| Application Layer | Layer 7 of the OSI reference model. This layer provides services to application processes that are outside of the OSI model. |
| ARP (Address Resolution Protocol) | Internet protocol used to map an IP address to a MAC address. |
| Cisco IOS (Internetwork Operation System) software | Cisco system software that provides common functionality, scalability, and security for all products under the CiscoFusion architecture. |
| Data Link Layer | Layer 2 of the OSI reference model. This layer provides reliable transit of data across a physical link. |
| Datagram | Logical grouping of information sent as a network layer unit over a transmission medium without prior establishment of a virtual circuit. |
| Default route | Routing table entry that is used to direct frames for which a next hop is not explicitly listed in the routing table. |
| Dynamic routing | Routing that adjusts automatically to network topology or traffic changes. |
| EIGRP (Enhanced Interior Gateway Routing Protocol) | Advanced version of IGRP developed by Cisco. Provides superior convergence properties and operating efficiency, and combines the advantages of link state protocols with those of distance vector protocols. |
| Flow Control | Technique for ensuring that a transmitting entity, such as a modem, does not overwhelm a receiving entity with data. |
| ICMP (Internet Control Message Protocol) | Network layer Internet protocol that reports errors and provides other information relevant to IP packet processing. |
| IGRP (Interior Gateway Routing Protocol) | IGP developed by Cisco to address the problems associated with routing in large, heterogeneous networks. |
| IP Address | 32-bit address assigned to hosts using TCP/IP. An IP address belongs to one of five classes (A, B, C, D, or E) and is written as 4 octets separated with periods (dotted decimal format). |
| MAC (Media Access Control) | Lower of the two sublayers of the data link layer defined by the IEEE. The MAC sublayer handles access to shared media, such as whether token passing or contention will be used. |
| Network | Collection of computers, printers, routers, switches, and other devices that are able to communicate with each other over some transmission medium. |
| Network Layer | Layer 3 of the OSI reference model. This layer provides connectivity and path selection between two end systems. |
| NIC (Network Interface Card) | Board that provides network communication capabilities to and from a computer system. |
| Packet | Logical grouping of information that includes a header containing control information and (usually) user data. |