**11.1 MPLS traffic engineering architecture**

Multiprotocol label switching (MPLS) is a hybrid technology that provides very fast forwarding at the cores and conventional routing at the edges. MPLS working mechanism is based on assigning labels to packets based on forwarding equivalent classes

(FEC) as they enter the network. A FEC identifies of a group of packets that share the same requirements for their transport. All packets in such a group are provided the same treatment en route to the destination.

Packets that belong to the same FEC at a given node follow the same path and the same forwarding decision is applied to all packets. Then packets are switched through the MPLS domain using simple label lookup. Each FEC may be given a different type of service. At each hop, the routers and switches use the packet labels to index the forwarding table to determine the next-hop router and a new value for the label. This new label replaces the old one and the packet is forwarded to the next hop. As each packet exits the MPLS domain, the label is stripped off at the egress router, and then the packet is routed using conventional IP routing mechanisms.

The router that uses MPLS is called a label switching router (LSR). A LSR is a high speed router that participates in establishment of LSPs using an appropriate label signaling protocol and high-speed switching of the data traffic based on the established paths.

MPLS-TE has the following components and functionalities, as shown in Figure 2:


enhance classic IP with virtual circuit-switching technology in the form of label switched

Then, IETF proposed an extension to the MPLS-TE control plane to support the optical layer in optical networks; this extension is called the Multiprotocol Lambda Switching (MPλS) control plane. Another extension to MPLS was proposed to support various types of switching technologies. This extension is called Generalized Multi- Protocol Label Switching (GMPLS). GMPLS has been proposed in the Control and Measurement Plane working group in the IETF as a way to extend MPLS to incorporate circuit switching in the time,

Multiprotocol label switching (MPLS) is a hybrid technology that provides very fast forwarding at the cores and conventional routing at the edges. MPLS working mechanism is

(FEC) as they enter the network. A FEC identifies of a group of packets that share the same requirements for their transport. All packets in such a group are provided the same

Packets that belong to the same FEC at a given node follow the same path and the same forwarding decision is applied to all packets. Then packets are switched through the MPLS domain using simple label lookup. Each FEC may be given a different type of service. At each hop, the routers and switches use the packet labels to index the forwarding table to determine the next-hop router and a new value for the label. This new label replaces the old one and the packet is forwarded to the next hop. As each packet exits the MPLS domain, the label is stripped off at the egress router, and then the packet is routed using conventional IP

The router that uses MPLS is called a label switching router (LSR). A LSR is a high speed router that participates in establishment of LSPs using an appropriate label signaling

1. The routing protocol (e.g. OSPF-TE, IS-IS TE), collects information about the network connectivity (this information is used by each network node to know the whole topology of the network) and carries resource and policy information of the network. The collected information is used to maintain: The so-called Link-state database which provides a topological view of the whole network and the TE database which stores resource and link utilization information. The databases are used by the path control component. A constrained Shortest Path First (CSPF) is used to compute the

2. A signaling protocol (e.g. RSVP-TE or CR-LDP) is used to set up LSP along the selected path through the network. During LSP setup, each node has to check whether the requested bandwidth is available. This is the responsibility of the link admission control that acts as an interface between the routing and signaling protocol. If bandwidth is available, it is allocated. If not, an active LSP might be preempted or the LSP setup fails.

protocol and high-speed switching of the data traffic based on the established paths. MPLS-TE has the following components and functionalities, as shown in Figure 2:

based on assigning labels to packets based on forwarding equivalent classes

path (LSP). MPLS is well known for its TE capability and its flexible control plane.

frequency and space domains.

**11.1 MPLS traffic engineering architecture** 

treatment en route to the destination.

routing mechanisms.

best path.

Fig. 3. MPLS-TE functional components.
