TCP/IP Networking basics


A number of hosts connected to a central switch, and connected to other networks through a gateway (router).

Layers (TCP/IP stack)

Link (OSI 2/1)

The link layer handles the actual transmission of data, relying on dedicated hardware (a networking interface) identified by a unique 48 digits MAC address.

Internet (OSI 3)

IP protocol

Identifies hosts and defines routing paths.

  • IPv4 address

    An IPv4 address is a 32 bits number.

    In an IP addresses, the first N bits represent the the network the address belongs to, while the remaining n bits identify the host.

  • Network classes

    Network addresses are grouped in classes. Each class a network address designed for private use.

    • Class A

      N = 8: [1-127].x.x.x/8 (

      private network: 10.x.x.x/8

    • Class B

      N = 16: [129-191].x.x.x/16 (

      private network: 172.16.x.x/12

    • Class C

      N = 24: [192-223].x.x.x/24 (

      private network: 192.168.x.x/16

    • Class D


      Class D is reserved for multicast.

    • Loopback

    • Link local addresses


      It is assigned when dynamic addresses can't be obtained (via DHCP). It is not routable.

Transport (OSI 4)

At this layer information get segmented for transmission.

Application (OSI 7/6/5)

This layer features application protocols like http, ftp, smtp.

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