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dietaryfiber
dietaryfiber
12/4/2012 | 8:04:43 PM
re: PMC Offers 'Cerent Chip'
There is a standard for mapping DS0s into STS-1s. This is direct mapping and was intended for SONET when it was going to be a truly Synchronous Network.

DS0s are used for those very useful devices known as telephones.

dietaryfiber
gardner
gardner
12/4/2012 | 8:04:43 PM
re: PMC Offers 'Cerent Chip'
A couple of points. Number one, although STS1 is the basic module in SONET, an STS1 payload can be structured to carry VT1.5s (DS1s), thus it isn't really true to say that STS1s are "the smallest-sized pipes in Sonet networks". Number two, although there is a standard mapping to DS1 bit rates in SONET there is none for DS0s (there is no smaller VT than an VT1.5). Although one could extract the DS0s from the DS1 in the VT1.5 it is not something standard to SONET . This would seem to indicate that they are going it alone standards-wise. Comments anyone? (And I would also be anxious to hear of what use it is to a data network to break out such tiny pipes (64Kbps is pretty small)).
Ranger
Ranger
12/4/2012 | 8:04:41 PM
re: PMC Offers 'Cerent Chip'
I'm sure you would be offended it you were labelled as "Lite Wreeding".
Pauline Rigby
Pauline Rigby
12/4/2012 | 8:04:38 PM
re: PMC Offers 'Cerent Chip'
A late night editing error. I rushed to fix it this morning.

[email protected]
Peter Heywood
Peter Heywood
12/4/2012 | 8:04:37 PM
re: PMC Offers 'Cerent Chip'
In the cool light of morning, I decided to simplify the front end of this story - get to the point faster and cut out the stuff on the parallels with Ciena's CoreDirector.

For those of you who think you might have missed something, the business of Cerent getting a head start on the competition by developing its own ASICs has a parallel. Lightera did exactly the same thing and that's how Ciena ended up having a big success with the CoreDirector.

In the past few months, a number of chip vendors have brought out merchant silicon that's enabling folk like Sycamore and Nortel to get started on trying to catch up with Ciena.

So this now also has a parallel in the metro market, with PMC Sierra and Paxonet announcing Cerent type chips.

glowingduck
glowingduck
12/4/2012 | 8:04:33 PM
re: PMC Offers 'Cerent Chip'
I thought the same thing: why a DS0 (64 k) cross-connect fabric? Sure the 454 doesn't have a DS0 fabric, but fully-featured narrowband DCSs with SONET interfaces, in all shapes and sizes, have been around for years, AND they are cheap and plentiful. Any narrowband DCSs vendor will make you a DEAL today!

Is there a real market for this new chipset?

ivehadit
ivehadit
12/4/2012 | 8:04:32 PM
re: PMC Offers 'Cerent Chip'
peter,
you're creating unneccessary confusion for need of a catchy headline. cerent doesn't do ds0 processing, and neither do any cerent lookalikes plan on that.

even circuit switches now have sts-1 interfaces, however they need to break the signal down to ds0 before they can do the switching. is the application for this a circuit switch lookalike? or, ds0 crossconnects that sit in front of circuit switches to groom traffic into a circuit switch. perhaps ds0 frame relay circuits, is there anyone from pmc on this board that can clarify the true application?
lighthearted1
lighthearted1
12/4/2012 | 8:04:32 PM
re: PMC Offers 'Cerent Chip'
Is it possible that Astral Point and Mayan have proven that no one really cares about getting to the DS0 level within an edge/core box. They touted 3/1/0/ capability, but no takers.

The question that seems to come up most often is -
Do you dilute the cost of a high speed interface slot by using it for low speed applications?

In most cases it is simply cheaper to buy a managed, external 3/1/0 mux and use your high priced, multiservice chassis for the good stuff.
kww
kww
12/4/2012 | 8:04:31 PM
re: PMC Offers 'Cerent Chip'
I think that people will find that feature useful now that the mania for delivering 10GigE pipes to every home while losing billions in the process has calmed down.
The real problem with PMC's offering is that their "DS0 switching" feature is a sham. It requires byte-synchronous mapping of DS1 traffic before DS0 switching can work. Byte-synchronous mapping is so rare that the feature is virtually useless.
gardner
gardner
12/4/2012 | 8:04:28 PM
re: PMC Offers 'Cerent Chip'
There is a standard for mapping DS0s into STS-1s.

And what would that standard be? GR-253CORE? I don't think so. Look for yourself. Here is what GR-253CORE says: "The VT structure is designed for transport and switching of sub-STSG1 rate payloads. There are four sizes of VTs: VT1.5 (1.728 Mb/s), VT2 (2.304 Mb/s), VT3 (3.456 Mb/s), and VT6 (6.912 Mb/s)." Do you see 64Kb/s in that list? I didn't think so.

This is direct mapping and was intended for SONET when it was going to be a truly Synchronous Network.

Merely asserting there must be one doesn't cut it. Prove it by citing it chapter and verse. And while you are at it explain what you mean by "when it [SONET] was going to be a truly Synchronous Network".

DS0s are used for those very useful devices known as telephones.

This kind of flippancy doesn't improve your argument. Will I see you post here to tell me what standard defines a DS0 container for SONET or will you just slink away into the night like a smart aleck kid should?
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