100BT Performance

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I want to know how many packet 100BT card can handle.

[Bill Hassell · Accepted solution]

The answer is quite difficult to answer as it depends on the speed and loading of your computer, the type of LAN card (specifically the type of bus the LAN card uses) and the ability of the network hardware to process the packets. Throughput on a LAN is usually measured in bytes per second rather than packet count since very small packets (ie, 10 bytes) will have very high percentage of overhead.

In theory, 100 megabits can probably approach 7-9 megabytes/sec but some versions of the LAN card will never get past 2-3 megabytes/sec. Throughput significantly below this level is usually fue to overloaded LAN segments or cards that are setup with auto-negotiation. Always fix the communication rate on both the computger side as well as the hub to avoid problems.

Halfduplex will not improve the throughput except in cases where true simultaneous communication is the majority of usage, and on a slow computer, it can sometimes reduce throughput a bit.

[Berlene Herren]

You can also get a look at performance for the 100BaseT card from

http://www.netperf.org.

Berlene

[rick jones]

100Base-T the _technology_ has a maximum packet per second limit based on the packet size, the bitrate (100 megabits) and the inter-packet spacing.

As far as a 100Base-T NIC goes, that will vary with the NIC. As others point-out, some NICs are better than others. For instance, the HP PCI 100BT NICs are leaps and bounds ahead of the HP-PB NICs.

Another factor will be the stack and driver path lengths and the CPU horsepower of the system. An N Class will be able to drive a higher number of 64-byte packets through a 100BT NIC than a K.

The actual packet per second at any packet size will be the _minimum_ of these possible limiters.

You can use netperf tests to try and guage some of these limits. One test would be the UDP_STREAM test, though it has issues with its lack of flow control. Another test would be the TCP_RR test with single-byte requests. If you run several in parallel you can try to max-out a NIC/ that way. There is also the TCP_STREAM test with the -D option to disable the Nagle algorithm.

More info about netperf can be had at http://www.netperf.org/ including instructions on how to join the netperf-talk mailing list.

Finally, by now, there should be a couple whitepapers talking about NIC performance at http://docs.hp.com/