Re: (ASCEND) 7.10.6 software for the DSL MAX 20

[Matt Holdrege <matt@ascend.com>]

The Terminator does support the feature called Bridged IP Routing (BIR),
which almost identical to Cisco's IRB. This feature was implemented 
specifically for that reason, where CPE equipment is a plain vanilla Bridge 
and the PC's traffic is bridged (CPE) and then switched (DSLAM) and finally 
bridging encapsulation is terminated on the Terminator and then routed.

Multiple customer premises share the same subnet and the Terminator has
one of its interfaces on that subnet.

Bridge groups is another feature that allows customer to create
"poor man's" VLANs by combining multiple bridged interfaces in
unique bridge group.

 > >Also, while the Terminator 100 appears to be able to handle 1000 dlci's,
 > >there is no mention of whether there are limits on the number of dlci's
 > >per T-1 interface.

Even if you consider SERIOUS oversubsription, I am not sure how practical 
is 1000 pvcs on 1 T1 line.


At 06:26 PM 12/22/99 -0800, Tony Ray wrote:
>Matt,
>
>Perhaps you know or can find out for me the answers to these questions.
>
>Currently I'm providing DSL (over Frame Relay from the DSLAM) and Frame
>Relay using Cisco equipment.  The feature Cisco has that I need and use
>is Integrated Bridging and Routing, irb.  I need to be able to bridge
>several DSL and Frame Relay pvc's together for telecommuting to offices
>and interconnecting offices between communities for customers.  I also
>need to place a routable interface on these bridge groups giving each
>their own subnet and access to the Internet.  Cisco's routers do this
>quite well, but I find I am limited to 120 dlci's per T-1 interface when
>the T-1's could easily handle three times their current traffic.  I'm
>also limited to 480 subinterfaces using irb.
>
>I have no control over customer premise equipment nor do I want to have
>it.
>
>I've read some of the documentation for the DSL Terminator 100 and,
>quite frankly, it doesn't appear to be able to do irb (but it may just
>be the way the documentation is written and its use of "Ascendese" when
>I speak "Ciscoese").  Under no circumstances do I want the ethernet port
>to be part of any bridge (which is what is done in the only example
>Ascend gives) - just a purely routed interface.  The Ascend
>documentation makes it sound as if separate "bridge groups" are not
>possible except between interfaces without it being clear what
>constitutes an interface.
>
>In a Cisco router, every dlci can be given it's own "interface" for
>routing purposes by creating serial subinterfaces, assigning each one
>its own dlci, assigning a (separate) bridge group to each serial
>subinterface (or group of subinterfaces) and placing a bridge virtual
>interface on the bridge group.  Considering the chain of things tied
>together to make this work in a Cisco router, I wouldn't be surprised if
>something like this isn't possible in the Ascend box but that is just
>isn't clear how to go about it from the documentation.
>
>Also, while the Terminator 100 appears to be able to handle 1000 dlci's,
>there is no mention of whether there are limits on the number of dlci's
>per T-1 interface.  I realize the size of the LMI packets places such a
>limit (but can't recall right off what that limit is).  Also, irb places
>a heavy load on the Cisco's processor so whether or not the Terminator
>100 can handle 1000 irb's (or equivalent profiles) is an equally serious
>question.
>
>Thanks,
>
>--Tony

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