MPLS Technology Details
This section examines how MPLS facilitates the development of service types, such as Layer 3 VPNs and traffic engineering. Figure 3-7 depicts the MPLS advanced service architectural components that include Layer 3; traffic engineering; differentiated services; Layer 2 VPNs; Virtual Private LAN Service (VPLS); IPv6, multicast GMPLS; and the key control protocols, such as Label Distribution Protocol (LDP), BGP, RSVP, and so on, that activate these service functions. As mentioned previously in this chapter, one of the key benefits of the MPLS architecture is the separation into two planes—one containing information required to transfer a packet (the data plane) and the other allocating the transfer information (the control plane). This separation permits applications to be developed and deployed in a scalable and flexible manner.
Several applications that are facilitated by the implementation of MPLS include:
- MPLS QoS—Implements quality of service mechanisms, such as differentiated service, which enables the creation of LSPs with guaranteed bandwidth.
- Layer 3 VPN—Uses BGP in the service provider's network with IP routing protocols or static routing between the service provider and the customer. The BGP protocol is used to exchange the FEC-label binding.
- Traffic engineering—Uses extensions of IS-IS or OSPF to distribute attributes in the network. Control processes the FEC-binding through RSVP. Traffic engineering enables you to control traffic routing and thus optimize network utilization.
- Multicast routing via PIM—The protocol used to create FEC tables; extensions of version 2 of the PIM protocol are used to exchange FEC–label binding.
- Layer 2 VPN—Can be created via a Layer 2 circuit over MPLS, commonly referred to as Any Transport over MPLS. Layer 2 VPNs, therefore, use Layer 2 transport as a building block to construct a Layer 2 VPN service that includes auto configuration, management, QoS, and so on.
The sections that follow focus on the technology details for a base of these services, such as Layer 3 VPNs, traffic engineering, differentiated services, and Layer 2 VPNs. Multicast, IPv6, and GMPLS are discussed in later chapters.
Figure 3-7 Architecture for Advanced Services