tion in a network that contains computers and additional devices that have dissimilar operating systems or protocols. intranet A network based on TCP/IP protocols (i.e., an internet) that belongs to an organization and is accessible only by the organization's members, employees, or others with authorization. intranet VPN A site-to-site connection whose key objective is to replace or reduce the use of leased-line networks, traditional routers, and Frame Relay services. IntServ (Integrated Services) The IETF's scheme to introduce QoS support over IP net- works. IntServ provides extensions to the best-effort service model to allow control over end-to- end packet delays. IntServ is a per-flow resource reservation model that requires RSVP. Its key building blocks include resource reservation and admission control. Inverse ARP An extension to ARP that permits a station to request a protocol address (e.g., an IP address) given a hardware address (e.g., a Frame Relay DLCI). inverse multiplexer A device that spreads a high-bandwidth information stream over multi- ple lower-speed transmission channels (e.g., a 1.5Mbps signal transmitted over 24 64Kbps chan- nels of a T-1). I/O (input/output) (1) A device or channel that may be involved in an input process, and, at a different time, in an output process. (2) A device whose parts can be performing an input process and an output process at the same time. (3) Pertains to either input or output, or both. IP (Internet Protocol) The protocol that specifies the exact format of all data as it trav- els through a TCP/IP network. In addition, IP performs the routing functions and selects the transmission path on which data will be sent. As part of these two functions, IP also provides a mechanism for dealing with unreliable data, specifying the manner in which net- work nodes will process data, how and when to generate error messages, and when to dis- card unreliable data. IP address The 32-bit address assigned to a host that wants to participate in a TCP/IP inter- net. IP addresses 