Subject: Service disciplines for RSVP 7/08/95 7/10/95 21:57:28

From: "Roch Guerin ((914) 784-7038)" <[email-masked]>
Date: Tue, 11 Jul 95 07:00:52 EDT

Reference:  Your note of Mon, 10 Jul 1995 21:57:28 PDT

>did you also looked at the buffer occupancy issue?  i.e. would
>work-conserving rate-control cause downstream nodes more buffer space
>that the non-work conserving version?

Yeap, as has been pointed out by several previous works, there is
unfortunately a price to pay in terms of buffer space (no free lunch).
It's essentially because letting things out early at one node allows
a "worse" arrivals pattern at downstream nodes.  That's not a problem
if these nodes are themselves not congested, but you can create scenarios
with several "worsened" flows converging onto one bottleneck link where
the buffering needed will then be higher.
On the other hand, letting packets out early may also help overall
network operation as packets altogether
get out of the network earlier, which makes the buffer space
they would have occupied available to other packets.  Typically, this
is, however, a less significant effect.

Roch

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From: Steve Jackowski <[email-masked]>
Date: Tue, 11 Jul 1995 08:14:29 -0900 (PDT)

Roch,

We've been working with pure rate control implementations 
both in our NQSS product and in Starlight's MTP (an XTP 
derivative).  

> is, however, a less significant effect.
I know that many of the powers that be in the IETF seem to 
think that jitter is not important if there is controlled 
delay, but...

Have you examined the effects on end-to-end jitter?  It 
seems that variation in the scheduling of packets with 
additional buffering required along the path will 
significantly impact jitter when network loads vary.  Any 
thoughts?

Steve