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GLOSSARY

PABX - PRIVATE AUTOMATIC BRANCH EXCHANGE
PACKET
PACKET MONKEY
PACKET-SWITCHED
PASSIVE FTP or PASV FTP
PON - PASSIVE OPTICAL NETWORK
PATCH PANEL
PBX - PRIVATE BRANCE EXCHANGE
PCMCIA
PDF
PEER-TO-PEER
PEERING
PVC - PRIVATE VIRTUAL CIRCUIT
PERSONAL FIREWALL
PHP - PERSONAL HOME PAGE
PHYSICAL LAYER
PING
PING STORM
POTS - PLAIN OLD TELEPHONE SERVICE
POP - POINT OF PRESENCE
PPP - POINT-TO-POINT PROTOCOL
PPTP - POINT-TO-POINT TUNNELING PROTOCOL
POP3 - POST OFFICE PROTOCOL 3
PORT
PORT 80
PORTAL
PREDICTIVE DIALER
PRI - PRIMARY RATE INTERFACE
PROVISIONING
PROXY SERVER
PSTN - PUBLIC SWITCHED TELEPHONE NETWORK
PUBLIC KEY CERTIFICATE


• PABX Private Automatic Branch Exchange, is an automatic telephone switching system within a private enterprise. Originally, such systems - called private branch exchanges (PBX) - required the use of a live operator. Since almost all private branch exchanges today are automatic, the abbreviation "PBX" usually implies a "PABX."
  Some manufacturers of PABX (PBX) systems distinguish their products from others by creating new kinds of private branch exchanges. Rolm offers a Computerized Branch Exchange (CABX) and Usha Informatics offers an Electronic Private Automatic Branch Exchange (EPABX).
  

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• PACKET is the unit of data that is routed between an origin and a destination on the Internet or any other packet-switched network. When any file (e-mail message, HTML file, Graphics Interchange Format file, Uniform Resource Locator request, and so forth) is sent from one place to another on the Internet, the Transmission Control Protocol (TCP) layer of TCP/IP divides the file into "chunks" of an efficient size for routing. Each of these packets is separately numbered and includes the Internet address of the destination. The individual packets for a given file may travel different routes through the Internet. When they have all arrived, they are reassembled into the original file (by the TCP layer at the receiving end).
  "Packet" and "datagram" are similar in meaning. A protocol similar to TCP, the User Datagram Protocol(UDP) uses the term datagram.
  

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• PACKET MONKEY is someone who intentionally inundates a Web site or network with data packets, resulting in a denial-of-service situation for users of the attacked site or network. Packet monkeys typically use tools created and made available on the Internet by hackers.
  According to one writer's distinction, a packet monkey, unlike a script kiddy, leaves no clues as to who is making the exploit, making the identity of a packet monkey more difficult to trace. In addition, a denial-of-service attack can be launched on a wider scale than attacks performed by script kiddies, making them more difficult to investigate.
  

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• PACKET-SWITCHED describes the type of network in which relatively small units of data called packets are routed through a network based on the destination address contained within each packet. Breaking communication down into packets allows the same data path to be shared among many users in the network. This type of communication between sender and receiver is known as connectionless (rather than dedicated). Most traffic over the Internet uses packet switching and the Internet is basically a connectionless network.
  

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• PASSIVE FTP (sometimes referred to as PASV FTP because it involves the FTP PASV command) is a more secure form of data transfer in which the flow of data is set up and initiated by the File Transfer Program (FTP) client rather than by the FTP server program. Separate FTP client programs, such as WS_FTP Pro, usually allow the user to select passive FTP. Most Web browsers (which act as FTP clients) use passive FTP by default because corporations prefer it as a safety measure. As a general rule, any coprorate firewall server, which exists in order to protect an internal network from the outside world, recognizes input from the outside only in response to user requests that were sent out requesting the input. The use of passive FTP ensures all data flow initiation comes from inside the network rather than from the outside.
       How It Works
       Using normal or passive FTP, a client begins a session by sending a request to communicate through TCP port 21, the port that is conventionally assigned for this use at the FTP server. This communication is known as the Control Channel connection.
       Using "normal" FTP communication, the client requestor also includes in the same PORT command packet on the Control Channel a second port number that is to be used when data is to be exchanged; the port-to-port exchange for data is known as the Data Channel. The FTP server then initiates the exchange from its own port 20 to whatever port was designated by the client. However, because the server-initiated communication is no longer controlled by the client and can't be correlated by a firewall to the initial request, the potential exists for uninvited data to arrive from anywhere posing as a normal FTP transfer.
       Using passive FTP, a PASV command is sent instead of a PORT command. Instead of specifying a port that the server can send to, the PASV command asks the server to specify a port it wishes to use for the Data Channel connection. The server replies on the Control Channel with the port number which the client then uses to initiate an exchange on the Data Channel. The server will thus always be responding to client-initiated requests on the Data Channel and the firewall can coorelate these.
  

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• PON Passive Optical Network, is a system that brings optical fiber cabling and signals all or most of the way to the end user. Depending on where the PON terminates, the system can be described as fiber-to-the-curb (FTTC), fiber-to-the-building (FTTB), or fiber-to-the-home (FTTH). A PON consists of an Optical Line Termination (OLT) at the communication company's office and a number of Optical Network Units (ONUs) near end users. Typically, up to 32 ONUs can be connected to an OLT. The passive simply describes the fact that optical transmission has no power requirements or active electronic parts once the signal is going through the network.
  

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• PATCH PANEL is a mounted hardware unit containing an assembly of port locations in a communications or other electronic or electrical system. In a network, a patch panel serves as a sort of static switchboard, using cables to interconnect computers within the area of a local area network (LAN) and to the outside for connection to the Internet or other wide area network (WAN). A patch panel uses a sort of jumper cable called a patch cord to create each interconnection.
  

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• PBX Private Branch Exchange, is a telephone system within an enterprise that switches calls between enterprise users on local lines while allowing all users to share a certain number of external phone lines. The main purpose of a PBX is to save the cost of requiring a line for each user to the telephone company's central office.
  The PBX is owned and operated by the enterprise rather than the telephone company (which may be a supplier or service provider, however). Private branch exchanges used analog technology originally. Today, PBXs use digital technology (digital signals are converted to analog for outside calls on the local loop using plain old telephone service).
  

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• PCMCIA card is a credit card-size memory or I/O device that connects to a personal computer, usually a notebook or laptop computer. Probably the most common example of a PCMCIA card is the 28.8 Kbps modem for notebook computers.
  

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• PDF (Portable Document Format) is a file format that has captured all the elements of a printed document as an electronic image that you can view, navigate, print, or forward to someone else. PDF files are created using Adobe Acrobat, Acrobat Capture, or similar products. To view and use the files, you need the free Acrobat Reader, which you can easily download. Once you've downloaded the Reader, it will start automatically whenever you want to look at a PDF file.
  

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• PEER-TO-PEER (referred to as P2P) is a type of transient Internet network that allows a group of computer users with the same networking program to connect with each other and directly access files from one another's hard drives. Napster and Gnutella are examples of this kind of peer-to-peer software. Corporations are looking at the advantages of using P2P as a way for employees to share files without the expense involved in maintaining a centralized server and as a way for businesses to exchange information with each other directly.
  

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• PEERING is the arrangement of traffic exchange between Internet service providers (ISPs). Larger ISPs with their own backbone networks agree to allow traffic from other large ISPs in exchange for traffic on their backbones. They also exchange traffic with smaller ISPs so that they can reach regional end points. Essentially, this is how a number of individual network owners put the Internet together. To do this, network owners and access providers, the ISPs, work out agreements that describe the terms and conditions to which both are subject. Bilateral peering is an agreement between two parties. Multilateral peering is an agreement between more than two parties.
  Peering requires the exchange and updating of router information between the peered ISPs, typically using the Border Gateway Protocol (BGP). Peering parties interconnect at network focal points such as the network access points (NAP) in the United States and at regional switching points.
  

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• PVC Permanent Virtual Circuit, is a software-defined logical connection in a network such as a frame relay network. A feature of frame relay that makes it a highly flexible network technology is that users (companies or clients of network providers) can define logical connections and required bandwidth between end points and let the frame relay network technology worry about how the physical network is used to achieve the defined connections and manage the traffic. In frame relay, the end points and a stated bandwidth called a Committed Information Rate (CIR) constitute a PVC, which is defined to the frame relay network devices. The bandwidth may not exceed the possible physical bandwidth. Typically, multiple PVCs share the same physical paths at the same time. To manage the variation in bandwidth requirements expressed in the CIRs, the frame relay devices use a technique called statistical multiplexing.
  

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• PERSONAL FIREWALL (sometimes called a desktop firewall) is a software application used to protect a single Internet-connected computer from intruders. Personal firewall protection is especially useful for users with "always-on" connections such as DSL or cable modem. Such connections use a static IP address that makes them especially vulnerable to potential hackers. Often compared to anti-virus applications, personal firewalls work in the background at the device (link layer) level to protect the integrity of the system from malicious computer code by controlling Internet connections to and from a user's computer, filtering inbound and outbound traffic, and alerting the user to attempted intrusions.
  

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• PHP Personal Home Page, is a script language and interpreter, similar to JavaScript and Microsoft's VBScript, that is freely available and used primarily on Linux Web servers. PHP (the initials come from the earliest version of the program, which was called "Personal Home Page Tools") is a cross-platform alternative to Microsoft's Active Server Page (ASP) technology (which runs only on Microsoft's Windows NT servers). As with ASP, the PHP script is embedded within a Web page along with its HTML. Before the page is sent to a user that has requested it, the Web server calls PHP to interpret and perform the operations called for in the PHP script. An HTML page that includes a PHP script is typically given a file name suffix of ".php" ".php3," or ".phtml". Like ASP, PHP can be thought of as "dynamic HTML pages," since content will vary based on the results of interpreting the script.
  

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• PHYSICAL LAYER in the Open Systems Interconnection (OSI) communications model, the physical layer supports the electrical or mechanical interface to the physical medium. For example, this layer determines how to put a stream of bits from the upper (data link) layer on to the pins for a parallel printer interface, an optical fiber transmitter, or a radio carrier.
  

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• PING is a basic Internet program that lets you verify that a particular IP address exists and can accept requests. The verb ping means the act of using the ping utility or command. Ping is used diagnostically to ensure that a host computer you are trying to reach is actually operating. If, for example, a user can't ping a host, then the user will be unable to use the File Transfer Protocol (FTP) to send files to that host. Ping can also be used with a host that is operating to see how long it takes to get a response back. Using ping, you can learn the number form of the IP address from the symbolic domain name.
  Tip: To find out the dot address (such as 65.215.31.31) for a given domain name, Windows users can go to their MS DOS prompt screen and enter: ping xxx.yyy where xxx is the second-level domain name like "cnsny" and yyy is the top-level domain name like "net").
  

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• PING STORM is a condition in which the Internet Packet program is used to send a flood of packets to a server to test its ability to handle a high amount of traffic or, maliciously, to make the server inoperable. Although the ping support in Windows operating systems does not allow someone to mount a ping storm, the ping command in at least some UNIX-based systems offers two options: "ping -f" which specifies to output ping packets back as fast as they are returned, and "ping -s]packetsize[", which causes the size of the outgoing packet to be padded by some specified size in order to increase the load on the receiving server.
  

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• POTS, Plain Old Telephone Service is a term sometimes used in discussion of new telephone technologies in which the question of whether and how existing voice transmission for ordinary phone communication can be accommodated. For example, Asymmetric Digital Subscriber Line (ADSL) and Integrated Services Digital Network (ISDN) connections provide some part of their channels for "Plain Old Telephone Service" while providing most of their bandwidth for digital data transmission.
  

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• POP Point-Of-Presence, is an access point to the Internet. A POP necessarily has a unique Internet Protocol (IP) address. Your Internet service provider (ISP) or online service provider (such as AOL) has a point-of-presence on the Internet and probably more than one. The number of POPs that an ISP or OSP has is sometimes used as a measure of its size or growth rate.
  A POP may actually reside in rented space owned by the telecommunications carrier (such as Sprint) to which the ISP is connected. A POP usually includes routers, digital/analog call aggregators, servers, and frequently frame relays or ATM switches.
  

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• PPP Point-to-Point Protocol, is a protocol for communication between two computers using a serial interface, typically a personal computer connected by phone line to a server. For example, your Internet server provider may provide you with a PPP connection so that the provider's server can respond to your requests, pass them on to the Internet, and forward your requested Internet responses back to you. PPP uses the Internet protocol (IP) (and is designed to handle others). It is sometimes considered a member of the TCP/IP suite of protocols. Relative to the Open Systems Interconnection (OSI) reference model, PPP provides layer 2 (data-link layer) service. Essentially, it packages your computer's TCP/IP packets and forwards them to the server where they can actually be put on the Internet.
  PPP is a full-duplex protocol that can be used on various physical media, including twisted pair or fiber optic lines or satellite transmission. It uses a variation of High Speed Data Link Control (HDLC) for packet encapsulation.
  PPP is usually preferred over the earlier de facto standard Serial Line Internet Protocol (SLIP) because it can handle synchronous as well as asynchronous communication. PPP can share a line with other users and it has error detection that SLIP lacks. Where a choice is possible, PPP is preferred.
  

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• PPTP, Point-To-Piont Tunneling Protocol, is a protocol (set of communication rules) that allows corporations to extend their own corporate network through private "tunnels" over the public Internet. Effectively, a corporation uses a wide-area network as a single large local area network. A company no longer needs to lease its own lines for wide-area communication but can securely use the public networks. This kind of interconnection is known as a virtual private network (VPN).
  PPTP, a proposed standard sponsored by Microsoft and other companies, and Layer 2 Tunneling Protocol, proposed by Cisco Systems, are among the most likely proposals as the basis for a new Internet Engineering Task Force (IETF) standard. With PPTP, which is an extension of the Internet's Point-to-Point Protocol (PPP), any user of a PC with PPP client support is able to use an independent service provider (ISP) to connect securely to a server elsewhere in the user's company.
  

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• POP3 Post Office Protocol 3, is the most recent version of a standard protocol for receiving e-mail. POP3 is a client/server protocol in which e-mail is received and held for you by your Internet server. Periodically, you (or your client e-mail receiver) check your mail-box on the server and download any mail. POP3 is built into the Netmanage suite of Internet products and one of the most popular e-mail products, Eudora. It's also built into the Netscape and Microsoft Internet Explorer browsers.
  An alternative protocol is Internet Message Access Protocol (IMAP). With IMAP, you view your e-mail at the server as though it was on your client computer. An e-mail message deleted locally is still on the server. E-mail can be kept on and searched at the server.
  POP can be thought of as a "store-and-forward" service. IMAP can be thought of as a remote file server.
  POP and IMAP deal with the receiving of e-mail and are not to be confused with the Simple Mail Transfer Protocol (SMTP), a protocol for transferring e-mail across the Internet. You send e-mail with SMTP and a mail handler receives it on your recipient's behalf. Then the mail is read using POP or IMAP.
  

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• PORT is a "logical connection place" and specifically, using the Internet's protocol, TCP/IP , the way a client program specifies a particular server program on a computer in a network. Higher-level applications that use TCP/IP such as the Web protocol, Hypertext Transfer Protocol , have ports with preassigned numbers. These are known as "well-known ports" that have been assigned by the Internet Assigned Numbers Authority (IANA). Other application processes are given port numbers dynamically for each connection. When a service (server program) initially is started, it is said to bind to its designated port number. As any client program wants to use that server, it also must request to bind to the designated port number.
  Port numbers are from 0 to 65536. Ports 0 to 1024 are reserved for use by certain privileged services. For the HTTP service, port 80 is defined as a default and it does not have to be specified in the Uniform Resource Locator (URL).
  

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• PORT 80 on a Web server or Hypertext Transfer Protocol daemon , port 80 is the port that the server "listens to" or expects to receive from a Web client, assuming that the default was taken when the server was configured or set up.
  A port can be specified in the range from 0-65536 on the NCSA server. However, the server administrator configures the server so that only one port number can be recognized. By default, the port number for a Web server is 80.
  

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• PORTAL is a term, generally synonymous with gateway, for a World Wide Web site that is or proposes to be a major starting site for users when they get connected to the Web. There are general portals and specialized or niche portals. Some major general portals include Yahoo, Excite, Netscape, Lycos, CNET, Microsoft Network, and America Online's AOL.com. Examples of niche portals include Garden.com (for gardeners) and Fool.com (for investors).
  

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• PREDICTIVE DIALER is a telephone control system that automatically calls a list of telephone numbers in sequence and screens out no-answers, busy signals, answering machines, and disconnected numbers while predicting at what point a human caller will be able to handle the next call. Predictive dialers are commonly used for telemarketing, surveys, appointment confirmation, payment collection, and service follow-ups. Sellers of predictive dialer systems claim that they greatly increase caller productivity. The phone calls you receive from "no one there" are often predictive dialer calls in which a manual caller isn't ready yet.
  Not to be confused with an automatic dialer, a predictive dialer is programmed to predict when a human caller is available to pick up a call, A somewhat related system is the lead generator, which dials a list of telephone numbers and, when a live voice answers, delivers a recorded message.
  

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• PRI Primary Rate Interface channels are carried on a T-carrier system line (in the U.S., Canada, and Japan) or an E-carrier line (in other countries) and are typically used by medium to large enterprises. The 23 (or 30) B-channels can be used flexibly and reassigned when necessary to meet special needs such as videoconferences. The Primary Rate user is hooked up directly to the telephone company central office.
  The Basic Rate Interface consists of two 64 Kbps B-channels and one 16 Kbps D-channel. Thus, a Basic Rate Interface user can have up to 128 Kbps service. The Primary Rate Interface consists of 23 B-channels and one 64 Kpbs D-channel using a T-1 line or 30 B-channels and 1 D-channel using an E1 line. Thus, a Primary Rate Interface user on a T-1 line can have up to 1.544 Mbps service or up to 2.048 Mbps service on an E1 line. PRI uses the Q.931 protocol over the D-channel.
  

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• PROVISIONING means "providing". In telecommunications terminology, provisioning means providing a product or service, such as wiring or bandwidth. The term has a number of varied meanings when used in telecommunications:
  1) Providing telecommunications service to a user, including everything necessary to set up the service, such as equipment, wiring, and transmission.
  2) Used as a synonym for configuring, as in "Telecommunications lines must be correctly provisioned to work with the customer's equipment and enabled for various options the customer has chosen."
  3) In a traditional telecommunications environment, there are three separate types of provisioning: circuit provisioning, service provisioning, and switch provisioning.
  4) In a wireless environment, provisioning refers to service activation and involves programming various network databases with the customer's information.
  5) In a slightly different sense, network provisioning systems are intermediary systems that are used to provide customer services, log transactions, carry out requests, and update files.
  6) Provisioning is the fourth step of the telecommunications sequence called OAM&P: Operations, Administration, Maintenance, and Provisioning.
  

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• PROXY SERVER is a server that acts as an intermediary between a workstation user and the Internet so that the enterprise can ensure security, administrative control, and caching service. A proxy server is associated with or part of a gateway server that separates the enterprise network from the outside network and a firewall server that protects the enterprise network from outside intrusion.
  

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• PSTN, Public Switched Telephone Network is the world's collection of interconnected voice-oriented public telephone networks, both commercial and government-owned. It's also referred to as the Plain Old Telephone Service (POTS).
  

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• PUBLIC KEY CERTIFICATE is a digitally signed document that serves to validate the sender's authorization and name. The document consists of a specially formatted block of data that contains the name of the certificate holder (which may be either a user or a system name) and the holder's public key, as well as the digital signature of a certification authority for authentication. The certification authority attests that the sender's name is the one associated with the public key in the document. A user ID packet, containing the sender's unique identifier, is sent after the certificate packet.
  

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