[Tmrg] Round table: Buffer sizes

[Lachlan Andrew]

Greetings all,

Another question on the list is buffer sizes.

I'd obviously like to standardize on the buffer sizes that WAN-in-Lab
supports "natively", namely 128 packets at 1Gbps and 16384 packet at
2.5Gbps, but they're fairly ad-hoc choices.  WAN-in-Lab can
alternatively be cajoled into using buffer sizes of any power of 2
from 128 to 8192 packets.

An obvious buffer size to set is some multiple of the BDP, but that is
not well defined if flows have different RTTs.  Setting the buffer too
large will mask the effects of RTT unfairness; for example, setting
the buffer to be the size of the maximum BDP would mean that all RTTs
are within a factor of 2, even if the actual path delays differ by a
factor of 10.

Also, Cisco buffer sizes seem to be specified in numbers of packets
not bytes, and I believe Dummynet has an option to do that too.  This
makes a "BDP-sized " buffer hard to define with bidirectional traffic,
since the number of packets depends on the fraction of ACKs vs
full-sized packets.

Given all that, can someone suggest suitable buffer sizes for this
core set of tests?

Cheers,
Lachlan

-- 
Lachlan Andrew  Dept of Computer Science, Caltech
1200 E California Blvd, Mail Code 256-80, Pasadena CA 91125, USA
Phone: +1 (626) 395-8820    Fax: +1 (626) 568-3603