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)

This layer is used to transport data between nodes in a network.

Transport (OSI 4)

This layer is responsible for communication between processes, and utilizes different ports for different services.

At this layer information get segmented for transmission.

Application (OSI 7/6/5)

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

The application layer is responsible for transmitting user data between applications.

Transport layer protocols


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.


It's a protocol used to diagnose network issues.


Encapsulates data into packets and trasmits them to the remoce end of the connection; it can check for errors and resend packets if needed.

TCP packets are reassembled into one logical piece of information to be sent to the application layer.


Its an unreliable, connection-less protocol: data are sent to the remote end without any prior connection established, and without checking (and thus resending) lost packets.

It's faster than TCP and employed where low latency is a must and data integrity is not a requirement.

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