expanded by Jozef Goetz, 2012 The McGraw-Hill Companies, Inc., 2006

1. Lesson 6 and 7 LAN Technologies: Wired LANs - Ethernet Part I expanded by Jozef Goetz, 2012 The McGraw-Hill Companies, Inc., 2006

2. 13-1 IEEE STANDARDS • In 1985, the Computer Society of the IEEE started a project, called Project 802, to set standards to enable intercommunication among equipment from a variety of manufacturers. • Standard 802 adopted by ANSI and approved by ISO is a way of specifying functions of the physical layer and the data link layer of major LAN protocols. Topics discussed in this section: Data Link LayerPhysical Layer

3. INTRODUCTION LANs usually are owned by the organization that is using the network to interconnect equipment. LANs have much greater capacity than WAN. The key technologyingredients that determine the nature of a LAN are: [1] Topology [2] Transmission medium [3] Medium access control technique

4. LAN ARCHITECTURE • In OSI terms, higher-layer protocols (layer 3/4 & above) are independent of network architecture and are applicable to LANs & WANs. SCOPE OF IEEE 802 STANDARDS [1] LOGICAL LINK CONTROL (LLC) [2] MEDIUM ACCESS CONTROL (MAC) [3] PHYSICAL LAYER

5. Figure 13.1 IEEE standard for LANs Note: there is one LLC sublayer for all IEEE LANs

6. LAN ARCHITECTURE Physical Layer [1] Encoding/decoding of signals [2] Preamble generation/removal (synch) [3] Bittransmission/reception Medium Access Layer (MAC) [1] On transmission, assemble data into a frame with address and error-detection fields. [2] On reception, disassembleframe, and performrecognition and error detection. [3] Govern access to the LAN transmission medium

7. LAN ARCHITECTURE Logical Link Control (LLC) [1] Provide an interface to higher layers and perform flow and errorcontrol. LAN Protocols in Context

8. Figure 13.2 HDLC (typical DLL protocol) frame compared with LLC and MAC frames in the 803 IEEE standard PDU – protocol data unit

9. LOGICAL LINK CONTROL • 3 services are provided by LLC: • [1] Connection-mode service • A logical connection is set up between users. Flow/error control. • Extended HDLC format. • [2] Acknowledged connectionlessservice • No connection is setup up, but datagrams are acknowledged. • [3] Unacknowledged connectionservice • Simple, the delivery of data is not guaranteed.

10. LOGICAL LINK CONTROL

11. LOGICAL LINK CONTROL Most upper-layer protocols such as IP don’t use the services of LLC

12. Ethernet Cabling • (a)Linear – from room to room, • (b)Vertical Spine – from the basement to the roof with cables on each floor connected by repeaters, • (c) Tree, • (d)Segmented – see max in the previous slide • repeaters are the physical layer device – amplifies signals in both directions

13. Gigabit Ethernet • (a) A two-station Ethernet. • (b) A multistation Ethernet.

14. LAN TOPOLOGIES The common topologies for LANs are bus, tree, ring, and star. BUS TREE RING STAR

15. Three generations of Ethernet

16. 13-2 STANDARD ETHERNET • The original Ethernet was created in 1976 at Xerox’s Palo Alto Research Center (PARC). • Since then, it has gone through four generations. • We briefly discuss the Standard (or traditional) Ethernet in this section. Topics discussed in this section: MAC SublayerPhysical Layer

17. Figure 13.3 Ethernet evolution through four generations

18. Ethernet • • A thick coax cable was used for data transmission. • • The coax could be up to 2.5km long (with repeaters every 500 meters). • • 256 machines could connect to the cable. • • A cable with multiple machines is called a multidrop cable. • • The originalthroughput was 2.94 Mbps

19. IEEE 802.3 • Based on 1-persistent CSMA/CD with some extra features. • More commonly (but incorrectly) referred to as Ethernet. • Ethernet is the original product designed by Xerox PARC based on Bob Metcalfe's idea • It was later upgraded to 10 Mbps by Xerox, Intel and DEC. • This formed the basis for the IEEE 802.3 standard. • Which then became an ISO standard.

20. Ethernet – IEEE 802.3 in ’83. • LAN Architecture of the original Ethernet. • A multidrop cabel • A computer first listened to the cable to see if someone was already transmitting. • If so, then back off and wait a random time before retrying • If a 2nd collision happen, the random waiting time is doubled • Other standards a token bus (IEEE 802.4) and a token ring (IEEE 802.5) • Ethernet(most popular LAN) wonawar between Ethernet, token bus, token ring

21. Ethernet • • What happens when there is a collision on Ethernet? • • The terminals listen while transmitting, • and if they don’t hear the same thing that they transmitted, they jam the cable to alert the other terminals that a collision has happened. • • They then back off and wait a random time before trying again.

22. Ethernet Cabling 4 kinds of Ethernet cabling. 10Base5 => 1st one =10 means 10 Mbps – the speed in Mbps; Base = baseband transmission, 3rd one is its length rounded to 100 m (a) 10Base5, (b)10Base2 – much cheaper and easier to install, (c)10Base-T – cheapest, no share cable. (d) 10Base-F – fiber optic, excellent noise immunity, good security

23. IEEE 802.3 10-Mbps Specs (ETHERNET)

24. MAC FRAME FORMAT The MAC layerreceives a block of data from the LLC layer and is responsible for performing functions related to medium access and for transmitting the data. MAC control ex. Priority level PDU – protocol data unit

25. 802.3 MAC frame Minimum and maximum length Start Frame Delimiter next length or PDU(protocol data unit)packet physical physical • Ethernet does not provide any mechanism for acknowledging received frames, • making it what is known as an unreliable medium. • Acknowledgments must be implemented at thehigher layers.

26. 802.3 MAC frame Minimum and maximum length Start Frame Delimiter next length or PDU packet physical physical • DSAP = DestinationService AccessPoint • Defines a number to which a higher layer protocol or application is bound to at the destination, e.g. IP • SSAP = SourceService Access Point • Tells the destination which SAP to send back the response to, e.g. IP • Control information depends on the service type • Type 1 – no other information required • Type 2 – full sliding window protocolimplementation with extensions • Type 3 – basic stop and waitprotocol information

27. Ethernet addresses in hexadecimal notation • Each station on an Ethernetnetwork (such as a PC, workstation, or printer) has its ownNetwork Interface Card (NIC). • The NIC fits inside the station and provides the station with a 6-byte physical address. • written in hexadecimal notation using a hyphen to separate bytes from each other

28. Figure 13.6 Example of an Ethernet address in hexadecimal notation

29. Unicast and multicast addresses • The least significant bit of the first byte defines the type of address. • If the bit is 0, the address is unicast; otherwise, it is multicast.

30. Note The broadcast destination address is a special case of the multicast address in which all bitsare1s. FF:FF:FF:FF:FF:FF

31. Example 13.1 Define the type of the following destination addresses: a. 4A:30:10:21:10:1A b. 47:20:1B:2E:08:EE c. FF:FF:FF:FF:FF:FF • Solution • To find the type of the address, we need to look at the second hexadecimal digit from the left. • If it is even, the address is unicast. • If it is odd, the address is multicast. • If all digits are F’s, the address is broadcast. • Therefore, we have the following: • a. This is a unicast address because A in binary is 1010. • b. This is a multicast address because 7 in binary is 0111. • c. This is a broadcast address because all digits are F’s.

32. Example 13.2 Show how the address47:20:1B:2E:08:EE is sent out on line. • Solution • The address is sentleft-to-right,byte by byte; • for each byte, it is sent right-to-left, bit by bit, as shown below: • e.g. 47 = 0100 0111 => 1110 0010

33. Physical layer

34. AUI NIC – Network Interface Card

35. Function of MAU (transceiver) AUI – Attachment Unit Interface MAU – Medium Attachment Unit MDI – Medium Dependent Interface PLS – Physical Layer Signaling NIC – Network Interface Card

36. Function of MAU (transceiver) MDI – Medium Dependent Interface PLS – Physical Layer Signaling

37. NIC Evolution • Volumes for Ethernets NICs became huge • NIC becomes cheaper than the AUI cable! • Moved from 3 separate components to one integral NIC card

38. Categories of traditional Ethernet cables Thick coaxial one segment is 500m long max Thin coaxial one segment is 185m long max UTP category 5 100m max P2P Optical Fiber 2km max P2P Unshielded Twisted-Pair P2P = point-to-point

39. BUS LANs 4 media that can be used for a bus LAN: [1] Twisted pair, [2] Baseband coaxial cable, [3] Broadband coaxial cable, [4] Optical fiber. 10BASE 5 - thick cable 10BASE2 - thin cable

40. Figure 13.10 10Base5 implementation

41. Connection of a station to the medium using 10Base5 AIU cable the size of the cable, which is roughly the size of a garden hose and too stiff to bend with your hands

42. Figure 13.11 10Base2 implementation

43. Connection of stations to the medium using 10Base2 Connection of stations to the medium using 10Base5 AIU cable

44. Figure 13.12 10Base-T implementation

45. Connection of stations to the medium using 10Base-T A repeater hub connects segments of a LAN. A repeater forwards every frame; it has no filtering capability.

46. Ethernet • Ethernet now looks like a star network from a physical perspective • Hub is a half duplex device – “effectively a small piece of coaxial cable” • Collisions on a hub can still take place

47. Figure 13.13 10Base-F implementation

48. Connection of stations to the medium using 10Base-FL AUI cabel

49. Comparison of Connection of stations to the medium 10Base5 10Base2