozinovski, 07/14/2001
          • Re: [SCTP-Discussion] Unclear statement, Michael Tüxen, 07/14/2001
            • Re: [SCTP-Discussion] Unclear statement, Marjan Bozinovski, 07/14/2001
              • Re(2): [SCTP-Discussion] Unclear statement, Michael Tüxen, 07/14/2001
              • Re: [SCTP-Discussion] Unclear statement, M. Mueller, 07/15/2001
              • Re(2): [SCTP-Discussion] Unclear statement, Michael Tüxen, 07/15/2001
              • Re: Re(2): [SCTP-Discussion] Unclear statement, M. Mueller, 07/16/2001
        • Re(2): [SCTP-Discussion] Path failure management, Michael Tüxen, 07/14/2001

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