Fundamentals of Networking


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  • This is intended to be a very general overview of the concepts in computer networking and communication.
  • Potential topics: TCP/IP and the Internet TCP and UDP Gateway and Routing Protocols Telnet and FTP TCP/IP Configuration TCP/IP and Networks Domain Name Service Network File System
  • Transmitter: modem Transmission system: public telephone network Receiver: modem Destination: server
  • Transmitter: modem Transmission system: public telephone network Receiver: modem Destination: server
  • Network - A group of computers connected together in a way that allows information to be exchanged between the computers. Node - Anything that is connected to the network. While a node is typically a computer, it can also be something like a printer or CD-ROM tower. Segment - Any portion of a network that is separated, by a switch, bridge or router, from other parts of the network. Backbone - The main cabling of a network that all of the segments connect to. Typically, the backbone is capable of carrying more information than the individual segments. For example, each segment may have a transfer rate of 10 Mbps (megabits per second: 1 million bits a second), while the backbone may operate at 100 Mbps. Topology - The way that each node is physically connected to the network.
  • Backbone example: E.g. each segment may have a transfer rate of 10Mbps (megabits per second or 1 million bits a second) while the backbone may operate at 100Mbps
  • Similar to a bus network, rings have nodes daisy chained, but the end of the network in a ring topology comes back around to the first node, creating a complete circuit. Each node takes a turn sending and receiving information through the use of a token. The token along with any data is sent from the first node to the second node which extracts the data addressed to it and adds any data it wishes to send. Then second node passes the token and data to the third node, etc. until ti comes back around to the first node again. Only the node with the token is allowed to send data . All other nodes must wait for the token to come to them.
  • A hub does not perform any type of filtering or routing of the data. A hub is a junction that joins all the different nodes together.
  • A hub does not perform any type of filtering or routing of the data. A hub is a junction that joins all the different nodes together.
  • Baud – don’t use; a single state change can involve more than a single bit of data
  •  we will talk about network cables next
  • CAT 5 is currently under consideration to be incorporated into the Gigabit Ethernet specification for short distance wiring. While longer connections using Gigabit Ethernet use optical fiber, the goal is to leverage the CAT 5 twisted-pair wiring most organizations already have in place for connections out to the desktop.
  • Use of optical fibers over ; Optical fiber (or "fiber optic") refers to the medium and the technology associated with the transmission of information as light pulses along a glass or plastic wire or fiber. Optical fiber carries much more information than conventional copper wire and is in general not subject to electromagnetic interference and the need to retransmit signals. Most telephone company long-distance lines are now of optical fiber. Transmission on optical fiber wire requires repeater at distance intervals. The glass fiber requires more protection within an outer cable than copper. For these reasons and because the installation of any new wiring is labor-intensive, few communities yet have optical fiber wires or cables from the phone company's branch office to local customers (known as local loop). single mode fiber fiber is used for longer distances; multimode fiber fiber is used for shorter distances.
  • Multimode has a larger core than single mode optical fiber
  • DirectDuo DirectPC
  • In wireless LAN (WLAN) technology, 802.11 refers to a family of specifications developed by a working group of the Institute of Electrical and Electronics Engineers ( IEEE ). There are three specifications in the family: 802.11, 802.11a, and 802.11b. All three of the above mentioned specifications use CSMA/CD carrier sense multiple access with collision detection ( CSMA/CD )as the path sharing protocol. If a source station has a data packet to send, the station checks the system to see if the path medium is busy. If the medium is not busy, the packet is sent; if the medium is busy, the station waits until the first moment that the medium becomes clear. Testing is done repeatedly by the source via a short test message called RTS (ready to send). The data packet is not transmitted until the destination station returns a confirmation message called CTS (clear to send). If two stations send at exactly the same time, CSMA/CD prevents the loss of data that might otherwise occur and provides a system for retrying. The 802.11 and 802.11b specifications apply to wireless Ethernet LANs, and operate at frequencies in the 2.4-GHz region of the radio spectrum. Data speeds are generally 1 Mbps or 2 Mbps for 802.11, and 5.5 Mbps or 11 Mbps for 802.11b, although speeds up to about 20 Mbps are realizable with 802.11b. The 802.11b standard is backward compatible with 802.11. The modulation used in 802.11 has historically been phase-shift keying ( PSK ). The modulation method selected for 802.11b is known as CCK (complementary code keying), which allows higher data speeds and is less susceptible to multipath-propagation interference. The 802.11a specification applies to wireless ATM systems and operates at radio frequencies between 5 GHz and 6 GHz. A modulation scheme known as OFDM (orthogonal frequency-division multiplexing) makes possible data speeds as high as 54 Mbps, but most commonly, communications takes place at 6 Mbps, 12 Mbps, or 24 Mbps.
  • Nowadays you see hubs with switches; but basically the hub is the place where data comes together while the switch determines how and where data is forwarded from the place where data comes together.
  • bridge In telecommunication networks, a bridge is a product that connects a local area network (LAN) to another local area network that uses the same protocol (for example, Ethernet or token ring). You can envision a bridge as being a device that decides whether a message from you to someone else is going to the local area network in your building or to someone on the local area network in the building across the street. A bridge examines each message on a LAN, "passing" those known to be within the same LAN, and forwarding those known to be on the other interconnected LAN (or LANs). In bridging networks, computer or node addresses have no specific relationship to location. For this reason, messages are sent out to every address on the network and accepted only by the intended destination node. Bridges learn which addresses are on which network and develop a learning table so that subsequent messages can be forwarded to the right network. Bridging networks are generally always interconnected local area networks since broadcasting every message to all possible destinations would flood a larger network with unnecessary traffic. For this reason, router networks such as the Internet use a scheme that assigns addresses to nodes so that a message or packet can be forwarded only in one general direction rather than forwarded in all directions. A bridge works at the data-link (physical network) level of a network, copying a data frame from one network to the next network along the communications path. A bridge is sometimes combined with a router in a product called a brouter.
  • The range for WAN transmission will vary: 56 Kb/s to 1.544 Mb/s
  • Communication path established between two
  • What is the third generation speed for ISDN?
  • The 802.3 standards put down in writing what happens at the very basest level of network communication: that which actually travels through the wires and hardware.
  • Structure of protocols architecture: file transfer module contains all logic for file transfer applications (transmitting passwords, file commands, and file records). Need is to transmit the files and commands reliably. Some sorts of reliability are relevant to a variety of applications (e.g. e-mail, document transfer) Met by separate communication service modules that can be used by a variety of applications. Communication service modules assumes two computer systems are active and ready for data transfer, and keeps track of data being exchanged to assure delivery. A structured set of modules are used that implements the communication functions.
  • It is use to guide product implementors so that their products will consistently work with other products.
  • OSI divides telecommunication into seven layers. The layers are in two groups. The upper four layers are used whenever a message passes from or to a user. The lowest three layers (Up to network layer) are used when any message passes through the host computer. Message intended for this computer pass to the upper layers. Message destined for some other host are not passed up to the upper layers but are forwarded to another host. Physical layer: Bit stream through network at electrical/mechanical level
  • There are several higher layer application protocols that use TCP/IP to get to the internet. They include World Wide Web’s Hypertext Transfer Protocol; File Transfer Protocol (FTP); Telnet (Telnet) [ allow you to logion to remote computers], Simple Mail Transfer Protocol (SMTP) These and other protocols are often packaged together as a suite. TCP keep track of the individual packets that a message is divided into for efficient routing through the internet
  • Fundamentals of Networking

    1. 1. Network Fundamentals: Introduction to Network Structure and Protocol LAN, WAN, TCP/IP Prepared & Presented by: Muhammad Junaid Assistant Manager Corporate Services Dancom Online Services (PVT) Ltd. Feb 10, 2007
    2. 2. Outline <ul><li>Basic concepts in communications </li></ul><ul><li>Understanding Networking. </li></ul><ul><li>Understanding Transmission Medium (Network Cables) </li></ul><ul><li>Understanding Network Hardware </li></ul><ul><li>WAN and LAN </li></ul><ul><li>Understanding Network Protocols </li></ul>
    3. 3. Basic Concepts in Communication
    4. 4. Basic Concepts <ul><li>Communications – activity associated with distributing or exchanging information </li></ul><ul><li>Telecommunications – technology of communications at a distance that permits information to be created any where and used everywhere with little delay </li></ul><ul><li>Today it, involves </li></ul><ul><ul><li>Data: digital and analog </li></ul></ul><ul><ul><li>Voice: spoken word </li></ul></ul><ul><ul><li>Video: telecommunication imaging </li></ul></ul>
    5. 5. Essentials for Communications <ul><li>Must have a message </li></ul><ul><li>Message must have a transmitter </li></ul><ul><li>Message must have a medium </li></ul><ul><li>Message must be understood </li></ul><ul><li>Message must have some level of security </li></ul>Source  Transmitter  Transmission  Receiver  Destination Source System Destination System Workstation/PC Workstation/PC Medium 1 2 3 4 5 6
    6. 6. Essentials for Communications Source  Transmitter  Transmission  Receiver  Destination Source System Destination System Workstation/PC Workstation/PC Medium 1 2 3 4 <ul><li>Text input information </li></ul><ul><li>Input data digital bit stream </li></ul><ul><li>Transmitted analog signal </li></ul><ul><li>Received analog signal </li></ul><ul><li>Output data digital bit stream </li></ul><ul><li>Text output information </li></ul>5 6
    7. 7. Data Communication Tasks Routing Delivery Error Feedback Network MGT Flow Control Signal Distortion Bit Error Network MGT Error Detection & Correction Nature and Timing of Signal Security Exchange Management Signal Begins & Ends Messsage Formatting Synchronization Repeater/Amplifier; Propagation; Interoperable Recovery Signal Generation Router / Server / Media Control / Protocol Routing Interfacing Multiplexing Capacity Congestion Control Addressing Data System Utilization
    8. 8. Understanding Networking
    9. 9. Big Picture What do you see here for a typical network?
    10. 10. Key Network Terminology Explained (1) <ul><li>Networks needs to interconnect at a distance by a form of point to point or point to multiple point connected media </li></ul><ul><li>A network is a group of computers connected together in such a way as to allow </li></ul><ul><li>Networks that are interconnected have proven to be low cost, reliable, and efficient means of communicating at a distance </li></ul>
    11. 11. Key Network Terminology Explained (2) <ul><li>Node: anything connected to the network, usually a computer, but it could be a printer or a scanner </li></ul><ul><li>Segment: any portion of a network that is separated by a switch, bridge or a router from another part of a network. </li></ul><ul><li>Backbone: the main cabling of a network that all of the segment connect to. Usually, the backbone is capable of carrying more information than the individual segments. </li></ul><ul><li>Topology: The way each node is physically connected to the network </li></ul>Network architecture 
    12. 12. Common Topologies - Bus <ul><li>Bus: each node is daisy-chained (connected one right after the other) along the same backbone. Information sent from a node travels along the backbone until it reaches its destination node. Each end of a bus network must be terminated with a resistor to keep the </li></ul>
    13. 13. Common Topologies - Ring <ul><li>Ring: Similar to a bus network, rings have nodes daisy chained, but the end of the network in a ring topology comes back around to the first node, creating a complete circuit. Each node takes a turn sending and receiving information through the use of a token. The token along with any data is sent from the first node to the second node which extracts the data addressed to it and adds any data it wishes to send. Then second node passes the token and data to the third node, etc. until it comes back around to the first node again. Only the node with the token is allowed to send data . All other nodes must wait for the token to come to them. </li></ul>
    14. 14. Common Topologies - Star <ul><li>In a star network, each node is connected to a central device called a hub. The hub takes a signal that comes from any node and passes it along to all the other nodes in the network. </li></ul><ul><li>A hub does not perform any type of filtering or routing of the data. </li></ul><ul><li>A hub is a junction that joins all the different nodes together. </li></ul>
    15. 15. Common Topologies - Star <ul><li>In a star network, each node is connected to a central device called a hub. The hub takes a signal that comes from any node and passes it along to all the other nodes in the network. </li></ul>
    16. 16. Common Topologies – Star Bus <ul><li>Prob. Most common topology used today. Combines elements of the star and bus topologies to create a versatile network environment. </li></ul><ul><li>Nodes in particular areas are connected to hubs (and create star topology), and hubs are connected together along the network backbone (like a bus network). </li></ul><ul><li>Often you have stars nested within stars. </li></ul>
    17. 17. Other network topologies (architecture) <ul><li>Some basic network topologies not previously mentioned: </li></ul><ul><li>One-to-one </li></ul><ul><li>Hierarchical </li></ul><ul><li>Hybrid </li></ul><ul><li>Client-server </li></ul><ul><li>Multiple nodes </li></ul>
    18. 18. Key Network Terminology Explained (3) <ul><li>Simplex: information flows in only one direction </li></ul><ul><li>Half-duplex: information flows in two directions, but only in one direction at a time. </li></ul><ul><li>Full-duplex: information flows in two directions at the same time </li></ul>
    19. 19. Basic Signal Terminologies <ul><li>Bit: binary digit, either 0 or 1 </li></ul><ul><li>Baud (don’t really use anymore; not accurate) = one electronic state change per second </li></ul><ul><li>Bit rate – a method for measuring data transmission speed – bits per second </li></ul><ul><li>Mbps – millions of bits per second (data speed; measure of bandwidth = total information flow over a given time) on a telecommunication medium </li></ul><ul><li>8 bits = 1 byte </li></ul><ul><li>Mb – million bits (quantity of data) </li></ul><ul><li>MB – million bytes (quantity of data) </li></ul><ul><li>Gbps – Billion bits per second (data speed) </li></ul><ul><li>Teraflops – trillion operations per second </li></ul>Kilo K 2^10 Mega M 2^20 Giga G 2^30 Tera T 2^40 Peta P 2^50 Exa E 2^60 Zetta Z 2^70 Yotta Y 2^80
    20. 20. Data Transmission <ul><li>Successful transmission of data depends on: </li></ul><ul><ul><li>The quality of the signal being transmitted </li></ul></ul><ul><ul><li>Characteristics of the transmission medium </li></ul></ul><ul><li>Data rate – bits per second in data communications </li></ul><ul><li>Bandwidth – bandwidth or signal is constrained by the transmitter and the nature of the transmission in cycles per second or hertz </li></ul><ul><li>Noise – Average level of noise over the communication path. </li></ul><ul><li>Error rate – rate at which errors occur where error in 1 or 0 bit occurs </li></ul>
    21. 21. Understanding Transmission Medium
    22. 22. Basic transmission medium concepts <ul><li>Medium is the physical path between transmitter and receiver in a data transmission system </li></ul><ul><li>Guided Medium: waves are guided along a solid medium path (twisted pair, coaxial cable, and optical fiber). </li></ul><ul><li>Unguided medium: waves are propagated through the atmosphere and inner/outerspace (satellite, laser, and wireless transmissions). </li></ul>
    23. 23. Medium examples by type <ul><li>Conductive: twisted pairs and coaxial cables </li></ul><ul><li>Electromagnetic: microwave </li></ul><ul><li>Light: lasers and optical fibers (need clear line of sight) </li></ul><ul><li>Wireless – inner/outerspace; satellite (omnidirectional  security issues) </li></ul>
    24. 24. Coaxial cable (1) <ul><li>Widely installed for use in business and corporation ethernet and other types of LANs. </li></ul><ul><li>Consists of inter copper insulator covered by cladding material, and then covered by an outer jacket </li></ul><ul><li>Physical Descriptions: </li></ul> Covered by sheath material  Outer conductor is braided shielded (ground)  Separated by insulating material  Inner conductor is solid copper metal
    25. 25. Coaxial cable (2) <ul><li>Applications: </li></ul><ul><ul><li>TV distribution (cable tv); long distance telephone transmission; short run computer system links </li></ul></ul><ul><ul><li>Local area networks </li></ul></ul><ul><li>Transmission characteristics: </li></ul><ul><ul><li>Can transmit analog and digital signals </li></ul></ul><ul><ul><li>Usable spectrum for analog signaling is about 400 Mhz </li></ul></ul><ul><ul><li>Amplifier needed for analog signals for less than 1 Km and less distance for higher frequency </li></ul></ul><ul><ul><li>Repeater needed for digital signals every Km or less distance for higher data rates </li></ul></ul><ul><ul><li>Operation of 100’s Mb/s over 1 Km. </li></ul></ul>
    26. 26. Twisted Pair Cables <ul><li>Physical description: </li></ul><ul><ul><li>Each wire with copper conductor </li></ul></ul><ul><ul><li>Separately insulated wires </li></ul></ul><ul><ul><li>Twisted together to reduce cross talk </li></ul></ul><ul><ul><li>Often bundled into cables of two or four twisted pairs </li></ul></ul><ul><ul><li>If enclosed in a sheath then is shielded twisted pair (STP) otherwise often for home usage unshielded twisted pair (UTP). Must be shield from voltage lines </li></ul></ul><ul><li>Application: </li></ul><ul><ul><li>Common in building for digital signaling used at speed of 10’s Mb/s (CAT3) and 100Mb/s (CAT5) over 100s meters. </li></ul></ul><ul><ul><li>Common for telephone interconnection at home and office buildings </li></ul></ul><ul><ul><li>Less expensive medium; limited in distance, bandwidth, and data rate. </li></ul></ul>
    27. 27. Categories of Twisted Pairs Cabling System Specs describe cable Material, type of Connectors, and Junction blocks to Conform to a category 100 Mbps 20 Mbps 16 Mbps 4 Mbps Less than 1 Mbps Maximum data rate Usual application Category 100 Mbps TPDDI 155 Mbps asynchronous transfer mode (certify 100 Mhz signal) CAT 5 Used in 16Mbps Token Ring Otherwise not used much CAT 4 Voice and data on 10BASE-T Ethernet (certify 16Mhz signal) CAT 3 Mainly used in the IBM Cabling System for token ring networks CAT 2 analog voice (plain old telephone service) Integrated Services Digital Network Basic Rate Interface in ISDN Doorbell wiring CAT 1
    28. 28. Optical Fibers (1) <ul><li>Physical Description: </li></ul><ul><ul><li>Glass or plastic core of optical fiber = 2to125 µm </li></ul></ul><ul><ul><li>Cladding is an insulating material </li></ul></ul><ul><ul><li>Jacket is a protective cover </li></ul></ul><ul><ul><li>Laser or light emitting diode provides transmission light source </li></ul></ul><ul><li>Applications: </li></ul><ul><ul><li>Long distance telecommunication </li></ul></ul><ul><ul><li>Greater capacity; 2 Gb/s over 10’s of Km </li></ul></ul><ul><ul><li>Smaller size and lighter weight </li></ul></ul><ul><ul><li>Lower attenuation (reduction in strength of signal) </li></ul></ul><ul><ul><li>Electromagnetic isolation – not effected by external electromagnetic environment. Aka more privacy </li></ul></ul><ul><ul><li>Greater repeater spacing – fewer repeaters, reduces line regeneration cost </li></ul></ul>Repeaters 
    29. 29. Optical Fibers (2) <ul><li>multimode fiber is optical fiber that is designed to carry multiple light rays or modes concurrently, each at a slightly different reflection angle within the optical fiber core. used for relatively short distances because the modes tend to disperse over longer lengths (this is called modal dispersion) . </li></ul><ul><li>For longer distances, single mode fiber (sometimes called monomode) fiber is used. In single mode fiber a single ray or mode of light act as a carrier </li></ul>
    30. 30. Wireless Transmission (1) <ul><li>Frequency range (line of sight): </li></ul><ul><ul><li>26 GHz to 40 GHz: for microwave with highly directional beam as possible </li></ul></ul><ul><ul><li>30 MHz to 1 GHz: for omni directional applications </li></ul></ul><ul><ul><li>300MHz to 20000 GHz: for infrared spectrum; used for point to point and multiple point application (line of sight) </li></ul></ul><ul><li>Physical applications: </li></ul><ul><ul><li>Terrestrial microwave – long haul telecommunication service (alternative to coaxial or optical fiber) </li></ul></ul><ul><ul><li>Few amplifier and repeaters </li></ul></ul><ul><ul><li>Propagation via towers located without blockage from trees, etc (towers less than 60 miles apart) </li></ul></ul>
    31. 31. Wireless Transmission (2) <ul><li>Satellite is a microwave relay station </li></ul><ul><li>Geostationary orbit (22,000 miles) and low orbit (12000 miles) </li></ul><ul><li>Satellite ground stations are aligned to the space satellite, establishes a link, broadcast at a specified frequency. Ground station normally operate at a number of frequencies – full duplex </li></ul><ul><li>Satellite space antenna is aligned to the ground station establishes a link and transmits at the specified frequency. Satellite are capable of transmitting at multiple frequencies simultaneously, full duplex. </li></ul><ul><li>To avoid satellites from interfering with each other, a 4 degree separation is required for 4/6 GHz band and 3 degree for 12/14 GHz band. Limited to 90 satellites. </li></ul><ul><li>Disadv: not satellite repair capability; greater delay and attenuation problems. </li></ul>
    32. 32. Wireless LAN <ul><li>Wireless LAN </li></ul><ul><li>HiperLAN (European standard; allow communication at up to 20 Mbps in 5 GHz range of the radio frequency (RF) spectrum. </li></ul><ul><li>HiperLAN/2 operate at about 54 Mbps in the same RF band. </li></ul>
    33. 33. Network Hardware
    34. 34. Hubs <ul><li>A hub is the place where data converges from one or more directions and is forwarded out in one or more directions. </li></ul><ul><li>Seen in local area networks </li></ul>Reference to equipment
    35. 35. Gateways <ul><li>A gateway is a network point that acts as an entrance to another network. On the internet, in terms of routing, the network consists of gateway nodes and host nodes. </li></ul><ul><li>Host nodes are computer of network users and the computers that serve contents (such as Web pages). </li></ul><ul><li>Gateway nodes are computers that control traffic within your company’s network or at your local internet service provider (ISP) </li></ul>
    36. 36. Routers <ul><li>A router is a device or a software in a computer that determines the next network point to which a packet should be forwarded toward its destination. </li></ul><ul><li>Allow different networks to communicate with each other </li></ul><ul><li>A router creates and maintain a table of the available routes and their conditions and uses this information along with distance and cost algorithms to determine the best route for a given packet. </li></ul><ul><li>A packet will travel through a number of network points with routers before arriving at its destination. </li></ul>
    37. 37. Bridge <ul><li>a bridge is a product that connects a local area network (LAN) to another local area network that uses the same protocol (for example, Ethernet or token ring). </li></ul><ul><li>A bridge examines each message on a LAN, &quot;passing&quot; those known to be within the same LAN, and forwarding those known to be on the other interconnected LAN (or LANs). </li></ul>
    38. 38. What is the difference between? <ul><li>Bridge: device to interconnect two LANs that use the SAME logical link control protocol but may use different medium access control protocols. </li></ul><ul><li>Router: device to interconnect SIMILAR networks, e.g. similar protocols and workstations and servers </li></ul><ul><li>Gateway: device to interconnect DISSIMILAR protocols and servers, and Macintosh and IBM LANs and equipment </li></ul>
    39. 39. Switches <ul><li>Allow different nodes of a network to communicate directly with each other. </li></ul><ul><li>Allow several users to send information over a network at the same time without slowing each other down. </li></ul>
    40. 40. WANs and LANs
    41. 41. Major Categories of Networks <ul><li>Local Area Networks (LAN) </li></ul><ul><ul><li>A network of computers that are in the same general physical location, within a building or a campus. </li></ul></ul><ul><li>Metropolitan Area Networks (MAN) </li></ul><ul><li>Wide Area Networks (WAN) </li></ul><ul><li>Issues of size and breadth. </li></ul>
    42. 42. Data Communications Through WANs (1) <ul><li>WANs were developed to communicate over a large geographical area (e.g. lab-to-lab; city-to-city; east coast-to-west coast; North America-to-South America etc) </li></ul><ul><li>WANs require the crossing of public right of ways (under control and regulations of the interstate commerce and institute of telephone and data communications established by the gov’t and international treaties). </li></ul><ul><li>WANs around the world relies on the infrastructure established by the telephone companies (“common carrier”) or public switched telephone network (PSTN). </li></ul><ul><li>WANs consists of a number of interconnected switching nodes (today = computers). Transmission signals are routed across the network automatically by software control to the specified destination. The purpose of these nodes are to route messages through switching facilities to move data from node to node to its destination. </li></ul>
    43. 43. Data Communications Through WANs (2) <ul><li>WANs originally implemented circuit switching and packet switching technologie s. Recently, frame relay and asynchronous transfer mode (ATM) networks have been implemented to achieve higher operating and processing speeds for the message. </li></ul><ul><li>WAN transmission speeds are _______ </li></ul><ul><li>WAN are owned by the common carrier in the U.S. and governement in most foreign countries. </li></ul><ul><li>Interconnected devices, I.e. LANs or Personal Computers (PC) or Workstation or Servers can be (usually are) privately owned by companies. </li></ul>
    44. 44. Circuit Switching Technologies <ul><li>Circuit switching is a dedicated communications path established between two stations or multiple end points through nodes of the WAN </li></ul><ul><li>Transmission path is a connected sequence of physical link between nodes. </li></ul><ul><li>On each link, a logical channel is dedicated to the connection. Data generated by the source station are transmitted along dedicated path as rapidly as possible. </li></ul><ul><li>At each node, incoming data are routed or switched to the appropriate outgoing channel without excessive delay. However, if data processing is required, some delay is experienced. </li></ul><ul><li>Example of circuit switching above is the telephone networks. </li></ul>
    45. 45. Packet Switching Technologies <ul><li>It is not necessasry (as in circuit switching) to dedicate transmission capacity along a path through the WAN rather data are sent out in a sequence of small chucks, called packets . </li></ul><ul><li>Each packet, consisting of several bits is passed through the network from node to node along some path leading from the source to the destination </li></ul><ul><li>At each node along the path, the entire packet is received, stored briefly, and then transmitted to the next node. </li></ul><ul><li>At destination all individual packets are assembled together to form the complete text and message from the source. Each packet is identified as to its place in the overall text for reassembly. </li></ul><ul><li>Packet switching networks are commonly used for terminal-to-computer and computer-to-computer communications. </li></ul><ul><li>If packet errors occur, the packet is retransmitted. </li></ul>
    46. 46. Frame Relay Techniques <ul><li>Packet switching was developed at a time (1960’s) when digital long distance transmission facilities exhibited a relatively high error rate compared to today’s facilities. A large amount of overhead was included for error detection and control. Each packet included additional bits and each node performed additional processing to insure reliable transmission. </li></ul><ul><li>Frame relay has removed the overhead bits and additional processing. It has become unnecessary to invoke these overhead checks and thereby enables higher capacity transmission rates. </li></ul><ul><li>Frame relay takes advantage of these high rates and low error rates. </li></ul><ul><li>Frame relay networks are designed to operate efficiently at user data rates of 2 Mb/s and higher. (packet switching originally designed with a 64 Kb/s data rate to the end user). </li></ul><ul><li>Frame relay achieves these higher rates by stripping out most of the overhead involved with error control. </li></ul>
    47. 47. Asynchronous Transfer Mode (ATM) <ul><li>ATM also referred to as “Cell Relay” </li></ul><ul><li>Evolution from frame relay and circuit switching. </li></ul><ul><li>Major differences: Frame relay uses variable length packets called “frames”. ATM uses fixed length packets called “cells”. </li></ul><ul><li>ATM provides little overhead for error control like frame relay, and depends on inherent reliability of the transmission system and on higher layers of logic in the end systems to identify and correct errors. </li></ul><ul><li>ATM is designed to operate in range of 10s to 100 Mb/s compared to frame relay (2 Mb/s) </li></ul><ul><li>ATM allows multiple virtual channels with higher data rates for transmission paths. Each channel dynamically sets on demand. </li></ul>
    48. 48. ISDN and Broadband ISDN Technology <ul><li>Integrated services digital network (ISDN) was intended to be a world wide public telecommunication network to replace existing public telecommunication networks and deliver a wide variety of services. </li></ul><ul><li>ISDN has standardized user interfaces, implemented a set of digital switches and paths supporting a broad range of traffic types and providing a value added processing service </li></ul><ul><li>ISDN is multiple networks, but integrated to provide user with single, uniform accessibility and world wide interconnection. </li></ul><ul><li>First generation ISDN was narrowband, 64 Kb/s channel of switching and circuit switching orientations. Frame relay resulted from the ISDN narrowband efforts. </li></ul><ul><li>Second generation is broadband ISDN. It supports high data rates of 100s Mb/s and has a packet switching orientation. ATM resulted from the broadband ISDN efforts. </li></ul>
    49. 49. Local Area Network <ul><li>Small interconnected of personal computers or workstations and printers within a building or small area up to 10 Kms. </li></ul><ul><li>Small group of workers that share common application programs and communication needs. </li></ul><ul><li>LANs are capable of very high transmission rates (100s Mb/s to G b/s). </li></ul><ul><li>LAN equipment usually owned by organization. Medium may be owned or leased from telephone company provider or common carrier. </li></ul><ul><li>PC or Workstation interconnected to medium (twisted pair; fiber optics; etc) through concentrators to servers. LAN is interconnected with other networks via switches and router/gateways. </li></ul><ul><li>Advanced LANs using circuit switching are available. ATM LANs, fibre channel baseband, and broadband LANs are being used. Etc. </li></ul><ul><li>Ethernet </li></ul><ul><li>Token Ring </li></ul>
    50. 50. What is ethernet? <ul><li>A group of standards for defining a local area network that includes standards in cabling and the structure of the data sent over those cables as well as the hardware that connects those cables. </li></ul><ul><li>Independent of the network architecture </li></ul><ul><li>Flavors of ethernet </li></ul><ul><li>IEEE 802.3 Ethernet Specification </li></ul><ul><ul><li>Great detail specifying cable types, data formats, and procedures for transferring that data through those cables </li></ul></ul><ul><li>IEEE 802.5 Token Ring Specification </li></ul>
    51. 51. Network Interface Card (NIC) <ul><li>Every computer and most devices (e.g. a network printer) is connected to network through an NIC. In most desktop computers, this is an Ethernet card (10 or 100 Mbps) that is plugged into a slot on the computer motherboard. </li></ul>
    52. 52. How does Ethernet work? <ul><li>Using MAC addresses to distinguish between machines, Ethernet transmits frames of data across baseband cables using CSMA/CD (IEEE 802.3) </li></ul>
    53. 53. What is a MAC Address? <ul><li>Media Access Control (MAC) Address – are the physical address of any device, e.g. a NIC in a computer on the network. The MAC address has two parts of 3 bytes long. The first 3 bytes specify the company that made the NIC and the second 3 bytes are the serial number of the NIC. </li></ul>
    54. 54. What is a Token Ring? <ul><li>All computers are connected in a ring or star topology and a binary digit or token passing scheme is used in order to prevent the collision of data between two computers that want to send messages at the same time. </li></ul>
    55. 55. How do Token Rings work? <ul><li>Empty information frames are continuously circulated on the ring. </li></ul><ul><li>When a computer has a message to send, it inserts a token in an empty frame (this may consist of simply changing a 0 to a 1 in the token bit part of the frame) and inserts a message and a destination identifier in the frame. </li></ul><ul><li>The frame is then examined by each successive workstation. If the workstation sees that it is the destination for the message, it copies the message from the frame and changes the token back to 0. </li></ul><ul><li>When the frame gets back to the originator, it sees that the token has been changed to 0 and that the message has been copied and received. It removes the message from the frame. </li></ul><ul><li>The frame continues to circulate as an &quot;empty&quot; frame, ready to be taken by a workstation when it has a message to send. </li></ul>
    56. 56. Understanding Network Protocols
    57. 57. Protocols of Computer Communications and Networks <ul><li>Protocol are used for communication between computers in different computer networks. Protocol achieves: </li></ul><ul><ul><li>What is communicated between computers? </li></ul></ul><ul><ul><li>How it is communicated? </li></ul></ul><ul><ul><li>When it is communicated? </li></ul></ul><ul><ul><li>What conformance (bit sequence) between computers? </li></ul></ul><ul><li>Key elements of a protocol are: </li></ul><ul><ul><li>SYNTAC: Data format and signal levels </li></ul></ul><ul><ul><li>SEMANTICS: Control information for coordination and error handling </li></ul></ul><ul><ul><li>TIMING: Synchronization, speed matching, and sequencing </li></ul></ul><ul><li>Examples of protocols: </li></ul><ul><ul><li>WAN Protocol: TCP/IP </li></ul></ul><ul><ul><li>LAN Protocol: Media Access Control; Contention; Token Passing </li></ul></ul>
    58. 58. Protocol Architecture <ul><li>Architecture provides high degree of cooperation between two computers. </li></ul><ul><li>Example: </li></ul><ul><li>INSERT DIAGRAM of file transfer  </li></ul>
    59. 59. ISO/OSI Reference Model (1) <ul><li>Open Systems Interconnection </li></ul><ul><li>No one really uses this in the real world. </li></ul><ul><li>A reference model so others can develop detailed interfaces. </li></ul><ul><li>Value: The reference model defines 7 layers of functions that take place at each end of communication and with each layer adding its own set of special related functions. </li></ul><ul><li>Flow of data through each layer at one </li></ul>
    60. 60. ISO/OSI Reference Model (2) How to transmit signal; coding Hardware means of sending and  receiving data on a carrier Two party communication: Ethernet  Routing and Forwarding Address: IP  End-to-end control & error checking (ensure complete data transfer): TCP  Establish/manage connection  ASCII Text, Sound (syntax layer)  File Transfer, Email, Remote Login 
    61. 61. What is TCP/IP? <ul><li>Transmission Control Protocol (TCP) – uses a set of rules to exchange messages with other Internet points at the information packet level </li></ul><ul><li>Internet Protocol (IP) – uses a set of rules to send and receive messages at the Internet address level </li></ul><ul><li>Is the predominate network protocol in use today (Other includes OSI Model) for interoperable architecture and the internet. </li></ul><ul><li>TCP/IP is a result of protocol research and development conducted on experimental packet switched network by ARPANET funded by the defense advanced research projects agency (DARPA). TCP/IP used as internet standards by the internet architecture board (IAB). </li></ul>
    62. 62. TCP/IP Five Independent Levels <ul><li>Application Layer : contains the logic needed to support the various user applications. Separate module are required for each application. </li></ul><ul><li>Host-to-host or transport Layer : collection of mechanisms in a single and common layer </li></ul><ul><li>Internet Layer : IP provides the routing functions across the multiple networks </li></ul><ul><li>Network access layer : concerned with access to and routing data across a network for two end systems attached to the same network. </li></ul><ul><li>Physical Layer : covers physical interface between PC or workstation and a transmission medium or network </li></ul>HTTP / FTP / Telnet / SMTP / SLIP / PPP  TCP keep track of the individual packets  And reassemble IP handles actual  delivery of packets
    63. 63. TCP (example) <ul><li>Web Server: serves HTML pages </li></ul><ul><li>TCP layer in the server divides the file into one or more packets, numbers the packet, then forward packets individually to IP. </li></ul><ul><li>Note: each packet has the same destination IP address, it may get routed differently through the network. </li></ul><ul><li>TCP (on the client) reassembles the individual packets and waits until they have arrived to forward them as a single file. </li></ul><ul><li>Connection-oriented protocol </li></ul>
    64. 64. IP <ul><li>Connectionless protocol (I.e. no established connection between the end points that are communicating.) </li></ul><ul><li>Responsible for delivery the independently treated packet !!!! </li></ul><ul><li>TCP responsible for reassembly. </li></ul>
    65. 65. Associated TCP/IP Protocols & Services SLIP (Serial Line Internet Protocol) and PPP (Point to Point Protocol) encapsulate the IP packets so that they can be sent over a dial up phone connection to an access provider’s modem. SLIP/ PPP Provides meaningful names like for computers to replace numerical addresses like Stands for the Domain Name System. DNS Used to remotely manage network devices. Stands for the Simple Network Management Protocol. SNMP A remote terminal emulation protocol that enables clients to log on to remote hosts on the network. Telnet This protocol, the core of the World Wide Web, facilitates retrieval and transfer of hypertext (mixed media) documents. Stands for the HyperText Transfer protocol HTTP