Wednesday, July 30, 2008

What To Consider For A WAN Optimization Solution

You're evaluating your WAN (Wide Area Network) and wondering how you can optimize performance across the network. What are you're realistic options for a solution?

Keep in mind that this isn't necessarily a bandwidth solution, such as say MPLS or ethernet is. Rather it's a bandwidth utilization question.

I would suggest looking at WAN optimization appliances: Riverbed, Juniper, Packeteer. In many cases they do a very good job with latency, especially if the main source of the problem is CIFS WAN-unaware issues (copying/opening/modifying files using Windows).

The first step in my view is to find out the path your IP packets are taking. A delay can be caused if your connection is going through satellite and not a land line (Earthbound wireless, fibre- underwater or land, etc.).

First I would suggest tracing your packets' route ..... then making an SLA with your service provider and see if they can guarantee the quality parameters you want concerning BW, delay, jitter etc.

I would'nt jump into buying or installing anything before that!

Keep in mind that all WAN-accelerators solve Latency issues. So choose any Vendor that does WAN-acceleration. But choosing the right one is not that easy. It depends on your WAN-traffic.

If you use applications (like Citrix, SAP) than a traffic priorizing Accelerator (Like Packeteer or Ipanema) will offer you the best results. However, if your traffic is more file oriented (MS-Office) ..... than you will get the best results with the Data reduction Accelerators, like Riverbed, Juniper Citrix and Cisco. In general you'll likely get the best results with Riverbed.

Wan Optimizations appliances have an effect only on TCP flows. If you have latency issues with UDP flows (voip) I don't think you can do anything against that (real time traffic is very sensitive to latency)

About generic TCP flows optimization, you'll find many vendors in the market selling products which fit well according to your needs : Citrix WanScaler, Cisco WAAS, Juniper, Riverbed, Expand and probably a lot of other vendors...

Here is the trick they all use to hide the effects of latency (they don't hide latency, because it already exists, they hide the effects), Wan optimization solutions act like a transparent TCP proxy, spoofing server's IP address to the client, and spoofing client's IP address to the server, and they send the TCP Ack messages locally. So you don't have to wait for the round trip time to get the ACK message. It helps to "fill-the-pipe" quickly. This is the great solution to avoid latency effects, as TCP throughput is highly sensitive to latency, due to the Ack return messages, also congestion control has an horrible effect when the TCP connections start.

Also they implement selective Acks and large initial flow control windows to use the total bandwidth of the WAN link. Add to this some compression mechanisms to artificially increase the bandwidth available and some layer 7 optimizations (mainly CIFS for file sharing, but also HTTP-based compression), embedded QoS stuff, and you have an overview of what we call "Wan optimization".

Whatever the vendor you choose, they all implement what I described above.

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