SIP 487 Request Terminated is the final response to an INVITE that was cancelled before anyone answered. It usually means the caller hung up while the phone was still ringing, or a dialer or PBX stopped the attempt after its ring timeout. A 487 is normal in small numbers; a high share points to short timeouts, slow call setup or calls racing on several routes.
What does SIP 487 Request Terminated mean?
RFC 3261 defines 487 as "the request was terminated by a BYE or CANCEL request". In practice it almost always follows a CANCEL. When the calling side sends CANCEL for a pending INVITE, the called side answers the CANCEL with 200 OK and then closes the INVITE with 487. The caller acknowledges with ACK and the attempt ends. No audio was connected and the call is not billed.
What does the 487 call flow look like?
- The caller sends INVITE.
- The far end replies 100 Trying, then 180 Ringing or 183 Session Progress.
- Before any 200 OK, the caller sends CANCEL.
- The far end answers the CANCEL with 200 OK.
- The far end sends 487 Request Terminated for the INVITE.
- The caller sends ACK for the 487.
If a 200 OK for the INVITE crosses the CANCEL on the wire, the call is answered anyway and must be ended with BYE. That race is rare but explains occasional very short answered calls.
What causes SIP 487 errors?
| Cause | What you see |
|---|---|
| Caller hung up during ringing | Random 487s across destinations, normal for manual calling |
| Dialer ring timeout too short | Many 487s with ring times clustered at the same value (for example 15 or 20 seconds) |
| High post-dial delay | Callers give up before the far end rings, often on long international chains |
| Parallel forking | When one branch answers, the proxy cancels the others, which return 487 |
| Failover timers | Your switch cancels a slow route to try the next one |
| Agent not available | A predictive dialer cancels calls it cannot connect to an agent |
Is a high 487 rate a route problem?
Not always. A 487 is created by the calling side, so it tells you more about your own settings than about the supplier. Still, routes can cause it indirectly. If post-dial delay is high, callers and dialers cancel before the phone rings. If a route answers slowly at signalling level, failover timers fire and cancel it. Compare the 487 share and PDD between two routes on the same traffic: if one route has much higher PDD and more 487s, the route is the issue.
For dialers, check the ring timeout first. A timeout under about 20 seconds cuts off people who would have answered, which lowers ASR and inflates 487s. Our guide on dialer traffic and VoIP routes explains what suppliers expect from dialer campaigns.
How to reduce SIP 487 responses
- Lengthen ring timeouts to match how long people take to answer in each country.
- Measure PDD per route and move traffic away from routes with slow setup (see ASR, ACD and PDD).
- Tune failover timers so a route is not cancelled while it is still legitimately setting up the call.
- Tune dialer pacing so it does not launch more calls than agents can take, which also limits abandoned calls.
- Exclude 487 from route quality alerts, or track it separately, so you do not blame a supplier for cancellations you made.
How 487 relates to other codes
In CDRs, a 487 is often labelled as an originator cancel, and the Q.850 cause code recorded next to it depends on the switch, so read both fields together. Do not confuse it with 408, 480 and 486, which come from the far side, or with 503, which signals a capacity problem. The full table is on our SIP error codes page.
Routes with fast, clean call setup
If slow call setup on a supplier is pushing your 487s up, VoIPMatcher can source a VoIP termination route with lower PDD from its carriers and manage it for you. Request a VoIP route with your destinations and traffic type.
Frequently asked questions
Is SIP 487 an error?
Not in the usual sense. A 487 confirms that a ringing call was cancelled by the calling side, which is a normal event when people hang up before an answer. It only becomes a problem when the share is unusually high, which suggests short ring timeouts, slow call setup on a route or aggressive failover timers.
Who sends the SIP 487 response?
The called side, meaning the user agent or server that received the INVITE, sends 487 after it receives a CANCEL for that INVITE. The CANCEL itself comes from the calling side, which can be the phone, the PBX, a dialer or an intermediate proxy that is cancelling forked branches.
Are SIP 487 calls billed?
No. A 487 means the call was never answered, so no conversation time exists and standard per-minute wholesale billing does not charge for it. If you see charges for calls that ended in 487, compare your CDRs with the supplier's, because it may point to a billing error or false answer supervision.
What is the difference between SIP 487 and SIP 486?
486 Busy Here comes from the far end and means the called user is busy and cannot take the call. 487 Request Terminated means the calling side gave up and cancelled the attempt before answer. 486 reflects the called person, while 487 reflects the caller, the dialer or a routing timer.
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