TCP/IP Networking basics

Topology
Layers (TCP/IP stack)

Topology

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 (255.0.0.0)
  
  private network: 10.x.x.x/8
- Class B
  
  N = 16: [129-191].x.x.x/16 (255.255.0.0)
  
  private network: 172.16.x.x/12
- Class C
  
  N = 24: [192-223].x.x.x/24 (255.255.255.0)
  
  private network: 192.168.x.x/16
- Class D
  
  [224-239].x.x.x
  
  Class D is reserved for multicast.
- Loopback
  
  127.0.0.1/32
- Link local addresses
  
  169.254.x.x/16
  
  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.