Modern Protocol Analyzers Monitor And Simulate Multiple Data Streams

Being well-connected today depends much more upon selecting the same protocols in your LAN server and client NICs than on the ivy-ness of your alma mater.

The rate of increase in communications traffic is staggering. In 1997, the number of service providers in North America increased from 2,300 to 4,000.1 Last year, approximately 98.6 million second-generation digital cell phones were produced.2 By 2002, it is estimated that 328 million people will be using the internet.3

When third-generation GSM phones are available, they will support up to 2 Mb/s data rates. That’s enough speed for internet downloads and video conferencing wherever you may be. So when you consider the increased internet and phone usage, digital video, legacy LAN and WAN traffic, and the proliferation of new communications networks throughout industry, it’s easy to anticipate the occurrence of system and signal conflicts.

Enter the Protocol Analyzer

Data generated by several distinct types of sources, each with its QoS delay and timing requirements, may move through many transmission media and modes before reaching its destination. For example, a common application of ATM is LAN emulation. In this application, the broadband, point-to-point, fixed-size cell-based ATM network carries lower-speed, shared-medium, variable-size packet-based LAN data.

Industry experts agree that a protocol analyzer must observe traffic simultaneously on at least two networks, usually with different protocols. In the case of ATM, you want to compare data on the LAN with the data after SAR.

“If there is a physical-layer or protocol-related problem on either the LAN or the WAN side, it probably can be detected by an analyzer connected to just one network segment at a time,” commented Hartmut Marschall, senior sales engineer at Radcom. “However, if the source of the problem is the interoperability device such as a router or switch, the only sure method of identifying it as such is simultaneously monitoring both sides.”

Mr. Marschall added, “The analyzer must display the corresponding latency time of the router to the user. Simultaneous capture allows exact comparison of both sides of the interoperability device, providing verification that the router is the bottleneck.”

Of course, there may be more than two interfaces involved. “For manufacturers of telecommunications equipment, it is very important to be able to automatically test all interfaces of the equipment they build,” pointed out Joerg Ehrhardt, V5.x product manager at Tektronix. “These interfaces may use different protocols on a different physical interface.” An example of an instrument with this capability is the Tektronix K1205 Signaling Protocol Analyzer that simultaneously monitors up to 16 physical interfaces and 32 channels.

“Often, it is necessary to examine multiple network and protocol performance remotely,” said Dave Ushler, product marketing manager at Digitech. The embedded client/server application in Digitech’s new remote-control package allows source selection, analysis, and display of results in multiple windows.

Most manufacturers address the variety of physical interfaces by offering separate, plug-in LIMs. There are no more than 15 to 20 popular types of LIMs, but the number of protocols that may be encountered is more than 250 and growing. As an example, there have been several recent changes to UNI signaling protocols. Each protocol defines many types of messages.

To deal with evolving standards for B-ISDN message handling, Hewlett-Packard implemented a special MDL and a compiler in the HP E4214A Broadband ISDN UNI Signaling Test Software.⁴ Compared with hard-coded approaches, this solution is more general because new protocols can be defined using the MDL without actual application changes.

A similar capability to handle new protocols was described by Avi Zamir, Radcom’s US president. “Due to the modular design of our analyzers, we can provide customers with up-to-date solutions long after their initial purchase,” he said. “By simply installing a new version of the software, our analyzers address today’s applications and have the capability to test technologies which didn’t exist when the analyzers were bought.”

Network performance is measured using statistics: How much of the total bandwidth is being used for how long, at what times during the day, and by whom? How many cells were discarded due to UPC and at which UNIs? What is the BER exhibited by a particular channel?

For post-acquisition measurements to be meaningful, you must capture 100% of the data you intend to analyze. As a result, this requirement has analyzer-speed and memory-size implications. By selecting specific types of information, real-time filtering reduces the captured data rate. But if you need to capture all traffic, then your analyzer must keep up with the maximum data rate–up to 155.52 Mb/s for ATM networks, for example.

Monitoring traffic implies live generation of statistics. Digitech’s Mr. Ushler included both live and post-acquisition analysis when he said, “Users require real-time data display, decode display, and capture to RAM and hard disk.”

After all the relevant data has been captured, “Post-capture analysis can take place on a number of PCs,” added Mr. Marschall. “Using remote-control software to access the analyzer, multiple engineers can examine the data in parallel.”

Simulation

In addition to monitoring and interpreting data flow between devices or networks, a protocol analyzer must simulate part of a network. In this way, you can completely control the environment and data used to test a network component such as a switch. For example, the Radcom ATMax-200 Protocol Analyzer can simulate both network and user signaling. An unlimited number of users can be simulated to test ATM switches. Alternatively, it can replace an actual switch in UNI stress-testing applications.

According to Tektronix’s Mr. Ehrhardt, there is a trend to high-level applications. “For the protocol simulator, there should be applications which allow whole network elements to be replaced by the simulator for testing purposes,” he explained.

Ease of Use

Given the complicated test situations that can be encountered, it’s only natural to want protocol analyzers to be as easy as possible to use. Part of ease of use is having the required functionality:

Filters to identify data to be captured or analyzed.

Multiple display windows for viewing statistics and captured frames simultaneously.

Full seven-layer decoding.

The capability to tailor the traffic being generated in the simulation mode.

Ease of use also involves having “an intuitive GUI, preferably Windows-based; a lightweight, portable instrument for field use; online help; and a programming interface that allows specific parts of the analyzer to be customized,” noted to Mr. Marschall of Radcom.

A real-time expert mode that determines if there is a problem, such as excessive hops or duplicate addresses, and then alerts the user is featured in the Digitech LAN900 Hand-Held Protocol Analyzer. “This mode compares actual network performance to user-configurable events,” Mr. Ushler said.

“A protocol analyzer also should be configurable and extendable to support current and future types of interfaces and protocols,” noted Mr. Ehrhardt of Tektronix. “A large selection of ready-to-use protocol emulations really is desirable.” The Tektronix K1205 Signaling Protocol Analyzer contains more than 100 communications protocols as well as approximately 150 country- and vendor-specific protocols.

References

1. Green, H., “All Roads Lead To The Web,” Business Week, Nov. 24, 1997, pp. 150-151.

2. Brull, S., Gross, N., and Yang, C., “Cell Phones: Europe Made the Right Call,”

Business Week

, Sept. 7, 1998, pp. 107-110.

3. Himelstein, L., et al, “Yahoo!,” Business Week, Sept. 7, 1998, pp. 67-76.

4. Naganawa, S. and Zuo, R., “A Message Handling System for B-ISDN User-Network Interface Signaling Test Software,” Hewlett-Packard Journal, April 1997, pp. 51-58.

Multi-Interface Analyzer

Is Automatically Configured

Up to 16 physical interfaces and 32 channels can be monitored simultaneously by the 11.3″ × 13.5″ × 7.5″ VME-based K1205 Signaling Protocol Analyzer. Features include four measurement slots for test modules, analysis of the different layers of approximately 250 protocols, simulation modes, and automatic configuration of the instrument without manual pre-test setup. The built-in LAN port provides TCP/IP for remote control and network applications. A PS-2-compatible keyboard, a trackball, and a color screen are standard. Tektronix, (800) 426-2200, (code 1090).

Protocol Analyzer Emulates

End-To-End ISDN Connection

The TAS 2502A is an ISDN central office emulator and protocol analyzer. It contains two ISDN-BRI (2B+D) interfaces with U (2B1Q) and S/T (ASI bipolar) access to each. It captures and stores protocol traces for layers 1, 2, and 3 and provides high-level message translation. It also simulates X.25 Packet Mode Data calls, applies in-band tones to voice calls, and routes speech and Circuit Mode Data connections on either B channel. Real-time, in-line, U-interface protocol analysis is optional. Telecom Analysis Systems, (908) 544-8700.

PC-Based Protocol Analyzer

Supports Bi-Phase Encoding

FM0-encoded HDLC packets at rates up to 230,400 b/s can be captured and deciphered by the Model 905 PC Notebook Comscope Protocol Analyzer. Comscope connects to a PC’s parallel port and is configured as a DTE or DCE through software. RS-232, RS-422, RS-485, and V.35 hardware interfaces are built-in. Operating modes are ASYNC; SYNC including SNA/SDLC, X.25/HDLC, and Bisync; and UNKNOWN which accepts and decodes any serial data. Telebyte Technology, (800) 835-3298.

Analysis Software Determines

Top Talkers and Listeners

A new version of ATM Consultant Software measures and analyzes ATM signaling and LAN emulation performance. Determination of top talkers and top listeners, Q.SAAL and ILMI error identification, and protocol verification are features that address ATM signaling applications. LAN emulation analysis includes evaluating LE_Join and LE_Arp response times, tracking LAN Emulation Client control and data connections, and ascertaining complete ATM station address binding. ATM Consultant operates on the capture buffer data and runs on Prism Series and RC-200-C Analyzers. Radcom, (201) 529-2020.

Expert Analyzer Recommends

Solutions to Network Problems

The LAN900 Hand-Held Protocol Analyzer is available for token ring 4- or 16-Mb/s and 10-MHz or 100-MHz Ethernet networks. It provides real-time 100% capture of frames, statistics, and time stamps to RAM and hard disk. An expert mode recognizes and suggests solutions to problems such as excessive hops and packet timing. Features include filtering at any or every layer, byte, or bit; seven-layer protocol decoding; and simulation of traffic with varying packet sizes. Remote control and graphing software are options. Digitech, (800) 821-2265.

Multi-Port Analyzer

Is VME-Based

Up to 28 line interface ports in an integral 22-slot VME chassis are provided by the interWATCH™ 96000 rack-mount ATM/LAN/WAN Protocol Analyzer. Multiple, remote UNIX workstations can independently launch and run test applications on the analyzer. In its intended network verification lab environment, increased port density improves simultaneous, correlated, and automated traffic generation and protocol analysis. Optional software tests PNNI conformance, UNI signaling performance, and ATM-to-LAN/WAN interworking capabilities. GN Nettest, (905) 479-8090.

Glossary of Terms

2B+D 2 Bearer Channels @ 64 kb/s + 1 Data Signaling Channel @ 16 kb/s

2B1Q Two-Binary, One-Quaternary (ISDN-BRI four voltage level bit stream)

ATM Asynchronous Transfer Mode

BER Bit Error Rate

B-ISDN Broadband Integrated Services Digital Network

BISYNC BISYNChronous Transmission

DCE Data Communications Equipment

DTE Data Terminal Equipment

FM0 Self-Clocking Data Encoding Scheme (for HDLC Packets)

GSM Global System for Mobile Communications

GUI Graphical User Interface

HDLC High-Level Data Link Control

ILMI Interim Link Management Interface

ISDN-BRI Integrated Services Digital Network-Basic Rate Interface (2B+D)

LAN Local Area Network

LE_Join Request to Join an Emulated LAN

LE-ARP LAN Emulation Address Resolution Protocol (request for address)

LIM Line Interface Module

MDL Message Descriptive Language

NIC Network Interface Card

PNNI Private Network-Node Interface

Q.SAAL ATM Signaling standard

QoS Quality of Service

S/T Either S or T designates BRI via two twisted pairs (1 km)

SAAL Signaling ATM Adaptation Layer

SAR Segmentation and Reassembly

SNA/SDLC System Network Architecture/Synchronous Data Link Control

SONET Synchronous Optical NETwork

TCP/IP Transmission-Control Protocol/Internet Protocol

U Designates ISDN-BRI via one twisted pair (5 to 0 km)

UNI User Network Interface

UPC Usage Parameter Control

WAN Wide Area Network

 

Copyright 1998 Nelson Publishing Inc.

November 1998