Cisco Systems C819HG4GVK9 Configuring Compression of HDLC Data, Using the NRZI Line-Coding Format

Chapter 8 Configuring the Serial Interface

How to Configure Serial Interfaces

Configuring Compression of HDLC Data

You can configure point-to-point software compression on serial interfaces that use HDLC encapsulation. Compression reduces the size of a HDLC frame via lossless data compression. The compression algorithm used is a Stacker (LZS) algorithm.

Compression is performed in software and might significantly affect system performance. We recommend that you disable compression if CPU load exceeds 65 percent. To display the CPU load, use the show process cpu EXEC command.

If the majority of your traffic is already compressed files, you should not use compression.

To configure compression over HDLC, use the following commands in interface configuration mode.

SUMMARY STEPS

1.encapsulation hdlc

2.compress stac

DETAILED STEPS

	Command or Action	Purpose
Step 1	encapsulation hdlc	Enables encapsulation of a single protocol on the
		serial line.
	Example:
	Router(config-if)# encapsulation hdlc
Step 2	compress stac	Enables compression.
	Example:
	Router(config-if)# compress stac

Using the NRZI Line-Coding Format

The nonreturn-to-zero (NRZ) and nonreturn-to-zero inverted (NRZI) formats are supported on the Cisco 819 serial ports.

NRZ and NRZI are line-coding formats that are required for serial connections in some environments. NRZ encoding is most common. NRZI encoding is used primarily with EIA/TIA-232 connections in IBM environments.

The default configuration for all serial interfaces is NRZ format. The default is no nrzi-encoding.

To enable NRZI format, use one of the following commands in interface configuration mode.

SUMMARY STEPS

1.nrzi-encoding

Cisco 819 Series Integrated Services Routers Software Configuration Guide

OL-23590-02 8-9