Page 744 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

remember. One of our favorites is Please Do Not Teach Surly People
Acronyms. Do take note that this memorization mnemonic works from

the Physical layer up to the Application layer. A mnemonic working
from the Application layer down is All Presidents Since Truman Never
Did Pot. There are many other OSI memorization schemes out there;
just be sure you know whether they are top-down or bottom-up.

Physical Layer

The Physical layer (layer 1) accepts the frame from the Data Link
layer and converts the frame into bits for transmission over the

physical connection medium. The Physical layer is also responsible for
receiving bits from the physical connection medium and converting
them into a frame to be used by the Data Link layer.

The Physical layer contains the device drivers that tell the protocol
how to employ the hardware for the transmission and reception of
bits. Located within the Physical layer are electrical specifications,
protocols, and interface standards such as the following:

EIA/TIA-232 and EIA/TIA-449

X.21

High-Speed Serial Interface (HSSI)

Synchronous Optical Networking (SONET)

V.24 and V.35

Through the device drivers and these standards, the Physical layer
controls throughput rates, handles synchronization, manages line
noise and medium access, and determines whether to use digital or
analog signals or light pulses to transmit or receive data over the
physical hardware interface.

Network hardware devices that function at layer 1, the Physical layer,
are network interface cards (NICs), hubs, repeaters, concentrators,
and amplifiers. These devices perform hardware-based signal
operations, such as sending a signal from one connection port out on
all other ports (a hub) or amplifying the signal to support greater
transmission distances (a repeater).