North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

RE: Traffic Shape or Rate Limit

  • From: Alexander Kiwerski
  • Date: Tue Oct 02 17:04:29 2001

Alex Bligh was alleged to have written:

>But if you don't want burst - you appear to just want
>to simulate a fractional DS-3 - why don't you just set
>the relevant number of timeslots to be used either
>end? This works well. And guarantees no complications.

If your trying to test with a-typical real-world parameters,
wouldn't it be prefereable to also test utilizing a clear
channel pipe with a rate-limited/policed PVC defined?  My
experience has been that most carriers don't like to deliver
channelized DS-3's, instead they throw out a clear-channel
loop, aggregate it into their ATM network, drag it to their
router etc, then define an ATM PVC across it to the rate agreed 
upon to do the "fractionalizing". (I suspect this has something
to do with the fact that Channelized cards for their switches
tend to be bit more expensive and less cost effective for Frac
DS-3 usage?)

In the ATM-based Frac DS-3 scenario, you're doing rate-limiting
by default as you must define the PVC to the bandwidth that you
are selling to your customer. (typically at your ATM switch with
matching rate queues on your router as well).  Perhaps shaping
would come in handy however to optimize/prioritize particular types
of traffic for your customer(s).

All in all, IMHO, I think you really have to consider how you 
are aggregating your customers to your network, and how policing 
or shaping will play into/against that.  If you're aggregating
via an ATM switch into your router(s), it becomes a different
ball game from terminating individual clear channel or even
channelized pipes directly to your router(s).  I do agree though,
if it agrees with your network/aggregation design, shaping is
much nicer.

/Alex Kiwerski