LAN Protocols LAN Protocols CSE Fall Instructor N - PDF document

CSE 3213, Fall 2010 2 Aloha, CSMA, Scheduling SchemesHow to transmit data (bits) over a medium?ASK, FSK, PSK, Line Coding How to reliably transmit groups of bits(frames) over the medium?Flow & Error Control (e.g. Go-Back-N, 5Ethernet(IEEE 802.3)(IEEE 802.3) 8 9MAC Protocols: Ethernet (cont.) –7 bytes / 56 bits of alerts receiving stations of the synchronize –56 bits long , to allow stations to synchronize evenif they miss some bits at the beginning –1 byte (signals the beginning of a frame; last chance for synchronizationtwo consecutive 1-bits indicate thatDestination Address–6 bytes–6 bytescontains the physical address of the sending station 64 to 1518 bytes 11MAC Protocols: Ethernet (cont.) IEEE 802.3IEEE 802.310 Mbps10 Mbps Physical LayerPhysical Layer 10 Mbps Mthernetuses Manchester signaling–additional bandwidthto achieve better synchronization, not a big issue(10 mm)–awkward to handle and install–cheaper and easier to handle,but the length of each segment cannot exceed 200 m level of attenuation in thin coaxial cable–low-cost and prevalent in offices,but due to poor transmission qualities of twisted pair the length ofindividual links is limited to 100 m hub –multiportrepeater baseband 14Token Ring(IEEE 802.5)(IEEE 802.5) 17MAC Protocols: Token Ring (cont.) data / control frameformat: 21-byte overhead + dataformat: 3-byte–alerts arrival of a token / data / control frame–determines the frame type –token or data/controlFrame Control–indicates whether frame contains data or control info–CCITT-32 CRC checksumEnd Delimiter–signals the end of token / data frame–tells the sending device whether the destination device is on ther it copied the frame –Token frame format SD address Source address Information 6111 Data frame format SD ACED