Data and Computer Communications - MedTerm
(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.
Near-Real-Time Replication
(more common) Backups occur in batches with a small amount of lag time (e.g., 30 minutes)
Key Characteristics for effective use of services in a Service-Oriented Architecture:
* Coarse-grained * Interface-based design * Discoverable * Single Instance * Loosely coupled * Asynchronous
Advantages of a Web/Database system compared to a more traditional database approach
* Ease of administration. * Deployment * Development Speed * Flexible Information Presentation
Potential disadvantages of a Web/Database system
* Functionality may be more limited * Stateless Operation-the web server keeps no information between transactions to track the state of the user
Problems associated with using traditional client/server systems
* 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.
Describe three ways that an application can be allocated in a distributed environment. (Forms of Distributed Applications)
* 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.
Intranet Features
* 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
Characteristics that make client/server distinct from ordinary distributed processing:
* 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
Three Logical Phases of Mail Transfer
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
Characteristics Autonomous System (AS)
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.
Web systems with a response time between ___________ result in loss of some user concentration.
3 and 10 seconds
Web systems with a ________________ or better response time maintain a high level of user attention.
3-second
What is the bandwidth of telephone voice?
3400 Hz of bandwidth = moderate quality
Centralized Support Staff
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.
Local Area Network (LAN)
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.
Server
A computer, usually a high-powered workstation or a mainframe, that houses information for manipulation by networked clients.
DDP System
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
Analog
A continuous signal (i.e., a voltage) that can take on a continuum of values, an example is the electrical signal coming out of a microphone when someone speaks into it. For analog communication, information rate and channel capacity are measured in (Hz)
Middleware
A set of drivers, APIs or other software that improves connectivity between a client application and a server
Protocol
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
Interior Router Protocol (IRP)
A shared routing protocol passes routing information between routers within an AS - does not need to be shared outside the system - flexibility that allows IRPs to be custom tailored to specific applications 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
GIF
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.
Network Management
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.
Host
Any end system, such as a PC, workstation, or server, that connects to the Internet.
OSI Architecture
Application Presentation Session Transport Network Data link Physical
TCP/IP Architecture
Application Transport (Host-to-Host) Internet Network Access Physical
Asynchronous Transfer Mode (ATM)
Cell Relay; a culmination of developments in circuit switching and packet switching. ATM uses fixed-length packets, called cells.
Content-Description
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)
MIME-Version
First of the new header fields, must have the parameter value 1.0 which indicates the message conforms to the RFCs
Unified Communications
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.
NSF
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.
Content-ID
Fourth of the new header fields, used to uniquely identify MIME entities in multiple contexts.
____________________ 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.
Frame Rate
Based on your reading of the chapter, name five components that might be part of a fully centralized system.
Centralized computers Centralized processing Centralized data Centralized control Centralized support staff
Compare the address space between IPv4 and IPv6. How many bits are used in each?
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
What is the difference between an ISP and a POP?
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 telecommunications equipment.
Raster Graphics
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.
Real-Time Replication
Immediately synchronized data/database
List two common image formats
JPEG - good for photos GIF - good for web-based graphics and animations
What major problems for the data processing manager result from distributed small systems?
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.
Physical Layer
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.
JPEG
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).
What is the difference between an NAP and an NSP?
NAP is the physical facility/Infrastructure that provides the physical access paths between routers. NSP is the Company that provides Equipment responsible for routing.
TCP/IP Protocol
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.
Centrex
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
IP Address
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.
UDP
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
Gateway: Security Intermediary
client and server may be separated by a security intermediary such as a firewall, with the gateway on the server side of the firewall
Network Service Provider (NSP)
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.
Internet Service Provider (ISP)
company that provides other companies or individuals with access to, or presence on, the Internet
Virtual Private Network (VPN)
consists of a set of computers that interconnect by means of a relatively unsecured network and that make use of encryption and special protocols to provide security.
Session Description Protocol
defined in RFC 2327, describes the content of sessions including telephony, Internet radio and multimedia applications
Session Initiation Protocol (SIP)
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.
Border Gateway Protocol (BGP)
developed for use in conjunction 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
Message Passing
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
Internet Mail Access Protocol (IMAP)
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
MIME Content Type: Message/partial Subtype
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)
SIP Method
first line of a request, which defines the nature of the request
Dotted Decimal Notation
format of IP addresses - a decimal number represents each of the octets o the 32-bit address.
User Agent (UA)
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
Mail Command
gives the reverse path, which can be used to report errors.
SIP Uniform Resource Identifier (URI)
identification of a resource with an SIP network.
RCPT Command
identifies an individual recipient of the mail data; multiple recipients are specified by multiple use of this command.
Vector Graphics
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.
MIME Content Type: Message/External Body subtype
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
Simple Mail Transfer Protocol (SMTP)
used for transfer of mail from a UA to an MTA and from one MTA to another
Internet Layer
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
Downside of modifying an image or stream in order to reduce the size
you usually sacrifice some amount of quality.
Host Based Processing
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.
Neighbor Acquisition
occurs when two neighboring routers in different autonomous systems agree to exchange routing information regularly.
Network Access Point (NAP)
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.
Centralized Computers
one or more computers are located in a central facility
Grayscale Image
produced if each pixel is defined by more than one bit, representing shades of gray.
SSH (Secure Shell)
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.;
Intranet
provides users the features and applications of the Internet but isolated within the organization.
What is a DNS Resource Record?
record that includes the Name, IP Address and other information about hosts
Availability
refers to the percentage of time that a particular function or application is available for users.
Router Function
responsible for receiving and forwarding packets through the interconnected set of networks. Makes routing decisions based on knowledge of the topology and traffic/delay conditions of the internet-must avoid portions of the network that have failed and should avoid portions of the network that are congested.
What is the major function of the network access layer?
routing the data to the appropriate destination using the address of the destination computer that is provided by the sending computer.
IP Datagrams/Packets
sequenced packets of data sent via Internet
Asynchronous
services use an asynchronous message-passing approach - not required.
Server-based processing
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.
Point of Presence (POP)
site that has a collection of telecommunications equipment; usually refers to an ISP or telephone company sites.
Client/Server Binding
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.
IPv6
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
Middleware
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.
HyperText Markup Language (HTML)
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.
Internet Protocol (IP)
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.
Intermediate Systems (ISs)
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.
Header
system defined control information that precedes user data in a protocol data unit
SMTP Sender
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.
Receive Function
tells from whom a message is desired (including "all") and provides a buffer where the incoming message is to be stored.
The central feature of a client/server architecture is:
the allocation of application-level tasks between clients and servers
Cooperative Processing
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
Digital Video
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.
Proxy: Security Intermediary
the client and server may be separated by a security intermediary such as a firewall.
HTTP User Agent
the client that initiates the request, such as a web browser being run on behalf of an end user
End Systems (ESs)
the devices connected to the subnetwork.
ISP POP
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
What is Mosaic?
the first graphically oriented browser
Intranet
the implementation of Internet technologies within a corporate organization rather than for external connection to the global internet.
Local Loop (Last Mile)
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.
Application Programming Interface (API)
the middleware which cuts across all client and server platforms, is responsible for routing client requests to the appropriate server
International Reference Alphabet (IRA)
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.
Central Office
the place where telephone companies terminate customer lines and locate switching equipment to interconnect those lines with other networks
Exterior Router Protocol (ERP)
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
Application Layer
the sending application generates a block of data and passes this to the transport layer.
Application Logic
the software for data analysis that interacts with the database. i.e., SQL
Customer Premises Equipment (CPE)
the telecommunications equipment located onsite with the host.
Response Time
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.
Purpose of the Internet
to interconnect end systems called hosts.
Each router maintains a database that reflects the known __________ of the autonomous system of which it is a part.
topology
HTTP
transaction-oriented client/server protocol provides reliability, stateless protocol - each transaction is treated independently. Flexible in the formats that it can handle.
TVoIP
transmission of video over IP-based networks, including the internet and private intranets, known as video streaming.
IPSec (IP Security)
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.
What is the difference between a name server and a resolver in DNS
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.
What are the 3 functional procedures in BGP?
Neighbor Acquisition - Neighbor Reachability - Network Reachability -
What are two applications programs that have taken the place of Mosaic?
Netscape Navigator & Internet Explorer
The third essential ingredient of the client/server environment is the ________________.
Network
Usenet
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.
Internet
Public telecommunication network. A worldwide internetwork based on TCP/IP that interconnects thousands of public and private networks and millions of users.
Loosely coupled
Services are connected to other services and clients using standard, dependency-reducing, decoupled message-based methods such as XML document exchanges.
Interface-Based Design
Services implement separately defined interfaces, multiple services can implement a common interface and a service can implement multiple interfaces
Discoverable
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.
File Transfer Protocol (FTP)
Similar open functionality (to Telnet) that allows the transparent transfer of files from one computer to another over the network.
Protocol Architecture
Software structure that implements the communications function - typically consists of a layered set of protocols with one or more protocols at each layer.
Send Function
Specifies a destination and includes the message content.
Office Automation Support System
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.
_______________ interfaces are used to enable service modules to communicate with one another and to enable client applications to communicate with service modules.
Standardized
Multipurpose Internet Mail Extensions (MIME)
Supplements SMTP and allows the encapsulation of multimedia (nontext) messages inside of a standard SMTP message
Simple Mail Transfer Protocol (SMTP)
Supports a basic electronic mail facility by providing a mechanism for transferring message among separate hosts. Features include mailing lists, return receipts, and forwarding.
Audio Service
Supports applications based on sound, usually of the human voice. Primary application - telephone communication
What two protocols form the foundation of and govern the way we communicate on the Internet?
TCP - Transmission Control Protocol IP - Internet Protocol
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?
TCP/IP architecture is configured for communications.
Interlacing
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.
Image Communications
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.
What were two of the first applications developed for use over a network?
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.
Network Class
The IP address is coded to allow a variable allocation of bits to specify network and host. The encoding provides flexibility in assigning addresses to hosts and allows a mix of network sizes on an internet.
Connectivity
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.
Roting Algorithm
The algorithm used to make a routing decision for a particular datagram, based on current routing information
Virtually any communication signal can be expressed as a combination of pure oscillations of various frequencies.
The bandwidth measures the limits of these frequencies. The higher the frequencies allowed, the more accurately a complex signal can be represented.
MIME Content Type: Message type
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
DNS Database
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.
Computer Processing Power
The faster the computer, the shorter the response time. Increased processing power means increased cost.
Class C: Many networks, each with a few hosts
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
Name two approaches that can be used for increasing efficiency of transmission services.
Two approaches that can be used for increasing efficiency of transmission services are multiplexing and compression.
Client Machines
Typically single-user PCs or workstations that provide a highly user-friendly interface to the end user.
MIME Specification includes these three elements:
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 encoding are defined that enable the conversion of any content format into a form that is protected from alteration by the mail system.
Two Methods by which queries are forwarded and results returned in a query.
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.
SMTP is not concerned with the format or content of messages themselves, with two exceptions:
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.
Connection Setup Sequence
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.
What are two significant trends in industry that illustrate the success of client/server computing:
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.
DNS Operation Steps
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 requester. 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.
Conceptual queued message has two parts:
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.
What are the four reasons that dictate the way the division of data and application processing:
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
Web systems with a response time above ___________ discourage the user, who may simply abort the session.
10-seconds
Centralized Control
A data processing or information systems manager has responsibility for the centralized data processing facility
Relational Database
A database in which information access is limited to the selection of rows that satisfy all search criteria.
Routers
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.
Text
A familiar example of digital data
Frame Relay
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.
Packet
A group of bits that includes data plus control information. Generally refers to a network layer (OSI layer 3) protocol data unit.
Structured Query Language (SQL)
A language developed by IBM and standardized by ANSI for addressing, creating, updating, or querying relational databases.
What are some advantages of layering as seen in the TCP/IP architecture?
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.
Service Requester
A network code that discovers and invokes other software services to provide a business solution.
Resource
A network data object or service that can be identified by a URI
Service Provider
A network node that provides a service interface for a software asset that manages a specific set of tasks.
What is the difference between a printable character and a control character?
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.
Cache
A programs local store of response messages and the subsystem that controls its message storage, retrieval and deletion.
SIP Registrar
A server that accepts Register requests and places the information it receives in those requests into the location service for the domain it handles.
Packet Switching
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.
Service broker
A specific kind of service provider interfaces and service locations, can pass on service requests to one or more additional service providers.
Database
A structured collection of data stored for use in one or more applications. Contains the relationships between data items and groups of data items.
Database Management System (DBMS)
A suite of programs for constructing and maintaining the database and for offering ad hoc query facilities to multiple users and applications.
HTTP Connection
A transport layer virtual circuit established between two application programs for the purposes of communication
Port
A transport-layer address that identifies a user of a transport-layer protocol.
Networking Implications of Images
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.
Internet
A worldwide internetwork based on TCP/IP that interconnects thousands of public and private networks and millions of users.
What is the difference between and the Internet?
ARPANET was a network that that used packet-switching to communicate with it's hosts. The Internet is a technique/protocol for interconnecting networks.
SMTP Receiver
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.
Class A: Few Networks, each with many hosts
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
Centralized Processing
All applications are run on the central data processing facility
Connections Setup
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.
HTTP Server
An application program that accepts connections in order to service requests by sending back responses.
SIP Proxy Server
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
Tunnel
An intermediary program that is acting as a blind relay between two connections.
Two types of ISs
Bridges Routers
Contrast of the function of application software with that of interconnection software.
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.
Three Tier Client/Server Approach
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)
Distributed Applications
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.
Centralized Data Processing
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
Performance
Assessment of the system and the applications it supports.
Why are burdens on Manager greater today than in previous years?
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.
Video Communications
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.
The Two primary paradigms for electronic communications were _______________ switching and ____________ switching.
Circuit Switching - voice communications Packet Switching - telegraph and telex
What are the Three principal network classes?
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
Class B: Medium number of networks, each with a medium number of hosts
Class B addresses begin with a binary 10; binary 10000000 to 10111111. The second octet is also part of the Class B address, so that there are 2 to the 14 power = 16,384 Class B addresses.
Object-Oriented Mechanisms
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.
Zone
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.
Distributed database
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.
____________ _____________ enables the client and server to interoperate.
Communications software i.e., TCP/IP
The process that takes advantage of redundancy to reduce the number of bits sent for a given piece of data is called what?
Compression
What is a distributed data processing (DDP) strategy?
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 .
Distributed Data Processing (DDP)
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.
Three Categories of SSL Security
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
Name three types of communications and networking requirements generated by the use of distributed data processing.
Connectivity Availability Performance
Packet Switching
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.
Horizontal Partitioning
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.
Vertical Partitioning
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.
The most common type of server is a _______________ server, usually controlling a ________________ ______________.
Database Relational Database
Centralized Database
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.
In designing a distributed database, database objectives and communications objectives are not always the same. Distinguish between the two sets of objectives.
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.
RFC 822
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.
Boundary
Defines the delimiter between body parts, should not appear in any parts of the message.
ARPANET
Developed in 1969, the first operational packet-switching network which began operations in four locations.
Client/server computing is _____________ computing
Distributed
Why would a company want a distributed database?
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.
What is a DNS?
Domain Name System, directory lookup service that provides a mapping between the name of a host on the internet and its numerical address.
Name the four major components of the domain name system.
Domain name space DNS database Name servers Resolvers
How does a factory often reflect the use of distributed devices?
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.
Network Reachability
Each router maintains a database of the networks that it can reach and the preferred route for reaching each network.
Single Instance
Each service is a single, always running instance that a number of clients communicate with.
Telnet
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.
What are some advantages of a centralized processing facility?
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.
Parity - in IRA
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.
The most heavily used network application in the corporate world is:
Electronic Mail
Purpose of Middleware
Enables an application or user at a client to access a variety of services on servers without being concerned about differences among servers.
MIME Access Type Parameters
FTP TFTP Anon-FTP Local-File AFS Mail-Server
Gateway: Non-HTTP Server
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.
Response time ranges:
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. Decision 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
What is the programming language used to display Web pages?
HTML - HyperText Markup Language
Four Types of Information Found on Networks:
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.
Which version of IP is the most prevalent today?
IPv4
Routing Information
Information about the topology and delays of the internet
Analog
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.
Digital
Information 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)
Protocol Data Unit (PDU)
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.
Voice Over IP (VoIP)
Internet Telephony, will probably be the standard IP signaling mechanism for voice and multimedia calling services
Proxy: Different Versions of HTTP
Proxy can implement both versions and perform the required mapping
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?
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.
What are the two different interpretations of the prefixes kilo, mega and giga?
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.
SIP Location Service
Location service used by a SIP redirect or proxy server to obtain information about a caller's possible location.
Extranet
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).
Extranet
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
Message Switching
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.
Centralized 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.
Circuit Switching
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.
Wide Area Networks (WANs)
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.
Does a router require that all attached layer 2 protocols are the same?
No .
Lossless compression
No loss of information is acceptable in compression, ratios run below 5:1 Example: Medical Imaging
Does all traffic running on the Internet use TCP?
No, there is FTP, Telnet,SMTP, UDP etc.
Applications for the distributed environment are available much sooner than those in the centralized environment. What are the main sources of these applications?
Off-The-Shelf Applications - readily available (no backlog) and don't need to worry about communicating requirements from users to professional programmers.
Neighbor Reachability
Once neighbor relationship is established the neighbor reachability procedure is used to maintain the relationship - periodically pass Keepalive message between routers.
Coarse-grained
Operations on services are frequently implemented to encompass more functionality and operate on larger data sets
What is the difference between Centrex and PBX?
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.
List two common image formats.
PDF - good for text and graphics Postscript - page description language - desktop printers and all high-end printing systems.
Three-Layer model of Enterprise Communications
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.
Postscript
Page description language that is built into many desktop printers and virtually all high-end printing systems.
Thick Client
Presentation logic , Application logic and Database logic are performed at the client level, Database logic and DBMS are performed at the server level
Thin Client
Presentation logic is at the client level, Application Logic, Database logic and DBMS are at the server level.
Describe the process used to prevent flicker in a video screen.
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.
Voice Communications
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.
Intranet
Private Internets within Organizations that provide the key internet applications .
Quantization
Process where after sampling , the signal amplitudes must be put in digital form
What are some functions that are centralized in a fully centralized data processing facility?
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
When a computer and a user interact at a pace that ensures that neither has to wait on the other, _____________ increases significantly.
Productivity
Resolvers
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.
______________ scan is used for computer monitors and most HDTV schemes
Progressive
Open Shortest Path First (OSPF) Protocol
Protocol sidelined 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
Query Language
Provides a uniform interface tot he database for users and applications.
Transmission Control Protocol (TCP)
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.
Competing Requirements
Providing rapid response time to some processes may penalize other processes.
Data Communications
Refers to any form of information transfer other than voice
Multiplexing
Refers to the ability of a number of devices to share a transmission facility
HTTPS (HTTP over SSL
Refers to the combination of HTTP and SSL to implement secure communication between a web browser and a web server.
Convergence
Refers to the merger of previously distinct telephony and information technologies and markets. Brings many benefits including simplified network management, increased efficiency and greater flexibility at the application level.
Neighbors
Refers to two routers that share the same network.
What are some reasons for wanting to interconnect distributed data processing systems?
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
Two Concepts of Routing Function
Routing Information Routing Algorithm
__________ is the standard protocol for transferring mail between hosts in the TCP/IP protocol suite (defined in RFC 821.
SMTP
Connection Closing
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
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.
Sample
Content-Type
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
Client/Server
Separate computers (servers) support database functions, store files, perform printing services and provide other specialized functions on a shared basis for many users (clients).
Name Servers
Server Programs that hold information about a portion of the domain name tree structure and the associated RRs.
Video
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.
How has the technology of the compact disc used in the music industry been used in image communications?
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.
HTTP Origin Server
The server on which a resource of interest resides (web server)
Protocol Architecture
The software structure that implements the communications function. Typically consists of a layered set of protocols, with one or more protocols at each layer.
Define Response Time.
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.
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
The time span between the moment the user enters a command and the moment a complete response is displayed on the terminal
Why do we still need mainframe computers even though personal computers and workstations have become so much more powerful?
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.
Content-Transfer-Encoding
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.
Why has optical fiber transmission become popular in the past few years?
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.
Root Name Servers
Top of the server hierarchy, servers that share responsibility for the top-level zones.
Three kinds of basic organizational difficulties communications technology can help companies overcome:
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.
TCP/IP
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.
SIP Redirect Server
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
SMTP Protocol
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.
Client/Server Architecture
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)
Key Features of the DNS database
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.
Explain the basic principles of vector graphics and raster graphics.
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.
Distinguish between horizontal and vertical partitioning of applications.
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.
Client-Based Processing
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.
What types of communications can be carried by satellite transmission?
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.
Wireless Networking
Wireless technology commonly used in both WANs and data networks. Provide advantages in the areas of mobility and ease of installation and configuration.
Remote Procedure Call
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.
Hypertext Transfer Protocol (HTTP)
a communications protocol for use in TCP/IP networks for fetching the files from the appropriate servers as specified by the hyperlinks.
Persistent Binding
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.
IPv4
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).
World Wide Web (www)
a distributed hypermedia technology that facilitates the international exchange of products, research findings and information.
Distributed Devices
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.
Electronic Mail
a facility that allows users at workstations and terminals to compose and exchange messages
Communication Network
a facility that provides a data transfer service among devices attached to the network.
Service-Oriented Architecture
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.
What is an Internet Domain?
a group of hosts that are under the administrative control of a single entity, i.e., com, net, gov
Domain
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, ...
Secure Sockets Layer (SSL)
a layer i the TCP/IP protocol architecture that provides security functions.
Nonpersistent Binding
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.
Subnet Masks
a logically visible subdivision of an IP network.[1] The practice of dividing a network into two or more networks is called subnetting.
Subnetwork
a logically visible subdivision of an IP network; constituent network
Socket
a method of directing data to the appropriate application in ta TCP/IP network.
HTTP Entity
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
Graphical User Interface (GUI)
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.
HTTP Gateway
a server that acts as an intermediary for some other server
IPSec
a set of Internet standards that provides the capability to secure communications across a LAN, across private and public WANs and across the Internet
Open Systems Interconnection (OSI)
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.
Message Transfer Agent (MTA)
accepts messages from the user agent for transmission across a network or internetwork, concerned with the protocol operation needed to transmit and deliver messages
Network Layer/ Network Access Layer
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
Post Office Protocol (POP3)
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
Electronic Mailing List
an alias that has multiple destinations, usually created to discuss specific topics. Each subscriber receives messages one at a time, as they are sent.
HTTP Client
an application program that establishes connections for the purpose of sending requests.
Inventory Software
an application that will run on the server or mainframe - user cannot work with these applications unless they are connected and possibly authenticated.
Mailbox
an entity maintained buy the file management system and is in the nature of a file directory.
Checksum
an error-detecting code based on a summation operation performed on the bits to be checked.
Frame Check Sequence (FCS)
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.
Multipurpose Internet Mail Extensions (MIME)
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.
Proxy
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.
Private Branch Exchange (PBX)
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.
Replicated Database
an overall strategy for data distribution. all or part of the database is copied at two or more computers.l
Transport Layer
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
Voice
audio service support applications based on sound, usually of the human voice - primarily telephone, other applications: telemarketing, voice mail, audio teleconferencing and entertainment radio.
Lossy Compression
barely perceivable loss of information, may reduce the data by factors of roughly 10:1 to 20:1
HTTP Message
basic unit of HTTP communication, consisting of a structured sequence of octets transmitted via the connection
MIME Content Type: Multipart type
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.
Domain Name System (DNS)
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.
Deferred Replication
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.
Compression
involves squeezing the data down so that a lower-capacity, cheaper transmission facility can be used to meet a given demand.
Data Manipulation Language (DML)
language that provides a powerful set of tools for application developers.
Data Definition Language (DDL)
language used to define the database logical structure and procedural properties, represented by a set of database description tables.
Characteristics that change audio file sizes
length, sampling rate and bits per sample
What are the three underlying mechanisms of middleware:
message passing remote procedure calls object-oriented mechanisms
Domain namespace
naming system on which DNS is based is a hierarchical and logical tree structure used to identify resources on the Internet
MIME Content Type: Text Type
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)
