Glossary

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A

Accepted packets

The data packets were captured and analyzed by Sax2ids. Packet is "open systems interconnection" (OSI) network of transmission units, which is composed of data and recognition, source, destination address and error control data binary system information.

ASCII

 ASCII stands for American Standard Code for Information Interchange. Computers can only understand numbers, so an ASCII code is the numerical representation of a character like 'c' or '#' or an action of some sort. Here are some samples ASCII codes and the characters they represent:

Adapter

 An adapter is a physical device that allows one hardware or electronic interface to be adapted (accommodated without loss of function) to another hardware or electronic interface. In a computer, an adapter is often built into a card that can be inserted into a slot on the computer's motherboard. The card adapts information that is exchanged between the computer's microprocessor and the devices that the card supports.

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B

Bandwidth

 In computer networking and computer science, digital bandwidth or just bandwidth often refers to a bit rate measured in bits/s, for example, network throughput. The reason for the connection of data rate with the term bandwidth is that according to Hartley's law, the limit to the data rate of a physical communication link is related to its bandwidth in hertz, sometimes denoted analog bandwidth in computer networking literature. For the case of high signal-to-noise ratio, the digital bandwidth consumption (i.e. the throughput) of a bit stream or logical link in a computer network is proportional to the average spectral bandwidth of the analog signal representing the bit stream during a studied time interval. However, measuring bandwidth in bits/s is disputed due to confusion with the original definition. Less ambiguous terms are for example gross bit rate, net bit rate, throughput, good put or channel capacity.

Binary

Binary is a numeric system which uses two numerals to represent all real numbers. While the most common counting system, the decimal system, uses ten numerals, binary uses only 0 and 1.

Buffer

This is a small amount of data that is stored for a short amount of time, typically in the computer's memory (RAM). The purpose of a buffer is to hold data right before it is used.

Bridge

A device that connects two local-area networks (LANs), or two segments of the same LAN that use the same protocol, such as Ethernet or Token-Ring.

Byte

Abbreviation for binary term, a unit of storage capable of holding a single character. On almost all modern computers, a byte is equal to 8 bits. Large amounts of memory are indicated in terms of kilobytes (1,024 bytes), megabytes (1,048,576 bytes), and gigabytes (1,073,741,824 bytes).

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C

Capture

Sax2ids’s main functions can be broken down into five steps: capture, analysis, monitor tracking, show results and saving log.

Cache

Cache (pronounced cash) memory is extremely fast memory that is built into a computer’s central processing unit (CPU), or located next to it on a separate chip. The CPU uses cache memory to store instructions that are repeatedly required to run programs, improving overall system speed. The advantage of cache memory is that the CPU does not have to use the motherboard’s system bus for data transfer. Whenever data must be passed through the system bus, the data transfer speed slows to the motherboard’s capability. The CPU can process data much faster by avoiding the bottleneck created by the system bus.

Client

A client is the requesting program or user in a client/server relationship. For example, the user of a Web browser is effectively making client requests for pages from servers all over the Web. The browser itself is a client in its relationship with the computer that is getting and returning the requested HTML file. The computer handling the request and sending back the HTML file is a server.

Connection

A TCP connection is always initiated with the 3-way handshake, which establishes and negotiates the actual connection over which data will be sent. The whole session is begun with a SYN packet, then a SYN/ACKpacket and finally an ACK packet to acknowledge the whole session establishment. At this point the connection is established and able to start sending data. The big problem is, how does connection tracking hook up into this? Quite simply really.

Content length

Display the amount of information which be sent to the recipient by decimal system figures.

Columns

In the user interface of Sax2ids, column included the titles in the list view and the content of the changed title.

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D  

Disable

Enable equipment procedures are not on role. For example, if you disable a device of the hardware configuration, when the computer uses hardware configuration, you will not be able to use the equipment. Do not open the equipment, which can release the resources that be allocated to the equipment.

Delete method

The DELETE method requests that the origin server delete the resource identified by the Request-URI. This method MAY be overridden by human intervention (or other means) on the origin server. The client cannot be guaranteed that the operation has been carried out, even if the status code returned from the origin server indicates that the action has been completed successfully. However, the server SHOULD NOT indicate success unless, at the time the response is given, it intends to delete the resource or move it to an inaccessible location.

DHCP

Dynamic Host Configuration Protocol (DHCP) is a network protocol that enables a server to automatically assign an IP address to an individual computer's TCP/IP stack software. DHCP assigns a number dynamically from a defined range of numbers (i.e., a scope) configured for a given network.

Default value

Default the value of a specific variable, designated by the operating system automatically and is continuously effective, unless the operator cancel it or make it invalid.

Destination IP

Current data packets were sent to the host's IP address.

Destination MAC

Current data packets were sent to the host's MAC address.

Data size

 The size of the data

Domain

In general, a domain is an area of control or a sphere of knowledge. 

1) In computing and telecommunication in general, a domain is a sphere of knowledge identified by a name. Typically, the knowledge is a collection of facts about some program entities or a number of network points or addresses. 

2) On the Internet, a domain consists of a set of network addresses. This domain is organized in levels. The top level identifies geographic or purpose commonality (for example, the nation that the domain covers or a category such as "commercial"). The second level identifies a unique place within the top level domain and is, in fact, equivalent to a unique address on the Internet (an IP address). Lower levels of domain may also be used. 

Strictly speaking, in the Internet's domain name system (DNS), a domain is a name with which name server records are associated that describe subdomains or host. For example, "whatis.com" could be a domain with records for "www.whatis.com" and "www1.whatis.com," and so forth. 

3) In Windows NT and Windows 2000, a domain is a set of network resources (applications, printers, and so forth) for a group of users. The user need only to log in to the domain to gain access to the resources, which may be located on a number of different servers in the network.

Domain name

In computer networking, a domain name is a name given to a collection of network devices that belong to a domain which is managed according to some common property of the members or within a common administrative boundary. In particular, the term is used to describe the regions of administrative authority within the Domain name system used for the Internet (cf. DNS zone).

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E

Ethernet

Ethernet is a family of frame-based computer networking technologies for local area networks (LANs). The name comes from the physical concept of the ether. It defines a number of wiring and signaling standards for the physical layer, through means of network access at the Media Access Control (MAC)/Data Link Layer, and a common addressing format.

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F

Flag

Flag, characteristics has two stable stations one or a series, which means single information in software.

Firewall

A firewall is a secure and trusted machine that sits between a private network and a public network. The firewall machine is configured with a set of rules that determine which network traffic will be allowed to pass and which will be blocked or refused. In some large organizations, you may even find a firewall located inside their corporate network to segregate sensitive areas of the organization from other employees. Many cases of computer crime occur from within an organization, not just from outside.

FTP (File Transfer Protocol)

File Transfer Protocol (FTP) is a network protocol used to transfer data from one computer to another through a network, such as the Internet.

FTP is a file transfer protocol for exchanging and manipulating files over any TCP-based computer network. A FTP client may connect to a FTP server to manipulate files on that server. As there are many FTP client and server programs available for different operating systems, FTP is a popular choice for exchanging files independent of the operating systems involved.

Frame

 In telecommunications, a frame is data that is transmitted between network points as a unit complete with addressing and necessary protocol control information. A frame is usually transmitted serial bit by bit and contains a header field and a trailer field that "frame" the data. (Some control frames contain no data.)

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G

Get Method

The GET method is used to retrieve information from a specified URI and is assumed to be a safe, repeatable operation by browsers, caches and other HTTP aware components. This means that the operation must have no side effects and GET requests can be re-issued with worrying about the consequences.

Gateway

A node on a network that serves as an entrance to another network. In enterprises, the gateway is the computer that routes the traffic from a workstation to the outside network that is serving the Web pages. In homes, the gateway is the ISP that connects the user to the internet.

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H

Header

In information technology, a header is, in general, something that goes in front of something else and is usually repeated as a standard part of the units of something else. A header can consist of multiple field s, each containing its own value. Here are four common uses:

In a network transmission unit, a header precedes the data or control signals and describes something about the file or transmission unit, such as its length and whether there are other files or transmission units logically or physically associated with this one.

HTML

HTML stands for Hyper Text Markup Language. It is a type of computer language that is primarily used for files that are posted on the internet and viewed by web browsers. HTML files can also be sent via email. 

Although it may seem complex to the uninitiated, HTML is relatively simple. All text, graphics and design elements of a web page are "tagged" with codes that instruct the web browser how to display the files. Such files are easy to recognize because they contain the file extension of 'html' or 'htm'.

In addition to the page content itself, HTML files provide layout and formatting information. HTML is not case sensitive and can be easily updated after the file is created. For the novice web designer, there are many different software utilities and programs available to assist in generating HTML pages.

To format a simple text file into HTML, the user creates tags that start and finish with angle brackets. To end the formatting or change to another format, the HTML developer types the first angle bracket, a backslash, then repeats the command and closes the bracket. For example, <H1>What is HTML?</H1> is the code used to create the heading at the top of this article.

 There are different codes for all sorts of other formatting including italics, tables, paragraphs etc. The "A" tag is used to designate words that are to be displayed as hyperlinks to other pages.

If you would like to view a sample of HTML, a good place to start might be the code that was used to generate this very page. Simply click on the "view" menu on your browser and then select "source". It may look complicated, but if you learned the limited number of tags, you would discover that it is a relatively straightforward language.

Head Method

The HEAD method is used to ask only for information about a document, not for the document itself. HEAD is much faster than GET, as a much smaller amount of data is transferred. It's often used by clients who use caching, to see if the document has changed since it was last accessed. If it was not, then the local copy can be reused, otherwise the updated version must be retrieved with a GET. The met information contained in the HTTP headers in response to a HEAD request should be identical to the information sent in response to a GET request. This method can be used for obtaining met information about the resource identified by the request URI without transferring the data itself. This method is often used for testing hypertext links for validity, accessibility, and recent modification.

HTTP

HTTP is the protocol of the Web, by which Servers and Clients (typically
browsers) communicate. An HTTP transaction comprises a Request sent by
the Client to the Server, and a Response returned from the Server to
the Client.

Hub

In computer networking, a hub is a small, simple, inexpensive device that joins multiple computers together. Many network hubs available today support the Ethernet standard. Other types including USB hubs also exist, but Ethernet is the type traditionally used in home networking.

Host

A computer system that is accessed by a user working at a remote location. Typically, the term is used when there are two computer systems connected by modems and telephone lines. The system that contains the data is called the host, while the computer at which the user sits is called the remote terminal.  

Host Address

The host address, or more properly the host id portion of an IP address is the portion of the address used to identify hosts (which can be any device requiring a Network Interface Card such a personal computer or networked printer) on the network. The network id by contrast is the portion of the address that refers to the network itself.

Host Name

A hostname (occasionally also, a sitename) is the unique name by which a network-attached device (which could consist of a computer, file server, network storage device, fax machine, copier, cable modem, etc.) is known on a network. The hostname is used to identify a particular host in various forms of electronic communication such as the World Wide Web, e-mail or Usenet.

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I

Internet Protocol

The Internet Protocol (IP) is a protocol used for communicating data across a packet-switched internet work using the TCP/IP suite of protocols.

IP is the primary protocol in the Internet Layer of the Internet protocol suite and has the task of delivering datagrams (packets) from the source host to the destination host solely based on its address. For this purpose the Internet Protocol defines addressing methods and structures for datagram encapsulation. The first major version of addressing structure, now referred to as Internet Protocol Version 4 (IPv4) is still the dominant protocol of the Internet, although the successor, Internet Protocol Version 6 (IPv6) is actively deployed world-wide.

ICMP

 ICMP is a complementary protocol to IP (Internet Protocol). Like IP, ICMP resides on the Network Layer of the OSI Model.

ICMP is designed for sending control and test messages across IP networks.

Unlike the Transport Layer protocols TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) which operate on top of IP, ICMP exists alongside IP.

The ability to understand ICMP is a requirement for any IP-compatible network device. However, many security devices such as firewalls block or disable all or part of ICMP functionality for security purposes.

IP Address

An identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination. The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, 1.160.10.240 could be an IP address.

 

IP Checksum

A checksum is a simple error-detection scheme in which each transmitted message that results in a numerical value based on the value of the bytes in a message. The sender places the calculated value in the message (usually in the message header) and sends the value with the message. The receiver applies the same formula to each received message and checks to make sure the accompanying numerical value is the same. If not, the receiver can assume that the message has been corrupted in transmission.

 

IP Identification

An identifying value assigned by the sender to aid in assembling the

    fragments of a datagram.

 

IP IHL

Internet Header Length is the length of the internet header in 32

    bit words, and thus points to the beginning of the data.  Note that

    the minimum value for a correct header is 5.

 

IP Offset

This field indicates where in the datagram this fragment belongs.

The fragment offset is measured in units of 8 octets (64 bits).  The

    first fragment has offset zero.

 

 

IP Type of Service

The Type of Service provides an indication of the abstract

    parameters of the quality of service desired.  These parameters are

    to be used to guide the selection of the actual service parameters

    when transmitting a datagram through a particular network.  Several

    networks offer service precedence, which somehow treats high

    precedence traffic as more important than other traffic (generally

    by accepting only traffic above a certain precedence at time of high

    load).  The major choice is a three way tradeoff between low-delay,

    high-reliability, and high-throughput.

   Bits 0-2:  Precedence.

      Bit    3:  0 =Normal Delay,      1 =Low Delay.

      Bits   4:  0 =Normal Throughput, 1 =High Throughput.

      Bits   5:  0 =Normal Relibility, 1 =High Relibility.

      Bit  6-7:  Reserved for Future Use.

 

 

IP TTL

This field indicates the maximum time the datagram is allowed to

    remain in the internet system.  If this field contains the value

    zero, then the datagram must be destroyed.  This field is modified

    in internet header processing.  The time is measured in units of

    seconds, but since every module that processes a datagram must

    decrease the TTL by at least one even if it process the datagram in

    less than a second, the TTL must be thought of only as an upper

    bound on the time a datagram may exist.  The intention is to cause

    undeliverable datagrams to be discarded, and to bound the maximum

    datagram lifetime.

 

IP Version

The Version field indicates the format of the internet header.  This  document describes version 4.

 

IPV4 (Internet Protocol version 4)

Internet Protocol version 4 (IPv4) is the fourth iteration of the Internet Protocol (IP) and it is the first version of the protocol to be widely deployed. IPv4 is the dominant network layer protocol on the Internet and apart from IPv6 it is the only standard internet work-layer protocol used on the Internet.

 

IPV6 (Internet Protocol version 6)

Due to recent concerns over the impending depletion of the current pool of Internet addresses and the desire to provide additional functionality for modern devices, an upgrade of the current version of the Internet Protocol (IP), called IPv4, has been standardized. This new version, called IP version 6 (IPv6), resolves unanticipated IPv4 design issues and takes the Internet into the 21st Century.

This paper describes the problems of the IPv4 Internet and how they are addressed by IPv6, IPv6 addressing, the new IPv6 header and its extensions, the IPv6 replacements for the Internet Control Message Protocol (ICMP) and Internet Group Management Protocol (IGMP), neighboring node interaction, IPv6 address auto configuration, and IPv6 routing. This paper provides a foundation of Internet standards-based IPv6 concepts and is intended for network engineers and support professionals who are already familiar with basic networking concepts and TCP/IP.

 

ISDN

ISDN is an abbreviation for Integrated Services Digital Network. It is the next-generation, digital telephone network that integrates circuit-switched voice and data services over a common access facility. There are two types of ISDN lines. Basic Rate ISDN (BRI) is designed for residential customers and small businesses. Primary Rate ISDN (PRI) is designed for larger businesses.?/span>

Intranet

The Internet has captured world attention in recent years. In reality, growth of internal networks based on Internet technologies known as the Intranet is outpacing the growth of the global Internet itself.

An Intranet is a company-specific network that uses software programs based on the Internet TCP/IP protocol and common Internet user interfaces such as the web browser. Simply put, an Intranet is the application of Internet technologies within an organization private LAN or WAN network.

Intrusion Detection System

An intrusion detection system (IDS) inspects all inbound and outbound network activity and identifies suspicious patterns that may indicate a network or system attack from someone attempting to break into or compromise a system.

Internet

The Internet is a worldwide, publicly accessible series of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP). It is a "network of networks" that consists of millions of smaller domestic, academic, business, and government networks, which together carry various information and services, such as electronic mail, online chat, file transfer, and the interlinked web pages and other resources of the World Wide Web (WWW).                  

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L

localhost

In TCP/IP networks, localhost is the name used to describe the local computer address. Localhost always translates to the loopback IP address 127.0.0.1.

Lost packets

Sax2 failed to capture the packets.

Local area network

A LAN is a high-speed data network that covers a relatively small geographic area. It typically connects workstations, personal computers, printers, servers, and other devices. LANs offer computer users many advantages, including shared access to devices and applications, file exchange between connected users, and communication between users via electronic mail and other applications.

Log File

The files were born in storage applications, services, or operating system. The information is used to track the implementation of the operation. For example, Web server maintenance list all log files issued by the server. The log file is usually plain text (ASCII) and have a . log extension.

In "Backup", recorded the creating date of tape, successful backup and restore files, and directories of files. "Performance logs and alert" service also will create a log file.

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M

MAC (Message Authentication Code)

 The MAC address is a unique value associated with a network adapter. MAC addresses are also known as hardware addresses or physical addresses. They uniquely identify an adapter on a LAN.

MAC addresses are 12-digit hexadecimal numbers (48 bits in length). By convention, MAC addresses are usually written in one of the following two formats:

MM:MM:MM:SS:SS:SS

MM-MM-MM-SS-SS-SS

The first half of a MAC address contains the ID number of the adapter manufacturer. These IDs are regulated by an Internet standards body (see sidebar). The second half of a MAC address represents the serial number assigned to the adapter by the manufacturer. In the example,

00:A0:C9:14:C8:29

The prefix

00A0C9

indicates the manufacturer is Intel Corporation.

 

Memory

Computers and many electronic gadgets usually rely on stored information which is mainly data which can be used to direct circuit afctions. The digital information is stored in memory devices. Memories can be divided into 2 categories based on what memory cells can be accessed at a given instant. SAM (Sequentially Access Memory) is accessed by stepping through each memory location until the desired location is reached. Magnetic tape is an example of SAM. The second category of memory devies is called RAM (Random Access Memory) where the memory can be randomly accessed at any instant, without having to step through each memory location. It is generally faster to access a RAM compared to SAM. Most of the electronics gadgets memory are of RAM type. 

Max Packet Size

The Max size of captured data packet.

Min Packet Size

The Min size of captured data packet.

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N

DNS Server

A DNS server is any computer registered to join the Domain Name System. A DNS server runs special-purpose networking software, features a public IP address, and contains a database of network names and addresses for other Internet hosts.

NETBIOS (Network Basic Input/Output System)

NetBIOS stands for Network Basic Input Output System and defines a software interface, very much like a programming API, offering a standard method for the provision and use of network services. It must be noted though that NetBIOS is not a protocol but it does have a base of rules such as naming conventions - for the naming of computers, workgroups, domains, users and other services.

Network

In information technology, a network is a series of points or nodes interconnected by communication paths. Networks can interconnect with other networks and contain subnetworks.

The most common topology or general configurations of networks include the bus, star, Token Ring, and mesh topologies. Networks can also be characterized in terms of spatial distance as local area networks (LANs), metropolitan area networks (MANs), and wide area networks (WANs). 

A given network can also be characterized by the type of data transmission technology in use on it (for example, a TCP/IP or Systems Network Architecture network); by whether it carries voice, data, or both kinds of signals; by who can use the network (public or private); by the usual nature of its connections (dial-up or switched, dedicated or nonswitched, or virtual connections); and by the types of physical links (for example, optical fiber, coaxial cable, and Unshielded Twisted Pair). Large telephone networks and networks using their infrastructure (such as the Internet) have sharing and exchange arrangements with other companies so that larger networks are created.  

Network protocol

A network protocol defines rules and conventions for communication between network devices. Protocols for computer networking all generally use packet switching techniques to send and receive messages in the form of packets.

Network protocols include mechanisms for devices to identify and make connections with each other, as well as formatting rules that specify how data is packaged into messages sent and received. Some protocols also support message acknowledgement and data compression designed for reliable and/or high-performance network communication. Hundreds of different computer network protocols have been developed each designed for specific purposes and environments.

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O

Options method

The OPTIONS method represents a request for information about the communication options available on the request/response chain identified by the Request-URI. This method allows the client to determine the options and/or requirements associated with a resource, or the capabilities of a server, without implying a resource action or initiating a resource retrieval.

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P

Peer host

Through peer to peernetwork technology, and exchanges the data directly with host without a relay equipment or services on another host.

Peer host groups

Through peer to peernetwork technology?/span>and exchanges the data with host directly without a relay equipment or services on another host group.

Port

A port number is a way to identify a specific process to which an Internet or other network message is to be forwarded when it arrives at a server. For the Transmission Control Protocol and the User Datagram Protocol, a port number is a 16-bit integer that is put in the header appended to a message unit. This port number is passed logically between client and server transport layers and physically between the transport layer and the Internet Protocol layer and forwarded on.

Put Method

 The PUT method is defined to store the request body at the location specified by the Request-URI.

POP3

POP (Post Office Protocol) is used to provide simple remote access to mailboxes. POP3 is the latest version of POP. With POP3, once mail clients connect and download their messages, the messages are typically removed from the server and stored on the client's local machine.

Post method

The POST method is used to request that the origin server accept the entity enclosed in the request as a new subordinate of the resource identified by the Request-URI in the Request-Line.

Packet

A packet is the unit of data that is routed between an origin and a destination on the Internet or any other packet-switched network. 

Packet Buffer

As same as the cache, equipment or region which be used for storage the data packets temporarily and receive data at different speeds.

Packet size

Description of the packet size.

Protocol

A uniform set of rules that enable two devices to connect and transmit data to one another. Protocols determine how data are transmitted between computing devices and over networks. They define issues such as error control and data compression methods. The protocol determines the following: type of error checking to be used, data compression method (if any), how the sending device will indicate that it has finished a message and how the receiving device will indicate that it has received the message. Internet protocols include TCP/IP (Transfer Control Protocol/Internet Protocol), HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), and SMTP (Simple Mail Transfer Protocol).

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R

Router

Routers are physical devices that join multiple wired or wireless networks together. Technically, a wired or wireless router is a Layer 3 gateway, meaning that the wired/wireless router connects networks (as gateways do), and that the router operates at the network layer of the OSI model.  

RFC

The abbreviation of Request for Comments, and the name be used when research and development DoD / TCP protocol. 

Referrer

The referer, or HTTP refe er, identifies, from the point of view of an internet webpage or resource, the address of the webpage (commonly the URL, the more generic URI or the i18n updated IRI) of the resource which links to it. By checking the referer, the new page can see where the request came from. Referer logging is used to allow websites and web servers to identify where people are visiting them from, for promotional or security purposes. Referer is a popular tool to combat Cross-site request forgery, but such security mechanisms do not work when the referer is disabled. Referer is widely used for statistical purposes.

Response

In Windows remote access, the equipment is expected to issue the orders d Series from equipment, including the Macro Command.

Response Message

Receive a response the information for a service request from a network system.

Ring Buffer

It is a limited amount cache memory. When it is full, it will be kept the new data rate, and discard the most outdated data.

Remote Computer

A remote computer is a computer to which a user does not have physical access, but which he or she can access/manipulate via some kind of network.

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S

Scope

Through DHCP services, let customers get machine's IP address range automatically.

Server

A computer, or a software package, that provides a specific kind of service to client software running on other computers.

Session

In telecommunication, a session is a series of interactions between two communication end points that occur during the span of a single connection. Typically, one end point requests a connection with another specified end point and if that end point replies agreeing to the connection, the end points take turns exchanging commands and data ("talking to each other"). The session begins when the connection is established at both ends and terminates when the connection is ended.

Source IP

IP address of the host which sent the data packet.

SMTP

 SMTP (Simple Mail Transfer Protocol) is a TCP/IP protocol used in sending and receiving e-mail. However, since it's limited in its ability to queue messages at the receiving end, it's usually used with one of two other protocols, POP3 or Internet Message Access Protocol, that let the user save messages in a server mailbox and download them periodically from the server. In other words, users typically use a program that uses SMTP for sending e-mail and either POP3 or IMAP for receiving messages that have been received for them at their local server. Most mail programs such as Eudora let you specify both an SMTP server and a POP server. On UNIX-based systems, send mail is the most widely-used SMTP server for e-mail. A commercial package, Send mail, includes a POP3 server and also comes in a version for Windows NT.  

Switching Hub

A network switch is a small hardware device that joins multiple computers together within one local area network (LAN). Technically, network switches operate at layer two (Data Link Layer) of the OSI model.

Source Mac

MAC address of the host which sent the data packet.

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T

TTL

In IPv4, time to live (TTL) is an 8-bit field in the Internet Protocol (IP) header. It is the 9th octet of 20. The time to live value can be thought of as an upper bound on the time that an IP datagram can exist in an internet system. The TTL field is set by the sender of the datagram, and reduced by every host on the route to its destination. If the TTL field reaches zero before the datagram arrives at its destination, then the datagram is discarded and an ICMP error datagram (11 - Time Exceeded) is sent back to the sender. The purpose of the TTL field is to avoid a situation in which an undeliverable datagram keeps circulating on an internet system, and such a system eventually becoming swamped by such immortal datagrams. In theory, time to live is measured in seconds, although every host that passes the datagram must reduce the TTL by at least one unit. In practice, the TTL field is reduced by one on every hop. To reflect this practice, the field is named hop limit in IPv6.

Traffic

The load on a communications device or system. One of the principal jobs of a system administrator is to monitor traffic levels and take appropriate actions when traffic becomes heavy. 

TCP/IP Protocol

TCP/IP (Transmission Control Protocol/Internet Protocol) is the basic communication language or protocol of the Internet. It can also be used as a communications protocol in a private network (either an intranet or an extranet). When you are set up with direct access to the Internet, your computer is provided with a copy of the TCP/IP program just as every other computer that you may send messages to or get information from also has a copy of TCP/IP. 

TCP/IP is a two-layer program. The higher layer, Transmission Control Protocol, manages the assembling of a message or file into smaller packets that are transmitted over the Internet and received by a TCP layer that reassembles the packets into the original message. The lower layer, Internet Protocol, handles the address part of each packet so that it gets to the right destination. Each gatewaycomputer on the network checks this address to see where to forward the message. Even though some packets from the same message are routed differently than others, they'll be reassembled at the destination. 

Trace method

The TRACE method is used to invoke a remote, application-layer loop- back of the request message. The final recipient of the request SHOULD reflect the message received back to the client as the entity-body of a 200 (OK) response. The final recipient is either the  

Transaction

In computer programming, a transaction usually means a sequence of information exchange and related work (such as database updating) that is treated as a unit for the purposes of satisfying a request and for ensuring database integrity. For a transaction to be completed and database changes to made permanent, a transaction has to be completed in its entirety. A typical transaction is a catalog merchandise order phoned in by a customer and entered into a computer by a customer representative. The order transaction involves checking an inventory database, confirming that the item is available, placing the order, and confirming that the order has been placed and the expected time of shipment. If we view this as a single transaction, then all of the steps must be completed before the transaction is successful and the database is actually changed to reflect the new order. If something happens before the transaction is successfully completed, any changes to the database must be kept track of so that they can be undone. 

Telnet (Telnet Protocol)

Telnet is a user command and an underlying TCP/IP protocol for accessing remote computers. Through Telnet, an administrator or another user can access someone else's computer remotely. On the Web, HTTP and FTP protocols allow you to request specific files from remote computers, but not to actually be logged on as a user of that computer. With Telnet, you log on as a regular user with whatever privileges you may have been granted to the specific application and data on that computer.

Terminal

In networking, a terminal is a personal computer or workstation connected to a mainframe. The personal computer usually runs terminal emulation software that makes the mainframe think it is like any other mainframe terminal. 

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U

UDP

UDP (User Datagram Protocol) is a communications protocol that offers a limited amount of service when messages are exchanged between computers in a network that uses the Internet Protocol (IP). UDP is an alternative to the Transmission Control Protocol (TCP) and, together with IP, is sometimes referred to as UDP/IP. Like the Transmission Control Protocol, UDP uses the Internet Protocol to actually get a data unit (called a datagram) from one computer to another. Unlike TCP, however, UDP does not provide the service of dividing a message into packets (datagrams) and reassembling it at the other end. Specifically, UDP doesn't provide sequencing of the packets that the data arrives in. This means that the application program that uses UDP must be able to make sure that the entire message has arrived and is in the right order. Network applications that want to save processing time because they have very small data units to exchange (and therefore very little message reassembling to do) may prefer UDP to TCP. The Trivial File Transfer Protocol (TFTP) uses UDP instead of TCP.

UDP provides two services not provided by the IP layer. It provides port numbers to help distinguish different user requests and, optionally, a checksum capability to verify that the data arrived intact. 

In the Open Systems Interconnection (OSI) communication model, UDP, like TCP, is in layer 4, the Transport Layer. 

Unicode

Unicode provides
a unique number for every character,
no matter what the platform,
no matter what the program,
no matter what the language.

Fundamentally, computers just deal with numbers. They store
letters and other characters by assigning a number for each one. Before Unicode
was invented, there were hundreds of different encoding systems for assigning
these numbers. No single encoding could contain enough characters: for example,
the European Union alone requires several different encodings to cover all its
languages. Even for a single language like English no single encoding was
adequate for all the letters, punctuation, and technical symbols in common use.

These encoding systems also conflict with one another. That
is, two encodings can use the same number for two different characters,
or use different numbers for the same character. Any given computer
(especially servers) needs to support many different encodings; yet whenever
data is passed between different encodings or platforms, that data always runs
the risk of corruption.

URL

A URL (Uniform Resource Locator, previously Universal Resource Locator) - usually pronounced by sounding out each letter but, in some quarters, pronounced "Earl" - is the unique address for a file that is accessible on the Internet. A common way to get to a Web site is to enter the URL of its home page file in your Web browser's address line. However, any file within that Web site can also be specified with a URL. Such a file might be any Web (HTML) page other than the home page, an image file, or a program such as a common gateway interface application or Java applet. The URL contains the name of the protocol to be used to access the file resource, a domain name that identifies a specific computer on the Internet, and a pathname, a hierarchical description that specifies the location of a file in that computer.

User agent

A user agent is the client application used with a particular network protocol; the phrase is most commonly used in reference to those which access the World Wide Web, but other systems such as SIP uses the term user agent to refer to the user's phone. Web user agents range from web browsers and e-mail clients to search engine crawlers ("spiders"), as well as mobile phones, screen readers and braille browsers used by people with disabilities. When Internet users visit a web site, a text string is generally sent to identify the user agent to the server. This forms part of the HTTP request, prefixed with User-Agent: (case does not matter) and typically includes information such as the application name, version, host operating system, and language. Bots, such as web crawlers, often also include a URL and/or e-mail address so that the webmaster can contact the operator of the bot.

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V

Virtual IP Address

 A virtual IP address (VIP or VIPA) is an IP address that is not connected to a specific computer or network interface card (NIC) on a computer. Incoming packets are sent to the VIP address, but all packets travel through real network interfaces.

VIPs are mostly used for connection redundancy; a VIP address may still be available if a computer or NIC fails because an alternative computer or NIC replies to connections.

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W

WAN

Stands for "Wide Area Network." It is similar to a Local Area Network (LAN), but it's a lot bigger. Unlike LANs, WANs are not limited to a single location. Many wide area networks span long distances via telephone lines, fiber-optic cables, or satellite links. They can also be composed of smaller LANs that are interconnected. The Internet could be described as the biggest WAN in the world. You could even call the Internet a Super WAN BAM if you wanted to. Or maybe not.

Web

The World Wide Web (commonly shortened to the Web) is a system of interlinked hypertext documents accessed via the Internet. With a Web browser, a user views Web pages that may contain text, images, videos, and other multimedia and navigates between them using hyperlinks. The World Wide Web was created in 1989 by Sir Tim Berners-Lee, working at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland and released in 1992. Since then, Berners-Lee has played an active role in guiding the development of Web standards (such as the markup languages in which Web pages are composed), and in recent years has advocated his vision of a Semantic Web.

Web Access

The operation which means visiting the Web.

Web Server

A computer program that is responsible for accepting HTTP requests from web clients, which are known as web browsers, and serving them HTTP responses along with optional data contents, which usually are web pages such as HTML documents and linked objects (images, etc.).

A computer that runs a computer program as described above.

Word Wrap

Word wrap or line wrap is the feature, supported by most text editors, word processors, and web browsers, of automatically replacing some of the blank spaces between words by line breaks, such that each line fits in the viewable window, allowing text to be read from top to bottom without any horizontal scrolling.

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X

XML (Extensible Markup Language)

 The Extensible Markup Language (XML) is a general-purpose specification for creating custom markup languages.[1] It is classified as an extensible language because it allows its users to define their own elements. Its primary purpose is to facilitate the sharing of structured data across different information systems, particularly via the Internet,[2] and it is used both to encode documents and to serialize data. In the latter context, it is comparable with other text-based serialization languages such as JSON and YAML.

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