People use “network” when they describe a group or organization. Among computers, network is described as connection between PC to PC to share(send/receive) data.

Like we use common language to communicate each other efficiently, for PCs, they also needs basic principles and rules to transport data efficiently.

Protocol, is a tool which defines basic rules and promises for data transmission. Sometime network admin needs to set some of rules for protocol.

When PC sends data to another PC, it packs information with data because data itself doesn’t have extra information like destination address or source address. This process is called Encapsulation. At first, data is created as a PDU(Protocol Data Unit) and during transmission process, it gets bigger with encapsulation.

To transfer voice data to another PC, at first, you uses G.711 codec to compress voice data. When it transfers, the compressed voice data attached with 12 Bytes of header when it uses RTP(Real Time Transport Protocol).  Each time, when the data goes through different layers, it adds up different header because a parameter value is different for each layer.


Network Types

There’s two types of network depends on network size and transmission devices. LAN(Local Area Network) and WAN(Wide Area Network)

LAN(Local Area Network) means local network including a user. So it’s isolated network with other network group. To create LAN environment we use Hub, Switch and UTP cable. The basic protocol for LAN is “Ethernet”  which uses MAC address to assign location and set destination.

WAN(Wide Area Network) is included each of isolated LAN group, which is more wide. If A company’s headquarter is located in VA  and others in GA, then it would be impossible to connected each others’ switch devices locally/ physically, so it uses ISP(Internet Service Provider) to connect. They use Router and IP address to assign location and forward it.