Chapter 4 - From MPLS to GMPLS

Abstract

Generalized Multiprotocol Label Switching (GMPLS) is concerned with extending the MPLS concepts so that a uniform control plane can be applied to any transport technology including the MPLS packet-based data plane. The switching type of a network node defines the data units that the device can manage, and switch such as MPLS routers are packet switch capable (PSC) that can receive data on an interface, identify the packets in the data stream, and switch each packet separately. GMPLS recognizes a list of switching types that is consistent with the quantities that may be labeled. In MPLS, bandwidth—specifically bandwidth requested for an LSP—can be measured down to the finest granularity in bytes per second. The available bandwidth on a link may be divided in any way between the LSPs that use the link. In GMPLS transport networks, because an LSP is directly related to a physical and switchable resource, the bandwidth can only be divided up according to the capabilities of the switching device—this typically forces the bandwidth division to be in large units of bytes per second. LSP tunneling using hierarchical LSPs is an MPLS concept supported by label stacking but label stacks are only efficacious where shim headers are used to encode the labels. Various techniques such as the Hierarchical LSP (H-LSP) are needed in GMPLS signaling and routing to make hierarchical LSPs properly useful.