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How does Multiprotocol Label Switching (MPLS) Routing work ?

Last Updated : 28 Jan, 2020
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Multiprotocol Label Switching (MPLS) is a traffic routing mechanism it has significant advantages over the traditional IP based routing mechanism, MPLS is used in telecommunication networking where it shapes the data packet transmission among the nodes.

In traditional IP based routing, IP datagram packet is analyzed by the router and according to the source and destination address contains by the packet it has been processing and forwarded by the routers (by using routing table for packet forwarding), this datagram follow the path set up by the routing protocol such as (OSPF, BGP, EGP) and accomplish the defined route to reaching till the destination node.

An IP address is the identity of the network and a subnet mask, when a packet is forwarded by the routers, the routing table is used to determine the forwarding mechanism and the packet is sent over the interface registered with a route containing shortest optimize path till the destination. If there is no route found for the packet in the routing table, the default route is used to transmit the packet to the destination.

MPLS was introduced in late 1990 it is a more efficient routing mechanism alternative to the traditional IP based routing method.

In MPLS each router requires to determine the next router or the next node/hope of the packet(where the datagram need to be transmitted) by inspecting the packet destination address before conferring its own routing table, this process is slow and degraded in terms of time consumption and performance for live scenario such as audio and video transmission in real-time applications.

With IP routing in a traditional packet-switched network, data packets determine its own routing path through the network hopes. It means datagrams have the dynamic path flow to the destination which is neither pre-decided nor predictable. In circuit-switched telecom networks, the dedicated circuit path is established between the source and the destination each of the packets follows this pre-decided routing path to reach to the destination hope, by passing through the number of switching centers. the sender and receiver begin the communication by requesting and acknowledging the established circuit. this circuit can carry the network traffic such as the data and voice and video streaming but this is predictable and predecided routing paths, but extremely costly and difficult to scale up to the large network because of the need to develop the circuit infrastructure.

To overcome these difficulties, the MPLS routing mechanism has been introduced, which enables more control over the dynamic network routing path, by establishing the dynamic paths which seem like a hope to hope connection inside the network infrastructure. but the dynamic routing by using the MPLS is logical rather than a physical path.

How do MPLS works ?
MPLS routing mechanism works with almost all types of networking protocols and transmission channels such as IP (Internet Protocol), ATM (Asynchronous Transport Mode), Ethernet.

Datagram packets are redirected through the routers by assigning the label to each packet by passing through each router called Label Switch Paths (LSP’s) in the telecommunications network. The label is associated with a predecided route throughout the network hopes, when hope receives the datagram it dynamically assigns the label to the datagram packet to pass through it to the other upcoming hops. it means the label of control is higher as compare to the packet-switched networks.

Labels used in the switching act as transmission paths in an MPLS network, which are established by the signaling protocols, these patch guides voice and data packets to their final ultimate destination in the network.

Let’s understand it working with an example when a pos office assign work to postman to search, sort and look through each of the parcels to get to know to the address of its receiver it will make the process slows down due to manual working, instead if it will use the automated conveyor sorting system to search, sort the packet by scanning the barcode stick on the top of the packet, due to automated system processing it will improve speed of the parcel processing and sorting drastically and longer-lasting.

LSP’s improve the speed and optimize the process of the data packet transmission by passing it through the routers over the network, by allowing each router to quickly determine where the packet is going.

As data packets pass through the MPLS network, its labels are swapped by the routers. As the packet been through the boundary of the MPLS backbone it is examined, classified and assigned a label. after it, these packets forwarded to the next step in the pre-set Label Switched Path (LSP). As the packet passes through the path, each router on the path uses the label to determine where the datagram should be redirected routed.

MPLS Pros and Cons:

  1. PLS is dynamic, scalable, versatile with better performance, better bandwidth utilization, reduce network traffic congestion as compared to traditional IP routing.
  2. MPLS is a virtual private network and it does not provide encryption by itself, it is separated from the public Internet. this is the reason, MPLS is considerable secure transmission mode for data packets. And it is not easily vulnerable to DOS attacks, which can affect the IP based routing.
  3. On the other side, MPLS is a mechanism that needs to purchase a carrier frequency to use it in the network that is the reason it is more costly than the transmission which can be accomplished through the public network.
  4. As long as the organization expands its infrastructure, it is difficult to find the MPLS service provider for global coverage service. which can be costly and time-consuming.
  5. MPLS was designed to use when multiple branch offices receive and sent traffic back to a main headquarters or data center, it is not suited where branch office directly want to access the data available on the cloud.

Enterprise network architecture should be durable enough to determine the service and risk between the expensive and faster performance of MPLS and the cheaper and less versatile performance of the public Internet/Intranet.

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