[TriLUG] Tuning WAN links

[Shawn Hood]

Hey guys...

I've recently had a dedicated gigabit fiber WAN link that runs between
Rackspace in Dallas and an office in Bethesda, MD dropped in my lap.  It's
not often (read: ever) that I'm given a high-bandwidth high-latency link to
tune.

Here are the basics:

Office in Bethesda
Catalyst 3560
    |
AboveNet POP - Vienna, VA
Catalyst 6509
    |
AboveNet IP/MPLS Backbone
    |
AboveNet POP - Dallas, TX
Catalyst 6509
    |
Rackspace - Dallas, TX
Catalyst 3560


I've run iperf between two RHEL4 boxes connected to the 3560s.  The most
throughput I've been able to get is ~45mbit by increasing the buffer sizes
in /etc/sysctl and using massive window sizes on iperf.  I was hoping you
guys could point me in the right direction.  I need to do some reading about
how to get the most out of this link, and any reference would be greatly
appreciated.  Will this be a matter of create a Linux router on each end to
shape the traffic destined for this link?  Is this something better suited
for proprietary technology that claims to 'auto-tune' this kinds of links.
I'm fairly fluent when it comes to talking about this stuff 'in theory,' but
have yet to get any hands on experience.

Questions, comments, suggestions?

Shawn