NOTE: Free essay sample provided on this page should be used for references or sample purposes only. The sample essay is available to anyone, so any direct quoting without mentioning the source will be considered plagiarism by schools, colleges and universities that use plagiarism detection software. To get a completely brand-new, plagiarism-free essay, please use our essay writing service.
One click instant price quote
Introduction To Communications And Networking Essay, Research Introduction To Communications And Networking Digital to Analog Conversions Digital to analog, and analog to digital conversions, typically performed by D/A and A/D converters, became a necessity when digital systems were first introduced. Digital systems were introduced so that the information transmitted across the wires or network could be controlled, manipulated and reproduced when needed. Analog systems have an inherent noise that can not be removed and could potentially destroy the quality needed of a communications system. With digital systems, the noise was removed and control was gained. Voice digitization is a good example of the power of using a digital method for communications rather than analog.
With voice, the analog signal is sampled at approximately a rate of 8000 Hertz. This means that 8000 times per second, a computer is tracking the amplitude and frequency of the human voice and converting it into digitized levels base on the bandwidth allocated to the system channel. (i. e. 8 bits channel width could provide 256 distinct variations in the human voice that could be interpreted by the receiver of the data. The receiver could then recreate the analog signal based on those digitized levels.
The problem with this is that when the bandwidth allotted is not wide enough for proper leveling of the signal. The recreation of the signal into an analog sound would result in tinny or unrealistic sounds not truly made by the sender. However, the control and accuracy of the transmitted signal make up for this problem. Protocols A protocol is a set of rules formulated to control the exchange of data between two or more communicating devices. They are the components of communications architectures which are guidelines on how environments connecting two or more devices can be constructed, so most components of a given architecture in a network will be found on each communicating computer in that network. Protocols provide the rules of communications between counterpart components on difference devices.
Components for a major protocol, the OSI protocol, are the Physical, Data Link, Network, Transport, Session, Presentation, and Application layers. Each of these have a specific lower level data communication protocol in which they perform inter-layer data transfer. Due to the use of protocols and thus standards, we are able to bring communication technology to a greater level of efficiency and allow for greater ease connectivity. Error Checking Error checking is typically performed when data is being transmitted between two Dte's especially if he transmission lines are very noisy, as they are in PSTNs, or a low bit error rate is necessary as with file transfers. Error checking ensures that information received by a destination DTE has a high probability of being the same as that transmitted by the sending DTE. Error checking protocols allow the receiver to deduce, to a high probability, when received information contains errors.
If errors are determined to be present then a mechanism is required to obtain a copy of the original information. There are two main approaches for achieving error free communications. One is Forward Error Control and the other is Feedback Error Control. Forward Error Control transmits additional character or frame information so the receiver can detect and error and correct the error as well. This requires substantial additional space and thus lowered data throughput but allows for decreased if not eliminated retransmissions and approaches flawless data transmission to occur.
Some prominent names for error checking mechanisms are Parity Error Checking, Vertical Redundancy Check (VRC), Longitudinal Redundancy Check (LRC) and Cyclic Redundancy Check (CRC). Note that Cyclic Redundancy Error checking is the most common as is typically used for system that have inherent burst errors. T-Carrier Systems T-Carrier systems were developed to provide increased efficiency in the wire-pair cable facilities already in heavy use. This new digital system of communications became very used because is increased the call-carrying capacity while taking advantage of the unused transmission capacity of existing systems. The T-Carrier evolution is important due to a number of reasons.
It was the first successful system designed to utilize digitized voice transmission. It identified many of the standards that are employed today digital switching, digital transmission, including the modulation techniques. It established the digital transmission rate at 1. 5 M bits per second and also established protocols and constraints found today for other types of transmission communications. T 1 became the first named format, using framed formats, for the T-Carrier systems. All other today are aggregates of the T 1 line. T 1 uses the framed format which implements the pulse code modulation scheme.
There are 24 channels that are time-division multiplexed into a frame to be carried along the line of communications. Each frame represents 1 sample of 8 bits from each 24 channels resulting in 192 bits. There are 8000 frames per second and there is 8 Kbds of framing overhead. Adding the 8 Kbps overhead to the 1. 536 Mbps for data transmission we get a total of 1. 544 Mbps for each T 1 line or 24 channels of multiplexed communications. Note there is 64 Kbps information capacity in each channel on the 24 channel T 1 line. Other common names for T 1 aggregates are as follows: DS 0 1 channel on a T 1 line giving 64 Kbps.
DS 1 Equivalent to a T 1 line giving 24 channels of 64 Kbps each totaling to 1. 544 Mbps. DS 3 Equivalent to 28 T 1 lines, or 28 DS 1 lines, at 1. 544 Mbps each totaling to 44. 737 Mbps. DS 4 Equivalent to 63 T 1 lines, or 6 DS 3 lines, totaling to 274. 176 Mbps. Standards, Open Systems and Proprietary Systems Standards are set in the communications field so that all users of the network will abide by one set of rules thus allowing more interconnectivity and interoperability between users. Defacto standards differ from Dejure standards in that defacto implies that all communities naturally accept a given set of rules for a particular communication systems over time. Whereas a Dejure standard is one that is ruled into place as having to be accepted be decree or law or governing authority An Open system is a vendor-independent set of interconnected computers that all utilize the same standard communications protocol stack based on ether the ISO/OSI protocols or TCP/IP.
Proprietary systems are communications systems in which only the vendor knows the specific protocol and does not allow other vendors or users to the documentation explaining the protocol. This stops anyone from building any equipment that can communicate with these proprietary systems. Proprietary systems are the complete opposite in meaning to that of Open Systems since it does not allow a choice of vendors for connectable communication products. X. 25 Packet Switching X. 25 is an internationally agreed upon standard protocol defined for an interface of a data terminal device, such as a computer, to a packet switched data network. X. 25 was brought about since TDM became limited due to its fixed bandwidth allocation. X. 25 allows bandwidth to be allocated on the fly.
When a user of the X. 25 network, otherwise called ethernet network, needs to send data, it packetizes the data into small individual packets and bursts them across the network as needed. The network allocates and keeps tracks of the virtual circuit created to deliver the packets. All packets delivered under a X. 25 protocol is guaranteed to be delivered with integrity. The packets are assembled and disassembled using a PAD or Packet Assemble/Disassemble device. The PAD allows a charter-mode terminal to communicate with a packet-mode orientated device.
The X. 25 protocol was the first attempt to packet ize information for transmission. The advent of the T- 1 communication lines, which were originally designed for voice, brought about the X. 25 protocol that is now so widely in use. However, the X. 25 was originally designed to carry digitized data across a network so that a terminal located away from the central server could communicate together. Advantages with packet switching are shared user access, full error control and flow control for smooth and efficient transfer of data, protection of intermediate link and node failures, and lowered cost because the network is used by many and the price is then based on a packet-by-packet basis. The outstanding drawback realized when using this type of network is the decrease in speed due to data overhead on each small packet, buffering of multiple packets along the route, the CRC performance at each node and the final sequenced data delivery. Ethernet The name of the LAN invented at Xerox Cooperation Palo Alto Research Center.
It operates using the Carrier Sense Multiple Access/ Collision Detection (CSMA/CD) medium access control method. The early specification was refined by a joint team from Digital Equipment Corporation, Intel Corporation and Xerox Corporation and this is in turn now superseded by the IEEE 802. 3 ISO 8802. 3 International Standard. Ethernet is commonly referred to as CSMA/CD and is typically known as a 10 Mbps baseband coaxial cable media communications system. Other cable media are supported such as 10 Base 2 (thin-wire), 10 Base 5 (thick-wire), 10 Base T (Hub / star topology with twisted pair drop cables) and 10 Base F (Hub / star topology with optical fiber drop cables). All media, regardless of what type, operate using the same Media Access Control (MAC) method. The Ethernet protocol essentially allows anyone to communicate to anyone that is connected to the network while all other can listen.
In case of a collision during frame transmission, the senders each wait a exponentially random time until they try to transmit again. This type of network protocol allows for a large number of users on the system to communicate with one another efficiently when less than high loads of traffic are occurring. Also, the hardware and software to implement this network is much simpler since the protocols are simple. Token Ring Token ring networks are used primarily in technical and office environments. All Dte's are connected to a neighboring DTE and thus make a ring defined network. Instead of a sender transmitting whenever necessary, a token must be grabbed from the ring network in order to transmit.
This ensures that only on sender is transmitting at any given time on the network. The data transmission rates started out as 4 Mbps and then increased to 16 Mbps as they are currently implemented. If using fiber optical cabling, then 100 Mbps can be achieved. The jump from 4 Mbps to 16 Mbps was achieve simply by a concept known as Early Token Release where by immediately after transmitting the data the token was transmitted as well thus allowing a sender to grab the token earlier and thus transmit sooner. Routers A router is a device used to interconnect two or more LANs together, each of which operates with a different medium access control method also known as a gateway or intermediate system. Routers are expensive in cost and slower in speed than bridges (which control access to locations and connect similar communication networks together) because they combine different communication protocols together and transform packets or frames for transmission out another path of the router.
A router can be reprogrammed to handle various transmission protocols and is done so by changing the Application specific Integrated Chipset (ASIC). The ASIC is the hardware device that allows for fast transmission of the packets into the router and then out from the router toward the packets destination. Baseband Vs. Broadband Broadband is typically the definition given to communications systems that are analog or systems that use the entire bandwidth of its inherent medium in which it is communicating.
Baseband is generally thought of as digital communications or systems that are limited in size to a smaller portion of the true bandwidth that is available. Baseband systems are lower in cost whereas broadband systems have higher throughput. Most non-wireless LANs and WANs are baseband systems whereas Frequency Division Multiple Access (FDMA) systems are broadband. The line between baseband and broadband systems is a very fine one and can typically be though of as being both depending on its context of communication spectrum provided and available.
Free research essays on topics related to: set of rules, packet switching, type of network, access control, multiple access
Research essay sample on Set Of Rules Type Of Network
