Table Of Contents
Related Features and Technologies
Supported Standards, MIBs, and RFCs
V.44 LZJH Compression for Cisco AS5350, Cisco AS5400, and Cisco AS5850 Universal Gateways, and Cisco AS5800 Universal Access Servers
Feature History
This feature module introduces the V.44 Lempel-Ziv-Jeff-Heath (LZJH) compression algorithm International Telecommunication Union Telecommunication Standardization Sector (ITU-T) standard on NextPort/DFC-108NP-bearing platforms using Cisco IOS Release 12.2(2)XB1 or 12.2(11)T.
This document includes the following sections:
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Supported Standards, MIBs, and RFCs
Feature Overview
V.44 LZJH is a new compression standard based on Lempel-Ziv that uses a new string-matching algorithm that increases upload and download speeds to make Internet access and Web browsing faster. The V.44 call success rate (CSR) is similar to V.42bis with significant compression improvement for most file types, including HTML files. V.44 applies more millions of instructions per second (MIPS) than V.42bis toward the same application data stream and yields better compression rates in almost any data stream in which V.42bis shows positive results.
V.44 supports automatic switching between compressed and transparent modes on NextPort DFC-108NP-bearing platforms. Automatic switching allows overall performance gain without loss in throughput for file streams that are not compressible.
V.44 is globally controlled through dialed number ID service (DNIS), calling line ID (CLID), and resource pool manager server (RPMS) virtual groups, and performance improvement is determined by the LZJH algorithms. The NextPort Dial Feature Card (DFC) is responsible for the ITU implementation of V.44 and the collection of statistics related to the new feature.
The Cisco AS5800 uses the NextPort high density dial termination card to implement this feature. Both voice and dial technologies are supported when used in a Cisco 5850 universal gateway.
To support V.44 LZJH compression, the control switch module (CSM) has been modified. MIBs that show the status of V.42bis have been extended to show V.44 configuration status. New disconnect reasons help manage V.44 session status and debugging.
Disconnect Reasons
New token errors are derived from the V.42bis and V.44 recommendations:
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V.44 compression errors are defined by the following disconnect reasons:
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AT Commands and S-Registers
V.44 compressor/decompressor optimizes throughput and the call success rate (CSR) using standard AT command interface. New AT commands are provided so that V.44 can be enabled or disabled at the modem level. Modemcaps (dial in) or chat scripts (dial out) are required to enable or disable V.44 globally on the access server.
The AT command interface supports new S-registers for tuning V.44 negotiation parameters and lets you monitor V.44 configuration and session status. The ATSn=v AT command is used to configure V.44, and the ATSn?, AT%R, and AT\S commands are used for obtaining V.44 status. These commands modify the operation of S21 to enable and disable the algorithm. Table 1 shows the S21 register values, while Table 2 shows additional S-register values used with the V.44 feature. V.44 is enabled by default.
Table 1 Changed S-Register Values
Data Compression
S21
0x800b
15
Bit 2: V.44 Tx
Bit 3: V.44 Rx
For more information about the new S-registers and AT commands that control the V.44 feature, refer to AT Command Set and Register Summary for NextPort Platforms.
Benefits
Increased Modem Throughput
V.44 provides increased modem throughput for compressible data streams. V.44 provides speedier downloads and uploads for most data stream types. For example, e-mail, Web page, .rtf, and ASCII downloads and uploads are noticeably faster. This speed enhances modem-centered use of ports without requiring user input.
No Negative Impact on Modem Density or Systems Not Running V.44
DFC-108NP-bearing modems support V.44 without negatively impacting other modem channels, other modem features, or modem density. There is no impact on software subset feature packages or other existing NextPort features.
Restrictions
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Related Features and Technologies
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Related Documents
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Supported Platforms
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Determining Platform Support Through Cisco Feature Navigator
Cisco IOS software is packaged in feature sets that support specific platforms. To get updated information regarding platform support for this feature, access Cisco Feature Navigator. Cisco Feature Navigator dynamically updates the list of supported platforms as new platform support is added for the feature.
Cisco Feature Navigator is a web-based tool that enables you to determine which Cisco IOS software images support a specific set of features and which features are supported in a specific Cisco IOS image. You can search by feature or release. Under the release section, you can compare releases side by side to display both the features unique to each software release and the features in common.
To access Cisco Feature Navigator, you must have an account on Cisco.com. If you have forgotten or lost your account information, send a blank e-mail to cco-locksmith@cisco.com. An automatic check will verify that your e-mail address is registered with Cisco.com. If the check is successful, account details with a new random password will be e-mailed to you. Qualified users can establish an account on Cisco.com by following the directions at http://www.cisco.com/register.
Cisco Feature Navigator is updated regularly when major Cisco IOS software releases and technology releases occur. For the most current information, go to the Cisco Feature Navigator home page at the following URL:
Availability of Cisco IOS Software Images
Platform support for particular Cisco IOS software releases is dependent on the availability of the software images for those platforms. Software images for some platforms may be deferred, delayed, or changed without prior notice. For updated information about platform support and availability of software images for each Cisco IOS software release, refer to the online release notes or, if supported, Cisco Feature Navigator.
Supported Standards, MIBs, and RFCs
Standards
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MIBs
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To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
http://tools.cisco.com/ITDIT/MIBS/servlet/index
If Cisco MIB Locator does not support the MIB information that you need, you can also obtain a list of supported MIBs and download MIBs from the Cisco MIBs page at the following URL:
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
To access Cisco MIB Locator, you must have an account on Cisco.com. If you have forgotten or lost your account information, send a blank e-mail to cco-locksmith@cisco.com. An automatic check will verify that your e-mail address is registered with Cisco.com. If the check is successful, account details with a new random password will be e-mailed to you. Qualified users can establish an account on Cisco.com by following the directions found at this URL:
RFCs
No new or changed RFCs are supported by this feature.
Prerequisites
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Configuration Tasks
V.44 is enabled and disabled using the standard AT commands and S-registers. The AT command interface supports new S-registers for tuning V.44 negotiation parameters and for providing V.44 configuration and session status. V.44-capable portware defaults to all data compressions enabled (S21=15). With this setting, if V.42 frames are detected, V.44 negotiation is attempted first with a fallback to V.42bis. If MNP frames are detected, V.42bis is negotiated with a fallback to MNP5.
When configurations other than the default are required, use the AT interface to set V.44-specific S-registers to one of the values detailed in Table 4. To configure V.44 compression in only the TX direction, for example, set S21 to 4. To configure V.44 in only the Rx direction, set S21 to 8.
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Use the ATSn=v command to configure V.44. The following AT commands can be used for obtaining V.44 status: ATSn?, AT%R, and AT\S.
The ATSn=v command sets S-registers that tune V.44 session parameters.
To disable V.44, enter the ATSn=v command to set S-register 21 to a value that does not support V.44 (0, 1, 2, or 3).
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Configurations have precedence in the following order: V.44, V.42bis, none, or V.42, MNP5, none.
For more information about the AT commands and S-registers used to control the V.44 feature, refer to AT Command Set and Register Summary for NextPort Platforms.
Configuration Examples
None
For information about configuration, refer to the following documents:
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Command Reference
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Glossary
CLID—calling line ID.
CSMv6—Mindspeed modem hardware solution.
CSR—call success rate.
DFC—dial feature card.
DNIS—dialed number ID service.
DSP—Digital Signal Processor. Microprocessor on which the modulation/demodulation process is carried out.
host—The platform in which the modem is installed. Usually used in the context of an interface declaration or definition. Cisco IOS software is enabled on the host.
ITU-T—International Telecommunication Union Telecommunication Standardization Sector.
Lempel-Ziv algorithm (LZ)—A compression algorithm, based on a dynamically encoded dictionary, that replaces a continuous stream of characters with codes. The symbols represented by the codes are stored in memory in a dictionary-style list. LZ-style compression is used in a number of compression algorithms, such as Stacker (STAC) compression. In contrast, statistical compression methods use a fixed and, oftentimes, a non adaptive encoding method, which is best used where data is consistent and predictable.
LZJH—Lempel-Ziv-Jeff-Heath data compression algorithm used in V.44.
MICA—Modem ISDN channel aggregation. Modem module and card used in the Cisco AS5300 universal access servers. A MICA modem provides an interface between an incoming or outgoing digital call and ISDN telephone line; the call does not have to be converted to analog, as it does with a conventional modem and an analog telephone line. Each line can accommodate, or aggregate, up to 24 (T1) or 30 (E1) calls.
MICA modem—An installed Cisco MICA system. A single modem instance on that system.
MIPs—millions of instructions per second.
modem—A device with generic modem functionality. A single modem instance on a Cisco MICA system. The modem with which the host is currently conversing (the host knows with which modem it is exchanging mail and commands at any particular time). Command descriptions might say that a command is issued to "the modem."
MOH—Modem on Hold functionality specified in V.92.
NextPort—Device driver architecture for Cisco IOS software that supports the NextPort hardware and software interfaces. Supports the Universal Port concept.
PCM—pulse code modulation.
universal port—Concept of a single device that can terminate one digital signal level zero (DS-0) with a data modem, fax modem, ISDN, or voice solution.
QC—Quick Connect functionality specified in V.92
RPMS—resource pool manager server.
V.44—ITU modem standard for LZJH data compression algorithm.
V.92—ITU modem standard that contains Quick Connect and Modem On Hold.
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