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Re: Frame Relay encap vis-a-vis point-to-point at UUNET
- From: Dan Jones
- Date: Tue Sep 22 14:22:03 1998
See http://info.uu.net/tv/unite/low/hubs.html. It depicts Cascade
switches terminating 'customer leased lines'. They go so far as to draw
the FR cloud(s) separately, so it looks like the UUNET engineer was giving
it to you straight.
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
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.
At 02:09 PM 9/21/98 -0400, Barry L James wrote:
> We just got a third T1, this time through UUNet and when I looked
>at their router configuration I got a little surprise. We ordered a
>point-to-point circuit that is being terminated at their detroit POP. The
>configuration, however, sets up the line as a frame relay encap on a
>sub-interface (on a Cisco, of course :). When I talked to my UUNet rep he
>advised that this was the way "every large ISP did it" which I knew wasn't
>exactly true since our MCI and AT&T (just recently transitioned from the
>BBN backbone to the AT&T network) does not use this configuration. He
>insisted that it was still a point to point and that the frame relay
>encapsulation was used to enhance the connection.
>Well, I had him grab an engineer (he was an SE) that could possibly
>explain it better to me (since the SE said F/R was used to decrease RIP
>broadcasts across their backbone) and the engineer said this (basically):
>the circuit is terminated in a cascade 9000 f/r switch (used for port
>density) which went to a HSSI interface in a Cisco 7xxx series router
>which connected directly to their ATM network. Therefore, the f/r encaps
>were needed to speak with the cascade. The engineer advised we had a full
>CIR and would not suffer any bandwidth loss from using f/r encap.
>Now, I guess my question is: am I getting sold the brooklyn bridge here?
>I mean, not that I wouldn't like to *own* the brooklyn bridge (well, I'd
>rather have the triboro or the washington, but anyway...). Is this f/r
>encap going have any adverse affect on the quality of this connection
>(assuming that this is *NOT* a point-to-point into a frame cloud) or am I
>getting shoveled a load of copralite?
>Barry L James | Mikrotec Internet Services, Inc (AS3801)
>Director R & D | 1001 Winchester Rd
>email@example.com | Lexington KY 40505
>http://www.mis.net/ | 606/266.5925 800/875.5095
>Member AAAI, IEEE # 40277528
>Man will occasionally stumble over the truth, but most of the time he
>will pick himself up and continue on. -- Winston Churchill