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This document describes the Cisco IOS support for the Octal-Port DMT ATU-C over ISDN (8xDMT over ISDN) line card. It also includes information on new and modified Cisco IOS software commands.
This document includes the following sections:
The 8xDMT over ISDN line card provides high port density for the Cisco 6015 DSLAM and the Cisco 6260 DSLAM. The line card:
G.dmt support is provided through both the Management Information Base (MIB) and the command line interface (CLI).
G.hs support is provided through both the MIB and the CLI.
You can configure the parameters for either the fast or interleaved path using the DSL profile configuration commands. Although you can configure both paths, only one path will actually be enabled (dual latency is not supported at this time). Thus, the maximum bit rate for the unused path must be zero. For example, to configure and use the fast path, you must specify nonzero maximum bit rates for the fast path. After you configure the maximum bit rates for the fast path, the rates for the interleave path must be zero. Cisco IOS software ensures that only one path is enabled at a given time.
The fast path provides improved latency characteristics for applications that cannot tolerate latency (for example, voice). Before you migrate from interleaved mode to fast path, determine if the deployed CPEs offer support for the feature.
Trellis encoding improves performance in a noisy environment. It enables you to transmit at faster line rates with lower error rates, thus providing faster overall throughput in a moderately noisy environment.
By default, the 8xDMT over ISDN line card automatically configures itself for the type of trellis encoding supported on the CPE. It is no longer necessary to enable trellis encoding in the DSL profile.
The 8xDMT over ISDN line card improves the manageability of Discrete Multi-Tone (DMT) ports on supported DSLAMs. The following commands are used to configure this functionality:
DMT minrate-blocking customizes the DMT port reaction to lines that train below configured minimum bit rates. Formerly, a line that trained below the configured minimum bit rate generated a minor alarm, but the DMT port remained active. The dmt minrate-blocking command prevents DMT ports from training when bit rates fall below the configured minimum threshold specified in the dmt bitrate minimum command.
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Note If the bit rates on a DMT port violate the minimum allowed bit rates specified in the dmt bitrate minimum command, the default configuration (DMT minrate-blocking turned off) generates a minor alarm (if alarms are enabled in the DSL profile). |
The dmt rate-adaptation command causes the signal-to-noise ratio (SNR) to be monitored on DSL lines. When enabled, software monitors the upstream and downstream DMT ports for low SNR margins. When the actual upstream or downstream margin falls below the DMT rate-adaptation margin for the duration of the configured rate-adaptation interval, the line drops and attempts to retrain. If the line is able to retrain, it trains to a lower bit rate with improved SNR margins.
The 8xDMT over ISDN line card is supported in chassis halves in the Cisco 6015 DSLAM and in chassis quadrants in the Cisco 6260 DSLAM. If a chassis section (half or quadrant) contains 8xDMT over ISDN line cards, you can install other types of supported line cards in other chassis sections; however, you can install only 4xDMT over ISDN (Annex B) line cards in the same section as the 8xDMT over ISDN line cards.
See the "CPEs" section for information about operating requirements for Alcatel-based CPEs and Cisco SOHO 76 and 826 CPEs.
Use line lengths greater than 100 meters.
Provision the maximum downstream rate to 7616 kbps or less.
Modes 0, 1, and 2 are not supported. Only framing mode 3 is supported.
Do not remove the data line from the CPE modem while voice traffic is present because the ISDN line could momentarily drop and terminate the voice line.
Do not select a zero interleaving delay parameter because that parameter is likely to create a high-bit error rate with long loops. Use the default parameter.
Bit swapping is not supported.
A list of all DSL hardware-related documentation is available at the following URL:
http://www.cisco.com/univercd/cc/td/doc/product/dsl_prod/index.htm
A list of all Cisco IOS DSL software-related documentation is available at the following URL:
http://www.cisco.com/univercd/cc/td/doc/product/dsl_prod/ios_dsl/index.htm
In the ATM software-related documentation, look for information about the Cisco LightStream 1010, which uses the same software base as the NI-2 DSL systems. It is available at the following URL:
http://www.cisco.com/univercd/cc/td/doc/product/atm/index.htm
The 8xDMT over ISDN line card is supported by Cisco 6015 DSLAM and Cisco 6260 DSLAM platforms with NI-2. Table 1 lists the total available ADSL modem connections that each chassis supports.
Table 1 Number of Available Modem Connections for Each Chassis
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The 8xDMT over ISDN line card supports the following types of CPEs:
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Note Alcatel-based CPEs and Cisco SOHO 76 and 826 CPEs require Cisco IOS Release 12.2(4)YA2 or later. We also recommend that you issue the command dsl operating-mode annexb-ur2 at the CPE to enable DMT operating mode on these CPEs. |
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Note A correct firmware version does not guarantee operation with third-party CPEs. Some hardware variations can affect performance and error rates. Before provisioning service, test the operation of CPEs with the 8xDMT over ISDN line card in the targeted deployment model. |
The 8xDMT over ISDN line card is designed for use in a configuration with an ISDN POTS splitter. The line card provisions one modem directly and is physically connected to one specific subscriber line through the POTS splitter. Telco equipment includes DMT/ISDN splitters to separate or combine ISDN and DMT signals at the CO and at the customer site.
ADC Telecommunications supplies POTS splitters for the ETSI Annex B splitter, types 2B1Q or 4B3T. Check with a Cisco customer representative to verify ISDN POTS splitter compatibility with the 8xDMT over ISDN line card.
The ATU-C transceiver complies with the following standards:
To obtain lists of supported MIBs by platform and Cisco IOS release and to download MIBs, go to the Cisco MIB page at the following URL:
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
The 8xDMT over ISDN line card is supported by the following DSLAMs with Cisco IOS Release 12.2(5)DA or later installed:
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Note If you are upgrading from Cisco IOS Release 12.1(5)DA1 or earlier images on the NI-2 card to Release 12.2(5)DA or later, you must reformat the boot flash memory on the NI-2 card. See the Release Notes for Cisco IOS Release 12.2(5)DA for instructions. |
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Note If you are using an Alcatel-based CPE, a Cisco SOHO 76 CPE, or a Cisco 826 CPE, see the operational requirements for those CPEs in the "CPEs" section. |
The following sections describe how to configure the 8xDMT over ISDN line card for operation:
In global configuration mode, use the following commands to preprovision a slot for the 8xDMT over ISDN line card:
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Tip After you have completed these steps, insert the 8xDMT over ISDN line card to activate the line card with your preprovisioned configuration. |
Use the show running-configuration command to verify that the slot is preprovisioned correctly.
Before you start this configuration task, install the 8xDMT over ISDN line card. Refer to the Octal-Port DMT ATU-C Over ISDN Line Card FRU Installation and Replacement Notes for information on installing the 8xDMT over ISDN line card.
In global configuration mode, use the following commands to associate a DSL profile with a port:
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You can use the show dsl profile profile-name command or the show running-configuration command to verify that the DSL profile is attached to a port.
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Tip If no DSL profile appears in the show running-configuration command output, the default DSL profile is enabled. |
We recommend that you use the default DSL profile values. To modify a profile, use the following commands in global configuration mode. These commands modify the default bit rate for the fast path, change the signal-to-noise ratio, and change the DMT check bytes in your DSL profile:
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Caution Before migrating from interleaved mode to fast path, determine whether the deployed CPEs support the fast path feature. |
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Cisco.com is a starting point for all technical assistance. Customers and partners can obtain documentation, troubleshooting tips, and sample configurations from online tools.
For Cisco.com registered users, additional troubleshooting information is available at the following TAC web site:
http://www.cisco.com/kobayashi/support/tac/tsa/launch_tsa.html
Also see the "Monitoring and Maintaining the 8xDMT over ISDN Line Card" section.
Use the following commands to monitor and maintain the 8xDMT over ISDN line card:
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The following example shows how to create a profile named 8xDMT/ISDN. In the profile, default profile values are used for any parameters not specified.
This section documents the new and modified commands that are specific to the 8xDMT over ISDN line card. All other commands used with the line card are documented in the Command Reference for Cisco DSLAMS with NI-2. For information on other Cisco IOS commands that can be used on the NI-2 DSL systems, see the Cisco ATM Switch Router Command Reference.
To enable alarms in profile command mode, use the alarms command. To disable alarms, use the no form of the command.
Syntax Description
This command has no keywords or arguments.
Defaults
Command Modes
Command History
Usage Guidelines
The command affects minor alarms for DSL subscriber ports only. The alarms that this command controls apply to these event classes:
Enabling or disabling alarms affects the specified profile only. For example, if you disable alarms on the default profile, other profiles are unaffected.
Use alarms and no alarms to enable and disable minor alarms related to DSL subscriber ports. If these alarms are disabled, no notification appears if alarm conditions exist. (Notification methods include console messages, LEDs, the output of the show facility-alarm command, and relay alarm signals to external systems for audible or visible alarms.) However, you can track the condition of DSL ports on which alarms are disabled, including conditions that ordinarily trigger alarms, using the show dsl interface atm slot# /port# command.
You can suppress minimum bit rate alarms without disabling other alarms for the profile.
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Note The alarms command has no effect on critical alarms, major alarms, or minor alarms related to subsystems other than the DSL subscriber ports. |
Examples
In this example, the command enables alarms for the default profile:
Related Commands
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To set the maximum and minimum allowed bit rates for the fast or interleaved DMT profile parameters, use the dmt bitrate profile configuration command. To reset this command to the default value, use the no form of this command.
Syntax Description
Defaults
Command Modes
Command History
Usage Guidelines
Only the alarm subsystem uses the minimum bit rate settings. Cisco IOS software asserts an alarm if the line card trains at a rate below the configured minimum bit rate. However, if you disable alarms, no alarm occurs. See Alarms in Chapter 2 of the Command Reference for Cisco DSLAMS with NI-2 for more information on enabling and disabling alarms.
If alarms are enabled for the profile, you can set the DMT bit rate to 0 to disable the associated minimum DMT bit rate alarm.
Table 2 lists the allowable DMT bit rate ranges and default values.
Table 2 Allowable Ranges and Default Values for DMT Bit Rates
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Caution This command causes the port to retrain when you change the value of the bit rate parameter. |
Setting a parameter to its current value does not cause a retrain. If a port is training when you change the parameter, the port stops training and retrains to the new parameter.
Examples
The following command example sets the maximum interleaved bit rate of the default profile to 3200 kbps downstream and 640 kbps upstream:
Related Commands
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To set upstream and downstream FEC check (redundancy) bytes, use the dmt-checkbytes profile configuration command. To reset this command to the default value, use the no form of this command.
Syntax Description
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Defaults
Interleaved Downstream and Upstream: 16
Fast Downstream and Upstream: 0
Command Modes
Command History
Usage Guidelines
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Caution This command causes the port to retrain when you change the check-bytes parameter. |
Setting a parameter to its current value does not cause a retrain. If a port is training when you change the parameter, the port untrains and retrains to the new parameter.
Conditions on the line, the configured bit rate, and the capabilities of the ATU-R CPE affect the achievable value for this parameter. As a result, the check-bytes value to which the line trains might be smaller than the value you configure. If you want to use more check bytes than the system allows, use the dmt bitrate command to reduce the bit rate.
Use the command show dsl interface atm slot# /port# to display the configured and actual check-bytes values for the connection.
Examples
The following command example sets the interleaved FEC check bytes for the default profile to 12 downstream and 6 upstream.
Related Commands
To set upstream and downstream signal-to-noise ratio (SNR) margins for a DMT profile, use the dmt margin command. To reset this command to the default value, use the no form of this command.
Syntax Description
Defaults
Command Modes
Command History
Usage Guidelines
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Caution This command causes the port to retrain when you change the parameter. |
Setting a parameter to its current value does not cause a retrain. If a port is training when you change this value, the port untrains and retrains to the new value.
Examples
The following command example sets the SNR margins of the default profile to 12 dB downstream and 6 dB upstream:
Related Commands
To force a port not to retrain when actual bit rates fall below the values configured in the dmt bitrate minimum command, use the dmt minrate-blocking command. To disable dmt minrate-blocking, use the no form of the command.
Syntax Description
This command has no arguments or keywords.
Defaults
The default configuration, no dmt minrate-blocking, generates a minor alarm when the bit rates on a DMT port violate the minimum allowed bit rates specified in the dmt bitrate minimum command (if alarms are enabled in the DSL profile).
Command Modes
Command History
Usage Guidelines
To specify the bit rate below which a DMT port will not retrain, use the dmt bitrate minimum command.
Examples
The following command example enables dmt minrate-blocking:
Related Commands
To set the overhead framing mode, use the dmt overhead-framing command. To reset this command to the default value, use the no form of this command.
Syntax Description
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Defaults
Mode3 is the only supported mode. If you specify another mode, the mode is forced to mode3.
Command Modes
Command History
Usage Guidelines
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Note Conditions on the line and the capabilities of the ATU-R CPE affect the achievable value for this parameter. As a result, the overhead framing value to which the line trains might not be the same as the value you configure. |
There are two types of ADSL framing:
There are also two versions of full overhead:
The ADSL framing mode is Mode 3 which specifies reduced overhead framing with merged fast and sync bytes using either the fast or interleaved latency buffer.
There is one overhead byte per frame.
If, during the training sequence, the ATU-R indicates a lower framing structure value than that specified by the ATU-C, the ATU-C falls back to the framing structure number indicated by the ATU-R.
Management requirements drive the determination of overhead (full or reduced). Full overhead provides more bandwidth to the embedded operations channel (EOC), enabling higher polling rates. However, reduced overhead provides enough EOC bandwidth to satisfy typical applications.
The dmt overhead-framing command does not cause port retrain when you change the parameter.
Examples
The following command example sets the overhead framing mode in the profile named 8xDMT/ISDN:
Related Commands
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DMT rate adaptation monitors upstream and downstream DMT ports for signal-to-noise ratio (SNR) margins during specified time intervals. If an unacceptable SNR margin is detected, the port is retrained at a lower bit rate to improve the SNR margins. To enable rate adaptation on a DMT port, use the dmt rate-adaptation enable command at the DSL profile configuration prompt. To disable dmt rate adaptation, use the no form of the command.
This command has no arguments or keywords.
Defaults
Enabling dmt rate-adaptation assigns the default values to dmt rate-adaptation interval and dmt rate-adaptation margin commands. For information on the default values of dmt rate-adaptation interval and dmt rate-adaptation margin, see the "dmt rate-adaptation interval" section and the "dmt rate-adaptation margin" section.
Command Modes
Command History
Usage Guidelines
If you wish to modify the default configuration of the dmt rate-adaptation interval and dmt rate-adaptation margin, see the "dmt rate-adaptation interval" section and the "dmt rate-adaptation margin" section.
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Note If line conditions improve, the line does not automatically drop and retrain to a higher bit rate. The administrator must execute a shut command then a no shut command on the port to retrain to a higher bit rate. |
Examples
The following command example enables DMT rate-adaptation with default interval and margin values:
Related Commands
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To change the intervals during which a DMT port is monitored for signal-to-noise ratio (SNR) margins, use the dmt rate-adaptation interval command in DSL profile configuration mode. To disable dmt rate-adaptation interval, use the no form of this command.
Syntax Description
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Defaults
Following are the default settings for the dmt rate-adaptation interval:
Command Modes
Command History
Usage Guidelines
Use the dmt rate-adaptation interval to specify the frequency at which line margins are checked on a DMT port. The dmt rate-adaptation interval command works in conjunction with the dmt rate-adaptation margin command. If, for the duration of time specified in the dmt rate-adaptation interval command, the actual SNR margins on a port remain lower than the margins configured in the dmt rate-adaptation margin command for the duration of time specified in the dmt rate-adaptation interval command, the line drops and retrains to a lower bit rate, to improve SNR margin quality on the line.
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Note If line conditions improve, the line does not automatically drop and retrain to a higher bit rate. The administrator must execute a shut then a no shut on the port to retrain to a higher bit rate. |
Examples
The following command example configures a downstream monitoring interval of roughly 60 to 150 seconds, and an upstream monitoring interval of 20 seconds:
Related Commands
To configure the minimum acceptable SNR margins on a DMT port, use the dmt rate-adaptation margin command in DSL profile configuration mode. The minimum acceptable SNR margins on a DMT port force the port to retrain when bad margins exist for the duration of the dmt rate-adaptation interval. To disable dmt rate-adaptation margin, use the no form of this command.
Syntax Description
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Defaults
The default configuration is derived from the no dmt rate-adaptation enable command. This specifies minimum upstream and downstream SNR margins of 0 dB.
Command Modes
Command History
Usage Guidelines
Use the dmt rate-adaptation margin command to configure the acceptable SNR margin thresholds on a specified port. The dmt rate-adaptation margin command works in conjunction with the dmt rate-adaptation interval command. If, for the duration of time specified in the dmt rate-adaptation interval command, the actual SNR margins on a port remain lower than the margins configured in the dmt rate-adaptation margin command, the line drops and retrains to a lower bit rate, to improve SNR margin quality on the line.
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Note If line conditions improve, the line does not automatically drop and retrain to a higher bit rate. The administrator must execute a shut then a no shut on the affected port to retrain to a higher bit rate. |
Examples
The following command example shows how to configure dmt rate-adaptation margin:
To provision a slot for a specific card type, or to change the line coding for a flexi line card, use the slot command.
Syntax Description
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Defaults
Command Modes
Command History
Usage Guidelines
Use the slot command to provision a slot for a line card.
Card mismatch error conditions include the following:
If you attempt to provision an empty slot, the major alarm "MODULE-MISSING" is asserted.
The 8xDMT over ISDN line card is spectrally incompatible with both the 8-port IDSL line card and the 4-port SDSL (STU-C) line card. If you install spectrally incompatible cards in the same chassis, the lines served by those cards can suffer reduced performance. For best performance in a chassis with a mixture of line card types, always install 8xDMT over ISDN line cards on one side of the chassis and IDSL and SDSL cards on the opposite side.
Examples
The following command example provisions slot 30 for an 8xDMT over ISDN line card:
Related Commands
ADSL—asymmetric digital subscriber line. A DSL technology in which the transmission of data from server to client is much faster than the transmission from the client to the server.
ADSL Transmission Unit—Central Office—See ATU-C.
ADSL Transmission Unit—Remote—See ATU-R.
asymmetric digital subscriber line—See ADSL.
Asynchronous Transfer Mode—See ATM.
ATM—Asynchronous Transfer Mode. A cell-based data transfer technique in which channel demand determines packet allocation. ATM offers fast packet technology, and real-time, demand-led switching for efficient use of network resources.
ATU-C—ADSL Transmission Unit—Central Office. Special electronics in support of ADSL and placed in the carrier's CO. The ATU-C has a matching unit on the subscriber premise in the form of an ATU-R. The two units, in combination, support a high data rate over UTP copper cable local loops.
ATU-R—ADSL Transmission Unit—Remote. Special electronics in support of ADSL and placed in the customer's premises. The ATU-R has a matching unit in the carrier's CO in the form of an ATU-C. The two units, in combination, support a high data rate over UTP copper cable local loops.
bridge—A device that connects two or more physical networks and forwards packets between them. Bridges can usually be made to filter packets, that is, to forward only certain traffic. Related devices are: repeaters which simply forward electrical signals from one cable to the other, and full-fledged routers which make routing decisions based on several criteria. See router.
CBOS—Cisco Broadband Operating System. An operating system that users access to configure and operate Cisco products.
chassis—The card cage (housing) where modules are placed.
CPE—customer premises equipment.
DDTS—Cisco Distributed Defect Tracking System. Cisco uses DDTS to track bugs in a variety of products, including router software, communication server software, and network management software. DDTS is also used to track bugs in some hardware and microcode products, and for bugs in some internal tools, including the automated test software and various software tools.
digital signal level 3—See DS3.
Distributed Defect Tracking System—See DDTS.
DMT—Discrete Multi-Tone. An ADSL modulation scheme defined by the ANSI T1.413 standard. DMT is a multicarrier modulation scheme where incoming data is collected and then distributed over a large number of small individual channels, each of which uses a form of Quadrature Amplitude Modulation (QAM). DMT creates the channels using a digital technique known as Discrete Fast-Fourier Transform.
downstream rate—The line rate for return messages or data transfers from the network machine to the CPE.
DS-3—Digital signal level 3. A framing specification used for transmitting digital signals at 44.736 Mbps on a T3 facility.
DSLAM—digital subscriber line access multiplexer. A device that concentrates digital subscriber line signals at the telephone service provider location and multiplexes them onto the broadband wide area network. Replaces ADSLAM.
EOC—embedded operations channel.
ETSI—European Telecommunications Standards Institute. ETSI is a non-profit organization producing voluntary telecommunications standards used throughout Europe, some of which have been adopted by the EC as the technical base for Directives or Regulations.
frame—A packet as it is transmitted over a serial line. The term derives from character-oriented protocols that involved the addition of special start-of-frame and end-of-frame characters for packet transmission.
FTP—File Transfer Protocol. The Internet protocol (and program) used to transfer files between hosts.
G.992.2—The ITU standard for line coding and framing for splitterless, reduced spectrum ADSL. Also known as G.lite.
G.994.1—The ITU standard for signaling, identification, and negotiation between broadband systems; an integral part of G.dmt and G.lite. Also known as G.hs.
G.997.1—The ITU standard for performance monitoring on DMT access technologies.
G.hs—Pseudonym for G.994.1 HandShake (hs).
handshake—Part of the procedure to set up a data communications link. The handshake can be part of the protocol itself or an introductory process. The computers that are to talk to each other set out the conditions they can operate under. Sometimes, the handshake is just a warning that a communication is imminent.
IETF—Internet Engineering Task Force. Task force consisting of over 80 working groups responsible for developing Internet standards.
IP—Internet Protocol. The network layer protocol for the Internet Protocol suite.
IP address—The 32-bit address assigned to hosts that want to participate in a TCP/IP Internet.
ISDN—Integrated Services Digital Network. Communication protocol offered by telephone companies that permits telephone networks to carry data, voice, and other source traffic.
ITU—International Telecommunications Union; a telecommunications standards body.
LODS—loss of delay synchronization.
loopback—A diagnostic test that returns the transmitted signal to the sending device after it has passed through a network or across a particular link. The returned signal can be compared to the transmitted signal and any discrepancies can be used to trace the fault. When trying to locate a faulty piece of equipment, you can repeat loopbacks, eliminating satisfactory equipment, until the problem is found.
Management Information Base—See MIB.
MIB—Management Information Base. A collection of objects that can be accessed through a network management protocol, such as SNMP or CMIP (Common Management Information Protocol).
NI-2—A second generation network interface card.
PVC—permanent virtual connection. A fixed virtual connection between two users. The public data network equivalent of a leased line. The creation of a PVC requires no call setup or clearing procedures.
QAM—Quadrature Amplitude Modulation.
route—The path that network traffic takes from its source to its destination. The route a datagram follows can include many gateways and many physical networks. In the Internet, each datagram is routed separately.
router—A system responsible for making decisions about which of several paths network (or Internet) traffic will follow. To do this, it uses a routing protocol to gain information about the network and algorithms to choose the best route based on several criteria known as "routing metrics." See also bridge.
routing table—Information stored in a router that contains network path and status information. It is used to select the most appropriate route to forward information.
Simple Network Management Protocol—See SNMP.
slot—A numbered location within a chassis capable of housing a module.
SNMP—Simple Network Management Protocol. The network management protocol of choice for TCP/IP-based internets.
SVC—switched virtual connection. A temporary virtual connection between two users.
T1.413—The ANSI standard for line coding and framing for full rate ADSL.
TCP—Transmission Control Protocol. The major transport protocol in the Internet suite of protocols providing reliable, connection-oriented, full-duplex streams.
Telnet—The virtual terminal protocol in the Internet suite of protocols. It allows users of one host to log in to a remote host and act as normal terminal users of that host.
TFTP—Trivial File Transfer Protocol. A simple file transfer protocol (a simplified version of FTP) that is often used to boot diskless workstations and other network devices such as routers over a network (typically a LAN). It does not offer password security.
training—The procedure used by the ATU-C and ATU-R to establish an end-to-end ADSL connection.
training mode—A characteristic of a router that allows it to use RADSL technology to adjust its line speed according to noise conditions on the transmission line.
Transmission Control Protocol—See TCP.
trellis encoding—A channel coding technique which provides forward error correction capability.
Trivial File Transfer Protocol—See TFTP.
twisted pair—Two insulated copper wires twisted together with the twists or lays varied in length to reduce potential signal interference between the pairs.
upstream rate—The line rate for message or data transfer from the source machine to a destination machine on the network. Also see downstream rate.
VC—virtual circuit. A logical circuit created to ensure reliable communication between two network devices. A virtual circuit is defined by a VPI/VCI pair, and can be either permanent (PVC) or switched (SVC). In ATM, a virtual circuit is called a virtual channel. Sometimes abbreviated VC. See also PVC, SVC, VCI, and VPI.
VCI—virtual channel identifier. A 16-bit field in the header of an ATM cell. The VCI, together with the VPI, is used to identify the next destination of a cell as it passes through to the ATM switch. Sometimes called virtual channel connection. See also VPI.
VPI—virtual path identifier. An 8-bit field in the header of an ATM cell. The VPI, together with the VCI, is used to identify the next destination of a cell as it passes through the network. See also VCI.
Posted: Mon Sep 15 08:51:38 PDT 2003
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