[c-nsp] ATM over a Serial Interface question

[Scott Granados]

There are many cases when terminating a DSLAM with a single T1 makes sense.

You assumed that these were ADSL end users, they may not be.  We used this exact model in a previous gig to terminate a bunch of management interfaces on hardware or console servers.  There's lots of telemetry type applications where this setup is more than enough to meet the need.  Also, the DSLAMs I am familiar with (samsung, redback and nokia) can terminate DS3 or DS1.

On Jan 18, 2011, at 4:29 PM, Michael Sokolov wrote:

> Nick Voth <nvoth at estreet.com> wrote:
> 
>> We have a number of channelized DS3's that are terminating on to a 7206VXR
>> with the standard old PA-MC-T3 cards. We have a need to deliver ATM based
>> DS1's out to Adtran DSLAMs in the field. Customers will connect to the
>> Adtran units via ADSL and their local telco loop and their data is then
>> aggregated by the Adtran and on to the ATM based T1 coming back to us.
> 
> Let me see if I've understood you correctly: you are planning on feeding
> a whole DSLAM with a single T1?  In other words, the aggregated bandwidth
> usage of all subscribers you are going to serve is going to fit into a
> single 1.5 Mbps T1?  I thought today's spoiled ADSL users demand a heck
> of a lot more than that...  (The latter thought is based on my personal
> experience of the level of ridicule I get for promoting my beloved SDSL
> which also maxes out at 1.5 Mbps.)
> 
>> SO, my question is if we can deliver these circuits to the Adtran units
>> using the "encapsulation atm-dxi" on each serial interface. I know this
>> encapsulation is for delivering ATM through an ATM ADSU, but in this
>> application, does the far end Adtran function as the ADSU or are we missing
>> something on our end?
> 
> I invite someone from Cisco to prove me wrong, but my understanding is
> that "encapsulation atm-dxi" is another term for what's also known as
> ATM FUNI:
> 
> http://ifctfvax.Harhan.ORG/OpenWAN/l2conv.html
> 
> With ATM FUNI aka DXI the line carries HDLC frames which have the AAL5
> packets encapsulated in them, so the hardware is still HDLC.  True ATM
> over DS1, OTOH, would mean running actual 53-octet ATM cells over the
> DS1 bits, which calls for significantly different hardware.  I would
> expect that a DS1 feeding a DSLAM would need to be true ATM, but I'm not
> familiar with Adtran DSLAMs specifically.
> 
> (The DSLAMs which I do know want to be fed with DS3 or higher, not DS1,
> and they do want ATM cells over that DS3, not FUNI or DXI.)
> 
> HTH,
> MS
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