V.42/V.42bis/V.44/MNP2-4/MNP 5/MNP 10

VOCAL Technologies modem data protocol software implements the ITU V.42 error correction protocols. These protocols include both LAPM (Link Access Procedure for Modems) and an alternate protocol. The alternate protocol, as described by V.42, is the MNP (Microcom Networking Protocol) data protocol, classes 2 through 4. LAPM and MNP 2-4 implement end-to-end error correction through an automatic repeat-transmission request algorithms.

MNP 2 is an error correction algorithm using data packets of asynchronous characters over a full-duplex modulation. MNP 3 introduced the use of HDLC based synchronous data packets. MNP 4 can be used with or without the MNP 3 feature; it provides for the use of slightly smaller (through optimized headers) data and acknowledge packets.

The modem data protocol software provides data compression capability with ITU V.42bis and MNP 5 algorithms. The V.42bis data compression protocol is sometimes used standalone. Classically, V.42bis has been used with LAPM and MNP5 is used with MNP2-4.

Features

  • Modem MIB Support (RFC 1696)
  • Extended Buffered Mode Support for V.80 features
  • Extended Buffered Mode Supports V.110 rate adaptation
  • Extended Buffered Mode Supports PPP Framing (RFC 1662)
  • Detection Phase
  • Automatic LAPM detection
  • MNP autoreliable mode
  • Buffered Mode (Speed Matching) provides modem-to-modem flow control
  • Direct Mode support
  • Extended Buffered Mode Support for V.80 features
  • V.42bis compression: provides up to 4:1 compression
  • MNP5 compression: provides up to 2:1 compression
  • Multi-tasking environment compatible

Configuration

  • VOCAL's Overall Modem Controller (OMC) Layer provides coordinated data modulation/data protocol operation relative to startup, shutdown, modulation retrains and modulation renegotiations.
  • V.14/HDLC/Binary/FSK SART layer support for buffered mode
  • V.14/FSK SART layer support for asynchronous MNP mode
  • HDLC SART layer support for LAPM, synchronous MNP modes
  • V.42 support for ADP/ODP generation/detection, automatic protocol detection mechanisms
  • System configuration supports the overlay of LAPM, MNP 2-4, Buffered and Direct Modes for maximum program and data memory efficiency.
  • System configuration supports the overlay of V.42bis and MNP5 for maximum program and data memory efficiency.
  • System configuration supports the overlay of data protocols with fax protocols for maximum program and data memory efficiency.
  • System configuration supports compile-time selectable V.42bis dictionary size and string size.
  • VOCAL's OMC Layer can be used standalone in a non command-set environment (although a variety of commands sets are available from VOCAL)
  • Compatible with ITU and Bell data modulations through V.90 (also available from VOCAL).

ITU Recommendation V.42

ITU Recommendation V.42bis