What field in the IPv4 header is used to prevent infinite routing loops?

The field in the IPv4 header that is specifically used to prevent infinite routing loops is the Time to Live (TTL) field. This field is a crucial mechanism that limits the lifespan of a data packet as it traverses through the networks. Each time a packet is forwarded by a router, the TTL value is decremented by one. If the TTL value reaches zero, the packet is discarded, and an Internet Control Message Protocol (ICMP) message is typically sent back to the sender indicating that the packet was dropped due to expiration.

This mechanism is important because it helps to prevent packets from circulating indefinitely in the network due to misconfigurations or routing loops. In the absence of TTL, packets could loop endlessly between routers, causing network congestion and inefficient use of resources. By using the TTL field effectively, the network can avoid these issues, ensuring that packets do not remain in the network for too long and ultimately get removed if they cannot reach their destination in a reasonable amount of time.

The other options do not serve this purpose. The Fragment Offset is used to indicate the position of a fragment in the original datagram, while the Checksum field verifies the integrity of the header and data. The Protocol field identifies the upper-layer protocol used in the data