Website http://academy-khi.com/ <br />Facebook https://www.facebook.com/academykhi/ <br />Twitter https://twitter.com/academy_khi <br /> <br />Ethernet Introduction <br /> <br />Ethernet is the name of LAN standard defined by IEEE 802.3. It was basically introduced as a LAN technology.With the introduction of Gb Ethernet. Now It is MAN and WAN standard. <br /> <br />Shared access network technology <br />Link layer technology <br />Use CSMA/CD <br />Backoff Algorithm <br />Low Cost <br />Easy to implement <br />Easy to manage <br /> <br /> <br /> <br /> <br />History <br /> <br />Aloha <br /> <br />Developed by Bob Metcalfe and others at Xerox PARC in mid-1970s. <br /> <br />If receive Ack then communication success otherwise send again. It was designed for 3Mb/s. <br /> <br />Slotted Aloha <br /> <br />Delay of transmission of collided packet for a random time. <br /> <br />DIX Ethernet in 1980 <br /> <br />DIX was developed by three organizations Digital, Intel, and xerox. In 1980 DIX Ethernet v.1 was introduced with the speed of 10Mb/s. <br /> <br />Project 802 of IEEE <br />In 1985 IEEE started a project 802. Named for the year and month ('80 Feb). Its goal was to set standards to establish communication between devices. It defines a family of protocols at Data link and physical layers. Ethernet10BaseT was introduced. Manchester encoding. <br /> <br />802.1--overview of project 802, including higher layers and internetworking <br />802.2-logical link control (LLC) <br />802.3- Ethernet - carrier sense multiple access with collision detect (CSMA/CD. <br />802.4-token bus <br />802.5-token Ring <br />802.6-metropolitan area network <br />802.7-broadband technology <br />802.8-optical fiber technology <br />802.9-voice/data integration on LANs <br />802.10-standard for interoperable LAN security <br />IEEE 802.3 Data Link Layer = LLC + MAC <br />In ethernet architecture, data link layer is divided into two parts <br /> <br />LLC (Logical link control) <br /> <br />Upper layer communication <br />Flow control <br />Link establishment and termination <br />Framing <br />Interconnectivity between data link layer of different LAN. <br />MAC(Media access control) <br /> <br />Error Checking <br />Media access control <br />Frame transmission and its recovery in case of failure. <br />Interaction with physical layer <br />IEEE 802.3 CSMA/CD <br />CSMA = First listen then speak. <br /> <br />CD= While speaking, listen also. If someone speaking, stop. <br /> <br />Medium is idle, transmit. <br /> <br />Medium busy, wait for free and then transmit imeediately. <br /> <br />If collision detected during transmission, Transmit a jam signal of high voltage. It is just like “Stop I m talking at this time”. <br /> <br />Backoff Algorithm <br /> <br />Wait for sometime. Reattempt if problem not resolved. If continue problem then go home and come again. <br /> <br />Ethernet Frame. <br />Minimum packet size is 64 bytes. <br />18 header bytes and 46 data bytes. <br />If less than 46 bytes to send, then add dummy bits to increase the length to 46 bytes. <br />Maximum packet size 1518 bytes <br /> <br />Preamble: <br /> <br />7 bytes with pattern 101010...............1010101010 used for clock synchronization. <br />eighth byte is start of frame (10101011) <br /> <br />Addresses: <br /> <br />6 bytes (Source and Destination MAC address). <br /> <br />Type/length: <br /> <br />Indicates the type of the Network layer protocol.mostly IP but may be Novell IPX and AppleTalk. <br />Allow multiple network layer protocols to be supported on a single machine (multiplexing). <br />Identifies the length of data field. <br /> <br />CRC: <br /> <br />It checks errors at receiver, if detected, frame discard. <br /> <br />Data: <br /> <br />It is sequence of bits less than or equal to 1500. carries data from the upper-layer protocols. <br /> <br />Pad: <br /> <br />Zeros are added to the data field to make the minimum data length = 46 bytes. <br /> <br />Ethernet media. <br />Data rate (10, 100, 1,000). <br />10, 100, 1,000Mbps. <br /> <br />Signaling method (base, broad). <br />Baseband. <br />Broadband. <br /> <br />Cabling (2, 5, T, F, S, L). <br />5 - Thick coax (original Ethernet cabling). <br />F – Optical fiber. <br />S – Short wave laser over multimode fiber. <br />L – Long wave laser over single mode fiber. <br /> <br />Twisted pair <br />10-BaseT twisted pair standard <br /> <br />Coaxial cable <br />10Base2 Thin coaxial standard. <br />10Base5 Thick coaxial standard <br /> <br />Fiber Optic <br />10Base-FL <br />100Base-Sx <br />100Base-Lx
