Radu-Adrian Feurdean wrote on 5/17/2019 5:10 AM:
On Thu, May 16, 2019, at 16:38, Blake Hudson wrote:
offloading that responsibility onto the transit provider. IMHO, what's the point of being multi-homed if you can't make intelligent routing decisions and provide routing redundancy in the case of a transit provider outage? Speaking of "intelligent routing", this is why doing some targeting on what you filter by some criteria other than prefix or as-path length is a good idea. Either manually every once in a while (just make sure that you at least check the situation every few weeks), or in an automated manner (better). You just need more data (usually *flow/ipfix based) in order to be able to take the good decisions.
You can use traffic levels (or better - lack of traffic), traffic criticality (?!?! cirticity ?!?!) and prefix count saving as criteria.
-- R-A.F.
From my perspective one's ability to intelligently route IP traffic is directly correlated to the data they have available (their routing protocol and table). For example, with static default routes one can only make the simplest of routing decisions; with dynamic default routes one can make more informed decisions; with a partial view of the internet one can make even better decisions; with a full view of the internet one can make good decisions; and with a routing protocol that takes into account bandwidth, latency, loss, or other metrics one can make the very best decisions. Determining how intelligent one wants his or her decisions to be, and how much he or she is willing to spend to get there, is an exercise for the reader. Not all routers need a full view of the internet, but some do. The cost of routers that hold a full routing table in FIB is generally more than those that do not, but overall is not cost prohibitive (in my opinion) for the folks that are already paying to be multihomed. Single homed networks (or those with a single transit provider and additional peers), probably won't benefit from holding more than a default route to their transit provider and therefore may be able to get by with a less capable router. Each network is different and the choices driven by the needs for redundancy, availability, performance, and cost will come out differently as well.