Broadcast Search

A broadcast search is issued by a network node because a directed search using database information has failed or there is no database information for the requested resource. A broadcast search does not use database information about the location of a requested LU to propagate the search. Instead, a broadcast search is sent to every adjacent network node at the same time. Each of the adjacent network nodes then forwards the broadcast search to all other adjacent network nodes, and so forth. After propagating a broadcast search to all adjacent network nodes, each network node also searches all its client end nodes to determine if the target LU resides within the domain of the network node.
This process allows the entire network to be searched. When the search reaches the network node serving the destination resource, that node sends back a positive reply to the first search request it receives.
In Figure 1, LUA on ENA wants to start a session with LUB on ENB.
Figure 1. Broadcast search - stage 1










ENA sends a directed search to its network node server (NN1). Because the directory database of NN1 has no information about LUB, NN1 sends a network broadcast search to all end nodes served by NN1. If LUB is not located in the NN1 local domain, the broadcast search is propagated at the same time to all adjacent network nodes.
After propagating the broadcast search, network nodes search local node and served end nodes.


Figure 2. Broadcast search - propagating to served end nodes












Since LUB is located in ENB, ENB sends a positive reply to the broadcast search request. The reply is returned along the same path as the request. The directory database in NN4 and NN1 is updated with the information about the locations of both LUB and LUA.