If your company is like many other companies, you're probably starting to wonder where all your network bandwidth went. Along with the advent of the Internet came bandwidth intense applications like Napster, streaming audio, streaming video, interactive gaming and others, many of which are not sanctioned or supported by the organization that pays for the bandwidth that enables them.
Network managers sometimes feel that their only solution to stem the tide of performance complaints from their users is to purchase ever more bandwidth from their data carriers. While this may be good news for your ISP or data network carrier, it just spells added cost for your company.
Few network managers know the exact number of applications running over their network and the amount of bandwidth they consume. A recent report from IDC titled "WAN (Wide Area Network) Optimization" predicts the amount spent on bandwidth management technology will increase from $236 million this year to $427 million in 2008. Businesses essentially are paying millions of dollars to enable their users to swap music files and surf the Web, among other activities. Often, critical business applications suffer poor performance because they share the same WAN links as those used for non-work related activities.
Business applications such as VoIP (Voice over Internet Protocol) or ERP (Enterprise Resource Planning) that require a consistent amount of bandwidth compete with business applications that will use whatever bandwidth is available. Applications such as database replication and e-mail that are not sensitive to delay across the network will use the full bandwidth speed allowed if available. Whether delay sensitive or not, all business applications have to compete with recreational activity on the network.
For most companies, the bandwidth problem lies in three specific areas:
- Bandwidth consumption not related to business activities,
- Congestion, and
- Traffic being discarded and resent because traffic exceeds WAN capacity.
Bandwidth management devices can control these three elements and provide consistent application performance across the network.
Typically, these devices implement a variety of three approaches:
- The devices create virtual bandwidth through compression and/or caching.
- They offer traffic control with queuing and prioritisation.
- They can provide traffic shaping by managing network flows.
Compressing or caching traffic can reduce the amount of data sent over the WAN and deliver improved performance for applications. Although extraordinary compression gains may be claimed, general experience shows gains of 2 to 4 times. If you have a T-1 line (1.54 Mbps) you can more then double your bandwidth without buying more. Creating "virtual bandwidth" through compression is typically more cost effective than purchasing a bandwidth upgrade since it incurs a one-time cost rather than an ongoing monthly charge. On the downside, simply compressing and caching traffic to gain more bandwidth does not ensure that business critical applications perform as desired.
Prioritizing traffic is a method employed by WAN routers and by some bandwidth management devices. Queuing mechanisms ensure that time sensitive traffic gets priority and try to identify key applications that are high priority. The advantage to this solution is that it is included in the cost of most WAN routers. However, as with anything, you generally get what you pay for. During congestion, data packets can be delayed in the queues by an uncertain amount of time. Heavy congestion can cause data packets to be dropped entirely starting the vicious cycle of dropped packets and retransmission.
Traffic shaping can be the best approach for most organizations because it controls the rate at which data flows onto the WAN. This approach ensures that there is always enough bandwidth for the key applications and guarantees latency across the WAN link because it does not allow queues to build up. Experience shows us that traffic shaping and compression used together can show solid gains in WAN application performance.
Although each bandwidth management approach has advantages and disadvantages, application visibility is critical. Unless you know precisely what applications are on the network, it is impossible to ensure that bandwidth goes to the right applications.