Cisco WAAS on a low latency line

[Robert Milner]

Hi everyone,

I would just like to ask if anyone has ever used or installed a Cisco WAAS on a low latency line?  We are having a lot of problems with the device that is on the low latency line, in particular we are having a lot of issues with the CIFS part where users are complaining of really slow file access and that Windows Explorer can freeze for 30-60 seconds.

After logging a call with Cisco, we were told that installing a Cisco WAAS on a low latency line was not recommended and that we should turn off all the optimisation features and just leave TFO on.  We have not done this yet, as I am not convinced that this is the issue...

This is the output from pinging the remote site WAE-674 from our head office WAE-674:

WAE-674#ping 10.99.8.200

PING 10.99.8.200 (10.99.8.200) 56(84) bytes of data.
64 bytes from 10.99.8.200: icmp_seq=1 ttl=61 time=2.65 ms
64 bytes from 10.99.8.200: icmp_seq=2 ttl=61 time=2.36 ms
64 bytes from 10.99.8.200: icmp_seq=3 ttl=61 time=2.38 ms
64 bytes from 10.99.8.200: icmp_seq=4 ttl=61 time=2.35 ms
64 bytes from 10.99.8.200: icmp_seq=5 ttl=61 time=2.28 ms

--- 10.99.8.200 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4003ms
rtt min/avg/max/mdev = 2.284/2.409/2.657/0.128 ms

We were told that the times of 2-3ms were too low and not recommended for use with a WAAS.

If anyone could confirm this and if anyone has any thoughts or comments on this, it would be greatly appreciated.

Many Thanks.

[ktunugun]

Hi Robert,

Ideally the typical latency suited for showing WAAS benefits is 20ms and above. In your case the latency is far less. Since the WAAS optimizations (L4+L7) also add some latency to the tune of 2 - 5 ms (depending on the kind of traffic) hence the users may experince the delay with WAAS deployed on very low latency links. Hence it is suggested to disable all L7 optimization and just work with L4 (TFO+DRE+LZ). DRE can remove the redundancy on the link and thereby reduces the traffic that has to traverse WAN thereby saving WAN time. TFO can help with TCP flow optimizations and LZ can further compress the data going on WAN.

However for low latency it has to be tested with what configuration (L4 only) or (L4+L7) works well.

Regards

Kiran.

[Robert Milner]

Hi,

Thanks for your reply - just another few questions.  Does disabling the L7 optimisation mean disabling the CIF caching or is this something different?

We also have several Gigabytes of traffic going over the link each hour - does this mean we will see a dramatic increase in the amount of traffic that is going over the WAN?  Surely this will have a more detromental impact on the users?

Do you think disabling the L7 optimisation might help us on the low latency WAN?  If so, what would we need to disable?

Regards,
Rob.

[ktunugun]

Hi Robert,

Yes when you disable L7 optimzations for CIFS the CIFS caching woudn't work. However you will still get the benefit of the L4 optimizations which will remove the redundancies when going over WAN.

I have experienced in the past disabling L7 optimization has definetely helped on very low latency WAN.

You can disable the L7 Optimizations through CM GUI -> My WAN -> Device Group -> AllWaasGroup -> Configure -> Acceleration -> Enabled Features...remove the check mark from the Accelerators and submit.

Regards

Kiran