ttcp performance test command syntax, etc.

Unanswered Question
Jan 26th, 2008

I'm working for an ISP. Since our clients often ask for testing performance on dsl and sdh links in the mpls cloud and I didn't found a method at work except IP SLAs udp jitter operation -which is quite useful, but not realistic-, I started using ttcp.

It only works on the CE -> PE uplink as it seems not to support vrf.

It could also work from a backbone router which imports loopback ip management addresses through bgp from every client for the backbone -> CE downlink.

There's not enough information on ttcp online, as it's a Cisco undocumented command. (You can read some info on

Can anyone provide the following?

i. command syntax,

ii. options (maybe vrf?),

iii. description on how it works,

iv. other ios built-in performance test method.

buflen is buffer lenght

nbuf in buffer number

port is port

The other options are not clear.


transmit or receive [receive]:

buflen [8192]:

bufalign [16384]:

bufoffset [0]:

port [5001]:

sinkmode [y]:

rcvwndsize [2144]: 4096

show tcp information at end [n]:

ttcp-r: buflen=8192, nbuf=2048, align=16384/0, port=5001, rcvwndsize=4096 tcp


transmit or receive [receive]: trans

Target IP address:

buflen [8192]:

nbuf [2048]: 50

bufalign [16384]:

bufoffset [0]:

port [5001]:

sinkmode [y]:

buffering on writes [y]:

show tcp information at end [n]:

ttcp-t: buflen=8192, nbuf=50, align=16384/0, port=5001 tcp ->

I have this problem too.
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Joseph W. Doherty Sat, 01/26/2008 - 13:02

TTCP isn't unique to Cisco, documentation for it can be found on the web.


One problem with TTCP on Cisco routers, most(?) IOS images don't have it. (More likely on service provider images?) Second problem, I found it often can't stress bandwidth except on smaller links. (The stats for drops/retransmits is good though, if provided.)

You can obtain PC versions of TTCP. I like the DOS PCATTCP which also supports UDP tests.

useridcisco Sat, 01/26/2008 - 13:21

The topic focus on ttcp on Cisco routers and testing between routers, i.e., the ce-pe and lan-lan connections in the isp's mpls cloud.

useridcisco Sat, 01/26/2008 - 13:27

The document you mention, that's ID 10340, contains the link I've already posted (Netcordia), which is far more specific.


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