Re: maximum Ethernet throughput

Brian Thomson (mnetor!utzoo!utgpu!utcsri!me!oldhub!
17 Mar 88 03:48:09 GMT

Van Jacobson's results are certainly startling, but I can't help
believing that a significant part of that speedup must be in
changes to the mbuf handling, the socket code, and the LANCE
driver. My evidence is a test I ran on a 3/50: I defined a
'protocol' whose PRU_SEND action was to checksum each mbuf then
hand it directly to the driver, with a dummy AF_UNSPEC destination so
there would be no ARPing going on. This exercises vanilla
SUN mbuf, socket, and interface driver code, while replacing all
of TCP/IP by simple checksumming - so no protocols at all.
The data goes nowhere, and there are no acks to deal with.
Even so, this configuration could not source data to the wire faster
than about 3.6Mb/sec. I could hit 8Mb/sec if I threw the data
away right after checksumming, without passing it to the driver at all.

		    Brian Thomson,	    CSRI Univ. of Toronto

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