Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

Re: why two different coding schemes ?


8B/10B is the most widely deployed transmission code for datacom
fiber-optic link operating at 200 Mbps and above. It is the only code
used in 1000BASE-X (Gigabit Ethernet) and would likely have been be the
only code used for the 10GE LAN PHY if it weren't for the difficulty in
obtaining 12.5 Gbps opto-electronic components at this point in time.
8B/10B is very "optics friendly".

64B/66B is employed in both the LAN PHY to keep the line rate of the
opto-electronics down to 10.3125 Gbps while supporting the 10GE data
rate of 10.0 Gbps.

Note that 10GE supports scrambled encoding for the WAN PHY which is a
third coding scheme. 

I strongly disagree that coding schemes complicate life for anyone. A
typical path from the central processor of a PC to the media platter of
a disk drive in a low cost system is likely to employ many more than two
coding schemes and perhaps 10 or more. Every coding scheme employed is
typically optimized for its particular application.

It is inappropriate to use this reflector or any other IEEE 802.3 forum
to discuss products and timings. Please take any such discussions and
questions off line. 

Best Regards,

Jagmit Sandhu wrote:
> Hi, I'm new to 10 Gb/s ethernet. Could somebody explain why two
> different coding schemes are being contemplated for 10GE ? i.e.
> 8B/10B and 64B/66B? Why not stick with just one to simplify life for
> everybody ? Also, are there any vendors with tentative 10GE products
> coming out soon?
> thanks
> jagmit sandhu
Richard Taborek Sr.                 Phone: 408-845-6102       
Chief Technology Officer             Cell: 408-832-3957
nSerial Corporation                   Fax: 408-845-6114
2500-5 Augustine Dr.        mailto:rtaborek@xxxxxxxxxxx
Santa Clara, CA 95054