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RE: [EFM] Minutes of P2MP Optics conference 22nd Aug 20002


This is to address action item #2 from the minutes.

2. Efficiency model based on guard bands and traffic type - P2MP group?

There are 3 types of overhead (or bandwidth loss):

1. Cycle overhead. This is overhead used by guard bands (including CDR).
It is measured as a number of guard bands in one cycle. This number at
least equal to the number of ONUs, but may be even larger if we grant
per LLID and there are multiple LLIDs per ONU. 

2. Slot overhead.  This overhead arises when granted slot does not take
into account frame delineation in a buffer. Since frames cannot be
fragmented, a frame that doesn't fit in the remainder of a slot will be
deferred to next slot (in next cycle), leaving current slot

The size of unused slot remainder depends on frame size distribution.
This distribution for today's traffic is known and there exist formula
to calculate this unused remainder (for the case when assigned slot size
has no correlation to the frame sizes). 

Few protocol proposals consider how to eliminate unused slot remainder
completely, but it looks like it will require changes to the frame
format.  P2MP group is still debating about it.

3. Frame overhead.  That includes IFG and headers. Nothing we can do
about it.


> -----Original Message-----
> From:
> efm@xxxxxxxxxxxxxxxxxx] On Behalf Of Thomas.Murphy@xxxxxxxxxxxx
> Sent: Friday, August 23, 2002 1:57 AM
> To:
> Subject: [EFM] Minutes of P2MP Optics conference 22nd Aug 20002
> Hello All,
> First off I apologise for sending this mail to the
> EFM reflector, however, a number of issues arose which
> are relevant for other groups.
> The next phone conference is planned for next Thursday
> at the old time of 11:00 Eastern
> Regards
> Tom