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.
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:
