Data communication and networking


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Data communication and networking

  1. 1. Topic OSI Reference Model
  2. 2. 2
  3. 3. 7) Application Layer •The Application Layer is the level of the protocol hierarchy where user-accessed network processes reside. 6) Presentation Layer •For cooperating applications to exchange data, they must agree about how data is represented 5) Session Layer •As with the Presentation Layer, the Session Layer is not identifiable as a separate layer in the TCP/IP protocol hierarchy. 4) Transport Layer •Much of our discussion of TCP/IP is directed to the protocols that occur in the Transport Layer. 3) Network Layer •The Network Layer manages connections across the network and isolates the upper layer protocols from the details of the underlying network. 2) Data Link Layer •The reliable delivery of data across the underlying physical network is handled by the Data Link Layer. 1) Physical Layer •The Physical Layer defines the characteristics of the hardware needed to carry the data transmission signal. 3
  4. 4. OSI Reference Model Simple Video Example 4
  5. 5. 5
  6. 6. Topic TCP/IP Model
  7. 7. 7
  8. 8. 5) Application Layer • Top most layer is the Application Layer where the protocols such as SMTP, FTP, SSH, HTTP, etc operate. 4) Transport Layer • Where the connection protocols such as TCP, exist. Other popular Transport Layer Protocols are UDP, DCCP, GTP, SCTP, etc. This layer not only enables opening and maintaining connections but also ensures that the message packets are received properly. 3) Internet Layer • Internet Layer which defines IP address system and the routing schemes for navigating packets from one IP address to another. Some examples of Internet Layer protocols are IPv4, IPv6, ICMP, IGMP, etc. 2) Network Interface Layer • Network Access Layer which defines the low-level protocols used for signaling and communication. Some examples of Low level protocols in Network Access Layer are PPP, FDI, Frame Relay, ATM, GPRS, etc. Specifies details of how data is physically sent through the network, including how bits are electrically signaled by hardware devices that interface directly with a network medium, such as coaxial cable, optical fiber, or twisted-pair copper wire. 1) Physical Layer • Physical Layer which constitutes of the physical equipment necessary for communications, such as twisted pair cables, equipment and system for the signaling such as Ethernet, SONET/SDH, ISDN, Modems, Routers, etc. 8
  9. 9. Error Handling 51 Addressing Connection Establishment 2 Connection Release 3 Flow Control 4 Interface and State Machine 6 Agenda of TCP/IP Model 9
  10. 10. In TCP/IP there are two main transport protocols. Transport Protocol TCP UDP Reliable: if some data is lost somewhere, TCP retransmits it Stream service: the data is delivered at destination in the order it was sent by source (sequence guarantee) Unit of information is a byte; grouping of data into blocks may be different at destination than at source In TCP (Transmission Control Protocol) In UDP (User Datagram Protocol) offers a datagram service to the application (unit of information is a message) Unreliable (message may be lost) No sequence guarantee 10
  11. 11. Topic LAN & WAN
  12. 12. share peripherals devices like printers LAN (Local Area Network) small geographic area Super cheap high-speed data network shared access to devices And so on ... Everything! 12
  13. 13. •Special security measures are needed to stop the users from using programs and data that they should not have accessed to. •Network are difficult to set up and need to be maintained by skilled technicians. •If the file servers develop a serious fault, all the users are affected, rather than just one users in the case of a standalone machine. •It needs to be on all the time. Workstations can share peripherals devices like printers. Cheaper that providing a printer for each computer. Workstations do not necessary need their own hard disk or CD-ROM drives which make them cheaper to buy than stand- alone PC. User can save their work centrally on the network’s file server. This means that they can retrieve work from any workstation on the network. They don’t need to go to the same workstation again. Advantages Disadvantages LAN 13
  14. 14. network protocols like ATM, X.25, and Frame Relay WAN (Wide Area Network) router connects LANs to WANs broad geographic area high-speed data network shared access to devices And so on ... Everything! 14
  15. 15. WAN (Wide Area Network) LAN (Local Area Network) 15
  16. 16. High Data Transfer Rates (DTR) Cover small areas such as a household or a school. Do not require leased telecommunication lines LAN Low cost. Cover wider areas such as businesses and governments. Higher speed in the multiple gigabits range WAN 16
  17. 17. Topic Network Topologies
  18. 18. ? What is Network Topology? • The physical topology of a network refers to the configuration of cables, computers, and other peripherals. Physical topology should not be confused with logical topology which is the method used to pass information between workstations. Logical topology was discussed in the Protocol chapter. • There are several basic network topologies: star, bus, ring, mesh, and hierarchical etc.. 18
  19. 19. A Star topology • A star network has a central node that connects to each of the other nodes by a single, point-to-point link. Any communication between one node and another in a star topology must pass through the central node. 19
  20. 20. Bus Topology • In a bus topology, nodes are arranged along a single length of twisted-pairwire, coaxial cable, or fiber-optic cable that can be extended at the ends. Using a bus topology, it is easy and inexpensive to add a node to the network, and losing a node in the network will not cause the network to fail. The main disadvantages to the bus topology are that a defective bus causes the entire network to fail. Also, providing a bus with inadequate bandwidth will degrade the performance of the network. 20
  21. 21. •There is a limit on central cable length and number of nodes that can be connected. •Dependency on central cable in this topology has its disadvantages.If the main cable (i.e. bus ) encounters some problem, whole network breaks down. •Proper termination is required to dump signals. Use of terminators is must. •It is difficult to detect and troubleshoot fault at individual station. •It is not suitable for networks with heavy traffic. It is easy to set-up and extend bus network. Cable length required for this topology is the least compared to other networks. Bus topology costs very less. Linear Bus network is mostly used in small networks. Good for LAN. Advantages Disadvantages Bus Topology 21
  22. 22. Ring Topology • A network topology that is set up in a circular fashion in which data travels around the ring in one direction and each device on the right acts as a repeater to keep the signal strong as it travels. Each device incorporates a receiver for the incoming signal and a transmitter to send the data on to the next device in the ring. The network is dependent on the ability of the signal to travel around the ring. 22
  23. 23. A mesh Topology • A mesh network design is one in which each device is connected to every other device located on the network, like a spider web. The advantage to this design is the redundancy of the connected devices; if one link fails, it will not affect the rest of the network. The disadvantages of this design are the cost of all the required medium and limited scalability. If you add a device to a network that currently has four devices, then you must connect the new device to the four existing devices with individual cable drops. 23
  24. 24. Hierarchical Topology • In a hierarchical topology, nodes are arranged like an inverted tree with the root (usually the mainframe computer) as the highest level and the leaves (usually the desktop computers) as the lowest level. It is very cheap, but may have possible traffic jams at the top level. 24
  25. 25. Hybrid Topology • In a hybrid topology, nodes are arranged in more than one topology, which may include star, ring, and hierarchical . A hybrid topology can integrate together various computer configurations that may have special reasons for their own choice of topology. A hybrid network will allow companies to pick the advantages from several different topologies. 25
  26. 26. Topic Network Technologies
  27. 27. Packet Switching In packet-based networks, the message gets broken into small data packets. These packets are sent out from the computer and they travel around the network seeking out the most efficient route to travel as circuits become available. This does not necessarily mean that they seek out the shortest route. Each packet may go a different route from the others. 27
  28. 28. •Under heavy use there can be a delay •Data packets can get lost or become corrupted •Protocols are needed for a reliable transfer •Not so good for some types data streams (e.g. real-time video streams can lose frames due to the way packets arrive out of sequence) Security Bandwidth used to full potential Devices of different speeds can communicate Not affected by line failure (redirects signal) Availability – no waiting for a direct connection to become available During a crisis or disaster, when the public telephone network might stop working, e-mails and texts can still be sent via packet switching Advantages Disadvantages Packet Switching 28
  29. 29. Circuit Switching Circuit switching was designed in 1878 in order to send telephone calls down a dedicated channel. This channel remains open and in use throughout the whole call and cannot be used by any other data or phone calls. 29
  30. 30. •Inefficient – the equipment may be unused for a lot of the call; if no data is being sent, the dedicated line still remains open. •It takes a relatively long time to set up the circuit. •During a crisis or disaster, the network may become unstable or unavailable. •It was primarily developed for voice traffic rather than data traffic. Circuit is dedicated to the call – no interference, no sharing Guaranteed the full bandwidth for the duration of the call Guaranteed quality of service Advantages Disadvantages Circuit Switching 30
  31. 31. ? What is Frame Relay? Frame Relay is a packet switching technology for connecting network points in Wide Area Networks (WAN). It is a connection oriented data service and establishes a virtual circuit between two end points. Data transfer is done in packets of data known as frames. These frames are variable in packet size and more efficient due to flexible transfers. Frame Relay was originally introduced for ISDN interfaces though it is currently used over a variety of other network interfaces as well. In Frame Relay, connections are called as ‘Ports’. All the points which need to connect to the frame relay network needs to have a port. Every port has a unique Address. A frame is made of two parts which can be called as ‘actual data’ and the ‘frame relay header’. Frame architecture is same as defined for LAP-D (Link Access Procedures on the D channel) which has a variable length for information field. These frames are sent over Virtual Connections. Frame Relay can create multiple redundant connections among various routers, without having multiple physical links. Since frame relay is not specific for media, and provides means to buffer speed variations, it has the possibility to create a good interconnect medium between different types of network points with different speeds. 31
  32. 32. ? What is ATM? ATM is a network switching technology that uses a cell based methodology to quantize data. ATM data communication consists of fixed size cells of 53 bytes. An ATM cell contains a 5 byte header and 48 bytes of ATM payload. This smaller size, fixed-length cells are good for transmitting voice, image and video data as the delay is minimized. ATM is a connection oriented protocol and therefore a virtual circuit should be established between sending and receiving points. It establishes a fixed route between two points when the data transfer starts. ATM is designed to be convenient for hardware implementation and therefore processing and switching have become faster. Bit rates on ATM networks can go up to 10 Gbps. ATM is a core protocol used over the SONET/SDH backbone of the ISDN. ATM provides a good quality of service in networks where different types of information such as data, voice, and are supported. With ATM, each of these information types can pass through a single network connection. 32
  33. 33. Topic Transmission Medium
  34. 34. There are two main types of transmission medium Transmission Medium Guided (Wired) Unguided (Wireless) Bandwidth higher bandwidth gives higher data rate Transmission impairments e.g.. attenuation Interference Number of receivers in guided media more receivers introduces more attenuation Design Factors 34
  35. 35. Transmission Characteristics of Guided Media Frequency Range Typical Attenuation Typical Delay Repeater Spacing Twisted pair (with loading) 0 to 3.5 kHz 0.2 dB/km @ 1 kHz 50 µs/km 2 km Twisted pairs (multi-pair cables) 0 to 1 MHz 0.7 dB/km @ 1 kHz 5 µs/km 2 km Coaxial cable 0 to 500 MHz 7 dB/km @ 10 MHz 4 µs/km 1 to 9 km Optical fiber 186 to 370 THz 0.2 to 0.5 dB/km 5 µs/km 40 km 35
  36. 36. Twisted Pair • analog – needs amplifiers every 5km to 6km • digital – can use either analog or digital signals – needs a repeater every 2-3km • limited distance • limited bandwidth (1MHz) • limited data rate (100MHz) • susceptible to interference and noise 36
  37. 37. Coaxial Cable • superior frequency characteristics to TP • performance limited by attenuation & noise • analog signals – amplifiers every few km – closer if higher frequency – up to 500MHz • digital signals – repeater every 1km – closer for higher data rates 37
  38. 38. Optical Fiber • greater capacity – data rates of hundreds of Gbps • smaller size & weight • lower attenuation • electromagnetic isolation • greater repeater spacing – 10s of km at least 38
  39. 39. network protocols like ATM, X.25, and Frame Relay WAN (Wide Area Network) router connects LANs to WANs broad geographic area high-speed data network shared access to devices And so on ... Everything! 39
  40. 40. Wireless Transmission Frequecies 2GHz to 40GHz 30MHz to 1GHz 3 x 1011 to 2 x 1014 microwave highly directional point to point satellite omnidirectional broadcast radio Infrared local 40
  41. 41. Antennas • electrical conductor used to radiate or collect electromagnetic energy • transmission antenna – radio frequency energy from transmitter – converted to electromagnetic energy byy antenna – radiated into surrounding environment • reception antenna – electromagnetic energy impinging on antenna – converted to radio frequency electrical energy – fed to receiver • same antenna is often used for both purposes 41
  42. 42. Radiation Pattern • power radiated in all directions • not same performance in all directions – as seen in a radiation pattern diagram • an isotropic antenna is a (theoretical) point in space – radiates in all directions equally – with a spherical radiation pattern 42
  43. 43. Terrestrial Microwave • used for long haul telecommunications • and short point-to-point links • requires fewer repeaters but line of sight • use a parabolic dish to focus a narrow beam onto a receiver antenna • 1-40GHz frequencies • higher frequencies give higher data rates • main source of loss is attenuation – distance, rainfall • also interference 43
  44. 44. Satellite Microwave • satellite is relay station • receives on one frequency, amplifies or repeats signal and transmits on another frequency – eg. uplink 5.925-6.425 GHz & downlink 3.7-4.2 GHz • typically requires geo-stationary orbit – height of 35,784km – spaced at least 3-4° apart • typical uses – television – long distance telephone – private business networks – global positioning 44
  45. 45. Satellite Point to Point Link 45
  46. 46. Satellite Broadcast Link 46
  47. 47. Broadcast Radio • radio is 3kHz to 300GHz • use broadcast radio, 30MHz - 1GHz, for: – FM radio – UHF and VHF television • is omnidirectional • still need line of sight • suffers from multipath interference – reflections from land, water, other objects 47
  48. 48. Infrared • modulate noncoherent infrared light • end line of sight (or reflection) • are blocked by walls • no licenses required • typical uses – TV remote control – IRD port 48
  49. 49. Wireless Propagation Ground Wave 49
  50. 50. Wireless Propagation Sky Wave 50
  51. 51. Wireless Propagation Line of Sight 51
  52. 52. Topic Communication
  53. 53. Connections between devices may be classified into three categories Simplex. This is a unidirectional connection, i.e., data can only travel in one direction. Simplex connections are useful in situations where a device only receives or only sends data (e.g., a printer). Half-duplex. This is a bidirectional connection, with the restriction that data can travel in one direction at a time. Full-duplex. This is a bidirectional connection in which data can travel in both directions at once. A full- duplex connection is equivalent to two simplex connections in opposite directions.
  54. 54. Topic Network Units
  55. 55. Segment •If the transport protocol is TCP, the unit of data sent from TCP to network layer is called Segment. Datagram •This is used in 2 layers. If the network protocol is IP, the unit of data is called Datagram. At transport layer, if protocol is UDP, we use datagram there as well. Hence, we differentiate them as UDP Datagram, IP Datagram. Frame •The term frame is most frequently used to describe a chunk of data created by network communication hardware such as a network interface cards (NIC cards) and router interfaces. Switch ports primarily forward existing frames and don't usually create frames of their own (unless they are participating in Spanning Tree or dynamic VLANs etc.) Packet •It is a more generic term used either transport layer or network layer. TCP Packet, UDP Packet, IP Packet etc. I have not seen it to represent Physical layer data units. Fragment •When a unit of data is chopped up by a protocol to fit the MTU size, the resultant unit of data is called Fragments. PDU •A protocol data unit is a term used in much of the documentation and educational literature for networking technologies. It simply means a chunk of data created and/or labled by a particular protocol. TCP, UDP, IP, OSPF and RIP (and other protocols) could be said to create "protocol data units". The term is somewhat synonymous with packet or frame, especially when used in the process of discussing routing protocols or spanning tree. 55
  56. 56. Topic Switching Technologies
  57. 57. •Switch will save the entire packet to the buffer and check it for errors or other problems before sending. •If the packet has an error, it is discarded. •Entire packet is processed •Packets are filtered • Bad packets are filtered A packet switch where the switch starts forwarding that frame (or packet) before the whole frame has been received, normally as soon as the destination address is processed. This technique reduces latency through the switch, but decreases reliability Reads only part of the packet  The addresses header  Packet is forwarded accordingly Bad packets are not filtered Cut through Swtich Straight and Forward Switch Bus Topology 57
  58. 58. Topic Network Connectors
  59. 59. Hubs are Layer-1 devices that physically connect network devices together for communication. Hubs can also be referred to as repeaters. Hubs provide no intelligent forwarding whatsoever. Hubs are incapable of processing either Layer-2 or Layer-3 information, and thus cannot make decisions based on hardware or logical addressing. Multilayer switching is a generic term, referring to any switch that forwards traffic at layers higher than Layer-2. Thus, a Layer-3 switch is considered a multilayer switch, as it forwards frames at Layer-2 and packets at Layer-3. A Layer-4 switch provides the same functionality as a Layer-3 switch, but will additionally examine and cache Transport- layer application flow information, such as the TCP or UDP port. Layer-3 routing is the process of forwarding a packet from one network to another network, based on the Network-layer header. Routers build routing tables to perform forwarding decisions, which contain the following: • The destination network and subnet mask • The next hop router to get to the destination network • Routing metrics and Administrative Distance A switch is defined as a device that allows a LAN to be segmented. -The segments will operate under the same protocol Improve the network performance and reliability Better manage the network in general. 59
  60. 60. 1 OSI Reference Model 2 TCP/IP Model 3 LAN and WAN 4 Network Topologies 5 Network Technologies Topics list covered in the assignment Huh, Finally Done! 6 Transmission Medium 7 Communication 8 Network Units 9 Switching Technologies 10 Network Connectors
  61. 61. QUESTIONS ?
  62. 62. THANK YOU!