SYSTEM ADMINISTRATION Chapter 3 IEEE Specifications and their Characteristics

Understanding Project 802 Standards Project 802 addresses aspects of networking technology. Whenever a new technology, such as wireless communications, is introduced, a committee is formed to investigate and make recommendations on that technology. Their results are often published as standards. These standards are written to address how networking should occur between devices that are using that particular technology.

A Brief Introduction to the OSI Model The OSI Model provides a framework for the rules that network devices will use to talk with each other. There are seven layers to the OSI Model. This chapter is concerned only with the Data Link layer.

802.2: Logical Link Control The Data Link layer of the OSI Model is divided into two separate sublayers: Media Access Control (MAC) layer Logical Link Control (LLC) layer. The 802.2 standard defines how network communications should take place within the LLC sublayer. The LLC communicates upward to the Network layer using either connectionless or connection-oriented modes. The LLC also monitors the flow of data between nodes and conducts error checking through the use of cyclical redundancy checks (CRC).

802.3: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Defines Ethernet networking standards. Also called the “DIX” standard. Provides rules concerning how stations communicate while sharing a common cabling system. Uses a bus topology. (continued)

CSMA/CD (continued) Uses the following media: Thinnet (10Base2): Support data transfer speeds of 10 Mbps. Segments are limited to 185 meters (approximately 607 feet). If additional length is needed, a repeater is required. Thicknet (10Base5): Supports data transfer speeds of 10 Mbps. Segments can extend 500 meters (approximately 1,640 feet). If additional length is needed, a repeater is required. Twisted pair wiring (10BaseT): Shielded or unshielded twisted pair cable (STP or UTP). Supports a data transfer rate up to 100 Mbps. Segment between network devices (when wired as a star) can extend 100 meters (approximately 328 feet).

802.5: Token Ring Token Ring or token passing networks use a token that travels around the ring, from computer to computer. Since there is only one token, there are no collisions. Uses a ring topology. Supports a data transfer rate up to 16 Mbps. Commonly uses UTP, STP or fiber-optic cable.

802.11: Wireless LANS Provide network access for computing devices without regard for where they are physically located. Devices use radio waves rather than network cabling. The 802.11 standard addresses transmission requirements at both the Physical and Media Access Control layers of the OSI Model. The Physical layer handles the actual data transmission duties between devices. (continued)

802.11: Wireless LANS (continued) The Media Access Control layer controls the network access method. Use the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) access method. The 802.11b standard boosted wireless network speeds to 11Mbps. 802.11g raises transmission rates to 54 Mbps provided short distances are used.