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Webcast-Catalyst9k
New Member

ATM IMA Error

Hi - I have a router configured with ATM IMA & 3 X ATM 2Mbps circuits which never reaches it's max 6Mbps bandwidth. I fully understand about IMA & ATM overhead and that I should not reach 6Mbps however I am only reaching 4.6Mbps. The router does have qos but the same problem occured before the qos was added. This problem also occurs on antoher IMA router elsewhere so I'm pretty sure it's not a code or hardware error. Here's the IMA config:

network-clock-participate wic 0

network-clock-participate wic 1

network-clock-participate aim 1

network-clock-select 1 E1 0/0

network-clock-select 2 E1 0/1

network-clock-select 3 E1 0/2

controller E1 0/0

mode atm aim 1

!

controller E1 0/1

mode atm aim 1

!

controller E1 0/2

mode atm aim 1

!

interface ATM0/0

no ip address

scrambling-payload

ima-group 1

no atm ilmi-keepalive

no fair-queue

interface ATM0/1

no ip address

scrambling-payload

ima-group 1

no atm ilmi-keepalive

no fair-queue

interface ATM0/2

no ip address

scrambling-payload

ima-group 1

no atm ilmi-keepalive

no fair-queue

!

interface ATM0/IMA1

no ip address

ip accounting precedence input

ip accounting precedence output

ip route-cache flow

no atm ilmi-keepalive

service-policy output qos

!

interface ATM0/IMA1.100 point-to-point

ip address x.x.x.x 255.255.255.252

ip accounting precedence input

ip accounting precedence output

ip nbar protocol-discovery

pvc 1/100

vc-hold-queue 1024

encapsulation aal5snap

Can you see any obvious mistakes that would explain the problem, or do you know of any known IMA additional configuration that may be required?

3 REPLIES

Re: ATM IMA Error

Hi,

how do you measure the maximum throughput? Is this application level like an FTP download? Or did you just do a "show interface"?

You are not too far from the theoretical limit taking into account ATM and IMA overhead. Accounting for the 40 Byte TCP/IP header and assuming an average packet size of 500 Bytes you would expect about the measured 4.6 Mbps.

How much would you expect based on your measurement method?

Regards, Martin

New Member

Re: ATM IMA Error

I am using MRTG & a Netflow application level server to measure the throughput. Maybe I have my calculations wrong, and I am no ATM expert (hence this post) but I was expecting a greater throughput.

New Member

Re: ATM IMA Error

chris,

mrtg gets its stats via snmp so what you see is the same as sh xxx command

i would suggest a little .exe program, one runs on one end and the other at the other in server mode. they pump packets and you get real time reading, it is called NetCPS.exe but I cant figure a way to post it here

NetCPS 1.0 - donated into the Public Domain (almost) by Jarle Aase

THIS PROGRAM IS NOT LISENCED TO GOVERNMENTAL OR MILITARY USE.

Usage: NetCPS.exe [options] [Remote host]

-Pn Port number. Default port is 4455

-server Server mode. (Default is client)

-mn Megabytes to transfer. Default is 100

Note: 'n' represents a number.

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