Re: [BP] Question regarding Channels
As a System Architect and Designer, I think before we spend overly much time
debating the characteristics of particular channels, we should first see if
we can agree on the problem we are trying to solve.
The group needs to be clear on the problem.
The ATCA market is projected to develop into a large and important market
and as such is of interest to 802.3ap members.
However, today and for the short to medium term future, ATCA is only a small
fraction of the Total Available Market.
The ATCA market will include both Existing (Legacy) and New (Greenfield)
products. Products of potential interest to 802.3ap include:
Line Cards
Switch Cards
Passive backplanes
Do we want 802.3ap to include auto-negotiation to allow support for existing
Gigabit Ethernet and XAUI Line Cards.
My Answer is YES.
Do we want 802.3ap to auto-negotiate to allow a future switch fabric card to
be built that supports existing Gigabit Ethernet Line Cards, XAUI Line Cards
and new 10 Gigabit Serial Line Cards
My Answer is YES.
Do we want to support 10 Gigabit Serial Links on Existing ATCA Backplanes
designed for 1 Gigabit or XAUI speeds.
My Answer is NO.
As a System Designer, I know that there are some parameters that I have
under my control and some I do not.
I have no control over the Mechanical outline, the Thermal Budget, or the
Power Budget for an ATCA card.
I have control over the Line Card and Backplane:
materials and construction
design and manufacturing practices
I desire an optimal solution for the constraints which I am unable to
change:
Space (must integrate between 10 & 100 links on a single ASIC)
Power (because thermal issues are my most severe constraint)
Could the 802.3ap Task Group spend its time seeking a 10 Gigabit Serial
signaling solution that will operate over existing Gigabit and XAUI
backplanes?
My Answer is Yes
Should the 802.3ap Task Group spend its time seeking a signaling solution
that will operate over existing Gigabit and XAUI backplanes?
My Answer is Absolutely NOT.
What should the Task Group be concerned with? In my opinion two things.
1) Developing an optimal signaling solution for those channels which
meet the criteria developed by the Channel Ad Hoc. These represent realistic
best practices for backplane construction. These channels do not
unnecessarily burden the potential solution with the power, cost and
complexity of legacy support.
2) Developing an Analytical Tool driven by S parameters, along the
lines of Stat-Eye which will allow the quantitative characterization of a
particular backplane as Complaint with 802.3ap 10 Gigabit Serial Signaling.
To aid the development of the market for 802.3ap 10 Gigabit Serial
Signaling, the most important thing is not burdening the standard with
legacy requirements. The most important thing is to provide a tool that will
allow systems designers to unequivocally know if an existing (or planned)
backplane will operate reliably at 10 gigabit serial rates.
Mike Lerer
Chief Architect Rapid Prototypes Inc.
Chairman Physical Link Layer Working Group of the Optical Internetworking
Forum
Chairman Hardware Working Group of the Network Processing Forum
Box 636 Londonderry, NH 03053
Cell: 603-548-3704