RE: Hari
Funny, these are exactly the arguements that were used by the various
systems companies that put down the initial requiremetns for Hari.
The Hari interface should use less power, fewer pins, and therefore make it
possible to have a future transceiver in the size (or smaller) of a current
LC or MT-RJ Small Form Factor (MSA) transceiver. It should remove the
difficulties of dealing with set-up and hold and other time/skew issues.
This should allow for a simpler system design/architecture (OK, call it
sloppy if you want, though I don't believe it) -- either way, this should
translate into less cost. My understanding is that chips that are designed
for the wide interfaces are pad bound, and not circuit bound. I have never
known this to be a good trade-off. These wide interfaces have no future path
for high density. They do not allow high levels of integration with eventual
multi-port implementations. In short, these are "point-in-time" solutions
that should not be the basis of a future-looking standard. Typically, the
industry reverts to parallel when it can't do the job in serial. Less is
almost always best.
The fact that a low-circuit-count 8B/10B encoder/decoder is required at each
end of the interface is not relivant. The real cost in a system design is
board space, routing difficulty, power, etc. Not a few extra circuits in a
MAC or PMD chip.
Hari is being used, I think, as a Red Herring for many more substantial
issues that need to be resolved regarding the WAN and LAN PHYs.
Questions:
What will need to be done to make it possible for LAN and WAN PMDs to be the
same. Is this possible? What are the trade-offs in doing so. Does it mean
suboptimizing the LAN PHY? If not, will we be putting FEC into all the LAN
PHYs?
How exactly will the length field be generated for the WAN PHY. I know where
it will likely be specified in the standard, but where will it be
implemented. Will a single chip WAN/LAN MAC be a reality?
If there is a common WAN/LAN MAC, and a common WAN/LAN set of PMD's, then
what is the common interface between these (I understand that this interface
may or may not be a specific layer boundary in the standard)? Is it possible
that it happens to be the interface that was designed for the OC-192 world
when the designers took none of these and a multitude of other issues into
consideration?
Does it matter to the Ethernet community if Fibre Channel and SIO
(Infiniband) are able to use the same transceivers and thereby improve the
overall cost structure?
I could go on for a very, very long time. Bottom line, answer all of the
above questions and I will show you how to use Hari or any other interface
to accomplish the objectives.
Is there an agenda? Of course there is an agenda. It is all of the above and
more. I think I talked about all of that in my presentation. In short, I
think I already exposed the agenda.
jonathan
> -----Original Message-----
> From: Roy Bynum [mailto:rabynum@xxxxxxxxxxx]
> Sent: Monday, November 22, 1999 9:37 PM
> To: Fred Weniger; HSSG
> Subject: Re: Hari
>
>
>
> Fred,
>
> Is or is not Hari a 8B10B encoding method? Is 8B10B the same
> encoding method that
> has been suggested for the WAN PHY? If not, then there must
> be some sort of
> translation, almost another MAC bridge to take the 802.3
> frames from the Hari
> interconnect and put them into another encoding method. Are
> you suggesting that we
> create another, secondary, MAC bridge just to support a
> different PHY? Was this
> what was presented at York? I don't think that is what is in
> the objectives.
>
> As for real estate on the PC board. Vendors need to think
> about reducing the size
> of their boards and systems. More and more floor space is
> being taken by these
> systems as well as power and cooling. Reducing the size of
> the boards, reducing the
> amount of electronics, reducing power requirements, and
> increasing the density of
> the connections is becoming an issue in large installations,
> like those that will
> use P802.3ae. Hari tends to take exactly the opposite
> direction in system design.
> Hari makes it easy for the system designer to become sloppy,
> not requiring them to
> become tighter and better.
>
> Thank you,
> Roy Bynum
>
> Fred Weniger wrote:
>
> > Dear Ladies and Gentlemen:
> >
> > Before we commence constructing a DMZ between the LAN and
> WAN 10GbE camps,
> > may I remind one and all that Vitesse offered a proposal at
> the Kauai HSSG
> > which we believe will provide an alternative path to peaceful
> > co-existence. Our proposal allowed the MAC to run at 10 Gb/s, and
> > suggested a "pause" or "rate-match" function on the XGMII
> to allow HARI to
> > run at 2.9952 Gb/s on each of the four lines if it is
> intended for WAN
> > connection. We stated that a HARI to SONET LITE framer could be
> > implemented in CMOS, and could use the OIF-proposed
> standard 16- bit Serdes
> > to serialize the date in an OC-192 COMPATIBLE format. We,
> as chip makers,
> > believe this is quite achievable, and provides both camps
> with what they
> > want. If there are those who disagree, please reply.
> >
> > At 10:37 PM 11/20/99 -0600, Roy Bynum wrote:
> >
> > >Rich,
> > >
> > >I'm not sure what gave you the idea that Hari was
> favorable to serial
> > >PHYs. I do know that
> > >it is not favorable to anything other than the legacy
> fiber channel 8B10B
> > >LAN PHY. Hari is
> > >NOT a PHY neutral device interconnect. Some LAN vendors
> have very huge
> > >boards and they want
> > >
> > >something that will support their 8B10B encoding over the
> distance of
> > >their board, and also
> > >the back plane if needed. By introducing Hari as the
> standard for device
> > >interconnect
> > >between the PMA and the PMD, they are specifically, and possibly
> > >knowingly, hampering the
> > >development of the agreed on WAN PHY. There is no
> mechanism for rate
> > >controlling over
> > >Hari. This is in violation of the agreed objective in
> this regard. Hari
> > >is an attempt by a
> > >specific camp to control the development of 10GbE and
> limit development of
> > >anything other
> > >than the 10.0 only rate PHY.
> > >
> > >As you will remember, I called the presenters and floor on
> the issue of
> > >what Hari really
> > >was. It was admitted that it was a LAN extension
> interconnect by the
> > >individual that
> > >responded. For those of us that are attempting to bring
> 802.3 into the
> > >20th century by
> > >making a truly ubiquitous MAC, we have been astounded by
> the brazen push
> > >of this
> > >"interconnect". Chip makers will confirm that Hari
> specifically makes
> > >the WAN PHY
> > >extremely difficult to implement. Since Hari truly is not
> common to all
> > >of the PHYs as
> > >specified in the objectives, I suggest that it be withdrawn from
> > >consideration as part of
> > >the 10GbE standard.
> > >
> > >Thank you,
> > >Roy Bynum
> > >
> > >
> > >
> > >Rich Taborek wrote:
> > >
> > > > Roy,
> > > >
> > > > I thought that Hari was clearly presented in at least
> half a dozen
> > > presentations by at
> > > > least the same number of presenters who all explained
> it in the same
> > > way in Kauai. I'll
> > > > try one more time here.
> > > >
> > > > Hari is the same as the Serial interface of the 10 GMII
> as presented to
> > > the HSSG by
> > > > Howard Frazier of Cisco in Montreal, York and Kauai. A group of
> > > Ethernet, Fibre Channel,
> > > > InfiniBand and even OIF folks have gotten together over the past
> > > several months to try
> > > > and arrive at a common interface for passing 10 Gbps of data
> > > continuously in each
> > > > direction between a PCS/PMA element (which may be
> integrated with the
> > > MAC and the PMD
> > > > (i.e. transceiver module).
> > > >
> > > > Note that a typical Ethernet PHY, like 1000BASE-X
> contains the PCS, PMA
> > > and PMD
> > > > sublayers. Hari is NOT a PHY nor is it a PHY sublayer.
> Hari is an
> > > interface between
> > > > sublayers and is very similar in nature to the Ten-Bit
> Interface (TBI)
> > > of 1000BASE-X,
> > > > which is fully described in Clause 36 of that standard.
> > > >
> > > > Hari has nothing at all to do with WWDM although it
> clearly may be used
> > > to attach a WWDM
> > > > PMD to its MAC/PCS/PMA.
> > > >
> > > > Hari may be used to attach a Parallel Optical PMD to
> its MAC/PCS/PMA in
> > > much the same
> > > > fashion as for WWDM
> > > >
> > > > Hari usage to attach a MAS PMD to its MAC/PCS/PMA has
> been described in
> > > all my MAS
> > > > proposals to the HSSG including the latest update
> presented in Kauai:
> > > >
> > >
> http://grouper.ieee.org/groups/802/3/10G_study/public/nov99/ta
> borek_2_1199.pdf
> > > >
> > > > Hari usage to attach a Serial PMD to its MAC/PCS/PMA
> along with a
> > > proposed coding to
> > > > maintain a line rate of ~10 Gbaud has been described in
> the Kauai
> > > proposal by Rick
> > > > Walker and Richard Dugan of Agilent:
> > > >
> > >
> http://grouper.ieee.org/groups/802/3/10G_study/public/nov99/wa
> lker_1_1199.pdf
> > > >
> > > > Therefore, Hari provides a common interface for all
> major classes of
> > > PMDs proposed to
> > > > the HSSG to date in addition to being strongly
> considered as a common
> > > interface for
> > > > other ~10 Gbps standard and industry interfaces.
> > > >
> > > > The principal strengths of Hari are:
> > > > 1) Low pin count
> > > > 2) Self-timed (doesn't need a clock with data)
> > > > 3) Supports reasonable distances over inexpensive
> medium (e.g. 20" of
> > > FR4 traces)
> > > > 4) Good synergy with traditional Ethernet MAC/PHY framing
> > > > 5) Sufficient robustness to not compromise a 10E-12 link BER
> > > >
> > > > 8B/10B encoding has been proposed for Hari since it has
> been proven
> > > time and time again
> > > > in multiple forums that 8B/10B is a very robust serial link
> > > transmission code. However,
> > > > Hari is not a PCS and an alternate code could have been
> proposed for
> > > Hari. I consider
> > > > the Hari usage of 8B/10B to be analogous to a parity bit for a
> > > traditional parallel
> > > > interface. The "parity bit" can be generated at the source and
> > > discarded after checking
> > > > at the destination. The MAS and Serial PMD proposals
> referenced above
> > > use Hari in
> > > > exactly this fashion and result in the lower line rate
> possible for
> > > those respective
> > > > interfaces when compared to a PMD coding which would
> carry forward the
> > > 8B/10B overhead.
> > > >
> > > > Hari is being proposed for inclusion into the 802.3ae
> standard as an
> > > interface as
> > > > described above. However, Hari does not dictate the
> encoding of data
> > > transported over
> > > > the Medium. Hari simply enables the transport of that
> data over the
> > > medium in a manner
> > > > commensurate with the 5 criteria of 802.3ae.
> > > >
> > > > As such, I would also recommend that Hari be considered
> for the WAN PHY.
> > > >
> > > > Best regards,
> > > > Rich
> > > >
> > > > --
> > > >
> > > > Roy Bynum wrote:
> > > >
> > > > > Rich,
> > > > >
> > > > > I am confused here. Is Hari being proposed as a PHY
> for the LAN
> > > compatible PHY of
> > > > > 10GbE? I have recognized that Hari only needs the
> WWDM optical
> > > interface to be a 4
> > > > > wavelength parallel short reach PHY. When it was
> first presented,
> > > the way that it
> > > > > was presented reminded me of a "solution looking for
> a problem". It
> > > certainly looks
> > > > > like there are a lot of people have been working on
> this for some
> > > time. All of the
> > > > > conversations on the reflector are starting to treat
> Hari as a PHY,
> > > not a device
> > > > > interconnect. I am confused why an interconnect
> suitable to be a
> > > full LAN PHY would
> > > > > be proposed first as a device interconnect. As a
> 500m and less LAN
> > > PHY, I am
> > > > > neutral on Hari. As something else, I confused by
> the way it was
> > > presented and have
> > > > > my doubts as to the overall impact of Hari as a
> device interconnect
> > > and the
> > > > > limitations that it inherently makes on the PCS/PMD
> relationship.
> > > > >
> > > > > Hari as a device interconnect requires specific
> functionality. It
> > > forces the
> > > > > physical coding functionality of non parallel PHYs to
> exist at the
> > > PMD, not the
> > > > > PCS. I have been told by a Hari supporter that the
> PCS/PMA/PMD
> > > relationship is
> > > > > purely for the standard and has little relationship
> to how protocols
> > > are implemented
> > > > > and devices are actually designed. If device and protocol
> > > implementation has little
> > > > > to do with the standard, why have the standard? If
> the protocol
> > > implementation is
> > > > > specific to the standard, then Hari is a PCS specific
> to a particular
> > > PHY and is
> > > > > exclusive of other PCS definitions for other PHY definitions.
> > > > >
> > > > > If Hari is a PCS, let us recognize it as such and
> move on with other PHY
> > > > > definitions. If it is not a PCS then let us
> recognize that it will
> > > alter the nature
> > > > > of the relationships of the PHY functionalities for
> the non-WWDM PHYs
> > > dramatically.
> > > > > A silicon designer can best determine if the increase
> in complexity
> > > of the PMD is
> > > > > countered by the pin count benefits of Hari as
> something other than a
> > > PCS. Hari as
> > > > > a device interconnect needs to be removed from the
> table. Hari as a
> > > PCS, with minor
> > > > > modifications can be evaluated as such.
> > > > >
> > > > > Thank you,
> > > > > Roy Bynum
> > > > >
> > > > > Rich Taborek wrote:
> > > > >
> > > > > > The purpose of this note is to clear up confusion
> regarding Hari, a
> > > > > > proposed 4-lane serial interface for 10 GbE and
> train-up sequences.
> > > > > >
> > > > > > It should be clear that NO TRAINING SEQUENCES are
> proposed for Hari.
> > > > > > Both the "Hari Coding Objectives" presentation
> > > > > >
> > >
(http://grouper.ieee.org/groups/802/3/10G_study/public/nov99/taborek_1_119
> > 9.pdf)
> > > > > and "Word Striping on Multiple Serial Lanes"
> > > > >
> >
http://grouper.ieee.org/groups/802/3/10G_study/public/nov99/ritter_1_1199.pd
f)
> > > > > make a point of noting that no train-up is required Hari to
deskew.
> > > > >
> > > > > The Hari Coding Objectives proposal uses the standard Idle
sequence
> > > > > proposed by Howard Frazier of Cisco to deskew multiple parallel
lanes
> > > > > while simultaneously acquiring code-group synchronization on all
lanes.
> > >
> > > ----------------------------------------------------------
> > >
> > > Richard Taborek Sr. 1441 Walnut Dr. Campbell, CA 95008 USA
> > > Tel: 408-370-9233 Cell: 408-832-3957 Fax: 408-374-3645
> > > Email: rtaborek@xxxxxxxxxxxxx
>
> Fred Weniger
> Gigabit Product Marketing Manager
> 805-388-7571
> weniger@xxxxxxxxxxx