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Cisco 819 Series Integrated Services Routers Software Configuration Guide
OL-23590-02
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
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
Command or Action Purpose
Step 1
encapsulation hdlc
Example:
Router(config-if)# encapsulation hdlc
Enables encapsulation of a single protocol on the
serial line.
Step 2
compress stac
Example:
Router(config-if)# compress stac
Enables compression.