RE: DDP segment sequences for Untagged DDP message

Below...

Paul R. Culley
HP Fellow
281-514-5543


-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Barry Reinhold
Sent: Friday, January 16, 2004 1:09 PM
To: RDDP
Subject: [rddp] DDP segment sequences for Untagged DDP message



So, is there agreement, for the sequences that follow, that the
specified "result" given below is the correct (and desired?) behavior as
defined by the 01 draft.

Untagged DDP Segment Sequences:

1. QN = 0, MSN = 1, MO = 100 L = 1 Payload = 100 bytes
2. QN = 0, MSN = 1, MO = 0   L = 0 Payload = 100 bytes
Result: DDP Message (bytes 0-200) is delivered to ULP
[prc] yes

1. QN = 0, MSN = 1, MO = 100, L = 0, Payload = 100 bytes
2. QN = 0, MSN = 1, MO = 0,   L = 1, Payload = 100 bytes
Result: ULP sent Error type=Untagged Buffer Error, Error Code=Invalid MO
[prc] No, the receiver will place both segments, but inform the ULP that
only 100 bytes was delivered, ending at MO=99.  No error should be
detected or reported, unless the receiver's buffer was not large enough
to hold the second 100 bytes.

1. QN = 0, MSN = 1, MO = 0, L = 0, Payload = 100 bytes
2. QN = 0, MSN = 1, MO = 0, L = 1, Payload = 100 bytes
Result: DDP Message (bytes 0-100) is delivered to ULP
[prc] yes, but it is not certain which segment ends up in the buffer, it
won't matter unless the two payloads are different.

1. QN = 0, MSN = 1, MO = 000, L = 0, Payload = 100 bytes
2. QN = 0, MSN = 1, MO = 200, L = 1, Payload = 100 bytes
Result: DDP Message (bytes 0-300) is delivered to ULP
[prc] yes, but the middle 100 will contain unknown values (probably what
they had before the buffer went through DDP).

1. QN = 0, MSN = 1, MO = 300, L = 1, Payload = 100 bytes
Result: DDP Message (bytes 0-400) is delivered to ULP
(This is based on wording in 6.3, MO field. Note that the second
sentence simply says that the MO "that references the first octet MUST
be set to zero", not that a segment having a zero MO is required)
[prc] yes, but first 300 is unknown

1. QN = 0, MSN = 1, MO = 100, L = 0, Payload = 100 bytes
2. QN = 0, MSN = 1, MO = 000, L = 1, Payload = 0 bytes
Result: ULP sent Error type=Untagged Buffer Error, Error Code = Invalid
MO (There is ambiguity between 6.1 L bit field description ( Segment w/
L bit set must have highest MO), and 9.1 (implies that for non-zero
length segments the header fields are not validated.)
[prc] no, at least not because of a protocol error.  There is only an
error if the buffer limits as defined by the ULP is exceeded.  You
should get an indication that a zero length message was delivered.

1. QN = 0, MSN = 1, MO = 000, L = 0, Payload = 100 bytes
2. QN = 0, MSN = 1, MO = 100, L = 1, Payload = 0 bytes
Result: DDP Message (bytes 0 - 100) is delivered to ULP
[prc] yes

1. QN = 0, MSN = 1, MO = 100, L = 1, Payload = 0 bytes
Result: DDP Message (bytes 0 - 100) id delivered to ULP. 
[prc], yes, but with unknown data values.

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



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