Guide To Networks Ch2 Terms

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802.2

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The IEEE standard for error and flow control in data frames.

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802.3

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The IEEE standard for Ethernet networking devices and data handling (using the CSMA/CD access method).

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802.5

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The IEEE standard for token ring networking devices and data handling.

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802.11

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The IEEE standard for wireless networking.

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802.16

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The IEEE standard for broadband wireless metropolitan area networking (also known as WiMAX).

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ACK

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(acknowledgment) A response generated at the Transport layer of the OSI model that confirms to a sender that its frame was received. The ACK packet is the third of three in the three-step process of establishing a connection.

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ANSI

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(American National Standards Institute) An organization composed of more than 1000 representatives from industry and government who together determine standards for the electronics industry in addition to other fields, such as chemical and nuclear engineering, health and safety, and construction.

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API

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(application program interface) A set of routines that make up part of a software application.

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Application layer

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The seventh layer of the OSI model. Application layer protocols enable software programs to negotiate formatting, procedural, security, synchronization, and other requirements with the network.

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block ID

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The first set of six characters that make up the MAC address and that are unique to a particular manufacturer.

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checksum

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A method of error checking that determines if the contents of an arriving data unit match the contents of the data unit sent by the source.

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connection oriented

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A type of Transport layer protocol that requires the establishment of a connection between communicating nodes before it will transmit data.

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connectionless

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A type of Transport layer protocol that services a request without requiring a verified session and without guaranteeing delivery of data.

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CRC

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(cyclic redundancy check) An algorithm (or mathematical routine) used to verify the accuracy of data contained in a data frame.

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Data Link layer

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The second layer in the OSI model. The Data Link layer bridges the networking media with the Network layer. Its primary function is to divide the data it receives from the Network layer into frames that can then be transmitted by the Physical layer.

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device ID

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The second set of six characters that make up a network device’s MAC address. The device ID, which is added at the factory, is based on the device’s model and manufacture date.

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EIA

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(Electronic Industries Alliance) A trade organization composed of representatives from electronics manufacturing firms across the United States that sets standards for electronic equipment and lobbies for legislation favorable to the growth of the computer and electronics industries.

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encapsulate

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The process of wrapping one layer’s PDU with protocol information so that it can be interpreted by a lower layer. For example, Data Link layer protocols encapsulate Network layer packets in frames.

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Ethernet

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A networking technology originally developed at Xerox in the 1970s and improved by Digital Equipment Corporation, Intel, and Xerox. Ethernet, which is the most common form of network transmission technology, follows the IEEE 802.3 standard.

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FCS

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(frame check sequence) The field in a frame responsible for ensuring that data carried by the frame arrives intact. It uses an algorithm, such as CRC, to accomplish this verification.

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flow control

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A method of gauging the appropriate rate of data transmission based on how fast the recipient can accept data.

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fragmentation

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A Network layer service that subdivides segments it receives from the Transport layer into smaller packets.

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frame

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A package for data that includes not only the raw data, or “payload,” but also the sender’s and recipient’s addressing and control information. Frames are generated at the Data Link layer of the OSI model and are issued to the network at the Physical layer.

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HTTP

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(Hypertext Transfer Protocol) An Application layer protocol that formulates and interprets requests between Web clients and servers.

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IAB

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(Internet Architecture Board) A technical advisory group of researchers and technical professionals responsible for Internet growth and management strategy, resolution of technical disputes, and standards oversight.

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IANA

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(Internet Assigned Numbers Authority) A nonprofit, United States government funded group that was established at the University of Southern California and charged with managing IP address allocation and the domain name system. The oversight for many of IANA’s functions was given to ICANN in 1998; however, IANA continues to perform Internet addressing and domain name system administration.

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ICANN

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(Internet Corporation for Assigned Names and Numbers) The nonprofit corporation currently designated by the United States government to maintain and assign IP addresses.

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IEEE

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(Institute of Electrical and Electronics Engineers) An international society composed of engineering professionals. Its goals are to promote development and education in the electrical engineering and computer science fields.

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IETF

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(Internet Engineering Task Force) An organization that sets standards for how systems communicate over the Internet (for example, how protocols operate and interact).

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IP

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(Internet Protocol) A core protocol in the TCP/IP suite that operates in the Network layer of the OSI model and provides information about how and where data should be delivered. IP is the sub-protocol that enables TCP/IP to internetwork.

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IP address

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(Internet Protocol address) The Network layer address assigned to nodes to uniquely identify them on a TCP/IP network. IP addresses consist of 32 bits divided into four octets, or bytes.

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ISO

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(International Organization for Standardization) A collection of standards organizations representing 157 countries with headquarters located in Geneva, Switzerland. Its goal is to establish international technological standards to facilitate the global exchange of information and barrier-free trade.

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ISOC

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(Internet Society) A professional organization with members from 90 chapters around the world that helps to establish technical standards for the Internet.

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ISP

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(Internet service provider) A business that provides organizations and individuals with Internet access and often, other services, such as e-mail and Web hosting.

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ITU

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(International Telecommunication Union) A United Nations agency that regulates international telecommunications and provides developing countries with technical expertise and equipment to advance their technological bases.

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LLC

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(Logical Link Control) sublayer The upper sublayer in the Data Link layer. The LLC provides a common interface and supplies reliability and flow control services.

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MAC address

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A 12-character string that uniquely identifies a network node. The manufacturer hard codes the MAC address into the NIC. This address is composed of the block ID and device ID.

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MAC

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(Media Access Control) sublayer The lower sublayer of the Data Link layer. The MAC appends the physical address of the destination computer onto the frame.

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MTU

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(maximum transmission unit) The largest data unit a network (for example, Ethernet or token ring) will accept for transmission.

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network address

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A unique identifying number for a network node that follows a hierarchical addressing scheme and can be assigned through operating system software. Network addresses are added to data packets and interpreted by protocols at the Network layer of the OSI model.

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Network layer

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The third layer in the OSI model. Protocols in the Network layer translate network addresses into their physical counterparts and decide how to route data from the sender to the receiver.

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OSI

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(Open Systems Interconnection) model A model for understanding and developing computer-to-computer communication developed in the 1980s by ISO. It divides networking functions among seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

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PDU

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(protocol data unit) A unit of data at any layer of the OSI model.

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Physical layer

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The lowest, or first, layer of the OSI model. Protocols in the Physical layer generate and detect signals so as to transmit and receive data over a network medium. These protocols also set the data transmission rate and monitor data error rates, but do not provide error correction.

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Presentation layer

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The sixth layer of the OSI model. Protocols in the Presentation layer translate between the application and the network. Here, data are formatted in a schema that the network can understand, with the format varying according to the type of network used. The Presentation layer also manages data encryption and decryption, such as the scrambling of system passwords.

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reassembly

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The process of reconstructing data units that have been segmented.

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RIR

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(Regional Internet Registry) A not-for-profit agency that manages the distribution of IP addresses to private and public entities. ARIN is the RIR for North, Central, and South America and sub-Saharan Africa. APNIC is the RIR for Asia and the Pacific region. RIPE is the RIR for Europe and North Africa.

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route

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To intelligently direct data between networks based on addressing, patterns of usage, and availability of network segments.

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router

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A device that connects network segments and directs data based on information contained in the data packet.

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segment

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A unit of data that results from subdividing a larger protocol data unit.

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segmentation

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The process of decreasing the size of data units when moving data from a network that can handle larger data units to a network that can handle only smaller data units.

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sequencing

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The process of assigning a placeholder to each piece of a data block to allow the receiving node’s Transport layer to reassemble the data in the correct order.

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session

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A connection for data exchange between two parties. The term session may be used in the context of Web, remote access, or terminal and mainframe communications, for example.

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Session layer

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The fifth layer in the OSI model. The Session layer establishes and maintains communication between two nodes on the network. It can be considered the “traffic cop” for network communications.

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standard

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A documented agreement containing technical specifications or other precise criteria that are used as guidelines to ensure that materials, products, processes, and services suit their intended purpose.

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SYN

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(synchronization) The packet one node sends to request a connection with another node on the network. The SYN packet is the first of three in the three-step process of establishing a connection.

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SYN-ACK

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(synchronization-acknowledgment) The packet a node sends to acknowledge to another node that it has received a SYN request for connection. The SYN-ACK packet is the second of three in the three-step process of establishing a connection.

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terminal

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A device with little (if any) of its own processing or disk capacity that depends on a host to supply it with applications and data-processing services.

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TIA

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(Telecommunications Industry Association) A subgroup of the EIA that focuses on standards for information technology, wireless, satellite, fiber optics, and telephone equipment. Probably the best known standards to come from the TIA/EIA alliance are its guidelines for how network cable should be installed in commercial buildings, known as the “TIA/EIA 568-B Series.”

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token

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A special control frame that indicates to the rest of the network that a particular node has the right to transmit data.

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token ring

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A networking technology developed by IBM in the 1980s. It relies upon direct links between nodes and a ring topology, using tokens to allow nodes to transmit data.

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Transport layer

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The fourth layer of the OSI model. In the Transport layer protocols ensure that data are transferred from point A to point B reliably and without errors. Transport layer services include flow control, acknowledgment, error correction, segmentation, reassembly, and sequencing.