On Dec 4, 2009, at 12:57 PM, Sudhanva Mudigere Narayana Gowda wrote:
Hi,
I have a query regarding sctp multihoming behavior.
I have setup a multihomed association and this is my observation
Host_A (IP a): Local single Homed endpoint
Host_B (IP b(Primary), IP c(secondary)): Remote multiHomed endpoint
During Heartbeat I see that even though the Heart beat req is to the
secondary ip of Host_B, the Host_B uses its primary ip as source when sending
back the Heartbeat Ack.
Ie Host_A (IP a) --------HEART_BEAT_REQ-----------> Host_B(IP c)
Host_A (IP a)<--------- HEART_BEAT_ACK---------- Host_B(IP b)
I guess host B is choosing the source address based on the destination
address. Host A must be able to handle this.
also during data exchange I observed that even when the data is sent to the
secondary ip of Host_B, the SACK is being sent back from the primary ip of
Host_B.
Host_A (IP a) --------DATA_MSG-----------> Host_B(IP c)
Host_A (IP a)<--------- SACK------------------- Host_B(IP b)
Same as above.
Is this the expected behavior, shouldn’t the node use the same ip on which it
received the data or Heart_beat_req on while sending back the
responses(Heart_beat_ack or SACK).
That would be good. But some stacks select the source address based on the
destination address. However, A has to accept both.
Due to this behavior if the primary ip of an endpoint fails the association
goes down as the node will not be able to transmit any Heartbeat_Req or
Heartbeat_Ack.
Yes.
On Host_A I blocked the incoming packets which has Host_B(IP b) as source and
I expected Host_B to retry using its secondary ip addr, but I observed that
even the retries from Host_B uses its primary ip .
Does this mean that an endpoint always uses its primary-ip while sending
packets, but might receive packets on primary or secondary-ip?
How an endpoint selects the source address is implementation specific.
Best regards
Michael
Thanks
Sudhanva
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