Troubleshooting via a maze of network devices

Several years ago, a new category of network equipment for bandwidth optimization emerged. Dubbed "traffic managers" or "traffic shapers," these devices go beyond firewalls by classifying traffic based on information deep within the packet.

Essentially, they are OSI Layer 7 switches with buffering capability for queuing and partitioning. Packeteer was an early leader in this field and continues to hold a significant portion of the market today.

Traffic managers are but one component of today's networks that can make troubleshooting connectivity issues quite complicated. There are routers, switches, firewalls, authentication servers, network access control devices, load balancers, intrusion-prevention systems, virtual private networks -- the list goes on and on. Each system adds another layer to troubleshoot when things don't work as planned.

I recently found myself troubleshooting a situation involving intermittent connectivity to a company's e-mail portal. While ultimately the issue was caused by a traffic manager, I reached that conclusion only after navigating a maze of network devices. While my path to resolution wasn't perfect, the methodology of working with several devices that could be an issue emphasized several critical network lessons.

The problem

Access was intermittent from off-site but worked fine from the site itself to a Web portal for access to e-mail. The problem pointed to a block at the network edge, and that is where I began my investigation.