Getting the best out of WebRTC
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This document discusses best practices for deploying WebRTC to replace or augment existing SIP-based phone systems. It covers choosing appropriate codecs to balance bandwidth usage and call quality for different use cases. It also addresses WebRTC-specific considerations like ICE, DTLS, and asymmetric call patterns. Performance metrics are provided from test calls using different codecs on an Asterisk server. The presentation includes diagrams of common WebRTC deployment architectures and links to live demos.
Getting the best out of WebRTC
- 1. Getting the Best out of WebRTC Tim Panton - Protocol Droid - Westhawk Ltd Dan Jenkins - Chief Ape - nimblea.pe & Respoke
- 2. Simple 1 for 1 replacement ? No! Bandwidth / CPU use are different
- 3. How to plan a deployment A talk in two parts
- 5. Practical numbers and graphs
- 6. Assumptions If you are here you are probably Doing this commercially - Quality matters Using Asterisk - Hybrid model with some PSTN Have Asymmetric calls - agents and users Are on a tight bandwidth and CPU budget Video not top priority (yet) Have a clue
- 8. Video Peer Calls Video User Agent Internet SIP Audio HTML Context Asterisk Webservice
- 9. Internal Audio Agents Asterisk L A N App Server User P S T N Agent Agent Agent Agent Agent
- 10. External Audio Agents I N T E R N E T User P S T N Agent Agent Agent Agent Agent WebRTC App Server Asterisk
- 11. External Audio Users L A N User I N T E R N E T Agent Agent Agent Agent Agent DeskPhones HTML WebRTC Audio App Server Asterisk SIP Phones
- 12. Hybrid L A N User I N T E R N E T Agent Agent Agent Agent Agent DeskPhones WebRTC Audio HTML App Server Asterisk Agent WebRTC SIP Phones PSTN Audio FAX SMS User Skype Twitter Chat Email Facebook
- 13. WebRTC issues How webRTC differs from plain old SIP ICE - can penetrate NAT at cost of setup time DTLS - encrypted traffic but call setup costs CPU Web service - may expose your Asterisk SRTP - encrypted media costs some CPU too.
- 14. Codecs Codecs implemented in browsers today: ULAW - old favourite - high bandwidth/ low cpu 2 quality modes - landline or incomprehensible Opus - new comer - low bandwidth / high cpu flexible quality and error correction settings VP8 - free video codec - High but variable bandwidth H264 - licensed video codec - free if < 100k (IANAL)
- 15. Codecs - ideal choices (audio only) Codec Setting Reasoning P2P video Opus None The browser knows best Int Agents ulaw None low loss on LAN + will end up on PSTN Ext Agent Opus High BW / low loss Can set minimum DSL standards for staff Ext User Opus Low BW / high loss Users share DSL with web/games etc Note - Digium does not support opus on Asterisk
- 16. DTLS - crypto selection
- 17. WebRTC uses DTLS to generate SRTP key Different Cypher suites Different key lengths Multiple certificate sources All impacts CPU usage at call setup.
- 18. ICE - Tricks
- 19. Assume your asterisk has a public IP Probably don’t need a TURN server Avoid offering candidates for internal IPs Don’t offer VPN candidates Can probably get away with setting ice-lite
- 21. In future we expect more asymmetric cases Mayday - they see your screen not you Baby monitor - 1 way video but 2 way audio ? Security cameras
- 22. What does that all mean in practice Probably: Higher CPU use (especially with Opus) Longer call setup times Very high bandwidth with Video (if enabled)
- 23. Tools to monitor Probably: WebRTC stats (Respoke Stats) www.npmjs.org/package/getstats chrome://webrtc-internals CollectD / Graphite
- 24. Some Numbers Test scenario: Asterisk: 11.8.1 on machine: Centos Intel(R) Core(TM) i3-4010U CPU @ 1.70GHz Chrome 38 Ramp up 24 calls Play back intermittent audio (IVR usage) Graph - bandwidth / CPU / calls / time
- 25. 24 ulaw audio calls Graph
- 26. 24 opus audio calls - No settings Graph
- 27. 24 opus audio calls Low BW high loss Graph
- 28. Some MORE “Numbers” Test scenario: Digital Ocean Medium Droplet San Francisco
- 29. 1 P2P video call - LAN/WAN http://bit.ly/dt-demo
- 30. 1 P2P video call - WAN http://bit.ly/dt-demo
- 31. Live demo using respoke Chrome (android too) browse here! URL: http://bit.ly/dt-asterisk
- 32. Thank you! Questions? More info at: github.com/danjenkins/web-examples @dan_jenkins @steely_glint www.respoke.io
- 33. Images Used http://upload.wikimedia.org/wikipedia/commons/c/ca/Padlock_2010.JPG http://upload.wikimedia.org/wikipedia/commons/8/8e/ Ice_road_in_the_Northwest_Territories_-a.jpg http://upload.wikimedia.org/wikipedia/commons/4/41/Asymmetric_%28PSF %29.png