On Mon, 22 Jan 2001, Val Henson wrote:
> Date: Mon, 22 Jan 2001 12:37:07 -0700
> From: Val Henson <email@example.com>
> To: David Lang <firstname.lastname@example.org>
> Cc: email@example.com, Linus Torvalds <firstname.lastname@example.org>
> Subject: Re: Is sendfile all that sexy?
> On Mon, Jan 22, 2001 at 10:27:58AM -0800, David Lang wrote:
> > On Mon, 22 Jan 2001, Val Henson wrote:
> > > There is a use for an optimized socket->socket transfer - proxying
> > > high speed TCP connections. It would be exciting if the zerocopy
> > > networking framework led to a decent socket->socket transfer.
> > if you are proxying connextions you should really be looking at what data
> > you pass through your proxy.
> > now replay proxying with routing and I would agree with you (but I'll bet
> > this is handled in the kernel IP stack anyway)
> Well, there is a (real-world) case where your TCP proxy doesn't want
> to look at the data and you can't use IP forwarding. If you have TCP
> connections between networks that have very different MTU's, using IP
> forwarding will result in tiny packets on the large MTU networks.
> So who cares? Some machines, notably Crays and NEC's, have a severely
> rate-limited network stack and can only transmit up to about 3500
> packets per second. That's 40 Mbps on a 1500 byte MTU network, but
> greater than line speed on HIPPI (65280 MTU, 800 Mbps).
> So, for a rate-limited network stack on a HIPPI network, the best way
> to talk to a machine on a gigabit ethernet network is through a TCP
> proxy which just doesn't care about the data going through it. Hence
> my interest in socket->socket sendfile().
> I'll admit this is an odd corner case which isn't important enough to
> justify socket->socket sendfile() on its own. But this odd corner
> case did make enough money to pay my salary for years to come. :)
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