What is MPLS?
In the TCP/IP model, the Internet Layer (Layer 3) is responsible for managing IP addressing and routing packets between different networks. MPLS sits between the traditional Layer 2 (Network Access Layer) and Layer 3 (Internet Layer) in the TCP/IP model, which is sometimes referred to as Layer 2.5 or Shim Header.
Figure 1.1 – MPLS Header
The MPLS header comprises four fields, totaling 32 bits in size:
- Label: The Label field is the most critical part of the MPLS header, comprising a fixed size of 20 bits that carries the forwarding information for the packet. Each router in an MPLS-enabled network maintains a forwarding table that maps incoming labels to the next-hop router and the corresponding output interface. The label is used to quickly determine the packet’s path through the network, making the forwarding process more efficient.
- Experimental (EXP) or Traffic Class (TC) bits: The Experimental bits field is 3...
