AW: [802.3ae_Serial] another question on pattertn defined in the current draft:
Hi,
The issue is that there is effectively no error in the Sonet Hierarchy but
one or multiple alarms (which could be very misleading) are raised in the
transport network and may be some K bytes in addition may be mis-interpreted
without any reason in this domain by a simple management action outside of
the transport section. I can agree if somebody states that AIS is not the
complete correct signal as this should be an Unequipped condition, however
AIS is the easiest signal that, avoids management interaction problems.
Regards Juergen
> ----------
> Von: Tim Warland[SMTP:twarland@nortelnetworks.com]
> Antwort an: Tim Warland
> Gesendet: Freitag, 29. Juni 2001 13:54
> An: Tom Alexander
> Cc: 'DAWE,PIERS (A-England,ex1)'; Rahn, Juergen (Juergen);
> stds-802-3-hssg-serialpmd@ieee.org
> Betreff: Re: [802.3ae_Serial] another question on pattertn defined in
> the current draft:
>
> Tom Alexander wrote:
>
> > Juergen and Piers,
> >
> > The decision to not send AIS upon loopback was made for the following
> reasons:
> >
> > <snip>
>
> > 2. The constant pattern, originally 00-00 but now 00-FF, does not
> correspond
> > to any SONET framing characters. Therefore, the far-end WIS will lose
> frame
> > synchronization almost immediately when the local WIS has been placed
> into
> > loopback. The effect will be similar to that of a failure of the WIS
> > (loss of framing). This is precisely the logical effect upon the far-end
> > WIS as a consequence of placing the local WIS into loopback;
> effectively,
> > the transmit path of the local WIS has been disabled or shut off by
> putting
> > it into loopback, and shutting off the WIS transmit path would have most
> > likely raised an LOF alarm at the far-end under normal circumstances.
>
> I agree with Tom (another good answer). I wanted to add that the error
> hierarchy for SONET/SDH has loss of signal (LOS) has the highest alarm
> followed by loss of frame (LOF) then Alarm Indication State (AIS).
> Forcing the WIS to output a 00FF has the affect of generating an LOF -
> that is: there is still a signal but the far end can not frame to it -
> which
> causes an alarm.
>
> Aside: the AIS condition is usually raised in response to an alarm
> condition. AIS is analogous to the RF (remote fault) condition.
> For 10GE, an RF is generated to the far end in response to an error
> which was detected between the far-end and the local termination.
> If the WIS were true to the SONET/SDH standard, upon receipt
> of an AIS it would ask itself what it had done to generate this
> condition. Whereas upon detection of an LOF, it would realize
> the problem exists in the far-end.
>
>
> --
> Tim Warland P.Eng.
> Hardware Design Engineer Broadband Products
> High Performance Optical Component Solutions
> Nortel Networks (613)765-6634
>
>
>