Give every call a defined routing policy.
Align destination selection with cost, quality and the operating requirements of your voice network.
- 01INGRESSTrunk admission
- 02NORMALIZATIONNumber & identity rules
- 03ROUTE POLICYLCR + quality review
- 04EGRESSSelected carrier trunk
- 05CALL RECORDSDuration & outcome
- 06RATING REVIEWDeck & billing records
Balance route economics with call behavior.
Make the selection rules explicit
Least-cost routing compares eligible routes using their commercial rates. Quality-based decisions also consider the performance objective for a traffic group. Prefix matching, route priority and access restrictions determine which paths are eligible before a call is attempted.
Keep rate changes and policy changes traceable. A route that is economical for one destination may not be the right choice for another. Define destination groups and review them against actual traffic rather than relying only on a blended network average.
Failover needs a controlled retry policy
A second attempt can help when a path is unavailable, but indiscriminate retrying can create duplicate attempts, delays and a traffic burst. Agree which outcomes qualify for another route, the maximum attempt count and how the policy interacts with caller cancellation.
Test route withdrawal and restoration with representative calls. Review the resulting call records so operations can distinguish the original attempt from later attempts. Confirm the controls available to your account and the change process used to operate them.
Where it fits in your network
- 01Customer SBCCall initiation
INVITE - 02VirPhone EdgeIngress validation
100 TRYING - 03Routing EngineRoute selection
180 RINGING - 04Carrier RouteCall established
200 OK - 05Destination PSTNTwo-way media
RTP
Plan the connection around your traffic
Cost and quality
Compare low-cost routes against the quality needed for the traffic. Define how ASR, ACD and PDD will be evaluated.
Failure behavior
Specify which responses advance to an alternate route and when the call should stop. Unbounded retries can create excess traffic and delay.
Change control
Record rate and routing changes. Evaluate destination performance before expanding a policy across the traffic base.
Agree the details before production
| Parameter | Planning detail |
|---|---|
| Inputs | Destination prefixes, rates and quality objectives. |
| Policy | Confirm supported LCR, priority and quality options. |
| Failover | Agree response-code and timeout treatment. |
| Validation | Compare controlled traffic before and after changes. |
What to review with your team
| Review area | What to establish |
|---|---|
| Eligibility | Prefixes, destination restrictions and route groups. |
| Selection | Commercial priority and quality objectives. |
| Recovery | Retry conditions, attempt limits and restoration tests. |
Before the next step
Does the cheapest rate always produce the lowest cost?
Not necessarily. Consider call completion, billing increments and the operational effect of retries alongside the nominal per-minute rate.
What does the diagram represent?
The diagram explains the logical call path: Customer SBC, VirPhone Edge, Routing Engine, Carrier Route and PSTN. It does not identify physical infrastructure.
Choose routes with a reason you can explain
A route policy is a set of eligibility and selection decisions. Destination restrictions determine which paths may be considered. Commercial rates and quality objectives then influence which eligible path should be preferred. Keep the rules specific enough that an operator can explain why a call used a particular route.
Use destination groups with meaningful traffic characteristics. Combining unrelated traffic into one quality score can hide a local issue or penalize a healthy route. Inspect CDR and quality evidence before changing a policy on the strength of one aggregate percentage.
Control what happens after a failed attempt
Failover is a decision about a particular outcome, not an instruction to retry every call. Review which responses permit another attempt, how many attempts are allowed and what happens if the caller cancels. The resulting records need to distinguish a customer call from the carrier attempts created to deliver it.
Apply the same discipline when a preferred path returns. A restoration test should establish that the intended route becomes eligible again without creating an unexpected shift in traffic or cost. Keep a previous configuration available so a policy change can be reversed through the agreed process.
Separate a policy experiment from production traffic
Evaluate a change against a stable sample and a defined objective. A change in destination mix can alter the result even if the route itself has not changed. Record the policy version, time window and call set used for comparison.
Commercial updates and quality interventions may need different approvals. Link the rate deck, the route configuration and the acceptance record so operations can reconstruct the decision. For the larger switching context, review Class 4 carrier switching.
Investigate a destination-specific change
Suppose one destination group develops a longer setup delay while other groups remain stable. Compare equivalent traffic and time windows, inspect call outcomes and identify the route actually selected. A network-wide average may conceal the affected group and lead to an unnecessarily broad change.
If an alternate allocation is part of the approved design, evaluate it with a controlled sample and retain the before-and-after evidence. Consider cost, call completion and setup behavior together. Document who approved the change and the conditions for reviewing it again. This hypothetical case illustrates policy evaluation; it does not promise automatic failover or any particular route outcome.