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Re: Interface reality check


We're getting much closer. I have comments in the following areas:

Code Space

We seem to agree on reserving some code space for future use.

Supporting Fibre Channel in IEEE 802.3ae is not relevant. However, it is
impossible the overwhelmingly strong market acceptance of gigabit interconnects,
the exponentially growing demand for data transport, and the magical convergence
speed of ~10 Gbps for the LAN, MAN/WAN and SAN. 

IEEE 802.3ae has decided that addressing MAN/WAN applications is in its best
interest. WAN support is written into our PAR and included in our objectives. It
is clear that supporting the MAN/WAN means supporting SONET directly to some,
simply providing Ethernet access to the MAN/WAN to others, and building out all
Ethernet MAN/WANs to still others. I believe that either the IEEE 802.3ae or
vendors are just going to bet on one of the three MAN/WAN support scenarios. My
own analysis of the strategies and product lines of large companies such as
Cisco and Nortel as well as VC investments in the past few years clearly show
the billions of dollars are being poured into all three. Getting back to code
space, I believe that 10 GbE needs to be architected in a flexible enough manner
to support MAN/WAN directions.

The Storage Area Network business and applications have been hard to ignore in
1999 and momentum is still growing. Fibre Channel has already endorsed a roadmap
which includes 10 Gbps and 40 Gbps interfaces for the SAN on a timeline in sync
with MAN/WAN timelines. Many SAN applications also require MAN/WAN connectivity
for applications such as remote backup, disaster recovery, and storage sharing
between remote corporate sites. Some Ethernet vendors have also been eyeing the
SAN space as a huge and easy business opportunity to put under their wing. Once
again, the direction is clear: SANs are here to stay. Getting back to code space
again, I believe that 10 GbE needs to be architected in a flexible enough manner
to support SAN directions.

All these 10 Gbps LAN, MAN/WAN and SAN links need to be sourced somewhere. Enter
the server, whether it be a low-cost high volume or mainframe server. One or
more 10 Gbps and higher connections will be directly attached to these servers
in the near future, requiring internal 10 Gbps and higher internal I/O busses.
This is where interfaces like InfiniBand(TM) and PCI-XXX enter the picture (yeah
I made PCI-XXX up :-). It just so happens that InfiniBand and 10 GFC and 10 GbE
requirements for code space are pretty similar when you get right down to it. 

"Brown, Ben [BAY:NHBED:DS48]" wrote:
> Rich,
> Rich Taborek wrote:
> >
> > > Page 1: I agree with everything here except perhaps the /O/.
> > >   I'd like to understand more about why this is needed.
> >
> > I've included the /O/, representing "other" in support of other standards such
> > as Fibre Channel and InfiniBand with common parts, for other OAM&P functions for
> > Ethernet WAN access and WAN applications, and for other unforeseen extensions to
> > 10 GbE since I believe that we shouldn't assume that we have all link control
> > functions covered. Both 8B/10B and 64B/66B proposals currently support
> > additional control codes which may be required to provide /O/ support for the
> > purposes described above.
> I agree the code space is available and that it should be held
> reserved. I think a healthy debate is yet to be waged on the virtues
> or follies of explicitly supporting other standards (Fibre Channel
> and Infiniband) within "ae".
> > > Page 2: I agree with everything here except the following:
> > >   This applies for any serial PCS, 64b/66b or other. I think
> > >     this is the picture that I envisioned when I started this
> > >     thread and wat I understand is the picture that Mr. Rick
> > >     Walker is in support of based on his most recent comments.
> > >   The WWDM encoding may be identical to XAUI or may be
> > >     something else completely. Either way, I'd like to
> > >     see this specified with the encodings supported/
> > >     required by RS only. Even XAUI is specified this way.
> > >     XAUI requires /A/K/R/ for a further encoding of the
> > >     IDLE stream but it takes /I/ as input (along with all
> > >     the others /S/T/d/E/RF/BL/). Our debate is where the
> > >     /A/K/R/ gets stripped off after XAUI.
> >
> > I'm not sure I understand exactly what you're disagreeing with on page 2 since
> > its intention was to show your view: "Serial PHY, 64B/66B PCS, XGXS never
> > forwards /A/K/R/." Page 2 clearly show /A/K/R/ being stripped off and translated
> > back to /I/ by the XGXS adjacent to the PCS in Device A.
> >
> > Our debate has also focused on only the Serial PHY and only on 64B/66B coding.
> > I'd like to keep our debate focused on these elements only. I believe that this
> > coding debate is applicable to and independent of other PHY's and encodings, but
> > I'd like to focus on the PHY/PMD we started with, especially since it is
> > endorsed by a significant cross section of IEEE 802.3ae Task Force members.
> >
> > Can you please explain your disagreement with page 2 with respect only to the
> > Serial PHY with a 64B/66B PCS.
> With respect to a Serial PHY using 64b/66b, I am in full agreement
> with page 2. I was merely pointing out that this can also apply to
> other serial PCS proposals in addition to 64b/66b and that WWDM is
> a bit off the beaten path. These discussions probably deserve their
> own thread.


> > > Page 3: I think that this is the picture you've been in
> > >   support of and the one that the current 64b/66b proposal
> > >   describes. I don't agree with this picture.
> >
> > If you'll allow me to twist your words: I believe that you agree that the
> > picture accurately represents my previous view of XAUI/XGXS and PCS operation
> > for the Serial LAN PHY with 64B/66B encoding. Your disagreement is with this
> > mode of operation, not the picture. I know it's a minor point, but I am trying
> > to accurately portray our debate in pictures since words are apparently not
> > working.
> Again, you are absolutely correct. I disagree with this mode
> of operation. Because this picture represents this mode of
> operation, I don't particularly like it but my distaste is
> based solely on the mode of operation that it represents, not
> the picture itself. I think it is a great picture to describe
> your previous view of XAUI/XGXS and PCS operation.

Great! that was my intention, to picture what you disagreed with and allow
others to see the same.

> > > Page 4: A minor twist to page 3.
> >
> > Wow! This comment boggles my mind!
> >
> > This picture is the heart of the presentation and illustrates a solution to
> > problems exemplified in page 2, call it Ben's picture, and page 3, call that one
> > Rich's picture. I must not have done a good job on the picture in page 4 or
> > maybe they all look too similar.
> >
> > This page shows control codes being generated by the transmitting RS and
> > modified by the transmitting XGXS, if present. Control codes are then
> > transparently transported by the PCS and over the medium. All control codes not
> > specified by 10 GbE are translated to Idles by the RS. The latter translation
> > occurs in a manner analogous to that of the 1000BASE-X PCS Receiver.
> Again, the picture is a fine one that, I believe, accurately
> represents your current view of XAUI/XGXS and PCS operation.
> I guess I should have been more explicit. I'm not against the
> incremental step that this page shows. This incremental step
> of having the RS treat everything it doesn't recognize as an
> /I/ is fine. I merely disagree with the base content that was
> carried forth from page 3.

Now we're getting to the root of the problem. We already agree that multiple
control codes must be transported by 64B/66B and the medium. These include
/S/d/I/E/RF/BL/ and we even agree that there are some good reasons to transport
/O/. I'm looking for the simplest way to support all required and optional 10
GbE sublayers and interfaces in a PMD independent fashion. I would do the same
for an SLP-based PCS for the Serial LAN or WAN PHY, for WWDM based on 8B/10B and
for WWDM based on an alternate PCS. Having the RS Receiver simply treat all
undefined codes as Idles the simplest scheme I could come up with. This scheme
is capable of supporting all proposed PCS and interface codes assembled in any
combination for the 10 GbE link.

I believe that you'll find that the "base content" that you disagree with may be
different for different PCS and optional interface codes. The scheme outlined on
Page 4 is "base content" independent.

> > > Page 5 & 6: I don't see any difference between these 2 pages.
> > >   I agree with this.
> >
> > I included these for completeness. They illustrate the "reverse" or Device B to
> > Device A path analogy to Pages 2 and 3, respectively.
> >
> > > Page 7: A minor twist to 6 & 7. Though subtle, I don't like
> > >   this but I could probably be convinced by using the same
> > >   arguement that allows the 1000Base-X receive state machine
> > >   to treat "everything else" as /I/.
> >
> > I'm still surprised by your comment on page 4 since Page 7 illustrate the
> > "reverse" or Device B to Device A path analogy to Page 4. Your statement that
> > "to treat "everything else" as /I/" is exactly what I had in mind. I'm offering
> > this as the solution to our debate. I'm open to other solutions which can
> > resolve our debate in a simple manner.
> As I tried to clean up earlier, I agree that this incremental
> step is a good one (having the RS treat everything it doesn't
> recognize as an /I/). I simply disagree with carrying /A/K/R/
> outside the boundary of the XGXS blocks.
> The bottom line is that we're still in disagreement with the
> fundamental aspect of this proposal. The pictures are great,
> the addition to the RS is great. I simply don't think /A/K/R/
> should be carried outside the boundaries of the XGXS blocks
> and you think that it's okay if it does. I don't seem to have
> changed your mind and you don't seem to have changed mine.
> I think we could have gotten to this point about a month
> faster if we were drawing on napkins, sitting in nice comfy
> chairs drinking Guiness.

No doubt. Thanks for boiling down your real concern though. I believe the
pictures have helped. 

Transporting /A/K/R/ through 64B/66B, SLP, SUPI or any other Serial or WWDM PCS
code, given the other mandatory requirements to transport control codes is
supported in current proposals (e.g. 64B/66B). It is simple to implement (I can
prove that). I'd like to understand your reasons for not carrying /A/K/R/
outside the boundary of XGXS blocks? Do you object specifically to the actual
36-bit encodings of the /A/, /K/ or /R/ columns? Why should these be treated any
differently than a 36-bit encoding for /I/? 

Personally, I think we're down to nit-picking. I've offered up a solution to get
away from the nit picking. I'd really like to hear from you and others from an
implementation perspective regarding this solution.

> > > I don't think any of my responses have surprised you. At this
> > > point in the thread, I think we know where each other stands.
> > > It would be interesting to hear a few others weigh in on this.
> > >
> > > Thanks for the nice pictures. This should make involvement by
> > > the rest of the group much easier.
> >
> > That was the intention. Anyone else out there want to offer their opinions?
> Please, let's get some new blood in on this discussion! I feel
> like we're in a vacuum.

I agree. We either need more participation, or more Guinness :-)

> Ben
> --
> -----------------------------------------
> Benjamin Brown
> Router Products Division
> Nortel Networks
> 1 Bedford Farms,
> Kilton Road
> Bedford, NH 03110
> 603-629-3027 - Work
> 603-624-4382 - Fax
> 603-798-4115 - Home
> bebrown@xxxxxxxxxxxxxxxxxx
> -----------------------------------------


Best Regards,
Richard Taborek Sr.                 Phone: 408-845-6102       
Chief Technology Officer             Cell: 408-832-3957
nSerial Corporation                   Fax: 408-845-6114
2500-5 Augustine Dr.        mailto:rtaborek@xxxxxxxxxxx
Santa Clara, CA 95054