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Feature History
12.2(2)XA This feature was introduced on Cisco AS5350 and Cisco AS5400 universal gateways running NextPort firmware. 7/18/2001 This feature was introduced on the Cisco AS5300 universal access server running Cisco MICA Portware Version 2.9.1.0.
Release
Modification
This feature module introduces the V.44 Lempel-Ziv-Jeff-Heath (LZJH) compression algorithm International Telecommunication Union Telecommunication Standardization Sector (ITU-T) standard on Cisco MICA portware platforms using Cisco IOS Software Release 12.2(2)XA.
This document includes the following sections:
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 Cisco MICA portware 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 Cisco MICA portware is responsible for the ITU implementation of V.44 and the collection of statistics related to the new feature.
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.
New token errors are derived from the V.42bis and V.44 recommendations:
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Note Most V.44 disconnect reasons report additional data in the 8-byte diagnostic field shown in the modem logs. |
V.44 is enabled and disabled using standard AT commands and S-registers. 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 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 1. 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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Note Some clients do not support compression in only one direction. Such modems will disconnect if the server is configured only for compression in one direction. |
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.
| Name | Register | Index | Default | Description |
|---|---|---|---|---|
Data Compression | S21 | MICA 11 | 0xf | Bit 2: V.44 Tx Bit 3: V.44 Rx |
V.44 Max Tx Codewords | S65 | MICA66 | 2048 | 256-2048 |
V.44 Max Rx Codewords | S66 | MICA67 | 2048 | 256-2048 |
V.44 Max Tx String Length | S67 | MICA68 | 255 | 32-255 characters |
V.44 Max Rx String Length | S68 | MICA69 | 255 | 32-255 characters |
V.44 Max Tx History Size | S69 | MICA70 | 15000 | 512-15000 bytes |
V.44 Max Rx History Size | S70 | MICA71 | 15000 | 512-15000 bytes |
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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Note ATS21 is a bit-mapped register, and combinations of compression standards are valid. |
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 MICA 6-Port Modules.
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
Cisco MICA 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 Cisco MICA features.
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Note The default string length is adjustable via S67 and S68 |
Standards
MIBs
To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, go to the Cisco MIB web site on Cisco.com at the following URL:
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
RFCs
No new or changed RFCs are supported by this feature.
None
Refer to the following documentation for further information about V.92 using Cisco MICA technology:
None
None
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 an 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, Modem On Hold, and PCM Upstream.
Posted: Thu Aug 30 17:25:05 PDT 2001
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