Which of the following correctly describe steps in the OSI data encapsulation process?

A. The presentation layer translates bits into voltages for transmission across the physical
link.
B. The transport layer divides a data stream into segments and adds reliability and flow
control information.
C. Packets are created when the network layer adds Layer 3 addresses and control
information to a segment.
D. The data link layer adds physical source and destination addresses and an FCS to the
segment.
E. Packets are created when the network layer encapsulates a frame with source and
destination host addresses and protocol-related control information.

Answer: B, C

Explanation:

The Transport Layer:

You can think of the transport layer of the OSI model as a boundary between the upper
and lower protocols. The transport layer provides a data transport service that shields the
upper layers from transport implementation issues such as the reliability of a connection.

The transport layer provides mechanisms for:

• Segmenting upper layer applications
• The establishment, maintenance, and orderly termination of virtual circuits
• Information flow control and reliability via TCP
• Transport fault detection and recovery.

The Network Layer:

Layer three of the OSI model is the network layer.

1. The network layer creates and sends packs from source network to destination network.
2. It provides consistent end-to-end packet delivery services and control information.
3. It creates and uses layer3 addresses for use in path determination and to forward packets.