Lightweight Directory Access Protocol (LDAP)

The Lightweight Directory Access Protocol (LDAP) is a protocol that provides a mechanism to access and query directory services systems. These directory services systems are most likely to be Novell Directory Services (NDS) and Microsoft's Active Directory.

Although LDAP supports command-line queries that are executed directly against the directory database, most LDAP interactions will be via utilities such as an authentication program (network logon) or locating a resource in the directory through a search utility. LDAP operates at the application layer of the OSI model.

Internet Group Management Protocol (IGMP)

The Internet Group Management Protocol (IGMP) protocol is associated with the process of multicasting. Multicasting is a mechanism by which groups of network devices can send and receive data between the members of the group at one time, rather than separately sending messages to each device in the group.

The IGMP protocol is used to register devices into a multicast group, as well as to discover what other devices on the network are members of the same multicast group. Common applications for multicasting include groups of routers on an internetwork and videoconferencing clients. IGMP operates at the network layer of the OSI model.

Line Printer Remote (LPR)

The Line Printer Remote (LPR) protocol provides a means to connect to print servers on a network. It is a generic printing protocol supported by all commonly used operating systems including UNIX, Windows, and Linux.

To make use of LPR, client software is installed on a system. When a file is sent to print, it is channeled over the network by LPR to a print server or printer. That server or printer runs a print server program, normally the Line Printer Daemon (LPD), which accepts the LPR information and adds that job to the print queue. LPR operates at the application layer of the OSI model.