RE: [EFM] Network timing, ATM, ADSL/VDSL and EFM
Sorry Ariel, I think you have mis-interpreted some of the technical details
here.
In E1 TS16 is used for common channel signalling, and in T1 the bit robbing
CAS (that cuts 64k down to 56k) is also for PSTN signalling. It might be
used for OAM in DDS services. Call control is a layer two data link and
layer three and above call control function and is analogous to IP within
the payload in EFM, and not an equivalent of OAM.
In T1 the 193rd bit is used for sync and the OAM channel in a superframe
mechanism (16 frames give you two bytes, six bits of which are the OAM / FDL
channel).
In E1 TS0 is used for sync, and although there are National and
International Bits that could be used for OAM there is no ITU specification
for how most of them should be / could be used, and no common implementation
certainly not in the UK. The only spec. that is defined is for alarm bits.
The UK E1 uses a wrapper round the E1 within the telco (ILEC / BT) network,
this includes a side band for OAM, so OAM it is totally disconnected from
the 2048kbit/s stream. This actually supports the case for side-band, as
there are good reasons for doing what they do :-). 64k in the UK gets
delivered as two wire bi-direction simplex at 256k, or using 2B1Q in newer
systems. Both have OAM in side bands.
Best regards
Bob
> -----Original Message-----
> From: owner-stds-802-3-efm@majordomo.ieee.org
> [mailto:owner-stds-802-3-efm@majordomo.ieee.org]On Behalf Of Ariel
> Maislos
> Sent: 06 October 2001 21:26
> To: Roy Bynum; mattsquire@xxxxxxx
> Cc: stds-802-3-efm@ieee.org
> Subject: RE: [EFM] Network timing, ATM, ADSL/VDSL and EFM
>
>
>
> 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
>