[nsp] NM-1T3/E3 problems

[Mourad BERKANE]

What is your RTT between RouterA and B?

TCP bandwith limitation come sometimes from TCP windows size and RTT.
When RTT < 1 ms, the 64kbytes TCP limitation is not a problem (LAN
environment)
Each time you cross a Long Fat Network (LFN), example of 500 ms, TCP
throughpout could decrease to 1 Mb/s even if you do not suffer of a lack of
capacity.

Mourad

-----Message d'origine-----
De : Ryan Roylance [mailto:ryan at opsource.net]
Envoyé : vendredi 30 mai 2003 21:26
À : cisco-nsp at puck.nether.net
Objet : [nsp] NM-1T3/E3 problems


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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