---
title: "Quality Routing & Carrier SLA Engine"
description: "Documentation for Quality Routing"
---

## Table of Contents
1. [Overview & Architecture](#1-overview--architecture)
2. [Business & Operational Significance](#2-business--operational-significance)
3. [🎯 User Roles & Key Capabilities](#3--user-roles--key-capabilities)
4. [Visual Interface & Form Layout](#4-visual-interface--form-layout)
5. [Field & Configuration Reference](#5-field--configuration-reference)
6. [Real-Time Telephony Quality Metrics (ASR, ACD, MOS)](#6-real-time-telephony-quality-metrics-asr-acd-mos)
7. [Automated Degradation & Autonomous Rerouting](#7-automated-degradation--autonomous-rerouting)
8. [Security Best Practices & Operational Hardening](#8-security-best-practices--operational-hardening)
9. [Troubleshooting & Verification](#9-troubleshooting--verification)
10. [Glossary](#10-glossary)

---

## 1. Overview & Architecture

In **Ring2All SBC**, the **Quality Routing** module (`public.carrier_quality_policies` and real-time CDR aggregation) introduces intelligent, automated quality-of-service closed-loop control to carrier routing decisions. 

While traditional Least Cost Routing (LCR) selects routes based solely on static tariff rates, Ring2All SBC continuously aggregates live telephony telemetry—including **Answer-Seizure Ratio (ASR)**, **Average Call Duration (ACD)**, and RTPEngine **Mean Opinion Score (MOS)**. If an upstream carrier experiences fiber cuts, transcoding latency, or packet loss degradation below defined SLA thresholds, the system autonomously penalizes the route and shifts traffic to higher-performing secondary routes.

```
                  ┌─────────────────────────────────────────┐
                  │          Inbound Call Traffic           │
                  │    (Continuous Real-Time Telemetry)     │
                  └────────────────────┬────────────────────┘
                                       │
                                       ▼
                  ┌─────────────────────────────────────────┐
                  │    RTPEngine & Kamailio CDR Engine      │
                  │  • Packet Loss • Jitter • Round-Trip    │
                  │  • SIP 200 OK vs 5xx Failure Codes      │
                  └────────────────────┬────────────────────┘
                                       │
                                       ▼
                  ┌─────────────────────────────────────────┐
                  │   Quality Routing Engine (Every 15m)    │
                  │   Sliding Evaluation Window Calculation │
                  └────────────────────┬────────────────────┘
                                       │
                Quality Score Verification vs Configured Policy
                                       │
           ┌───────────────────────────┴───────────────────────────┐
           │ ASR >= 40% & MOS >= 4.0                               │ ASR < 40% OR Packet Loss > 5%
           ▼                                                       ▼
┌─────────────────────────────┐                         ┌─────────────────────────────┐
│       Optimal Status        │                         │      Degraded Status        │
│  • Keep Carrier in Pool     │                         │  • Trigger NOC Alert        │
│  • Normal Weight Routing    │                         │  • Autonomous Reroute       │
│  • Record SLA Compliance    │                         │  • Auto-Recovery Cooldown   │
└─────────────────────────────┘                         └─────────────────────────────┘
```

---

## 2. Business & Operational Significance

* **Guaranteed Call Completion**: Protects contact centers, enterprise sales floors, and emergency lines from silent call drops, fast-busy tones, and robotic audio caused by carrier packet degradation.
* **Autonomous SLA Enforcement**: Automatically detects carrier route degradation without requiring human NOC engineers to monitor dashboards 24/7 or manually modify routing tables.
* **Balanced Quality vs. Cost**: Ensures telecom operators never sacrifice audio fidelity for pennies of margin; when low-cost routes degrade, traffic seamlessly ascends to premium carriers until quality restores.
* **Objective Vendor Scorecards**: Generates irrefutable statistical data for carrier SLA dispute resolution, vendor billing credit negotiations, and quarterly vendor reviews.

---

## 3. 🎯 User Roles & Key Capabilities

| Role | Primary Use Case | Key Capabilities |
| :--- | :--- | :--- |
| **SBC Administrator** | Carrier Policy Configuration | Establish global quality thresholds; define evaluation time windows; configure automatic failover actions; set cooldown recovery timers. |
| **NOC Voice Engineer** | Live Quality Inspection | Monitor real-time ASR, ACD, MOS, and jitter metrics; manually trigger immediate route re-evaluation; inspect degraded gateways. |
| **Telecom Procurement Lead** | Carrier Performance Auditing | Review historical carrier quality metrics across 15m, 1h, 24h, and 7d windows to assess vendor SLA compliance. |

---

## 4. Visual Interface & Form Layout

### Quality Routing Live Telemetry Dashboard
The dashboard displays global telephony KPIs (Global ASR, Global ACD, Active Gateways, Degraded Count) and an interactive data grid tracking each wholesale carrier's real-time quality scores.

![Quality Routing Live Telemetry](/screenshots/sbc/routing/quality/quality-routing-list.png)

### Carrier Health & Quality Policy Form
The policy view allows administrators to configure automated threshold metrics, sampling parameters, and autonomous failover actions.

![Carrier Health & Quality Policy Form](/screenshots/sbc/routing/quality/quality-routing-form.png)

---

## 5. Field & Configuration Reference

### Section 1: Quality Thresholds & Sampling

| Field | Type | Options / Constraints | Description |
| :--- | :--- | :--- | :--- |
| **Policy Name \*** | Text | Max 100 characters | Name of the active SLA policy (e.g., `Standard Carrier Quality SLA`). |
| **Enable Real-Time Health Engine** | Toggle | Boolean (`Yes` / `No`) | Activates continuous background evaluation of carrier performance metrics. |
| **Minimum ASR (%) \*** | Number | `1.0` to `100.0` (Default `40.0%`) | Answer-Seizure Ratio floor. Carriers dropping below this percentage are flagged as degraded. |
| **Minimum ACD (Seconds) \*** | Number | `1` to `600` (Default `30s`) | Average Call Duration floor. Drastic drops in ACD typically indicate dead air or immediate customer hang-ups. |
| **Minimum Call Sample Size \*** | Number | `5` to `500` (Default `10`) | Minimum call attempts required within the time window before taking automated failover actions. |
| **Evaluation Window \*** | Dropdown | `5m`, `15m`, `30m`, `1h` | The rolling time window over which CDR metrics are computed. |

### Section 2: Automated Failover & Recovery

| Field | Type | Options / Constraints | Description |
| :--- | :--- | :--- | :--- |
| **Automated Action on Degradation \*** | Dropdown | `alert_only`, `alert_and_reroute`, `disable_gateway` | Action triggered when a carrier breaches quality thresholds. |
| **Auto-Recovery Cooldown \*** | Number | `5` to `120` minutes (Default `15m`) | Time period the SBC waits before testing a degraded carrier with probe traffic to verify recovery. |
| **Admin Notifications** | Toggle | Boolean (`Yes` / `No`) | Dispatches instant alerts via email and the platform notification center upon route degradation. |

---

## 6. Real-Time Telephony Quality Metrics (ASR, ACD, MOS)

Ring2All SBC calculates telephony health based on industry standards:

### 1. Answer-Seizure Ratio (ASR)
$$\text{ASR} = \left( \frac{\text{Answered Calls (SIP 200 OK)}}{\text{Total Call Attempts}} \right) \times 100$$
- **Optimal**: $ASR \ge 65\%$
- **Acceptable**: $40\% \le ASR < 65\%$
- **Degraded / Faulty**: $ASR < 40\%$ (indicates carrier network congestion or signaling disconnects).

### 2. Average Call Duration (ACD)
$$\text{ACD} = \frac{\sum \text{Duration of Answered Calls}}{\text{Count of Answered Calls}}$$
- **Short ACD (< 15s)** often indicates audio path failure (one-way audio, dead air, or ring-no-answer loops).

### 3. Mean Opinion Score (MOS)
Calculated via RTPEngine from real-time RTP jitter buffer statistics and packet loss telemetry:
- **4.3 - 4.5**: Pristine, studio-grade audio (G.711 / G.722 HD).
- **4.0 - 4.2**: Standard toll-quality telephony.
- **< 3.5**: Noticeable clipping, robotic voice, or significant delay.

---

## 7. Automated Degradation & Autonomous Rerouting

When **Automated Action on Degradation** is set to `alert_and_reroute`:

1. **Detection**:
   The background worker detects that Carrier X fell to $28\%$ ASR across 50 call attempts over the last 15 minutes.
2. **Autonomous Demotion**:
   The engine dynamically lowers the carrier's priority in Kamailio's `drouting` tables via RPC:
   ```bash
   kamcmd drouting.carrierDemote carrier_id=1 reason="ASR fell below 40% threshold"
   ```
3. **Rerouting**:
   Subsequent calls automatically bypass Carrier X and route through Carrier Y.
4. **Probing & Restoration**:
   After the **Auto-Recovery Cooldown** expires (e.g., 15 minutes), the SBC allows a low-volume canary sample of calls (5%) through Carrier X. If the sample demonstrates healthy ASR ($> 50\%$), Carrier X is fully restored.

---

## 8. Security Best Practices & Operational Hardening

* **Prevent Flapping with Sample Size Guards**: Never set **Minimum Call Sample Size** below 10. In low-traffic hours, 2 consecutive unanswered calls could trigger false-positive degradation alerts.
* **Tune for Destination Types**: DIDs terminating to call center IVRs naturally have higher ASR and longer ACD than outbound predictive dialer campaigns. Calibrate policies appropriately.
* **Integrate with Notification Webhooks**: Configure administrative email alerts to notify the upstream carrier's NOC immediately when degradation is detected to accelerate vendor ticket resolution.

---

## 9. Troubleshooting & Verification

| Symptom / Issue | Potential Root Cause | Recommended Verification & Resolution |
| :--- | :--- | :--- |
| **Dashboard displays "No carrier metrics recorded"** | No calls traversed the SBC in the selected time window, or CDR table timestamps are out of sync. | Verify system clock synchronization via NTP (`chronyc tracking`) and ensure CDR accounting is active in **Reports > Call Detail Records**. |
| **Carrier incorrectly marked Degraded during off-peak hours** | Sample size too small ($N < 5$). | Increase the **Minimum Call Sample Size** in the policy form to at least 25 attempts. |
| **Autonomous reroute did not occur despite low ASR** | Policy action set to `alert_only`. | Change **Automated Action on Degradation** to `alert_and_reroute` and save changes. |

---

## 10. Glossary

* **ASR (Answer-Seizure Ratio)**: Primary telecom metric measuring the percentage of initiated calls successfully answered by the callee.
* **ACD (Average Call Duration)**: The average length of answered telephone conversations across a given time frame.
* **MOS (Mean Opinion Score)**: Subjective or algorithmically derived measurement of the perceived audio quality of a voice call (ranging from 1.0 to 5.0).
* **Flapping**: Rapid, repeated state transitions between healthy and degraded caused by overly sensitive monitoring thresholds.