RE: What is ~10 Gb/s?

["Thirion, Walt" <wthirion@xxxxxxxxxx>]

So, in your opinion the only data rate we need at the MAC interface is
9.584640 Gb/s (data rate). For transmit, the Sonet PHY would take in raw
ethernet data at this speed and spit out encoded data at 9.95328 Gb/s
(baud rate) and do the opposite for receive. Doing this would allow the
10 Gb/s ethernet MAC to be directly connected to the Sonet network. Is
this a correct summation?
 
To continue down this path, are there any other signals necessary to
support the direct connection, i.e. does the MAC have to be
started/stopped/etc.? Is there any kind of flow control between the
Sonet PHY and its upper layer clients? etc. etc. etc.
 
Would adopting the Sonet data rate allow us to use already developed
PHYs or would we still need to customize features, etc. for
autonegotiation, coding, etc.?
 
I'm trying to narrow down the issues to see if it really is simply a
matter of 9.584640 Gb/s vs. 10.000 Gb/s or if other issues come into
play.
Walter Thirion 
Level One Communications 
512-407-2110 

 
 
 
 

-----Original Message-----
From: pbottorf@xxxxxxxxxxxxxxxxxx [mailto:pbottorf@xxxxxxxxxxxxxxxxxx]
Sent: Monday, June 21, 1999 12:16 PM
To: 'stds-802-3-hssg-speed@xxxxxxxx'; Thirion, Walt
Subject: Re: What is ~10 Gb/s?




My answers, 


At 01:04 AM 6/21/99 -0500, Thirion, Walt wrote: 

>>>> 

What is ~10 Gb/s? 


Ok, I would like to get the discussion really going. So, I'm going to
propose a couple of issues. Hopefully, we'll get extensive reflector
discussion, then I'll schedule a conference call for Wednesday to try to
hash out differences. 


A lot of the discussion revolves around the objective of whether we want
to support a direct attachment to the WAN infrastructure by having a
specification that maps 10Gig directly to an OC-192 like interface. 


For the sake of discussion, my first objective is to nail down exactly
which speeds we're talking about. There were a couple of numbers thrown
out at the Interim in Idahao. The following table was taken from the web
site at http://www.data.com/tutorials/sonet.html. 


Comparing Capacity 

OC level Number of DS-3 

circuits or STS-1 DS capacity ATM capacity POS capacity 


tributaries (Mbit/s) (Mbit/s) (Mbit/s) 


OC1 1 45 47 52 

OC3 3 135 129 156 

OC12 12 540 563 622 

OC48 48 2,160 2,254 2,488 

OC192 192 8,640 9,014 9,953 

OC768 768 17,280 36,057 39,813 


DS = Digital signal 

POS = Packet over Sonet 

STS =Synchronous transport signal 

______________________________________________ 


1. So, when we say ~10Gb/s, is there an actual number that we want and,
if so, what is that number? 

<<<< 

Yes, it is an actual number. The number is a data rate of 9.584640
Gbits. This rate is expressed after coding overhead (i.e. for 8b/10b
coding the baud rate would be 11.98080 Gbaud). The reason this number is
not identical to SONET transmission clock is because all SONET overhead
has been subtracted. The SONET transmission clock is 9.95328 Gbits of
which a few percent are coding overhead leaving a 9.584640 data payload.
The numbers quoted for POS above are incorrect since they include the
SONET overhead as data therefore not stating the actual line capacity. 

>>>> 



2. Is there more than one WAN number that we should be considering? If
so, what are they and what is the basis (standard) for the number? 

<<<< 

The 9.584640 is the only number which is required. Adaption to OC-48 and
OC-768 would be performed by inverse multiplexing and multiplexing
respectively. The question is whether we need any special considerations
to allow for multiplexing. This will depend on the PHY design not on the
10GMII interface rate. 

>>>> 



3. Is the number a "raw" bit/baud rate or is it the net after
subtracting some protocol overhead? 

<<<< 

The 9.584640 rate includes any Preamble, SA, DA, Type, FCS, and IFG. It
therefore includes protocol overhead, but not encoding overhead. 

>>>> 



4. When we talk about a direct connection to the WAN, is there also an
assumption that we will pick up the integrated management, i.e.
self-healing Sonet rings? 

<<<< 

The 10 GigE is not required to support self-healing or any other SONET
management attributes. At the demarcation point between 10 GigE and a
SONET ring a transcoding device will isolate the SONET characteristics
from 10 GigE characteristics. The transcoder will allow SONET management
on the SONET ring and Ethernet management on the 10 GigE ring. 


An independent issue to the speed is whether 10 GigE should have SONET
type management capabilities for self-healing and failure detection.
These may be desirable objectives, but have little to do with the speed
issue. The management issue is more important for dark fiber and dark
wavelength applications than SONET mapping applications. 

>>>> 



Walter Thirion 

Level One Communications 

512-407-2110 








Paul A. Bottorff, Director Switching Architecture 

Bay Architecture Laboratory 

Nortel Networks, Inc. 

4401 Great America Parkway 

Santa Clara, CA 95052-8185 

Tel: 408 495 3365 Fax: 408 495 1299 ESN: 265 3365 

email: pbottorf@xxxxxxxxxxxxxxxxxx

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