3 quick notes-- Neither MLFR/FRF.16 (MCI's implementation) nor the corresponding CPE require external DSUs. The service may utilize internal DSUs (whether on Cisco CPE or Tasman) just as a tiered/fractional DS3 would. ATM-IMA could be considered wasteful of bandwidth as you would have to live with the ATM cell tax reducing usable bandwidth by about 25%. FRF.16 allows for much lower overhead through frame relay encapsulation. FRF.16 also allows for losing circuits within a bundle or even designating a threshold number of circuits for when to consider a link "down" (useful in failover scenarios). Another minor point is that DS3s are tiered by many large providers through timing at the provider edge DSU/linecard vs. CIR (even though FR encaps may be used). Given all that, a fraction DS3 may still be a better option if the telco loop is reasonable... Bryant Rump Advanced Internetworking Booz Allen Hamilton rump_bryant@bah.com -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Jeff Kell Sent: Thursday, September 16, 2004 10:55 PM To: Scott McGrath Cc: Bryce Enevoldson; nanog@merit.edu Subject: Re: Multi-link Frame Relay OR Load Balancing Scott McGrath wrote:
In my experience the breakeven point for a Frame Relay DS3 is 6 DS1 circuits. DS3's tend to be more reliable than DS1's as the ILEC usually installs a MUX at your site instead of running to the nearest channel bank and running the T1's over copper with a few repeaters thrown in for good measure.
I'll second that. Our ILEC extended our existing SONET node (for the PBX in another building) to our machine room (couldn't push DS3 over copper that far). Now, if they'd just terminate the old T1s at the new node and not push them over local copper from there to the machine room, we would be sitting pretty.
Another nice thing about DS3's is that it is easy to scale bandwidth in the future by modifying the CIR on your link. Another feature is that since the link is faster the serialization delay is lower which will give you better latency and last but not least PA3+ for Cisco 7[2|5]xx routers are inexpensive and give you one call for service not a separate call for the CSU/DSU's and the serial line card you need to support a multilink solution.
Ditto. We have one in a 7204 with a CIR of 30Mb. Handles it quite nicely, replaced 5 T1s on load-sharing per-packet link. Jeff