Cisco LAN2LAN Software

Document ID: 14996

Contents

Introduction
Prerequisites
      Requirements
      Components Used
Facts
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Introduction

This document discusses data compression facts.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

This document is not restricted to specific software and hardware versions.

Facts

The data compression module (DCM) is installed as a daughter board on the LAN²LAN adapter. The software automatically detects the presence of the DCM and enables data compression subject to these conditions:

1. The DCM must pass the quick look diagnostics, which are run prior to loading the operational software to the adapter.

2. When a line that might use data compression is activated, the remote LAN²LAN must also offer data compression, and the line must operate at 128 Kbps or less.

3. If both DCMs are operational and the line speed measured at both ends is 128 Kbps or less, each end reports:

   Line in service with compression enabled

4. If the DCM fails diagnostics, then that end does not offer compression to the remote end and reports:

   Line in service

5. If the line speed is measured at greater than 128 Kbps or if the remote end does not offer compression (no DCM installed, failed diagnostic, speed greater than 128 Kbps), then that end reports:

   Line in service with compression disabled

6. The compression ratio reported for a line is for packets transmitted from that end. You need to look at both ends of the line to get the full picture. The figure reported is a rolling average. It does not immediately react to changes in packet characteristics, but, rather, it smooths out dynamic fluctuations. In fact, if no traffic is flowing, the figure changes very slowly, since it only updates for every 5,000 bytes counted.

7. If you use NetWare v3.x Monitor, the compression ratio figure shown must be divided by 1,000 to obtain the ratio (Monitor displays only integers).

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