Final answer:
The 'time to live' (TTL) field in an IP datagram represents the maximum number of routers that the datagram can visit before being dropped. The TTL field is significant in preventing datagrams from circulating endlessly in a network.
Step-by-step explanation:
The 'time to live' (TTL) field in an IP datagram represents the maximum number of routers that the datagram can visit before being dropped. The initial value of the TTL field is given as DD in hexadecimal, and the datagram has already visited AA routers.
To determine the remaining routers the datagram can visit, we need to perform hexadecimal subtraction. So, the remaining routers can be calculated as DD - AA = 23 (decimal), which is equivalent to 17 in hexadecimal.
The TTL field is significant because it helps prevent datagrams from circulating endlessly in a network. Each time a router receives a datagram, it decrements the TTL value by 1. If the TTL reaches 0, the datagram is discarded. This ensures that datagrams do not loop indefinitely and helps in network efficiency.
The relationship between the initial TTL value and the visited routers can be analyzed by subtracting the number of visited routers from the initial TTL value.
The maximum number of routers the datagram can visit is equal to the initial TTL value, which in this case is DD (hexadecimal) or 221 (decimal).