Tuesday, December 28, 2004

Ethernet's Hidden Speed Trap

If you have a local area network, chances are that you're using 10 Mbps Ethernet, 100 Mbps Fast Ethernet or perhaps even 1,000 Mbps Gigabit Ethernet. So, are you getting all the bandwidth that your network is capable of? Or are you losing as much as half of your potential throughput to packet collisions?

The original Ethernet design included a clever mechanism called CSMA/CD to let all of the network connected equipment share a common party line for transmitting and receiving. CSMA/CD stands for Carrier Sense Multiple Access/Collision Detect. That's right Collision. Each device is expected to listen for network activity and only transmit when the line is quiet. But, like pulling out onto the freeway, sometimes unfortunate collisions occur. The packets get jumbled and all parties back off to wait for another opportunity. This need to take turns talking and listening can reduce the efficiency of the network by as much as 50%.

A design update in 1997 added the capability of full duplex operation with separate transmit and receive lines. The original Ethernet used hardware called hubs to make the party line connection between computers, servers, printers, etc. The full duplex approach uses switches instead of hubs. The switches make sure that data from the sending party goes to the receiving party unbeknownst to other equipment on the network. With full duplex you are utilizing the complete transmit and receive bandwidths of your network simultaneously. No, it doesn't speed up the packet transmission rate. But by eliminating all that network congestion, it might well seem that way.

If you are wondering why your network might be running slower than expected, make sure all those ancient hubs are replaced by switches and that all of your NICs or Network Interface Cards are capable of the speed you desire. Ethernet was designed to make digital communications easy and will try to keep working even with a hodgepodge of connections.

If you are interested in getting quotes for Ethernet, Fast Ethernet or Gigabit Ethernet for Metropolitan, Point to Point or Wide Area Networks, find the latest Ethernet service prices here.

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