It's no secret that the number of remote and mobile workers is increasing, stressing IT departments and their connectivity options. When it comes to remote virtual desktops, WAN acceleration technology can help iron out some of those kinks.
Delivering virtual desktops remotely has become a simple challenge of providing more bandwidth for increasing user counts. Most enterprises have bandwidth constraints, while remote users are awash in increasing bandwidth availability.
Plus, sharing bandwidth across hundreds or thousands of users means the users will encounter a less-than-ideal
So, aside from increasing the budget for bandwidth, what can you do to improve VDI performance for the remote user?
What's WAN got to do with it?
WAN optimization is here to help. It's a set of technologies that balances performance, meters access, compresses data and ultimately reduces the impact of limited bandwidth for the end user.
More on WAN acceleration
The truth about Citrix HDX and WAN acceleration
Dealing with the VDI bandwidth dilemma
Evaluating remote desktop WAN optimization
WAN optimization starts in the data center, most notably at the edge of the network, where internal and external connectivity merges to provide access to remote users. However, the first step toward WAN optimization requires intricate knowledge of network traffic.
To determine what traffic is on the network, you need network monitoring tools. Once you catalog and examine traffic, you can figure out how to optimize WAN performance.
Many WAN optimization projects start with installing WAN acceleration technology, usually called an accelerator, which introduces packet compression and packet deduplication into site-to-site communications.
To help you understand how traffic traverses the WAN, choose a WAN acceleration product that incorporates traffic analysis and reporting. With that information, for instance, you can give VDI sessions a percentage of total bandwidth or set to fixed maximums, which can be used to increase the number of sessions that can connect.
You can also define network policies by controlling traffic through quality of service (QoS), where certain types of data packets are given priority over the network. Key examples include video and Voice over Internet Protocol (VoIP) traffic, which react poorly to low-bandwidth, high-latency connections. QoS is a good starting point for WAN optimization, but it's only a start. Display protocol selection, deduplication and client-side VPN connections can all affect WAN optimization.
Most important of all, WAN optimization requires you to come up with a way to measure remote desktop performance without hampering functionality. WAN acceleration technology and other tools that measure performance from the endpoint back to the WAN offer the best methodology to measure results.
WAN optimization challenges
Deduplication technologies in WAN accelerators can address some bandwidth issues, but it's not always about bandwidth. Issues such as out-of-order packets cause retransmissions higher up in the stack, which decreases application performance in VDI sessions.
Solving packet-ordering problems will make a significant difference to VDI performance. WAN acceleration vendors use technologies such as Forward Error Correction (FEC) and Packet Order Correction (POC) to address the problem. FEC rebuilds dropped packets on the far end of a WAN link, and POC re-sequences packets that are delivered out of order.
You also need to consider what type of VDI implementation you're optimizing. TCP-based VDI protocols such as Citrix ICA can be accelerated by vendors, including Blue Coat, Riverbed and Silver Peak, but not all VDI implementations rely on TCP. Part of VMware's PCoIP, for example, runs on the User Datagram Protocol (UDP), as does Sun Ray ALP. The only WAN optimizer that claims to accelerate PCoIP and UDP is Silver Peak.
Also be aware of packet flows, where VDI implementations usually require that each client maintains at least one flow, with some peaking at 10 to 15 TCP flows at any one time. That means WAN acceleration products must be able to support huge volumes of concurrent flow or risk scaling issues.
It's also critical that WAN optimization tools are application aware, so they know how to accelerate certain kinds of traffic. However, many WAN optimizers classify applications based on port numbers, which is ineffective in many VDI environments. Instead, WAN acceleration technology needs to deploy a deep packet inspection (DPI) engine to understand what type of application is running.
WAN optimization can bring the benefits of VDI to branch offices and remote users. Still, challenges remain, and throwing money at additional bandwidth may not be the answer. It all comes down to identifying where WAN performance gains can be had, which takes intimate knowledge of the network and the traffic traversing it.
This was first published in July 2012