MPLS Overview


Multi-Protocol Label Switching (MPLS) defines a mechanism for packet forwarding in network routers. It was originally developed to provide faster packet forwarding than traditional IP routing, although improvements in router hardware have reduced the importance of speed in packet fowarding. However, the flexibility of MPLS has led to it becoming the default way for modern networks to achieve Quality of Service (QoS), next generation VPN services, and optical signaling.

Traditional IP networks are connectionless: when a packet is received, the router determines the next hop using the destination IP address on the packet alongside information from its own forwarding table. The router’s forwarding tables contain information on the network topology. They use an IP routing protocol, such as OSPF, IS-IS, BGP, RIP or static configuration, to keep their information synchronized with changes in the network.

MPLS also uses IP addresses, either v4 or v6, to identify end points and intermediate switches and routers. This makes MPLS networks IP-compatible and easily integrated with traditional IP networks. However, unlike traditional IP, MPLS flows are connection-oriented and packets are routed along pre-configured Label Switched Paths (LSPs

How does MPLS work?
MPLS works by tagging packets with an identifier (a label) to distinguish the LSPs. When a packet is received, the router uses this label (and sometimes also the link over which it was received) to identify the LSP. It then looks up the LSP in its own forwarding table to determine the best link over which to forward the packet, and the label to use on this next hop.

A different label is used for each hop, and it is chosen by the router or switch performing the forwarding operation. This allows the use of very fast and simple forwarding engines, as the router can select the label to minimize processing.

Ingress routers at the edge of the MPLS network use the packet’s destination address to determine which LSP to use. Inside the network, the MPLS routers use only the LSP labels to forward the packet to the egress router.

source: http://www.dataconnection.com/mpls/whatis.htm

ANOTHER GOOD EXPLANATION OF MPLS:

MPLS refers to the technological operation that is more properly known as multi-protocol label switching. Essentially, MPLS is an operating scheme that is used to speed up the flow of traffic on a network by making better use of available network paths. The main thrust of the idea is to define or designate the proper path for each function so that the opportunity for bottlenecks within the network are minimized.

The concept of MPLS was the brainchild of the Internet Engineering Task Force, or IETF. As the need for handling more traffic on networks connected to the Internet became apparent, the concept of establishing labels in packets that would control the flow and destination of data was understood to be a solution to the issue. MPLS made good use of the existing technology and has continued to be refined as use of the World Wide Web has continued to grow.

MPLS plays a major role in keeping the networks of big businesses running smoothly today. The labeling process involves setting the criteria for information retrieval, sometimes determined by an IP address. The data is then directed through routers that have been pre-determined by the label switching. As a final step, the data is delivered to the end location. This entire process is completed in less than a few seconds, when the system is working at maximum efficiency.

The implementation of MPLS protocols also help make it possible to run different types of traffic on the same network, such as the ability to carry data, audio, and video at the same time. MPLS technology also makes it possible to restore data faster after a network failure takes place, even if there is not a backup server involved in the overall network design. Overall, MPLS is an essential traffic management tool that becomes increasingly important as the Internet is used for more communication applications.

http://www.wisegeek.com/what-is-mpls.htm

WEBOPEDIA.com Definition:

Short for Multiprotocol Label Switching, an IETF initiative that integrates Layer 2 information about network links (bandwidth, latency, utilization) into Layer 3 (IP) within a particular autonomous system–or ISP–in order to simplify and improve IP-packet exchange.

MPLS gives network operators a great deal of flexibility to divert and route traffic around link failures, congestion, and bottlenecks.

From a QoS standpoint, ISPs will better be able to manage different kinds of data streams based on priority and service plan. For instance, those who subscribe to a premium service plan, or those who receive a lot of streaming media or high-bandwidth content can see minimal latency and packet loss.

When packets enter a MPLS-based network, Label Edge Routers (LERs) give them a label (identifier). These labels not only contain information based on the routing table entry (i.e., destination, bandwidth, delay, and other metrics), but also refer to the IP header field (source IP address), Layer 4 socket number information, and differentiated service. Once this classification is complete and mapped, different packets are assigned to corresponding Labeled Switch Paths (LSPs), where Label Switch Routers (LSRs) place outgoing labels on the packets.

With these LSPs, network operators can divert and route traffic based on data-stream type and Internet-access customer.

http://www.webopedia.com/TERM/M/MPLS.html

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