Application Performance and Network Problems

Terry Slattery
Principal Architect

I’ve started blogging for Opnet at, and the first posts are describing what happens to applications when faced with any of several types of network problems. I’ve previously written about packet loss and how it impacts TCP performance. Most applications are built to use TCP for communications, so packet loss directly affects them. However, there are other factors too, which I begin covering with an article “The Impact of Network Problems on Application Performance.” This is the first in a series of articles that discuss Application Performance Management (APM).

APM is really neat technology that, when properly installed and configured, looks at all the communications between systems that are used to implement an application. Many applications these days are multi-tiered – that is they rely on multiple servers. A pair of load balancers running in High Availability (HA) mode may front-end multiple application servers. The application servers in turn connect to middleware servers, which rely on one or more back-end database servers. In addition, you’ll often find DNS and DHCP in the mix.

When a customer calls, complaining about a slow application, it is often easy for the application support staff to place the blame on the network. After all, the servers are frequently running at acceptable utilization levels and they can’t find anything wrong with their operation. So the network team gets to play the game of Mean Time to Convince.

APM helps both the network and application team determine whether the slow application is due to the network or whether it is due to interactions between the different application tiers. It may also identify a bad database query that causes the DB server to take a long time to return results to the middleware server.

APM products aren’t cheap, so it may take a bit of convincing to get the CIO to buy into it. It is best to have a nagging problem that has gone unsolved for a long time and arrange an evaluation around finding a solution to it. You should expect to take a while to properly design and setup a good evaluation. For a three tiered application that’s not too complex, might take a week or two of staff time (that’s the total effort, not calendar time). Get buy-in from the CIO to set acceptance criteria prior to the evaluation if you want to obtain the product if the evaluation is successful.

My customers who use it have found that it significantly reduces the amount of effort that is required to pinpoint the source of an application performance problem.


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Nick Kelly

Cybersecurity Engineer, Cisco

Nick has over 20 years of experience in Security Operations and Security Sales. He is an avid student of cybersecurity and regularly engages with the Infosec community at events like BSides, RVASec, Derbycon and more. The son of an FBI forensics director, Nick holds a B.S. in Criminal Justice and is one of Cisco’s Fire Jumper Elite members. When he’s not working, he writes cyberpunk and punches aliens on his Playstation.


Virgilio “BONG” dela Cruz Jr.

CCDP, CCNA V, CCNP, Cisco IPS Express Security for AM/EE
Field Solutions Architect, Tech Data

Virgilio “Bong” has sixteen years of professional experience in IT industry from academe, technical and customer support, pre-sales, post sales, project management, training and enablement. He has worked in Cisco Technical Assistance Center (TAC) as a member of the WAN and LAN Switching team. Bong now works for Tech Data as the Field Solutions Architect with a focus on Cisco Security and holds a few Cisco certifications including Fire Jumper Elite.


John Cavanaugh

CCIE #1066, CCDE #20070002, CCAr
Chief Technology Officer, Practice Lead Security Services, NetCraftsmen

John is our CTO and the practice lead for a talented team of consultants focused on designing and delivering scalable and secure infrastructure solutions to customers across multiple industry verticals and technologies. Previously he has held several positions including Executive Director/Chief Architect for Global Network Services at JPMorgan Chase. In that capacity, he led a team managing network architecture and services.  Prior to his role at JPMorgan Chase, John was a Distinguished Engineer at Cisco working across a number of verticals including Higher Education, Finance, Retail, Government, and Health Care.

He is an expert in working with groups to identify business needs, and align technology strategies to enable business strategies, building in agility and scalability to allow for future changes. John is experienced in the architecture and design of highly available, secure, network infrastructure and data centers, and has worked on projects worldwide. He has worked in both the business and regulatory environments for the design and deployment of complex IT infrastructures.