Lec 3 Physical and Data Link PDF

Chapter 3 Underlying Technology TCP/IP Protocol Suite 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. OBJEC...

Chapter 3 Underlying Technology TCP/IP Protocol Suite 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. OBJECTIVES:  To briefly discuss the technology of dominant wired LANs, Ethernet, including traditional, fast, gigabit, and ten-gigabit Ethernet.  To briefly discuss the technology of wireless WANs, including IEEE 802.11 LANs, and Bluetooth.  To briefly discuss the technology of point-to-point WANs including 56K modems, DSL, cable modem, T-lines, and SONET.  To briefly discuss the technology of switched WANs including X.25, Frame Relay, and ATM.  To discuss the need and use of connecting devices such as repeaters (hubs), bridges (two-layer switches), and routers (three-layer switches). TCP/IP Protocol Suite 2 Chapter 3.1 Wired Local Area Network Outline 3.2 Wireless LANs 3.3 Point-to-Point WANs 3.4 Switched WANs 3.5 Connecting Devices TCP/IP Protocol Suite 3  3-1 WIRED LOCAL AREA NETWORKS A local area network (LAN) is a computer network that is designed for a limited geographic area such as a building or a campus. Although a LAN can be used as an isolated network to connect computers in an organization for the sole purpose of sharing resources, most LANs today are also linked to a wide area network (WAN) or the Internet. The LAN market has seen several technologies such as Ethernet, token ring, token bus, FDDI, and ATM LAN, but Ethernet is by far the dominant technology. TCP/IP Protocol Suite 4  Topics Discussed in the Section IEEE Standards Frame Format Addressing Ethernet Evolution Standard Ethernet Fast Ethernet Gigabit Ethernet Ten-Gigabit Ethernet TCP/IP Protocol Suite 5  Figure 3.1 IEEE standard for LANs TCP/IP Protocol Suite 6  Figure 3.2 Ethernet Frame TCP/IP Protocol Suite 7  Figure 3.3 Maximum and minimum lengths TCP/IP Protocol Suite 8  Note Minimum length: 64 bytes (512 bits) Maximum length: 1518 bytes (12,144 bits) TCP/IP Protocol Suite 9  Figure 3.4 Ethernet address in hexadecimal notation TCP/IP Protocol Suite 10  Figure 3.5 Unicast and multicast addresses unicast: 0 multicast: 1 TCP/IP Protocol Suite 11  Note The broadcast destination address is a special case of the multicast address in which all bits are 1s. TCP/IP Protocol Suite 12  Note 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. TCP/IP Protocol Suite 13 Example 3.1 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 (even). b. This is a multicast address because 7 in binary is 0111 (odd). c. This is a broadcast address because all digits are F’s. TCP/IP Protocol Suite 14 Example 3.2 Show how the address 47:20:1B:2E:08:EE is sent out on line. Solution The address is sent left-to-right, byte by byte; for each byte, it is sent right-to-left, bit by bit, as shown below: ← 11100010 00000100 11011000 01110100 00010000 01110111 TCP/IP Protocol Suite 15  Figure 3.6 Ethernet evolution through four generations TCP/IP Protocol Suite 16  Figure 3.7 Space/time model of a collision in CSMA B starts C starts at time t1 at time t2 A B C D Area where A’s signal exists Area where both signals exist Area where B’s signal exists Time Time TCP/IP Protocol Suite 17  Figure 3.8 Collision of the first bit in CSMA/CD TCP/IP Protocol Suite 18 Example 3.3 In the standard Ethernet, if the maximum propagation time is 25.6 μs, what is the minimum size of the frame? Solution The frame transmission time is Tfr = 2 × Tp = 51.2 μs. This means, in the worst case, a station needs to transmit for a period of 51.2 μs to detect the collision. The minimum size of the frame is 10 Mbps × 51.2 μs = 512 bits or 64 bytes. This is actually the minimum size of the frame for Standard Ethernet, as we discussed before. TCP/IP Protocol Suite 19  Figure 3.9 CSMA/CD flow diagram TCP/IP Protocol Suite 20 TCP/IP Protocol Suite 21  Figure 3.10 Standard Ethernet implementation TCP/IP Protocol Suite 22 TCP/IP Protocol Suite 23  Figure 3.11 Fast Ethernet implementation TCP/IP Protocol Suite 24 TCP/IP Protocol Suite 25  Note In the full-duplex mode of Gigabit Ethernet, there is no collision; the maximum length of the cable is determined by the signal attenuation in the cable. TCP/IP Protocol Suite 26  Figure 3.12 Gigabit Ethernet implementation TCP/IP Protocol Suite 27 TCP/IP Protocol Suite 28  3-2 WIRELESS LANS Wireless communication is one of the fastest growing technologies. The demand for connecting devices without the use of cables is increasing everywhere. Wireless LANs can be found on college campuses, in office buildings, and in many public areas. In this section, we concentrate on two wireless technologies for LANs: IEEE 802.11 wireless LANs, sometimes called wireless Ethernet, and Bluetooth, a technology for small wireless LANs. TCP/IP Protocol Suite 29  Topics Discussed in the Section IEEE 802.1 MAC Sublayer Addressing Mechanism Bluetooth TCP/IP Protocol Suite 30  Figure 3.13 Basic service sets (BSSs) TCP/IP Protocol Suite 31  Figure 3.14 Extended service sets (ESSs) TCP/IP Protocol Suite 32  Figure 3.15 CSMA/CA flow diagram TCP/IP Protocol Suite 33  Figure 3.16 CSMA/CA and NAV Source Destination All other stations DIFS 1 RTS SIFS CTS 2 SIFS NAV 3 Data (No carrier sensing) SIFS ACK 4 Time Time Time Time TCP/IP Protocol Suite 34  Figure 3.17 Frame format TCP/IP Protocol Suite 35 TCP/IP Protocol Suite 36  Figure 3.18 Control frames TCP/IP Protocol Suite 37 TCP/IP Protocol Suite 38 TCP/IP Protocol Suite 39  Figure 3.19 Hidden station problem TCP/IP Protocol Suite 40  Note The CTS frame in CSMA/CA handshake can prevent collision from a hidden station. TCP/IP Protocol Suite 41  Figure 3.20 Use of handshaking to prevent hidden station problem B A C RTS CTS CTS Time Time Time TCP/IP Protocol Suite 42  Figure 3.21 Exposed station problem TCP/IP Protocol Suite 43  Figure 3.22 Use of handshaking in exposed station problem RTS RTS CTS RTS RTS Data CTS Data Collision here TCP/IP Protocol Suite 44  Figure 3.23 Piconet TCP/IP Protocol Suite 45  Figure 3.24 Scatternet TCP/IP Protocol Suite 46  Figure 3.25 Frame format types 72 bits 54 bits 0 to N bits Access code Header Data TCP/IP Protocol Suite 47  3-3 POINT-TO-POINT WANS A second type of network we encounter in the Internet is the point-to-point wide area network. A point-to-point WAN connects two remote devices using a line available from a public network such as a telephone network. We discuss traditional modem technology, DSL line, cable modem, T-lines, and SONET. TCP/IP Protocol Suite 48  Topics Discussed in the Section 65K Modems DSL Technology Cable Modem T Lines  SONET PPP TCP/IP Protocol Suite 49  Figure 3.26 56K modem Downloading, Uploading, no quantization noise quantization noise TCP/IP Protocol Suite 50  Note ADSL is an asymmetric communication technology designed for residential users; it is not suitable for businesses. TCP/IP Protocol Suite 51  Figure 3.27 Bandwidth division TCP/IP Protocol Suite 52  Figure 3.28 ADSL and DSLAM TCP/IP Protocol Suite 53  Figure 3.29 Cable bandwidth TCP/IP Protocol Suite 54  Figure 3.30 Cable modem configuration TCP/IP Protocol Suite 55 TCP/IP Protocol Suite 56 TCP/IP Protocol Suite 57  Figure 3.31 PPP frame TCP/IP Protocol Suite 58  3-4 SWITCHED WANS The backbone networks in the Internet can be switched WANs. A switched WAN is a wide area network that covers a large area (a state or a country) and provides access at several points to the users. Inside the network, there is a mesh of point- to-point networks that connects switches. The switches, multiple port connectors, allow the connection of several inputs and outputs. Switched WAN technology differs from LAN technology in many ways. TCP/IP Protocol Suite 59  Topics Discussed in the Section X.25 Frame Relay ATM TCP/IP Protocol Suite 60  Note A cell network uses the cell as the basic unit of data exchange. A cell is defined as a small, fixed-size block of information. TCP/IP Protocol Suite 61  Figure 3.32 ATM multiplexing A3 A2 A1 B1 C3 B2 A3 C2 B1 A2 C1 A1 B2 C3 C2 C1 TCP/IP Protocol Suite 62  Figure 3.33 Architecture of an ATM network TCP/IP Protocol Suite 63  Figure 3.34 Virtual circuit TCP/IP Protocol Suite 64  Note A virtual connection is defined by a pair of numbers: the VPI and the VCI. TCP/IP Protocol Suite 65  Figure 3.35 ATM layers TCP/IP Protocol Suite 66  Figure 3.36 Use of the layers TCP/IP Protocol Suite 67  Note The IP protocol uses the AAL5 sublayer. TCP/IP Protocol Suite 68  Figure 3.37 AAL5 TCP/IP Protocol Suite 69  Figure 3.38 ATM layer TCP/IP Protocol Suite 70  Figure 3.39 An ATM cell TCP/IP Protocol Suite 71  3-5 CONNECTING DEVICES LANs or WANs do not normally operate in isolation. They are connected to one another or to the Internet. To connect LANs and WANs together we use connecting devices. Connecting devices can operate in different layers of the Internet model. We discuss three kinds of connecting devices: repeaters (or hubs), bridges (or two-layer switches), and routers (or three-layer switches). TCP/IP Protocol Suite 72  Topics Discussed in the Section Repeaters Bridges Routers TCP/IP Protocol Suite 73  Figure 3.40 Connecting devices TCP/IP Protocol Suite 74  Figure 3.41 Repeater or hub Sent Maintained TCP/IP Protocol Suite 75  Note A repeater forwards every bit; it has no filtering capability. TCP/IP Protocol Suite 76  Note A bridge has a table used in filtering decisions. TCP/IP Protocol Suite 77  Note A bridge does not change the physical (MAC) addresses in a frame. TCP/IP Protocol Suite 78  Figure 3.42 Bridge Bridge table Address Port 71:2B:13:45:61:41 1 71:2B:13:45:61:42 2 64:2B:13:45:61:12 3 64:2B:13:45:61:13 4 TCP/IP Protocol Suite 79  Figure 3.43 Learning bridge Address Port a. Original Address Port Address Port 71:2B:13:45:61:41 1 Address Port 71:2B:13:45:61:41 1 64:2B:13:45:61:13 4 71:2B:13:45:61:41 1 64:2B:13:45:61:13 4 71:2B:13:45:61:42 2 64:2B:13:45:61:13 4 71:2B:13:45:61:42 2 64:2B:13:45:61:12 3 c. After D sends a frame to B d. After B sends a frame to A e. After C sends a frame to D M M M M TCP/IP Protocol Suite 80  Note A router is a three-layer (physical, data link, and network) device. TCP/IP Protocol Suite 81  Note A repeater or a bridge connects segments of a LAN. A router connects independent LANs or WANs to create an internetwork (internet). TCP/IP Protocol Suite 82  Figure 3.44 Routing example TCP/IP Protocol Suite 83  Note A router changes the physical addresses in a packet. TCP/IP Protocol Suite 84