Subject: [rddp] Markers and software

From: [email-masked]
Date: Wed, 4 Dec 2002 23:46:15 -0500

WG chair hat off ...

> So clearly, the absence of markers imposes a *severe*
> penalty on RNICs optimized for alignment preserving
> environments. In contrast, markers are a nuisance, but they
> are far from an implementation-breaker for any option.

> 512B as Marker interval - keeps the wire overhead at about the
> same level TUF had it. At high data rates the receiver efficiency,
> reducing RCV memory bandwidth and size, is much more important.

Markers appear to be an implementation-breaker for software in
their current form, in contrast to the TUF framing additions.

> Again, pls note that CRC in SW place a high toll on SW. Adding
> markers is not the killer at this point

Uhmmm ... CRCs may want to be negotiable/selectable/optional
in some fashion, as NFSv4 does not need (REQUIRE) them, although
it may find them useful ...

> The vast majority of say 10GbE will be HW and SW will not keep up.

Even when fanning in a bunch of slower SW clients to a HW server??
In what sort of time frame?

WG chair hat on for the rest of this message ...

If the practical effect of MPA is to prohibit software
implementations, that's going to be a major obstacle to it
making progress.

> Adding options and sacrificing the no-negotiation-required
> at connection setup, seems a high price to pay.

To some extent I suspect that's driven by an orthogonal issue
- the onus is still on the advocates of MPA to provide adequate
assurances to satisfy the AD concern expressed in Atlanta that
two TCP implementations could get confused about whether the
traffic on the wire is framed or not.  The SCTP adaption exchange
(see draft-stewart-sctp-roi-00.txt) is something to which
whatever is or is not done in the TCP mapping will be
compared in evaluating whether it provides an adequate assurance.

Thanks,
--David

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David L. Black, Senior Technologist
EMC Corporation, 176 South St., Hopkinton, MA  01748
+1 (508) 293-7953 **NEW**     FAX: +1 (508) 293-7786
[email-masked]        Mobile: +1 (978) 394-7754
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