RE: [802.3ae_Serial] another question on pattertn defined in the current draft:
Juergen,
Draft 3.0 had said "In this mode, ... the WIS shall transmit a continuous
stream of all-zero data words to the PMA sublayer, and shall ignore all data
presented to it by the PMA sublayer." This meant zeroes on the line: zeroes
where the header would be and zeroes where the payload would be. I thought
that this could lead to optical power glitches and/or chattering optics and
even worse problems than you describe, so I suggested changing it to any
balanced pattern. It turns out that the pattern chosen by the group is
being proposed for the square wave test pattern for WAN PHY.
That's the history: I'll let the SONET experts debate the merit of AIS,
which I presume is balanced, or nearly so.
Piers
> -----Original Message-----
> From: Rahn, Juergen (Juergen) [mailto:krahn@lucent.com]
> Sent: 27 June 2001 10:28
> To: stds-802-3-hssg-serialpmd@ieee.org
> Subject: AW: [802.3ae_Serial] another question on pattertn defined in
> the current draft:
>
>
> Hi,
> Can somebody help me to understand why the pattern in case of
> Loop back is set to 00-FF?
> My question is was there a strong reason for this that I do
> not know. What I know is that there are some
> ugly effects possible with such pattern when the interface is
> connected to a Sonet or other type transport network.
> I understand that at the last meeting some work has been done
> on this loop back facilities. Now I read in
> 50.3.9 Loopback:
> ..............................................................
> ..............
> ...........................the WIS shall transmit a constant pattern
> to the PMA sublayer, and shall ignore all data presented to
> it by the PMA sublayer. The pattern output to
> the PMA transmit path at this time shall consist of a
> sequence of 8 logic zero bits and 8 logic one bits, form-ing
> the 16-bit word 00-FF hexadecimal. No SONET overhead or fixed
> stuff shall be output to the PMA at this time.
>
>
> While agreeing that the data incoming to the PMA sublayer
> should not be
> sent further such constant pattern is likely to generate some ugly
> additional
> effects . So maybe this would lead to undefined and miss
> leading alarms
> or( or even protection actions) in a possible transport network. This
> transport
> network that can either be a plane Sonet transport network, but also a
> traditional
> WDM network with Sonet non-intrusive monitoring or transport
> via an OTN. In all those
> cases the consequence on such patterns are not defined and
> the alarms that will
> be generated are likely to be miss interpreted. For instance
> it can be
> interpreted that a wrong signal is connected. In case a proper AIS is
> inserted however the transport network will react in the standardized
> way and no alarms (or even protection switches as worst case
> scenario)
> will be activated (which should not be done when a client
> equipment is in test mode).
> So can somebody help me with the reason for this pattern ( In
> contrast to a normal AIS
> that would not generate such effects). If there is no
> particular overriding reason for this
> I would strongly suggest to take the AIS signal instead.
> Regards Juergen Rahn
>
>