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Samenvatting J1 S2 Computer Networks 1
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Samenvatting van het vak 'Computer Networks' in het eerste jaar
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H1: Networking today Communication is almost as important to us as air, water or food. Trough networks, we are
connected like never before
Network components
Host roles/Client-server
o Host/end device: every computer on a network
o Servers: computers that provide information to end devices
o Clients: computers that send requests to the servers to retrieve info
Peer-to-peer: possible to have a device be a client and a server
o Easy to set up no centralized administration
o Less complex not as secure
o Lower cost not scalable
o Used for simple tasks slower performance
End devices: end device is where a message originates from or where it is received
Intermediary Network device: interconnects end devices like switches and routers and
manages data as it flows through a network
Network media: communication across a network is carried through a medium which allows
a message to travel from source to destination
o Metal wires in cables: electrical impulses
o Glass or plastic fibers in cables: pulses of light
o Wireless transmition: modulation of specific frequencies of electromagnetic waves
Network representations and topologies
Network representations: network/topology diagrams use symbols to represent devices
o Network Interface Card (NIC)
o Physical port (on switches)
o Interface (on routers)
Physical topology diagrams: illustrate physical location of devices and cables
Logical topology diagrams: illustrate devices, ports and the addressing scheme
Common types of networks
Small home networks: connect a few computers to each other and the internet
Small office: enables computer within a home or remote office to connect to a corporate
network
Medium to large networks: many locations with hundreds of interconnected computers
World wide networks: connects millions of computers worldwide
LAN: network infrastructure that spans a small geographical area
o Interconnect end devices in a limited area
o Administered by a single organization or individual
o Provide high-speed bandwidth to internal devices
WAN: network infrastructure that spans a wide geographical area
o Interconnect LANs over wide geographical areas
o Typically administered by one or more service providers
o Typically provide slower speed links between LANs
, Internet: worldwide collection of interconnected LANs and WANs
Intranet: private collection of LANs and WANs internal to an organization that is meant to be
accessible to the organizations members or others with authorization
Extranet: provides secure access to an organization’s network for individuals who work for a
different organization that need access to their data on their network
Internet connections
Internet access technologies
o Popular services for home users and small offices include broadband cable,
broadband digital subscriber line, wireless WANs and mobile services
o Organizations need faster connections to support IP phones, video conferencing and
data center storages
o Business-class interconnections are usually provided by service providers
Home and small office internet connections:
o Cable: high bandwidth, always on, internet offered by cable service providers
o DSL: high bandwidth, always on, internet connection that runs over a telephone line
o Cellular: uses a cell phone network to connect to the internet
o Satellite: major benefit to rural areas without internet service providers
o Dial-up telephone: an inexpensive, low bandwidth option using a modem
Business internet connections:
o Dedicated leased line: reversed circuits within the provider’s network that connect
distant offices with private voice and/or data networking
o Ethernet WAN: extends LAN access technology into the WAN
o DSL: available in various formats including Symmetric Digital Subsriber Lines
o Satellite: can provide a connection when a wired solution is not available
The converging network: before converged networks organizations would have separately
cabled telephone, video and data and would use different technologies with different sets of
rules and standars
Converged networks: can deliver data, voice and video over the same network infrastructure
Reliable networks
Network architecture: technologies that support infrastructure that moves data across the
nerwork
Four basic characteristics that the architectures need to address to meet user expectations:
o Fault tolerance: limits the impact of a failure, provide redundancy by implementing a
packet switched network (not possible with circuit-switched networks)
o Scalability: a scalable network can expand quickly and easily to support new users
and applications without impacting the performance of service of existing users
o Quality of service: primary-mechanism used to ensure reliable delivery of content
o Network security: network infrastructure security and information security
Confidentiality: only intended recipients can read the data
Integrity: assurance that the data has not be altered with
Availibility: assurance of timely and reliable access to data
Network trends
Bring your own device: allows end users to have the freedom to use personal tools
Online collaboration: collaborate and work with others over the network on projects
, Video communication: easy and powerful tool for communication
Cloud computing: allows us to store personal files or backup our data on servers over the
internet
o Public clouds: available to the general public through a pay-per-use model of free
o Private clouds: intended for a specific organization or entity such as the government
o Hybrid clouds: made up of two or more cloud types
o Custom clouds: built to meet the needs of a specific industry
Technology trends at home: smart home technology = growing trend that allows technology
to be integrated into every-day appliances which allows them to interconnect with other
devices
Powerline networking: can allow devices to connect to a LAN where data network cables or
wireless communications are not a viable option
Wireless broadband: option to connect homes to the internet
Network security
Security is an integral part of networking regardless of the size of the network. It involves
many protocols, technologies, devices, tools and techniques
Security solutions: security must be implemented in multiple layers using more than one
security solution
The IT professional
Cisco Certified Network Associate (CCNA)
Networking jobs
, H2: Basic switch and end
device configuration
Cisco IOS access
Shell: user interface that allows users to request specific tasks from the computer
Kernel: communicates between hardware and software of a computer
Hardware: physical part of a computer including underlying electronics
GUI: graphical user interface
o Allows user to interact with the system using an environment of graphical icons,
menus and windows
o More user-friendly and requires less knowledge
o Can crash easily so network devices mainly use CLI
Access methods
o Console: physical management port used to access a device in order to provide
maintenance such as performing the initial configurations
o Secure shell: establishes a secure remote CLI connection to a device over a network
Terminal emulation programs: used to connect to a network device by a console port or SSH
connection
IOS navigation
Primary command modes
o User EXEC mode: allows access to only a limited number of basic monitoring
commands (CLI: >)
o Privileged EXEC mode: allows access to all commands (CLI: #)
Configuration mode and subconfiguration modes
o Global configuration mode: used to access configuration options on the device (CLI:
(config)#)
o Line configuration mode: used to configure console and SSH
o Interface configuration mode: used to configure a switch port or router interface
Navigation between IOS modes
o enable: to move from user EXEC mode to privilege EXEC mode
o configure terminal: move in and out of global configuration mode
o exit: return to privilege EXEC mode
o line: move in and out of line configuration mode
o exit: return to global configuration mode
o exit: move out of any subconfiguration mode to get back to global configuration
mode
o end or Ctrl+Z: return to privilege EXEC mode
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