At which layer of ISO/OSI does the fiber optics work?

A.
Network layer

B.
Transport layer

C.
Data link layer

D.
Physical layer

Explanation:
The physical layer consists of the basic networking hardware transmission technologies, such as fiber optics, of
a network.
Incorrect Answers:
A: The network layer is responsible for packet forwarding including routing through intermediate routers.
B: The transport layer provide host-to-host communication services for applications. It provides services such
as connection-oriented data stream support, reliability, flow control, and multiplexing.
C: The data link layer is responsible for media access control, flow control and error checking.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, New York, 2013, p. 530