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Introducing HTTP/2
HTTP/2 is a new version of the HTTP network protocol that makes web content delivery faster and more efficient. It introduces features like multiplexing, header compression, and server push that fix limitations in HTTP/1.1 like head-of-line blocking and slow start. HTTP/2 is now supported in all major browsers and servers and provides performance improvements over HTTP/1.1 without requiring workarounds. The presentation provided an overview of HTTP/2 concepts and how to troubleshoot using developer tools.
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Overview of presenter, Ido Flatow. Introduction to HTTP/2 with focus on web technologies.
Discussion on HTTP 1.1 limitations, including request limits, latency issues, and performance impacts.
Examination of latency, request reduction strategies, and how HTTP/2 addresses these shortcomings.
Introduction of SPDY as precursor to HTTP/2, discussing its features and integration into HTTP/2 specifications.
Overview of HTTP/2 connections (over TLS and TCP), emphasizing multiplexing, prioritization, and header compression.
Comparison between HTTP/1.1 and HTTP/2 connections, along with browser and server support for HTTP/2.
Details of HTTP/2 frame types, including various functionalities and the importance of HPACK header compression.
Demonstration of Wireshark for troubleshooting HTTP/2, including SSL sniffing setup.
Explanation of server push in HTTP/2, detailing resource pushing after initial HTML response.
Final thoughts on HTTP/2 improvements, including multiplexing, prioritization, and reduction of HTTP 1.1 hacks.
Links to resources for further reading and exploration of HTTP/2 specifications and implementation details.
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Introducing HTTP/2
- 1. © Copyright SELASoftware & Education Labs Ltd. | 14-18 Baruch Hirsch St Bnei Brak, 51202 Israel | www.selagroup.com Ido Flatow Introducing HTTP/2
- 2. About Me Senior Architect,Sela Group Other titles: Microsoft Regional Director, IIS/ASPNET MVP Co-author of courses and books Focus on server, web, and cloud Manager of the Israeli Web Developers User Group
- 3. Agenda Web (HTTP 1.1)and its current state What is (HTTP/2) – and how fast is it? Goals of HTTP/2 HTTP/2 concepts How to troubleshoot
- 4. Web – CurrentState HTTP 1.1 is huge HTTP 1.0 RFC 1945 – released 1996 – 60 pages HTTP 1.1 RFC 2626 – released 1999 – 176 pages Now split into 6 documents – RFC 7230 and family Incomplete implementation of RFC Eg. HTTP pipelining Inadequate use of TCP
- 5. Average Request +150%in 3 Years Jan 2012 – Nov 2015 (http://httparchive.org) top 1000 sites
- 6. Shortcoming – CurrentWeb Concurrent connection limit Head of line blocking TCP slow start Latency – page load time
- 7. Max Persistent Connections FromHTTP 1.1 RFC: “Clients that use persistent connections SHOULD limit the number of simultaneous connections that they maintain to a given server. A single-user client SHOULD NOT maintain more than 2 connections with any server or proxy. … These guidelines are intended to improve HTTP response times and avoid congestion.” Firefox 2 – 2 Firefox 3 and on – 6 Opera 9.26 – 4 Opera 12 – 6 Safari 3 – 4 Safari 5 – 6 IE 7 – 2 IE 8 – 6 IE 10 – 8 Chrome – 6 Avg. TCP connections during page load (Last 18 months)
- 8. Head-of-Line Blocking (No Pipelining) Eachconnection can only handle one request at a time If current request blocks, next request will wait HTTP 1.1 defines pipelining, but most browsers do not implement it
- 9. TCP Slow Start TCPdoes not use the full bandwidth capacity from start TCP probes network to find available capacity
- 10. Latency vs Bandwidth Averageweb page has over 100 objects to download Largest impact on page load time is latency, not bandwidth https://www.akamai.com/us/en/our-thinking/state-of-the-internet-report
- 11. What is 20msof Latency? (RTT = Round-trip time)
- 12. What Have weDone to Improvise? Reduce # of requests and latency overhead Spriting Concatenation (JavaScript, CSS) Inlining Overcome max connection limit Domain sharding
- 13. Problems with “optimizations” Spriting Painfuland annoying preprocessing, cache invalidations, slower executions Inlining Resource can’t be cached, inflates parent document by 33% overhead Concatenation Less modular code, expensive cache invalidators, slower execution Domain sharding TCP slowstart, excessive DNS lookup, latency
- 14. HTTP/2 to theRescue Improve latency and less RTT sensitive Fix pipelining and remove “head of line blocking” Does not require multiple connections Achieved all this by retaining semantics of HTTP 1.1
- 15. It Began withSPDY Originally proposed by Google as a wire format extension to HTTP in 2011 Implements all the major features of HTTP/2 Serves as a testbed for improvements to HTTP Without the burden of standardization SPDY became the basis of HTTP/2 in 2012 SPDY will cease to exist in 2016, making way to HTTP/2
- 16. What is HTTP/2 HTTP/2uses a single, multiplexed connection Max connection limit per domain can be ignored HTTP/2 compresses header data and sends it in a concise, binary format Better than the plain text format used previously Less need for popular HTTP 1.1 optimizations
- 17. HTTP/2 Specification Started withSPDY - draft 3 Comprised out of two specifications HTTP/2 – RFC7540 HPACK (header compression) – RFC7541 Implementations HTTP/2 over TLS (h2) HTTP/2 over TCP (h2c)
- 18. HTTP/2 Over TLS(h2) HTTP/2 shipped with TLS as optional Firefox and Chrome developer teams stated they will only implement HTTP/2 over TLS Today, only HTTPS:// is allowed for HTTP/2 TLS must be at least v1.2, with cipher suite restrictions https://http2.github.io/http2-spec/#BadCipherSuites
- 19. HTTP/2 Over TCP(h2c) Uses the Upgrade header Plans to support on IE, already supported in CURL GET /page HTTP/1.1 Host: server.example.com Connection: Upgrade, HTTP2-Settings Upgrade: h2c HTTP2-Settings: (SETTINGS payload) HTTP/1.1 200 OK Content-length: 243 Content-type: text/html (... HTTP/1.1 response ...) --- or --- HTTP/1.1 101 Switching Protocols Connection: Upgrade Upgrade: h2c (... HTTP/2 response ...)
- 20. HTTP/2 in OneSlide One TCP connection Request → Stream Streams are multiplexed Streams are prioritized Binary framing layer Prioritization Flow control Server push Header compression (HPACK)
- 21. TCP Connections -HTTP 1.1 vs HTTP/2 HTTP 1.1 HTTP/2 Client http://www.url.com Client http://www.url.com
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- 23. How to Troubleshoot- Dev Tools
- 24. HTTP/2 Support Servers Microsoft IIS10 (Win 10 / Server 2016) Apache 2.4.12 Nginx 1.9.5 Jetty 9.3 Many more… Browsers Edge IE11 (Windows 10) Firefox 40+ Chrome 43+ Safari 9+ Opera 32+ iOS Safari 9.1+ Chrome for Android 46+ CURL Google, Facebook, Twitter and many more are using HTTP/2 already HTTP/2 is used by 4.5% of all websites (Dec. 2015 http://w3techs.com)
- 25. HTTP/2 Multiplexing Each request/responsestream has an ID Streams comprise of frames (Header, Data…) TCP connection can have multiple streams Frames can be interleaved in the TCP channel Stream dependencies control frame prioritization Server (IIS/ASP.NET) sees streams as TCP connections
- 26. Frame Types Frame typeDescription DATA HTTP body HEADERS Header fields PRIORITY Sender-advised priority of stream RST_STREAM Signal termination of stream SETTINGS Configuration parameters for the connection PUSH_PROMISE Signal a promise (push) of referenced sources PING Measure roundtrip time and “liveness” GOAWAY Inform peer to stop creating streams for current connection WINDOW_UPDATE Connection flow control CONTINUATION Continue a segment of header block fragments
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- 29. How to Troubleshoot- Wireshark Works with Chrome and Firefox only (Windows, Linux, Mac) Set SSLKeyLogFile for HTTPS sniffing Wireshark->Preferences->Protocols->SSL C:> set SSLKEYLOGFILE=c:tempsslkeylog.log
- 30. How to Troubleshoot- Wireshark
- 31. How to Troubleshoot- Wireshark
- 32. How to Troubleshoot- Wireshark
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- 34. Server Push (Promise) Afterthe server responds with an HTML, it waits for requests to embedded resources Server code knows which resources client needs JavaScript CSS Images HTML pages of future navigation Why not just push it to the client along with the HTML? In ASP.NET, use HttpResponse.PushPromise string path = Request.ApplicationPath; Response.PushPromise(path + "/Images/1.png"); Response.PushPromise(path + "/Images/2.png");
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- 36. Summary Multiplexing Multiple requests andresponses Fixes head-of-line blocking problem Avoid the HTTP 1.1 hacks Mechanism for request prioritization Fewer TCP connections Reduces TCP slow start Header compression Server Push
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Editor's Notes
- #5 Pipelining in HTTP 1.1 is mostly supported in browsers, but not in proxies
- #11 Diagrams via Akamai’s state of the Internet statistics https://www.igvita.com/2012/07/19/latency-the-new-web-performance-bottleneck/
- #22 TLS must support SNI, disable compression and re-negotiation, minimal key length for ephemeral key exchange