What is Internet

Internet is a network of interconnected devices network of networks

• Communication links
  • fiber, copper, radio, satellite
  • transmission rate: bandwidth
• packet switches: forwards packets (chunks of data)
  • routers and switches
• protocols control sending, receiving of messages
  • TCP, IP, HTTP
• Internet standards for interoperability
  • RFC: request for comments
  • IETF: Internet Engineering Task Force

Circuit Switching

end-end resources allocated to reserved for 'call' between source and destination

• While the two is having communication
• others cannot use the resources

Packet Switching

break down the information that you want to send into smaller chunks and send over the network through different routes in the network

• When a route is congested, the packet can go through another route
• packets may arrive out of order
• handle by transport layer

Protocols

A protocol defines the rules for communication between computers

• protocol are broadly classified as connectionless and connection oriented
  More is explained in the 4. Network Layer

Connectionless protocol

Send data out as soon as there is enough data to be transmitted
base on the receiving end to rearrange the data into the original data

• use datagram protocol (UDP)

Connection-oriented protocol

Provides a reliable connection stream between two nodes
Consists of setup, transmission and tear down phases
Creates virtual circuit-switched network

• transmission control protocol (TCP)

examine the sequence number of the packet to know the sequence, allows the receiver to know how to arrange them and ask the server for those packets that has yet to transmitted

Encapsulation

• A packet typically consist if
  • control information of address of packet
    • header and footer
  • data: payload
    Delivery service only assess the header and footer while the receiving end process the payload

#toupdate

• Wrapping of packets is possible
  • A packet of p1 of N1 is encapsulated into a packet p2 of N2

Network Layers

Network models typically use a stack of layer

• Higher layers uses the services of lower layers via encapsulation
• A layer can be implemented in hardware or software
• bottom most layer must be hardware
  A network device may implement several layers
  A communication channel between two nodes is established for each layer
• Actual channel at bottom layer
• Virtual channel at higher layers

Intermediate Layers

Layers between Application and Physical layer

• Link layer
  • sending information in the local area network
  • Ethernet, WiFi
  • Media Access Control (MAC) address
  • packets called frames
• Network layer
  • Internet wide communication
  • send the packet as long as they have the bandwidth
  • uses address table
  • 32-bit IPv4 and 128-bit IPv6
• Transport layer
  • 16-bit addresses(ports) for classes of application
  • Connection-oriented (TCP)
  • Connectionless UDP

Internet Packet Encapsulation

OSI Model

Open System Interconnect is a network model consisting of sever layers

• Application
• presentation
• session
• transport
• network
• data link
• physical