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Data Communications and Network Architectures
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Data Communications and Network Architectures
Data Communications and Network Architectures
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1
Question
How can data communication networks affect businesses?
Page 1
Answer
Data communication networks can affect businesses by being the foundations for distributed systems in which information system applications are divided among a network of computers. They facilitate more efficient use of computers and improve day-to-day business control through faster information flow, aiding strategic competitive advantage. They also provide message transfer services, such as electronic mail.
2
Question
Discuss three important applications of data communication networks in business and personal use.
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Answer
Email, videoconferencing, and the Internet.
3
Question
How do LANs differ from WANs, and BNs?
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Answer
A Local Area Network (LAN) is a group of microcomputers or terminals located in the same general area. A Backbone Network (BN) is a large central network that connects most everything on a single company site. A Metropolitan Area Network (MAN) encompasses a city or county area. A Wide Area Network (WAN) spans cities, states, or national boundaries. Typically, MANs and WANs used leased facilities, while LANs and BNs are often located internally in an organization and used owned facilities.
4
Question
What is a circuit?
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Answer
A circuit is the pathway through which messages travel. The single end-to-end connection is called the circuit, regardless of the equipment or physical facilities it passes across. It can use copper wire, fiber optic cable, or wireless transmission. Hubs, switches, routers, and gateways can perform functions along its path.
5
Question
What is a client?
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Answer
The client is the input or output hardware device at the other end of a communication circuit. It typically provides remote users with access to the network and the data and software on the server.
6
Question
What is a server?
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Answer
The server stores data or software that can be accessed by clients, or remote users of a hardware input or output device. In client-server computing, several servers may work together over the network to support the business application.
7
Question
Why are network layers important?
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Answer
Communication networks are divided into separately defined layers so vendors can develop software and hardware that work together. Layers simplify development and comprehension of complex networks. They enable different equipment to connect over a common platform using protocols and standards applicable to each layer.
8
Question
Describe the seven layers in the OSI network model and what they do.
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Answer
The application layer is the application software used by the network user. The presentation layer formats data for presentation to the user and accommodates different interfaces. The session layer initiates, maintains, and terminates logical sessions between end users. The transport layer establishes, maintains, and terminates logical connections for end-to-end data transfer. The network layer addresses messages, determines their route, and records message accounting information. The data link layer formats message boundaries, decides when to transmit over physical media, and detects and corrects transmission errors. The physical layer is the physical connection between sender and receiver, including hardware devices and physical media.
9
Question
Describe the five layers in the Internet network model and what they do.
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Answer
The application layer is the application software used by the network user. The transport layer deals with end-to-end issues by establishing, maintaining, and terminating logical connections for data transfer. The network layer addresses messages, determines their route, and records message accounting information. The data link layer formats message boundaries, decides when to transmit, and detects and corrects transmission errors. The physical layer is the physical connection between sender and receiver, including hardware devices and physical media.
10
Question
Explain how a message is transmitted from one computer to another using layers.
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Answer
The application layer is the application software used by the network user. The transport layer obtains the end-user address if needed, breaks large transmissions into smaller packets if needed, ensures packets are received, eliminates duplicates, and performs flow control. The network layer breaks messages into smaller ones if necessary, addresses them, determines their route, and records message accounting information. The data link layer formats message boundaries, decides when to transmit over physical media, and detects and corrects transmission errors. The physical layer provides the connection between sender and receiver through hardware devices and physical media.
11
Question
Describe the three stages of standardization.
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Answer
The three stages are specification, identification of choices, and acceptance. Specification develops a nomenclature and identifies problems to address. Identification of choices considers possible solutions and selects the optimum alternative. Acceptance defines the solution and obtains agreement from recognized industry leaders on a single, uniform solution.
12
Question
How are Internet standards developed?
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Answer
The Internet Engineering Task Force (IETF) sets standards governing how much of the Internet will operate. A standard usually begins as a vendor-developed protocol. IETF forms a technical-expert working group to examine the protocol, identify problems and possible improvements, and report to IETF. If the report is favorable, IETF issues a Request for Comment (RFC) soliciting worldwide comments. Once no additional changes are identified, it becomes a Proposed Standard. After at least two vendors develop software based on it and it proves successful in operation, it becomes a Draft Standard. Some protocols are elevated to Internet Standards, usually signifying a mature standard unlikely to change.
13
Question
Describe two important data communications standards-making bodies. How do they differ?
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Answer
The International Organization for Standardization (ISO) makes technical recommendations about data communication interfaces. The Telecommunications group (ITU-T) is the technical standards-setting organization of the United Nations International Telecommunications Union (ITU). ITU-T establishes recommendations for use by Postal Telephone and Telegraphs (PTTs), other common carriers, and hardware and software vendors. The ISO created the OSI model.
14
Question
What is the purpose of a data communications standard?
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Answer
Standards make it easier to develop software and hardware that link different networks because they can be developed one layer at a time. Software or hardware defined by a standard at one network layer can be updated easily as long as the interfaces with adjacent layers remain unchanged.
15
Question
What are three of the largest inter-exchange carriers (IXCs) in North America?
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Answer
Two of the largest inter-exchange carriers (IXCs) in North America are AT&T and Sprint, and the formerly large MCI was acquired in a post bankruptcy merger with Verizon.
16
Question
Discuss three trends in communications and networking.
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Answer
Pervasive networking means high-speed communications networks everywhere, with virtually any device able to communicate with any other device in the world; network prices will drop and economic globalization will accelerate. Integration of voice, video, and data onto the same networks will simplify networks and enable access to any media at any point. Pervasive, integrated networks will increase information availability and new information services; application service providers may evolve to act as information utilities.
17
Question
Why has the Internet model replaced the OSI model?
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Answer
The Internet model is simpler and easier to remember and understand, effectively collapsing the top three OSI layers into a single model. The ISO OSI Reference Model results from a formal standardization process and is technical in its presentation. The Internet model is suited to practical needs related to implementing the Internet and networking. The Internet model now separately identifies the transport layer, yielding five layers for comprehension.
18
Question
In the 1980s, why has the number of commonly used protocols at the data link, network, and transport layers declined?
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Answer
There is convergence around the non-proprietary use of TCP/IP as the protocol of choice for networks. TCP/IP is interoperable and portable to any manufacturer's hardware, and manufacturers are developing products to use it. This reduces incompatibilities among proprietary networks. The decline is also related to increased competition and better price availability from vendors supporting TCP/IP.
19
Question
The number of standardized protocols in use at the application layer has significantly increased from the 1980s to today. Why?
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Answer
The biggest reason is the predominant use of the Web and its standardized graphic interface, with HTTP and DHCP given as examples. Many new protocols operate on top of TCP/IP networks, including protocols developed to retrofit new technologies onto older networking architecture. Internet-related protocols have grown in importance while some proprietary protocols, such as those connected with IBM's SNA and DECNet, have declined in significance.
20
Question
How many bits (not bytes) are there in a 10 page text document? Hint: There are approximately 350 words on a double-spaced page.
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Answer
Assuming each word averages seven letters plus one space and using 8-bit ASCII: 350 words × 8 bytes = 2,800 bytes per page. For 10 pages, that is 28,000 bytes; 28,000 bytes × 8 bits per byte = 224,000 bits.
21
Question
What are the different types of application architectures?
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Answer
Host-based architecture performs all processing and stores all data on the host, with terminals providing access. Client-based architecture performs processing on the client and stores all data on the server. Client-server architecture balances processing; usually, the host provides data access and storage while the client provides application and presentation logic.
22
Question
Describe the four basic functions of an application software package.
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Answer
Data storage, data access logic, application logic, and presentation logic.
23
Question
What are the advantages and disadvantages of host-based networks versus client-server networks?
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Answer
Host-based advantages: centralized security, integrated architecture from a single vendor, and simpler centralized installation. Host-based disadvantages: processing on the host may cause overload, software and upgrades are costly, infrastructure is expensive, and terminals are totally dependent on the server. Client-server advantages: balanced processing demands, lower cost and inexpensive infrastructure, use of software and hardware from different vendors, and scalability. Client-server disadvantages: problems can arise when using products from different vendors, and installation or updating is more complex, although automated installation software helps.
24
Question
What is middleware and what does it do?
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Answer
Middleware manages client-server message transfer and shields application software from the effects of hardware changes. It provides standard communication between products from different vendors through translation.
25
Question
Suppose an organization switches from a host-based architecture to client-server. What problems might it encounter?
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Answer
Cabling, hardware, and software infrastructure may need redesign. The organization may need staff to manage the LAN, address workstation security, and handle more complex upgrades.
26
Question
Which network architecture is described as less expensive, and why?
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Answer
Client-server networks are less expensive because competitive vendors offer lower-cost software and hardware upgrades. Host-based upgrades can require large, discrete expenditure increases, whereas LAN deployment can follow a smoother cost curve.
27
Question
How do two-tiered, three-tiered, and n-tiered client-server architectures differ?
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Answer
Two-tiered architectures contain clients and servers. Three-tiered architectures separate presentation, application, and data-access logic and storage. N-tiered architectures may use multiple tiers for application logic, often including a Web-server tier.
28
Question
How do thin clients differ from thick clients in application logic and costs?
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Answer
Thick clients support all or most application logic; thin clients support little or none. Development and maintenance costs can be higher in complex thick-client environments.
29
Question
Which benefits of cloud computing are identified in this section?
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Answer
Cloud computing can provide access to experts who manage the cloud, potentially lower costs, scalability, and pay-as-you-go pricing.
30
Question
Which parts make up an HTTP request, and which part is required?
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Answer
An HTTP request contains a request line, request header, and request body. Only the request line is required; the header and body are optional.