Subject: [rddp] Conformance Question

From: "Barry Reinhold" <[email-masked]>
Date: Fri, 12 Nov 2004 17:43:25 -0500

Working on an interoperability issue related to section 3.6.1.1 (CRC bit
paragraph) of MPA, which states:

This bit (CRC bit) declares an endpoint's preferred CRC usage. When this
field is '0' in the "MPA Request Frame" and the "MPA Reply Frame", CRCs
MUST not be checked and need not be generated by either endpoint. When
this bit is '1' in either the "MPA Request Frame" or "MPA Reply Frame",
CRCs MUST be generated and checked by both endpoints.

The question:

If an MPA request frame has set the CRC bit to 1, can the MPA replay
frame's CRC bit be set to 0 without violating the draft.

>From a strict reading of the draft there does not seem to be a
requirement that a "1" in the request results in a "1" in the reply,
only that both devices must use CRCs.

So is the meaning of a "0" in the reply frame "I'm not using CRCs, or is
it I didn't want to use CRCs". Further if the requester sees a 0 in the
reply frame after setting the CRC bit to 1 in the request frame should
it reset the connection?

Barry Reinhold
Lamprey Networks
[email-masked]
(603) 868-8411

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From: "Barry Reinhold" <[email-masked]>
Date: Mon, 15 Nov 2004 11:19:46 -0500

Ok,
	I think I am hearing that the consensus of the group is that a
conformant MPA device SHALL NOT reset a TCP connection if it receives a
MPA Startup Reply frame in which the CRC bit is 0 when it sent out a MPA
Startup Request frame with the bit set to 1.

Any objections to this understanding?

Barry Reinhold
Lamprey Networks
[email-masked]
(603) 868-8411

---

From: "Jim Pinkerton" <[email-masked]>
Date: Mon, 15 Nov 2004 21:34:08 -0800

I agree with the summary, but am concerned on re-reading the text.

I'd suggest a couple of minor changes for clarity:

I would recommend we clarify some text elsewhere in the document.
Specifically section 5.2 CRC Calculation. The text that states 

   "(2) only negotiate the non-use of CRC on the explicit request of the
..."

We change to "only attempt to negotiate..."

And a little after this, also in section 5.2 states:

   "If an MPA instance has
   declared that it does not require CRCs, it MUST turn off CRC checking
   immediately after receipt of an MPA mode declaration indicating that
   its peer also does not require CRCs."

Should be changed to say (note that MPA mode declaration is not a
defined term in the spec):

"If an MPA stream has successfully negotiated during the MPA Startup
Phase (see section 6) for CRCs to not be enabled, it MUST turn off CRC
checking immediately after receipt of the first (and only) MPA Startup
Phase Message." 

Jim

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On Behalf
Of
> Barry Reinhold
> Sent: Monday, November 15, 2004 8:20 AM
> To: RDDP
> Subject: [rddp] RE: Conformance Question
> 
> Ok,