The walls between IT groups are crumbling, and network professionals report that responsibility for optimal application performance is shifting to them.

Distributed IP networks and complex real-time applications have forced a change. Now network managers need to be in the know from the start about application performance, helping developers understand what will work on a network, spotting poorly performing applications before users feel the effects and delivering LAN-like performance over the wide area to remote and branch offices.

"There are two kinds of network people in my mind: the ones that are just out of college and have all their certifications; and those that know the company's network, the applications that run on it and how to marry those two together," says Larry McBrayer, network architect for SaraLee Technology Services in Mason, Ohio. "That's the difference between a contracted resource called in to troubleshoot a specific network issue [and] a corporate employee that knows the net, the business' apps and how they should be working together."

McBrayer says his application performance duties expanded when his organization installed Siebel software and couldn't get it working as desired. He used a combination of network tools from companies such as Network General and NetQoS, as well as application and system management products from BMC Software, CA and SolarWinds to better track down application performance problems. Ultimately it took a lot of tuning and tweaking by the network team to help the application team work out the kinks in the Siebel deployment.

"It's very cumbersome to explain Sniffer traces to an application developer," he says.

The more companies explore service-oriented architectures, deploy VoIP or consolidate data centers to serve up applications from a centralized point to remote offices, the more network professionals are going to be called on to improve application performance, experts say.

"An intelligent or application-aware network places new demands on network managers," says George Hamilton, director of enterprise computing and networking at The Yankee Group. "They now have more responsibility for applications than just determining whether the network is the source of the problem. . . . The nature of enterprise applications is such that network managers must be involved in their performance."