MPLS Network Action for Entropy

Load balancing is a powerful tool for engineering traffic across a network. The use of entropy labels within MPLS was first described in and has been deployed succesfully in multiple MPLS networks. With the emergence of MPLS Network Actions , there is a significant benefit to being able to describe entropy as a network action. Without this, a packet that required load balancing and network actions would need to deal with the complexity and overhead of both the MNA and Entropy Labels in the label stack. By defining an action for Entropy within the MNA infrastructure, overhead and complexity can be reduced.

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “NOT RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in BCP14 when, and only when, they appear in all capitals, as shown here.

Name: Entropy Action Network Action Indication: The Entropy Action is opcode TBA1. Scope: The Entropy Action is valid in Hop-by-Hop (HBH) and Select scopes. In-Stack Data: The Entropy Action carries 20 bits of ancillary data, known as the Entropy Value. The semantics of the Entropy Value are identical to the semantics of the Entropy Label as found in , but the Entropy Value is not found in the Label field of the Label Stack Entry (LSE). While the RFC 6790 Entropy Label has some restrictions to avoid collisions with the reserved label space (0-15) , those restrictions are not necessary for the Entropy Value and do not apply. A forwarding node should incorporate the Entropy Value into its forwarding decision when the Entropy Action is evaluated. Post-Stack Data: None. The Entropy Action does not appear in post-stack data.

The forwarding plane is insecure. If an adversary can affect the forwarding plane, then they can inject data, remove data, corrupt data, or modify data. MNA additionally allows an adversary to make packets perform arbitrary network actions. Link-level security mechanisms can help mitigate some on-link attacks, but does nothing to preclude hostile nodes.

This document requests that IANA allocate a codepoint (TBA1) from the MPLS “HBH and Select In-Stack MPLS Network Action Indicator Opcodes” from the “IETF Review” range for the Entropy Action. The allocation should reference this document.