Q

Ethernet throughput

I have question about Ethernet. I manage a Network for a development company and we have one subnet with roughly

115 PC's and Servers. What would be the actual throughput one should be getting within a internal subnet if you have Windows 2000 Pro machine with a 100MB Ethernet adapter attached via a cable run to the 100 MB switch using Cat5E cable. I tested with some bandwidth with tools and states that my max throughput is 6.2MB. My test was conducted by copying 160MB file from are internal file server that is running Windows 2000 Server to a Windows 2000 Professional machine. 6.2MB this seems kind of low. I don't believe we experience high internal bandwidth usage here at my company. Does this seem normal or should I be getting better throughput out 100MB connection? Would this be the difference of using HP Procurve Switches verses a larger vendor such as Cisco? Actual throughput on Ethernet is NEVER 100Mbps if you are looking at data transfer by trying to carve up a file and assume what is being carried. There is overhead associated with Ethernet including framing, acknowledgements, etc. Typically one can expect about 1/3-2/3 of the actual speed based on several factors such as traffic. Also, if there are problems in your physical layer causing retransmissions, your throughput will suffer as well.

As for whose switch to use, the best way to determine what brand of switch should relay on these factors:

Price

  • Performance (packets per second, fabric speed, buffer size, memory)
  • Feature sets (some manufacturers charge per feature, others sell switches fully loaded)
  • Mean Time Before Failure (often overlooked but VERY important include all components when looking at these)
  • Warranty availability and pricing over the expected life Support

    Do not assume that any one brand is better than another based on name alone.

    You can also try installing something like SNMPc (available from CastleRock Computing) and/or products that contain RMON features to determine application throughput speeds. When you look at your packets sent, also look for errors, discards and unknown protocols.

    Lastly, check to be sure that you don't have extra protocols loaded on your workstations, servers, and print servers. Every protocol that is active means that you will transmit packets for each.

  • This was first published in April 2004

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