Satisfying the need for WAN speed

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Most people, and even communications manufacturers, misstate the term 'speed' when what they really mean is capacity.

Want to know the best way to measure speed and pedal to the metal performance on a WAN?

First, you have to understand that speed is not just a function of bandwidth and capacity across a single or multiple networks. It involves a variety of factors -- like the distance between the endpoints and the linked networks -- that all fall under the category of network topology. Topology is something every network administrator should think about as part of initial network design and continue reviewing as the network is expanded and resources added or shifted around the building of campus.

More considerations for improving WAN speeds

Other things to consider in terms of the impact of latency and network throughput, from the experts on our IT Knowledge Exchange:

  • Networks do not transfer data in a continuous stream, but in small packets. The server sends a packet to your computer, which sends an acknowledgement back (TCP/IP protocol). Upon receipt of the acknowledgement the server sends the next packet, sort of like a game of ping-pong.
  • The speed at which these packets can be sent is limited by the speed of light and laws of physics, as well as the distance between you and the server. The speed of light is 299,792 kilometers/sec.  
A high-capacity capability and slow link does not always pave the way for faster transfer speeds.

The maximum number of ping-pongs per second is therefore 299,792 divided by twice the distance between you and the server. If the server is 1,000 kilometers away, that's 149 ping-pongs per second.

Every networking ping-pong is 1 packet, so if the packet size is 1 bit the server can only send you 149 bits per second. The speed of the network is immaterial, even a gigabit network cannot break the speed of light. The server is not sending data while waiting for the acknowledgement, waiting means less throughput, so the speed is reduced because of the distance. The further the distance from the server, the lower the speed.

  • Most people, and even communications manufacturers, misstate the term 'speed' when what they really mean is capacity, since networks are all limited by the same speed barrier but are capable of transferring different amounts of data in each packet. This is why some networks are faster than others -- they are capable of managing higher capacities of data.
  • A high-capacity capability and slow link does not always pave the way for faster transfer speeds. The reason: In order to manage file transfers, a computer is sending dozens of little control messages back and forth. The interactivity of the computer system and computer communications in general, depends on interactivity and these little back-and-forth messages.

WAN performance measurement tools

There are a number of dependable network performance measurement tools on the market that can automatically track speed and quality of service issues across a WAN. These include products from:

Want to try out a performance testing utility for smaller networks and telecommuting applications? Check out Qcheck from Ixia (www.ixiacom.com). It's free and can reportedly test networks using ICMP, TCP, UDP, IPX and SPX protocols.

Have a comment on this tip, or want to add your own thoughts? Send an email to tscannell@techtarget.com.


This was first published in April 2009

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