 per ring UPSR for a Fully Meshed Four-Node No. of receive transponders per ring No. of protection switches per ring No. of switch arrays per ring No. of fiber pairs necessary 7.2 Approaches for ION 7.2.1 Control Plane Mechanism MPLS is a set of protocols developed during the past five years for provi- sioning and managing core packet networks (see Table 7-3). These protocols were originally developed for intranet applications. MPLS was developed as a packet-based technology and is seeing deployment in core IP-based net- works, including converged data and voice networks. MPLS does not replace IP routing, but works alongside existing and future routing tech- nologies to provide high-speed data forwarding between label-switched routers (LSRs) together with the reservation of bandwidth for traffic flows with differing QoS requirements. All-Optical Networks Table 7-3 Application IETF Document IETF MPLS Docu- ments Destination-based IP routing RFC3036 IP VPN RFC2547 Traffic engineering (RSVP-TE) draft-ietf-mpls-rsup-lsp-tunnel-09.txt Traffic engineering (CR-LDP) draft-ietf-mpls-cr-ldp-05.txt Diffserv traffic engineering draft-ietf-tewg-diff-te-reqts-01.txt Fast recovery draft-ietf-mpls-recovery-frmwrk-03.txt MPLS VPN multicast draft-rosen-upn-mcast-02.txt Optical draft-ietf-mpls-generalized-signaling-06.tx L2 transport draft-martini-l2circuit-trans-mpls-07.txt Interdomain RFC 3107 Networks that can be controlled by MPLS may be data-centric like those of enterprises or ISPs, voice-centric like those of traditional telecommuni- cations companies, or a converged network that combines voice and data. MPLS overlays a packet-switched IP network to support traffic engineer- ing. Specifically, it enables resources to be reserved and routes to be prede- termined. MPLS provides virtual links or tunnels through the network to connect nodes that lie at the edge of the network. For packets injected into the ingress of an established MPLS tunnel, normal IP routing procedures are suspended; instead, the packets are label switched s