RE: Multi-link Frame Relay OR Load Balancing

["Rump Bryant" <rump_bryant () bah com>]

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