JUNOS High Availability

Chapter 16. Transitioning MPLS to a Multivendor Environment

Though not common in small and medium-size enterprise networks, Multiprotocol Label Switching (MPLS) has a long history (by Internet standards) of use by large enterprises and carriers. Forwarding traffic based on the content of an MPLS label table was originally viewed as faster than forwarding based on a longest-prefix match lookup in a routing table. However, with rapid advances in router hardware and the adoption of the radix tree structure for charting routing table content, the IP-based prefix match quickly caught up. MPLS would have been discarded had its clean separation between control and forwarding not been suitable for other purposes.

Network engineers are, by nature, power-hungry control freaks bent on dominating the traffic that transits their domain. Therefore, the notion of being able to configure paths through the network that allow selected streams of traffic to deviate from the Interior Gateway Protocol (IGP)-dictated “best path” is highly appealing. MPLS—when it is configured statically or deployed with a signaling protocol that supports traffic engineering—provides this functionality.

MPLS and the associated signaling protocols can also provide a means of separating selected traffic streams from other traffic transiting a network to create virtual private networks (VPNs). From a service-provider perspective, VPNs can be used to secure customer traffic streams, create multiservice infrastructures, and ...