Which type of message is defined as ICMPv6 Type 135?

The correct message type defined as ICMPv6 Type 135 is Neighbor Solicitation. ICMPv6 (Internet Control Message Protocol for IPv6) is an essential part of the IPv6 protocol suite, providing diagnostic and control functions.

Neighbor Solicitation messages are used by a device to determine the link-layer address (MAC address) of another node on the same local network segment when only the IPv6 address is known. This process is crucial for IPv6 operations, such as during the address resolution phase, which assists in ensuring successful communication between devices on an IPv6 network. Essentially, when a host wants to communicate with another host but does not know its MAC address, it sends out a Neighbor Solicitation message asking who has a specific IPv6 address.

This process also plays a role in maintaining the local network information, allowing devices to keep track of each other and maintain an updated view of the network topology, which is integral for effective communication and connectivity in IPv6 environments. Understanding the function of Neighbor Solicitation clarifies its importance in network operations and protocols.