**12. MPLS traffic engineering features**

1. **Explicit routes:** MPLS supports setting up of explicit routes, which can be an important tool for load balancing and satisfying other objectives so as to steer traffic away from particular paths. It is a very powerful technique which potentially can be useful for a variety of purposes. With pure datagram routing the overhead of carrying a complete explicit route with each packet is prohibitive. However, MPLS allows the explicit route to be carried only at the time that the label switched path is set up, and not with each packet. This implies that MPLS makes explicit routing practical. This in turn implies that MPLS can make possible a number of advanced routing features which depend upon explicit routing.

An explicitly routed LSP is an LSP where, at a given LSR, the LSP next hop is not chosen by each local node, but rather is chosen by a single node (usually the ingress or egress node of the LSP). The sequence of LSRs followed by an explicit routing LSP may be chosen by configuration, or by an algorithm performed by a single node (for example, the egress node may make use of the topological information learned from a link state database in order to compute the entire path for the tree ending at that egress node).

With MPLS the explicit route needs to be specified at the time that Labels are assigned, but the explicit route does not have to be specified with each L3 packet. This implies that explicit routing with MPLS is relatively efficient (when compared with the efficiency of explicit routing for pure datagram).

**Time-division multiplexing (time slot switching):** The forwarding mechanism is based on the time frames with several slots and data is encapsulated into the time slots (e.g.

**Fiber switching:** Here the switching granularity is a fiber. The networkings gears are fiber

The difference between MPλS and GMPLS is that the MPλS control plane focuses on Lambda switching, while GMPLS includes almost the full range of networking technologies.

1. **Explicit routes:** MPLS supports setting up of explicit routes, which can be an important tool for load balancing and satisfying other objectives so as to steer traffic away from particular paths. It is a very powerful technique which potentially can be useful for a variety of purposes. With pure datagram routing the overhead of carrying a complete explicit route with each packet is prohibitive. However, MPLS allows the explicit route to be carried only at the time that the label switched path is set up, and not with each packet. This implies that MPLS makes explicit routing practical. This in turn implies that MPLS can make possible a number of advanced routing features which depend

An explicitly routed LSP is an LSP where, at a given LSR, the LSP next hop is not chosen by each local node, but rather is chosen by a single node (usually the ingress or egress node of the LSP). The sequence of LSRs followed by an explicit routing LSP may be chosen by configuration, or by an algorithm performed by a single node (for example, the egress node may make use of the topological information learned from a link state database in order to compute the entire path for the tree ending at that egress

With MPLS the explicit route needs to be specified at the time that Labels are assigned, but the explicit route does not have to be specified with each L3 packet. This implies that explicit routing with MPLS is relatively efficient (when compared with the

**Lambda switching:** λ switching is performed by OXCs.

Fig. 4. GMPLS Label – Stacking Hierarchy.

**12. MPLS traffic engineering features** 

efficiency of explicit routing for pure datagram).

upon explicit routing.

node).

SONET/SDH).

switch capable OXCs.

Explicit routing may be useful for a number of purposes such as allowing policy routing and/or facilitating traffic engineering.


Fast reroute is a Multiprotocol Label Switching (MPLS) resiliency technology to provide fast traffic recovery upon link or router failures for mission critical services. Upon any single link or node failures, it could be able to recover impacted traffic flows in the level of 50 ms.

Backup path can be configured for:


Fig. 5. Link Protection V/s Node Protection

#### **13. References**


[1] J. Malcolm, J. Agogbua, M. O'Dell and J. McManus, "Requirements for Traffic

[2] T. Li and Y. Rekhter, "A Provider Architecture for Differentiated Services and Traffic

[3] M. Allman, V. Paxon, and W. Stevens. TCP congestion control. Request for Comments

[4] D. Awduche, J. Malcolm, J. Agogbua, J. McManus "Requirements for Traffic Engineering over MPLS (RFC 2702)" http://rfc-2702.rfc-list.net/rfc-2702.htm Sept 1999.

[6] L. Andersson, P. Doolan, N. Feldman, A. Fredette, B. Thomas "LDP Specification (RFC

[7] Li, T. and Y. Rekhter, "Provider Architecture for Differentiated Services and Traffic

[5] V. Alwayn, "Advanced MPLS Design and Implementation"ISBN 1-58705-020-X.

(Standards Track) RFC 2581 April 1999. URL:http://www.ietf.org/rfc/rfc2581.txt.

Engineering Over MPLS," IETF RFC 2702, September 2004.

Engineering (PASTE)," IETF RFC 2430, October 2006.

3036)" http://rfc-3036.rfc-list.net/ January 2001.

Engineering (PASTE)", RFC 2430, October 1998.

**13. References** 
