Lec 01 and 02_Networks-mod.pdf

Introduction to Networks NSA 131 Course Objectives Understanding the basic concepts of data networks including components, layers, protocols, services, applications, and tools. Understanding the common network security vulnerabilities and threats. Develop skills of designing a network based on a...

Introduction to Networks NSA 131 Course Objectives Understanding the basic concepts of data networks including components, layers, protocols, services, applications, and tools. Understanding the common network security vulnerabilities and threats. Develop skills of designing a network based on a specific scenario setting. Develop skills of using various networking tools. Assessment Strategy Assessment through the course will be via: 1. Lecture quizzes. 2. Assignments (Sheets , Reports or Lab. Activities). 3. Mid-Term Exam. 4. Final Exam. Assessment Strategy # Assessment task Week Due Percentage of Total Assessment Sore 1 Assignments/Participation/Lab. During Semester 20 2 First Exam Week 05 15 3 Second Exam Week 09 15 4 Final Exam Week 13 40 5 Quizzes During Semester 10 Learning Resources Lecture Policy You are not allowed to attend the lecture after 5 mins of its start. You are free to ask any time in the lecture topic. If you have a question out of the lecture scope, it is preferable to ask it after the lecture or at the end of it. Don’t attend the lecture just for attendance, it won’t help you. Try to gain knowledge. CHAPTER 1 INTRODUCTION 01 Lecture Objectives 02 Benefits of computer networks. 04 Network types. 03 05 Computer Network Definition. Network components. Network topologies. What is the Computer Network?  A data communication system consists of a number of computerized devices communicated directly with each other over shared channel plus S.W [NOS] to provide services of communications. Benefits of Computer Networks Easy access and sharing of information. Sharing of expensive devices and network resources:  File Sharing.  Peripheral Sharing.  Software Sharing with multi-user licenses. Modern Technologies (IP telephony, Video Conferencing, ….etc). Shared Internet Access. Network Components S/W H /W Shared channel Wired Wireless N IC Devices End Devices Network Access ❑Repeater ❑ Hub ❑Bridge ❑Switch Application Network Devices Internetworking ❑Router NOS Hardware Components 1) Shared Channel (transmission media): ❑ Media that physically connect the computers and network devices ❑ It can be: a) Wired (cables) such as : ▪ Metallic wires - encoding into patterns of electrical impulses. ▪ Fiber optics – encoding into pulses of light (infrared or visible light ranges) b) Wireless (Air) which encoding patterns of electromagnetic waves. such as : Infrared. Bluetooth. Radio Waves Microwaves. Hardware Components (cont.) 2) NIC (Network Interface Card):  The hardware that directly access the network.  Can be:  Internal or external (USB).  Wired or Wireless 3) Devices – End Devices 3) Devices: A) End Devices: ▪ An end device is where a message originates from or where it is received. Data originates with an end device, flows through the network, and arrives at an end device. ▪ Source of applications (network aware applications). ▪ Such as : Workstations, PCs , Servers, Printers…etc. 3) Devices - Network Devices 3) Devices: B) Network Devices: ▪ Devices that interconnect different computers together. ▪ An intermediary device interconnects end devices. Examples include switches, wireless access points, routers, and firewalls. ▪ Management of data as it flows through a network is also the role of an intermediary device, including: ▪ Regenerate and retransmit data signals. ▪ Notify other devices of errors and communication failures. Hardware Components (cont.) Network Devices can be categorized into: I. Network Access Devices: Provide connectivity to the network such as: ▪ Hub: device allows different nodes to communicate with each other. ▪ Switch: Allow different nodes to communicate with each other at the same time without slowing each other down. II. ▪ Internetworking Devices: networks such as: Connect individual Router: Allow different networks to communicate with each other. HUB  Point of central connection for all of the LAN's devices.  A hub serves the same function as the shared cable in the bus.  On a hubbed LAN, devices exchange data by:  First sending it to the hub.  The hub, in turn, repeats the "message" back out to all of its connected devices “blind repeat” Switches  The most recent and most sophisticated of inter-networking devices.  Switches link devices and LANs.  They are like multi-port bridges, so they can manage complex switching among multiple LANs.  Switches segment network traffic.  Switches provide address-intelligence (filtering and forwarding) based on H/W address. Routers ❑ ❑ ❑ ❑ ❑ With a router, data passes only from one LAN to another. Routers are "intelligent" devices. It inspects the destination IP address. Based on this information it makes a routing decision. The most expensive& complicated to set up device. Classifications of Networks LAN Area MAN Network Classification WAN Sharing of Information Interchange method P2P C/S Circuit Switch Packet Switch Bus Star Topology Ring Mesh Classifications of Networks  According to covered area:  LAN.  MAN.  WAN.  According to network model (Sharing of information):  C/S.  P2P.  According to network topology:  Bus, Star, Ring, Extended Star, Mesh etc. (1) According to covered area:  Local Area Networks [LAN]:  A LAN is a group of computers connected in small geographical area.  Allow users to share files and services.  Metropolitan Area Networks [MAN]:  A MAN connects an area larger than a LAN but smaller than a WAN, such as a city.  Wide Area Networks [WAN]  A WAN is a group of computers connected in Large geographical area such as country.  A WAN often connects two LANs (WAN Link). (1) According to covered area (cont.): A LAN is a network infrastructure that spans a small geographical area. A WAN is a network infrastructure that spans a wide geographical area. LAN WAN Interconnect end devices in a limited area. Interconnect LANs over wide geographical areas. Administered by a single organization or individual. Typically administered by one or more service providers. Provide high-speed bandwidth to internal devices. Typically provide slower speed links between LANs. The Internet The internet is a worldwide collection of interconnected LANs and WANs. LANs are connected to each other using WANs. WANs may use copper wires, fiber optic cables, and wireless transmissions. The internet is not owned by any individual or group. (2) According Network Model: 1) Peer – too – Peer Networks (P2P):  In a peer-to-peer network, all computers are considered equal; they all have the same abilities to use the resources available on the network.  Example : Windows Workgroup. According Network Model (cont.): 2) Client / Server Networks(C/S):  Some nodes (SERVER) are dedicated to present services to other nodes (CLIENTS).  Examples:  Mail Server.  Web Server.  FTP Server.  DNS Server. Client Server Model (3) According to Network Topology:  Topology refers to the shape of a network, or the network's layout.  How different nodes in a network are connected to each other and how they communicate are determined by the network's topology.  The choice of topology is dependent upon:  Type and number of equipment being used.  Cost. (3) According to Network Topology: Physical topology diagrams illustrate the physical location of intermediary devices and cable installation. Logical topology diagrams illustrate devices, ports, and the addressing scheme of the network. (3) According to Network Topology: End devices on LANs are typically interconnected using a star or extended star topology. Star and extended star topologies are easy to install, very scalable and easy to troubleshoot. Early Ethernet and Legacy Token Ring technologies topologies: provide two additional Bus – All end systems chained together and terminated on each end. Ring – Each end system is connected to its respective neighbors to form a ring. According to Network Topology (Cont.): According to topology computer networks can be (Types of network Topologies):  Bus.  Star.  Ring.  Mesh.  Hybrid. Bus Topology  All devices are connected to a central cable, called the bus or backbone. Bus Topology (cont.) Frame Transmission - Bus LAN Bus Topology (cont.) Advantages & Disadvantages ❑Advantages: ✓Simple, easy to use and construct ✓Requires least amount of cable (less expensive) ❑Disadvantages: ✓A faulty cable will take the entire LAN down ✓Difficult to troubleshoot ✓Heavy network traffic can slow bus considerably Star Topology [used today]  A physical Star topology connects the devices via a centralized unit such as a Hub or Switch.  Nodes communicate across the network by passing data through the central device. Star Topology (cont.) Star Types  Broadcasted Star Topology (Hubbed Star)  Switched Star Topology (Switched Star) Star Topology (cont.) Advantages Single computer failure doesn’t bring down whole network. Adding new devices to a Star network is very simple compared to any of the other topologies. No disruptions to the network when connecting or removing devices. Centralized control. Centralized network/hub monitoring. Easy to troubleshoot. Star Topology (cont.) Disadvantages If central device fails, the whole network fails. Compared to the bus topology, a star network generally requires more cable. More expensive than linear bus topologies because of the cost of the central device. Ring Topology All devices are connected to one the shape of a closed loop, so device is connected directly to devices, one on either side of it. ◼ Data is passed one way from device. ◼ another in that each two other device to Ring Topology (cont.). Advantages and Disadvantages  Advantages  Equal access for all users.  Perform well under heavy traffic  Disadvantages  If one device/cable fails then the whole network goes down.  Difficult to troubleshoot  Adding/Removing computers disrupts the whole network Mesh Topology  In a mesh topology each device/PC is connected to every other device/PC in the network by its own cable.  Mesh Types:  Full Mesh.  Partial Mesh. Mesh Topology (cont.) Advantages and Disadvantages Advantages  Mesh topology boasts the highest fault tolerance of all of the network topologies Disadvantages  Because each connection needs its own cable a Mesh topology can get very expensive. According to data Interchange Method Circuit Switch  A circuit-switched network establishes a dedicated circuit (or channel) between endpoints before the users can communicate.  Three phases  Circuit establishment  Data transfer  Circuit disconnect  All communication uses the same path.  Examples of circuit-switched communication links are analog dialup (PSTN) Circuit Switching  Circuit-switch communication Circuit Switching – Properties(1) Inefficient  Channel capacity dedicated for duration of connection  If no data, capacity wasted Set up (connection) takes time. Once connected, transfer is transparent. Developed for voice traffic (phone). Packet-Switching – Basics Data transmitted in small packets  Longer messages split into series of packets Packets are received, stored briefly (buffered) and passed on to the next node. Packet-Switching – Advantages(1) Line efficiency  Single node to node link can be shared by many packets over time  Packets queued and transmitted as fast as possible Data rate conversion  Each station connects to the local node at its own speed  Nodes buffer data if required to equalize rates NETWORK TRANSMISSION MEDIA NETWORK TRANSMISSION MEDIA Network Transmission Media Communication across a network is carried through a medium which allows a message to travel from source to destination. Media Types Description Metal wires within cables Uses electrical impulses Glass or plastic fibers within cables (fiber-optic cable) Uses pulses of light. Wireless transmission Uses modulation of specific frequencies of electromagnetic waves. Network Transmission Media  To transmit data, a medium must exist.  The medium can be in the form of cables or wireless medium.  Most common used media for data networks  Twisted pair cable  Coaxial cable  Fiber optic cable  Wireless media Network Transmission Media  Cable Media  Twisted Pair Cables  STP  UTP  Coaxial Cables.  Fiber Optic Cables  Wireless Media  Infrared  Microwave  Bluetooth Network Transmission Media Cable Media  There are several types of cable which are commonly used with LANs.  In some cases, a network will utilize only one type of cable, other networks will use a variety of cable types.  The type of cable chosen for a network is related to the network's topology, protocol, and size. Twisted pair cable [used today] Most widely used (Ethernet networks) The segment can’t exceed 100 meters Two basic types  STP(Shielded Twisted Pair)  UTP (Unshielded Twisted Pair): Twisted pair cable has 7 categories Use RJ-45 connectors Crimper tool attach the twisted pair cable to RJ- 45 Unshielded Twisted Pair (UTP) Low Cost Easy Installation Bandwidth ~ 1,4,10,16,100,1000 Mbps Attenuation ~ hundred of meters (high) UTP Categories  The principle upon which the UTP cables are classified is the amount of twisting, when the twisting amount is increased, the interference amount is decreased,. as a final result, the bandwidth the cable support increases. UTP Categories (a) Category 3 UTP. (b) Category 5 UTP. UTP Categories RJ-45 Connector Poorly terminated UTP cable Properly terminated UTP cable RJ-45 Socket Shielded Twisted Pair (STP) Moderate Cost. Fairly Easy Installation. Bandwidth ~ more than same cat of UTP. Attenuation ~ hundred of meters. Connector Used RJ-45 123 ……… 8 Twisted Pair Cable Connection Types Dropped Cable (Patch Chord / Straight). Cross-over Cable. Rolled-over Cable. Dropped (Patch Chord / Straight) Cable 1 2 1 2 3 6 3 6 Cross-over Cable 1 2 3 6 3 6 1 2 Coaxial [not used] Cost is Moderate Fairly Easy Installation Bandwidth ~ 10 Mbps Attenuation ~ few hundreds of meters Fiber-optic Highest Cost. Difficult Installation. Bandwidth ~ 2 Gbps. Attenuation ~ ten of kilometers (low). Wireless Media  Flexible (Used in areas where it is hard to install cables )  Used in wireless LANs  Hybrid environment is one which wireless components communicate with a network that use cables THANKS! Best Regards!