help on PA-A3-E3 configuration.. why 17Mbps vs 34Mbps_

[lcolimoro]

We have recently get a leased line 34Mbps point-to-point from TelcomItalia.

I-m not an expert on ATM and the above link requires the module in the subject.

I configured the both routers with the following config lines:

******************************

int atm6/0.100 point-to-point

ip address x.x.x.x x.x.x.252

atm pvc 1 0 35 aal5snap

**************************

I am able to ping the remote site and the show interface tells me the speed is 34Mbps, but when I run a test between 2 hosts, the data are transferred at 17 Mbps...why??

Is there any body can help me on this?

thanks for your help

[pkhatri]

Hi,

The throughput you get on a link depends on the type of data you are transferring. How are you testing this ? Is it a TCP or a UDP stream ? Where are you getting the reading of 17M from ? Also, what sort of a router are you using ?

Paresh

[lcolimoro]

I'm using a 7206VXR router at 1 site and the remote site has a 2691 router with a NM-1A-E3.

I copied the files with different sizesfrom one host to another host and they both have an interface network card at 100Mbps directly connected into the above mentioned routers.

I tried using ftp and scp(secure shell) with the same result.

Lucio

[pkhatri]

Hi Lucio,

What I was trying to get at was whether you are offering the link enough traffic. Repeat the tests and this time, get the following information:

- configure 'load-interval 3' on both your FE interface and your ATM interface

- start up your FTP and while it is running, get the output of 'sh interface' for these two interfaces on the router where the traffic is being originated from

If the FastEth bit-rate is about the same as that on the ATM interface, then you are not presenting enough traffic to be able to do the test. If it is higher, post the output of 'show interface' for your ATM so we can see why the traffic is getting dropped.

Hope that helps - pls rate the post if it does.

Paresh

[bhedlund]

One thing to note here is that the maximum throughput of a 2691 is 35Mbps (under ideal lab conditions with a constant stream of 64 byte packets).

In the real world you should not expect to see 34Mbps on that router.

I have attached a router performance comparisson chart for your review.

Please rate all helpful posts.

Brad

[mbjohnson]

Hi Lucio,

Unfortunately we've ran into a similar problem with our OC-3 link (155mbp/s). This is a limitation of the TCP/IP stack. We could only get about 25Mbp/s from our link when doing some tests. We've worked a lot with Cisco and currently are evaluating WAN hardware accelerators. We are now able to pass about 100Mbp/s over the link. You will have to look into the same solution most likely.

Good luck!

[pciaccio]

You need to look into tuning your hosts for effecient TCP and UDP windowing. See URL: http://www.internet2.edu/~shalunov/writing/tcp-perf.html