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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Network Topology
Here's my take on this. A lot of this is from personal experience. In the beginning, a lot of smaller ISP's/hosting companies (at least in our neck of the woods) start out with a single T1 to the internet. This seems to be up most of the time. However, you are dependent on the reliability of your upstream provider. Which may be good or not. Also, during backhoe season this is definately not good. The next logical step is to go to a pair of T1's to two different upstreams, taking pains to insure that the path is geographically diverse, so that a fiber cut or some "disaster" in one part of the country shouldn't affect both connections. >From there you have two options. The first is to add additional T1's to different providers. At this point, the law of diminishing returns has probably taken effect and any minor benefit to having 3 T1's is probably outweighed by trying to semi-balance traffic between all three providers. In fact, you'll probably find that it's almost impossible to get 3 T1's to not be significantly unbalanced. In addition, you chew more router memory and cpu by having the router deal with 3 (or more) views instead of just 2. I realize memory and CPU is cheap nowadays, but I seem to always be able to find some knob which I'd rather use than another BGP view. The other option is to get thicker Pipes to your 2 upstreams. This can either be muxed T1's to get 3.0 or 4.5 or more mb/s or some sort of FT3, depending on cost. My opinion is that this seems to be the more beneficial of the two options. You can scale each pipe up as the bandwidth on that pipe grows. This is also better internet wise as you end up being able to just say to the router "pick the optimum path" instead of saying "prefer a sub-optimum path so that things are well-balanced here". In addition, it permits flows greater than a single T1 would permit. There is one exception to my "only 2 upstream" opinion. That is that there comes a point where you find that a significant part of your bandwith is going through one of your upstreams to another provider. At that point, it may pay to get a pipe directly to that provider and either take only customer routes from them or accept some subset of routes such as those which must travel through them to get to their destination. This exception also applies when it becomes cost effective to just "peer" with those providers who will peer with you. If you'd like to discuss this further not-on-list, feel free to e-mail me directly. - Forrest W. Christian ([email protected]) ---------------------------------------------------------------------- iMach, Ltd., P.O. Box 5749, Helena, MT 59604 http://www.imach.com Solutions for your high-tech problems. (406)-442-6648 ----------------------------------------------------------------------
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