Networking Fundamentals CMPSC 255 Fall 2004
Aims • By the end of this Module you should be able to: • Briefly outline the history of networking. • Identify devices used in networking. • Understand the role of protocols in networking. • Define LAN, WAN, MAN, and SAN. • Explain VPNs and their advantages. • Describe the differences between intranets and extranets. • Explain bandwidth in networking as units of measurement. • Explain the difference between bandwidth and throughput. • Calculate data transfer rates. • Describe the OSI Model in relation to Layers, Functions, Protocols and Devices • Identify the four layers of the TCP/IP model and describe the similarities and differences between the two models.
Network Evolution • Sneakernet • Used when few computers were available • Stand alone computers • Files transferred by copying to disk and physically delivering it to destination • Makes it difficult to track current file version • Wastes time
Network Evolution • Local Area Networks • Connected computers on a shared medium • Enabled users to share files electronically • More efficient • Standards developed to allow equipment from different vendors to interoperate
Wide Area Networks As corporations grew wider communication was needed Each branch of a corporation became isolated Files sent by post or courier Solution WAN standards developed Companies were able to communicate with other networks globally Network Evolution
Network Terminology • Network Devices
Topologies • Network Topologies Describe • Structure of the network • Physical Layout of Cabling (Physical Topology) • How the media is accessed by communicating hosts (Logical Topology) • Common Physical Topologies
Bus Topology • Uses a single backbone cable that is terminated at both ends. • All the hosts connect directly to this backbone • Bandwidth is shared between the number of hosts on Network • Can be Logical or Physical
Star Topology • A star topology connects all cables to a central point of concentration • Can be a Logical Bus or Ring • Concentrator can be a • Hub • Switch • MSAU
Ring Topology • Connects one host to the next and the last host to the first • This creates a physical ring of cable • Can be Logical or Physical
Extended Star Topology • Links individual star wired network segments together • Uses hubs and/or switches • This topology can extend the scope and coverage of the network
Hierarchical Topology • Similar to an extended star • Instead of linking the hubs and/or switches together, the system is linked to a computer that controls the traffic on the topology
Mesh Topology • Implemented to provide as much protection as possible from interruption of service • The use of a mesh topology in the networked control systems of a nuclear power plant would be an excellent example • Each host has its own connections to all other hosts. • Internet has multiple paths to any one location but it does not adopt the full mesh topology.
Logical Topologies • Defines how the hosts communicate across the medium • The two most common types of logical topologies are: • Broadcast topology • means that each host sends its data to all other hosts on the network medium. There is no order that the stations must follow to use the network. • It is first come, first serve. Ethernet works this way as will be explained later in the course. • Token passing • controls network access by passing an electronic token sequentially to each host. • When a host receives the token, that host can send data on the network. If the host has no data to send, it passes the token to the next host and the process repeats itself. • Two examples of networks that use token passing are Token Ring and Fiber Distributed Data Interface (FDDI). • A variation of Token Ring and FDDI is Arcnet. Arcnet is token passing on a bus topology.
Network Protocols • Protocol suites are collections of protocols that enable network communication from one host through the network to another host. • A protocol is a formal description of a set of rules and conventions that govern a particular aspect of how devices on a network communicate. • Protocols determine the format, timing, sequencing, and error control in data communication. • Protocols control data communication, which include the following: • How the physical network is built • How computers connect to the network • How the data is formatted for transmission • How that data is sent • How to deal with errors
Network Protocols • Protocols are created and maintained by organizations and committees such as: • Institute of Electrical and Electronic Engineers (IEEE) • American National Standards Institute (ANSI) • Telecommunications Industry Association (TIA) • Electronic Industries Alliance (EIA) • International Telecommunications Union (ITU)
Local Area Networks (LANs) • LANs consist of the following components: • Computers • Network interface cards • Peripheral devices • Networking media • Network devices
LAN Components • LANs are designed to: • Operate in a limited geographical area • Allow multiple access to high-bandwidth media • Control the network privately under local administrative control • Provide full time connectivity to local services • Connect physically adjacent devices
WAN Components • WANs are designed to: • Operate over a large geographical area • Allow access over serial interfaces at lower speeds • Provide full and part time connectivity • Connect devices separated over wide, even global areas
LAN and WAN Technologies • Common LAN technologies are: • Ethernet • Token Ring • FDDI • 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 • Synchronous Optical Network (SONET)
Metropolitan Area Network • A network that spans a metropolitan area such as a city or suburban area. • Usually consists of two or more LANs in a common geographic area. • A service provider is used to connect two or more LAN sites • Can also be created using wireless technology
Storage Area Network • A dedicated, high-performance network used to move data between servers and storage resources. • SAN technology allows high-speed server-to-storage, • Offers the following features: • Availability • Scalability
Virtual Private Networks • A private network that is constructed within a public network infrastructure such as the Internet • Uses a secure tunnel through the Internet between the telecommuter’s PC and a VPN router in the headquarters
Bandwidth • Why Bandwidth is important • Bandwidth is limited by Physics and Technology • Regardless of the media used to build the network there are limits on the capacity of that network to carry information. • Bandwidth is limited by the laws of physics and by the technologies used to place information on the media. • Bandwidth is not free • WAN connectivity must be purchased from a service provider • Bandwidth requirements are growing at a rapid rate • More and more companies are using WAN services which require more and more bandwidth • Bandwidth is critical to network performance • The higher the bandwidth the more information can be transferred in a shorter time
Bandwidth • Bandwidth Analogy 1
Bandwidth Analogy 2 Bandwidth
Bandwidth • Units of Bandwidth • Bandwidth is the measure of how much information, or bits, can flow from one place to another in a given amount of time • Although bandwidth can be described in bits per second, usually some multiple of bits per second is used.
Limitations • Bandwidth is limited by a number of factors • Media • Network devices • Physics • Each have their own limiting factors • Actual bandwidth of a network is determined by a combination of the physical media and the technologies chosen for signaling and detecting network signals
Throughput • Throughput refers to actual measured bandwidth at: • a specific time of day • using specific Internet routes • and while a specific set of data is transmitted on the network. • Is determines by the following factors • Internetworking devices • Type of data being transferred • Network topology • Number of users on the network • User computer • Server computer • Power conditions
Transfer Time Calculation • Data Transfer Calculation • Best Download: T=S/BW • Typical Bandwidth: T=S/P • Where • T = Transfer time in seconds • S = Size of file in Bits • BW = Maximum theoretical bandwidth (slowest link between source and destination devices • P = Actual throughput at moment of transfer in Bps
Layered models • Using a layered model • Breaks network communication into smaller, more manageable parts. • Standardizes network components to allow multiple vendor development and support. • Allows different types of network hardware and software to communicate with each other. • Prevents changes in one layer from affecting other layers. • Divides network communication into smaller parts to make learning it easier to understand.
OSI Model • Open Standards Interconnection Model (OSI Model) • Released by International Standards Organisation (ISO) in 1984 • Standardised communications between different vendor hardware and software • Consists of 7 Layers • Each layer described a specific aspect of network communication
Layer 1 • The physical layer is concerned with transmitting raw bits over a medium • Wires • Connectors • Voltages • Data rates
Layer 2 • Controls the direct link to the media • How media is accessed • Physical addressing • Network topology • Flow control • Error Notification
Layer 3 • Logical Addressing • Best Path Determination • “Best Effort” delivery of data between networks
Layer 4 • End-to-end Connections • Concerned with transportation issues between hosts • Reliable delivery of data • Establishes, maintains and terminates virtual circuits • Error recovery and data flow
Layer 5 • Host to host communication • Establishes, manages and terminates sessions between applications
Layer 6 • Data representation • Ensure data is readable with receiving system • Data format • Data Structure • Negotiates data transfer syntax for application layer
Layer 7 • Provides network services for applications • e-mail, file transfer, terminal emulation
Peer to Peer Communication Host 1 Host 2
TCP/IP Model • Developed by the US DoD • Designed as an open standard • Is robust enough to survive any conditions (even nuclear war) • Is the standard used for communication on the Internet
TCP/IP Vs OSI TCT/IP OSI
Labs • Lab 2.3.6 • OSI Model and TCP/IP Model • Lab 2.3.7 • OSI Model Characteristics and Devices
Analog Vs Digital • Is measured by how much of the electromagnetic spectrum is occupied by each signal • The basic unit of analog bandwidth is hertz (Hz) • Units of measurement that are commonly seen are • kilohertz (KHz) • megahertz (MHz) • gigahertz (GHz). • These are the units used to describe the bandwidths of cordless telephones • Operate at either 900 MHz or 2.4 GHz. • These are also the units used to describe the bandwidths of IEEE 802.11a and 802.11b wireless networks • operate at 5 GHz and 2.4 GHz.