RE: Clock Tolerance and WAN PHY
Dave, Tom, James and all,
I apologize but it was not my intention to suggest you to directly
interface the WAN PHY to standard SONET/SDH network (I completely
agree with you all, ELTE is needed).
My intention was to make you aware of the new emerging standard that
defines OTN (Optical Transport Network) in ITU-T (G.709).
OTN is a "server layer" also for SONET/SDH services (i.e. for the
first time, SONET/SDH is a "client layer").
OTN is a "networking solution": it comprises its own performance
monitor, path provision, ... functions.
A CBR10G client signal (see my previous mail) is seen from OTN as a
constant bit rate stream.
I know that one 802.3 "philosophy" is to increase bandwidth by 10
with a cost increasing of only 3 or 4, for each new generation; I
wander if (for WAN interfaces only, not for LAN ones) it is convenient
to make today a "little" exception, to gain advantage from the above
mentioned new ITU-T standard.
Best regards,
Luigi
> -----Original Message-----
> From: dwmartin@xxxxxxxxxxxxxxxxxx [mailto:dwmartin@xxxxxxxxxxxxxxxxxx]
> Sent: Monday, January 22, 2001 11:11 PM
> To: james_colin_j@xxxxxxxxx; Ronchetti, Luigi /itah32;
> tripathi@xxxxxxxxxxxx
> Cc: dwmartin@xxxxxxxxxxxxxxxxxx; stds-802-3-hssg@xxxxxxxx
> Subject: RE: Clock Tolerance and WAN PHY
>
>
>
> James, Luigi,
>
> The 'ELTE' is also necessary to fill in the remaining SONET
> overhead.
>
> ...Dave
>
> David W. Martin
> Nortel Networks
> +1 613 765-2901
> +1 613 765-0769 (fax)
> dwmartin@xxxxxxxxxxxxxxxxxx <mailto:dwmartin@xxxxxxxxxxxxxxxxxx>
>
> -----Original Message-----
> From: Tom_Alexander@xxxxxxxxxxxxxx
> [mailto:Tom_Alexander@xxxxxxxxxxxxxx]
> Sent: Monday, January 22, 2001 11:12 PM
> To: james_colin_j@xxxxxxxxx; Ronchetti, Luigi /itah32;
> tripathi@xxxxxxxxxxxx
> Cc: Tom_Alexander@xxxxxxxxxxxxxx; stds-802-3-hssg@xxxxxxxx
> Subject: RE: Clock Tolerance and WAN PHY
>
>
>
> James,
>
> There is no intent or support for directly interfacing the
> WAN PHY to standard
> SONET gear, especially in outside plant applications. Off
> hand, I can think of
> the following obstacles, even if you did match the clocks:
>
> - The optics are completely different
> - Most of the overhead bytes are not supported (for instance, it
> would not be possible to provision the ring)
> - Much of the defects and alarm reporting is missing
>
> While it is certainly possible for someone to put back the
> missing overhead
> and defects and also use SONET optics rather than Ethernet
> optics, all this
> is totally outside the scope of the 802.3ae standard.
>
> Best regards,
>
> - Tom
>
> -----Original Message-----
> From: James Colin [mailto:james_colin_j@xxxxxxxxx]
> Sent: Sunday, January 21, 2001 12:54 AM
> To: Luigi.Ronchetti@xxxxxxxxxxxxxxxx; tripathi@xxxxxxxxxxxx
> Cc: stds-802-3-hssg@xxxxxxxx
> Subject: Clock Tolerance and WAN PHY
>
>
> Luigi,
> I think that the motto in the WAN PHY standard is the
> introduction of a new framing scheme (As opposed to
> POS), rather than being gluelessly connectable to the
> SONET network. The WAN PHY is supposed to be connected
> to a SONET LTE (ELTE) that is doing clock drift and
> jitter adjustments.
>
> Even if the WAN PHY Clock requirements were identical
> to those of SONET, I'm not sure if the ELTE is still
> needed or the WAN PHY can be directly interface to the
> SONET ring. Can anybody comment on that?
>
> James
>
> --- Luigi.Ronchetti@xxxxxxxxxxxxxxxx wrote:
> > Hi Devendra and all,
> >
> > I think that is not enough to reduce the clock
> > tolerance to 50ppm.
> >
> > As far as I know, ITU-T is going to approve
> > (February 2001) a new
> > recommendation (G.709) that defines OTN (Optical
> > Transport Network).
> > Future optical backbones over long distances will
> > likely to be realized
> > using G.709 and this will happen before 10 GbE final
> > approval.
> >
> > In G.709, among the others, a CBR10G client signal
> > is defined as "a
> > constant bit rate signal of 9953280 kbit/s +/-20
> > ppm" (for example an
> > OC-192/STM-64 signal and then, in principle, also a
> > 10 GbE WAN signal).
> >
> > So, in my opinion, at least for a 10 GbE WAN signal,
> > the clock
> > tolerance should be 20ppm.
> >
> > Best regards,
> > Luigi
> > __
> > \/ Luigi Ronchetti
> > A L C A T E L via Trento, 30 - 20059 Vimercate (MI)
> > Italy
> > TND R&D phone: +39-039-686.4793 (Alcanet
> > 2-210-(3)4793)
> > fax: +39-039-686.3590 (Alcanet
> > 2-210-(3)3590)
> >
> > mailto:luigi.ronchetti@xxxxxxxxxxxxxxxx
> >
> > > -----Original Message-----
> > > From: tripathi@xxxxxxxxxxxx
> > [mailto:tripathi@xxxxxxxxxxxx]
> > > Sent: Tuesday, January 09, 2001 10:50 PM
> > > To: stds-802-3-hssg@xxxxxxxx
> > > Cc: tripathi@xxxxxxxxxxxx
> > > Subject: Clock tolerance
> > >
> > >
> > >
> > > Hi,
> > >
> > > Right now we are specifying the clock tolerance of
> > 100 ppm. Currently
> > > in-expensive
> > > oscillators are available with tolerance value
> > less than 50
> > > ppm. Just like
> > > we are moving
> > > voltage levels, it is time we revise the tolerance
> > value too.
> > > The elastic
> > > buffer
> > > requirements get simplified by this assumption. I
> > propose
> > > that we reduce it
> > > to 50 ppm.
> > >
> > > Regards,
> > > Devendra Tripathi
> > > VidyaWeb, Inc
> > >
> >
>
>
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