On 25/Oct/17 20:47, Saku Ytti wrote:
> There are to principal IGP designs. One would be role based, where > metric is static depending on roles of A and B end of connection. Such > as P-P, P-PE, PE-PE. This strategy is well suited for networks where > hop count is similar to geographic distance or where network spans so > short geographic distance that it is not relevant. > This is very simple, requires almost 0 maintenance. If this works for > your topology, I high recommend it. > > Another strategy would be to encode latency cost to link, and always > choose lowest latency path. Hybrid could penalise for example P-PE > links, but otherwise use mostly latency on P-P, and document > exceptions. Particularly if you rely on strategic TE as opposed to > tactical TE, latency cost makes lot of sense, as then TE can find > next-lowest-latency path when you are out of capacity, and if you keep > monitoring paths which are not on SPT, you will know where you need to > buy more capacity. > If your network spans large geographic areas with lot of redundancy, > you will need this or hybrid, role based alone will cause too many > exceptions to document. > > Luckily SPF is super simple to implement, and I think there is even > free webtool for playing with costs. I've implemented both strategies at all ISP's I've built, i.e., device roles, where P-P links > P-PE links > PE-Metro links, e.t.c., as well as encoding latency into the IGP metric. Works beautifully, and as with Saku, I highly recommend it, as it's simple. Mark. _______________________________________________ juniper-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/juniper-nsp
