The portion of a network that is reachable by a network broadcast, which is a request for an address resolution or an announcement of availability ("what is the address of that node?," "I am here," etc.). Unlike a collision domain, which concentrates at layer 2 (data link layer) and is typically within a LAN segment, a broadcast can be initiated at various protocol layers, thus the domain can be within a LAN segment or routed across LAN segments. See broadcast, broadcast traffic and collision domain.