RE: [EFM] Network timing, ATM, ADSL/VDSL and EFM
Ariel,
It is interesting that you are calling "in-band" to the customer data, what
most people consider to be "out-of-band" management overhead. T1 framing is
equivalent to the 8b10b coding used by Fibre Channel and GbE. Is the 8b10b
coding of GbE "in band" to the MAC framing? T1 framing just so happens to
be time synchronous with the functionality that you refer to. It gives
North American service providers the ability to remotely manage and do
performance monitoring on the physical link in the last/first mile of
existing subscription network services. This is very critical for
businesses services that require and have the ability to pay for services
that justify deploying support infrastructure technology.
A 56k circuit is a T0, not a T1 and it does not have T1 framing. The
difference between a T1 and E1 is more related to the basic bandwidth
allocation. A basic T1 is ~1.5 Mb. A basic E1 is ~2 Mb. There is more
bandwidth in an SDH E1. That is the reason that a 64Kb service is
available in SDH and not for SONET.
Thank you,
Roy Bynum
At 10:25 PM 10/6/01 +0200, Ariel Maislos wrote:
>Roy,
>
>It's interesting that you mention T1/E1 framing for OAM.
>In previous mailings you mentioned the need not to damage the revenue
>generating bandwidth.
>T1 framing is an example of just the opposite!
>E1 framers use Time-Slot-16 as the OAM channel and Time-Slot-0 for
>synchronization, while T1 uses a bit-stealing mechanism for both. This is
>why you receive 56K links in T1 while E1 gives you 64K links.
>Food for thought...
>
>Ariel
>Passave
>
>-----Original Message-----
>From: owner-stds-802-3-efm@majordomo.ieee.org
>[mailto:owner-stds-802-3-efm@majordomo.ieee.org]On Behalf Of Roy Bynum
>Sent: Wednesday, October 03, 2001 5:08 PM
>To: mattsquire@xxxxxxx
>Cc: stds-802-3-efm@ieee.org
>Subject: Re: [EFM] Network timing, ATM, ADSL/VDSL and EFM
>
>
>
>Matt,
>
>What I am looking at are several separate factors. The existing T1/E1
>CSU/DSU logic is provided as a single "chip" from vendors, which means that
>technology can be further reduced in price by the increased production and
>yield of a more commodity market. T1/E1 framing is old technology that
>already provides some of the OAM requirements for supporting the physical
>infrastructure of an extensive diversity of services offerings. ( Where I
>am, I can get T1 bandwidths over DSL into my home from my DSL ISP, but
>today I have to run ATM to do it. ) This means that the PHY level framing
>technology can be adopted to new applications, particularly when used over
>the new copper and optical signaling technologies. For those silicon
>device vendors that are used to supporting the "service provider" market,
>this is not new "stuff". Adding some functionality for supporting minimal
>additional requirements over the higher bandwidth technologies should not
>be that difficult either. Once the PHYs are defined properly, how the
>different "box" vendors use that functionality will depend on the market
>sector that each will be targeting.
>
>Thank you,
>Roy Bynum
>
>Borrowing functionality from technology that already supports the require
>
>At 11:09 PM 10/2/01 -0400, Matt Squire wrote:
>
>
> > > It is also inexpensive. A T!/E1 CSU today costs less that what a GbE
>SMF
> > > PCI card does. If it had the commodity market that 10/100Mb Ethernet
>does,
> > > it would probably have much the same pricing, or lower.
> > >
> >
> >I have to question this expense argument. You're saying that a 1.5Mbps
> >copper T1 device costs less then a 1Gps fiber/optical component. Fine,
> >but I'm not sure why that's compelling. If we tried to make that same
> >device run 650 times faster and use optical components as a GbE SMF,
> >would that price comparison would hold up? I don't have any hard data
> >to pull out, but I'm guessing it wouldn't.
> >
> >- Matt