Add up signalling hops, processing time and radio setup to get post-dial delay and check it against the ITU target.
Every proxy, border controller and application server in the path adds both propagation time and its own processing time, and both scale with the hop count. Radio bearer establishment and name resolution are one-off costs added on top. Users abandon calls that take more than a couple of seconds to ring, and each extra SBC or application server inserted 'just for policy' quietly spends hundreds of milliseconds of that budget.
Call Setup Delay
post-dial delay = hops × per-hop RTT + hops × per-element processing + radio bearer setup + DNS/ENUM resolution.
post-dial delay = hops × per-hop RTT + hops × per-element processing + radio bearer setup + DNS/ENUM resolution. Every proxy, border controller and application server in the path adds both propagation time and its own processing time, and both scale with the hop count. Radio bearer establishment and name resolution are one-off costs added on top.
Users abandon calls that take more than a couple of seconds to ring, and each extra SBC or application server inserted 'just for policy' quietly spends hundreds of milliseconds of that budget.
This calculator takes 6 inputs: Signalling hops end to end, Round-trip latency per hop, Processing time per network element, Radio bearer setup time, DNS/ENUM resolution, Target post-dial delay. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.