Which value, contained in an IPv4 header field, is decremented by each router that receives a packet?

Which value, contained in an IPv4 header field, is decremented by each router that receives a packet?

• A. Header Length
• B. Time-to-Live
• C. Protocol Type
• D. Fragment Offset

Answer: (B)

The value that is decremented by each router that receives a packet is the Time-to-Live (TTL). The purpose of the TTL field is to prevent packets from circulating endlessly in the network due to routing loops. Each time a router forwards a packet, it decreases the TTL value by one. If the TTL reaches zero, the packet is discarded, and an Internet Control Message Protocol (ICMP) message may be sent back to the sender, indicating that the packet could not be delivered. The other fields listed in the question serve different purposes. The Header Length indicates the length of the header in 32-bit words and does not change. The Protocol Type identifies the protocol used in the payload of the packet but is not modified as the packet traverses the network. The Fragment Offset indicates the position of fragmented data in the packet and remains static during the routing process.

The value that is decremented by each router that receives a packet is the Time-to-Live (TTL). The purpose of the TTL field is to prevent packets from circulating endlessly in the network due to routing loops. Each time a router forwards a packet, it decreases the TTL value by one. If the TTL reaches zero, the packet is discarded, and an Internet Control Message Protocol (ICMP) message may be sent back to the sender, indicating that the packet could not be delivered.

The other fields listed in the question serve different purposes. The Header Length indicates the length of the header in 32-bit words and does not change. The Protocol Type identifies the protocol used in the payload of the packet but is not modified as the packet traverses the network. The Fragment Offset indicates the position of fragmented data in the packet and remains static during the routing process.