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Re: Frame Relay encap vis-a-vis point-to-point at UUNET

  • From: Dan Jones
  • Date: Tue Sep 22 16:37:09 1998

You've hit the proverbial nail on the head.  But there is a
customer-perception story to be told here.  I think most customers realize
that any provider's backbone is overbooked at some level.  Most backbone
links are probably not as large as the sum of all customer connections
coming in.  That's packet switching for you.

But I think most T1 customers think that they are getting a full T1 from
their location to the edge of the provider's backbone.  What the model at
hand (and emerging connectivity models like cable modems & xDSL) are doing
is pushing the definition of 'edge' closer to the customer.  In addition to
general backbone congestion, now the customer has to contend with
congestion in their neighborhood (cable head-end or xDSL DSLAM).

That's fine for Frame Relay customers since they presumably understand what
FR is all about & can choose their CIR/port speed wisely.  But I tend to
think that a customer who purchases a pt-pt T1 to reach their provider's
network wants the full T1 all the way to the router on the other end.
It'll be intersting to see if xDSL etc manages to change that expectation.

Dan



At 02:32 PM 9/22/98 -0400, Vijay Gill wrote:
>On Mon, 21 Sep 1998, Dan Jones wrote:
>
>> 	However, the statement 'would not suffer any bandwidth loss from
>> using f/r encap' is largely dependent on the overbooking of those
>> aggregation ports.  If it were me, I would a) make sure that 'full CIR'
>> meant line speed & b)  want an assurance that the aggregation ports were
>> >= the sum of all line speeds mapped to them.  Otherwise, one could very
>> well argue that those connections are not pt-pt at all but FR clouds
>> collapsed onto an on-site FR switch. 
>> 
>> 	If there is any overbooking going on on those aggregation
>> connections, you are not getting your T1's worth and might as well have
>> bought a FR connection in the first place. 
>
> The point where the congestion and overbooking takes place might be
>anywhere along the source/destination pair.  Assuming provider A was
>aggregating customers directly onto CT3 cards instead of frame relay
>switches.  
>
>The customer is now happy with his "point to point link."  Now, further
>assuming the uplink from the customer aggregation equipment, to the
>backbone transist system is worth X Mbps, then directly terminating a
>number of connections onto the gateway with an aggregate _peak_ bandwidth
>of greater than X Mbps just moves the choke point up further, to the
>transist <--> Customer aggregation equipment link. This can be moved up to
>any point in the network.
>
>This is where aggresive monitoring and proactive retermination and/or
>addition of more resources come in.
>
>--
>Vijay Gill                         |The (paying) customer is always right.
>wrath@cs.umbc.edu, vijay@umbc.edu  |                  - Piercarlo Grandi
>http://www.gl.umbc.edu/~vijay      | Eagles may soar, but weasels don't get
>These are my opinions only.        | sucked into jet engines.
>
>




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