Page 817 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

extend the maximum length of a specific cable type by deploying one

or more repeaters along a lengthy cable run. Repeaters, concentrators,
and amplifiers operate at OSI layer 1. Systems on either side of a
repeater, concentrator, or amplifier are part of the same collision
domain and broadcast domain.

Hubs Hubs were used to connect multiple systems and connect
network segments that use the same protocol. A hub is a multiport
repeater. Hubs operate at OSI layer 1. Systems on either side of a hub

are part of the same collision and broadcast domains. This ensures
that the traffic will reach its intended host, but at the cost that all
members of the same collision domain and broadcast domain will
receive the communication as well. Most organizations have a no-hub
security policy to limit or reduce the risk of sniffing attacks since they
are an outmoded technology and switches are preferred.

Modems A traditional landline modem (modulator-demodulator) is a

communications device that covers or modulates between an analog
carrier signal and digital information in order to support computer
communications of public switched telephone network (PSTN) lines.
From about 1960 until the mid-1990s, modems were a common
means of WAN communications. Modems have generally been
replaced by digital broadband technologies including ISDN, cable
modems, DSL modems, 802.11 wireless, and various forms of wireless

modems.

The term modem is used incorrectly on any device that

does not actually perform modulation. Most modern devices
labeled as modems (cable, DSL, ISDN, wireless, etc.) are routers,
not modems.

Bridges A bridge is used to connect two networks together—even
networks of different topologies, cabling types, and speeds—in order
to connect network segments that use the same protocol. A bridge
forwards traffic from one network to another. Bridges that connect
networks using different transmission speeds may have a buffer to

store packets until they can be forwarded to the slower network. This