How many bits make up an MPLS label field?

The MPLS (Multiprotocol Label Switching) label field consists of 20 bits. This label is used in MPLS packets to make forwarding decisions at routers without the need to inspect the entire packet's header. The label field is crucial for the operation of MPLS, allowing for efficient data forwarding through an MPLS network by enabling label-switching rather than traditional routing based on IP addresses.

Each MPLS label is accompanied by additional fields, such as the Exp field for quality of service (QoS) handling, the S field which indicates the bottom of the label stack, and the TTL (Time to Live) field, but these additional bits do not contribute to the size of the label field itself. Thus, the 20 bits of the MPLS label are specifically dedicated solely for the label, making this a key characteristic of MPLS technology.