What is MPLS-TP?
With the recent explosion of video-based applications, especially the cloud-first strategies IT departments are adopting, the expenses associated with continual expansion of the routing infrastructure itself have come under scrutiny.
MPLS-TP is one approach that can ease the continuous and growing expense of simply adding more and more routers to handle the burgeoning network load. MPLS-TP is a packet transport technology based on MPLS. Also known as IP/MPLS, MPLS is a protocol-agnostic IETF standard used to carry circuit and packet traffic over virtual circuits known as Label Switched Paths (LSPs). LSPs are created using Label Distribution Protocol (LDP), which builds the LSP based on the router IP routing table, making it an equivalent to a pure IP network. With MPLS, LSP from source to destination is predetermined and a ‘label’ is applied to it. The first (ingress) router inserts the label, intermediate devices forward traffic based on the label (without any IP lookups), and the final (egress) router removes it, forwarding the IP packet to its destination.
MPLS-TP is a packet transport technology that incorporates congruent paths, fault management, and network visibility.
In an MPLS network, LSPs are unidirectional, meaning traffic from source to destination and destination to source follow different paths. In contrast, an MPLS-TP network works congruently—that is, the paths traverse every segment of the network in both directions, making an MPLS-TP LSP deterministic, which allows for easier fulfillment of Service Level Agreements (SLAs).
With congruent paths, MPLS-TP enables communication back to the source. In addition to congruency, there are other differences between MPLS and MPLS-TP.
MPLS-TP applies constraints while eliminating some of the complex functions that make networks unpredictable and non-deterministic, including:
- Penultimate Hot Popping (PHP)
- LSP merge
- Equal Cost Multipath (ECMP) routing
MPLS-TP does maintain some essential MPLS functions, including MPLS Pseudo Wire (PW) emulation to provide virtual services like Virtual Private Wire Service (VPWS) and Virtual Private LAN Service (VPLS).
MPLS-TP addresses deficiencies in MPLS, providing carrier-class QoS, protection and restoration (sub 50ms), and OAM, by using deterministic methods to set up static LSPs that are congruent with predefined backup paths.
MPLS-TP uses Generalized MPLS (GMPLS) to utilize efficient forwarding using label switching, allowing deterministic and connection-oriented behavior, which makes it dependable.
MPLS-TP provides carrier-grade OAM for LSPs and PWs, which is the transport profile that gives MPLS-TP its name. With MPLS-TP, OAM is carried with the user traffic, ensuring faster trouble shooting and predicable carrier-grade performance.
Carriers that use MPLS-TP will derive greater value and deliver higher quality of service to their customers as they demand higher capacity, higher resiliency, and more visibility into the network.
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