ICND 1

synchronizationacknowledgment. 

system logging. 

standard terminal emulation protocol in the TCP/IP protocol stack. Telnet is used for remote terminal connection, enabling users to log into remote systems and use resources as if they were connected to a local system. Telnet is defined in RFC 854. 

Telecommunications Industry Alliance. Organization that develops standards relating to telecommunications technologies. Together, the TIA and the EIA have formalized standards, such as EIA/TIA232, for the electrical characteristics of data transmission. 

Transport Layer Security. A future IETF protocol to replace SSL. 

type, length, value. 

Tokenpassing LAN that was developed and supported by IBM. Token Ring runs at 4 or 16 Mbps over a ring topology. Similar to IEEE 802.5. 

type of service 

Time to Live. A mechanism that limits the lifespan or lifetime of data in a computer or network. 

unique device identifier. 

uninterruptible power supply. 

Coordinated Universal Time. Time zone at zero degrees longitude. Formerly called Greenwich Mean Time (GMT) and Zulu time. 

unshielded twistedpair. Fourpair wire medium used in a variety of networks. UTP does not require the fixed spacing between connections that is necessary with coaxialtype connections. Five types of UTP cabling are commonly used: Category 1, Category 2, Category 3, Category 4, and Category 5. 

VLAN ID. The identification of the VLAN, which is used by the standard IEEE 802.1Q. Being 12 bits, it allows for the identification of 4096 VLANs. 

virtual LAN. Group of devices on one or more LANs that are configured (using management software) so that they can communicate as if they were attached to the same wire, when in fact they are located on a number of different LAN segments. Because VLANs are based on logical instead of physical connections, they are extremely flexible. 

variablelength subnet mask. Capability to specify a different subnet mask for the same network number on different subnets. VLSM can help optimize available address space. 

wireless access point. 

Worldwide Interoperability for Microwave Access (WiMAX) is a family of wireless communications standards designed to provide up to 1 Gbit/s data rates. 

Windows Internet Name Service. 

wireless LAN. A LAN is a highspeed, lowerror data network covering a relatively small geographic area (up to a few thousand meters). LANs connect workstations, peripherals, terminals, and other devices in a single building or other geographically limited area. LAN standards specify cabling and signaling at the physical and data link layers of the OSI model. Ethernet, FDDI, and Token Ring are widely used LAN technologies. 

10Mbps baseband Ethernet specification using two pairs of twistedpair cabling (Categories 3, 4, or 5): one pair for transmitting data and the other for receiving data. 10BASET, which is part of the IEEE 802.3 specification, has a distance limit of approximately 328 feet (100 meters) per segment. 

thirdgeneration mobile network. Refers generically to a category of nextgeneration mobile networks, such as UMTS and IMT2000. *official* 

fourth generation of mobile phone mobile communications standards. 

fifthgeneration mobile network. 

acknowledgment. Notification sent from one network device to another to acknowledge that some event occurred (for example, the receipt of a message). 

access control list. A list kept by routers to control access to or from the router for a number of services (for example, to prevent packets with a certain IP address from leaving a particular interface on the router). 

Rating of the trustworthiness of a routing information source. Administrative distance often is expressed as a numerical value between 0 and 255. The higher the value, the lower the trustworthiness rating. 

African Network Information Center. AfriNIC is the Regional Internet Registry (RIR) for Africa. They are responsible for the distribution and management of Internet number resources (such as IP addresses and ASN Numbers) for the African region. 

Authentication Header. A security protocol that provides data authentication and optional antireplay services. AH is embedded in the data to be protected (a full IP datagram). 

In anycast routing, the IP packet is sent to the topologically nearest host. 

access point. A node on a wireless network that allows other wireless devices to connect to a wired network. 

application programming interface. The means by which an application program talks to communications software. Standardized APIs allow application programs to be developed independently of the underlying method of communication. A set of standard software interrupts, calls, and data formats that computer application programs use to initiate contact with other devices (for example, network services, mainframe communications programs, or other programtoprogram communications). Typically, APIs make it easier for software developers to create the links that an application needs to communicate with the operating system or with the network. 

Asia Pacific Network Information Center. Nonprofit Internet registry organization for the Asia Pacific region. The other Internet registries are currently IANA, RIPE NCC, and InterNIC. 

American Registry for Internet Numbers. A nonprofit organization that administers and registers IP numbers for the geographical areas that are currently managed by Network Solutions (InterNIC). Those areas include, but are not limited to, North America, South America, South Africa, and the Caribbean. 

Address Resolution Protocol. Internet protocol that is used to map an IP address to a MAC address. Defined in RFC 826. 

autonomous system. A collection of networks under a common administration sharing a common routing strategy. Autonomous systems are subdivided by areas. An autonomous system must be assigned a unique 16bit number by the IANA. 

American Standard Code for Information Interchange. An 8bit code for character representation (7 bits plus parity). 

Asynchronous Transfer Mode. The international standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixedlength (53byte) cells. Fixedlength cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take advantage of highspeed transmission media, such as E3, SONET, and T3. 

auxiliary.