The Ups And Downs Of Analyzing Middleware

By Barry Nance  Middleware, by its nature, operates invisibly. This invisibility, along with the difficulty of isolating middleware-related network traffic, discourages close examination of middleware's effect on your network. Out of sight, out of mind--this adage applies in spades to middleware. However, within the framework of a client/ server or Web-based business application system, measuring middleware's network use and observing its network traffic can explain much about an application's behavior. Does the application inexplicably slow at odd times of the day? Does it have a thirst for additional hardware that mere user population growth doesn't justify? Does it fail to scale as you install it at more sites across the e nterprise? Do stray, elusive bugs crash the application, and do you suspect some pathological interaction with the network or with the middleware? If you've answered yes to any of these questions, then read on, because we've got answers for you. Poring Through the Bits We examined the network traffic generated by data-access middleware on a three-segment Ethernet LAN consisting of three Advanced Logic Research Evolution servers running Microsoft Windows NT Server 4.0, 15 PC clients running Windows95, two IBM OS/2 Warp clients, and an Apple Computer Macintosh client. The databases we accessed included Oracle7.3 (SQL*NET traffic), IBM DB2 Universal Database 5.0 (DRDA traffic) and Microsoft SQL Server 6.5 (TDS traffic). Two data-access analyzers let us view network traffic as we worked to isolate, measure and evaluate the middleware events. Running on a Dolch Computer Systems PAC 63C, Network General's Fast Ethernet Sniffer Analyzer 5.02 with Database Module Option for Sybase 5.09 and Database Modu le Option for Oracle 5.02 gave us a packet-by-packet view and a summary view of middleware traffic. Running on one of the NT Server machines, Compuware's EcoSCOPE 3.0 provided us with an application-by-application view as well as a topology map of our network. The pair monitored our network traffic and utilization as our software logged onto the databases, issued SQL statements and retrieved results. Additionally, both EcoSCOPE and Sniffer gathered comprehensive metrics about how client/server applications performed and consumed network resources. The two products discovered, measured and tracked application response times and traffic loads. EcoSCOPE analyzed network traffic at the application level to identify those applications consuming the most bandwidth on each network segment at a given time, while Sniffer decoded and displayed database access activity in terms of request and response packets. Data-access middleware's primary use of the network occurs when applications access data residing on remo te servers. In terms of the OSI Reference Model, this access happens at the application (seventh) layer. An analyzer lets you choose those network applications whose network usage you want to measure (a top-down approach), or it lets you choose packet-filtering criteria that produce the measurements you want (a bottom-up approach). The distinction is subtle but important--with the latter approach, you need to have a somewhat greater technical perspective, or an awareness of the types of packets a data-access protocol uses. We discovered that the top-down approach offered a more global picture of an application's network use. The top-down approach also encouraged us to focus on specific application traffic between particular network nodes. However, troubleshooting network hardware or configuration problems is much easier with the bottom-up approach. If you're accountable only for the database-access aspect of the network, take a top-down approach. On the other hand, responsibility for an entire network sugg ests taking a bottom-up approach to solving problems.

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