North American Network Operators Group

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Re: Network Topology

  • From: Jeff Weisberg
  • Date: Wed Mar 24 14:44:43 1999

| I need the expert advice from all of you in this issue since my experience
| is insignificant compared to some of the members of this list. In your
| experience what is better in terms of connectivity to the Internet. My boss
| wants me to order 4 T1's (maybe 6)  to different providers to be
| 'completely' sure that our NOC will 'always' be up & running. I've already
| got 2 T's right now,  I really don't know how' 'wise' it is to add another
| 4 or 6 from 'different' providers. Would it be better for us to get them
| from the same 2 upstreams we've already got?  Would it be better to get a
| Fractional T3?

it depends.

"better" is a very vague problem constraint. better how?

as far as the normal everyday happiness factor better, you will be
happier with a FT3 than you will be trying to load balance traffic
over 6 T1s (unless you are paid by the hour :-))

on the day that the backhoe convention comes to town, you will
be happier having N of M functional T1s than experiencing the
deafening wail of your users' "Is the T3 down?"

as far as your NOC "always" being up, there are important questions
you need to ask:
	is "always" 3 9s? 4 9s? 5 9s?
	if we are down, how much money do we lose?
	what are the various modes of failure? how likely are they
	to happen? how much does it cost to protect against?
	(there is probably a greater chance of a drunk driver smashing
	into the utilty pole outside your NOC, than for 3 ISPs to have
	a router failure at the same time. and an even greater chance
	that your CLEC's "redundant" sonet ring, isn't.)