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we have to test sctp assosiation intializing between two ubuntu servers. We use sctp_darn on one server(B) to listen and on another(A) to send data. Every thing is Ok we could send data from one to another with sctp protocol.

but when we look on wireshark - we see that in assosiation initializing phase server A send INIT twice - without any delay between them

time1: server A --INTI--> server B time2: server A --INTI--> server B .....

time2 is the same as time1 - but as I understand there should be T1-init timer.

ubuntu used - 14.04 kernel version - 4.4.0-101-generic

both A and B - virtual, hypervisor is KVM

if it's like sctp fast retransmission how could we off it?

thanks,

Elmir Karimullin
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  • It is not a fast retransmission as it described in RFC 4960. Is it happening with INITs only or all packets that sent from server A are logged twice? It is possible that it is just related to the way you captured wireshark trace. So in reality packet was sent once, but wireshark logged it several times. – Alexander Zinovyev Dec 14 '17 at 03:15
  • lol) before starting to upgrade linux kernel i decide to check answers. you r rigth, when i use only tcpdump - i see correct sctp handshake, whithout any double INITs. thanks a lot!! – Elmir Karimullin Dec 14 '17 at 12:35

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