Lecture-6: Computer Networks and Internet PDF

Lecture-6 Computer Networks and Internet Networks Affect Our Lives Networking Today No Boundaries World without boundaries Global communities Human network Network Components Host Roles Every computer on a network is called a host or end device. Each host can be either client or se...

Lecture-6 Computer Networks and Internet Networks Affect Our Lives Networking Today No Boundaries World without boundaries Global communities Human network Network Components Host Roles Every computer on a network is called a host or end device. Each host can be either client or server. Servers are computers that provide Server Description information to end devices: Type email servers Email server runs email server software. Email web servers Clients use client software to access email. file server Web Web server runs web server software. Clients use browser software to access web pages. Clients are computers that send requests File File server stores corporate and user files. to the servers to retrieve information: The client devices access these files. web page from a web server email from an email server Network Components Peer-to-Peer It is possible to have a device be a client and a server in a Peer-to-Peer Network. This type of network design is only recommended for very small networks. Advantages Disadvantages Easy to set up No centralized administration Less complex Not as secure Lower cost Not scalable Used for simple tasks: transferring Slower performance files and sharing printers Network Components 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 Network Components Intermediary Network Devices 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. Maintain information about what pathways exist in the network. Notify other devices of errors and communication failures. Network Components Network 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 Uses pulses of light. (fiber-optic cable) Wireless transmission Uses modulation of specific frequencies of electromagnetic waves. Network Representations and Topologies Network diagrams, often called topology diagrams, use symbols to represent devices within the network. Important terms to know include: Network Interface Card (NIC) Physical Port Interface Note: Often, the terms port and interface are used interchangeably Network Representations and Topologies Topology Diagrams Physical topology diagrams illustrate the Logical topology diagrams illustrate devices, physical location of intermediary devices and ports, and the addressing scheme of the cable installation. network. Common Types of Networks Networks of Many Sizes Small Home Networks – connect a few computers to each other and the Internet Small Office/Home Office – enables computer within a home or remote office to connect to a corporate network Small Home SOHO Medium to Large Networks – many locations with hundreds or thousands of interconnected computers World Wide Networks – connects hundreds of millions of computers world-wide – such as the internet Medium/Large World Wide Common Types of Networks LANs and WANs A LAN is a network infrastructure that A WAN is a network infrastructure that spans a small geographical area. 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. The following groups were developed to help maintain structure on the internet: IETF ICANN IAB The Internet Intranets and Extranets An intranet is a private collection of LANs and WANs internal to an organization that is meant to be accessible only to the organizations members or others with authorization. An organization might use an extranet to provide secure access to their network for individuals who work for a different organization that need access to their data on their network. Internet Connections There are many ways to connect users and organizations to the internet: Popular services for home users and small offices include broadband cable, broadband digital subscriber line (DSL), wireless WANs, and mobile services. Organizations need faster connections to support IP phones, video conferencing and data center storage. Business-class interconnections are usually provided by service providers (SP) and may include: business DSL, leased lines, and Metro Ethernet. Internet Connections Home and Small Office Internet Connections Connection Description Cable high bandwidth, always on, internet offered by cable television service providers. DSL high bandwidth, always on, internet connection that runs over a telephone line. Cellular uses a cell phone network to connect to the internet. Satellite major benefit to rural areas without Internet Service Providers. Dial-up an inexpensive, low bandwidth option using a telephone modem. Internet Connections Businesses Internet Connections Corporate business connections may require: higher bandwidth Type of Description dedicated connections Connection managed services Dedicated Leased These are reserved circuits within the service Line provider’s network that connect distant offices with private voice and/or data networking. Ethernet WAN This extends LAN access technology into the WAN. DSL Business DSL is available in various formats including Symmetric Digital Subscriber Lines (SDSL). Satellite This can provide a connection when a wired solution is not available. Reliable Networks Network Architecture Network Architecture refers to the technologies that support the infrastructure that moves data across the network. There are four basic characteristics that the underlying architectures need to address to meet user expectations: Fault Tolerance Scalability Quality of Service (QoS) Security Reliable Networks Fault Tolerance Scalability Network Trends The role of the network must adjust and continually transform in order to be able to keep up with new technologies and end user devices as they constantly come to the market. Several new networking trends that effect organizations and consumers: Bring Your Own Device (BYOD) Online collaboration Video communications Cloud computing Network Trends Bring Your Own Device Bring Your Own Device (BYOD) allows users to use their own devices giving them more opportunities and greater flexibility. BYOD allows end users to have the freedom to use personal tools to access information and communicate using their: Laptops Netbooks Tablets Smartphones E-readers BYOD means any device, with any ownership, used anywhere. THANKS