Re: [nsp] Multiple T1s versus MLPPP

From: Jim Warner (warner@cats.UCSC.EDU)
Date: Tue Feb 13 2001 - 14:54:57 EST


The original question from Martin Picard:

> I have two routers with 8-T1 interfaces.
> How much benefit do I have by using MLPPP
> to bundle them instead of using separate
> serial interfaces ?

A partial answer from Phil Bedard:

+ The router won't balance more than 6 parallel paths I believe, so
+ the only real option is MPPP.

The load balancing schemes other than MLPPP (i.e. CEF):

   Per-packet load balancing allows the router to send data packets over
   successive equal-cost paths without regard to individual destination
   hosts or user sessions. Path utilization is good, but packets destined
   for a given destination host might take different paths and might arrive
   out of order.

   -- or --

   Per-destination load balancing allows the router to use multiple,
   equal-cost paths to achieve load sharing. Packets for a given source-
   destination host pair are guaranteed to take the same path, even if
   multiple, equal-cost paths are available. Traffic for different source-
   destination host pairs tend to take different paths.

 [above quotes from cisco docs]

If you need to be able to deliver all of your collected bandwidth
to a single TCP connection (e.g. backups running late at night) without
reordering packets, you want to use MLPPP or AIM.

AIM ("A" stands for ATM) makes the collected T-1s look like a single big
pipe, but incurs the cell header overhead of ATM, the expense of very
fancy interface cards, and the cost of ATM ports from your LEC.

jim warner
UC Santa Cruz



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