ICND 1

Network Time Protocol. A protocol that is built on top of TCP that ensures accurate local timekeeping with reference to radio and atomic clocks that are located on the Internet. This protocol is capable of synchronizing distributed clocks within milliseconds over long time periods. 

NAT Virtual Interface. 

nonvolatile RAM. RAM that retains its contents when a unit is powered off. 

Open Systems Interconnection. International standardization program created by ISO and ITUT to develop standards for data networking that facilitate multivendor equipment interoperability. 

Open Systems Interconnection reference model. Network architectural model developed by ISO and ITUT. The model consists of seven layers, each of which specifies particular network functions, such as addressing, flow control, error control, encapsulation, and reliable message transfer. The lowest layer (the physical layer) is closest to the media technology. The lower two layers are implemented in hardware and software whereas the upper five layers are implemented only in software. The highest layer (the application layer) is closest to the user. The OSI reference model is used universally as a method for teaching and understanding network functionality. Similar in some respects to SNA. 

Open Shortest Path First. Linkstate, hierarchical IGP routing algorithm proposed as a successor to RIP in the Internet community. OSPF features include leastcost routing, multipath routing, and load balancing. OSPF was derived from an early version of the ISIS protocol. 

Open Shortest Path First version 2. 

Open Shortest Path First version 3. 

Organizational Unique Identifier. Three octets that are assigned by the IEEE in a block of 48bit LAN addresses. 

Product Authorization Key. 

port address translation. Translation method that allows the user to conserve addresses in the global address pool by allowing source ports in TCP connections or UDP conversations to be translated. Different local addresses then map to the same global address, with port translation providing the necessary uniqueness. When translation is required, the new port number is picked out of the same range as the original following the convention of Berkeley Standard Distribution (SD). 

Personal Computer Memory Card International Association. Standard used for creditcardsized computer peripherals. Type I devices are very thin memory cards, Type 2 devices include most modems and interfaces, and Type 3 devices are used for disk drives and thicker components. 

protocol data unit. OSI term for packet. 

product identifier. 

Power over Ethernet. 

poweron self test. Set of hardware diagnostics that runs on a hardware device when this device is powered on. 

PointtoPoint Protocol. Successor to SLIP that provides routertorouter and hosttonetwork connections over synchronous and asynchronous circuits. Whereas SLIP was designed to work with IP, PPP was designed to work with several network layer protocols, such as IP, IPX, and ARA. PPP also has builtin security mechanisms, such as CHAP and PAP. PPP relies on two protocols: LCP and NCP. 

An SSH and Telnet client for Windows and Unix platforms. 

quality of service. Measure of performance for a transmission system that reflects its transmission quality and service availability. 

Reverse Address Resolution Protocol. Protocol in the TCP/IP stack that provides a method for finding IP addresses based on MAC addresses. 

remote copy protocol. Protocol that allows users to copy files to and from a file system residing on a remote host or server on the network. The rcp protocol uses TCP to ensure the reliable delivery of data. 

radio frequency interference. Radio frequencies that create noise that interferes with information being transmitted across unshielded copper cable. 

Routing Information Protocol. A distancevector routing protocol that uses hop count as a routing metric. 

Réseaux IP Européens Network Coordination Centre. The RIPE NCC is one of five Regional Internet Registries (RIRs), providing Internet resource allocations, registration services, and coordination activities that support the operation of the Internet globally. 

Routing Information Protocol next generation. 

Routing Information Protocol version 1. 

Routing Information Protocol version 2. 

regional Internet registry. 

"Registered Jack45" is an eightwire connector that is commonly used to connect computers onto a LAN. 

Protocol that accomplishes routing through the implementation of a specific routing algorithm. Examples of routing protocols include IGRP, OSPF, and RIP. 

Table stored in a router or some other internetworking device that keeps track of routes to particular network destinations and, in some cases, metrics associated with those routes. 

redundant power supply. 

Popular physical layer interface. Now known as EIA/TIA232. 

Acronym stands for Rivest, Shamir, and Adleman, the inventors of the technique. Publickey cryptographic system that can be used for encryption and authentication.