Purpose. The main purpose of the MPLS technology is to provide a basement for a new type of services that are not supported by the conventional routing. It is a major problem in the current situation of a tough competition when a provider needs to constantly offer new services in order to outrun the competitors.
The MPLS makes it possible to reduce the costs and to enhance the quality of the main services offered, as well as, to expand the routing functions. The classification of packets over a wide range of parameters makes it possible for an administrator to direct the traffic in advance, along his/her preferred and optimal choice.
The MPLS technology expands the traffic control capabilities, which leads to a more efficient network functioning, more predictable as well as flexible quality of service, which helps to increase the satisfaction of our customers’ needs.
MPLS supports the following services:
Technology description. In the IP networks, the router analyzes a header of every packet in order to determine a destination address; it also selects a path to the next router.
In the MPLS technology, ІР packets have additional small fixed-length ID labels. The labels act locally, being valid just on the way between two adjacent routers. Every router while sending a packet, it marks it with a different label. At the entrance of the MPLS network, the router checks whether the packet complies with a so called “Forwarding Equivalence Class” (FEC). Two packets are of the same FEC if they have similar characteristics and can be directed via the same path. Parameters determining FEC depend on router configuration. Generally, the destination ІР address is used for FEC determination. The use of the labeling considerably accelerates the packet delivery because, in this case, a new router does not have to analyze the IP packet headers, instead, it switches the packets based on their labels, which takes much less time.
Figure shows a diagram of an MPLS network with two types of routers:
Every LЕR in the MPLS network can serve as an input for some flows and as the output for the others. The input LER analyses headers of the packets arriving from outside, finds out the FECs they belong to, and directs the packets to respective LSRs. Having passed several LSRs, a packet arrives to an output LER which deletes the packet label, analyses the packet header and sends the packet to its destination outside the MPLS network.
A router chain (LERin, LSR, ... LSRn, LERout) passed by packets of the same FEC forms a Label Switched Path (LSР). Any LER can serve as an input one for some flows and an output one for others.