MPLS — Multiprotocol Label Switching (2.5 layer protocol)
I have posted about Circuit Switching & Packet Switching — I’ll link them at them bottom. Do give it a read, if you’re unfamiliar.
Let’s look at an example to understand how IP packets travel over the internet —
Suppose, an IP packet is sent from Mumbai to Kansas. Let’s assume the destination IP to be 220.127.116.11
As it travels over the internet, many routers are involved in forwarding this packet along the path towards the destination.
The first router will open the IP packet and reads its IP address, forward it to the next router. The next router also does the same thing. And the next one…and the next one till IP packet has reached its destination. This is how packet switching works. It is flexible and data packet’s path is not fixed. But processing IP information at every step is troublesome slowing down the transmission speed.
Circuit Switching is a fixed-path switching method. Generally used for traditional telephone communications. It is reliable but more expensive.
MPLS on the other hand, allows IP packets to be forwarded at layer 2 — switching level without being passed up to layer 3 — the routing level. Let’s look at the working of MPLS with the same IP packet being sent from Mumbai to Kansas. The packets in MPLS, have an additional info of MPLS Labels.
The MPLS label is inserted between layer 2 Header and layer 3 Header. The key difference now, is that the path for the IP packet is predetermined…before the packet is sent. The routers along the way now don’t need to determine the IP address of the next router. Instead, they only interpret the MPLS labels and only look at the destination IP address until at the final destination.
The result ?
MPLS offers a faster transmission of IP packets than traditional switching methods. So…MPLS can create end-to-end paths that act like circuit-switched connections, but deliver layer 3 IP packets. Routing is layer 3 function while switching is layer 2 function. MPLS makes those routers on the internet act like switches on a local network.