RE: Long distance links
I'd like to second Dan's words of wisdom. The MII (or AUI for
you older folks :-) has provided a means of decoupling a vast
number of physical layer access issues from the media access
layer. As Ethernet has progressed, the "MAC" has evolved to
be a frame format. This simplicity lead to the propagation of
100 and 1000 Mbps Ethernet in all kinds of bizarre environments.
By using the MII to decouple the physical layer in 10G Ethernet,
the 802.3 will allow the market to decide which PHY is best
suited for deployment in a given situation.
JR
At 09:06 AM 9/1/99 -0600, DOVE,DANIEL J (HP-Roseville,ex1) wrote:
>
>I can't believe the level of confusion this reflector brings me! :)
>
>I don't interpret Paul's comments to mean that SONET/OC-192 must
>be THE 10GbE PHY, but I am sure that he would like it to be the
>10GbE WAN PHY which is just fine with me.
>
>However, I still don't understand the persistence that the MAC/PLS
>must run at any speed other than 10.0000Gbps. I think we all realize
>that a 10.0000Gbps interface at the MAC/PLS is going to yield something
>less than a 10.0000Gbps throughput no matter WHAT PHY is running below
>it due to the overheads of preamble, delimiters, and IPG... not to
>mention a possible SONET/OC-192 PHY and it's particular issues.
>
>I sure wish we could come to consensus on the fact that it is not
>only possible to accomodate OC-192 with a 10.0000 Gig MAC, but that
>this would provide the most efficient solution from the standpoint
>of product implementation AND standards work.
>
>It makes sense to put PLLs and FIFOs in PHY components rather than
>to burden the MACs with such things. The additional complexity at a
>WAN PHY is where SONET/OC-192 complexity belongs. Why are we not
>converging upon these points?
>
>Let's revisit Paul's statements...
>
>> -------------- from Paul --------------------------
>> To carry Ethernet frames on a SONET system:
>>
>> 1)Ethernet must match the payload rate of 9.584640 Gbps
>> 2)Ethernet frames must be encoded with NRZ efficiency
>> 3)Ethernet frame delimiting must operate without
>> special symbols
>> ------------ end from Paul ------------------------
>
>Couldn't this be simply resolved by stating that the WAN
>PHY must;
>
>1) Resolve the rate mismatch by using HOLD or some other mechanism
>2) Encode data using NRZ
>3) Strip Ethernet frame delimiters and re-insert them as necessary
>
>Again, these seem easily accomplished within what is called a PHY.
>
>Look at the complexity of a 1000BASE-T PHY and you should see that
>once the data gets below the MII, it doesn't really matter what
>happens to it as long as it gets to the other port's MII in the form
>of an Ethernet frame.
>
>Regards,
>
>Dan Dove
>
>> Paul,
>>
>> I believe that we agree more than you think. You state in the
>> first paragraph of
>> your note that: "Ethernet is just not viable as a mainstream
>> WAN protocol without
>> some consideration of SONET." I can't agree more with this
>> statement. What I can't
>> agree to is either of the following:
>>
>> 1) Rubber stamp the SONET/OC-192 PHY as the 10 GbE PHY; or,
>>
>> 2) Wholesale limitations to the objectives and directions of
>> the HSSG by the
>> imposition of 9.58464 MAC/PLS rate, NRZ encoding efficiency
>> (I assume you mean 0%
>> overhead, scrambling, etc. since NRZ by itself doesn't say
>> much), and frame
>> delimiting without special symbols.
>>
>> If you're seriously interested in either of the above, I
>> believe you'll encounter
>> significant hurdles in the HSSG.
>>
>> If you mean what you say about "some consideration of SONET"
>> then I and many other
>> HSSG members are eager, ready and willing to listen and
>> learn. I speak from
>> experience here having participated in the recent and very
>> successful development
>> of the Gigabit Ethernet architecture. I was one of a group of
>> individuals who
>> introduced Fibre Channel Physical Layer architecture to the
>> GbE HSSG back in 1996.
>> FC and GbE folks worked together to take elements of Fibre
>> Channel and fit them
>> into the Ethernet structure. Careful consideration was given
>> to all aspects of
>> Ethernet including product implementation, support of the
>> installed base,
>> migration, operations, performance, etc. The HSSG is ready to
>> "do it again" for 10
>> GbE.
>>
>> You yourself during the 10 GbE Call for Interest presented
>> (http://grouper.ieee.org/groups/802/3/10G_study/public/march99
>> /bottorff_1_0399.pdf)
>> a "Packets on Photons" architecture (page 5) which
>> essentially shows IP carried by
>> 10 GbE carried by Optics. I see no SONET in this picture. I
>> assume that Optics
>> stands for DWDM systems. I have no problem with this picture.
>> Is it your intention
>> is to take the "10 GbE" box and replace it with a SONET/OC192
>> architecture rubber
>> stamped by 802.3? If not, what exactly are your intentions?
>>
>> If the 10 GbE box is filled with an architecture developed by
>> 802.3 to meet the
>> objectives set forth and agreed to by the HSSG, then I'm
>> perfectly happy to
>> consider supporting the WAN and considering elements of SONET
>> in achieving this
>> specific objective.
>>
>> Best Regards,
>> Rich
>rest of entire string deleted...