MOD 8 UNIT 2B

• Bandwidth MUST be managed properly to prevent a delay/loss of voice, data, or message traffic between users and their distant end

BANDWIDTH ALLOCATIONS 

• Classifying how networks distribute total bandwidth to their connected users 

• Four types

  • Conventional

    • Fixed amount of bandwidth that is common to all users 

    • Mos predictable, least efficient 

    • Each channel dedicated to specific user
      
      

  • Demand Assigned

    • Based on individual bandwidth needs of the user 

    • Managed more efficiently than conventional 

    • Does not dedicate any of its channels to a specific user 

    • Allocated on an AS NEEDED basis

    • When user disconnects, bandwidth is freed up 

    • Limitation is available bandwidth may not be enough for user, causing slower speed until bandwidth frees up

    • EXAMPLE IS INTERNET
      
      

  • Dynamic

    • When combined data rates of input exceed total bandwidth of network 

    • Only cause problems if all users go online at same time or transmit at same time 

    • Transmission occurs in burst with gaps in between
      
      

  • Time Of Day Restriction

    • Ensures enough bandwidth is set aside for specific time and date of the day on a priority basis
      
      

• NETWORK INFRASTRUCTURE 

  • Network is formed when at least TWO users communicate with each other when exchanging data across form of transmission line or media 

  • Protocol, transmission media, physical components affect overall output bandwidth when transmitted with other users whose design must also be considered
    
    

• EIA STANDARDS

  • How a node is designed is driven by a set of standards (protocols) developed by Electronics Industries Association (EIA)

  • Determine how computers communicate with each other across network

  • Primarily based on distance between nodes and data rate at which the nodes need to transmit 

  • Mandate use of certain cables and connectors as well as modems or line drivers 

  • Modem is required if data travels beyond minimum distance set forth by each EIA standard

  • Modems maintain integrity of transmitted data by converting DIGITAL to ANALOG
    
    

• EIA-232C

  • Developed 1962

  • Oldest standard developed for serial communication between modem and terminals 

  • Provides compatibility between various communications devices such as modems and computer

  • Military equivalent is 188C
    
    

• DATA TERMINAL EQUIPMENT (DTE)

  • Created along side EIA-232 Standard

  • Considered by EIA as computer or user node on both sides of a network 

  • Means that it is the source and destination of the data that is sent across a transmission medium to the distant end node 

  • DTE is any device that exist at end of data chain
    
    

• DATA COMMUNICATION EQUIPMENT (DCE)

  • Referred to by the EIA as modem on both sides of a network 

  • Any device that connects TWO DTE devices together using serial cables 

  • Establishes, maintains, terminates a data transfer 

  • Also includes specific transmission medium that the data travels across 

  • Converts (or codes) signals for communications between DTE and data circuits
    
    

• EIA-530

  • Developed in response to disadvantage of the EIA -449

  • Has physical specification of a 25 pin D type connector

TRANSMISSION MEDIA

• TWISTED PAIR

  • Example of balanced transmission media 

  • Made up of two conductors of a single circuit that are twisted together for improving electromagnetic compatibility 

  • Improves Electromagnetic radiation and improves rejection of EMI and noise

  • Twisted pair categorized by amount of data they can transmit
    
    

• COAXIAL CABLE

  • Unbalanced transmission media 

  • Made up of inner conductor with insulated shielding and grounded mesh shielding enclosed in jacket 

  • Can transmit all types of signals at once 

  • Can support baseband or broadband network 

  • Baseband transmit ONE signal at a time 

  • Broadband modulates different frequencies to transmit multiple signals simultaneously

  • Most popular types of cabling in RF field 

  • Two types of transmission lines are balanced and unbalanced
    
    

    • BALANCED

      • Balanced line carry identical signals on two separate input/output wires (one positive and one negative) 

      • Carry two identical input signals 180 degrees out of phase with each other 

      • Twisted pair uses balanced
        
        

    • UNBALANCED

      • Carry signals on just ONE input/output wire while the second wire is ground 

      • Known as SINGLE ENDED TRANSMISSION

      • Used by Coaxial Cables
        
        

  • FIBER OPTICS

    • Transmit using light instead of electricity 

    • Offers same capabilities as Coaxial cable but with greater speeds, allowing more data transfer 

    • Maximum distance is a little over a mile 

    • Allows for noise/EMI free data transmission over its length
      
      

  • WIRELESS

    • Communication without the use of wires 

    • Major disadvantage to satellite communications is time delay 

    • Wireless transmission can be either directional or omnidirectional 

    • Satellite and troposcatter are both directional wireless
      
      

CARRIER SYSTEM CONCEPTS

• DIGITAL SERVICE UNIT (DSU)

  • Can be single device operating alongside Channel Service Unit (CSU)

  • Or operates in the same device with the CSU

  • Responsible for managing interface with the DTE
    
    

• CHANNEL SERVICE UNIT (CSU)

  • Operates alongside the DSU

  • Responsible for connection to the telecommunications network
    
    

• DIGITAL NETWORK HIERARCHY

  • Bell System Laboratories developed this

  • Logical sequence in building transmission rate in a network