Internet layers

Internet layers

1. OSI model: Open System Interconnection model. This model has 7 layers-vertical stack of 7 layers.

   • Upper layer: software that provides network services-like encryption and connection management.
   • Lower layer: hardware orientated functions: routing, addressing and flow control.
   • 1. Application: SMTP, FTP, Telnet, HTTP
   • 2. Presentation: format data(ascii) and encryption
   • 3. Session: start and stop session
   • 4. Transport: TCP, port numbers
   • 5. Network: IP addresses, routers
   • 6. Data link: mac addresses and switches
   • 7. Physical: cables, network, ethernet

2. TCP/IP model: transmission control protocol/internet protocol. This model has 4 layers: application, transport, internet and link

   • Application: includes high level protocols- FTP, HTTP, SMTP, DNS
   • Transport: ensures reliable arrival of messages and provides error checking mechanisms and data flow controls
   • Internet: packs data into data packets (datagrams). Each packets contains a source and destination address-IP address. Uses several protocols for routing and delivering packets.
   • Link: defines how datagrams (like packets) can be passed in a network.