PPPoE Mode

Getting Started

Using your modem

Advanced Operations

General Information

Troubleshooting

FAQs


Glossary

ADSL (Asymmetric Digital Subscriber Line)
A new technology that allows more data to be sent over existing copper telephone lines (POTS or "Plain Old Telephone Service"). ADSL is more than 275 times faster than a 28.8 modem and up to 4 times faster than a T1 connection. That's really, really fast. DSL (ADSL, SDSL) technology uses your ordinary phone line but doesn't tie it up. You can access the Internet while you are telephoning or faxing. ADSL requires a special ADSL modem which allows your PC to connect to a remote site using a network protocol such as IP or IPX. Your HomeConnect ADSL Modem Dual Link contains one ADSL modem port, which is the WAN (Wide Area Network) interface. ADSL service runs between your home and your service provider, who then uses ATM technology to speed communications to more distant points.


ATM (Asynchronous Transfer Mode)
A network technology based on transferring data in small cells or packets of a fixed size. The small cell size allows ATM equipment to transmit video, audio, and computer data over the same network without any type of data consuming the entire capacity of the line. ATM differs from TCP/IP, where message packets take different routes from source to endpoint. ATM defines connections by two main parameters: Virtual Path Identifier (VPI) and Virtual Channel Identifier (VCI). VPI and VCI are defined in this Glossary. Your service provider will tell you what VPI and VCI values you must use in your Dual Link in order to properly connect to their service.


Bridging, Bridged
In networking, bridging is the process of moving a packet (or piece) of data from source to destination. A bridge is a mechanism which forwards packets between different networks based on hardware-level addresses. Your HomeConnect modem automatically maintains a forwarding table that contains information needed to correctly route data, so you don't need to manually add or delete entries as your home network configuration changes.


Connector (or Jack)
The part of a cable that plugs into a port or interface to connect one device to another.


Console Port
The console port on your Dual Link can be matched to the Com port (Com1, Com2...) on your computer using the DB-9 serial cable provided. On the ADSL Modem Dual Link, it is typically used only in the case of disaster recovery.


DHCP (Dynamic Host Configuration Protocol)
This allows a device to have a different IP address every time it connects to the network or, in some cases, to change while it is still connected. The software keeps track of IP addresses. This allows a new computer to be added to a network without having to manually assign it a unique IP address.


DIP switch
A series of tiny switches built into circuit boards. DIP switches let you configure a circuit board to conform to a particular application. In the case of your Dual Link modem, the DIP switch is reserved and all toggle switches should be left in the Off position.


DSL (Digital Subscriber Line)
The two main categories of DSL currently are the ADSL (Asynchronous DSL) and SDSL (Synchronous DSL). DSL technologies pack data onto copper wires. They are used for connections from a telephone switching station to a home or office, not between switching stations. DSL is similar to ISDN in that both operate over existing copper telephone lines (POTS) and both require the short runs to a central telephone office (usually less than 20,000 feet). But DSL offers much higher speeds.


Encapsulation
In networking, encapsulation means wrapping a data set in a protocol header. This allows one network to send its data via another network's connections.


Ethernet
Ethernet is a LAN (local area network) protocol that was developed by Xerox Corporation in cooperation with DEC and Intel in 1976. It is one of the most widely implemented LAN standards. Its function is to move data packets from one computer to another.


Flash Memory
An area on the modem where basic information necessary to operate the modem is stored. In your modem Dual Link, it contains a program with the extension ".nac" which must be easy to update but not easy to erase. A utility provided on your installation CD, if you install it on your PC, can search for any updates to the Nac file from the 3Com web site.


Host
The word Host has several different meanings in the computer industry. The "host" can be referred to as the computer system that is accessed remotely by modem over telephone lines by a user sitting at a remote terminal. It has also come to mean any computer connected to a TCP/IP network, including the Internet. Each Host has a unique IP address. "To host", on the other hand, means to provide the infrastructure for a computer service, as, for example, to "host" Web servers, where the hardware, software and communication lines are provided and controlled by the company providing the server while the content on the server is controlled by the user.


Hub
A conduit for information between devices that are part of a network. A hub contains a number of ports which all participating devices (computers, printers, scanners, etc.) in the network plug into. The hub then receives and directs information to all segments of the LAN.


LAN
A computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings. However, one LAN can be connected to other LANs over any distance via telephone lines and radio waves. A system of LANs connected in this way is called a wide-area network (WAN). Computers connected to a LAN are able to share, not only data, but also expensive devices, such as laser printers and scanners. Ethernet LANs are most common for PCs. Data transmission is very fast on a LAN, but the distances and numbers of computers that can be connected are limited.


LED (light emitting diode)
An electronic device or signal that lights up when electricity is passed through it. Your Dual Link modem uses LEDs to indicate the status of important operations.


Modem (modulator-demodulator)
A modem is a device or program that enables a computer to transmit data over telephone lines. The modem converts data which is stored digitally (in the computer) to analog data (which is required for transmission over telephone lines) and vice versa. Simply stated, "digital" data is based on discrete "on-off" switching (1 and 0) whereas analog data consists of infinitely variable data, such as sound waves.


Nac file
A "Nac file" is a file with the extension .nac. The file extension was coined by U.S. Robotics from the words Network Application Code or Network Application Card. It contains information essential to network communications and resides in the Flash memory of your modem Dual Link. If you choose to install the "Instant Update" utility from your modem's installation CD, the utility will search for and download from the 3Com web site any update to the Nac file. Once you've received an updated Nac file, you would install to the modem using the DL manager.


NIC (network interface card)
An expansion board or adapter that you install or insert into a computer in order to make it capable of communicating to a network. A common example is an Ethernet LAN adapter.


IP (Internet Protocol)
Specifies the format of packets (pieces of data) and the addressing scheme. Most networks combine IP with a higher-level protocol called Transport Control Protocol (TCP), which establishes a virtual connection between a destination and a source. IP by itself is like a postal system. Using it, you can "address a package and drop it in the mail," but there's no direct link between you and the recipient. TCP/IP, on the other hand, establishes a connection between two hosts so that they can send messages back and forth for a period of time.


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.


Jack
The part of a cable that plugs into a port or interface to connect one device to another.


Packet
A piece of a message transmitted over a packet-switching network. In IP networks, packets are often called datagrams. In a packet-switching network, messages are divided into "packets" which are addressed and sent separately and matched up at their destination.


PIN
A male lead (a thin metal foot or prong) on a connector.


POTS
Plain Old Telephone Service.


PPP (Point-to-Point Protocol)
A method of connecting a computer to the Internet. Other methods are Bridged (RFC-1483) and PPPoE. PPP is one of the most widely used data link protocols in networks. It lets a computer connect to the Internet with a standard dial-up telephone line and a high-speed modem. In order to use PPP, your service provider must support it.


PPPoE (Point-to-Point Protocol over Ethernet)
PPPoE was developed to allow users to connect a LAN to connect to the Internet over a single link (Virtual Circuit). In PPP and RFC-1483, connections exist between the HomeConnect ADSL Modem Dual Link and the ISP, while in PPPoE, the link is to the individual PCs. So the user on the LAN can select when to connect to a particular service by "logging in" to that service (sort of like placing a telephone call.) Choosing which of the protocols to use is not up to the user but dependent on the ISP. Ask your service provider if it's available.


Protocol
An agreed-upon format for transmitting data between two devices. The protocol determines the type of error-checking to be used, the data compression method, how the sending device will indicate that it has finished sending a message, and how the receiving device will indicate that it has received a message. From a user's point of view, the only interesting aspect about protocols is that your computer or device must support the right ones if you want to communicate with other computers.


PVC (permanent virtual circuit)
A virtual circuit that is permanently available. The only difference between a PVC and a switched virtual circuit (SVC) is that an SVC must be re-established each time data is to be sent. Once the data has been sent, the SVC disappears. PVCs are more efficient for connections between hosts that communicate frequently.


RFC
Short for Request for Comments, a series of notes about the Internet, started in 1969. An RFC can be submitted by anyone. Eventually, if it gains enough interest, it may evolve into an Internet standard. RFC-1483 is the protocol traditionally used for ATM networks. Each RFC is designated by an RFC number. Once published, an RFC never changes. Modifications to an original RFC are assigned a new RFC number.


RFC-1483
This is a protocol used for ATM networks. It's a very efficient channel or path for data transmission. It differs from PPPoE and PPP in that it doesn't provide any built-in negotiation for addresses or connection.


RJ-11 Jack
Short for Registered Jack-11, a four- or six-wire connector used primarily to connect telephone equipment in the United States. RJ-11 connectors are also used to connect some types of local-area networks (LANs), although RJ-45 connectors are more common.


RJ-45 Jack
Short for Registered Jack-45, an eight-wire connector used commonly to connect computers onto local-area networks (LANs), especially Ethernets. RJ-45 connectors look similar to the ubiquitous RJ-11 connectors used for connecting telephone equipment, but they are somewhat wider.


SDSL (symmetric digital subscriber line)
SDSL is called symmetric because it supports the same data rates for upstream and downstream traffic. A similar technology that supports different data rates for upstream and downstream data is called asymmetric digital subscriber line (ADSL). ADSL is more popular in North America, whereas SDSL is being developed primarily in Europe


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 communications protocols used to connect hosts on the Internet. 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 support TCP/IP.


Telecommuting
A term coined in the early 1970s to describe a geographically-dispersed office where workers can work at home on a computer and transmit data and documents to a central office via telephone lines.


USB (Universal Serial Bus)
A new external bus standard that supports very fast data transfer rates. A single USB port can be used to connect up to 127 peripheral devices. Manufacturers are including USB ports in more and more new computers.


VCI (Virtual Circuit Identifier)
A virtual circuit is a connection between two devices that acts as though it's a direct connection even though it may physically be circuitous. The term is used most frequently to describe connections between two hosts in a packet-switching network. The two hosts can communicate as though they have a dedicated connection even though the packets might actually travel very different routes before arriving at their destination.


VPI (Virtual Path Identifier)
"Virtual path" refers, in networking, to the location of a file or directory on a server being accessed remotely via the Web. The VPI is the address of the file.


WAN (Wide Area Network)
A computer network that spans a relatively large geographical area. Typically, a WAN consists of two or more local-area networks (LANs). Computers connected to a wide-area network are often connected through public networks, such as the telephone system. They can also be connected through leased lines (cable) or satellites. The largest WAN in existence is the Internet.


Workstation
(1). In networking, workstation refers to any computer connected to a local-area network. It could be a "workstation" (definition 2) or a personal computer (PC). (2). A "workstation" in a second sense generally means a computer that is capable of a moderate amount of computing power and high graphics capabilities. It is somewhere in power between a PC and a mini-computer, although the lines are becoming more and more blurred.