[nsp] NM-1T3/E3 problems

[lee.e.rian at census.gov]

Hi Ryan,
It sure sounds like a windowing problem.  Take a look at
  http://www.psc.edu/networking/perf_tune.html
for instructions on how to enable high speed transfers on various systems.

Or you can always use a sniffer to figure out what's causing the slow xfer
speed.  There's a bunch of free sniffer programs; the one I like is
ethereal.  Get it at
  http://www.ethereal.com/

Chances are pretty good that you're going to see retransmissions and/or the
sender stopping & waiting for an ACK.  Retransmissions is a packet loss
problem & the sender stopping until it receives an ACK is a window size
problem.

For what it's worth, I'd say the most common reasons for slow file
transfers are
1. NIC speed / duplex mismatch
2. window size too small
3. packet loss

Good luck.
Lee


------- original message -----------------------

Message: 6
Date: Fri, 30 May 2003 12:25:56 -0700
From: "Ryan Roylance" <ryan at opsource.net>
Subject: [nsp] NM-1T3/E3 problems
To: <cisco-nsp at puck.nether.net>
Message-ID: <001201c326e1$4b22e120$9f1114ac at accelica.com>
Content-Type: text/plain;            charset="us-ascii"

Thanks for any help in advance

I have a T3 terminated on either end by Cisco 3725 routers with NM-1T3/E3
cards in them.  I can utilize the full pipe with UDP packets but when I use
TCP packets I am capped at about 1mb to 2mb per session.  For example I can
open up an scp session from a host on one side to the other and get 1mb to
2mb throughput, open up another session at the same time and using the same
hosts and get 1mb to 2mb on that session as well but no more.  If I use a
traffic generating tool on those hosts I get the same results with TCP, but
with UDP I can use the majority of the T3.  I opened a TAC case and they
suggested windowing might be my issue, so I monkyed
with it for a while, no matter what I set the window to the speed issues
remained.  Below are the interface configs.

ROUTERA
interface Serial2/0
 mtu 4470
 ip address 172.31.3.2 255.255.255.0
 ip ospf message-digest-key 10 md5 7 *********
 load-interval 30
 dsu bandwidth 44210

ROUTERB
interface Serial2/0
 mtu 4470
 ip address 172.31.3.1 255.255.255.0
 ip ospf message-digest-key 10 md5 7 ********
 load-interval 30
 dsu bandwidth 44210

Thanks again for any help or thoughts on where to look for the problem.

ryan

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