Contents:
UninstallationU.S. Robotics SureConnect™ ADSL Ethernet/USB Router User Guide
Windows 95, 98, NT 4.0, Me, 2000, XP or later, Mac and Linux
Glossary
A | B | C | D | E | F | GH | IJKL | M | N | OP | QR | S | TU | V | WXYZ
ADSL (Asymmetric Digital Subscriber Line) - Transports information to and from customers and networks. ADSL employs different upstream and downstream data rates. The “asymmetric” name refers to these differing rates.
AH (Authentication Header) – RFC2402 defines AH. AH provides integrity and authentication through the shared key hashing algorithms (HMAC-MD5, HMAC-SHA1). AH provides authentication for as much of the IP header as possible. AH also authenticates upper level protocol data.
AM (Amplitude Modulation) Modulation method used by modems, radio, and DSL equipment. The signal modulates or alters the amplitude or intensity of the carrier. In regular AM, the carrier is a sinewave. The amplitude of the modulated carrier changes in proportion to signal amplitude. AM creates two identical sidebands on either side of the carrier. These sidebands contain the signal data. Either sideband can be attenuated or suppressed without harming the signal data. With an equivalent signal, AM tends to require less bandwidth than FM does. AM's disadvantage is that it’s more subject to impulse noise and static than FM is.
ATM (Asynchronous Transfer Mode) - Protocol that packs digital information into 53-byte cells. The cells switch throughout a network over virtual circuits.
Average Cell Rate - Maximum sustainable or average rate (Cells/second) for sending cells to the network. Average Cell Rate specifies bandwidth utilization. This value must always be less than or equal to Peak Cell Rate.
Bandwidth - Amount of data that can be transmitted over a given time period.
BPDU (Bridge Protocol Data Unit) - Data messages exchanged across switches in an extended LAN with a spanning tree protocol topology. BPDU packets assure that data arrives at the intended destination. These packets contain information on addresses, costs, ports, and priorities. Network loop detection involves exchanging BPDU messages across bridges. Loop deletion entails placing redundant switch ports in a backup (blocked) state and shutting down selected bridge interfaces.
Bridge – A device that connects two LAN segments together. These LAN segments may be of similar or dissimilar types, such as Ethernet and Token Ring. Inserting a bridge into a network segments the network. The bridge improves performance by keeping traffic contained within bridge segments.
Bridge Loop - Path that links one network segment to another. The spanning tree protocol avoids bridge loops.
Bridge Priority - Determines which bridge becomes the root bridge.
Burst Size (Cells) - Maximum number of cells that the user can send at peak rate in a burst. We measure burst size from within a sustainable rate.
CAP (Carrierless Amplitude and Phase Modulation) Modulation method used by modems and DSL equipment. Based on QAM. Signals modulate two wideband signals using passband modulation. CAP permits two to nine bits per frequency cycle.
Carrier wave - Periodic waveform. A carrier may be modulated or unmodulated. It may also be continuous or switched. Typically, modems modulate the carrier wave with a data signal. Modulation represents the data signal by impressing a variation on some characteristic of the carrier wave. For instance, a circuit may represent the signal as a proportional shift in carrier amplitude, frequency, or phase. Demodulation (detection) eliminates the carrier wave and reproduces the signal. The carrier frequency must be significantly greater than the signal frequency. A modem may simultaneously apply more than one signal and more than one modulation method to the same carrier. The modulation method may suppress the carrier before transmission. In that case, the receiver must reinsert the carrier before demodulation can occur.
CBR (Constant Bit Rate) - Service type that supports real-time applications with a fixed bandwidth. These applications, such as a video stream, produce data at regular intervals. The user can specify how much bandwidth that he wishes to reserve.
CDVT (Cells) - Parameter that constrains the number of cells that the user can send to the network at the maximum line rate.
Cycle - One half of a periodic wave. For instance, a sinewave includes one positive and one negative cycle.
DHCP (Dynamic Host Configuration Protocol) - Protocol for automatic TCP/IP configurations. DHCP provides static and dynamic address allocation and management.
DHCP Relay - Suppose that a Dynamic Host Configuration Protocol (DHCP) server resides on a different LAN than the node broadcasting for DHCP service. Then the DHCP broadcast request must be forwarded across the router/WAN to a subnet where a DHCP server resides. To assure receipt of an IP address that corresponds to this subnet, the router must use a DHCP relay. The router needs to know the IP address of the DHCP server. With this address, the router can direct the request to the appropriate DHCP server.
DMT (Discrete Multitone) - Most common DSL modulation method. DMT creates 256 channels across the usable frequency spectrum. Each channel measures 4.3125KHz wide. Dividing the spectrum into channels allows DMT to function well in spite of nearby AM radio transmitters. The DMT modulator and demodulator is the FFT (Fast Fourier Transform) algorithm. Inside each channel, the modulation technique is QAM. Within each channel, the number of bits per symbol may be independently selected. Independent selection allows a DMT modem to be rate adaptive. Both G.DMT and G.Lite use DMT.
DNS (Domain Naming System) - Mechanism used in the Internet for translating names of host computers into IP addresses.
DNS Relay - DNS requests that the router forwards from a LAN node to a known DNS server. The router uses a DNS relay when the router functions as a NAPT (Network Address Port Translation) device. The requests arrive at a DNS server over the WAN link. To function as a NAPT, the router requires DNS relay settings.
DSLAM (Digital Subscriber Line Access Multiplexer) - Network device that receives signals from multiple customer Digital Subscriber Line connections. DSLAM places signals on high speed lines with multiplexing techniques for the fastest phone line technology available.
ESP (Encapsulating Security Payload) – ESP provides confidentiality. Optionally, ESP also provides integrity, authentication, anti-replay service, and limited traffic flow confidentiality. Options selected at the time of Security Association establishment determine provided services. For confidentiality, shared ESP supports shared key encryption algorithms, such as DES and Triple DES.
Filter - Operating parameter used in LAN bridges and routers. When set, the filter causes bridges and routers to block transfer of packets between LANs. The term "filter" also applies to a hardware device, such as a microfilter. When installed, this device reduces interference between DSL signals and telephone signals.
Forward Delay Time - Timeout value employed by all bridges in the bridged LAN. The root sets the forward delay value.
FM (Frequency Modulation) Modulation method used by modems, radio, and DSL equipment. The signal modulates or alters the frequency or pitch of the carrier. In regular FM, the carrier is a sinewave. The frequency of the modulated carrier changes in proportion to signal amplitude. FM creates an infinite number of sidebands. These sidebands contain the signal data. With an equivalent signal, FM tends to require more bandwidth than AM does. FM's advantage is that it’s less subject to impulse noise and static than AM is.
Frame - Variable length information unit that contains packets. Also refers to a transmission frame, a fixed-length unit that carries bits across a physical link. A transmission frame is a framed transport component. DSL technologies use frames. Also refers to a frame of video, one image in a video sequence
Gateway - Entrance to and exit from a communications network.
G.DMT - The ADSL standard approved by the International Telecommunications Union (ITU). G.DMT indicates full-rate ADSL, which provides standards for higher speed ADSL than G.Lite. G.DMT provides maximum data rates of 8 Mbps downstream from the subscriber and 1.5 Mbps upstream from the subscriber.
G.lite - Standard way to install Asymmetric Digital Subscriber Line service. Over regular phone lines, G.Lite makes possible Internet connections to home and business computers at up to 1.5 Mbps. Officially known as G.992.2.
Hello Time - Time interval between generations of configuration BPDUs. The root bridge generates configuration BPDUs.
ICMP - (Internet Control Message Protocol) - A TCP/IP protocol for sending error and control messages. For example, a router uses ICMP to notify the sender that the router’s destination node is unavailable. A ping utility sends ICMP echo requests to verify the existence of an IP address.
Interface Name - Router interface that will be configured.
IP (Internet Protocol) - Protocol that allows a packet of information to travel through many networks and LANs.
IP Address - IP addresses deliver packets of data across a network. These addresses differentiate the source and destination IP address and keep them constant. When a router port detects a packet, the router checks the routing table. The port attempts to match the network number of the destination IP address with its routing table entry. If the port finds a match, it forwards the packet to the destination network. With no match, the port forwards the packet to a router defined as the default gateway.
LAN (Local Area Network) - Network base covering a local geographic area. A LAN connects computers in the same building or area.
Link Cost - Cost associated with the interface. Based on this cost, the bridge decides which link to forward data over.
MAC Address (Local Area Network) - Unique serial number burned into Ethernet adapters. Distinguishes the network card from others.
Max Age Time Timeout value that all bridged LAN bridges use. The root bridge sets the Max Age value.
MAC Filter (Local Area Network) - Method of allowing or rejecting WAN access for specific machines.
Microfilter - Device that separates the ADSL data signal from the telephone signal so that the ADSL data signal does not interfere with the telephone device.
Modulation - Varying elements of electrical carrier waves in a manner that represents signal data. Demodulation restores the signal data. A modulated signal requires more bandwidth and an unmodulated signal does. The bandwidth increase results from the creation of sidebands during modulation. The sidebands contain the signal. AM creates two, identical sidebands on either side of the carrier. FM creates an infinite number of sidebands.
MTU (Maximum Transmission Unit) - Parameter that limits the size of packets that transmit on an interface. Not all interfaces support the MTU parameter. Some interfaces, like Ethernet, have range restrictions (80 - 1500).
NAP (Network Access Point) - Public network exchange facility where ISPs connect while peering. NAP connections determine how the Internet routes traffic.
Next Hop IP - IP address or Gateway used to arrive at the destination address.
NRT-VBR (Non Real Time-Variable Bit Rate) - Service type that supports applications that have no constraints on delay and delay variation, but still have variable-rate and burst traffic characteristics.
PAM (Pulse Amplitude Modulation) Modulation method used by modems and DSL equipment. The signal modulates or alters the amplitude or intensity of the carrier. In regular AM, the carrier is a sinewave. In PAM, the carrier is a periodic series of DC pulses.
PCM (Pulse Code Modulation) - Digital modulation method for transmitting analog data. PCM signals are binary. These signals can represent any analog data with only two states, logic 0 and logic 1.
PDM (Pulse Duration Modulation) Modulation method. Signal modulates or alters the duty cycle of the pulse. In PDM, the carrier is a pulse stream. Also called PWM (Pulse Width Modulation).
Peak Cell Rate - Maximum rate (Cells/second) for sending cells to the network.
Phase - Position of a periodic waveform.
PM (Phase Modulation) Modulation method used by modems, radio, and DSL equipment. The signal modulates or alters the phase or position of carrier waves. In regular PM, the carrier is a sinewave. The phase of the modulated carrier changes in proportion to signal amplitude.
Port Priority - Parameter that determines which port becomes the root bridge port.
POTS (Plain Old Telephone Service) - Basic voice service available in residences throughout the United States.
PP (Point-to-Point Protocol) – Communication protocol for dialing up the Internet over a serial link. Such serial links include a POTS and an ISDN line. PPP establishes the session between the user’s computer and the ISP. PPP uses the Link Control Protocol (LCP), which also handles authentication (PAP, CHAP, etc.), compression, and encryption.
PPM (Pulse Position Modulation) Modulation method used by modems and DSL equipment. The signal modulates or alters the location of a pulse in the carrier. The carrier is a stream of pulses.
PPPoA (Point-to-Point Over ATM) – Dial-up Internet connections typically use PPP protocol. PPPoA is a method for running PPP protocol over ATM. PPPoA… •
• offers service providers similar billing and access control with a presence in dial-up services.
• provides session authentication using Password Authentication Protocol (PAP).
• provides session authentication using Challenge Handshake Authentication Protocol (CHAP).
• achieves session accounting and conservation of bandwidth by closing down unused sessions.
• allows the IAD/Router and ISP link to easily negotiate network parameters.
PPPoE (Point-to-Point Over Ethernet) – Dial-up Internet connections typically use PPP protocol. PPPoE is a method for running PPP protocol over Ethernet. PPPoE… •
• offers service providers similar billing and access control with a presence in dial-up services.
• provides a low-cost solution to multiple host maintenance at the customer premises.
• provides session authentication using Password Authentication Protocol (PAP).
• provides session authentication using Challenge Handshake Authentication Protocol (CHAP).
• achieves session accounting and conservation of bandwidth by closing down unused sessions.
• allows the IAD/Router and ISP link to easily negotiate network parameters.
PVC (Permanent Virtual Circuit) - Virtual connection between two fixed endpoints on the network. Frame relay and ATM networking term.
PWM (Pulse Width Modulation) Modulation method. Signal modulates or alters the duty cycle of the pulse. In PWM, the carrier is a pulse stream. Also called PDM (Pulse Duration Modulation).
QAM (Quadrature Amplitude Modulation) Modulation method used by modems and DSL equipment. Combines two amplitude-modulated (AM) signals into a single channel. The modem inserts the signals 90 degrees (one-quarter cycle) out of phase with each other. Engineers call this 90-degree phase shift "quadrature." QAM modulates both carrier phase and amplitude. Doubles effective bandwidth.
RAM (Random Access Memory) - Primary memory in a computer. The computer can overwrite this type of memory with new data. The "random access" part of RAM derives from the way RAM stores data: The computer can locate any bit of information in RAM in an equal amount of time. This fact applies regardless of where the bit resides.
RIP (Routing Information Protocol) - Routing protocol and part of the TCP/IP suite. RIP determines a route based on the smallest hop count between source and destination. RIP determines the smallest hop count by communicating with other routers within the network. Only use RIP if the target router also utilizes RIP.
RJ-11 - Six-conductor modular telephone jack wired for up to four wires. The most common telephone jack in the world is the RJ-11. This connects telephone instruments, modems, and fax machines to a female RJ-11 jack. The female jack often mounts to the wall or floor.
RJ-45 - Eight-conductor modular telephone jack. Used for 10BaseT, ISDN and other data connections.
Router - Device that forwards data packets between local area networks (LANs) or wide area networks (WANs). Referring to routing tables and routing protocols, routers read the network address in each transmitted packet. Routers then decide where to send the packet. A router bases this decision on the best route. When a router port detects a packet, the router checks the routing table. The port attempts to match the network number of the destination IP address with its routing table entry. If the port finds a match, it forwards the packet to the destination network. With no match, the port forwards the packet to a router defined as the default gateway.
RT-VBR (Real Time-Variable Bit Rate) - Service type that supports time-sensitive applications such as voice. Varies the rate at which cells arrive.
Sideband - Band of frequencies adjacent to the carrier. Modulation of the carrier creates sidebands. The sidebands contain the signal data, but consume bandwidth beyond what the carrier needs. In some cases, circuitry may suppress duplicate sidebands without harming the signal data. For instance, AM becomes single sideband when circuits delete one of two identical AM sidebands. Some single sideband equipment also suppresses the carrier frequency. The carrier must then be restored at the receiver before the signal can be demodulated, that is, recovered.
Spanning Tree-Bridging - Particular algorithm or formula. Transparent bridges use the spanning tree algorithm to dynamically determine the best source-to-destination path. This algorithm avoids bridge loops (multiple paths that link one segment to another) within a network. The algorithm determines all redundant paths and makes only one of them active. The spanning tree protocol (STP) is part of IEEE standard 802.1.
Splitter - DSL device that accommodates analog telephones, plus digital data access over the Internet. With a splitter, analog voice signals transmit at baseband frequencies. These combine with passband data transmission through a low-pass filter.
Static routes - Permanent routes that the router stores. The router uses these routes when determining where to forward IP packets that it receives.
Subnet Mask - Portion of a network. Distinguished from other portions by the use of a mask or subnet number. Subnet masks split one network into a set of mini networks or subnets. Subnetting helps to reduce traffic on each subnet. Subnetting also makes the network more manageable. Each subnet functions as if it were an independent network.
SVC (Switched Virtual Circuit) - Virtual connection between two variable endpoints on the network. The switch makes at the beginning of the call, and breaks at the end of the call. A frame relay and ATM networking term.
TCP/IP (Transmission Control Protocol/Internet Protocol) - Set of protocols designed to link dissimilar computers that use various networks and LANs.
Topology - Geometric physical or electrical configuration that describes a local communication network. The most common distribution system topologies are the bus, ring, and star.
UDP (User Datagram Protocol) - A protocol within the TCP/IP protocol suite. When reliable delivery is unnecessary, communications may use UDP instead of TCP.
UBR (Unspecified Bit Rate) - Best effort service that does not require tightly constrained delay and delay variation. UBR provides no specific quality of service or guaranteed throughput.
USB (Universal Serial Bus) - External bus standard that supports data transfer rates of 12 Mbps.
VCI (Virtual Channel Identifier) - Address of a virtual circuit. An integer that ranges from 0 to 65,535. The integer identifies a virtual channel that cells may traverse.
VPI (Virtual Path Identifier) - Address of a virtual path to a connection on an ATM network. An integer that ranges from 0 to 4,095.
WAN (Wide Area Network) - Network base that covers a large geographic area.
WINS (Windows Internet Name Service) - Service that transposes Windows networking names into addresses usable for routing purposes.
