Software Defined Networking (SDN)

Question: Discuss about the Essay for Software Defined Networking (SDN)? Answer: Introduction: The paper describes the function of a multiplexer in a data communication network. The assignment discusses in detail three important points; Difference between various forms of multiplexers, the multiplexing involved in different levels of OSI model of a network, the reasons for using a particular form of the multiplexer in the system. The first point discusses the difference between analog and a digital multiplexer as well as three special types of multiplexing; FDM, WDM and TDM. The second point explains the use of multiplexer in the seven layers of the OSI model. Moreover, the last point of the paper discusses the application of the particular type of multiplexer in the layers of the network. Multiplexer and its Variants: The multiplexer can be defined as a switch that takes multiple inputs and returns single output. The multiplexer can take both analog and digital type of information and convert it into a single output. The two most crucial features of the multiplexer are data selection as well as amplification. The multiplexer can select particular data lines to send output (Stacey, 2015). The transmission conductors for the multiplexer can be copper wire or optical fiber cable in a network. The multiplexer can amplify the transmitted data or information in a range of a particular bandwidth and time. The two primary type of multiplexer is analog and digital. Fig 1. Multiplexer in a network (Source: Industrialnetworking.com, 2016) Various form of multiplexer: Analog multiplexer transmits analog signal using its input lines. The analog multiplexing is further divided in FDM and WDM (Diab Powell, 2015). FDM: This type of analog multiplexing works with the various range of frequency and modulates the frequencies to combine in a single output frequency. The bandwidth ranges of the channels segregate the different range of frequencies. The unused bandwidth or the guard bands can overcome the overlapping of input signals (Giles et al., 2014). The frequency range for FDM or frequency division multiplexing is 80-108 MHz where each channel uses approximately 700MHz of frequency. The disadvantage of FDM is the need of the analog filter, which has a problem of phase error. Moreover, analog signals work on limited frequency range and the amplifiers for this type of multiplexing are complex and linear ( Willner, 2015). Fig 2. FDM (Source: Historyofcomputercommunications.info, 2016) WDM: The wavelength division multiplexing is based on the wavelength of the light. The data signal transmitted by the multiplexer depends on the principle of prism and light beam. The transmission lines of the multiplexer use the fiber optics for data transmission (Xia et al., 2015). The WDM is similar to the FDM but is based on the wavelength of the light, which is reciprocal of the frequency. Fig 3. WDM (Source: precisionopticaltransceivers, 2016) The digital multiplexer transmits the digital signals over the transmission channel. Time division multiplexing is a type of digital multiplexing. TDM: This kind of multiplexing combines data streams with different time slots in a frame. The signals are arranged sequentially. The number of data lines is equivalent to the number of timeslots. For n numbers of data lines, the TDM creates n time slots. TDM can be further divided into Synchronous as well as asynchronous TDM (Amaya et al., 2014). Synchronous TDM: In this type of multiplexing, the time slot is selected same for all the data slots for data transmission. The digital signal transmission is comparatively simpler than the analog signal transmission. However, this kind of multiplexing is the wastage of bandwidth. Asynchronous TDM: This type of multiplexing is also known as statistical TDM. This is a flexible way of multiplexing and the time is allocated to the slot, which wants to transmit data. The bandwidth wastage problem of the synchronous TDM is overcome in this case (Sasaki et al., 2015). The TDM tags each frame with an ID number for its device thus increasing the processing of the multiplexer but the efficient utilization of bandwidth is the primary advantage of its use. Fig 4. TDM (Source: Gordostuff.com, 2015) SDM: The space division multiplexing uses a point-to-point or series connection between electrical conductors for data transmission (Feuer et al., 2013). This type of multiplexing is suitable for the multi-node cables as well as other network topologies like star or mesh network. For the wireless communication, the multiplexing uses phased array antenna for MIMO, SIMO or MISO type of data transmission. Fig 5. SDM (Source: Ustudy.in, 2016) The other principal types of multiplexing include DWDM, OFDM, and ROADM, etc. The DWDM or the dense wavelength division multiplexing depends on the expanded bandwidth of fiber optics technique. With the advantages of bit rate and protocol independence, this type of multiplexing can transmit data in various kinds of channel like IP, SONET, and Ethernet, etc. The OFDM can transmit perpendicular subcarrier signals over parallel channels (Leigh Weidele , 2013). This kind of multiplexing can deal with channel issues like attenuation, interference, etc. as this works with slowly modulated narrowband signals. ROADM is a kind of add -drop multiplier that depends on the WDM and can choose, pass or redirect its kind of signal (light beams or infrared) for data transmission. Multiplexing and OSI layers: Multiplexing is the procedure of combining multiple signals like wavelength, timeslot or frequency and sending the signal over the channel to its receiver. Some layers of the OSI network model supports the Multiplexing as data transmission is an important option for the networking (Walker et al., 2013). The lowest layer of the OSI model or the physical layer includes the hardware part of the networking like cables, Ethernet as well as other equipment for the data transmission. The second lowest layer or the data link layer are divided into two sub-layers media access control and logical link control for the data framing, synchronization as well as the data flow control. The physical layer supports FDM for high speed of data transfer. The multiplexing in the physical layer is known as the circuit level multiplexing (Richardson et al., 2013). The AIM and BONDING protocols are used for this type of multiplexing where data streams are distributed over available circuits as well as the eq uipment (Mori et al., 2015). Moreover, the data link layer is the connection between the physical and network layer of the OSI model. The LLC sub layer of the data link control uses multiplexing/demultiplexing to combine the L3 protocols like IP, IPX as well as AppleTalk for multipoint network connection. The other sub layer or the Mac layer implements the collision resolution protocols like CSMA, CSMA/CD in half or full duplex mode using the same multiplexing technique ( Dendy et al., 2016). The network layer of the OSI model is responsible for the switching and routing techniques for data transmission. The packet, as well as the frame of data, is passed through this layer. The network layer deals with the control of the overall system. The network layer also uses the firewall and another security mechanism for the data security (Helms Brooks, 2014). This layer uses packet level multiplexing technique with MP and MPP protocols. The layer sends multiple packets over the different channel for the multiplexing. Moreover, the network layer uses TDM for digital data transmission as well as some unique multiplexing techniques like ROADM for adding, bypassing, blocking as the requirement of data transmission. The layer 4 or the transport layer works on the data flow control as well as error recovery (Bozinovic et al., 2013). SPX, TCP as well as UDP are the protocols used in the network layer. The transport layer is responsible for the huge amount of data transfer. Therefore, t he multiplexing technique like FDM for analog and TDM is used for data frame as well as packet transmission. The asynchronous TDM is the useful technique for multiplexing the required information in the transport layer. The network layer also uses the inverse multiplexing technique for slow data stream transmission. The next layer or the session layer establishes a connection between two applications. The maintenance, as well as the termination of the session, is also dependent on the session layer. The layer 5 depends on the application connection like NetBIOS, NFS, RPC as well as the database like SQL, etc. The synchronization of data streams overcomes the issues of data loss or data hiding in the network. As the session, layer deals with the session of the used applications multiplexing of the data and information use a particular type (Ciurana et al., 2014). The multiplexing is known as Session multiplexing. The session multiplexing is used in both means of transport as well as the session layer. This kind of multiplexing deals with the application type like a single computer with a particular IP address opens multiple web pages in the internet browser. The other application multiplexing includes the backend database connection to the internet browser. The various WebPages can be updated usi ng the stored procedures in the single interface of database like MYSQL, SQL Server, etc. The sixth layer of the OSI network model is the presentation layer. The presentation layer converts the different data types in a mode that are receivable by the application layer or the topmost layer of the OSI model. The conversion mechanism includes encryption as well as other cryptographic techniques etc. The compression as well as the decompression techniques also are used in the sixth layer of the network model (Mori et al., 2015). The presentation layer multiplexing includes combining multiple data streams into a single file and transmitting it to the top layer or the application layer. The topmost or the seventh layer of the OSI model of the network receives the data from the presentation layer. The working of the Application layer includes remote file and server access, internal process communication, mail and directory services as well as the virtual as well as the network management. The network software service, email services are included in the working of the layer (Helms Brooks, 2014). The protocols like Telnet, FTP are used in the application layer of the OSI network model. The term application layer multiplexing means sending multiple emails and attachments to a single user. The CDM or code division multiplexing is used in the application layer. Particular form of multiplexer in a network: The primary function of a multiplexer is to combine multiple data lines or signals to produce the single data lines or output. The networks are consist of seven (OSI) or four layers (TCP/IP), but the applications of the network layers in the different model are nearly same. However, the OSI is stood on its seven layers; the underlying layers are same; physical, network, application and internet layer. The type of multiplexing is based on the function of the particular tier. In the physical, layer the circuit/ hardware base multiplexing is suitable. In the case of network layer the packet, based multiplexing can be used considering the layer of protocols on the network interface. The application layer should use streamline multiplexing for data packets as well as the data frame (Ciurana et al., 2014). The internet layer is linked with network layer to use both data stream and packet multiplexing. Conclusion: The assignment discusses on the topic of different type of multiplexer as well as the multiplexing techniques. The type of multiplexers includes analog and digital types of multiplexers as well as other variations like OFDM, DWDM etc. The analog types include the frequency division and wave division multiplexing and the digital multiplexing include the time division multiplexing. The TDM is further divided into Synchronous as well as Asynchronous multiplexing. The paper also explains the multiplexing used in the seven layers of the OSI model. The OSI layers define the multiplexing in each layer depending on the functionality of individual layers. 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