Here are the different networks which are generally used for networking through linux machine;

* IPv4:  Internet Protocol version 4 (IPv4) is widely used by most of the Internet servers and personal computers. This uses 32 bits to assign a network address as defined by the four octets of an IP address up to 255.255.255.255. Which is the representation of four 8 bit numbers thus totaling 32 bits.

* IPv6: Internet Protocol version 6 (IPv6) uses a 128 bit address and thus billions of potential addresses. The protocol regularly upgraded to include new quality of service features and security. Linux supports both IPv6 but IPv4.

* TCP/IP: (Transmission Control Protocol/Internet Protocol) uses a client – server model for communications. The protocol defines the data packets transmitted, re-transmission. data integrity verification (error detection bytes), connection and acknowledgement protocol.

* TCP/IP time to live (TTL): This is a counting system to determine how long a packet is valid before it reaches its destination. Each time a TCP/IP packet passes through a router it will decrease its TTL count. After the count reaches zero the packet is dropped by the router. This ensures that delinquent routing and looping aimless packets will not flood the network.

* MAC Address: (media access control) is the network card address used for communication between other network devices on the subnet. This info is not routable. The ARP table maps TCP/IP address (global internet) to the local hardware on the local network. Use the command /sbin/ifconfig to view both the IP address and the MAC address. The MAC address distinctively recognizes each node of a network and is used by the Ethernet protocol.

* OSI 7 Layer Model: The ISO (International Standards Organization) has defined the OSI (Open Systems Interconnection) model for current networking protocols.

* Full Duplex:  Full Duplex allow sending and receiving of packets instantaneously. Most modern modems support full duplex.

* Half Duplex: Allows the sending and receiving of packets in one direction at a time only.