CHAPTER 12
COMMUNICATION
CONTROL
COMMUNICATION
SUBSYSTEM EXPOSURE
 Transmission impairments
 Component Failure
 Subversive Threats
Subversive threats to the
Communication Subsystem
Release of message contents
Passive
Attacks
Traffic analysis
Message insertion
Subversive
Threats
Message deletion
Active
attacks
Message modification
Changed message order
Message duplication
Denial of message services
Spurious associations
PHYSICAL COMPONENT
CONTROLS
 Tramsmision Media
Twisted paier
Bounded
Coaxial cable
Optical fiber
Transimission
media
Terrestrial microware
Unbounded
Satellite microwave
Radio frequency
Infrared
 Communication Lines
 Modems
 Port-Protection Devices
 Multiplexors and Concentrators
LINE ERROR CONTROLS
 Error Detection
Sends message

Receiver
Sender
Returns copy of message
Error Correction
 Forward error correcting codes
 Retransmission of data in
error(backward error correction)
FLOW CONTROLS
 The simplest form of flow control is stop-
and-wait flow control
 The stop-and-wait flow control protocol is
inefficient because the communication
channel remains unused for periods of
time while the receiver isprocessing the
frames received.
TOPOLOGICAL CONTROLS
 Local Area Network Topologies
 Bus Topology
 Tree Topology
 Ring Topology
 Star topology
 Hybrid Topologies
 Wide Area Network Topologies
CHANNEL ACCESS
CONTROLS
 Polling Methods
 Contention Methods
CONTROLS OVER
SUBVERSIVE THREATS
 Link Encryption
 End-to-End- Encryption
 Stream Ciphers
 Error Propagation Codes
 Message authentication Codes
 Message Sequence Numbers
 Request-Response Mechanisms
INTERNETWORKING
CONTROLS
 Three types of devices are used to
connect subnetworks in an internet :



Bridge
Router
Gateway
COMMUNICATION ARCHITECTURES
AND CONTROLS
 The architecture has seven layers of
function.each of which has as sociated
controls :




Physical
Data link
Network
Transport
- Session
- Presentration
- App;ication
AUDIT TRAIL CONTROLS
 Accounting Audit Trail
 Operations Audit Trail
EXISTENCE CONTROLS
 Some additional backup and recovery controls
follow :





Where possible, place redundant components and
spare parts throughout the network.
Use equipment with in-built fault diagnosis
capabilities.
Acquire high-quality test equipment.
Ensure adequate maintenance of hardware and
software, especially at remote site
Ensure that adequate logging facilities exist for
recovery purposes, especially where store-andforward operations must be carried out in the
network.