Network Topologies.pdf

Network Topologies LANs and WANs - Geographical coverage LANs – A single geographical location, such as office building, school, etc – Typically High speed and cheaper. WANs – Spans more than one geographical location often connecting separated LANs – Slower – Cost...

Network Topologies LANs and WANs - Geographical coverage LANs – A single geographical location, such as office building, school, etc – Typically High speed and cheaper. WANs – Spans more than one geographical location often connecting separated LANs – Slower – Costly hardware, routers, dedicated leased lines and complicated implementation procedures. 1 Network Topologies Topology - Physical and logical network layout – Physical – actual layout of the computer cables and other network devices – Logical – the way in which the network appears to the devices that use it. Common topologies: – Bus, ring, star, mesh and wireless 2 1  Bus topology Uses a trunk or backbone to which all of the computers on the network connect. Systems connect to this backbone using T connectors or taps. Coaxial cablings ( 10Base-2, 10Base5) were popular options years ago. 3 Bus Topology Advantages Disadvantages Cheap and easy to implement Network disruption when computers are added or removed Require less cable A break in the cable will prevent all systems from accessing the network. Does not use any specialized network Difficult to troubleshoot. equipment. 4 2  Ring Topology Logical ring – Meaning that data travels in circular fashion from one computer to another on the network. – Typically FDDI, SONET or Token Ring technology are used to implement a ring network – Ring networks are most commonly wired in a star configuration Token Ring has multi-station access unit (MSAU),equivalent to hub or switch. MSAU performs the token circulation internally. 5 Ring Topology Advantages Disadvantages Cable faults are easily located, making Expansion to the network can cause troubleshooting easier network disruption Ring networks are moderately easy to A single break in the cable can disrupt the install entire network. 6 3  Star Topology All computers/devices connect to a central device called hub or switch. Each device requires a single cable point-to-point connection between the device and hub. Most widely implemented Hub is the single point of failure 7 Star Topology Advantages Disadvantages Easily expanded without disruption Requires more cable to the network Cable failure affects only a single A central connecting device allows user for a single point of failure Easy to troubleshoot and isolate More difficult to implement problems 8 4  Mesh Topology Each computer connects to every other. High level of redundancy. Rarely used. – Wiring is very complicated – Cabling cost is high – Troubleshooting a failed cable is tricky – A variation hybrid mesh – create point to point connection between specific network devices, often seen in WAN implementation. 9 Mesh Topology Advantages Disadvantages Provides redundant paths between Requires more cable than the other devices LAN topologies The network can be expanded Complicated implementation without disruption to current uses 10 5  Wireless networking Do not require physical cabling Particularly useful for remote access for laptop users Eliminate cable faults and cable breaks. Signal interference and security issue. 11 Wireless networking Advantages Disadvantages Allows for wireless remote access Potential security issues associated with wireless transmissions Network can be expanded without Limited speed in comparison to other disruption to current users network topologies 12 6  IEEE and Networking standards Institute of Electrical and Electronic Engineers (IEEE) developed a series of networking standards – Networking technologies developed by manufacturers are Compatible – Cabling, networking devices and protocols are all interchangeable under the banner of a specific IEEE 13 Specification Name 802.1 Internetworking 802.2 The LLC(Logincal Link Control) sublayer 802.3 CSMA/CD ( Carrier Sense Multiple Access with Collision Detection) for Ethernet networks 802.4 A token passing bus 802.5 Token Ring networks 802.6 Metropolitan Area Network (MAN) 802.7 Broadband Technical Advisory Group 802.8 Fiber-Optic Technical Advisory Group 802.9 Integrated Voice and Data Networks 802.10 Standards for Interoperable LAN/MAN Security (SILS) (Network Security) 802.11 Wireless networks 802.12 100Mbps technologies, including 100BASEVG-AnyLAN 14 7  802.3 IEEE standard Defines characteristics for Ethernet networks. New additions, – 802.3u for Fast Ethernet – 802.3z for Gigabit Ethernet, referred to as 802.3x. – …… – 802.3ac 10gbits/s, expe. 2009 – …… Speed: Original 10Mbps, Fast Ethernet 100Mbps, Gigabit Ethernet 1000Mbps Topology: bus or star. Media: Coaxial and twisted pair cabling, also fiber optic cable. Access method: CSMA/CD 15 802.5 IEEE standard Specifies the characteristics for Token Ring Networks. Introduced by IBM in the mid 80s, network topology of choice until the rise of the popularity of Ethernet. Speed: 4 to 16Mbps Topology: logical ring and most often a physical star. Logical ring is often created in the Multistation Access Unit (MSAU) Media: twisted pair cabling. 16 Access method: token passing. 8 802.11b IEEE Standard - Wireless Specifies the characteristics of wireless LAN Ethernet networks. – Special devices called wireless access points to allow communicate. – Also connect to wired networks to create wireless portions of entire networks. – Access method: Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA ), a variation of CSMA/CD. – Topology: physical wireless, logical bus Protocol – 802.11b 1999 2.4GHz, 11Mbits/s – 802.11g 2003 2.4GHz, 54 Mbits/s – 802.11n 2008 2.4G,5GHz, 248Mbits/s –... … 17 FDDI Fiber Distributed Data Interface (FDDI) standard was developed by American National Standards Institute (ANSI) Dual ring technology for fault tolerance Speed: 100Mbps or higher Topology: dual ring topology Media: fiber optic cable, > 2 kilometers. Also possible use copper wire as Copper Distributed Data Interface (CDDI). Access method: token-passing access method 18 9 Standard Speed Physical Logical Media Access Topology Topology Method 802.3 10Mbps Bus and Star Coaxial and CSMA/CD Twisted pair (802.3u) 100Mbps( Fast Star Bus Twisted pair CSMA/CD Ethernet) (802.3z) 1000Mbps Star Bus Twisted pair CSMA/CD 802.5 4Mbps and Star Ring Twisted pair Token 16Mbps passing 802.11b 11Mbps Wireless Bus Radio waves CSMA/CA FDDI 100Mbps Dual Ring Ring Fiber-optic Token Twisted passing pair/CDDI 19 10