RE: Clock Tolerance and WAN PHY
Tom,
Do you see any justification in using this rather then POS?
I Mean:
If you compare the system {XGXS,PCS,WIS,PMA,PMD} + ELTE to a regular POS
system, you haev:
1.In the POS system you do not need the ELTE; You can directly connect to
the SONET network
2.All the world is talking POS today
3.There are components with I/F dedicated to POS which are different then
XGMII
The only advantage (I see) in WAN-PHY is that the encapsulation is more
efficient in terms of BW consumption from the SONET network.
Regards,
Boaz
> -----Original Message-----
> From: Tom Alexander [mailto:Tom_Alexander@xxxxxxxxxxxxxx]
> Sent: Monday, January 22, 2001 10:03 PM
> To: 'James Colin'; Luigi.Ronchetti@xxxxxxxxxxxxxxxx;
> tripathi@xxxxxxxxxxxx
> Cc: 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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