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

Re: [802.3ae] ask some questions




t wrote:

> Sorry, I will ask some questions, and thanks for your helping.
>
> 1. 10GBASE-W PHYs operate at the STS-192 line rate of 9.95328 Gb/s,
> mapping the encoded
>     data stream at a 9.58464 Gb/s payload rate. The number "9.58464" is
> how to calculate?

Simply put, the WIS processor (necessary for 10GBASE-W) adds
3 columns of transport overhead to every 87 columns of data (for a
total of 90 columns for an STS-1). Then we add one column of path
overhead for every 3 groups of 90 columns (so for 192 groups
of 90 columns, we add 64 columns of path OH).    The math:

For OC-192, there are (3x192) = 576 transport OH, + 64 path OH
= 640 total OH. There are  ((87x192)-64)=16640 columns of data.
(That's 192 groups of 87 columns of data minus the path OH)
Data rate = 9.95328x((16640)/(16640+640))=  9.5846.
(That's the line rate multiplied by the ratio of data columns to
total columns)
(O.K. maybe it's not that simple)

>
> 2. In the 802.3ae spec, link fault signaling of XGMII functional
> specifications in Clause46,
>     what does "UCT" mean in figure46-9 (Link Fault signaling state
> machine, page256)?

A UCT is an UnConditional Transition. This means that the state machine
toggles from the previous state to the next state without any changes.

>
> 3.The 10GBASE-R PCS sends tx_data-unit<15:0> to the WIS at a nominal
> rate of 599.04Mhz
>    The number "599.04" is how to calculate?

This is easier:  The data rate in WIS mode is 9.58464Gb/s (from above).
Therefore the sixteen bit wide bus will run at 1/16th the data rate.
That is, 9.58464/16= 599.04

--
Tim Warland  P. Eng.
Applications Engineer
Quake Technologies   (613)270-8113 ext 2311

Tough Times don't last, tough people do