Shady areas of TCP window autotuning?

Brett Frankenberger rbf+nanog at
Tue Mar 17 13:21:01 UTC 2009

On Mon, Mar 16, 2009 at 10:48:42PM -0500, Frank Bulk - wrote:
> It was my understanding that (most) cable modems are L2 devices -- how it is
> that they have a buffer, other than what the network processor needs to
> switch it?

The Ethernet is typically faster than the upstream cable channel.  So
it needs some place to put the data that arrives from the Ethernet port
until it gets sent upstream.

This has nothing to do with layer 2 / layer 3.  Any device connecting
between media of different speeds (or connecting more than two ports --
creating the possibility of contention) would need some amount of

     -- Brett

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