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It was still widely used for IPv4 and v6 in 2000s. ex telco engineer told us that two major reasons was that IS-IS was simply more efficient, and that they didn
by p_l 2y ago
It was still widely used for IPv4 and v6 in 2000s. ex telco engineer told us that two major reasons was that IS-IS was simply more efficient, and that they didn't require IP communication between routers - meaning troubleshooting and management was easier than providing p2p routes for IP-based protocols.
- Hikikomori 2y agoIt's still widely used, among old ISPs because why switch when it's just as good or better than the alternative and your engineers know it best. But it's not the whole stack as implied in the first reply. It was popular primarily because OSPF didn't scale well with hundreds to thousands of routers with the minimal CPU power even large core routers had.
- p_l 2y agoScalability was one part. Later the fact that you didn't need separate routing setup for v6 also was part of it. But for a telco, the fact that you didn't have to setup IP connectivity in order for routers to see each other, was also a crucial ability.
- Hikikomori 2y agoOSPF has supported unnumbered links for a long time, don't need IP on the link with point to point and multicast.
- p_l 2y agoUnnumbered just means you have no IP address exclusive to the link. IS-IS works without establishing IP connectivity at all, not just about tricks to handle leaky internals. This also meant autoconfiguration or supporting non-ip protocols (like routed ethernet) is simpler, though I will admit that OSPFv3 adding default use of link local V6 for router interfaces made the gap smaller.