RE: [PWE3] comments on draft-ietf-pwe3-requirements-03.txt

[neil.2.harrison@bt.com]

Thanks...yes I know all this (I had a large hand in the E1 framing design
way back).  However, E1 and T1 are the foundation rates for the PDH....they
are not the foundation rates for the SDH or the OTN, that's all I
meant.....nothing more.

regards, Neil

> -----Original Message-----
> From: Yaakov Stein [mailto:yaakov_s@rad.co.il]
> Sent: 08 October 2002 09:17
> To: neil.2.harrison; stbryant
> Cc: pwe3
> Subject: RE: [PWE3] comments on draft-ietf-pwe3-requirements-03.txt
> 
> 
> 
> > E1 and T1 belong to PDH and only PDH.
> 
> Sorry Neil, but PLESIOchronous refers ONLY
> to multiplexing of sources with NEARLY (BUT NOT EXACTLY)
> the same clock (PLESIO is Greek for near or close).
> (See G.701)
> 
> PDH thus refers to the hierarchy of multiplexing schemes 
> that use with stuffing bits, e.g. E2,T2,E3,T3.
> 
> E1 and T1 mandate a single clock for all the DS0s they multiplex. 
> They are thus not PLESIOchronous by any stretch of the imagination. 
> They are simply synchronous (SYN means SAME).
> 
> Please do not fall into the same pit as someone did in
> a previous thread on this list, and claim that various ITU
> standards refer to E1 and T1 as PDH.  They don't.
> They use the term BASED ON the 1544 kbps or 2048 kbps hierarchy.
> The PDH hierarchy is BASED ON the E1 or T1 clocks,
> but the E1/T1 signals themselves are NOT PDH.
> 
> Y(J)S
> 
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