From: Edwards, Andrew M (andrew.m.edwards@boeing.com)
Date: Mon Feb 16 2004 - 19:17:51 GMT-3
Alright,
I have looked through the IPexpert slide show discussion, read solie PS
I, Caslow 2nd Ed., and even looked on CCO but I'm seeing what appear to
be inconsistencies on the way FRTS is explained, particularly Be... and
also implementing FRTS successfully by interpreting the given
requirements.
So I have a 2 part question....
First, how does Be relate to the interval? Specifically, here is how I
have seen it explained:
- I have seen Be operation discussed as Bc tokens depleted in the
interval then the router can use up to Be tokens within the current
interval. After that, no more Be can be sent during remainder of ALL
intervals for the bit rate period. IOW, Be tokens are depleted over the
ENTIRE BIT RATE PERIOD, not per interval.
- I have also seen Be operation discussed as Bc tokens depleted in the
interval then the router can use up to Be tokens within the interval.
After that, Be tokens are replenished for the next interval. This
behavior occurs over ALL intervals for the bit rate period. IOW, Bc
token settings are valid per interval.
Can someone please expound upon which one it is?
The second question relates to recommended methodologies to 'interpret
FRTS requirements'. I will use the following 2 simplified examples of
how to interpret requirements, the first is my understanding (looking
for confirmation from peers) and the second is looking for how my peers
would interpret these requirements.
First -
My understanding is that by definition of Bc and Be being per interval,
it would seem that they are tokens being replaced per interval over the
bit rate period. Thus, a simple frame relay R1 @ 128Kbps circuit
guaranteed at 64kbps to R2 @ 64kbps circuit guaranteed to 32kbps would
be:
R1: CIR=128000, Bc=8000, Be = 8000, mincir = 64000, adaptive BECN
R2: CIR=64000, Bc=8000, Be=0, mincir=32000, adaptive BECN
Is this correct?
Second -
If I have a hub and spoke FR topology, R1 is hub, R2/R3 are spokes. R1
has serial interface that operates at 1.544Mbps to provider. R2 is
serial interface with 64Kbps to provider and R3 is serial interface with
128Kbps to provider. I know that I have a committed information rate
from the provider on R2 at 32kbps and R3 at 64kbps.
How would I go about setting up FRTS at R1 to ensure I do not exceed
remote or local settings? Or, suffice to say, would I need more
information about R1s provider CIR?
Any thoughts or additional links are appreciated.
andy
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