Re: [802.3ae] WIS defect conditions
On Mon, 8 Jul 2002 11:19:59 +0530 Anwar Shahab wrote:
> [ Gareth Edwards wrote: ]
> > In section 7.5 of ANSI T1.416-1999, Path AIS is defined as "an all ones
> > signal in H1, H1*, H2, H2*, H3 and the entire SPE". Does the SPE need
> > to be all ones for the whole frame to be classed as a path AIS frame,
> > or can one just assume that if all the header bytes are all ones, then
> > this
> > is path AIS?
>
> SPE also needs to be all ones for the interpretation of PAIS frame.
> It is very clear and has been implemented in many designs.
A point of clarification: for _sending_ Path AIS it is most definitely
necessary to set the SPE to an all 1s value. However, detection and
clearing of an AIS-P _defect_ is done by looking at the H1 and H2 bytes
only. See ANSI T1.231-1997 8.1.2.4.2.1 for details (T1.231-1997 is
incorporated by reference into T1.416-1999, which should not have
committed the cardinal sin of repeating some of the definitions (in some
cases with errors)).
//cmh