From:
OJHA,JUGNU [mailto:jugnu.ojha@xxxxxxxxxxxxx]
Sent: Monday, August 14, 2006 6:07
PM
To: Trowbridge, Stephen J (Steve)
Cc:
STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: RE: [HSSG] MAC Data Rate
of Operation Objective
Steve,
Many of your questions are answered in
messages just exchanged between Geoff Thompson and me. To address some of
the others:
A multi-hop solution without
realignment/reassembly sounds difficult, if not impossible:
1) How would intermediate nodes read the
destination MAC address?
2) The inter-channel skew would be
effectively unbounded.
The question of what channel rates higher
than 10G to use is related to the question of mixing and matching lanes of
differing speeds. For starters, I think we should apply some judgment on
the latter issue – i.e., would anyone really want to mix 10G and 1G lanes
to build a really fat pipe? If we’re talking about a pipe of 20-100
G or more, do additional 1G increments really add any value? Regarding
lane speeds higher than 10G, the question becomes, “Can we define
aggregation of lanes whose speeds are as yet unknown, or do we have to make a
decision today on speeds (and hence, technologies) that don’t exist
yet?” Do we use 25G, 33.3G, 40G, 50G? This future-gazing is a
tricky business.
Best wishes,
Jugnu
From: Trowbridge,
Stephen J (Steve) [mailto:sjtrowbridge@xxxxxxxxxx]
Sent: Monday, August 14, 2006 3:23
PM
To:
STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [HSSG] MAC Data Rate
of Operation Objective
John,
In some respects, I think that (A) and (B)
in your description might be good candidates to tackle in separate projects
(PARs).
Let me comment on proposal (B) first:
I would characterize this as a study of
"Multiple Lane Approaches". Here, there are a number of questions to
be answered:
1) Is the number of "lanes"
fixed or variable?
2) Can the interface operate at
reduced bandwidth in the presence of failure of individual lanes?
3) What is the network architecture
governing the multi-lane interconnection? Are multiple lanes carried over a
single span only, or can the lanes be carried independently across a network
and only reaggregated at the endpoints? (attractive feature here: not necessary
to build the new interface on every network element along a path between
ultra-high rate endpoints to provide an ultra-high rate service. Network
elements transporting individual lanes can be blissfully unaware that that lane
is part of a larger aggregate). This network architecture has an impact on the
differential delay that may need to be accommodated across the lanes when they
are re-aggregated.
4) Are the individual lanes carried over
existing or new physical interfaces?
5) Can we learn from or reuse the
capabilities from ITU-T Virtual Concatenation and LCAS to provide this kind of
physical layer aggregation?
Back to proposal (A), I think that even
those of us who think that (B) is an important problem to solve do not believe
that 10G is the highest rate we will ever have for serial transport. So the way
I would like to see (A) approached is to study what the next potential serial
interface rate above 10G should be and what its characteristics are. Here, we
could study 100G, 40G or other rates that provide a suitable evolution and are
supported by the technology.
40G has some attractive
characteristics since it could reuse components from transport interfaces
at the same rate (SONET OC-768, SDH STM-256, or OTN OTU-3). Note that in one
sense, we already have WAN PHY type interfaces at 40G if you consider Ethernet
frames mapped via GFP-F into SONET OC-768c, SDH VC4-256c, or OTN OPU3.
Of course even 40G is not the highest rate
interface that we will ever build, so even if 40G is considered to be an
evolutionary step along the path of increasing bandwidth, it is worth studying
what the next serial rate should be above 40G.
Regards,
Steve
From: John
DAmbrosia [mailto:jdambrosia@xxxxxxxxxxxxxxxxxxx]
Sent: Monday, August 14, 2006 3:20
PM
To:
STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: [HSSG] MAC Data Rate of
Operation Objective
All,
In regards to proposed MAC data rates, I have seen two basic
proposals
Proposal A) 100 Gb/s
Proposal B) Scalable Solution
Proposal A supports the traditional 10x increase in
speed.
Proposal B, as presently discussed, is unbounded. (The
following are only my observations of statements made on the reflector by
others) The lowest limit proposed was a 4x10 approach for 40 Gb/s.
No upper limits have been proposed. It has been suggested that this
approach should use existing PMDs, but there have been also been comments
regarding use of 10G, 25G, and 40G lambdas, but that carriers would want to leverage
their existing DWDM layer, which mean baudrate in the 9.95-12.5 Gig. Consuming
wavelengths has been brought up as a possible concern. It was also
suggested that the greatest bandwidth demands are on VSR links < 50m and
that the longer reach (>10km) may be able to live with 4x10G. (Data in
support of these observations that could be used to guide the creation of
objectives would be welcome.)
An objective for Proposal A could be similar to what was
done for 10 GbE– Support a speed of 100.000 Gb/s at the MAC/PLS service
interface.
For Proposal B, given its current unbounded nature and
multiple discussion points, I am not sure what would be proposed. I am
looking to the advocates of this proposal to provide some verbiage to the
reflector for discussion. Using the objective above as a basis: Support a
speed greater than 10.000 Gb/s at the MAC/PLS service interface, would create
too broad an objective.
Also for both proposals what are people’s thoughts on
an objective that would specify an optional Media Independent Interface (MII)?
John