Business Data Communications, William Stalling - Sixth Edition

Front 1

Asynchronous Transfer Mode (ATM)

Back 1

Cell Relay; a culmination of developments in circuit switching and packet switching. ATM uses fixed-length packets, called cells.

Front 2

Circuit Switching

Back 2

Network where a dedicated communication path is established between two stations through the nodes of the network. Path is a connected sequence of physical links between nodes. Data generated by the source station are transmitted along the dedicated path as fast as possible. I.E., Telephone Network.

Front 3

Client/Server

Back 3

Separate computers (servers) support database functions, store files, perform printing services and provide other specialized functions on a shared basis for many users (clients).

Front 4

Convergence

Back 4

Refers to the merger of previously distinct telephony and information technologies and markets. Brings many benefits including simplified network management, increased efficiency and greater flexibilitiy at the applicaiton level.

Front 5

Three-Layer model of Enterprise Communications

Back 5

Packet-based transmissions using the IP (Internet protocol).
Applications: integrates communications applications (voice calling, voicemail, e-mail, IMs) with business applications.
Enterprise Services: manager deals with the information network in terms of the services it supplies to support applications. (function providing system)
Infrastructure: consists of the communication links - LANs, WANs and Internet connections available to the enterprise.

Front 6

Data Communications

Back 6

Refers to any form of information transfer other than voice

Front 7

Distributed Applications

Back 7

Applications that are designed to work among a distributed set of computers for both intra-company and inter-company information exchange.
Software that executes on two or more computers in a network. In a client-server environment, distributed applications have two parts: (1) the 'front end' that requires minimal computer resources and runs on the client computer(s), and (2) the 'back end' that requires large amounts of data crunching power and/or specialized hardware, and runs on a suitably equipped server computer.

Front 8

Frame Relay

Back 8

A form of packet switching based on the use of variable-length link layer frames.. No network layer, basic functions have been streamlined or eliminated to provide for greater throughput.

Front 9

Image Communications

Back 9

Technology for storing and transmitting images , creates a demand for high-capacity networks and is one of the driving forces in the development of networking technology. Note: Important component of office environments - i.e., Fax.

Front 10

Internet

Back 10

Public telecommunication network.
A worldwide internetwork based on TCP/IP that interconnects thousands of public and private networks and millions of users.

Front 11

Local Area Network (LAN)

Back 11

A communications network that interconnects a variety of devices and provides a means for information exchange among those devices. Scope is small, typically a single building or a cluster of buildings.

Front 12

Packet Switching

Back 12

Data are sent out in a sequence of small chunks, called packets. Each packet is passed through the network from node to node along some path leading from source to destination. At each node, the entire packet is received, stored briefly and then transmitted to the next node. Commonly used for terminal-to-computer and computer-to-computer communications.

Front 13

TCP/IP

Back 13

Transmission Control Protocol/Internet Protocol: now universally used for the communications software function across multiple-vendor equipment and is the basis for the operation of the Internet.

Front 14

Unified Communications

Back 14

Focuses on the user perspective to the broad spectrum of business applications. Key elements:
1. Based on an integrated set of user interfaces and back-end connectivity for all communications services.
2. Merges real-time communications services with non-real-time collaboration and business process applications.

Front 15

Video Communications

Back 15

Becoming increasingly important in the office environment/business world. Traditionally was a one-way communication of entertainment programs. Now with the availability of high capacity transmissions links and networks, business applications are possible - i.e., video-conferencing.

Front 16

Voice Communications

Back 16

Primarily refers to telephone-related communications. Enhanced by a variety of computer-based services including voice mail and computerized telephone exchange systems. Now - VoIP protocol - merger of voice and internet technologies resulting in PBX and IP Centrex offerings that provide full internet support.

Front 17

Wide Area Networks (WANs)

Back 17

Networks that generally cover a large geographical area, require the crossing of public right-of-ways, and rely at least in part on circuits provided by a common carrier. Typically, consists of a number of interconnected switching nodes. Transmission from any attached device is routed through these internal nodes to the specified destination device. These nodes are not concerned with thee content of the data; rather their purpose is to provide a switching facility that will move the data from node to node until they reach their destination.

Front 18

Wireless Networking

Back 18

Wireless technology commonly used in both WANs and data networks. Provide advantages in the areas of mobility and ease of installation and configuration.

Front 19

Three kinds of basic organizational difficulties communications technology can help companies overcome:

Back 19

Traffic Growth: Local and Long Distance, Increasing emphasis on office automation, remote access, online transactions and other productivity measures. Struggle to maximize capacity and minimize transmission costs.
Development of New Services: Range of services expands which increases the demand for high-capacity networking and transmission facilities.
Advances in Technology: trends that enable the provision of increasing traffic capacity and the support of a wide range of services.

Front 20

Four Types of Information Found on Networks:

Back 20

IP Telephony: International and long-distance savings, Economics of converged networks, and productivity through application integration.
Multimedia Messaging: Increased productivity, reduced network expense, and integration into business workflow
e-Business: Workflow integration, productivity improvements, New applications tied to business needs , and better management of suppliers/ partners.
Customer Relationship Management: New customer acquisition; increased satisfaction for existing customers, reduced operating expenses and productivity via workflow management.

Front 21

How has the technology of the compact disc used in the music industry been used in image communications?

Back 21

The optical disc, which is similar to the compact disc, enables the storage of immense amounts of information that can be stored inexpensively as well as it being easily distributable in an office setting.

Front 22

Why are burdens on Manager greater today than in previous years?

Back 22

Because now they have to keep up with emerging technology and finding ways to incorporate it in their businesses at a reasonable cost. And by finding ways to incorporate technology into networks as well as making them secure and reliable.

Front 23

Why has optical fiber transmission become popular in the past few years?

Back 23

This transmission mode has become popular by high data transmission capacity as well as the drop in cost of this resource. Also because security characteristics of optical fiber transmission makes this resource a much sought after tool and the only issue with this mode of transmission is the bottleneck created by switching.

Front 24

What types of communications can be carried by satellite transmission?

Back 24

Voice (telephone communications), image (fax), video (video conferencing) and data such as reports, memos and other documents. Satellite transmission enables the user to have a portable terminal such as a smartphone from which the user can access the web, chat, and do other transactions over satellite transmission; it is also a huge factor in the rise of portable computing.

Front 25

Name two approaches that can be used for increasing efficiency of transmission services.

Back 25

Two approaches that can be used for increasing efficiency of transmission services are multiplexing and compression.

Front 26

Multiplexing

Back 26

Refers to the ability of a number of devices to share a transmission facility

Front 27

Compression

Back 27

involves squeezing the data down so that a lower-capacity, cheaper transmission facility can be used to meet a given demand.

Front 28

Contrast of the function of application software with that of interconnection software.

Back 28

Application software could be described as the end product of a certain application offered to users. An example of application software is multimedia messaging in which the user has access to a variety of sources by which to communicate such an e-mail and voice mail. Interconnection software is the software that makes it possible for the end user to be able to see the final product such as the interface for using emails. Interconnection software makes it possible for computers in a network to work together by communicating in the same language.

Front 29

Analog

Back 29

A continuous signal (i.e., a voltage) that can take on a continuum of values, an example is the eletrical signal coming out of a microphone when someone speaks into it. For analog communication, information rate and channel capacity are measured in (Hz)

Front 30

Virtually any comunication signal can be expressed as a combination of pure oscillations of various frequencies.

Back 30

The bandwidth measures the limits of these frequencies. The higher the frequencies allowed, the more accurately a complex signal can be represented.

Front 31

Audio Service

Back 31

Supports applications beased on sound, usually of the human voice. Primary application - telephone communication

Front 32

Centrex

Back 32

a telephone company offering that provides the same sort of service as a PBX but performs the switching function in equipment located in the telephone company's central office as opposed to the customer's premises

Front 33

Digital

Back 33

Informaiton represented as a sequence of discrete symbols from a finite "alphabet" Examples are: text, numerical data and binary data.
Information rate and the capacity of a digital channel are measured in bits per second (bps)

Front 34

Analog

Back 34

Information is a continuous signal (for example a voltage) that can take on a continuum of values. Example: electrical signal coming out of a microphone when someone speaks into it.
The analog electrical signal represents the continuous acoustic changes in air pressure that make up sound.

Front 35

To get a good representation of sound in digital format, we need to ___________ its amplitude at a rate (samples per second (smp/s)) equal to at least twice the maximum frequency of the analog signal.

Back 35

Sample

Front 36

Quantization

Back 36

Process where after sampling , the signal amplitudes must be put in digital form

Front 37

Private Branch Exchange (PBX)

Back 37

an on-premise switching facility, owned or leased by an organization, that interconnects the telephones within the facility and provides access to the public telephone system.

Front 38

Text

Back 38

A familiar example of digital data

Front 39

International Reference Alphabet (IRA)

Back 39

the most commonly used text code. Each character in this code is represented by a unique 7-bit pattern; 128 different characters can be represented. Almost always stored and transmitted using 8 bits per character.

Front 40

Parity - in IRA

Back 40

Eighth bit in an IRA character used for error detection. The bit is set so that the total number of binary 1s in each octet is always odd (odd parity), or always even (even parity). A transmission error that changes a single bit, or any odd number of bits can be detected.

Front 41

Lossy Compression

Back 41

barely perceivable loss of information, may reduce the data by factors of roughly 10:1 to 20:1

Front 42

Lossless compression

Back 42

No loss of information is acceptable in compression, ratios run below 5:1 Example: Medical Imaging

Front 43

Vector Graphics

Back 43

image is represented as a collection of straight and curved line segments. Simple objects, such as rectangles and ovals, and more complex objects are defined by the grouping of line segments.

Front 44

Raster Graphics

Back 44

Image is represented as a two-dimensional array of spots, called pixels. Each pixel is either black or white.
Used for computer image processing and fax.

Front 45

Grayscale Image

Back 45

produced if each pixel is defined by more than one bit, representing shades of gray.

Front 46

JPEG

Back 46

Most widely used format for raster-scan images. (Joint Photographic Experts Group) A set of standards for the compression off raster-scan images, both grayscale and color. Appropriate for high-quality images(photos).

Front 47

GIF

Back 47

Another format seen on the web (Graphics Interchange Format). An 8-bit color format that can display up to 256 colors and is generally useful for non-photographic images with a fairly narrow range of color. i.e., Company Logo. Originated by Compuserve, principal application/usage: flat-color graphics, animation.

Front 48

PDF

Back 48

(Portable Document Format) suitable for documents that include text and images, widely used on the web and readers are available for virtually all OS's free.

Front 49

Postscript

Back 49

Page description language that is built into many desktop printers and virtually all high-end printing systems.

Front 50

Networking Implications of Images

Back 50

A tremendous number of bits is needed for representation in the computer, can be reduced by compression techniques. Even with compression the number of bits to be transmitted for image information is large. Two concerns - response time and throughput.

Front 51

Video

Back 51

Service that carries sequences of pictures in time.Makes use of a sequence of raster-scan images, can be thought of as a time-varying analog signal.
To produce a picture on a screen, an electron beam scans across the surface of the screen from left to right and top to bottom. To achieve adequate resolution, the beam produces a total of 483 horizontal lines at a rate of 30 complete scans of the screen per second.

Front 52

Interlacing

Back 52

Technique used to provide flicker-free image without increasing the bandwidth requirement - the odd numbered scan lines and the even numbered scan lines are scanned separately, with odd and even fields alternating on successive scans.

Front 53

Digital Video

Back 53

the capture, manipulation and storage of video in digital formats. Take a series of digital photographs at a rate of at least 30 frames per second.

Front 54

______________ scan is used for computer monitors and most HDTV schemes

Back 54

Progressive

Front 55

TVoIP

Back 55

transmission of video over IP-based networks, including the internet and private intranets, known as video streaming.

Front 56

Response Time

Back 56

the time it takes a system to react to a given input. Or, the time it takes for the system to respond to a request to perform a particular task. Shorter response time imposes greater cost.

Front 57

Computer Processing Power

Back 57

The faster the computer, the shorter the response time. Increased processing power means increased cost.

Front 58

Competing Requirements

Back 58

Providing rapid response time to some processes may penalize other processes.

Front 59

Response time ranges:

Back 59

Greater than 15 seconds: rules out conversational interaction
Greater than 4 seconds: generally too long for a conversation requiring the operator to retain information in operator's short-term memory.
2 to 4 seconds: delay longer than 2 seconds can be inhibiting to terminal operations demanding a high level of concentration
Less than 2 seconds: the more detailed the information remembered, the greater the need for responses of less than 2 seconds.
Sub-second response time: certain types of thought-intensive work, especially with graphics applications, require very short response times to maintain the user's interest and attention for long periods of time.
Decisecond response time: response to pressing a key and seeing the character displayed on the screen or clicking a screen object with a mouse needs to be almost instantaneous

Front 60

When a computer and a user interact at a pace that ensures that neither has to wait on the other, _____________ increases significantly.

Back 60

Productivity

Front 61

User Response Time

Back 61

The time span between the moment a user receives a complete reply to one command and enters the next command. (Think-Time)

Front 62

System Response Time

Back 62

The time span between the moment the user enters a command and the moment a complete response is displayed on the terminal

Front 63

Web systems with a ________________ or better response time maintain a high level of user attention.

Back 63

3-second

Front 64

Web systems with a response time between ___________ result in loss of some user concentration.

Back 64

3 and 10 seconds

Front 65

Web systems with a response time above ___________ discourage the user, who may simply abort the session.

Back 65

10-seconds

Front 66

Characteristics that change audio file sizes

Back 66

length, sampling rate and bits per sample

Front 67

____________________ describes the number of times per second an image is sent and this value can drastically change the file size or bandwidth required for transmission.

Back 67

Frame Rate

Front 68

Downside of modifying an image or stream in order to reduce the size

Back 68

you usually sacrifice some amount of quality.

Front 69

Voice

Back 69

audio service support applications based on sound, usually of the human voice - primarily telephone, other applications: telemarketing, voice mail, audio teleconferencing and entertainment radio.

Front 70

What are the two different interpretations of the prefixes kilo, mega and giga?

Back 70

Literally taken, the prefixes kilo, mega, and giga mean 1,000, 1,000,000, and 1,000,000,000 respectively. However, due to the way computers work (and this is a gross simplification) one kilobyte actually equals 1024 bytes, a meg is 1,048,576, and a gig is 1,073,741,824.

Front 71

What is the bandwidth of telephone voice?

Back 71

3400 Hz of bandwidth = moderate quality

Front 72

The process that takes advantage of redundancy to reduce the number of bits sent for a given piece of data is called what?

Back 72

Compression

Front 73

What is the difference between Centrex and PBX?

Back 73

PBX provides a on-premise switching facility that interconnects the telephones within the facility and provides access to the public telephone system, Centrex performs the switching function in equipment located in the telephone company's central office.

Front 74

What is the difference between a printable character and a control character?

Back 74

A printable character is able to be printed as output, a control character is not printable and is used for things such as error detection and function control.

Front 75

Explain the basic principles of vector graphics and raster graphics.

Back 75

Vector graphics represents images as curved and straight line segments which can be grouped together to form complex shapes, use binary codes to represent details of image - size, type and orientation - later used to be transmitted digitally. Raster graphics = images as pixels, which are two-dimensional array of black and white spots. The most used form of raster graphics is faxes.

Front 76

List two common image formats

Back 76

JPEG - good for photos
GIF - good for web-based graphics and animations

Front 77

List two common image formats.

Back 77

PDF - good for text and graphics
Postscript - page description language - desktop printers and all high-end printing systems.

Front 78

Describe the process used to prevent flicker in a video screen.

Back 78

Prevention of flickering is done by Interlacing - process that involves scanning odd-numbered lines and even-number lines separately in order to refresh the screen 60 times per second instead of 30 times per second, also prevents having to increase bandwidth.

Front 79

Define Response Time.

Back 79

The time it takes a system to react to a given input. Or, the time it takes for the system to respond to a request to perform a particular task.
User response time: the time span between the moment a user receives a complete reply to one command and enters the next command (think time)
System response time: time span between the moment the user enters a command and the moment a complete response is displayed on the terminal.

Front 80

What is considered an acceptable system response time for interactive applications and how does this response time relate to acceptable response times for Web sites?

Back 80

Less than two seconds would be an acceptable system response time for interactive applications. the more detailed the information remembered, the greater the need for responses of less than 2 seconds. Web Systems with a 3--second or better response time maintain a high level of user attention.

Front 81

Centralized Data Processing

Back 81

Architecture where the data processing support is provided by one or a cluster of computers, generally large computers, located in a central data processing facility. i.e., payroll application

Front 82

Centralized Computers

Back 82

one or more computers are located in a central facility

Front 83

Centralized Processing

Back 83

All applications are run on the central data processing facility

Front 84

Centralized Data

Back 84

Most data are stored in files and databases at the central facility and are controlled by and accessible by the central computer or computers.

Front 85

Centralized Control

Back 85

A data processing or information systems manager has responsibility for the centralized data processing facility

Front 86

Centralized Support Staff

Back 86

A centralized data processing facility must include a technical support staff to operate and maintain the data processing equipment. Programming is usually done by a central staff.

Front 87

Distributed Data Processing (DDP)

Back 87

Computers, usually smaller computers, are dispersed throughout an organization, some form of interconnection is usually needed. Provides great flexibility. Data/applications are maintained on individual servers that are not tied to a centralized computer room but can be sited at the most convenient location. All servers have wireless access to the network. Network management and security are easier to manage.

Front 88

Vertical Partitioning

Back 88

Data processing is distributed in a hierarchical fashion which may reflect the organizational structure or simply be the most appropriate for the application.
Involves one application split up into components that are dispersed among a number of machines.

Front 89

Horizontal Partitioning

Back 89

Data processing is distributed among a number of computers that have a peer relationship - no concept of client/server. Normally operate autonomously - configuration sometimes used for load balancing. Usually reflects organizational decentralization. Involves either one application replicated on a number of machines or a number of different applications distributed among a number of machines.

Front 90

Office Automation Support System

Back 90

Staff and personnel are equipped with personal computers linked together by a network. Each PC contains software packages useful to that user. Systems are linked together so that users may exchange messages, files and other information.
An example of Horizontal Partitioning.

Front 91

Distributed Devices

Back 91

a distributed set of devices that can be controlled by processors. i.e., ATMs, lab interface equipment, factory automation. Involves the distribution of processing technology to the various locations of the manufacturing process.

Front 92

Network Management

Back 92

Any distributed system requires some form of management and control - including control of access to some of the facilities in the system, monitoring of the status of various components, and management of the communications facility to ensure availability and responsiveness. Each computer in the system must include some management and control logic to be able to interact with the central network management system.

Front 93

Database

Back 93

A structured collection of data stored for use in one or more applications. Contains the relationships between data items and groups of data items.

Front 94

Database Management System (DBMS)

Back 94

A suite of programs for constructing and maintaining the database and for offering ad hoc query facilities to multiple users and applications.

Front 95

Query Language

Back 95

Provides a uniform interface tot he database for users and applications.

Front 96

Data Definition Language (DDL)

Back 96

language used to define the database logical structure and procedural properties, represented by a set of database description tables.

Front 97

Data Manipulation Language (DML)

Back 97

language that provides a powerful set of tools for application developers.

Front 98

Distributed database

Back 98

Collection of several different databases, distributed among multiple computers, that looks like a single database to the user. The DBMS controls access to the distributed database and enables the user to treat the distributed database as a single database.

Front 99

Centralized Database

Back 99

Database housed in a central computer facility. Often used with a vertical DDP organization. Desirable when the security and integrity of the data are paramount because the central facility is more easily controlled than a dispersed collection of data.

Front 100

Replicated Database

Back 100

an overall strategy for data distribution. all or part of the database is copied at two or more computers.l

Front 101

Client/Server Architecture

Back 101

Users work on powerful workstations or PCs which supports the end-user programming, provides the ability to use off=the-shelf software, and gives the immediate response inherent in distributed architecture. The clients, are supported by specialized servers. - which provide database services, printing and fax services, files storage, and communication front ends, gateways and bridges. (LANs)

Front 102

Connectivity

Back 102

The ability of components in the system to exchange data.
Vertically partitioned DDP system - components generally need links only to components above and below them in the hierarchical structure. (more links are required than connections.)
Horizontally partitioned systems may need to allow data exchange between any two systems.

Front 103

Performance

Back 103

Assessment of the system and the applications it supports.

Front 104

Availability

Back 104

refers to the percentage of time that a particular function or application is available for users.

Front 105

Extranet

Back 105

Makes use of TCP/IP protocols and applications - especially the web. Provides access to corporate resources by outside clients - suppliers and customers or home-based workers, via the internet or through other data communications networks (portals).

Front 106

Intranet

Back 106

provides users the features and applications of the Internet but isolated within the organization.

Front 107

Intranet Features

Back 107

* Uses Internet-based standards
* Uses the TCP/IP protocol suite for local and WAN
* Comprises wholly owned content not accessible to the public
* can be managed

Front 108

DDP System

Back 108

A computing facility in which computers are dispersed within an organization with some means of interconnection among them. Implemented in a wide variety of forms. Functions/Objects supported:
* Applications
* Device controllers
* Control
* Data

Front 109

What are some functions that are centralized in a fully centralized data processing facility?

Back 109

Processing - all applications are run on the central data processing facility - mainframe or server
Data - most data are stored in files and databases at the central facility and are controlled by and accessible by the central computer or computers
Control - A data processing or information systems manager has responsibility for the centralized data processing facility
Support Staff - technical support staff to operate and maintain the data processing equipment/software

Front 110

What are some advantages of a centralized processing facility?

Back 110

Economies of scale
Can afford to have professional programmers on staff to meed the needs of the various departments.
Management can maintain control over data processing procurement, enforce standards for programming and data file structure and design and implement a security policy.

Front 111

Based on your reading of the chapter, name five components that might be part of a fully centralized system.

Back 111

Centralized computers
Centralized processing
Centralized data
Centralized control
Centralized support staff

Front 112

What is a distributed data processing (DDP) strategy?

Back 112

Computers are dispersed throughout an organization, the objective is to process information in a way that is most effective based on operational, economic, and/or geographic considerations (or all three). Some form of interconnection is usually needed. Allows greater flexibility in structure and more autonomy, but creates more redundancy .

Front 113

Applications for the distributed environment are available much sooner than those in the centralized environment. What are the main sources of these applications?

Back 113

Off-The-Shelf Applications - readily available (no backlog) and don't need to worry about communicating requirements from users to professional programmers.

Front 114

Real-Time Replication

Back 114

Immediately synchronized data/database

Front 115

Near-Real-Time Replication

Back 115

(more common) Backups occur in batches with a small amount of lag time (e.g., 30 minutes)

Front 116

Deferred Replication

Back 116

involves bulk transfer of a large number of changes at infrequent intervals, such as once or twice a day. Minimizes network resource requirements but does not provide current data.

Front 117

Describe three ways that an application can be allocated in a distributed environment. (Forms of Distributed Applications)

Back 117

* Split up into components that are dispersed among a number of machines
* One application replicated on a number of machines
* A number of different applications distributed among a number of machines.

Front 118

What major problems for the data processing manager result from distributed small systems?

Back 118

Lack of centralized processing may result in the loss of centralized control.
Individual departments may adopt incompatible systems, making interdepartmental cooperation difficult.
Procurement decisions may be made without systematic forecasts of requirements and cost and with no enforcement of standards for hardware, software, or departmental programming practices.
Increases the difficulty of obtaining data for use by top management, makes uniform collection of data for upward reporting more difficult.

Front 119

What are some reasons for wanting to interconnect distributed data processing systems?

Back 119

Responsiveness
Availability
Correspondence to Organizational Patterns
Resource Sharing
Incremental Growth
Increased User Involvement and Control
Decentralized Operation and Centralized Control
End-User Productivity
Distance and Location Independence
Privacy and Security
Vendor Independence
Flexibility

Front 120

Distinguish between horizontal and vertical partitioning of applications.

Back 120

Vertical partitioning involves one application split up into components that are dispersed among a number of machines - objective is to assign processing load to the level of the hierarchy at which it is most cost-effective.
Horizontal partitioning involves either one application replicated on a number of machines, or a number of different applications distributed among a number of machines - data processing is distributed among a number of computers that have a peer relationship - no concept of client/server.

Front 121

Why would a company want a distributed database?

Back 121

Distributed databases provide local autonomy by giving each department control over its data. Departments have a sense of ownership over their data.A distributed database architecture adapts more easily to changes in the organizational structure. When organizations add new locations or takeover independent entities, distributed databases allow for a smoother transition. More Flexible - local units retain some control over how data's organized and accessed. Units can change data format to accommodate unique geographical or departmental needs.

Front 122

In designing a distributed database, database objectives and communications objectives are not always the same. Distinguish between the two sets of objectives.

Back 122

Database objectives include accessibility of the data, security and privacy and completeness and integrity of the data - more concerned with access, availability and integrity. Communications objectives are to minimize the communications load and the delays imposed by the use of communications facilities - more concerned with load balancing and communications cost.

Front 123

How does a factory often reflect the use of distributed devices?

Back 123

Each major operational area is controlled by a work-station, which is fed information from individual process-control micro-processors. Distributed workstations ensure rapid response to conditions at the process level. All the workstations are linked to a higher-level computer concerned with operations planning, optimization, provision of management information, and general corporate data processing.

Front 124

Name three types of communications and networking requirements generated by the use of distributed data processing.

Back 124

Connectivity
Availability
Performance

Front 125

Why do we still need mainframe computers even though personal computers and workstations have become so much more powerful?

Back 125

These computers are capable of completing multiple tasks at the same time, taking commands from multiple users. They are capable of handling literally thousands of users at once.

Front 126

The Two primary paradigms for electronic communications were _______________ switching and ____________ switching.

Back 126

Circuit Switching - voice communications
Packet Switching - telegraph and telex

Front 127

Message Switching

Back 127

Messages are sent from A to B in stages. The transmission facility might be seized and the message is transmitted from A to C where it is temporarily stored and the transmission channel was released. Then the message would be transmitted to E where the process continues until the message is finally delivered to its destination.

Front 128

Packet Switching

Back 128

A special case of message switching with substantially different properties. Message packets are limited in length, and if necessary broken into a number of packets. the Packets are transmitted from switch to switch and stored in RAM instead of slower peripherals ordinarily used.

Front 129

Telnet

Back 129

Early application developed for the ARPANET that provided a universal language for remote computer terminals. The application provided a common denominator terminal. If software was written for each type of computer to support the "Telnet terminal" then one terminal could interact with all computer types.

Front 130

File Transfer Protocol (FTP)

Back 130

Similar open functionality (to Telnet) that allows the transparent transfer of files from one computer to another over the network.

Front 131

Domain Name System (DNS)

Back 131

invented so hosts could be assigned names that were easier to remember with DNS providing a translation from the domain names to numeric addresses. New routing algorithms were also invented to handle the ever-increasing complexity of the many connected networks.

Front 132

Purpose of the Internet

Back 132

to interconnect end systems called hosts.

Front 133

IP Datagrams/Packets

Back 133

sequenced packets of data sent via Internet

Front 134

IP Address

Back 134

a unique numeric address of a host or destination host
Has two components: a network number which identifies a network on the Internet, and a host address, which identifies a unique host on that network.

Front 135

NSF

Back 135

Foundation responsible form many of the policy decisions that led to the modern Internet.Primary goal was to establish a wide area networking infrastructure that was not directly funded by the federal government. Also helped standardize the use of many technologies such as TCP/IP.

Front 136

Routers

Back 136

A device that connects two networks and whose primary function is to relay data from one network to the other on a route from the source to the destination end system. Internet Gateways, ensure interoperability between the pieces of the Internet.

Front 137

World Wide Web (www)

Back 137

a distributed hypermedia technology that facilitates the international exchange of products, research findings and information.

Front 138

HyperText Markup Language (HTML)

Back 138

standard which defines embedded commands in text files that specify features of the browser display such as fonts, colors, images and their placement on the display, and the location of the locations where the user can invoke the hyperlinks and their targets.

Front 139

Hypertext Transfer Protocol (HTTP)

Back 139

a communications protocol for use in TCP/IP networks for fetching the files from the appropriate servers as specified by the hyperlinks.

Front 140

Host

Back 140

Any end system, such as a PC, workstation, or server, that connects to the Internet.

Front 141

Customer Premises Equipment (CPE)

Back 141

the telecommunications equipment located onsite with the host.

Front 142

Point of Presence (POP)

Back 142

site that has a collection of telecommmunications equipment; usually refers to an ISP or telephone company sites.

Front 143

Internet Service Provider (ISP)

Back 143

company that provides other companies or individuals with access to, or presence on, the Internet

Front 144

Network Access Point (NAP)

Back 144

one of several major Internet interconnection points that serve to tie all the ISPs together. Provide major switching facilities that serve the public in general.
A Physical facility that provides the infrastructure to move data between connected networks - built and operated by the private sector.
Infrastructure that provides the physical access paths between routers.

Front 145

Network Service Provider (NSP)

Back 145

company that provides backbone services to an ISP. Typically, an ISP connects at a point called an Internet Exchange (IX) to a regional ISP that in turn connects to an NSP backbone.
Company that provides Equipment responsible for routing.

Front 146

ISP POP

Back 146

the edge of the ISP's network; connections from users are accepted and authenticated here. an ISP may operate several POPs distributed throughout its area of operation

Front 147

Local Loop (Last Mile)

Back 147

the infrastructure between a provider's installation and the site where the host is located.
A transmission path, generally twisted pair, between the individual subscriber and the nearest switching center of a public telecommunications network.

Front 148

Domain

Back 148

a group of hosts that are under the administrative control of a single entity, such as a company or government agency - organized hierarchically
i.e., com, org, net, us, uk, ...

Front 149

Domain namespace

Back 149

naming system on which DNS is based is a hierarchical and logical tree structure used to identify resources on the Internet

Front 150

DNS Database

Back 150

The collection of all RRs is organized into a distributed database. Conceptually, each node and leaf in the name space tree structure names a set of information that is contained in resource record (RRs) that include the name, IP address and other information about hosts.

Front 151

Name Servers

Back 151

Server Programs that hold information about a portion of the domain name tree structure and the associated RRs.

Front 152

Resolvers

Back 152

Programs that extract information from name servers in response to client requests.
A typical request is for an IP address corresponding to a given domain name.

Front 153

Key Features of the DNS database

Back 153

Variable-depth hierarchy for names: allows essentially unlimited levels and uses the period as the level delimiter in printed names
Distributed Database: the database resides in DNS servers scattered throughout the Internet.
Distribution controlled by the database: the DNS database is divided into thousands of separately managed zones, which are managed by separate administrators. Distribution and update of records is controlled by the database software.

Front 154

DNS Operation Steps

Back 154

1. User program requests an IP address for a domain name.
2. Resolver module in the local host or local ISP queries a local name server in the same domain as the resolver.
3. Local name server checks to see if the name is in its local database or cache, and if so returns the IP address to the requestor. Otherwise, the name server queries other available name servers, if necessary going to the root server.
4. When response is received at the local name server, it stores the name/address mapping in its local cache and may maintain this entry for the amount of time specified in the time to live field of the retrieved RR
5. The user program is given the IP address or an error message.

Front 155

Zone

Back 155

Collection of one or more (or all) subdomains within a domain, along with the associated RRS. Authoritative set of data because the name server is responsible for maintaining an accurate set of RRs for the portion of the domain name space.

Front 156

Root Name Servers

Back 156

Top of the server hierarchy, servers that share responsibility for the top-level zones.

Front 157

Two Methods by which queries are forwarded and results returned in a query.

Back 157

1. Query another name server for the desired result and then send the result back to the resolver - recursive technique.
2. Return to the resolver the address of the next server to whom the request should be sent - iterative technique.
Operationally, when the DNS system receives a request for name resolution, the closest server attempts to provide the answer, if that server does not know the answer, the request is passed upward and a server with the answer responds.

Front 158

ARPANET

Back 158

Developed in 1969, the first operational packet-switching network which began operations in four locations.

Front 159

Central Office

Back 159

the place where telephone companies terminate customer lines and locate switching equipment to interconnect those lines with other networks

Front 160

Internet Protocol (IP)

Back 160

standardized protocol that executes in hosts and routers to interconnect a number of independent networks.
Implemented in all end systems and routers; and acts as a relay to move a block of data from one host, through one or more routers, to another host.

Front 161

Transmission Control Protocol (TCP)

Back 161

Provides reliable, ordered, error-checked delivery of a stream of octets between programs running on computers connected to an intranet or the public Internet. Used to accurately deliver email and transfer files from one location to another. Implemented only in the end systems and keeps track of the blocks of data being transferred to assure that all are delivered reliably to the appropriate application.

Front 162

What is the difference between and the Internet?

Back 162

ARPANET was a network that that used packet-switching to communicate with it's hosts. The Internet is a technique/protocol for interconnecting networks.

Front 163

What two protocols form the foundation of and govern the way we communicate on the Internet?

Back 163

TCP - Transmission Control Protocol
IP - Internet Protocol

Front 164

What were two of the first applications developed for use over a network?

Back 164

Telnet - provided a universal language for remote computer terminals, and FTP (File Transfer Protocol) allowed the transparent transfer of files from one computer to another over the network.

Front 165

What is Mosaic?

Back 165

the first graphically oriented browser

Front 166

What are two applications programs that have taken the place of Mosaic?

Back 166

Netscape Navigator & Internet Explorer

Front 167

What is the programming language used to display Web pages?

Back 167

HTML - HyperText Markup Language

Front 168

What is the difference between an ISP and a POP?

Back 168

ISP is a company that provides other companies or individuals with access to, or presence on, the Internet.
POP is the site that has a collection of telecommmunications equipment.

Front 169

What is the difference between an NAP and an NSP?

Back 169

NAP is the physical facility/Infrastructure that provides the physical access paths between routers.
NSP is the Company that provides Equipment responsible for routing.

Front 170

What is an Internet Domain?

Back 170

a group of hosts that are under the administrative control of a single entity, i.e., com, net, gov

Front 171

What is a DNS?

Back 171

Domain Name System, directory lookup service that provides a mapping between the name of a host on the internet and its numerical address.

Front 172

Name the four major components of the domain name system.

Back 172

Domain name space
DNS database
Name servers
Resolvers

Front 173

What is the difference between a name server and a resolver in DNS

Back 173

Name Servers are programs that hold information about a portion of the domain name tree structure and the associated RRs. A Resolver is a program that extracts that information in response to client requests.

Front 174

What is a DNS Resource Record?

Back 174

record that includes the Name, IP Address and other information about hosts

Front 175

Protocol Architecture

Back 175

Software structure that implements the communications function - typically consists of a layered set of protocols with one or more protocols at each layer.

Front 176

Open Systems Interconnection (OSI)

Back 176

a seven-layer communication model for a computer protocol architecture and a framework for developing protocol standards, communications functions are partitioned into a hierarchical set of layers.

Front 177

TCP/IP Protocol

Back 177

a standardized communications protocol with a number of relatively independent layers, common layers include: Application, Host-to-host (transport layer), Internet layer, Network Access layer, and Physical layer.

Front 178

Application Layer

Back 178

the sending application generates a block of data and passes this to the transport layer.

Front 179

Transport Layer

Back 179

appends a transport header containing protocol control information and then hands each segment over to the network layer with transmission instructions fro the destination computer

Front 180

Network Layer/ Network Access Layer

Back 180

accepts the network packet, appends a network access header and presents the data to the network with a request for transmission - requires the use of control information

Front 181

Internet Layer

Back 181

when 2 devices are attached to different networks, procedures are used to allow data to traverse multiple interconnected networks IP - Internet Protocol used at this layer to provide the routing function across multiple networks

Front 182

Physical Layer

Back 182

Layer 1 of the OSI model, concerned with the electrical, mechanical, and timing aspects of signal transmission over a medium.
Covers the physical interface between a data transmission device and a transmission medium or network - concerned with specifying the characteristics of the transmission medium, the nature of the signals, the data rate and related matters.

Front 183

UDP

Back 183

transport-level protocol that is in common use as a part of the TCP/IP protocol suite. Does not guarantee delivery, preservation of sequence or protection against duplication. UDP enables a process to send messages to other processes with a minimum of protocol mechanism.
Essentially adds a port addressing capability to IP

Front 184

IPv6

Back 184

standard for a next-generation IP, designed to accommodate the higher speeds of today's networks and the mix of data streams including graphic and video that are becoming more prevalent. Driving force was the need for more addresses

Front 185

Simple Mail Transfer Protocol (SMTP)

Back 185

Supports a basic electronic mail facility by providing a mechanism for transferring message among separate hosts. Features include mailing lists, return receipts, and forwarding.

Front 186

SSH (Secure Shell)

Back 186

provides a secure remote logon capability which enables a user at a terminal or PC to logon to a remote computer and function as if directly connected to that computer. Also supports file transfer between the local host and a remote server. Enables the user and the remote server to authenticate each other, encrypts all traffic in both directions - carried on a TCP connection.;

Front 187

Subnetwork

Back 187

a logically visible subdivision of an IP network; constituent network

Front 188

Intranet

Back 188

Private Internets within Organizations that provide the key internet applications .

Front 189

End Systems (ESs)

Back 189

the devices connected to the subnetwork.

Front 190

Intermediate Systems (ISs)

Back 190

subnetworks connected by devices that provide a communications path and perform the necessary relaying and routing functions so that data can be exchanged between devices attached to different subnetworks in the internet.

Front 191

Two types of ISs

Back 191

Bridges
Routers

Front 192

Communication Network

Back 192

a facility that provides a data transfer service among devices attached to the network.

Front 193

Checksum

Back 193

an error-detecting code based on a summation operation performed on the bits to be checked.

Front 194

Frame Check Sequence (FCS)

Back 194

an error-detecting code inserted as a field in a block of data to be transmitted. The code serves to check for errors upon reception of the data.

Front 195

Header

Back 195

system defined control information that precedes user data in a protocol data unit

Front 196

IPv4

Back 196

a connectionless protocol for use on packet-switched Link Layer networks (e.g., Ethernet). It operates on a best effort delivery model, in that it does not guarantee delivery, nor does it assure proper sequencing or avoidance of duplicate delivery. These aspects, including data integrity, are addressed by an upper layer transport protocol, such as the Transmission Control Protocol (TCP).

Front 197

Internet

Back 197

A worldwide internetwork based on TCP/IP that interconnects thousands of public and private networks and millions of users.

Front 198

OSI Architecture

Back 198

Application
Presentation
Session
Transport
Network
Data link
Physical

Front 199

TCP/IP Architecture

Back 199

Application
Transport (Host-to-Host)
Internet
Network Access
Physical

Front 200

Packet

Back 200

A group of bits that includes data plus control information. Generally refers to a network layer (OSI layer 3) protocol data unit.

Front 201

Port

Back 201

A transport-layer address that identifies a user of a transport-layer protocol.

Front 202

Protocol

Back 202

A set of semantic and syntactic rules that describe how to transmit data, especially across a network. Low level protocols - define the electrical and physical standards. High-level protocols - deal with the data formatting

Front 203

Protocol Architecture

Back 203

The software structure that implements the communications function. Typically consists of a layered set of protocols, with one or more protocols at each layer.

Front 204

Protocol Data Unit (PDU)

Back 204

Information that is delivered as a unit between peer entities of a network. Typically contains control information and address information in a header. May also contain data.

Front 205

What is the major function of the network access layer?

Back 205

routing the data to the appropriate destination using the address of the destination computer that is provided by the sending computer.

Front 206

There are several protocol models that have bee developed. Examples: SNA, Appletalk, OSI and TCP/IP as well as more general models such as three-layer models. What model is actually used for communications that travel over the Internet?

Back 206

TCP/IP architecture is configured for communications.

Front 207

Virtual Private Network (VPN)

Back 207

consists of a set of computers that interconnect by means of a relatively unsecure network and that make use of encryption and special protocols to provide security.

Front 208

IPSec

Back 208

a set of Internet standards that provides the capability to secure communications across a LAN, across private and public WANs and across the Internet

Front 209

What are some advantages of layering as seen in the TCP/IP architecture?

Back 209

A layered architecture s particularly well suited to the development of standards.
Breaks down the work to make it more manageable.
Speeds up the standards-development process.

Front 210

Which version of IP is the most prevalent today?

Back 210

IPv4

Front 211

Does all traffic running on the Internet use TCP?

Back 211

No, there is FTP, Telnet,SMTP,UDP etc.

Front 212

Compare the address space between IPv4 and IPv6. How many bits are used in each?

Back 212

IPv4 is 32 bits and can support up to 232 addresses; IPv6 is 128 bits, can support up to 2128 addresses to fulfill future needs with better security and network related features

Front 213

Does a router require that all attached layer 2 protocols are the same?

Back 213

No .

Front 214

Client Machines

Back 214

Typically single-user PCs or workstations that provide a highly user-friendly interface to the end user.

Front 215

Middleware

Back 215

A set of drivers, APIs or other software that improves connectivity between a client application and a server

Front 216

Relational Database

Back 216

A database in which information access is limited to the selection of rows that satisfy all search criteria.

Front 217

Server

Back 217

A computer, usually a high-powered workstation or a mainframe, that houses information for manipulation by networked clients.

Front 218

Structured Query Language (SQL)

Back 218

A language developed by IBM and standardized by ANSI for addressing, creating, updating, or querying relational databases.

Front 219

The most common type of server is a _______________ server, usually controlling a ________________ ______________.

Back 219

Database
Relational Database

Front 220

The third essential ingredient of the client/server environment is the ________________.

Back 220

Network

Front 221

Client/server computing is _____________ computing

Back 221

Distributed

Front 222

Characteristics that make client/server distinct from ordinary distributed processing:

Back 222

* heavy reliance on bringing user-friendly applications to the user on their system
* there is an emphasis on centralizing corporate databases and many network management and utility functions.
* There is an emphasis on open and modular systems (user has greater choice in selecting products and in mixing equipment from different vendors)
* Networking is fundamental to the operation

Front 223

What are two significant trends in industry that illustrate the success of client/server computing:

Back 223

1. The permanent shedding of jobs by companies in an effort to downsize and streamline for success in a fiercely competitive market.
2. Substantial increases in investment in computers and other information technology in an effort to compensate for a smaller employee base.

Front 224

The central feature of a client/server architecture is:

Back 224

the allocation of application-level tasks between clients and servers

Front 225

____________ _____________ enables the client and server to interoperate.

Back 225

Communications software
i.e., TCP/IP

Front 226

Graphical User Interface (GUI)

Back 226

a presentation service module in the client workstation that is responsible for providing a user-friendly interface to the distributed applications available in the environment.

Front 227

Application Logic

Back 227

the software for data analysis that interacts with the database.
i.e., SQL

Front 228

What are the four reasons that dictate the way the division of data and application processing:

Back 228

1. the nature of the database information
2. the types of applications supported
3. the availability of interoperable vendor equipment
4. the usage patterns within an organization

Front 229

Host Based Processing

Back 229

not true client/server computing; refers to the traditional mainframe environment in which all or virtually all of the processing is done on a central host.

Front 230

Server-based processing

Back 230

simplest class of client;/server configuration; the client is principally responsible for providing a graphical interface, while virtually all of the processing is done on the server.

Front 231

Client-Based Processing

Back 231

Virtually all application processing may be done at the client, with the exception of data validation routines and other database logic functions that are best performed at the server level.

Front 232

Cooperative Processing

Back 232

the application processing is performed in an optimized fashion, taking advantage of the strengths of both client and server machines and of the distribution of data. More complex to set up and maintain but offers greater user productivity gains and greater network efficiency

Front 233

Thick Client

Back 233

Presentation logic , Application logic and Database logic are performed at the client level, Database logic and DBMS are performed at the server level

Front 234

Thin Client

Back 234

Presentation logic is at the client level, Application Logic, Database logic and DBMS are at the server level.

Front 235

Three Tier Client/Server Approach

Back 235

Application software is distributed among three types of machines: a user machine, a middle-tier server and a backend server. (typically a thin-client setup)

Front 236

Middleware

Back 236

standard programming interfaces and protocols that sit between the application above and communications software and operating system below. Hides the complexities and disparities of different network protocols and operating systems.

Front 237

Purpose of Middleware

Back 237

Enables an application or user at a client to access a variety of services on servers without being concerned about differences among servers.

Front 238

Application Programming Interface (API)

Back 238

the middleware which cuts across all client and server platforms, is responsible for routing client requests to the appropriate server

Front 239

What are the three underlying mechanisms of middleware:

Back 239

message passing
remote procedure calls
object-oriented mechanisms

Front 240

Message Passing

Back 240

distributed message passing to implement client/server functionality. Client process requires some service (e.g., read a file, print) and sends a message containing a request for service to a server process. Server process honors the request and sends a message containing a reply. Simplest Form: Send and Receive

Front 241

Send Function

Back 241

Specifies a destination and includes the message content.

Front 242

Receive Function

Back 242

tells from whom a message is desired (including "all") and provides a buffer where the incoming message is to be stored.

Front 243

Remote Procedure Call

Back 243

a common method for encapsulating communication in a distributed system, Allows programs on different machines to interact using simple procedure call/return semantics, just as if the two programs were on the same machine. - used for access to remote services.

Front 244

Client/Server Binding

Back 244

specifies how the relationship between a remote procedure and the calling program will be established. A binding is formed when two applications have made a logical connection and are prepared to exchange commands and data.

Front 245

Nonpersistent Binding

Back 245

a logical connection is established between the two processes at the time of the remote procedure call and as soon as the values are returned, the connection is dismantled.

Front 246

Persistent Binding

Back 246

a connection that is set up for a remote procedure call is sustained after the procedure return and can then be used for future remote procedure calls. If a specified period of time passes with no activity on the connection, the connection is terminated.

Front 247

Object-Oriented Mechanisms

Back 247

Clients and servers ship messages back and forth between objects. Object communications may rely on an underlying message or RPC structure or be developed directly on top of object-oriented capabilities in the operating system.

Front 248

Intranet

Back 248

the implementation of Internet technologies within a corporate organization rather than for external connection to the global internet.

Front 249

Advantages of a Web/Database system compared to a more traditional database approach

Back 249

* Ease of administration.
* Deployment
* Development Speed
* Flexible Information Presentation

Front 250

Potential disadvantages of a Web/Database system

Back 250

* Functionality may be more limited
* Stateless Operation-the web server keeps no information between transactions to track the state of the user

Front 251

Problems associated with using traditional client/server systems

Back 251

* Long development cycles
* Difficulty of partitioning applications into client and server modules and the even greater difficulty of modifying the partition in response to user feedback
* Effort involved in distributing upgrades to clients
* Difficulty of scaling the servers to respond to increased load in a distributed environment
* Continuous requirement for increasingly powerful desktop machines.

Front 252

The most heavily used network application in the corporate world is:

Back 252

Electronic Mail

Front 253

Electronic Mailing List

Back 253

an alias that has multiple destinations, usually created to discuss specific topics. Each subscriber receives messages one at a time, as they are sent.

Front 254

Usenet

Back 254

Network News - a collection of electronic bulletin boards that work in much the same way as the Internet mailing lists. Messages are archived at each news site and organized by subject matter, discussions are threaded.

Front 255

Extranet

Back 255

Makes use of TCP/IP protocols and applications, especially the web, provides access to corporate resources by outside clients, typically suppliers and customers of the org. Can be through the internet or through other data communications networks, provides more extensive access to corporate resources - usually enforcing a security policy

Front 256

Service-Oriented Architecture

Back 256

a form of client/server architecture, organizes business functions into a modular structure rather than as monolithic applications for each department.Common functions can be used by different departments internally and by external business partners as well.

Front 257

_______________ interfaces are used to enable service modules to communicate with one another and to enable client applications to communicate with service modules.

Back 257

Standardized

Front 258

Service Provider

Back 258

A network node that provides a service interface for a software asset that manages a specific set of tasks.

Front 259

Service Requestor

Back 259

A network code that discovers and invokes other software services to provide a business solution.

Front 260

Service broker

Back 260

A specific kind of service provider interfaces and service locations, can pass on service requests to one or more additional service providers.

Front 261

Key Characteristics for effective use of services in a Service-Oriented Architecture:

Back 261

* Coarse-grained
* Interface-based design
* Discoverable
* Single Instance
* Loosely coupled
* Asynchronous

Front 262

Coarse-grained

Back 262

Operations on services are frequently implemented to encompass more functionality and operate on larger data sets

Front 263

Interface-Based Design

Back 263

Services implement separately defined interfaces, multiple services can implement a common interface and a service can implement multiple interfaces

Front 264

Discoverable

Back 264

Services need to be found at both design time and run time, not only by unique identity but also by interface identity and by service kind.

Front 265

Single Instance

Back 265

Each service is a single, always running instance that a number of clients communicate with.

Front 266

Loosely coupled

Back 266

Services are connected to other services and clients using standard, dependency-reducing, decoupled message-based methods such as XML document exchanges.

Front 267

Asynchronous

Back 267

services use an asynchronous message-passing approach - not required.

Front 268

Inventory Software

Back 268

an application that will run on the server or mainframe - user cannot work with these applications unless they are connected and possibly authenticated.

Front 269

Electronic Mail

Back 269

a facility that allows users at workstations and terminals to compose and exchange messages

Front 270

Mailbox

Back 270

an entity maintained buy the file management system and is in the nature of a file directory.

Front 271

User Agent (UA)

Back 271

functions that are visible to the e-mail user. Include facilities for preparing and submitting messages for routing to the destination(s), as well as utility functions to assist the user in filing, retrieving, replying, and forwarding

Front 272

Message Transfer Agent (MTA)

Back 272

accepts messages from the user agent for transmission across a network or internetwork, concerned with the protocol operation needed to transmit and deliver messages

Front 273

Post Office Protocol (POP3)

Back 273

allows an e-mail client (UA) to download an e-mail fro an e-mail server (MTA). POP3 UAs connect via TCP/IP to the server

Front 274

Internet Mail Access Protocol (IMAP)

Back 274

enables an e-mail client to access mail on an e-mail server - also uses TCP/IP with server TCP port 143. More complex than POP3 but provides stronger authentication and other functions not supported by POP3

Front 275

Simple Mail Transfer Protocol (SMTP)

Back 275

used for transfer of mail from a UA to an MTA and from one MTA to another

Front 276

Multipurpose Internet Mail Extensions (MIME)

Back 276

Supplements SMTP and allows the encapsulation of multimedia (nontext) messages inside of a standard SMTP message

Front 277

__________ is the standard protocol for transferring mail between hosts in the TCP/IP protocol suite (defined in RFC 821.

Back 277

SMTP

Front 278

SMTP is not concerned with the format or content of messages themselves, with two exceptions:

Back 278

1. SMTP standardizes the message character set as 7-bit ASCII
2. SMTP adds log information to the start of the delivered message that indicates the path the message took.

Front 279

Conceptual queued message has two parts:

Back 279

1. the message text consisting of
* the 822 header: constitutes the message envelope and includes an indication of the intended recipient(s)
* the body of the message composed by the user
2. A list of mail destinations.

Front 280

SMTP Sender

Back 280

takes messages from the outgoing mail queue and transmits them to the proper destination host via SMTP transactions over one or more TCP connections to port 25 on the target hosts.

Front 281

SMTP Protocol

Back 281

Used to transfer a message from the SMTP sender to the SMTP receiver over a TCP connection, attempts to provide reliable operation but does not guarantee recovery of lost messages. Generally considered reliable.

Front 282

SMTP ReceIver

Back 282

Accepts each arriving message and either places it in the appropriate user mailbox or copies it to the local outgoing mail queue if forwarding is required. Must be able to verify local mail destinations and deal with errors, including transmission errors and lack of disc file capacity.

Front 283

Connections Setup

Back 283

An SMTP sender will attempt to set up a TCP connection with a target host when it has one or more mail messages to deliver to that host.

Front 284

Connection Setup Sequence

Back 284

1. Sender opens a TCP connection with the receiver
2. Once the connection is established, receiver identifies itself with "220 Service Ready"
3. Sender identifies itself with the HELO command
4. Receiver accepts the sender's identification with "250 OK"
If mail services - destination is unavailable, destination host returns a "421 Service Not Available" reply and the process is terminated.

Front 285

Three Logical Phases of Mail Transfer

Back 285

1. A Mail command identifies the originator of the message
2. One or more RCPT commands identify the recipients for the message.
3. A Data command transfers the message text
If receiver is prepared to accept messages from originator, it returns a "250 OK" reply

Front 286

Mail Command

Back 286

gives the reverse path, which can be used to report errors.

Front 287

RCPT Command

Back 287

identifies an individual recipient of the mail data; multiple recipients are specified by multiple use of this command.

Front 288

Connection Closing

Back 288

SMTP sender closes the connection in two steps:
1. sender sends a Quit command and waits for a reply
2. initiate a TCP close operation for the TCP connection

Front 289

RFC 822

Back 289

Defines a format for text messages that are sent using e-mail. Adopted standard of the SMTP.
Messages are viewed as having an envelope and contents. The envelope contains whatever information is needed to accomplish transmission and delivery. The contents compose the object to be delivered to the recipient.

Front 290

Multipurpose Internet Mail Extensions (MIME)

Back 290

an extension to the RFC 822 framework that is intended to address some of the problems and limitations of the use of SMTP and RFC 822.

Front 291

MIME Specification includes these three elements:

Back 291

1. Five new message header fields which may be included in an RFC 822 header - provide information about the body of the message
2. Number of content formats are defined, standardizing representations that support multimedia e-mail.
3. Transfer encodings are defined that enable the conversion of any content format into a form that is protected from alteration by the mail system.

Front 292

MIME-Version

Back 292

First of the new header fields, must have the parameter value 1.0 which indicates the message conforms to the RFCs

Front 293

Content-Type

Back 293

Second of the new header fields, describes the data contained in the body with sufficient detail that the receiving user agent can pick an appropriate agent or mechanism to represent the data to the user or otherwise deal with the data in an appropriate manner

Front 294

Content-Transfer-Encoding

Back 294

Third of the new header fields, indicates the type of transformation that has been used to represent the body of the message in a way that is acceptable for mail transport.

Front 295

Content-ID

Back 295

Fourth of the new header fields, used to uniquely identify MIME entities in multiple contexts.

Front 296

Content-Description

Back 296

Fifth of the new header fields, a plain text description of the object with the body - useful when the object is not readable (e.g., audio data)

Front 297

MIME Content Type: Text Type

Back 297

no special software is required to get the full meaning of the text, aside from support of the indicated character set. (simply a string of ASCII characters)

Front 298

MIME Content Type: Multipart type

Back 298

indicates that the body contains multiple, independent parts
Mutipart/Mixed subtype: multiple parts are bundled
Multipart/Parallel subtype: order of the parts is not significant
Multipart/Alternative Subtype: various parts are different representations of the same information
Multipart/Digest Subtype: used when each of the body parts is interpreted as an RFC 822 message with headers.
Message type: provides a number of important capabilities - indicates that the body is an entire message, including header and body.
Message/Partial subtype: enables fragmentation of a large message in a number of parts.

Front 299

Boundary

Back 299

Defines the delimiter between body parts, should not appear in any parts of the message.

Front 300

MIME Content Type: Message type

Back 300

The body is itself an encapsulated message that conforms to RFC 822. Used to allow fragmentation of large mail items, in a way that is transparent to the recipient

Front 301

MIME Content Type: Message/partial Subtype

Back 301

enables fragmentation of a large message into a number of parts which must be reassembled at the destination. Will include: ID, Number (sequence indicating position), Total (total number of parts)

Front 302

MIME Content Type: Message/External Body subtype

Back 302

indicates that the actual data to be conveyed in this message are not contained in the body, instead the body contains the information needed to access the data

Front 303

MIME Access Type Parameters

Back 303

FTP
TFTP
Anon-FTP
Local-File
AFS
Mail-Server

Front 304

HTTP

Back 304

transaction-oriented client/server protocol provides reliability, stateless protocol - each transaction is treated independently. Flexible in the formats that it can handle.

Front 305

HTTP User Agent

Back 305

the client that intiates the request, such as a web browser being run on behalf of an end user

Front 306

HTTP Origin Server

Back 306

The server on which a resource of interest resides (web server)

Front 307

Cache

Back 307

A programs local store of response messages and the subsystem that controls its message storage, retrieval and deletion.

Front 308

HTTP Client

Back 308

an application program that establishes connections for the purpose of sending requests.

Front 309

HTTP Connection

Back 309

A transport layer virtual circuit established between two application programs for the purposes of communcation

Front 310

HTTP Entity

Back 310

a particular representation or rendition of a data resource, or reply from a service resource that may be enclosed within a request or response message, consists of entity headers and an entity body

Front 311

HTTP Gateway

Back 311

a server that acts as an intermediary for some other server

Front 312

HTTP Message

Back 312

basic unit of HTTP communication, consisting of a structured sequence of octets transmitted via the connection

Front 313

Proxy

Back 313

an intermediary program that acts as both a server and a client for the purpose of making requests on behalf of other clients. Must interpret and, if necessary, rewrite a message before forwarding it.

Front 314

Resource

Back 314

A network data object or service that can be identified by a URI

Front 315

HTTP Server

Back 315

An application program that accepts connections in order to service requests by sending back responses.

Front 316

Tunnel

Back 316

An intermediary program that is acting as a blind relay between two connections.

Front 317

Proxy: Security Intermediary

Back 317

the client and server may be separated by a security intermediary such as a firewall.

Front 318

Proxy: Different Versions of HTTP

Back 318

Proxy can implement both versions and perform the required mapping

Front 319

Gateway: Security Intermediary

Back 319

client and server may be separated by a security intermediary such as a firewall, with the gateway on the server side of the firewall

Front 320

Gateway: Non-HTTP Server

Back 320

Gateway that provides the capability to contact servers for protocols other than HTTP e.g. FTP and Gopher servers. The gateway server contacts the relevant FTP/Gopher server, obtains the desired result, then converts into a form suitable for HTTP and transmits back to the client.

Front 321

IPSec (IP Security)

Back 321

transparent to end users and applications and provides a general-purpose security solution. Includes a filtering capability so that only selected traffic need incur the overhead of IPSec processing.

Front 322

Secure Sockets Layer (SSL)

Back 322

a layer i the TCP/IP protocol architecture that provides security functions.

Front 323

Socket

Back 323

a method of directing data to the appropriate application in ta TCP/IP network.

Front 324

Three Categories of SSL Security

Back 324

Confidentiality - all data is encrypted
Message Integrity - assures the message is not altered or substituted for en route
Authentication - validates the identity of one or both partners to the exchange

Front 325

HTTPS (HTTP over SSL

Back 325

Refers to the combination of HTTP and SSL to implement secure communication between a web browser and a web server.

Front 326

Session Initiation Protocol (SIP)

Back 326

defined in RFC 3261, an application-level control protocol for setting up, modifying, and terminating real-time sessions between participants over an IP data network. Can support any type of single or multimedia.

Front 327

SIP Uniform Resource Identifier (URI)

Back 327

identification of a resource with an SIP network.

Front 328

Session Description Protocol

Back 328

defined in RFC 2327, describes the content of sessions including telephony, Internet radio and multimedia applications

Front 329

SIP Location Service

Back 329

Location service used by a SIP redirect or proxy server to obtain information about a caller's possible location.

Front 330

SIP Method

Back 330

first line of a request, which defines the nature of the request

Front 331

SIP Proxy Server

Back 331

An intermediary entity that acts as both a server and a client for the purpose of making requests on behalf of other clients. Also useful for enforcing policy

Front 332

SIP Redirect Server

Back 332

Used during session initiation to determine the address of the called device, returns this information to the calling device and directs the UAC to contact an alternate URI

Front 333

SIP Regisrar

Back 333

A server that accepts Register requests and places the information it receives in those requests into the location service for the domain it handles.

Front 334

Voice Over IP (VoIP)

Back 334

Internet Telephony, will probably be the standard IP signaling mechanism for voice and multimedia calling services

Front 335

Network Class

Back 335

The IP address is coded to allow a variable allocation of bits to specify network and host. The encoding provides flexibility in assignint addresses to hosts and allows a mix of network sizs on an internet.

Front 336

What are the Three principal network classes?

Back 336

Class A: Few Networks, each with many hosts
Class B: Medium number of networks, each with a medium number of hosts
Class C: Many networks, each with a few hosts

Front 337

Dotted Decimal Notation

Back 337

format of IP addresses - a decimal number represents each of the octets o the 32-bit address.

Front 338

Class A: Few Networks, each with many hosts

Back 338

All Class A network addresses begin with a binary 0; binary 00000000 thru 01111111 (0 - 127) are reserved, making 126 Potential Class A network numbers

Front 339

Class B: Medium number of networks, each with a medium number of hosts

Back 339

Class B addresses begin with a binary 10; binary 10000000 to 10111111. The second octet is also part of the Class B address, so theat there are 2 to the 14 power = 16,384 Class B addresses.

Front 340

Class C: Many networks, each with a few hosts

Back 340

The first decimal number ranges from 192 - 223 (binary 11000000 to 11011111); the total number of Class C addresses is 2 to the 21 power = 2,097,152

Front 341

Subnet Masks

Back 341

a logically visible subdivision of an IP network.[1] The practice of dividing a network into two or more networks is called subnetting.

Front 342

Router Function

Back 342

responsible for receiving and forwarding packets through the interconnected set of networks. Makes routing decisions based on knoowledge of the topology and traffic/delay condtions of the internet-must avoid portions of the newtwork that have failed and should avoid portions of the network that are congested.

Front 343

Two Concepts of Routing Function

Back 343

Routing Information
Routing Algorithm

Front 344

Routing Information

Back 344

Information about the topology and delays of the internet

Front 345

Roting Algorithm

Back 345

The algorithm used to make a routing decision for a particular datagram, based on current routing information

Front 346

Characteristics Autonomous System (AS)

Back 346

1. An AS is a set of routers and networks managed by a single organization.
2. An AS consists of a group of routers exchanging information via a common routing protocol.
3. Except in times of failure, an AS is connected (in a graph-theoretic sense); that is, there is a path between any pair of nodes.

Front 347

Interior Router Protocol (IRP)

Back 347

A shared routing protocol passes routing informaton between routers within an AS - does not need to be shared outside the system - flexibility that allows IRPs to be custom tailored to specific applicaitons and requirements. Needs to build up a rather detailed model of the interconnection of routers within an AS in order to calculate the least-cost path from a given router to any network within the AS

Front 348

Exterior Router Protocol (ERP)

Back 348

the protocol used to pass routing information between routers in different ASs. supports the exchange of summary reachability information between separately administered ASs - Simpler and uses less detailed information than an IRP

Front 349

Border Gateway Protocol (BGP)

Back 349

developed for use in conjucation with internets that employ the TCP/IP suite - concepts are applicable to any internet.
**The preferred ERP for the internet
allows routers (gateways in the standard) in different ASs to cooperate in the exchange of routing information. Operates in terms of messages which are sent over TCP connections. Current version - BGP-4

Front 350

Neighbors

Back 350

Refers to two routers that share the same network.

Front 351

What are the 3 functional procedures in BGP?

Back 351

Neighbor Acquisition -
Neighbor Reachability -
Network Reachability -

Front 352

Neighbor Acquisition

Back 352

occurs when two neighboring routers in different autonomous systems agree to exchange routing infomation regularly.

Front 353

Neighbor Reachability

Back 353

Once neighbor relationship is establised the neighbor reachability procedure is used to maintain the relationship - periodically pass Keepalive message between routers.

Front 354

Network Reachability

Back 354

Each router maintains a database of the networks that it can reach and the preferred route for reaching each network.

Front 355

Open Shortest Path First (OSPF) Protocol

Back 355

Protocol sidely sed as an interior router protocol in TCP/IP networks. Uses what is known as a link state routing algorithm. Each router maintains descriptions of the state of its local links to networks

Front 356

Each router maintains a database that reflects the known __________ of the autonomous system of which it is a part.

Back 356

topology

topology expressed as a directed graph, consisting of the following:
1. Vertices, or nodes, of two types
- Router
- Network
a. Transit if it can carry data that neither originates nor terminates on an end system attached to this network
b. Stub, if it is not a transit network
2. Edges, of two types:
- A graph edge that connects two router viertices when the correspoonding routers are connected to each other by a direct point-to-point link
- A graph edge that connects a router vertex to a network vertex when the router is directly connected to the network.

Front 357

'What are the two significant trends the altered the role of the PC, and therefore the requirements of the LAN?

Back 357

1. The speed and computing power of PCs continued to enjoy explosive growth.
2. IT organizations have recognized the LAN as a viable and essential computing platform, resulting in the focus on Network