Re: [Tsvwg] Re: WGLC on draft-ietf-tsvwg-prsctp-00

Sourabh Ladha (EED) wrote:

>You can't send the FWD-TSN until the left edge of the number
>of TSN's is concurrent with your "abandoned chunk"
>
>
>  
>
>>Just because you abandon it does not mean you tell the peer.. you have
>>to follow all or the normal RFC2960 procedures and ONLY when you
>>have marked it to abandon and you would have retransmitted and the
>>left edge is aligned will you send the FWD-TSN... you may decide
>>to delay a while... aka the 200ms but you send only at the normal
>>retrans opp..
>>    
>>
>
>So consider this:
>
>everything before has been ACKed
>-----TSN101----> XlostX
>-----TSN102----> 
>-----TSN103---->
>-----TSN104---->
>-----TSN105----> 
>
>----TSN101-----> retransmitted
>---abandon 101--
>Now all your three points for sending a FW-TSN (as mentioned by you above) hold. So,
>
<<<<<here is your error... no stimulus

>-----FW TSN----
>  
>
So you can't send the FWD-TSN here.. unless a T3 occured

>Where is the "at least 1RTO"?? What if the FW TSN now reaches before TSN 101 going on a possible alternate path? 
>  
>
You have not reached a point to retransmit it yet...

You must hit a RTO or 4 strikes the key is in A4 and A5... you must
have a stimuleous to send the FWD-TSN i.e. a T3-Timeout (A5) or
a SACK (A4)..

You retransmitted 101 as shown for one of two reasons (before
it was abandoned)...

If you retransmitted TSN101 due to T3.. you are collapsed to 1 MTU and
have burnt that in sending TSN101. If the SACK of 105 is the 4th strike
for fast retransmit... you have sent 101 and have done a CWND reduction
and must await the T3 for 101 or a SACK for 101... so you have
no chance to send the FWD-TSN until a SACK or T3 occurs...

I see at a minimum a RTO or if 101 is sack'd no FWD-TSN is needed...

R

>
>-S
>
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