Glossary of Terms and Acronyms

ABR (Available Bit Rate): ABR is an ATM bandwidth-allocation service that adjusts the amount of bandwidth based on the amount of traffic in the network. ABR service provides a guaranteed minimum bandwidth capacity but allows data to be bursted at higher capacities when the network is free.

AHT (Average Hold Time): The average length of time between the moment a caller finishes dialling and the moment the call is answered.

ANI (Automatic Number Identification): A telephone function that transmits the billing number of the incoming call (Caller ID, for example).

AS (Autonomous System): A group of networks under mutual administration that share the same routing methodology. An AS uses an internal gateway protocol and common metrics to route Packets within the AS, and uses an external gateway protocol to route packets to other ASs.

ASP (Application Service Provider):
An independent, third-party provider of software-based services delivered to customers across a wide area network (WAN).

ASR (Answer-Seizure Ratio): The ratio of successfully connected calls to attempted calls (also called 'Call Completion Rate'). ASRs vary by routes. A typical ASR to Pakistan is lower than that of Germany. Reasons for this include the quality of the network and the fact that it's less likely that a call to Pakistan will encounter a device such as an answering machine. Built-in IPCB.net QoS Management Tools track the ASRs for all termination facilities that receive calls routed through the IPCB.net.

ATA(Analog Telephone Adapter): In our world ATA refers to am adapter positioned between your POT (Plain Old Telephone). This device is a small box that enables a POT to become a VoIP endpoint.

ATM (Asynchronous Transfer Mode):
ATM is network technology based on transferring data in cells or packets of fixed size. The cell used with ATM is relatively small (53 bytes) compared to the units used with older technologies. The small, constant cell size allows ATM equipment to multiplex efficiently video, audio, and computer data over the same network.

Backbone: A very-high-speed network spanning the world from one major metropolitan area to another. Such networks are typically provided by national Internet Service Providers (ISPs). Local ISPs connect to the backbone in order to transport data.
Bad Frame Interpolation: Bad Frame Interpolation interpolates lost/corrupted packets by using the previously received voice frames. It increases voice quality by making the voice transmission more robust in bursty error environments.

Bandwidth: The maximum data carrying capacity of a transmission link. For data networks, bandwidth is usually expressed in bits per second (bps).

BRI (Basic-Rate Interface): the basic ISDN configuration, which consists of two B-channels that can carry voice or data at rate of 64Kbps, and one D-channel, which carries call-control information. Another type of ISDN configuration is called Primary-Rate Interface (PRI), which consists of 23 B-channels (30 in Europe) and one D-channel.

Buffer: A temporary data storage area, usually in RAM. The purpose of most buffers is to act as a holding area, enabling the CPU to manipulate data before transferring it to a device. Because the processes of reading and writing data to a disk are relatively slow, many programs keep track of data changes in a buffer and then copy the buffer to a disk. For example, word processors employ a buffer to keep track of changes to files. Then when you save the file, the word processor updates the disk file with the contents of the buffer. This is much more efficient than accessing the file on the disk each time you make a change to the file.

Call: Establishment of (or an attempt to establish) voice connection between two endpoints, or between two points which provide a partial link (e.g. a trunk) between two endpoints.

Call Deflection: Call Diversion or Call Forwarding allows a called endpoint to redirect the unanswered call to another endpoint.

CBR (Constant Bit Rate): often referred to as Class A quality of service. CBR is an ATM bandwidth-allocation service that requires the user to determine a fixed bandwidth requirement at the time the connection is set up so that the data can be sent in a steady stream. CBR service is often used when transmitting fixed-rate uncompressed video.

CDR (Call Detail Record): Information regarding a single call collected from the switch and available as an automatically generated downloadable report for a requested time period. The report contains information on the number of calls, call duration, call origination and destination, and billed amount. IPCB.net Members use CDR reports to bill retail customers and settle with their partners on a wholesale level.

CENTREX (Central office EXchange service): a type of PBX service in which switching occurs at a local telephone station instead of at the company premises. Typically, the telephone company owns and manages all the communications equipment necessary to implement the PBX and then sells various services to the company.

CLEC (Competitive Local Exchange Carrier): A telephone company that competes with an incumbent local exchange carrier (ILEC), such as a Regional Bell Operating Company (RBOC), GTE, ALLNET, Telus, Allstream etc. With the passage of the Telecommunications Act of 1996, there has been an explosion in the number of CLECs. The Act allows companies with CLEC status to use ILEC infrastructure in two ways: 1) Access to UNEs - Important to CLEC telecommunications networking is the availability of unbundled network elements or UNEs (through a collocation arrangement). UNEs are defined by the Act as any "facility or equipment used in the provision of a telecommunications service," as well as "features, functions, and capabilities that are provided by means of such facility or equipment." For CLECs the most important UNE available to them is the local loop, which connects the ILEC switches to the ILEC's present customers. With the local loop, CLECs will be able to connect their switches with the ILEC's switches, thus giving them access to ILEC customers.2) Resale - Another option open to CLECs is the resale strategy. The Act states that any telecommunications services ILECs offer at retail, must be offered to CLECs at a wholesale discount. This saves the CLEC from having to invest in switches, fiber optic transmission facilities, or collocation arrangements. In any case, a CLEC may decide on one or the other or even both. CLEC status is very beneficial, especially for ISPs, who may easily get access to the copper loops and other switching elements necessary to provide xDSL services.

Codec: The term codec is a contraption of COder and DECoder. The codec is where the analog to digital transformation is performed. In the PSTN, the Pulse Code Modulation (PCM) scheme is used to generate a 64kbps stream. More “economical” coding schemes have been designed to reduce this stream to 32, 16, and even 8 kbps. The main ITU codec standards are G.711, G.722, G.726, G.728, G.729, G.723. This reduction in the number of kbps required comes at the price of reduced quality of the voice signal, thus a required trade-off between bandwidth and quality of service.

Connection-Oriented: Mode of communication in which a connection must be established between the transmitter and receiver before transmission of user data. This can be done by switching a circuit or by setting up a logical channel. A well-known connection-oriented protocol is TCP. Connection-oriented is the opposite of connectionless.

Connectionless: Mode of communication in which a connection (circuit or logical channel) does not need to be set up for data transmission between the transmitter and receiver. It is the underlying protocol for packet-switched transmission. The individual data packets can go from the transmitter to the receiver via different paths. A well-known connectionless protocol is UDP.

DHCP (Dynamic Host Configuration Protocol): A protocol for assigning dynamic IP addresses to devices on a network. With dynamic addressing, a device can have a different IP address every time it connects to the network. In some systems, the device's IP address can even change while it is connected. DHCP also supports a mix of static and dynamic IP addresses.

Dynamic addressing simplifies network administration because the software keeps track of IP addresses rather than requiring an administrator to manage the task. This means that a new computer can be added to a network without the hassle of manually assigning it a unique IP address. Many ISPs use dynamic IP addressing for dial-up users.

Dial-peer: Addressable call endpoint -- a software structure that binds a dialed digit string to a voice port or IP address of the destination gateway. Several dial peers always exist on each router in the network, and at least two will be involved in making a call across the network, one on the originating end and one on the terminating end. In Voice over IP, there are two kinds of dial peers: POTS and VoIP. VoIP peers point to specific VoIP devices.

Dial-peer hunting: Process when the originating router tries to establish call on different dial peers if the originating router receives a user-busy invalid number or an unassigned-number disconnect cause code from a destination router.

DID (Direct Inward Dialling): Traditionally a DID is a PBX that has been given individual phone numbers which is different than extensions from one central phone number. The same is possible with VoIP.

DiffServ (Differentiated Services): is a QoS (quality of service) protocol for routers that prioritizes IP voice over other data traffic to help preserve voice quality even when network traffic is heavy.

DLC (Digital Loop Carrier): A system for transmitting digital multiplexed data signals using existing cabling for distribution. The digital loop carrier begins the transmission at the central office on a high-speed digital line, such as T1, and routes the transmission to a remote digital terminal, which then converts the signal into a form that can be passed on to low-speed lines for routing to the end users telephone or computer. The process is reversed when transmissions are sent from the end user, where the system collects transmissions and multiplexes them so they can be sent in the aggregate to the central office of the local loop.

DNIS (Dialed Number Identification Service): A telephone function that sends the dialled telephone number to the answering service.

DSLAM (Digital Subscriber Line Access Multiplexer): A mechanism at a phone company's central location that links many customer DSL connections to a single high-speed ATM line. When the phone company receives a DSL signal, an ADSL modem with a POTS splitter detects voice calls and data. Voice calls are sent to the PSTN, and data are sent to the DSLAM, where it passes through the ATM to the Internet, then back through the DSLAM and ADSL modem before returning to the customer's PC. More DSLAMs a phone company has, the more customers it can support.

DTMF (Dual-Tone Multifrequency): The audio signals made from pressing the buttons on a touch-tone telephone.

Dynamic Jitter Buffer: Collects voice packets, stores them, and shifts them to the voice processor in evenly spaced intervals to reduce any distortion in the sound.

Dynamic NAT (Dynamic Network Address Translator): A type of NAT in which a private IP address is mapped to a public IP address drawing from a pool of registered (public) IP addresses. Typically, the NAT router in a network will keep a table of registered IP addresses, and when a private IP address requests access to the Internet, the router chooses an IP address from the table that is not at the time being used by another private IP address. Dynamic NAT helps to secure a network as it masks the internal configuration of a private network and makes it difficult for someone outside the network to monitor individual usage patterns. Another advantage of dynamic NAT is that it allows a private network to use private IP addresses that are invalid on the Internet but useful as internal addresses.


E&M (Ear and Mouth): is the interface on a VOIP device that allows it to be connected to analog PBX trunk ports (tie lines).

E.164: The international public telecommunication numbering plan. An E.164 number uniquely identifies a public network termination point and typically consists of three fields, CC (country code), NDC (national destination code), and SN (subscriber number), up to 15 digits in total.

Endpoint: SIP or H.323 terminal or Gateway. An endpoint can Call and be Called. It generates and terminates the information stream.


Failed Call: An attempted Call that does not receive the connect message. Such calls are not billed.

Fiber Optics: Is a cable and technology that uses glass or plastic threads (fiber) to transmit data, each fiber is capable of transmitting messages modulated onto light waves. Fiber optics has several advantages over traditional metal communications lines: 1) Fiber optic cables have a much greater bandwidth than metal cables. This means that they can carry more data. 2) Fiber optic cables are less susceptible than metal cables to interference. 3) Fiber optic cables are much thinner and lighter than metal wires. 4) Data can be transmitted digitally (the natural form for computer data) rather than analogically. The main disadvantage of fiber optics is that the cables are expensive to install. In addition, they are more fragile than wire and are difficult to split .Fiber optics is a particularly popular technology for local-area networks. In addition, telephone companies are steadily replacing traditional telephone lines with fiber optic cables. In the future, almost all communications will employ fiber optics.

Firewall: A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented as hardware, software, or a combination of both. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the security criteria specified on the firewall.

Forward Error Correction: Increases voice quality by recovering lost or corrupted packets.

FXO (Foreign Exchange Office): And FXS (Foreign Exchange Station): FXS and FXS stand for Foreign Exchange Subscriber and Foreign Exchange Office respectively. The FXS interface delivers POTS service from the local phone company (from the Central Office). The FXS interface provides dial tone, battery current, and ring voltage to the subscriber device. The FXO interface receives POTS service from the local phone company (from the switch at the CO). The FXO interface provides on-hook and off-hook indication.

Gatekeeper: The central control entity that performs management functions in a Voice and Fax over IP network and for multimedia applications such as video conferencing. Gatekeepers provide intelligence for the network, including address resolution, authorization, and authentication services, the logging of Call Detail Records, and communications with network management systems. Gatekeepers control bandwidth, provide interfaces to existing legacy systems, and monitor the network for engineering purposes as well as for real-time network management and load balancing. This function is variously referred to as Call Agent, SoftSwitch.

Gateway: In IP telephony, a network device that converts voice and fax calls, in real time, between the public switched telephone network (PSTN) and an IP network. The primary functions of an IP gateway include voice and fax compression/ decompression, packetization, call routing, and control signaling. Additional features may include interfaces to external controllers, such as Gatekeepers or Softswitches, billing systems, and network management systems.

Grace Period: The time interval at the beginning of a call, measured in seconds, that is not billed. IPCB.net fee and the Routing fee do not apply.

Hairpin: Telephony term that means to send a call back in the direction that it came from. For example, if a call cannot be routed over IP to a gateway that is closer to the target telephone, the call typically is sent back out the local zone, back the way from which it came.

Hop off: Point at which a call transitions from H.323 to non-H.323, typically at a gateway. "be hopped-off locally" means "be hairpinned" Example from documentation: "If the called address does not match any known zone prefixes, the gatekeeper will attempt to hairpin the call out through a local gateway.

IDS (Intrusion Detection System): 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. IDS differs from a firewall in that a firewall looks out for intrusions in order to stop them from happening. The firewall limits the access between networks in order to prevent intrusion and does not signal an attack from inside the network. An IDS evaluates a suspected intrusion once it has taken place and signals an alarm. An IDS also watches for attacks that originate from within a system.

IETF (Internet Engineering Task Force): One of two technical working bodies in the Internet Activities Board. The IETF meets three times a year to set technical standards for the Internet.

IHV (Independent Hardware Vendor): Hardware-manufacturing company specializing in specific types of hardware device and not a complete computer system. The IHV typically also provides the software drivers for its hardware devices.

ILEC (Incumbent Local Exchange Carrier): An ILEC is a telephone company that was providing local service when the Telecommunications Act of 1996 was enacted. Compare with CLEC, a company that competes with the already established local telephone business.

Integrated T1: Comprised of 24 64Kbps channels, T1 lines can be used for a diverse number of applications. Commonly referred to as an integrated T1 or channelized T1, this highly flexible circuit is designed for businesses that need to run multiple services over the same line. Common applications for integrated T1 service include, Frame Relay/dedicated long distance and Internet/point-to-point. Often confused with a fractional T1, integrated service is made up of multiple fractional T1 services.

IP Centrex: IP Centrex delivers such services as call hold, call transfer, last number look-up and redial, call forward, three-way calling, but does it on a packet-based network.

IP Telephony: The transmission of voice and fax phone calls over data networks that uses the Internet Protocol (IP). IP telephony is the result of the transformation of the circuit-switched telephone network to a packet-based network that deploys voice-compression algorithms and flexible and sophisticated transmission techniques, and delivers richer services using only a fraction of traditional digital telephony’s usual bandwidth. Compare with VoIP.

ISDN (Integrated Services Digital Network): International communications standard for sending voice, video, and data over digital telephone lines or normal telephone wires. ISDN supports data transfer rates of 64 Kbps (64,000 bits per second). There are two types of ISDN: 1) Basic Rate Interface (BRI) -- consists of two 64-Kbps B-channels and one D-channel for transmitting control information. 2) Primary Rate Interface (PRI) -- consists of 23 B-channels and one D-channel (U.S.) or 30 B-channels and one D-channel (Europe). The original version of ISDN employs baseband transmission. Another version, called B-ISDN, uses broadband transmission and is able to support transmission rates of 1.5 Mbps. B-ISDN requires fiber optic cables and is not widely available.

ITSP (Internet Telephony Service Provider): Same as VoIP Service Provider.

Jitter: The variation in the amount of Latency among Packets being received.

LAN (A local area network): began as a group of computers and associated devices that shared a common communications line or wireless link and typically shared the resources of a server within a small geographic area (for example, within an office building). This architecture is seldom used today. Indeed, computers are connected to a hub where LAN switching occurs. Rather than the wire, it is now the hub backplane that is shared.

Latency: (Also called delay) is the amount of time it takes a Packet to travel from source to destination. Together, Latency and Bandwidth define the speed and capacity of a network.

Licensed Software: The "harvester software" and any other software provided by IPCB.net to a Member for the purpose of record keeping, accounting, and/or access to IPCB.net services, and including IPCB-provided documentation.

Load Balancing: Distribution of calls among terminating Gateways based on the Priorities and Weights assigned by the Buyer.

Login ID: A string of digits identifying an IPCB.net Registered User. Together with the Password, the Login ID is used to authorize a user's access to the IPCB.net trading floor. The Login ID and Password are automatically e-mailed to a potential IPCB.net Member after filling out a Registration.

MAC Address (Media Access Control): Hardware address that uniquely identifies each node of a network. In IEEE 802 networks, the Data Link Control (DLC) layer of the OSI Reference Model is divided into two sub layers: the Logical Link Control (LLC) layer and the Media Access Control (MAC) layer. The MAC layer interfaces directly with the network medium. Consequently, each different type of network medium requires a different MAC layer.

On networks that do not conform to the IEEE 802 standards but do conform to the OSI Reference Model, the node address is called the Data Link Control (DLC) address.

MGCP (Media Gateway Control Protocol): A protocol complementary to H.323 and SIP, designed to control media gateways from external call control elements in decomposed gateway architectures. Working in conjunction with the Gateway Location Protocol (GLP), MGCP enables a caller with a PSTN phone number to locate the destination device and establish a session. It provides the gateway-to-gateway interface for the Session Initialization Protocol (SIP). MGCP is meant to simplify standards for the new Voice over Packet technology by eliminating the need for complex, processor-intense IP telephony devices, thus simplifying and lowering the cost of these terminals.

Minimum Duration: The minimum billed call duration up to which all shorter calls are rounded in seconds.

MPLS (Multi Protocol Label Switching): As the Internet keeps growing, the fundamental packet forwarding function performed by routers becomes ever more complex. Such complexity obviously increases processing delays and reduces traffic throughput. Label switching has proved an efficient mechanism to reduce that complexity. As indicated by its name, label switching is a technique that forwards packets on the basis of an appended label as opposed to the packet destination address in the traditional Internet. A few proprietary schemes were developed before the IETF standardized the concept under the Multi Protocol Label Switching (MPLS) name.

MPLS is referred to as a layer 2.5 protocol as it stands between the Network layer (IP, layer 3) and the Link layer (layer 2) of the OSI stack.

Among the many attributes of MPLS, we may list its role in the support of: traffic engineering, QoS mechanisms, IP-based VPNs.

NAT (Network Address Translation): an Internet standard that enables a local-area network (LAN) to use one set of IP addresses for internal traffic and a second set of addresses for external traffic. A NAT box located where the LAN meets the Internet makes all necessary IP address translations. NAT serves three main purposes: 1) Provides a type of firewall by hiding internal IP addresses. 2) Enables a company to use more internal IP addresses. Since they're used internally only, there's no possibility of conflict with IP addresses used by other companies and organizations. 3) Allows a company to combine multiple ISDN connections into a single Internet connection.

NIDS (Network Intrusion Detection system): Is similar to IDS but individual packets flowing through a network are analyzed. The NIDS can detect malicious packets that are designed to be overlooked by a firewall’s simplistic filtering rules. In a host-based system, the IDS examines at the activity on each individual computer or host.

OC (Optical Carrier): A method to specify the speed of fiber optic networks conforming to the SONET standard. The following illustrates the speeds for common OC levels.

- OC-1 = 51.85Mbps - OC-3 = 155.52Mbps - OC-12 = 622.08Mbps - OC-24 = 1.244Gbps - OC-48 = 2.488Gbps - OC-192 = 9.952Gbps - OC-255 = 13.21Gbps

OEM (Original Equipment Manufacturer): a misleading term for a company that has a special relationship with computer producers. OEMs buy computers in bulk and customize them for a particular application. They then sell the customized computer under their own name. The term is really a misnomer because OEMs are not the original manufacturers -- they are the customizers

OSI (Open System Interconnection): An ISO standard for worldwide communications that defines a networking framework for implementing protocols in seven layers.

OSI (Open Source Initiative): a non-profit organization that promotes the integrity of the open source definition by certifying products with the OSI Certified Open Source Software mark. OSI is comprised of board members who make up its directorship and is not a membership organization.

OSS (Operations Support System): The generic term for a suite of programs that enable an enterprise to monitor, analyze and manage a network system. The term originally was applied to communications service providers, referring to a management system that controlled telephone and computer networks. The term has since been applied to the business world in general to mean a system that supports an organization’s network operations.

OSS (Open Source Software):

Packet: In data communication, the basic logical unit of information transferred.

PBX (Private Branch eXchange): An in-house telephone usually within an enterprise switching system that interconnects telephone extensions to each other as well as to the outside telephone network. Users of the PBX share a certain number of outside lines for making telephone calls external to the PBX.

Most medium-sized and larger companies use a PBX because it's much less expensive than connecting an external telephone line to every telephone in the organization. In addition, it's easier to call someone within a PBX because the number you need to dial is typically just 3 or 4 digits. A new variation on the PBX theme is the centrex, which is a PBX with all switching occurring at a local telephone office instead of at the company's premises.

PPP (Point-to-Point Protocol): One method of connecting a computer to the Internet. PPP is more stable than the older SLIP protocol and provides error checking features. Working in the data link layer of the OSI model, PPP sends the computer's TCP/IP packets to a server that puts them onto the Internet.

PPPOE (Point to Point Protocol of Ethernet): PPPoE relies on two widely accepted standards: PPP and Ethernet. PPPoE is a specification for connecting the users on an Ethernet to the Internet through a common broadband medium, such as a single DSL line, wireless device or cable modem. All the users over the Ethernet share a common connection, so the Ethernet principles supporting multiple users in a LAN combine with the principles of PPP, which apply to serial connections.

POTS (Plain Old Telephone Service): The standard telephone service that most homes use. In contrast, telephone services based on high-speed, digital communications lines, such as ISDN, are not POTS. The main distinctions between POTS and non-POTS services are speed and bandwidth. POTS is generally restricted to about 52 Kbps (52,000 bits per second). The PSTN (Public Switch Telephone Network) is the network supporting the POTS service. While they form a tight pair, they are not the same. POTS should not be confused with pot, an abbreviation of potentiometer. All references to POTS in the RARIS web site refer to the Plain Old Telephone Service.

PRI (Primary Rate Interface): Short for Primary-Rate Interface, a type of ISDN service designed for larger organizations. PRI includes 23 B-channels (30 in Europe) and one D-Channel. In contrast, BRI (Basic-Rate Interface), which is designed for individuals and small businesses, contains just two B-channels and one D-channel. PRI service is generally transmitted through a T-1 line (or an E1 line in Europe).

PSTN (Public Switched Telephone Network): This term refers to the international telephone system based on copper wires carrying analog voice data. This is in contrast to newer telephone networks base on digital technologies, such as ISDN.

QoS (Quality of Service): Traditionally, in the PSTN, QoS referred to the “quality of the line”. This quality was measured on a scale from 1 (very poor quality) to 5 (very good quality). The impact of the introduction of a new technology was measured by having groups of individuals listen to “transmission samples” and rate (from 1 to 5) the perceived quality of communication. The overall rating is thus appropriately named the Mean Opinion Score (MOS).

In the early days of the Internet, only computer-to-computer traffic was flowing on the Internet and the “best-effort” service provided was adequate for this single type of traffic. With the arrival of the web and the multiplication of Internet-based applications, the need for classes of service appeared. Each class of service is characterized by a set of performance attributes that it offers (ex. low packet delay, low packet loss, etc). QoS mechanisms have been designed in order to maintain efficient coexistence of these Classes of Service. QoS mechanisms control flowing traffic in order to ensure that each Class of Service is provided, by the network, adequate processing and transmission resources to maintain specific levels of service per class.

RAS (Registration, Admission, Status): A management protocol between terminals and Gatekeepers.

Route: A set of parameters predefined by IPCB.net to facilitate routing of traffic between the Gateways/Gatekeepers controlled by an IPCB.net Member either via ownership or via a partnership with the owner. Along with specifying other parameters, an IPCB.net Member using the Gatekeeping Service assigns to a Route values specifying the details of both originating and terminating Gateways/Gatekeepers.

RSVP (Resource Reservation Protocol): Protocol that supports the reservation of resources across an IP network. Applications running on IP end systems can use RSVP to indicate to other nodes the nature (bandwidth, jitter, maximum burst, and so on) of the packet streams they want to receive. RSVP depends on IPv6. Also known as Resource Reservation Setup Protocol.

RTP (Real-Time Transport Protocol): Commonly used with IP networks. RTP is designed to provide end-to-end network transport functions for applications transmitting real-time data, such as audio, video, or simulation data, over multicast or unicast network services. RTP provides such services as payload type identification, sequence numbering, time stamping, and delivery monitoring to real-time applications.

SIP (Session Initiation Protocol): An application-layer control protocol, a Signaling protocol for Internet Telephony. SIP can establish sessions for features such as audio/videoconferencing, interactive gaming, and call forwarding to be deployed over IP networks thus enabling service providers to integrate basic IP telephony services with Web, e-mail, and chat services. In addition to user authentication, redirect and registration services, SIP Server supports traditional telephony features such as personal mobility, time-of-day routing and call forwarding based on the geographical location of the person being called.

SLA (Service Level Agreement): a contract between an ASP or SP and the end user which stipulates and commits a required level of service. An SLA should contain a specified level of service, support options, enforcement or penalty provisions for services not provided, a guaranteed level of system performance as relates to downtime or uptime, a specified level of customer support and what software or hardware will be provided and for what fee.

Softswitch: (Also called a Proxy Gatekeeper, Call Server, Call Agent, Media Gateway Controller, or Switch Controller) Software used to bridge a public switched telephone network and voice over Internet by separating the call control functions of a phone call from the media gateway (transport layer). Softswitch performs call control functions such as protocol conversion, authorization, accounting and administration operations.

SoftSwitching Service: IPCB.net Softswitch service allows IPCB.net Members to bill, route and monitor IP telephony traffic between their gateways and the gateways of their partners. For more information on this please refer to the corresponding section of this site.

T1: 1.544-Mbps point-to-point dedicated digital circuit provided by the telephone companies consisting of 24 channels.

TCP (Transmission Control Protocol): TCP is one of the main protocols in TCP/IP networks. Whereas the IP protocol deals only with packets, TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent.

TCP/IP (Transmission Control Protocol/Internet Protocol): The suite of communications protocols used to connect hosts on the Internet. TCP/IP uses several protocols, the two main ones being TCP and IP. TCP/IP is built into the UNIX operating system and is used by the Internet, making it the de facto standard for transmitting data over networks. Even network operating systems that have their own protocols, such as Netware, also support TCP/IP.

ToS (Type of Service): A method of setting precedence for a particular type of traffic for QoS. ToS is an 8-bit field in the IP datagram header that identifies the relative priority of one packet over another. Networking devices use this field to prioritize packets appropriately and place them in different queues if necessary.

Trunk: A communications channel between two points, typically referring to large-bandwidth telephone channels between switching centers that handle many simultaneous voice and data signals.

Trunking: Trunking means that several connections in a network may be established simultaneously, and that setup of connections proceeds automatically using the channels available at the time in question. In this way many users may share a few connections, and if the number of connections is increased, the capacity of the network is increased more than proportionally. This means that an optimal trunking effect is obtained in very large networks.

UBR (Unspecified Bit Rate): or Class D quality of service. UBR is the ATM bandwidth-allocation service that does not guarantee any throughput levels and uses only available bandwidth. UBR is often used when transmitting data that can tolerate delays.

UDP (User Datagram Protocol): A connectionless protocol that, like TCP, runs on top of IP networks. Unlike TCP/IP, UDP/IP provides very few error recovery services, offering instead a direct way to send and receive datagrams over an IP network. It's used primarily for broadcasting messages over a network.

UPS (Uninterruptible Power Supply): A power supply that has a built-in battery to maintain power in the event of a power outage. Typically, a UPS keeps a computer or servers running for several minutes/hours after a power outage, enabling you to save data that is in RAM and shut down the computer gracefully. Many UPSs now offer a software component that enables you to automate backup and shut down procedures in case there's a power failure while you're away from the computer.

There are two basic types of UPS systems: An SPS monitors the power line and switches to battery power as soon as it detects a problem. The switch to battery, however, can require several milliseconds, during which time the computer is not receiving any power. An on-line UPS avoids these momentary power lapses by constantly providing power from its own inverter, even when the power line is functioning properly. In general, on-line UPSs are much more expensive than SPSs.

VBR (Variable Bit Rate): or Class B quality of service VBR is the ATM bandwidth-allocation service that allows users to specify a throughput capacity (i.e., a peak rate) and a sustained rate but data is not sent evenly. VBR is often used when transmitting compressed packetized voice and video data, such as videoconferencing.

VLAN (Virtual Local Area Network): A network of computers that behave as if they are connected to the same wire even though they may actually be physically located on different segments of a LAN. VLANs are configured through software rather than hardware, which makes them extremely flexible. One of the biggest advantages of VLANs is that when a computer is physically moved to another location, it can stay on the same VLAN without any hardware reconfiguration.

VoIP (Voice over IP): The capability to carry normal telephony-style voice over an IP-based Internet with POTS-like functionality, reliability, and voice quality. VoIP enables a router to carry voice traffic (for example, telephone calls and faxes) over an IP network. In VoIP, the DSP segments the voice signal into frames, which then are coupled in groups of two and stored in voice packets. These voice packets are transported using IP in compliance with ITU-T specification H.323.

VoIP Trunking: Service providers can use this application to connect enterprise and call center customers directly to their VoIP network. By bypassing local operators and toll charges, the VoIP trunking application enables service providers to offer attractive termination rates for both domestic and international long distance calling. This application connects seamlessly to the enterprise/call center's PBX, allowing employees to make off-net calls at reduced rates.

VPDN (Virtual Private Dial-up Network): Also known as virtual private dial network. A VPDN is a network that extends remote access to a private network using a shared infrastructure. VPDNs use Layer 2 tunnel technologies (L2F, L2TP, and PPTP) to extend the Layer 2 and higher parts of the network connection from a remote user across an ISP network to a private network. VPDNs are a cost effective method of establishing a long distance, point-to-point connection between remote dial users and a private network.

VPN (Virtual Private Network): Enables IP traffic to travel securely over a public TCP/IP network by encrypting all traffic from one network to another. A VPN uses “tunneling” to encrypt all information at the IP level.

WEP (Wired Equivalent Privacy): A security protocol for wireless local area networks (WLANs) defined in the 802.11 standard. WEP is designed to provide the same level of security as that of a wired LAN. LANs are inherently more secure than WLANs because LANs are somewhat protected by the physicalities of their structure, having some or all part of the network inside a building that can be protected from unauthorized access. WLANs, which are over radio waves, do not have the same physical structure and therefore are more vulnerable to tampering. WEP aims to provide security by encrypting data over radio waves so that it is protected as it is transmitted from one end point to another. However, it has been found that WEP is not as secure as once believed. WEP is used at the two lowest layers of the OSI model - the data link and physical layers; it therefore does not offer end-to-end security.

WPA (Wi-Fi Protected Access): A Wi-Fi standard that was designed to improve upon the security features of WEP. The technology is designed to work with existing Wi-Fi products that have been enabled with WEP (i.e., as a software upgrade to existing hardware), but the technology includes two improvements over WEP:

Improved data encryption through the temporal key integrity protocol (TKIP). TKIP scrambles the keys using a hashing algorithm and, by adding an integrity-checking feature, ensures that the keys haven’t been tampered with.

User authentication, is generally missing in WEP even through the Extensible Authentication Protocol (EAP). WEP regulates access to a wireless network based on a computer’s hardware-specific MAC address, which is relatively simple to be sniffed out and stolen. EAP is built on a more secure public-key encryption system to ensure that only authorized network users can access the network. It should be noted that WPA is an interim standard that will be replaced with the IEEE’s 802.11i standard upon its completion.