smir@PacBell.COM (Sonu Mirchandani) (04/05/89)
I had asked for information regarding direct T1 interfaces to
Routers. I also said that if there was enough interest I would
summarize. Well...there was a pretty decent amount of interest
and here's the summary.
SUMMARY:
The request is in context to the setup as shown below:
------------+ +-----------+
| |Router | |
|Router |Backplane | Digital |
| |----------+ +--------+ | Cross |
|___________|__T1 card_| | DSU____| | Connect |
V.35 4-wire +-----------+
ALL THIS EQUIPMENT IS IN ONE ROOM, PRETTY CLOSE TO EACH OTHER
Today: The connection from the Router is a V.35 interface (could be
56kb or T1 speeds). This is then connected to the DSU. On the
other side of the DSU the signal comes out 4-wire bipolar DSX-1.
This is then connected to one of the ports on the Digital
Cross-connect System (DCS). For the purpose of this discussion
let us call the Router T1 interface an external T1 interface.
What we'd like to do:
We would like to use a T1 card for the Router that provides
the T1 signal not as V.35 but as a 4-wire bipolar DSX-1
which can then be directly connected into the DCS. That
will save us the cost of the DSU by interfacing
directly between the DSX-1 and the router backplane,
avoiding the intermediate V.35 conversion.
For the purpose of this discussion, let us call this an
integrated T1 interface.
------------------------------------------------------------------------------
THE FOLLOWING IS A SUMMARY OF THE RESPONSES THAT WERE SENT TO ME.
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The responses were fairly mixed. A number of responses
indicated that an integrated T-1 interface sounded
desirable, while one indicated that the external T-1
interface was not that big of a cost concern. Wellfleet was
identified as a vendor that was providing an integrated T-1
interface, but it did not appear to offer a cost advantage
over the external interface, indicating that they are probably
just packaging a CSU in their box. Another possible vendor
was mentioned (vaguely).
One response indicated that the phone company liked to see
external T-1 interface boxes (i.e. DSU/CSUs) when interfacing to
their lines. That is true, but in this case I too, am a user of the
DCS, which is on my premise (see diagram above).
I was made aware of an integrated circuit company that was
developing an IC for providing the T-1 interface. This type
of device should allow the router folks to build direct T-1
interfaces with a substatial cost savings over the separate
CSU/DSU arrangements (Dallas Semiconductor is the company name).
Of course, there are instances where the DCS/T1 mux or a
that you would plug the Router into. However, in most other cases
they are expecting a 4-wire DSX-1 bipolar T1 signal (which is
what we have and would like to connect our Router directly to).
In summary, it sounds like there is a fair amount of
interest in a direct T-1 interface, and it appears that the
integrated circuits are becoming avaialable to make that
feasible. It sounds like users need to let the router
vendors know that they would like to see this sort of thing.
Thanx for the info from all of you out there. I appreciate
your feedback.
Sonu Mirchandani
Pacific Bell
smir@pacbell.com
(415) 823-8908
"Standard disclaimer...."