Monday, October 26, 2009

Wan Optimization for VDI and ICA

By:Rick Davis


Wan Optimization Controller (WOC) vendors claim the ability to enhance ICA (the Independent Computing Architecture protocol for remote application and desktop delivery) but there’s a sizable gap between what they say they can do and what they actually deliver. Here’s a view into the limitations of their support for optimizing ICA:




ICA
Prioritization


ICA
Compression


ICA
Caching


Blue Coat

Yes

Native Payload

Byte Stream

Cisco

Yes

Native Payload

Byte Stream

Citrix Repeater

Yes

Yes

Yes

Expand

Yes

Native Payload

Byte Stream

Riverbed

Yes

Native Payload

Byte Stream


Quality of Service: All vendors can prioritize ICA based on the Priority bits defined in the ICA Protocol header.


Compression: Not all ICA Compression is equal.


Citrix servers encrypt and compress ICA by default. While all vendors can compress ICA effectively, they typically can’t do it unless the server-side encryption and compression have been disabled so that the payload is in its native form. This creates challenges in mixed environments where some sites have WOC’s but others do not. Sites without a WOC are penalized twice: their traffic will not be secure and then their bandwidth utilization will increase; at the Headquarters too.

Not true for the Citrix Repeater, which dynamically negotiates the secure ICA session, for those clients that have a corresponding repeater with them at the remote site, to selectively disable server-side compression; Reducing the burden on the WAN and servers while providing confidentiality and ensuring that there are no penalties imposed on non-optimized sites.
Caching: Not all caching is equal


Byte Stream caching (a.k.a. Dictionary Compression, Network Sequence Caching, and de-duplication) operates by replacing repetitive WAN data packets with “tokens”. But because this technique is not protocol specific, it is not able to cache the ICA bitmap images being sent across the wan. And when the images have been compressed or encrypted by the server, there is even less opportunity for effective Byte Stream caching.


Here too the Citrix Repeater has the leg up on the competitors because it will recognize and parse the incoming ICA session, making itself known to the client and the server. Next, the Repeater will act as an intermediary for the encryption, enabling it to participate in the ICA conversation and begin caching at the application layer. This maintains the integrity of end-to-end encryption and enables the Repeater to cache the actual ICA bitmap images, print jobs, file transfers, and streamed media being delivered via the ICA Protocol.


Virtual Desktop Initiative:


On November 20th, 2009 Citrix will provide Repeater software version 5.5.1 which enables the ICA optimization for XenDesktop. Customers with Repeater maintenance agreements will be entitled to this software update.



blog comments powered by Disqus
Microsoft Virtualization, Citrix, XENServer, Storage, iscsi, Exchange, Virtual Desktops, XENDesktop, APPSense, Netscaler, Virtual Storage, VM, Unified Comminications, Cisco, Server Virtualization, Thin client, Server Based Computing, SBC, Application Delivery controllers, System Center, SCCM, SCVMM, SCOM, VMware, VSphere, Virtual Storage, Cloud Computing, Provisioning Server, Hypervisor, Client Hypervisor.