COMMUNICATION

1
CHAPTER 12

• COMMUNICATION
• CONTROL

2
COMMUNICATION SUBSYSTEM EXPOSURE

• Transmission impairments
• Component Failure
• Subversive Threats

3
Subversive threats to the Communication Subsystem
Release of message contents
Passive Attacks
Traffic analysis
Message insertion Message deletion Message
modification Changed message order Message
duplication Denial of message services Spurious
associations
Subversive Threats
Active attacks
4
PHYSICAL COMPONENT CONTROLS

• Tramsmision Media

Twisted paier Coaxial cable Optical fiber
Bounded
Transimission media
Terrestrial microware Satellite microwave Radio
frequency Infrared
Unbounded
5

• Communication Lines
• Modems
• Port-Protection Devices
• Multiplexors and Concentrators

6
LINE ERROR CONTROLS

• Error Detection

Sends message
Receiver
Sender
Returns copy of message
7
Error Correction

• Forward error correcting codes
• Retransmission of data in error(backward error
  correction)

8
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.

9
TOPOLOGICAL CONTROLS

• Local Area Network Topologies
• Bus Topology
• Tree Topology
• Ring Topology
• Star topology
• Hybrid Topologies
• Wide Area Network Topologies

10
CHANNEL ACCESS CONTROLS

• Polling Methods
• Contention Methods

11
CONTROLS OVER SUBVERSIVE THREATS

• Link Encryption
• End-to-End- Encryption
• Stream Ciphers
• Error Propagation Codes
• Message authentication Codes
• Message Sequence Numbers
• Request-Response Mechanisms

12
INTERNETWORKING CONTROLS

• Three types of devices are used to connect
  subnetworks in an internet
• Bridge
• Router
• Gateway

13
COMMUNICATION ARCHITECTURES AND CONTROLS

• The architecture has seven layers of
  function.each of which has as sociated controls
• Physical - Session
• Data link - Presentration
• Network - Appication
• Transport

14
AUDIT TRAIL CONTROLS

• Accounting Audit Trail
• Operations Audit Trail

15
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-and-forward operations must be carried out
  in the network.