ETHERNET

1. ETHERNET By- Pankaj Bisht Ashish Patwal Rahul Dhiman

2. Ethernet (cont..) • It is a frame based Computer network Technology for Local Area Networks. • This is covered by the IEEE 802.3 standard that defines what is commonly known as the CSMA/CD protocol.

3. 64 48 48 16 32 Src Dest Preamble Type Body CRC addr addr Ethernet Overview (contd.) • Ethernet by definition is a broadcast protocol • Any signal can be received by all hosts • Switching enables individual hosts to communicate • Network layer packets are transmitted over an Ethernet by encapsulating • Frame Format CS 640

4. Ethernet (cont..) Three data rates are currently defined for operation over optical fiber and twisted-pair cables: • 10 Mbps—10Base-T Ethernet • 100 Mbps—Fast Ethernet • 1000 Mbps—Gigabit Ethernet 10-Gigabit Ethernet is under development.

5. Characterstics .. • There are other technologies but Ethernet has survived as the major LAN technology because its protocol has the following characteristics : • Is easy to understand, implement, manage, and maintain • Allows low-cost network implementations • Provides extensive topological flexibility for network installation.

6. Our Focus is Ethernet • History • Developed by Bob Metcalfe and others at Xerox PARC in mid-1970s

7. The CSMA/CD Access Method.. • Carrier Sense Multiple Access / Collision Detection, a set of rules determining how network devices respond when two devices attempt to use a data channel simultaneously (called a collision). Standard Ethernet networks use CSMA/CD to physically monitor the traffic on the line at participating stations. If no transmission is taking place at the time, the particular station can transmit. If two

8. The CSMA/CD Access Method stations attempt to transmit simultaneously, this causes a collision, which is detected by all participating stations. After a random time interval, the stations that collided attempt to transmit again. If another collision occurs, the time intervals from which the random waiting time is selected are increased step by step. This is known as exponential back off. CSMA/CD is a type of contention protocol.  Networks using the CSMA/CD procedure are simple to implement but do not have deterministic transmission characteristic

9. A begins to transmit at t=0 B A B begins to transmit at t= tprop- B detects collision at t= tprop B A A B A detects collision at t= 2 tprop- Collision Detection.

10. Ethernet Evolution • 10 Base 5 (Thicknet) (Bus Topology) • 10 Base 2 (Thinnet) (Bus Topology) • 10 Base T (UTP) (Star/Tree Topology) • 10 Base FL (Fiber) (Star/Tree Topology)

11. Ethernet Evolution 10BASE5 {1983} • 10 Mbps • 500 meter segment length • Signal-regenerating repeaters • Thick Coax • Advantages: Low attenuation, excellent noise immunity, superior mechanical strength • Disadvantages: Bulky, difficult to pull, transceiver boxes too expensive • Wiring represented a significant part of total installed cost. Networks: Ethernet

12. Ethernet BUS Topology

13. Ethernet Evolution 10BASE2 Cheapernet{1985} • 10 Mbps • 185 meter segment length • Signal-regenerating repeaters • Transceiver was integrated onto the adapter • Thin Coax (coax thinner and lighter) • Advantages: Easier to install, reduced hardware cost, BNC connectors widely deployed  lower installation costs. • Disadvantages: Attenuation not as good, could not support as many stations due to signal reflection caused by BNC Tee Connector. Networks: Ethernet

14. Ethernet Evolution 1BASE5 StarLAN{1987} • 1 Mbps • 250 meter segment length • Signal-regenerating repeaters • Transceiver integrated onto the adapter • Hub-and-Spoke topology (star topology) • Two pairs of unshielded twisted pair • Advantages: Since four or more UTP are ubiquitous in buildings, it is easier to use installed wiring in the walls. Telephone wiring is hierarchical  can use wiring closets. Networks: Ethernet

15. Ethernet Evolution 10BASET {1990}**Most popular • 10 Mbps • 100 meter segment length • Signal-regenerating repeaters • Transceiver integrated onto adapter • Two pairs of UTP • Hub-and-spoke topology {Hub in the closet} • Advantages: could be done without pulling new wires. Each hub amplifies and restores incoming signal. Networks: Ethernet

16. Ethernet STAR Topology

17. Open system interconnection • International Standard Organisation (ISO) has proposed Open System Interconnection(OSI) reference model which provides a framework of data communication protocols.OSI model addresses the problem of interconnection of different computer and associated devices.

18. Open System Interconnection Model

19. OSI Layers • Physical:To send the data bit stream over Communication network. • Data Link:To recover from Transmission error. • Network:Concerned with routing and congestion control. • Transport:To receive the data from session layer and divide it into pieces to pass it to network layer.

20. OSI Layers (contd..) • Session:Establishes a session for communication between two hosts. • Presentation:Serves as an interface between Application and Communication network. • Application:To provide the facility to use the other layer.

21. Advancement. A newer version of Ethernet, called 100Base-T (or Fast Ethernet), supports data transfer rates of 100 Mbps. And the newest version, Gigabit Ethernet supports data rates of 1 gigabit (1,000 megabits) per second.