[e2e] TCP Performance in Satellite Networks

[Craig Partridge]

Remind me what RR-TCP and TCP DSACK do mechanically?

Also, increasing dupthresh is inevitably going to increase timeout events.
Even with reordering, sometimes dupe acks do loss and by increasing the
threshold you're going to see more timeouts.

The question is whether by increasing the dupe ack threshold you (a) reduce
the number of spurious retransmissions and thus (b) improve performance
enough that the occasional longer delay for a real retransmission is worth
it.

Craig


In message <14239.195.92.67.79.1091089356.squirrel at 195.92.67.79>, "Arjuna Sathi
aseelan" writes:

>
>Dear All,
>  I am a PhD student and am testing the performance of TCP on
>Satellite Networks when packet reordering occurs. I am a novice, so please
>excuse me if somethings are irrelevant. I perform reordering
>by normal distribution and packets are delayed in the range of 0ms to
>200ms. This error module was attached to all the satellite nodes. I use an
>Iridium constellation network. I perform experiments for 100s. The maximum
>congestion window was set to 500.
>
>>From what I see is that when I use Sally Floyd's RR-TCP and TCP DSACK -
>the performance was similar to standard TCP SACK. DSACK's were generated
>and received successfully but the restoration of the congestion window
>upon false retransmits never took place!! Even though I had a high maximum
>window size, the congestion window grew only upto 10 segments.
>
>Moreover when I increase the dupthresh values (to 4,5,6), I see more
>timeout events, so I guess increasing the dupthresh values when reordering
>occurs is not the right way since it leads to more timeouts because of the
>large RTT. Am I right? I would like to know why does RR-TCP and DSACK have
>no impact on the performance. Has anyone tested the performance of both
>the protocols on a Satellite environment? I would be very much obliged if
>someone could clarify these doubts please.
>
>Regards,
>Arjuna