Tuesday, June 1, 2021

Single-Metric Unequal-Cost Multipathing Is Hard

A while ago we discussed whether unequal-cost multipathing (UCMP) makes sense (TL&DR: rarely), and whether we could implement it in link-state routing protocols (TL&DR: yes). Even though we could modify OSPF or IS-IS to support UCMP, and Cisco IOS XR even implemented those changes (they are not exactly widely used), the results are… suboptimal.

Imagine a simple network with four nodes, three equal-bandwidth links, and a link that has half the bandwidth of the other three:

source https://blog.ipspace.net/2021/06/single-metric-ucmp-hard.html?utm_source=atom_feed

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