Protocol Analyzer Basics and Applications

This page covers the basics of a protocol analyzer and its applications in protocol analysis for various interfaces such as RS232, RS485, I2C, HTTP, etc. It is also commonly referred to as a protocol sniffer.

Protocol Analyzer Basics

A Protocol Analyzer is an equipment used to perform protocol analysis. Its functionality isn’t limited to a specific standard, technology, or interface type. Instead, it’s applicable to multiple standards/technologies and used for various interfaces, including RS232, RS485, and I2C.

Figure-1: Protocol analyzer

For example, in a GSM system, protocol analyzers are connected to BTSs, MSCs, and BSCs. This allows them to capture traces in case of failures within these subsystems, aiding in debugging and troubleshooting. The captured logs are then provided to central office locations, where they are used by software and hardware teams for further analysis. This log analysis can be performed either manually or using software tools. Logs captured using a protocol analyzer are invaluable for offline system analysis. Due to the higher cost, it’s typically not feasible to place protocol analyzers at all network interfaces to capture logs.

Protocol Analyzer Features

• Comprehensive Measurements: Protocol analyzers perform measurements from the lower layers all the way up to the higher layers, helping analyze complete call traces.
• Software Support: Additional software applications facilitate quick analysis of the captured logs.
• Customization: They can be easily customized for any standards/technologies with modifications in the protocol stack.

Models 4951C & 4952A from Hewlett Packard are well-known protocol analyzers for analyzing Async, SDLC or NRZI, BSC, HDLC, SNA, X.25, DDCMP, and other user-defined protocols. They allow users to monitor and decode data transmission locally and remotely using a LAN interface. These models support 19.2kbps asynchronous and 64kbps synchronous interfaces.

Modern wireless systems consist of RF, layer-1 (physical layer), MAC layer, Upper layers (TCP/IP or UDP/IP), and application layer protocols. Pinpointing problems can be difficult using only RF test and measurement tools. Therefore, low-level protocol analysis using a protocol analyzer becomes essential.

Protocol Analyzer Applications

Protocol Analyzers are used extensively in various systems for protocol analysis and troubleshooting during protocol stack implementation. This includes systems using RS232, RS485, and I2C interfaces.