diff --git a/system_design.md b/system_design.md new file mode 100644 index 0000000..0c2904e --- /dev/null +++ b/system_design.md @@ -0,0 +1,467 @@ +# SIP System Design in Go with Consistent Hashing Load Balancing + +## Table of Contents + +1. [Introduction](#introduction) +2. [Requirements](#requirements) +3. [System Architecture Overview](#system-architecture-overview) +4. [Components Description](#components-description) + - [1. SIP Signaling Server](#1-sip-signaling-server) + - [2. Media Gateway](#2-media-gateway) + - [3. Transcoding Service](#3-transcoding-service) + - [4. Conferencing Service](#4-conferencing-service) + - [5. DTMF Handler](#5-dtmf-handler) + - [6. Load Balancing with Consistent Hashing](#6-load-balancing-with-consistent-hashing) + - [7. Session Management (Stateless)](#7-session-management-stateless) + - [8. Monitoring and Logging](#8-monitoring-and-logging) +5. [Data Flow Diagram](#data-flow-diagram) +6. [Technology Stack](#technology-stack) +7. [Handling Edge Cases and Challenges](#handling-edge-cases-and-challenges) +8. [Scalability and High Availability](#scalability-and-high-availability) +9. [Implementation Plan](#implementation-plan) +10. [Testing Strategy](#testing-strategy) +11. [Deployment Strategy](#deployment-strategy) +12. [Future Expansion Planning](#future-expansion-planning) +13. [Conclusion](#conclusion) +14. [Next Steps](#next-steps) +15. [Appendix](#appendix) + +--- + +## Introduction + +This document outlines the design of a scalable SIP system in Go (Golang) that can accept and send SIP calls, handle media transmission using pion/WebRTC, support G.711 and Opus codecs with bidirectional transcoding, and provide conferencing features through audio multiplexing. The system employs consistent hashing for load balancing without the need for a dedicated proxy, ensuring high availability and statelessness. + +--- + +## Requirements + +### Core Functionalities + +- **SIP Call Handling:** Accept and send SIP calls. +- **Media Handling:** Use pion/WebRTC for media transmission. +- **Codec Support:** Support G.711 and Opus codecs with bidirectional transcoding. +- **Conferencing Features:** Implement audio multiplexing for conferencing. +- **DTMF Support:** Handle out-of-band DTMF tones. +- **Future Expansion:** Design with potential support for video codecs. + +### Non-Functional Requirements + +- **Scalability:** Support an average of 500 concurrent calls. +- **High Availability:** Stateless architecture with failover mechanisms. +- **Implementation Language:** Go (Golang). +- **Tools Integration:** + - **Audio Multiplexer:** Use [audio-multiplexer-go](https://github.com/itzmanish/audio-multiplexer-go) for audio mixing and transcoding. + - **SIP Library:** Use [sipgox](https://github.com/emiago/sipgox) for SIP functionalities. + +--- + +## System Architecture Overview + +![System Architecture Diagram](https://user-images.githubusercontent.com/your-username/your-repo/architecture-diagram.png) + + +The system consists of the following key components: + +1. SIP Signaling Server +2. Media Gateway +3. Transcoding Service +4. Conferencing Service +5. DTMF Handler +6. Load Balancing with Consistent Hashing +7. Session Management (Stateless) +8. Monitoring and Logging + +--- + +## Components Description + +### 1. SIP Signaling Server + +**Responsibilities:** + +- Handle SIP signaling for call setup, maintenance, and teardown. +- Parse and construct SIP messages using `sipgox`. +- Manage SIP transactions and dialogs in a stateless manner. + +**Implementation Details:** + +- **SIP Library:** Utilize [sipgox](https://github.com/emiago/sipgox) for SIP functionalities. +- **Stateless Design:** Store minimal state per transaction using tokens or IDs. +- **Consistent Hashing:** Implement consistent hashing based on the `Call-ID` header to route SIP requests to the appropriate server instance. + +**Considerations:** + +- **NAT Traversal:** Use SIP headers and pion/WebRTC's NAT traversal capabilities. +- **Future Video Support:** Design SIP handling to be flexible for future SDP attributes. + +### 2. Media Gateway + +**Responsibilities:** + +- Bridge media streams between SIP endpoints and pion/WebRTC. +- Handle media stream setup using SDP negotiation. +- Forward RTP packets between endpoints. + +**Implementation Details:** + +- **Media Handling:** Use [pion/WebRTC](https://github.com/pion/webrtc) for media transmission. +- **Integration with sipgox:** Coordinate SDP negotiation and media setup. +- **Codec Negotiation:** Manage codec capabilities during SDP negotiation. + +**Considerations:** + +- **Transcoding Integration:** Interface with the Transcoding Service when needed. +- **Scalability:** Instances handle sessions independently due to stateless design. + +### 3. Transcoding Service + +**Responsibilities:** + +- Perform bidirectional transcoding between G.711 and Opus codecs. +- Provide APIs for transcoding operations. + +**Implementation Details:** + +- **Audio Multiplexer:** Use [audio-multiplexer-go](https://github.com/itzmanish/audio-multiplexer-go) for transcoding. +- **Concurrency:** Use Goroutines for efficient transcoding. +- **Service Interface:** Expose transcoding functions internally. + +**Considerations:** + +- **Performance Optimization:** Profile transcoding paths to minimize latency. +- **Resource Management:** Scale instances based on CPU usage. + +### 4. Conferencing Service + +**Responsibilities:** + +- Mix multiple audio streams for conferencing. +- Manage conference sessions and participant lists. + +**Implementation Details:** + +- **Audio Mixing:** Utilize `audio-multiplexer-go` for audio mixing. +- **Session Management:** Assign unique conference IDs and manage participant lists. + +**Considerations:** + +- **Scalability:** Distribute conferencing load across instances. +- **Future Expansion:** Design to handle video streams in the future. + +### 5. DTMF Handler + +**Responsibilities:** + +- Detect and process out-of-band DTMF tones. +- Provide DTMF events to applications or services. + +**Implementation Details:** + +- **RFC 2833 Compliance:** Handle DTMF events per RTP Payload for DTMF Digits. +- **pion/WebRTC Integration:** Use pion's capabilities for DTMF handling. + +**Considerations:** + +- **Accuracy:** Ensure reliable detection for IVR systems. +- **Performance:** Handle DTMF processing asynchronously. + +### 6. Load Balancing with Consistent Hashing + +**Responsibilities:** + +- Distribute SIP requests among server instances without a dedicated proxy. +- Maintain session stickiness to ensure all messages in a SIP dialog reach the same instance. + +**Implementation Details:** + +- **Hash Function:** Use a consistent hash function (e.g., SHA-256) on the `Call-ID` header. +- **Hash Ring:** Represent server instances on a virtual ring with multiple virtual nodes. +- **Request Routing:** Each instance independently computes the hash and determines if it should handle the request. + +**Considerations:** + +- **Synchronization:** Ensure all instances use the same hashing algorithm and configurations. +- **Failure Handling:** Implement mechanisms to update the hash ring upon server changes. + +### 7. Session Management (Stateless) + +**Responsibilities:** + +- Maintain minimal session information required for transaction processing. +- Use tokens or IDs embedded in SIP messages for session correlation. + +**Implementation Details:** + +- **Stateless Tokens:** Embed session identifiers in SIP headers or use the `Call-ID`. +- **Distributed Cache (Optional):** Use Redis if minimal shared state is necessary. + +**Considerations:** + +- **Failover:** Any instance can handle a session based on the hash function. +- **Data Consistency:** Stateless design minimizes consistency issues. + +### 8. Monitoring and Logging + +**Responsibilities:** + +- Monitor system performance and health. +- Collect logs for troubleshooting and analysis. + +**Implementation Details:** + +- **Monitoring Tools:** Use Prometheus and Grafana. +- **Logging:** Implement structured logging. +- **Alerts:** Set up alerting for critical events. + +**Considerations:** + +- **Scalability Monitoring:** Track resource usage for scaling decisions. +- **Call Quality Metrics:** Monitor latency, jitter, and packet loss. + +--- + +## Data Flow Diagram + +1. **Call Initiation:** + + - A SIP endpoint sends an INVITE request. + - All SIP Signaling Server instances compute the hash of the `Call-ID`. + - The instance whose hash range includes the computed hash handles the request. + +2. **SIP Signaling:** + + - The SIP Signaling Server processes the INVITE. + - Performs SDP negotiation for codec selection. + +3. **Media Setup:** + + - The Media Gateway sets up RTP streams using pion/WebRTC. + - If transcoding is required, it interacts with the Transcoding Service. + +4. **Media Transmission:** + + - RTP packets are forwarded between endpoints via pion/WebRTC. + +5. **Conferencing (If Applicable):** + + - Media streams are sent to the Conferencing Service. + - The service mixes audio and sends it back to participants. + +6. **DTMF Handling:** + + - Out-of-band DTMF tones are detected by the DTMF Handler. + +7. **Call Termination:** + + - BYE requests are processed by the SIP Signaling Server. + +--- + +## Technology Stack + +- **Programming Language:** Go (Golang) +- **SIP Library:** [sipgox](https://github.com/emiago/sipgox) +- **Media Handling:** [pion/WebRTC](https://github.com/pion/webrtc) +- **Audio Multiplexing and Transcoding:** [audio-multiplexer-go](https://github.com/itzmanish/audio-multiplexer-go) +- **Load Balancing:** Consistent Hashing implemented within the application +- **Monitoring:** Prometheus and Grafana +- **Containerization:** Docker +- **Orchestration:** Kubernetes + +--- + +## Handling Edge Cases and Challenges + +### 1. Codec Mismatch + +**Solution:** Implement SDP negotiation to select mutually supported codecs. Use the Transcoding Service when necessary. + +### 2. NAT Traversal Issues + +**Solution:** Use pion/WebRTC's built-in STUN/TURN/ICE capabilities. + +### 3. High Load Conditions + +**Solution:** Monitor system load and scale instances horizontally using Kubernetes auto-scaling. + +### 4. Failover and Redundancy + +**Solution:** Implement health checks and update the consistent hash ring when instances become unavailable. + +### 5. Latency and Call Quality + +**Solution:** Optimize media processing paths and adjust jitter buffers as needed. + +### 6. DTMF Detection Accuracy + +**Solution:** Ensure compliance with RFC 2833 and rely on out-of-band DTMF handling. + +--- + +## Scalability and High Availability + +### Scalability + +- **Stateless Architecture:** Enables horizontal scaling. +- **Consistent Hashing:** Distributes load evenly and minimizes impact during scaling. +- **Microservices Approach:** Components can be scaled independently. + +### High Availability + +- **Multiple Instances:** Run multiple instances of each component. +- **Distributed Deployment:** Deploy across different servers or data centers. +- **Health Checks:** Regularly monitor and update the hash ring accordingly. +- **Load Balancing:** Consistent hashing ensures minimal disruption during failures. + +--- + +## Implementation Plan + +### Phase 1: Prototype Development + +- **SIP Signaling Server:** + - Implement basic SIP call handling using `sipgox`. + - Integrate consistent hashing for request routing. + +- **Media Gateway:** + - Set up media transmission with pion/WebRTC. + - Handle basic RTP forwarding without transcoding. + +### Phase 2: Feature Addition + +- **Transcoding Service:** + - Integrate `audio-multiplexer-go` for transcoding between G.711 and Opus. + +- **Conferencing Service:** + - Implement audio mixing using `audio-multiplexer-go`. + +- **DTMF Handler:** + - Add out-of-band DTMF detection and processing. + +### Phase 3: Scalability and Optimization + +- **Load Testing:** + - Simulate high call volumes to test load distribution. + +- **Performance Optimization:** + - Profile and optimize critical paths. + +- **Autoscaling:** + - Configure Kubernetes to scale services based on metrics. + +### Phase 4: High Availability + +- **Failure Handling:** + - Implement mechanisms to detect and handle instance failures. + +- **Consistent Hash Ring Management:** + - Develop protocols for updating the hash ring dynamically. + +### Phase 5: Monitoring and Maintenance + +- **Monitoring Setup:** + - Configure Prometheus and Grafana dashboards. + +- **Logging and Alerts:** + - Implement centralized logging and set up alerts. + +--- + +## Testing Strategy + +- **Unit Testing:** + - Test individual components like SIP message parsing and transcoding functions. + +- **Integration Testing:** + - Test interactions between components such as SIP Signaling Server and Media Gateway. + +- **End-to-End Testing:** + - Simulate complete call flows including conferencing and DTMF handling. + +- **Load Testing:** + - Use tools like [SIPp](http://sipp.sourceforge.net/) to generate SIP traffic. + +- **Failure Testing:** + - Simulate server failures to test consistent hashing and failover mechanisms. + +--- + +## Deployment Strategy + +- **Containerization:** + - Package services as Docker containers. + +- **Orchestration:** + - Use Kubernetes for deployment and scaling. + +- **CI/CD Pipeline:** + - Implement continuous integration and deployment using tools like Jenkins or GitLab CI/CD. + +- **Configuration Management:** + - Manage configurations using environment variables or config maps. + +--- + +## Future Expansion Planning + +- **Video Support:** + - Ensure media handling components are flexible for video codecs and streams. + +- **Additional Codecs:** + - Design the Transcoding Service to add new codecs easily. + +- **Geographical Scaling:** + - Consider deploying regional clusters with DNS-based geolocation routing. + +--- + +## Conclusion + +The proposed system design leverages Go's performance and the capabilities of `sipgox`, `pion/WebRTC`, and `audio-multiplexer-go` to build a scalable, stateless, and high-performing SIP system. Consistent hashing is used for load balancing, ensuring session stickiness without a dedicated proxy. + +--- + +## Next Steps + +1. **Finalize Design:** + - Review the design with stakeholders and incorporate feedback. + +2. **Prototype Implementation:** + - Begin development of core components. + +3. **Testing and Validation:** + - Implement the testing strategy to validate functionalities. + +4. **Deployment:** + - Set up the infrastructure and deploy the system. + +5. **Monitoring and Optimization:** + - Continuously monitor the system and optimize as needed. + +--- + +## Appendix + +### A. Glossary + +- **SIP (Session Initiation Protocol):** Protocol used for initiating, maintaining, and terminating real-time sessions. +- **SDP (Session Description Protocol):** Format for describing streaming media initialization parameters. +- **pion/WebRTC:** Go implementation of WebRTC for media streaming. +- **Consistent Hashing:** A distributed hashing scheme that provides a hash table functionality in a decentralized manner. +- **Goroutine:** Lightweight thread managed by the Go runtime. + +### B. References + +- [sipgox GitHub Repository](https://github.com/emiago/sipgox) +- [pion/WebRTC GitHub Repository](https://github.com/pion/webrtc) +- [audio-multiplexer-go GitHub Repository](https://github.com/itzmanish/audio-multiplexer-go) +- [Consistent Hashing Algorithm](https://en.wikipedia.org/wiki/Consistent_hashing) +- [RFC 3261 - SIP: Session Initiation Protocol](https://tools.ietf.org/html/rfc3261) +- [RFC 2833 - RTP Payload for DTMF Digits](https://tools.ietf.org/html/rfc2833) + +--- + +**Note:** This document is intended to serve as a comprehensive guide for the design and implementation of the SIP system. It should be used in conjunction with detailed technical specifications and development plans. + +# Thank You!