e over several types of media, such as coaxial 2. IEEE 802.2, Logical Link Control (LLC) Protocol, common to cable, twisted pair wiring and optical fibre. The IEEE has developed the various types of media implementation. a classification system which groups local area networks according 3. IEEE 802.3, Carrier Sense Multiple Access and Collision De- to speed, signalling technique and segment length. tect. For example, the most popular type of 802.3/ Ethernet LAN is 10 4. IEEE 802.4, Token Passing Bus. Base 5. This refers to LANs over the common, thick, yellow coaxial 5. IEEE 802.5, Token Passing Ring. cable, (YE-50). The speed at which data can theoretically travel 6. IEEE 802.6, Metropolitan Networks. over this medium is 10Mbit/s, the signalling technique is baseband and the maximum segment length without signal regeneration is 500 metres, hence 10 Base 5. This particular standard requires the The ISO has adopted the IEEE standards as ISO 8802 and relates special 'thick' Ethernet cable, most often yellow or bright orange in the IEEE model to its own. (See Figure 56.14.) colour, with multiple layers of shielding. 802.1 802.2 Logical Link Control LAYER 2 DATA LINK 802.3 802.4 802.5 802.6 Token Token LAYER 1 CSMA/CD Physical M.A.N. Layer IEEE MODEL OSI MODEL Figure 56.14 IEEE and OSI Models Internetworking devices 56/11 Other 802.3 LAN standards include: 56.5.1 The repeater 10 Base 2, also known as Thinnet or Cheapernet. The repeater is the simplest form of internetworking device and 2. 1 Base 5, the original standard for the AT&T StarLan evolved first in conjunction with CSMA/CD-type networks in the 3. 10 Base T, applicable to LANs over twisted pair wiring. mid 1970s. It operates at the lowest layer of the ISO Reference 4. 10 Base F, applicable to LANs over an optical fibre. Model, i.e., the Physical Layer. (See Figure 56.15.) 5. 10 Broad 36, CSMA/CD using broadband signalling tech- niques. IEEE 802.5 has standards governing nine types of physical media, PHYSICAL PHYSICAL including shielded and unshielded twisted p