Page 142 - Computer_Science_F5

(a) Data encapsulation process Link layer, the encapsulated data is
At the transport layer, data is divided termed as frames.
into smaller pieces. Each piece receives Chapter Three: Advanced Computer Networks
a header containing information such (b) Data de-encapsulation process
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as the source port, destination port, The Physical layer receives the bits,
sequence number, and other relevant de-encapsulates them into frames, and
details. This process transforms the forwards them to the upper layer. At the
original data into a new format. Data Link layer, frames are received and
checked for MAC address matches and
The encapsulated data at the transport errors. If everything is correct, the layer
layer is known as segments or 2 header and trailers are removed, and
datagrams. When TCP is utilised, this the data is de-encapsulated before being

encapsulated data is specifically referred sent to the upper layer.
to as segments. When UDP is used
for transmission, this is referred to as The Network layer receives the packet
Datagrams. from the Data Link layer, verifies IP
addresses, removes the layer 3 header,
The data then moves to the network and delivers the de-encapsulated data
layer, where additional information such packet to the Transport layer.
as the source IP address and destination
IP address is added from the layer 3 Finally, the Transport layer removes the

header. This combination of data and layer 4 header before passing the data
additional information is referred to as segments/datagrams to the upper layers
packets. (Session, Presentation, and Application)
for delivery to the recipient.
When the packets reach the Data Link
layer, additional information, known as This process illustrates the steps
a trailer is added. This trailer includes involved in data encapsulation and

details like MAC address and destination de-encapsulation. Figure 3.7 shows
MAC address, and it is also utilised for encapsulation and decapsulation in OSI
error-checking purposes. At the Data model.

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Student’s Book Form Five

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