Subject: [Tsvwg] SCTP: Fast Recovery questions

From: Hendrik Land <[email-masked]>
Date: Fri, 29 Sep 2006 16:18:52 +0200

Hi list,

I have some general questions regarding the fast recovery mechanism. I
assume the following scenario:

We are in Fast Recovery phase (cumulative ack < fast recovery exit
point, a fast retransmit has been performed).

1.) When another fast retransmit event occurs, do we send another fast
retransmit (even though we are in fast recovery phase) or do we only mark
packets for retransmission?

2.) All packets that have been tagged for retransmission have been
retransmitted and cwnd allows more data to be sent. Do we send this data or do
we wait until fast recovery is over?

3.) Similar to question 2 but we do have retransmissions outstanding
that can not be retransmitted due to cwnd restrictions. Do we send new data
instead to use up the cwnd?

I couldn't find a clear answer to these questions in the RFCs. All comments
appreciated.

Regards

Hendrik

---

From: Randall Stewart <[email-masked]>
Date: Thu, 05 Oct 2006 06:26:06 -0400

> packets for retransmission?
Sure. And if you are not fast-retransmitting to a alternate you can
even do multiple fast retransmit of the same TSN... Of course you
need to monitor the strike point and base it on the next TSN
every time you FR so you truely wait... either Armando or Jana
had a paper on this if I remember right :-D

> we wait until fast recovery is over?

Sure..

> instead to use up the cwnd?

This question makes no sense ot me... if you have cwnd restrictions then
how can you send new data to use up the cwnd?

Maybe you mean the retransmissions went to an alternate (which really
should only happen with a T3 timeout)... in that case sure, I would
send new data to the old address... if all the retransmissions are
queued to an alternate..

R

-- 
Randall Stewart
803-345-0369 <or> 815-342-5222(cell)