Page 173 - Computer_Science_F5

Computer Science data stream. This layer provides end-to- handshake, where synchronization and
end data transport services, establishing connection parameters are exchanged.
a logical connection between the sending
(b) Sequencing: The service ensures
and receiving hosts across an Internet.
that data is transmitted and received in a
Additionally, the Transport layer
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manages the multiplexing of upper-
that data is delivered to the recipient
layer applications, session establishment, specific order. This sequencing guarantees
exactly as it was sent.
and the termination of virtual circuits.
By offering transparent data transfer, it (c) Acknowledgments: The service
conceals network-dependent details from utilises acknowledgments to confirm the
the higher layers. The Transport layer successful receipt of data segments. These
can operate in a connectionless-mode acknowledgments provide feedback to
using User Datagram Protocol (UDP) the sender, ensuring reliable data transfer.
or in a connection-oriented mode using (d) Flow control: Connection-oriented
Transmission Control Protocol (TCP). services implement flow control
mechanisms to regulate the rate of data
Connection-oriented transport transmission. This helps to prevent
The connection-oriented transport service overwhelming the receiving entity and
guarantees that data is delivered without avoids congestion.
errors, in the correct order, and without
any losses or duplications. The Transport Flow control
layer also focuses on optimising the use Flow control is essential for managing the
of network services and delivering the rate at which data is transmitted between
requested quality of service to session a sender and a receiver, ensuring that
entities. For instance, a session entity the receiver can handle the incoming
might specify acceptable error rates, data without becoming overwhelmed.
maximum delay, priority, and security At the Transport layer, data integrity is
levels. Consequently, the transport layer maintained through the management of
must adapt to meet these requirements flow control and the provision of reliable
while maintaining efficient data data transport between systems. Flow

transmission. control prevents the sending host from
overwhelming the receiving host’s buffers,
A service is classified as connection- which can result in data loss. Reliable
oriented when it exhibits certain data transport involves establishing a
characteristics. These characteristics connection-oriented communication
include: session, ensuring the following:
(a) Virtual circuit setup: The service 1. Received segments are acknowledged
establishes a virtual circuit between back to the sender.
the communicating entities. This setup 2. Unacknowledged segments are
often involves a process like a three-way retransmitted.

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for Advanced Secondary Schools

Computer Science Form 5.indd 164 23/07/2024 12:33