RE: PMTU-D: remember, your load balancer is broken

[John Fraizer <nanog () EnterZone Net>]

> I'm having some trouble getting full throughput from a GigE pipe.
> Even in the 100baseTX/FDX down-stream, I'm not getting full link
> utilization (everything on switches, Cat6509 and 3512XLs). I'm
> considering increasing MTU sizes to MTU=4096+40, or even larger.
> Most of the data transmissions fall into the 5KB-50KB range. The
> site can be considered a large portal. What would be the effect
> on my upstream? Would it create problems? The only systems that
> see the Internet are the web-servers (dual NICs).

The one thing to consider if the fact that all devices on the ends of the
GigaE support "Giant Frames."  We have had no problems going with 4500+40
MTU server to server (direct) on GigaE but going to an HP 4000M switch, it
was a different story.  It seems that the HP's don't support giant frames.

John Fraizer
EnterZone, Inc