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Re: Issues in mapping Ethernet signal to SONET


We prefer the <length><type><hec> frame delimiting system because it
provides the most efficient encoding and allows easy extension for ANSI
T1X1.5 applications. The 64/66 code forces an additional 3% overhead which
is not necessary when using <length><type><hec>. Though the SLP code (which
we are supporting for the LAN-PHY) does not add any overhead it also does
not allow IDLE deletion which <length><type><hec> allows. 

The <length><type><hec> provides an easy method for extension since the
<type> is covered by the <hec> giving the option to decode new frame types.
Neither of the other codes provide this feature.

Using <lenght><type><hec> it is possible to compress the data stream by
deleting all the IDLE bytes on the wire. These are regenerated in the PHY
before sending data to the MAC.

The <length><type><hec> delimiting system is a variation of the ATM hec
system which has been field proven for many years. Both the 64/66 and the
SLP encodes are brand new and unknown.

The use of a <length> calculation buffer in the PHY is a cheap solution
which allows the use of <length><type><hec> without any MAC modifications.   



At 09:54 AM 4/11/00 -0700, Devendra Tripathi wrote:
>Could some one illustrate (or give pointer to existing document) on various 
>in mapping an Ethernet signal
>@9.584640 (+-100ppm) to OC-192 stream. As Paul has already pointed out,
>the muxer, should be able to absorb 320 ppm tolerance. Basically I would like
>to understand the reasoning for Length insertion in preamble (which makes the
>scheme somewhat unpleasant). The basic
>OAM&P function like remote fault and break link are already being talked
>about as part of the control code (as part of Ethernet stream).
>Thanks in advance,
>Best Regards,
>Devendra Tripathi
>Vitesse Semiconductor Corporation
>3100 De La Cruz Boulevard
>Santa Clara, CA  95054
>Phone: (408) 986-4380 Ext 103
>Fax:	(408) 986-6050
Paul A. Bottorff, Director Switching Architecture
Enterprise Solutions Technology Center
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