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Re: [SCTP-Discussion] SCTP failover (path changeover) problem


Chronological Thread 
  • From: Michael Tuexen <Michael.Tuexen AT micmac.franken.de>
  • To: Shefiroth Tsai <shefiroth AT gmail.com>
  • Cc: discussion AT sctp.de
  • Subject: Re: [SCTP-Discussion] SCTP failover (path changeover) problem
  • Date: Thu Nov 3 16:32:02 2005
  • List-id: SCTP Discussions <discussion.sctp.de>
If you are continuously sending packets the calculation you made is correct.
I'm not sure what is going on. That is why I asked for trace. Are you sure that
the routing table is not changed when plug out the cable?

If you have only one packet, it would be retransmitted after 1 second over the
second path and you would need the HB procedure to detect the path failure which
would take longer due to the HB.Interval.

Best regards
Michael

On Nov 3, 2005, at 13:46 Uhr, Shefiroth Tsai wrote:

Sorry I am not able to provide the message trace now.
My program is an SCTP streaming application.
I think the reason is that my application continuously transmit packets from the server to the client.
Thus, several TSNs may have the same RTO, right?
Assue that when the network wire is pulled out, the ongoing TSN is 60.
Then TSN #61, #62, and #63, might have the same RTO because the server was continuously sending packets.
Therefore, the time consumed to failover can be reduced because the number of retransmissions will increase faster.
 
What I mean is:
The minimum value (63 seconds) for an SCTP association to failover is for the situation that only one packet is sent.
If packets are continuouly transmitted from the server to the client, the time consumed to failover can be reduced, right?


 
On 11/3/05, Michael Tuexen <Michael.Tuexen AT micmac.franken.de> wrote: Hi,

can you provide a message trace in libpcap format for both networks?

Best regards
Michael

On Nov 3, 2005, at 3:18 AM, Shefiroth Tsai wrote:

> Hi,
>
> I have implemented a program using the sctplib to test the time
> consumed for an SCTP association to failover.
> The client and then server both have two NICs.
> Under the test, I setup the association between the client and the
> server.
> Then I just pulled out one of the network wire of the client.
> Theoretically, it should take at least 1+2+4+8+16+32=63 seconds to
> failover with the standard configuration.
> (RTO.mix=1 sec, RTO.max=60 secs, PATH_MAX_RETRANS=5)
> However, in my tests, it surprisingly usually only took about 20
> seconds to failover.
> Why shall this happen?
> Can somebody explain the reason for me?
> Thanks a lot!

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