Home page logo
/

nanog logo nanog mailing list archives

RE: PMTU-D: remember, your load balancer is broken
From: "Roeland Meyer (E-mail)" <rmeyer () mhsc com>
Date: Wed, 14 Jun 2000 09:06:52 -0700


Valdis.Kletnieks () vt edu: Wednesday, June 14, 2000 8:07 AM

On Tue, 13 Jun 2000 22:36:08 MDT, Marc Slemko said:

It is also a concern that, in my experience, many of the
links with
MTUs <1500 are also the links with greater packet loss, etc.
so
you really don't want fragmentation on them.

The worst part here is that I suspect that most of these
links (just on
sheer numbers of shipped product) are the aformentioned Win98
576-MTU.

I just set my dial PPP ports to MTU=512+40=552, is this wrong?
Where does the MTU=576 number come from?

I seem to remember that the *original* motivation for
slow-start and
all that was Van Jacobson's observation that the most common
cause of
a TCP retransmit was that an *entire* packet had been silently
dropped
due to queueing congestion, and could thus be treated identical
to
an ICMP Source Quench.

Has this changed?  Has "fragmentation" become a Great Evil,
rather than
an annoyance that some links have to deal with?

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).




  By Date           By Thread  

Current thread:
[ Nmap | Sec Tools | Mailing Lists | Site News | About/Contact | Advertising | Privacy ]