[c-nsp] Cisco WAAS on DICMOM image transfer - Clarifications and recommendations

[Arun Kumar]

Hi Netpros,

We have been doing a POC with one of our healthcare customers who are using
radiation imaging using DICOM/PACS standards. We are evaluating benefits of
WAAS with respect to this specific application. Expectations from the
customer are two-fold:

a. Reduce the transfer time of images between application and endhost
(radiation device)

b. Optimize WAN bandwidth and perform consistently with varying network
performance (latency and packet loss)

Referring to this Cisco whitepaper on this topic:
http://www-v6.cisco.com/c/dam/en/us/td/docs/solutions/Verticals/waasapno...
<http://www-v6.cisco.com/c/dam/en/us/td/docs/solutions/Verticals/waasapnotes.pdf>

POC is conducted with various features turned on in WAAS - 1. TFO only 2.
TFO with LZ and LZ 3. TFO with DRE-adaptive

Observations are below:

1. TFO only - Could not see any benefit compared to without WAAS turn on

2. TFO and LZ - Could see benefits shown in WAAS CM (18% between original
and optimized traffic). But there is no improvement on the transfer time.
Also the peak bandwidth remains the same on the WAN

3. TFO, DRE adaptive and LZ - See huge benefits due caching - both on
bandwidth savings and transfer time

Since customer would not typically re-transmit the same images multiple
times in a day, caching is not applicable to customer network.

Below are the clarifications and recommendations that we seek after the POC:

a. With compression enabled, this would also improve the transfer time of
images. We are not seeing it though. Can this be related to compression and
decompression time taken by vWAAS which is off-setting the end to end WAN
latency (50ms). Or any settings to be enabled to see transfer time
improvements?

b. For TFO to be effective, do we have to increase the buffer size and
window size?

c. Any recommendations on the WAAS settings specific to DICOM image
transfer?

Thanks in advance,

Arun