Stack Management for MPLS Network Actions: Integration of Nodes with Limited Hardware Capabilities

Abstract: The MPLS Network Actions (MNA) framework enhances MPLS forwarding with a generalized encoding for manifold extensions such as network slicing and in-situ OAM (IOAM). Network actions in MNA are encoded in Label Stack Entries (LSEs) and are added to the MPLS stack. Routers have a physical limit on the number of LSEs they can read, called the readable label depth (RLD). With MNA, routers must be able to process a minimum number of LSEs which requires a relatively large RLD. In this paper, we perform a hardware analysis of an MNA implementation and identify the reason for a large RLD requirement in the MNA protocol design. Based on this, we present a mechanism that reduces the required RLD for MNA nodes by restructuring the MPLS stack during forwarding. We then introduce the novel stack management network action that enables the proposed mechanism as well as its integration in networks with MNA-incapable nodes. The feasibility of the mechanism on programmable hardware is verified by providing a P4-based implementation. Further, the effects on the required RLD, ECMP, and packet overhead are discussed.