In internetworking, Multiplexing is a process in which multiple data.pdf
- 1. In internetworking, Multiplexing is a process in which multiple data channels are combined into a single data or physical channel at the source. Multiplexing can be implemented at any of the OSI layers. Conversely, demultiplexing is the process of separating multiplexed data channels at the destination. In this way student data & class assignment data can be combined & separated. Types of Multiplexing There are two basic forms of multiplexing used: Time Division Multiplexing Time Division Multiplexing works by the multiplexor collecting and storing the incoming transmissions from all of the slow lines connected to it and allocating a time slice on the fast link to each in turn. The messages are sent down the high speed link one after the other. Each transmission when received can be separated according to the time slice allocated. Theoretically, the available speed of the fast link should at least be equal to the total of all of the slow speeds coming into the multiplexor so that its maximum capacity is not exceeded. Two ways of implementing TDM are: Synchronous TDM Synchronous TDM works by the muliplexor giving exactly the same amount of time to each device connected to it. This time slice is allocated even if a device has nothing to transmit. This is wasteful in that there will be many times when allocated time slots are not being used. Therefore, the use of Synchronous TDM does not guarantee maximum line usage and efficiency. Synchronous TDM is used in T1 and E1 connections. Asynchronous TDM Asynchronous TDM is a more flexible method of TDM. With Asynchronous TDM the length of time allocated is not fixed for each device but time is given to devices that have data to transmit. This version of TDM works by tagging each frame with an identification number to note which device it belongs to. This may require more processing by the multiplexor and take longer, however, the time saved by efficient and effective bandwidth utilization makes it worthwhile. Asynchronous TDM allows more devices than there is physical bandwidth for. This type of TDM is used in Asynchronous Transfer Mode (ATM) networks. Frequency Division Multiplexing Frequency Division Multiplexing (FDM) works by transmitting all of the signals along the same high speed link simultaneously with each signal set at a different frequency. For FDM to work properly frequency overlap must be avoided. Therefore, the link must have sufficient bandwidth to be able to carry the wide range of frequencies required. The demultiplexor at the receiving end
- 2. works by dividing the signals by tuning into the appropriate frequency. FDM operates in a similar way to radio broadcasting where a number of different stations will broadcast simultaneously but on different frequencies. Listeners can then "tune" their radio so that it captures the frequency or station they want. FDM gives a total bandwidth greater than the combined bandwidth of the signals to be transmitted. In order to prevent signal overlap there are strips of frequency that separate the signals. These are called guard bands Wave Division Multiplexing Wave or Wavelength Division Multiplexing (WDM) is used with fibre optic cables. WDM is a technology that closely resembles frequency division multiplexing, but is specifically used to combine lots of Optical Carrier signals into a single optical fibre. The WDM technique relies on a laser that is designed to emit single colours of light. Each of the signals that is to be transmitted is then attached to a laser that will emit a different coloured light beam. All these individual light beams are then sent at the same time. At the receiving end, a device splits the combined colours back into the original individual colours again Importance of Internetworking: Internet work has clear advantages over conventional methods, First, the use of the internet allows for rapid researching of sources and information access. Internet work creates and fosters real-time collaboration on projects and ideas often negating the need for in-person conferencing. Internet work can replace local data storage by placing information into virtual clouds as safer backups onto servers. Finally the 24-7 global nature of the internet permits constant operation at all times. This further increases productivity by ensuring virtually uninterrupted access to work and data. Challenges in Internetworking: Implementing a functional internetwork is no simple task. Many challenges must be faced, especially in the areas of connectivity, reliability, network management, and flexibility. Each area is key in establishing an efficient and effective internetwork. The challenge when connecting various systems is to support communication between disparate technologies. Different sites, for example, may use different types of media, or they might operate at varying speeds. Another essential consideration, reliable service, must be maintained in any internetwork. Individual users and entire organizations depend on consistent, reliable access to network resources. Furthermore, network management must provide centralized support and troubleshooting capabilities in an internetwork. Configuration, security, performance, and other issues must be adequately addressed for the internetwork to function smoothly.
- 3. Flexibility, the final concern, is necessary for network expansion and new applications and services, among other factor. Solution In internetworking, Multiplexing is a process in which multiple data channels are combined into a single data or physical channel at the source. Multiplexing can be implemented at any of the OSI layers. Conversely, demultiplexing is the process of separating multiplexed data channels at the destination. In this way student data & class assignment data can be combined & separated. Types of Multiplexing There are two basic forms of multiplexing used: Time Division Multiplexing Time Division Multiplexing works by the multiplexor collecting and storing the incoming transmissions from all of the slow lines connected to it and allocating a time slice on the fast link to each in turn. The messages are sent down the high speed link one after the other. Each transmission when received can be separated according to the time slice allocated. Theoretically, the available speed of the fast link should at least be equal to the total of all of the slow speeds coming into the multiplexor so that its maximum capacity is not exceeded. Two ways of implementing TDM are: Synchronous TDM Synchronous TDM works by the muliplexor giving exactly the same amount of time to each device connected to it. This time slice is allocated even if a device has nothing to transmit. This is wasteful in that there will be many times when allocated time slots are not being used. Therefore, the use of Synchronous TDM does not guarantee maximum line usage and efficiency. Synchronous TDM is used in T1 and E1 connections. Asynchronous TDM Asynchronous TDM is a more flexible method of TDM. With Asynchronous TDM the length of time allocated is not fixed for each device but time is given to devices that have data to transmit. This version of TDM works by tagging each frame with an identification number to note which device it belongs to. This may require more processing by the multiplexor and take longer, however, the time saved by efficient and effective bandwidth utilization makes it worthwhile. Asynchronous TDM allows more devices than there is physical bandwidth for. This type of TDM is used in Asynchronous Transfer Mode (ATM) networks. Frequency Division Multiplexing
- 4. Frequency Division Multiplexing (FDM) works by transmitting all of the signals along the same high speed link simultaneously with each signal set at a different frequency. For FDM to work properly frequency overlap must be avoided. Therefore, the link must have sufficient bandwidth to be able to carry the wide range of frequencies required. The demultiplexor at the receiving end works by dividing the signals by tuning into the appropriate frequency. FDM operates in a similar way to radio broadcasting where a number of different stations will broadcast simultaneously but on different frequencies. Listeners can then "tune" their radio so that it captures the frequency or station they want. FDM gives a total bandwidth greater than the combined bandwidth of the signals to be transmitted. In order to prevent signal overlap there are strips of frequency that separate the signals. These are called guard bands Wave Division Multiplexing Wave or Wavelength Division Multiplexing (WDM) is used with fibre optic cables. WDM is a technology that closely resembles frequency division multiplexing, but is specifically used to combine lots of Optical Carrier signals into a single optical fibre. The WDM technique relies on a laser that is designed to emit single colours of light. Each of the signals that is to be transmitted is then attached to a laser that will emit a different coloured light beam. All these individual light beams are then sent at the same time. At the receiving end, a device splits the combined colours back into the original individual colours again Importance of Internetworking: Internet work has clear advantages over conventional methods, First, the use of the internet allows for rapid researching of sources and information access. Internet work creates and fosters real-time collaboration on projects and ideas often negating the need for in-person conferencing. Internet work can replace local data storage by placing information into virtual clouds as safer backups onto servers. Finally the 24-7 global nature of the internet permits constant operation at all times. This further increases productivity by ensuring virtually uninterrupted access to work and data. Challenges in Internetworking: Implementing a functional internetwork is no simple task. Many challenges must be faced, especially in the areas of connectivity, reliability, network management, and flexibility. Each area is key in establishing an efficient and effective internetwork. The challenge when connecting various systems is to support communication between disparate technologies. Different sites, for example, may use different types of media, or they might operate at varying speeds. Another essential consideration, reliable service, must be maintained in any internetwork. Individual users and entire organizations depend on consistent, reliable access to network
- 5. resources. Furthermore, network management must provide centralized support and troubleshooting capabilities in an internetwork. Configuration, security, performance, and other issues must be adequately addressed for the internetwork to function smoothly. Flexibility, the final concern, is necessary for network expansion and new applications and services, among other factor.