IGRP Composite Metrics
(D)elay, (B)andwidth, (R)eliability, (L)oad
- also includes (H)op-count and path MTU (these are not used in routing computation)
Delay: path length delay to each dest
Bandwidth: min across links to each dest
Reliability: measured (loss prob) [1..255]
Load: measured (loading) [1..255]