CH4: Transmission Media

Guided – wire

  • Twisted pair
  • Coaxial cable
  • Optical fiber

Unguided – wireless

  • Antenna
  • Isotropic antenna
  • Parabolic reflective antenna
  • Terrestrial microwave
  • Satellite microwave
  • Broadcast radio
  • Infrared
  • Wireless propagation
  • Ground wave propagation
  • Sky wave propagation
  • Line of sight propagation
  • Refraction
  • Optical and Radio Horizons
  • Line of sight transmission
  • Free space loss
  • Multi-path interference


CH2: Protocol Architecture

What is a protocol?

In information technology, a protocol is the special set of rules that end points in a telecommunication connection use when they communicate. Protocols specify interactions between the communicating entities. (more here)

Standardized Protocol Architectures

  • Required for devices to communicate
  • Vendors have more marketable products
  • Customers can insist on standards based
  • Two standards:
    — OSI Reference model
    — TCP/IP protocol suite


  • OSI = Open Systems Interconnection (7 layers)
  • Each layer performs a subset of the required communication functions
  • Each layer relies on the next lower layer to perform more primitive functions
  • Each layer provides services to the next higher layer
  • Changes in one layer should not require changes in other layers
  • Services between two adjacent layers expressed in term of primitives and parameters
  • Primitives specify function to be performed
  • Parameters pass data and control information

More about OSI here


  • TCP = Transmission Control Protocol
  • IP = Internet Protocol
  • TCP PDU: called TCP segment & includes source and destination port
  • protocol suite comprises a large collection of standardized protocols
  • not an official model but a working one
    — Application layer
    — Host-to-host, or transport layer
    — Internet layer
    — Network access layer
    — Physical layer
The standard TCP header comprises 20 bytes, but it can be longer if options are used.


  • UDP = User Datagram Protocol
  • Alternative to TCP
  • no guaranteed delivery (…it is a datagram)
  • no preservation of sequence
  • no protection against duplication
  • minimum overhead
  • adds port addressing to IP

OSI vs TCP/IP layers

Comparison between UDP and TCP/IP