Data Encapsulation
Written on 04:06 by Ahmet Emir
When a host transmits abstracts beyond a arrangement to addition device, the abstracts goes through encapsulation:
It is captivated with agreement advice at anniversary band of the OSI model. Anniversary layer
communicates alone with its associate band on the accepting device.
To acquaint and barter information, anniversary band uses Agreement Abstracts Units (PDUs).
These authority the ascendancy advice absorbed to the abstracts at anniversary band of the model. They are usually
attached to the attack in advanced of the abstracts acreage but can additionally be in the trailer, or end, of it.
Each PDU attaches to the abstracts by encapsulating it at anniversary band of the OSI model, and each
has a specific name depending on the advice provided in anniversary header. This PDU information
is apprehend alone by the associate band on the accepting device. After it’s read, it’s bare off
and the abstracts is again handed to the abutting band up.
Figure 1.28 shows the PDUs and how they attach ascendancy advice to anniversary layer. This
figure demonstrates how the upper-layer user abstracts is adapted for manual on the network.
The abstracts beck is again handed bottomward to the Transport layer, which sets up a basic circuit
to the accepting accessory by sending over a synch packet. Next, the abstracts beck is burst up
into abate pieces, and a Transport band attack (a PDU) is created and absorbed to the header
of the abstracts field; now the allotment of abstracts is alleged a segment. Anniversary articulation is sequenced so the
data beck can be put aback calm on the accepting ancillary absolutely as it was transmitted.
Each articulation is again handed to the Arrangement band for arrangement acclamation and routing
through the internetwork. Logical acclamation (for example, IP) is acclimated to get anniversary articulation to the
correct network. The Arrangement band agreement adds a ascendancy attack to the articulation handed
down from the Transport layer, and what we accept now is alleged a packet or datagram. Remember
that the Transport and Arrangement layers assignment calm to clean a abstracts beck on a receiving
host, but it’s not allotment of their assignment to abode their PDUs on a bounded arrangement segment—which is
the alone way to get the advice to a router or host.
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