RE: Potential data corruption in DDP with MSN protocol violation

At 04:08 PM 4/26/2004, Shah, Hemal wrote:
>Barry,
>
>The receiver can detect this protocol error by keeping track of the next
>MSN to be delivered. So, while delivering MSN=3, it can identify a hole
>in the MSN. I agree with you that this case is not covered in the errors
>section.
>
>I would propose we add an error "Invalid MSN - gap in MSN" (type=0x2,
>code=0x00) for Untagged buffer errors.

Would the receiver then be required to check for such gaps?
Because I agree with Caitlin that nothing bad happens if such
a gap appears, except that the connection will grind to a halt
since MSN=3 cannot be delivered.

So, I think the error is merely informative, and not required for
correctness. Therefore it could be argued it is not needed.

Tom.

>
>Thoughts?
>
>Hemal 
>
>-----Original Message-----
>From: [email protected] [mailto:[email protected]] On Behalf Of
>Barry Reinhold
>Sent: Friday, April 23, 2004 12:41 PM
>To: RDDP
>Subject: [rddp] Potential data corruption in DDP with MSN protocol
>violation
>
>Based on the current wording in ddp draft 02, clause 9 it appears that a
>receiver can place and deliver a sequence of DDP messages that arrive
>with sequence number MSN=1, MSN=3, MSN=4 if there is no gap in the LLP
>stream sequence. This could only be generated by a protocol error on the
>transmitting side. 
>However, if the transmitter did indeed generate this sequence
>incorrectly it is conceivable that the receiver would have old data in a
>buffer associated with MSN=2 and deliver it to the ULP.
>
>Although one does not in general like to have the receiver check for
>protocol errors, this may be an area in which the wording of the
>standard should be strengthened a bit, such that DDP messages can not be
>delivered when there are holes in the MSN space.
>
>Barry Reinhold
>Lamprey Networks
>[email protected]
>(603) 868-8411
> 
>
>
>
>
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