2 ms·
The internet "works" because, ultimately, core routers have adjacency to other core routers. Everyone propagates knowledge of their adjacency, and you end up h
by kev009 7y ago
The internet "works" because, ultimately, core routers have adjacency to other core routers. Everyone propagates knowledge of their adjacency, and you end up having complete paths to every other network.
A routing daemon speaks one or more routing protocol to build a table of routes. That can be used for various purposes, including programming the host's own routing table (bird runs on UNIX-like OSes) or other implementations can update a special kind of memory called a CAM (think something like a hashtable in silicon) an ASIC on a router/route switch uses.
Check wikipedia for BGP and peering and you should have what you desire.
- walrus01 7y agoBig ISPs connecting their core routers directly together with PNIs absolutely still happens, but in the modern era you see a lot more dedicated purpose aggregation and peering routers that are the AS-to-AS bgp neighbor relationship between ISPs that are in the same carrier hotel/same IX point. Often in a setup where the aggregation router has dual links to a pair of big core routers. The cores only speak bgp within their own AS. Or in a particularly big POP, a twin pair of agg routers connected in a X shaped topology to a pair of core routers.