How many bits in length is the 'TTL' field in the IPv4 header?

The Time to Live (TTL) field in the IPv4 header is 8 bits in length. This field is used to specify the maximum number of hops that a packet can take before it is discarded. Each time the packet passes through a router (a hop), the TTL value is decremented by one. When the value reaches zero, the packet is considered expired and is discarded to prevent it from circulating indefinitely in the network due to routing errors or loops.

The 8-bit length allows TTL to represent values from 0 to 255, providing an adequate range to control the packet's lifetime in typical network scenarios. The other options do not accurately reflect the actual size of the TTL field in the IPv4 header.