[PCN] RE: draft-babiarz-pcn-3sm-00 pseudocode nit

Bob, 
We selected this approach to reduce the number of instructions.
Our original rational was, since the pseudo-code in the "if" statement
does not subtract packet.size there is no need to set TB.fill = 0. We
believe there would be no meaningful difference between leaving the TB
at TB.fill versus empty since the TB is less than the size of the packet
from being empty and we are doing threshold marking. We also assumed
that TB.threshold is several times larger than the size of the largest
packet. 

Let us know if you disagree and we can add TB.fill = 0; line to the
example pseudo-code.

Regards, Joe
email:babiarz@nortel.com
Telephone:613-763-6098
-----Original Message-----
From: Bob Briscoe [mailto:rbriscoe@jungle.bt.co.uk] 
Sent: August 30, 2007 4:11 AM
To: Babiarz, Jozef (CAR:0S03)
Cc: pcn@ietf.org
Subject: draft-babiarz-pcn-3sm-00 pseudocode nit

Joe,

In the admission marking pseudo-code in draft-babiarz-pcn-3sm-00
S.2.2.2, 
if a packet arrives that is larger than the current depth of the token 
bucket, you correctly mark the packet with admission stop marking, but I

think you've omitted to empty the bucket to zero as well.

/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
      if (TB.fill < packet.size)
          TB.fill = 0;           // BB: Suggested amendment
          packet.mark = AS;
      else
          TB.fill = TB.fill - packet.size;
          if (TB.fill < TB.threshold)
              packet.mark = AS;
          endif
      endif
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

Bob

________________________________________________________________________
____
Bob Briscoe, <bob.briscoe@bt.com>      Networks Research Centre, BT
Research
B54/77 Adastral Park,Martlesham Heath,Ipswich,IP5 3RE,UK.    +44 1473
645196 

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