Cutting Through Opinions
EVERYONE'S FIRST QUESTION: Is it Network - Application - Server - Desktop - WAN? Trace entire Interpath - Diagram Application Flow - then create Test Plan.
Troubleshooting successfully & consistently - requires understanding completely Network & Application Flow from end-to-end.
- Application - Requirements - DLL/EXE locations - Local v. Remote protocols
- Database (s) - Version - Configuration . Server's Environment - UNIX <-> Windows Issues - Configuration & Utilization - Directory Services
- Desktop Environment - DNS - Build - DFS - Scripts
- Infrastructure - Routers . Switchport Statistics - CRC - Drops - Buffer Overruns - Errors . Optimizers . Load Balancers . Firewalls . Proxies
- End-User Training - Use application same way?
Application Flow = path from User -> Through Everything else -> back to User = The Interpath.
One person or team seldom knows entire Interpath for a given Application. Network & Application Performance Analyst (NAPA) must interview relevant Subject Matter Experts (SME) - Network Teams - OS Teams, etc..
Interpath includes all component -- yet:
- Database Administrator doesn't think about Network.
- Network Engineer knows little about Application & Database Servers.
- Server Team is unaware of Switch configurations,
- And so on.
- Complete diagram is very rare.
- NAPA must create that diagram.
Create detailed diagram to map Interpath. This becomes Application Flow Diagram. Application Flow Diagram includes:
- TCP/UDP Ports involved
- IP addresses of components
- Directional indicators showing interaction flow of specific application transactions
Use Application Flow Diagram to identify SPAN / mirror / tap locations. Place Sniffer / Ethereal / WireShark -- where traffic flow includes Workstation - First Tier Servers - Database Servers.
Capture Filters are critical. Filter as little as possible. You can't go back to see later what you didn't capture before. Gather Trace Files from workstation-side & server-side simultaneously. Filter for individual pre-determined Transactions.
Filter completed trace creatively - not during capture process. Rely on Application Flow Diagram.
Always remember the Interpath - careful planned appropriate analysis - will provide resolution - consistently.
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