One way of improving perceived performance is to ensure that the most important applications get priority. Typically, applications are allocated to classes of service (typically platinum, gold, silver, and bronze), and then policies are set for each class. For example, platinum traffic might be guaranteed at least 50 percent of the available bandwidth.
Three or four categories are typical, says Danny Price, solutions manager at Vanco Australasia, but some organisations use as many as six. A larger number is too hard to manage, he says.
Some category decisions are easy, such as blocking or severely limiting peer-to-peer file sharing, says Owen. Packeteer's software supports auto-discovery and auto-configuration, after which priorities can be fine-tuned to suit the needs of the organisation.
The traffic shaping capabilities of routers are "generally all that you need to get you started," says Atkinson. "A lot of places don't take the basic steps." If further improvements are needed, the Packeteer PacketShaper is a good product, he says.
Hayes warns that people don't always understand the impact of packet shaping, which can be negative if not done correctly. "We understand the applications and how to configure the [Packeteer] devices to provide the appropriate performance for the applications [along with detailed reports that the network administrator needs]," Hayes says.
Path optimisation can be used in conjunction with service classes, says Steve Wastie, director of strategic alliances at Peribit. For example, two sites might be connected by frame relay plus a higher bandwidth VPN link via an ISP. ERP traffic might always be sent by frame relay, while internal e-mail goes across the VPN as long as the latency does not exceed 200ms. This makes good use of the infrastructure, and "is a critical enabler for us", Wastie says.
Modesto points out that you may need to shop around among providers (or get an expert to point you in the right direction) to get a WAN link with the characteristics needed for your application to work at peak performance. Price says that where multiple carriers are involved (say one in Australia, another handling international traffic and the third within the US or Europe) it's important to ensure that the different classes of service are correctly aligned for optimum performance. In particular, real-time traffic must be kept in the top class all the way through the infrastructure.
3. Compression
"You're always going to have a bandwidth limitation," says Wastie. Changes such as the perceived need for disaster recovery, ever-growing PowerPoint decks and the tension between increasingly distributed staff and increasingly centralised infrastructure soak up previously spare bandwidth, while locations in rural areas and hard-to-service facilities such as oil rigs will always have limited bandwidth.
Where this is the problem, compression could be the answer. Modern compression algorithms, including those used by Peribit and Packeteer, are able to recognise patterns in very large data streams perhaps weeks apart. This gives better results than traditional algorithms that use a limited window, perhaps as small as 1Mbit of data.
Compression is actually a combination of compression and caching, says Owen. He says Packeteer uses four different algorithms to suit the requirements of different applications. For example, file transfers can benefit from relatively slow but thorough compression, while packets for a transactional application should be handled as fast as possible.
"Having TCP rate control and the level of compression [handled by one appliance] by far provides the best value in terms of optimising the network," says Owen. The functions can work against each other if they are separated, and the most aggressive application will still win. Correctly implemented, compression can increase the throughput as much as fourfold, he says.
