RE: FW: [PCN] RE: draft-babiarz-pcn-3sm-00 pseudocode nit
"Jozef Babiarz" <babiarz@nortel.com> Wed, 05 September 2007 13:25 UTC
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Subject: RE: FW: [PCN] RE: draft-babiarz-pcn-3sm-00 pseudocode nit
Date: Wed, 05 Sep 2007 09:25:10 -0400
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From: Jozef Babiarz <babiarz@nortel.com>
To: bob.briscoe@bt.com
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Bob, No problem, added the one line to S.2.2.2 TB.fill = 0; // BB: Suggested amendment Regards, Joe email:babiarz@nortel.com Telephone:613-763-6098 -----Original Message----- From: Bob Briscoe [mailto:rbriscoe@jungle.bt.co.uk] Sent: September 4, 2007 4:18 PM To: Babiarz, Jozef (CAR:0S03) Cc: PCN IETF list Subject: Re: FW: [PCN] RE: draft-babiarz-pcn-3sm-00 pseudocode nit Joe, OK, I understand the desire to reduce the no. of instructions, and that this accuracy isn't deadly important. But it's in the smaller branch and the less typically used branch of the two anyway. So it doesn't reduce the max intructions per packet, nor even the typical instructions per packet. It only saves one instruction for a packet arriving in one fairly rare case. It just gives a TB with a depth that isn't predictable - instead the depth is approximately the same but the exact depth experienced depends on the history of previously arrived packets. Larger packets tend to see a TB with slightly less depth (probabilistically) than smaller ones, because whenever a larger packet arrives at a bucket with fill less than the packet's size, it invokes this approximate code, while a smaller packet won't, necessarily. I doubt there's a huge problem doing that. The only problem I can think of is it will be less easy to verify experimentally against an analytical model of the bucket. As I said, a nit that we don't really need to talk about at the IETF - I wouldn't expect us to have to standardise whether or not this happens! [PS - tho my jungle mail @ seems OK now, I'll look into why it bounced - let me know if you get a bounce again.] Bob At 17:23 04/09/2007, Jozef Babiarz wrote: >Bob, I'm forwarding you this email as I got a bounce from >rbriscoe@jungle.bt.co.uk > >Regards, Joe >email:babiarz@nortel.com >Telephone:613-763-6098 > >-----Original Message----- >From: Babiarz, Jozef (CAR:0S03) >Sent: September 4, 2007 12:17 PM >To: Bob Briscoe >Cc: pcn@ietf.org >Subject: [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 > > > > >_______________________________________________ >PCN mailing list >PCN@ietf.org >https://www1.ietf.org/mailman/listinfo/pcn ________________________________________________________________________ ____ Bob Briscoe, <bob.briscoe@bt.com> Networks Research Centre, BT Research B54/77 Adastral Park,Martlesham Heath,Ipswich,IP5 3RE,UK. +44 1473 645196 _______________________________________________ PCN mailing list PCN@ietf.org https://www1.ietf.org/mailman/listinfo/pcn
- [PCN] draft-babiarz-pcn-3sm-00 pseudocode nit Bob Briscoe
- [PCN] RE: draft-babiarz-pcn-3sm-00 pseudocode nit Jozef Babiarz
- RE: FW: [PCN] RE: draft-babiarz-pcn-3sm-00 pseudo… Jozef Babiarz