SIP 408 timeouts breaking predictive routing warm-up phase during A/B test

I’m currently running a split test on the new predictive routing campaign, splitting the list 50/50 between our standard SIP trunk and a secondary provider. The ML model performance is taking a serious hit on the secondary side, and agent scoring isn’t updating properly since the dialer keeps dropping calls before the predictive window even closes.

Diving into the SIP trace, I’m seeing a steady stream of 408 Request Timeout and 487 Request Terminated responses right around the 3-second mark. Console logs are pointing to the outbound campaign flow timing out at the Set Outbound Contact element. We’ve got the dialing strategy locked to predictive with a 75% agent utilization target. The warm-up period really needs at least 150 answered calls to stabilize the regression model, but the trunk is choking after roughly 40.

I checked the /api/v2/telephony/servers/providers endpoint, and latency metrics look totally fine until concurrency hits 120. After that, SIP INVITE latency jumps to 1.8 seconds. Predictive routing really expects sub-200ms handoffs for optimal routing optimization, so it’s penalizing agents for slow connect even though the delay is happening at the SIP layer before the call even bridges.

Over on the A/B test dashboard, I’m seeing a 42% drop in predicted answer rate on the secondary trunk. The confusion matrix for the ML outcome prediction is basically random noise at this point. I’ve retrained the model twice today with fresh call disposition data, but the underlying SIP jitter is just poisoning the training set. The flow isn’t doing much to compensate, honestly.

{“timestamp”: “2024-05-12T08:14:22.000Z”, “sip_method”: “INVITE”, “status_code”: 408, “reason”: “Request Timeout”, “call_leg”: “outbound_b”, “flow_step”: “set_outbound_contact”}

As a quick workaround, I adjusted the SIP keepalive interval to 15 seconds and bumped the flow timeout to 6000ms, but I’m still seeing the same 408 cascade. The predictive routing engine keeps flagging the campaign as degraded in the admin console. Quick question: is this a known limitation with high-concurrency predictive dialing over shared SIP trunks, or does the outbound flow need a specific retry logic configured? Also, has anyone else seen agent scoring get thrown off by SIP-layer delays like this?

I’m looking at the raw RTP stats now, and the jitter buffer is maxing out at 80ms. If anyone’s running similar predictive routing setups or has a workaround for the training data poisoning, I’d love to hear how you’re handling it!

Cause: The secondary trunk is choking. WEM’s forecast is stale, so the predictive dialer’s over-dialing ratio is too aggressive for the split volume.

Solution: Check if available agents are dropping below the threshold with this OData query:

curl -X GET "https://api.mynice.com/api/v2/odata/WemIntervals?$filter=CampaignId eq 'your-campaign-id' and IntervalStart gt now()&$select=ForecastedVolume,AvailableAgents" -H "Authorization: Bearer <token>"

Is the error coming from your .NET integration script?
Docs say: “Timeouts during warm-up indicate a mismatch in async update handling.”
Why does not work?
You need check HttpClient timeout. It is often too low for secondary trunks.
Don’t use default. Set in handler:
handler.Timeout = TimeSpan.FromSeconds(5);

The 408s happen because the SIP stack drops the handshake before the predictive window even opens. It’s a classic trunk mismatch, and it’s been wrecking my dashboards for years. When calls drop that fast, real-time transcription never logs the first exchange, which tanks your AI ROI and breaks knowledge surfacing for Agent Assist. Don’t leave the invite timeout at default during an A/B split. Bump invite_timeout to 4500ms in the campaign config. Grab the config screenshot below. Warm-up phase stabilizes right away, and your sentiment tracking and knowledge suggestions finally stop ghosting you.