Re: PMD discussion
Jay,
I agree with you. However, I believe that we are loosing sight of the ultimate
goal of the WAN PHY: Compatibility with the SONET/SDH infrastructure.
I'd like to address a comment regarding our objectives that was made during the
Ottawa meeting on several occasions: It was said that a LAN PHY with a WIS (for
SONET/SDH compatibility) does not meet the HSSG objectives. I'm having trouble
understanding why a solution which "exceeds" the objectives, and is highly
likely to be lower in cost, is inferior to one which "meets" the objectives.
The specific objective in question is as follows:
Define two families of PHYs
– A LAN PHY, operating at a data rate of 10.000 Gb/s
– A WAN PHY, operating at a data rate compatible with the payload rate of
OC-192c/SDH VC-4-64c
It has been proposed, and there is general agreement (i.e. lack of any other
proposal) that the WIS, a layer 1 (PHY) sublayer is used to encapsulate Ethernet
packets, using 64B/66B for a PCS, for transport over SONET/SDH. The latest
relevant proposals from Ottawa are:
http://grouper.ieee.org/groups/802/3/ae/public/may00/bottorff_1_0500.pdf
http://grouper.ieee.org/groups/802/3/ae/public/may00/nicholl_1_0500.pdf
http://grouper.ieee.org/groups/802/3/ae/public/may00/walker_1_0500.pdf
The location of the WIS in a WAN PHY can be illustrated as follows:
+-----+ +-----+ +-----+ +-----+
--->| |--->| PHY |------->| |--->|SONET|
| MAC | | | medium | PHY | | \ |
<---| |<---|(WIS)|<-------| |<---| SDH |
+-----+ +-----+ +-----+ +-----+
(rate
controlled) |<--- WAN PHY ---->|
Alternatively, the location of the WIS in a LAN PHY can be illustrated as
follows:
+-----+ +-----+ +-----+ +-----+
--->| |--->| |------->| PHY |--->|SONET|
| MAC | | PHY | medium | | | \ |
<---| |<---| |<-------|(WIS)|<---| SDH |
+-----+ +-----+ +-----+ +-----+
(rate
controlled) |<--- LAN PHY ---->|
Note that the WIS function simply moves to the right (towards SONET/SDH) and the
same PHY, a LAN "UniPHY" if you will, may be used to achieve full SONET
compatibility. MAC/PHY rate control is not issue between the two methods. I
understand how to implement it either way.
Please point out the flaw(s) with the LAN UniPHY in supporting Ethernet over
SONET. Is it that there is a unwritten requirement for a WAN PHY to support
payloads other than Ethernet over SONET/SDH? I'd call any such requirements out
of the scope of IEEE 802.3.
Best Regards,
Rich
--
jay.hoge@xxxxxxxxxxxxxx wrote:
>
> In order for the WAN PHY to do its job, it cann't use a line code or else
> the data rate will exceed that of OC-192. Scrambling anyone?
>
> Jay
-------------------------------------------------------
Richard Taborek Sr. Phone: 408-845-6102
Chief Technology Officer Cell: 408-832-395
nSerial Corporation Fax: 408-845-6114
2500-5 Augustine Dr. mailto:rtaborek@xxxxxxxxxxx
Santa Clara, CA 95054 http://www.nSerial.com