Synchronization in carrier class Ethernet
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Posted by Michelot on March 31, 2006, 5:24 am
Please log in for more thread options 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
Please log in for more thread options Michelot wrote: 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 | |||||||||||||
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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 | |||||||||||||
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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 | |||||||||||||
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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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> that it is asynchronous multiplexing?