net tech

Routing Fundamentals

Data Encapsulation

Encapsulation is a process

wherein a new string of

information is added to an

existing unit to form a new unit of

information. A new datagram is

formed by adding headers and

trailers to a data payload

Decapsulation is the reverse

process of encapsulation wherein

the header and tail of a packet are

removed to obtain the data

payload.

Concept of Network Communication

Virtual information transfer is similar to real object transfer.

Data payload can be considered as the information to be transmitted. In a hierarchical communication process, the

data unit (packet) transmitted from the upper layer to the lower layer can be called the data payload of the lower layer.

• Packet is a data unit that is exchanged and transmitted on a

network. It is in the format of header+data payload+tail. During

transmission, the format and content of packets may change.

• Header is the information segment added before the data payload

during packet assembly to facilitate information transmission.

• Tail is the information segment added after the payload to

facilitate information transmission.

TCP Protocol Data Units

A Protocol Data Unit (PDU) is a specific block of information transferred over a network. It is often used in reference to

the OSI model, since it describes the different types of data that are transferred from each layer.

• Physical layer – raw bits (1s or 0s) transmitted physically via the hardware

• Data Link layer – a frame (or series of bits)

• Network layer – a packet that contains the source and destination address

• Transport layer – a segment that includes a TCP header and data

• Session layer – the data passed to the network connection

• Presentation layer – the data formatted for presentation

• Application layer – the data received or transmitted by a software application