Re: [HSSG] 40G MAC Rate Discussion
There are no form factors from Multi-Sourcing Agreements (MSAs) that
currently support 100 gigabit data rates. This means that any 100 Gb/s
transceiver are single source solutions or proprietary.
The X40 and QSFP are designed to support 4 bidirectional lanes to 10
Gbps/lane. The electrical connector on modules does not support 25
Gbps. These are the only multi-sourced, pluggable interfaces that could
be enhanced to support 4X25 Gbps. I was the main proponent of increasing
the data rate of the QSFP from 5 Gbps to 10 Gbps and the group did not
want to increase the speed because of power dissipation problems when
running at 10 Gbps.
Two other options for non-proprietary, non-pluggable solutions are the
SNAP-12 which runs 12 lanes at a maximum of 2.72 Gbps/lane (32 Gbps
aggregate) or the 300-pin MSA that runs 16 channels to 2.5 Gbps/lane (40
Gbps aggregate). Picolight has shown how they have overclocked the
SNAP-12 MSA to 10 Gbps/lane to achieve 120 Gig (100 Gig with 8B/10B
"Standardized" transceivers max out at 40 Gbps and would need to be
redesigned to increase the data rates to 100 Gig. Increasing the data
rates beyond their original design may be a fairly arduous journey and
completely new designs are often needed. The best example of this is
the SFP transceiver that was originally designed to run up to 5 Gbps.
The Improved Pluggable Form Factor (IPF) and SFP+ standards to replace
the SFP increase the data rate to 10 Gbps and have been worked on for a
couple of years. This task is now months away from completion to
achieve 10 Gbps data rates in the latest and greatest IPF form factor
with a single lane.
The general consensus that I have heard from the group is that 100 Gbps
solutions for multimode distances will be of the 10X10 Gbps variety.
The electrical connector on such a solution will probably require 4
pins/lane (2 bidirectional differential pairs) so 40 pins. This results
in a fairly large connector when the other pins are added. When
considering the power dissipation requirements for these modules, the
size must increase substantially to avoid exotic cooling techniques. One
prototype that I have seen for 10X10 Gbps is a over 3" by 3". With a
fiber ribbon as the optical interface, using tweezers because of high
port density will not be the problem.
I hope that helps and someone please correct me if I have missed an MSA
that supports 100 Gig.
From: Peter Harrison [mailto:pharrison@NETFLIX.COM]
Sent: Monday, April 09, 2007 9:30 PM
Subject: Re: [HSSG] 40G MAC Rate Discussion
The threads have mentioned a number of form factors for connectors
including, X40, X2, QSFP to name a few. Are these finalized or just
I'm interested because of port density opportunities on both stackable
and chassis based switches.
Mix and match 10/100G combo blades for example, not in the 10/100/1000
sense where a single port acts as a jack of all trades, but 10G and 100G
bundles of ports with varying port counts. That way I could have more
flexibility with my over-subscription rates and costs plus, in some
cases, uplink redundancy. As always smaller is better (as long as I
don't have to use tweezers).
100 Winchester Circle, Los Gatos, CA 95032