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Re: [HSSG] Reach Objectives



Geoff,
With all due respect, at 10G there were two rates and frame formats defined:
- The 10G LAN PHY, which some take to mean 10G BASE-R at 10.325 Gbit/s including the 64B/66B coding
- The 10G WAN PHY, which is built inside of a SONET/SDH wrapper at 9.58464 Gbit/s including 64B/66B coding.
 
As much as we wish that customers would all choose the LAN interface when they want to connect to a LAN and the WAN interface when they want to connect to a WAN, this hasn't happened. We see numerous cases for a variety of different reasons where people ask to take the 10G LAN PHY and carry it over a long distance.
 
There are some straightforward kinds of approaches to do this if you start from the assumption that Ethernet is really a packet interface and all you need to do is preserve the packets across the transport network. For example, you can carry your 10G LAN PHY by mapping it into an ODU2, decoding 64B/66B, dropping the preamble and IPG and replacing with GFP framing (saving 8-12 octets per packet) and using the OTN scrambler and get the full packet throughput of a 10G LAN PHY over a 10G transport network interface. At the far end, you reverse the process and regenerate a 10G LAN PHY signal with the same packet information content. But this breaks any proprietary stuff that people are doing with the preamble and IPG and seems to have an "image problem" with some operators that you are fiddling too much with the customer's stuff (even though most of us understand that this approach doesn't touch the payload).
 
Let me express the two suggestions that I am making for how we approach future interface definitions in terms of what it would have looked like had we done this at 10G:
- ONE RATE AND FORMAT - if we had recognized early enough that WAN was an important application and tried to unify things to the greatest extent possible, we might have elected that the XGMII being freshly defined wasn't exactly 10.00000000000 Gbit/s, but instead, say 9.282944 Gbit/s (if we decided that SONET/SDH was the dominant transport mode to be targeted) or 9.721329 Gbit/s (if we decided that OTN was the dominant transport mode to be targeted). Then you could have taken exactly the same 64B/66B coded bitstream that you used for the LAN and filled it directly into transport frames, and poof you are done. You wouldn't have had any of the market issues we see today.
- REPEATER DEFINITION - If we were to define a repeater that regenerates preamble & IPG and have a requirement that anything that works in a point-to-point configuration must also work across a repeater, we could discourage some of this proprietary stuff. If we then define that any layer 1 server layer network is supposed to meet the requirements for a repeater (appropriately defined), then you have the flexibility to use things like GFP framing over a transport network to get the extra throughput you need to fully carry all of the packets of a 10G LAN PHY Ethernet signal over a 10G transport network interface.
Regards,
Steve


From: Geoff Thompson [mailto:gthompso@xxxxxxxxxx]
Sent: Monday, September 04, 2006 12:27 PM
To: Trowbridge, Stephen J (Steve)
Cc: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [HSSG] Reach Objectives

Steve-

At 10:50 AM 9/4/2006 , Trowbridge, Stephen J (Steve) wrote:
Geoff,
We clearly have a problem at 10G that certain players have taken Ethernet to be more than a packet network:
- We have the situation that people have put information in parts of the frame not designed for carrying information (the preamble and IPG).
- We have the problem that some customers think that the entire frame format, not just the payload is sacred and must not be touched (some of this stems from the first problem, other parts of this problem are perception).
 
I think that it is worth some effort and careful though to make sure that this does not happen as we define interfaces for the next rate, e.g., that we keep it simple, and keep it as a (pure) packet network.
 
I think that there are two possible approaches:
- We could make sure that we define ONE frame format and data rate that works in all contexts

You mean we could continue to "define ONE frame format and data rate that works in all contexts"
vs. doing something else, i.e. define a new frame format which does not work in all contexts.
Sounds like a no-brainer to me.

(Further, I am of the belief that changing the frame format is outside the scope of "Higher Speed")

Geoff




This is starting to sound doubtful from the opinions expressed, but if we COULD achieve a single specification and ensure that anything that transits one medium would transit another, we could avoid these kinds of problems.
- I touched on this in the last email, but we could produce a repeater spec covering all interfaces and frame formats, e.g., if you have phsycial interfaces/frame formats X and Y, the repeater spec tells you enough that you could to build X<->X, Y<->Y and X<->Y repeaters and only what we consider to be the essential or characteristic information (the payload) would transit the repeater. We could indicate that any server layer network should meet the requirements for a repeater. Doing this might discourage inappropriate use of the frame format to implement proprietary things that would break if you put a standard repeater between the boxes.
 
Regards,
Steve

From: Geoff Thompson [mailto:gthompso@xxxxxxxxxx]
Sent: Sunday, September 03, 2006 8:47 PM
To: Trowbridge, Stephen J (Steve)
Cc: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [HSSG] Reach Objectives
At 03:46 PM 9/3/2006 , Trowbridge, Stephen J (Steve) wrote:
Geoff,
If only it were so simple ...
 
It is.

Ethernet is a packet network, not a bit or circuit network.





Geoff