Freeze one call, pilot, DID and observed destination
Record UTC and local time, pilot, affected DID, caller, expected and actual binding or SureCall destination, proxy, selection method, channel state, provider-visible binding state, response code, CDR filters, edge result and PBX match. Redact credentials and personal data.
Classify the first divergence: the binding inventory differed; the expected binding was not healthy; Round Robin or Lowest Available selected another active binding; the PBX returned a documented SureCall trigger; all bindings were down and unavailable forwarding acted; no request reached the edge; or the PBX selected another local route.
Confirm pilot, DID and binding inventory before tracing
The pilot identifies the trunk and provider CDR context; it is not every DID. Each IP-address and port pair is a binding. ThinkTel documents up to eight IP addresses per trunk, and the same address can be used by separate trunks only when their SIP service ports are unique.
Compare the current uControl order, pilot, DID ownership, binding IP and port, proxy, PBX type, per-binding maximum channels and SureCall scope. Do not infer the active inventory from a PBX template or an old implementation worksheet.
Correlate OPTIONS health with the selection method
ThinkTel documents OPTIONS-driven health and says an unresponsive binding is disabled for new INVITEs until it responds again. Round Robin alternates calls among configured bindings. Lowest Available prefers earlier bindings and advances when they are full or unavailable. Those mechanisms are separate from a PBX route and from telephone-number forwarding.
Preserve each OPTIONS exchange, provider state, selection method, binding order, channel observations and affected call. A secondary-binding INVITE proves selection for that call, not the reason the primary was unavailable or full.
Distinguish SureCall response triggers from all-down forwarding
ThinkTel publishes specific SIP response codes that can trigger unavailable forwarding without requiring a binding to be down. It also documents SureCall when all configured bindings are unresponsive. Record the exact response and the scope of the configured forward before assigning the cause.
Do not replace a meaningful PBX response with a generic error just to force forwarding. A call answered at the SureCall destination proves that one forwarded leg answered; it does not prove another binding was attempted, primary-path restoration or media success on the SIP trunk.
Match the provider record to edge and PBX processing
Use the selected time zone, pilot or DID and date range to obtain the relevant ThinkTel CDR. Treat its billing number, source, destination, channel count and line type as provider-side correlation, not edge or media proof. Match the provider attempt to an authorized capture at the expected binding.
If the request arrived, preserve source, Request-URI, asserted identity, Via, Contact, digest exchange, SDP and response sequence. Follow the effective PJSIP identify, endpoint, transport, context, digit normalization and first loaded route. Correct only the first demonstrated divergence.
Retest ordinary routing and only an approved failover condition
After an authorized correction, retest the ordinary DID path and one unaffected control while recording provider selection, edge receipt, PBX match, answer and media separately. Exercise a disabled binding, response-code trigger or SureCall destination only through an owner- and ThinkTel-approved plan; restore normal state and verify restoration with the same evidence chain.
Keep emergency testing outside this regression. ThinkTel requires advance coordination and confirmation for a live 911 test. No ThinkTel account, binding, CDR, PBX, packet, call, SureCall event, emergency result or support response was inspected or tested for this diagnostic.
Sources & applicability
Primary references for the technical details above. Operational examples and planning checklists are VoIP.info editorial guidance.
- ThinkTel SIP trunk service overview ↗
- ThinkTel SIP authentication ↗
- ThinkTel SIP failover ↗
- ThinkTel SureCall response-code triggers ↗
- ThinkTel SIP trunk IP-binding limit ↗
- ThinkTel CDR download ↗
- ThinkTel 911 testing procedure ↗
Examples require adaptation to your topology. No live PBX or hardware testing is claimed.