RE: (no subject)

Hi Barry,

FPDU alignment is a property of the TCP segment where the first byte of the FPDU follows the TCP header.  A valid FPDU CRC, however, does not guarantee FPDU alignment.  Thus, turning CRCs off is orthogonal to turning markers off.

If markers are disabled, an MPA receiver can only determine the start of the next FPDU from the length of the previous FPDU.  If a TCP segment is received out of order, the MPA receiver would have to buffer the segment until the gap is filled. 

--jc

> -----Original Message-----
> From: [email protected] [mailto:[email protected]]On 
> Behalf Of Barry
> Reinhold
> Sent: Thursday, April 08, 2004 7:42 AM
> To: RDDP
> Subject: [rddp] (no subject)
> 
> 
> How would you expect a MPA receiver to handle an out of order TCP
> segment with markers disabled and CRC off? Does it just 
> buffer it until
> the gap is filled?

> 
> Also, if CRCs are enabled and we are processing an out of order PDU
> without markers, what is the behavioral expectation of a failed CRC
> check? A matched CRC would be sufficient to determine FPDU alignment,
> but a failed CRC appears only to say that you may not have FPDU
> alignment. 
> 
> That is, if I created a test that produced a gap in the TCP 
> sequence and
> then sent an unaligned FPDU within a TCP segment, followed by the
> missing information I would expect the receiver to: (1) Not drop the
> connection, (2) Advance the ACK through the unaligned segment when the
> missing information was sent.
> 
> Is this the correct understanding?
> 
> Barry Reinhold
> Lamprey Networks
> [email protected]
> (603) 868-8411
>  
> 
> 
> 
> 
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