Re: Interface reality check
Roy,
In the grand scheme of things, IEEE 802.3 committee members are assembling
complete consensus proposals based on solid existing as well as new
technologies. Some of the existing technologies included in very strongly
supported proposals are:
1) SONET OC-192 lasers;
2) 8B/10B transmission code;
3) Clock tolerance compensation by Skip column insertion/removal from
InfiniBand;
4) 32-bit Word delimiters and control words from Fibre Channel;
5) WDM technology from telecom based DWDM equipment;
6) Scrambling for 64B/66B transmission code from SONET scrambling.
WWDM, Serial LAN PHY and UniPHY proposals based on the above proposals have
already achieved a significant amount of support from 802.3ae members.
I find that having code space available is a critical element in high speed
serial link design.
Instead of disparaging codes like 8B/10B and 64B/66B with "code space" please
help to define a competing proposal for the LAN PHY. I'm afraid that SONET/SDH
is just no competition for the existing WWDM, Serial LAN PHY and UniPHY
proposals.
I have also heard you publicly tout the overhead characteristics of SONET/SDH
framing as code space. Is this not true. Apparently, all serial link optical
transports require "code space".
Best Regards,
Rich
--
Roy Bynum wrote:
>
> Rich,
>
> You keep making references to 'code space' as if Fibre Channel and
> InfiniBand were the only signaling formats that could be used as 10Gb. SDH
> and SONET have been doing 10Gb as scrambled encoding for several years. I
> see no need to keep the legacy bandwidth limited 'code space' of Fibre
> Channel as a limiting factor for P802.3ae. SAN implementations will be
> using P802.3ae, not because of the code space, but because of the 802.3 MAC
> that can better create a data link between systems. I see no need to burden
> 10GbE with the same Fibre Channel 'code space' as GbE was limited to using.
> Just as 1.065 Fibre Channel was used as a model for GbE, then 10Gb SDH and
> SONET should be used as a model for 10GbE.
>
> Thank you,
> Roy Bynum
>
> ----- Original Message -----
> From: Rich Taborek <rtaborek@xxxxxxxxxxxxx>
> To: HSSG <stds-802-3-hssg@xxxxxxxx>
> Sent: Saturday, April 01, 2000 3:02 PM
> Subject: Re: Interface reality check
>
> >
> > Ben,
> >
> > 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.
> >
> > Yep.
> >
> > > > > 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,
> > Rich
> >
> > -------------------------------------------------------
> > 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 http://www.nSerial.com
-------------------------------------------------------
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 http://www.nSerial.com