LAN, MAN and WAN. Basics and Comparison. University of Damascus. Computer Engineering Dept. Digital Communications. By Abdulrahman Idlbi

Transcription

1 In the name of Allah, the Most Gracious, the Most Merciful University of Damascus Computer Engineering Dept. Digital Communications LAN, MAN and WAN Basics and Comparison By Abdulrahman Idlbi

2 Introduction to Networking In the early days of computing, computers were used as stand-alone devices with some attached peripherals such as printers. When the same data needed to be used on many computers, data had to be copied on floppy disks and carried on foot maybe to the desired destination. This nice kind of networking is sometimes referred to as Sneaker Net. As business and research relied more and more on computers, the so-called sneaker-net was unbearable, as it created multiple copies of the data needed to be shared. If two people modified the file and then tried to share it, one of the sets of changes would be lost. Consequently, companies invested in Local Area Networks, or LANs. The LAN allowed users within the same limited geographic area to exchange data electronically over a network. As LANs spread through companies, research centers and universities, each network had its own hardware, software and administration, and ran effectively on its own; but they were electronically isolated In mid-1980s the evolving networking technologies created a variety of software and hardware implementations as a result of the different standards followed by the manufacturing companies. This problem made network technologies incompatible to each other. One early solution was the establishing of Local Area Network (LAN) standards, which provided an open-set of guidelines for creating hardware and software. LAN standards allowed the equipment from different companies to be compatible. In LAN systems, each LAN-implemented network is an isolated electronic island. With the growth of businesses and the increasing dependency on networking, it was obvious that LAN systems were not enough. The solution was the creation of Metropolitan-Area Networks (MANs) and Wide-Area Networks (WANs), which extended internetworking connection over large geographic areas, making it possible for businesses and researchers to communicate over great distances. 1

3 Local Area Networks (LANs) LANs are used for connecting network terminals over a relatively short distance, affording a highspeed fault-tolerant data networking. They are usually owned and managed by a single person or organization. An important feature of a LAN is its topology: the layout of the connected terminals in a network. A LAN logical topology may be bus or ring topology. LANs are designed to: Operate within a limited geographic area. Allow multiple access to high-bandwidth media. Control the network privately under local administration. Provide full-time connectivity to local services. Connect physically adjacent devices. The original IEEE 802 LAN and MAN technologies were designed to be capable of supporting access domains containing at least 200 end stations and with geographical extent of at least 2 km for LANs (using Physical-layer repeaters if necessary) and 50 km for MANs. Subsequent developments in IEEE 802 LAN technology and performance have been accompanied by a reduction in the size and extent required in individual access domains, recognizing that these can readily and costeffectively be interconnected in bridged LANs that are capable of offering at least the original minimum size and extent, with increased overall bandwidth and performance. * LANs consist of: computers, network interfacing cards, peripheral devices, networking media and network devices. The used network devices are routers, bridges, hubs, Ethernet switches and repeaters. LANs can be implemented in a variety of technologies including: Ethernet, IsoEnet, Fast, Giga, 10GigE Token Ring, Token Bus 100 VG - AnyLAN FDDI (Fiber Distributed Data Interface) / CDDI (Copper Distributed Data Interface) WLAN (Wireless LAN) ATM (Asynchronous Transfer Mode) Most of LAN technologies follow the IEEE 802.x Series: Logical Link Control Ethernet (CSMA/CD) Token Bus Token Ring Isochronous Ethernet Secure Data Exchange Wireless VG-AnyLAN PAN (Bluetooth) Broadband Wireless * "IEEE Standard for Local and Metropolitan Area Networks: Overview and Architecture", Size and extent. 2

4 While FDDI follows ANSI X3T9.5 The typical access methods are CSMA/CD (carrier sense multiple access with collision detection) and Token Passing. LAN protocol functions at the two lowest layers of the OSI model (Physical and Data Link layers). The LAN speed varies among implemented technologies: Ethernet (802.3) Fast Ethernet (802.3u) Gigabit Ethernet (802.3z) 10-Gigabit Ethernet (802.3ae) Token Ring (802.5) IsoEnet (802.9) Wireless (802.11{b, a, g}) VG-AnyLAN (802.12) FDDI (X3T9.5) ATM 10 Mbps 100 Mbps 1 Gbps 10 Gbps 4, 16, 100, 1000 Mbps 16 Mbps 11, 54 Mbps 96 Mbps 100 Mbps 25, 100, 140, 155, 622 Mbps 3

5 Wide Area Networks (WANs) A WAN is a data communication network that covers a broad geographic area, and may use facilities provided by telephone companies. WANs were created to interconnect LANs, which can then provide access to computers on file servers in other locations. WANs are designed to do the following: Operate over a large geographically separated areas. Allow users to have real-time communication capabilities with other users. Provide full-time remote resources connected to local services. Provide , World Wide Web, file transfer, and e-commerce services. Some common WAN technologies are modems; Integrated Services Digital Network (ISDN); Digital Subscriber Line (DSL); Frame Relay; US (T) and Europe (E) Carrier Series T1, E1, T3, E3; and Synchronous Optical Network (SONET). The devices used in WANs are switches, access servers, modems and CSU/DSU (Channel/Data Service Unit). In terms of interconnecting the components of a WAN we have four solutions: Point-to-point link: provides a pre-established, dedicated WAN path (leased lines). Circuit switching: a dedicated circuit is established, maintained and terminated (ISDN for example). Packet switching: network devices share a single point-to-point link, so multiplexing is used. Examples include ATM, SMDS, X.25 and Frame Relay. WAN Virtual Circuits: logical circuits used to enable reliable communication among network devices (PVC, SVC). The speed of a WAN varies depending on the used technology, as the following table shows: Modem 9.6, 14.4, 19.2, 28.8, 33.6, 56 Kbps Switched 56 KBPS 56 Kbps ISDN B, BRI(2B+D) 64 Kbps, 144 Kbps ISDN PRI(23B+D) Mbps T1 (DS-1) Mbps X.25 up to (64 Kbps) 2 Mbps Frame Relay 56 Kbps-(1.544 Mbps)-36 Mbps HDSL Mbps SDSL 160 Kbps- 2 Mbps ADSL Mbps VDSL Mbps SMDS 56Kbps - 34 Mbps T3 (DS-3) Mbps SONET OC-1/STS Mbps ATM Mbps ATM DS Mbps ATM TAXI 100 Mbps ATM OC Mbps ATM OC Mbps ATM OC Gbps ATM OC Gbps ATM OC Gbps 4

6 Note: When two speeds are mentioned, the first is the upstream while the other is the downstream. Metropolitan Area Networks (MANs) A MAN is a network that spans a metropolitan area such as a city or suburban area. A MAN usually consists of two or more LANs in a common geographic area. Typically, a service provider is used to connect two or more LAN sites using private communication lines or optical services. A MAN can also be created using wireless bridge technology by beaming signals across public areas. Due to the advances in internetworking technologies, MANs recently use the same technologies and devices as WANs (check Cisco Systems Inc. website at for more information). So recent references do not usually talk much about MANs. Resources Cisco Networking Academy Program, CCNA 1, version 3, Cisco Systems, Inc IEEE Standard for Local and Metropolitan Area Networks: Overview and Architecture (IEEE Std ). Can be found at Get IEEE 802 Program ( CIS 600.2/CSE Lectures (Networking and Data Security) Fall 2006, Dr. Roman Markowski, Syracuse University ( William Stallings' "Data and Computer Communications, 8 th Edition" Website ( LAN Basics ( COM S0006) Most teachers waste their time by asking questions which are intended to discover what a pupil does not know, whereas the true art of questioning has for its purpose to discover what the pupil knows or is capable of knowing. Albert Einstein 5