Synchronization in carrier class Ethernet

Synchronization in carrier class Ethernet
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Subject Author Date
Synchronization in carrier class Ethernet Michelot 03-31-2006
Posted by Michelot on March 31, 2006, 5:24 am
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Bonjour,

We used to say that PDH is plesiochronous and SDH is synchronous. These
concepts concern the timing for the TDM multiplexing, this allowing to
have higher capacities to carry the client data

What is the situation in a network transport that uses WAN Ethernet?

Ethernet multiplexing could be done through VLAN or MPLS. Can we say
that it is asynchronous multiplexing?

Thanks for your comments.
Regards,
Michelot


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Posted by anoop on March 31, 2006, 9:24 am
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Michelot wrote:

> Ethernet multiplexing could be done through VLAN or MPLS. Can we say
> that it is asynchronous multiplexing?

That would be a fair statement. There has been some work on the
support
of circuit emulation services over Ethernet which addresses some of the
issues around providing support for synchronous services over an
asynchronous infrastructure.
http://www.metroethernetforum.org/PDFs/WhitePapers/Introduction-to-CESoE.pdf


Posted by Michelot on March 31, 2006, 11:21 am
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Bonsoir anoop,

Thanks to recall me that interesting white paper. I just read it once,
and I probably have to read it several times... because of the age.

Perhaps we will see soon VoE (voice over Ethernet).

Regards,
Michelot


Posted by Albert Manfredi on March 31, 2006, 2:58 pm
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> Thanks to recall me that interesting white paper. I just read it once,
> and I probably have to read it several times... because of the age.
>
> Perhaps we will see soon VoE (voice over Ethernet).

Bonsoir Michelot. The paper Annop pointed out,

http://www.metroethernetforum.org/PDFs/WhitePapers/Introduction-to-CESoE.pdf

states requirements but not how they're going to be met. It seems to me
that if the Ethernet underlying service is much faster than the TDM or
otherwise synchronous service layered over it, this TDM over metro
Ethernet can be made to work. In the extreme, you could use GPS at the
source and at the destination, to regenerate clock. That would be a true
isochronous system (same clock through the net). If the Ethernet is fast
enough compared to what you're sending over it, the slack could be used
just like those stuffed bytes (whatever they're called) in SONET/SDH.

Albert


Posted by Michelot on April 1, 2006, 9:17 am
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Bonjour Albert,

Albert Manfredi a =E9crit :

> http://www.metroethernetforum.org/PDFs/WhitePapers/Introduction-to-CESoE.=
pdf
> states requirements but not how they're going to be met.

There are other documents more practical.

The Y.1413 (03/2004) recommendation from ITU-T explains how to transmit
TDM signals through MPLS networks not done for that.

RFC3985 dicuss how to emulate TDM services over packet switched
networks.

> It seems to me
> that if the Ethernet underlying service is much faster than the TDM

Even with rapid spanning tree, SDH with GFP will remain always faster
than Ethernet. The TDM signals are not only PDH or n x 16 kbit/s, but
also SDH and OTN.

> In the extreme, you could use GPS at the
> source and at the destination, to regenerate clock. That would be a true
> isochronous system (same clock through the net).

You're right, it is one of the four solutions explained in figure
10-2/Y.1413. You can have a same reference clock (e.g. GPS) at the
interworking function between the asynchronous network and TDM
synchronous network. And, by this way, to have a hierarchically
distributed and precise timing between the both TDM domains separated
by an asynchronous network.

> If the Ethernet is fast
> enough compared to what you're sending over it

Ok

> ...the slack could be used
> just like those stuffed bytes (whatever they're called) in SONET/SDH.

You want to define another SDH. And this case could be 10Gbase-W, with
SDH framing.

Best regards,
Michelot


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