IS-IS Metric Extensions

Two newly proposed LSP TLVs specify wider fields for the default metric, allowing larger interface metric values than the previous 63 maximum. This enhancement can be leveraged for basic IP routing, as well as MPLS-based traffic engineering applications. These new TLVs are as follows:

  • Extended Intermediate System Reachability TLV (Type 22)

  • Extended IP Reachability TLV (Type 135)

The Extended IS Reachability TLV is an extension of the Intermediate System Neighbors TLV (Type 2), and the Extended IP Reachability TLV extends the IP Internal Reachability TLV (Type 128). These TLVs take advantage of the fact that current and most widely deployed implementations of the IS-IS protocol do not support the QoS metric types, namely ...

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