In this chapter
Find the part that needs attention
A network fault becomes easier to understand when you separate its layers. Start with the symptom, then follow the path that produces it.
Signal is present, data is missing
Look at attachment and authentication, then the data bearer, gateway rules, routes and DNS. A visible radio network and usable Internet access depend on different steps.
Data works, voice will not register
Follow IMS reachability, subscriber identity, authentication and serving function routing. The handset also needs suitable IMS support and configuration for the network.
A call connects with missing audio
Check the media addresses, negotiated codecs, RTP path and relay handling. Signalling and sound can travel through different components, so their faults can have different causes.
A tunnel connects but transfers stall
Check the return route, customer firewall and packet size. Comparing a small request with a larger transfer can help identify an MTU problem along the tunnel path.
A dashboard looks healthy, a user has trouble
Ask what the displayed measurement covers. Machine health, protocol checks and customer actions give different views. I bring those views together to narrow down the fault, then repeat the affected action after the change. A clear explanation helps the next person solve the same problem faster.