[c-nsp] Dual OC3 - Separate Carrier - Load-balancing 7201

[Justin M. Streiner]

On Mon, 4 Apr 2011, Mark Mason wrote:

> We are planning on terminating dual OC3 point-to-point circuits 
> (PA-POS-2OC3) from different carriers on 7201 NPE-G2's at two of our 
> DC's and do either HDLC CEF per packet load-balancing or multilink PPP 
> bundle together. What are some of the questions and responses from the 
> field for anyone who has done this type of setup?

I would stay away from per-packet load-sharing in this design, unless 
there is a really compelling reason to use it.  The biggest reason to 
stay away is that OC3 (technically, OC3c) circuits from different 
carriers to the same locations could have vastly different end-to-end 
latencies.  If they are significantly different, dealing with packets 
arriving out of order could be a major headache, and throughput could 
suffer greatly.

You might also want to look at a Gigabit Ethernet solution, if that's an 
option and you're not chained to a POS design.  The operating costs of a 
pair of gig-e circuits could very well be substantially lower than a pair 
of OC3cs, with the added benefit of being able to provide a lot more 
bandwidth.  If you were to get two gig-e circuits, the caveat above 
related to per-packet load-sharing would still apply.

In a POS world, if you need more than 155 Mb/s, you either 
need to install another POS circuit, or start upgrading to OC12c or 
higher.  That also throws in the need to purchase new router hardware, 
because the 7201 won't handle a POS OC12c, so your costs per megabit 
wouldn't scale too well.

jms