Advanced Networking

Some advanced networking protocols and URLSession APIs that we can use to improve the connectivity of our mobile application.

Transcript

1. Advanced Networking
2. Ravi Kumar Aggarwal iOS Engineer
 Tokopedia @raviAggarwal61 @ravi.aggarwal61
3. Agenda Multipath TCP Waits For Connectivity Low Data Mode What’s new in HTTP? Future of Networking
4. What’s new in HTTP?
5. HTTP GET (cleartext) HTTP/1.1 200 OK
6. HTTPS
7. HTTP/2
8. Why a New Protocol? SMTP WebSocket UDP POP3 Bonjour LDAP TCP SSH QUAKE3 FTP HTTP DHCP Telnet VoIP ICMP
9. HTTP/1.1 HTTP/2 Multiple TCP connections Head-of-line blocking FIFO restrictions Textual protocol overhead No header compression Only one TCP connection Fully multiplexed Requests have priorities Binary Header compression (HPACK)
10. HTTP/2 Server Push
11. HTTP/1.1 Latency App URLSession Server Time GET index.html index.html Response GET style.css style.css Response GET background.jpg background.jpg Response
12. HTTP/2 Server Push Latency App URLSession Server Time GET index.html index.html Response PUSH 2, 3, n GET Response style.css GET Response background.jpg
14. Pester your server guys…
15. · · Multipath Protocols for Mobile Devices
16. Current Scenario Leaving home
17. Current Scenario Leaving home
18. Current Scenario Leaving home
19. Current Scenario Poor Wi-Fi
20. · Choosing the right interface · Wi-Fi Assist
21. Wi-Fi Assist Triggered by · Marginal Wi-Fi “Fittest Wins Out” contest between Wi-Fi and Cell · Wi-Fi has head start over Cell · On a flow by flow basis, at flow setup time
22. Multipath TCP · Built on top of TCP - Reliability - Congestion control · Seamless handover from Wi-Fi to Cell · Chooses optimal interface for latency-sensitive flows
23. Multipath TCP MPTCP schedules traffic across the interfaces One “TCP subflow” per interface MPTCP creates/destroys subflows URLSession MPTCP Stack TCP subflow
 over Wi-Fi TCP subflow
 over Cellular
24. Multipath TCP Implemented since iOS 7 for Siri User feedback (time to first word) 
 20% faster in the 95th percentile 5x reduction in network failures
25. · Choosing the Multipath Service Type · Multipath TCP
26. Multipath TCP · Handover Mode for high reliability · Interactive Mode for low latency
27. · From Wi-Fi to cellular and back · Handover Mode
28. Multipath TCP Handover Mode
29. Multipath TCP Handover Mode Reliability for persistent connections Minimal cell usage
30. · Reducing latency for our end users · Interactive Mode
31. Multipath TCP Interactive Mode Low latency for low-volume interactive flows Wi-Fi and cellular
32. · URLSessionConfiguration property · Multipath TCP in iOS
33. ```````` Add Capability “Multipath” in Xcode Exposed as URLSessionConfiguration property var multipathServiceType: URLSessionConfiguration.MultipathServiceType
 
 none = 0 handover = 1 interactive = 2 Multipath TCP URLSession
34. Waits For Connectivity
36. URLSession and Connectivity URLSession with defaultSessionConfiguration fetches or fails Lack of connectivity causes URLSessionTasks to immediately fail
 with errors · NSURLErrorNotConnectedToInternet · NSURLErrorCannotConnectToHost
37. Only cellular connectivity, but allowsCellularAccess prohibits cellular Unsatisfactory Connectivity Examples No Ethernet cable, not connected to Wi-Fi network, no cellular signal Device in Airplane Mode VPN not connected
38. Current Solutions Each app must manually retry URLSessionTasks once connectivity 
 is satisfactory When is that? · Monitor conditions with SCNetworkReachability API · Polling/manual retry
39. Wouldn’t it be easier to say… “Please fetch me this resource when the network is available.”
40. Indicates URLSession should monitor network conditions 
 and wait to start tasks Begins network load once connectivity is satisfactory 
 instead of delivering errors · No longer a need to monitor connectivity and 
 manually retry requests New URLSessionConfiguration property var waitsForConnectivity: Bool URLSession Adaptable Connectivity API Built-in connectivity monitoring
41. URLSession Adaptable Connectivity API Insufficient connectivity notification Notification that a URLSessionTask is waiting for connectivity Opportunity to alter app behaviour or indicate status New URLSessionTaskDelegate method · Optional—not required to take advantage of adaptable 
 connectivity functionality · Called at most one time for each URLSessionTask urlSession(_:taskIsWaitingForConnectivity:)
42. Always enable waitsForConnectivity URLSession Adaptable Connectivity API When to enable it No downside—if connectivity is available, tasks will start right away General recommendation Exception Requests that must be completed immediately, or not at all for example, “Fill or Kill” stock trading transaction
43. Low Data Mode
44. Low Data Mode User preference to minimise data usage · Explicit signal to reduce network data use · Per Wi-Fi and Cellular network System policy · Discretionary tasks deferred · Background App Refresh disabled
45. Always save network data when there is no impact on user experience.
46. Application Adoption Reduce image quality Reduce pre-fetching Synchronise less often Mark tasks discretionary Disable auto-play Do not block user-initiated work
47. URLSession · Try large/prefetch with allowsConstrainedNetworkAccess = false · On failure with error.networkUnavailableReason == .constrained try Low Data Mode alternative Low Data Mode APIs
48. Future of Networking QUIC HTTP/3?
49. QUIC Quick UDP Internet Connection Experimental Much faster than TCP based protocols Proposed to become the basis for HTTP/3
50. Thank You