Re: TCP RDMA option to accelerate NFS, CIFS, SCSI, etc.

[julian_satran@il.ibm.com]

That is not completely accurate. You will need appreciably more silicon to
do what you suggest.   And you can do it only with information that "passes
through the protocol" .
The good thing about the  proposal is that it can TAG whatever the
application wants (and that can be several layers away from the protocol).
You can't "page-flip" to buffers that you are not aware of. And page
flipping wherever is applicable assumes  also page boundaries for buffers.

Julo

Julian Satran - IBM Research



Vernon Schryver <vjs@calcite.rhyolite.com> on 25/02/2000 04:23:47

Please respond to Vernon Schryver <vjs@calcite.rhyolite.com>

To:   ips@ece.cmu.edu, tcp-impl@grc.nasa.gov
cc:    (bcc: Julian Satran/Haifa/IBM)
Subject:  Re: TCP RDMA option to accelerate NFS, CIFS, SCSI, etc.




> From: Erik Nordmark <Erik.Nordmark@Eng.Sun.COM>

> > A draft describing the TCP RDMA option can be found at:
> > ftp://ftpeng.cisco.com/pub/rdma/draft-csapuntz-tcprdma-00.txt
>
> There is no DNS entry for ftpeng.cisco.com so I can't access the
document.

ftpeng.cisco.com resolves for me to 198.92.30.33, and the URL works
ftpeng.cisco.com does not answer ICMP Echo-Requests.  It also seems that
Cisco is filtering ICMP TTL Exceeded.

Oh, well.  I predict that soon traceroute and ping will be as
effective as if the Internet were run by the old line telco managers
who went great lengths to keep their technical problems quite.
The recent security hassles will be a handy (and quite silly)
excuse.  (Yes, of course, Cisco has every right to filter however
they want.  I'm talking about technical sense, not rights.)


I'm even less impressed about the proposal than Erik Nordmark,
perhaps because more than 10 years ago I saw systems shipped by
more than one competitor of Sun Microsystems that paged flipped
NFS/UDP and user TCP data.  (well, one of the other vendors might
have been a little more recent 10 years.)

The motive for the proposal seems to be that while only a very few
CPU instructions are needed to page flip, the functions of those CPU
instructions are very hard in hardware.  I don't agree.  In today's
world of ASIC's, silicon to figure out where to drop incoming TCP
segments or NFS/UDP/IP fragments based only on old fashioned TCP and
RPC/XRD/UDP headers is nothing to write home about.  It wasn't even
all that big a deal more than 10 years ago, as everyone involved with
or who watched Protocol Engines Inc. remembers.

Hashing is almost as cool (and easy) in hardware as in software.


Vernon Schryver    vjs@rhyolite.com