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    这个是一个自己工作中小组内的一个简单分享，关于HTTP2各种内容。以HTTP2作为标题，结合了一些工作里的业务场景，内容主要还是要靠讲的，并且在语速比较快的情况下也说了约40分钟，所以只能偷懒上些ppt的内容了。当然作为国际部门，现在内部要求都要英文交流，所以ppt也是英文的...

    HTTP History

  • Concept Hypertext (1963)
  • HTTP 0.9 (before 1995)
  • Only get, no header, 1 page
  • HTTP 1.0 (1996)
  • Header, response code, redirect, post. Etc, 60 pages
  • HTTP 1.1 (1999)
  • Options, upgrade, cache header extends
  • SPDY (2009 google)
  • HTTP2 (2012, 2015/5/14 published)

    • HTTP2 related

  • Server (google)
  • Proxy (akamai)
  • Client (google firefox)

    • HTTP2 Features

  • One Connection
  • use one connection for parallelism （ares oversea）
  • Header Compression
  • uses header compression to reduce overhead
  • Server Push
  • allows servers to “push” responses proactively into client caches

    • HTTP2 Requirement

  • Stage 1 (NPN)
  • Web server supported H2 (nginx 1.9.5+)
  • TLS certificate (Let' s Encrypt)
  • Chrome 41, Firefox 36, Edge 12, Safari 9, Opera 28
  • Stage 2 (ALPN)
  • OpenSSL 1.0.2g
  • Chrome 51

    • Site: HTTP1.1 vs HTTP2

    sample demo parse

    Questions about connection

  • How many connections browser can open, and why?
  • How many connections system can maintain?
  • What’s the ideal delay between Shanghai and New York?

    • Windows connections

    ref: http://smallvoid.com/article/winnt-tcpip-max-limit.html

  • TCP connection allow: TcpNumConnections = 16M
  • Max dynamic ports: MaxUserPort = 5000 （1024 to 5000）
  • TCP control block: MaxFreeTcbs = 1000 (srv = 2000)
  • 0.5k for pagepool and 0.5k for non-pagepool
  • TCB HashTable: MaxHashTableSize = 512 (Default = 512, Range = 64-65536)
  • Pagepool
  • allocated a 1000 TCBs == 1000 connection, close connection occupy port 4min: TcpTimedWaitDelay = 240 sec
  • Without closing the connection properly: KeepAliveTime = 2 h

    • result: < 1000

    Http1 problems

  • Head of line blocking
  • Inefficient of TCP usage rate
  • Slow start
  • Congestion window
  • Etc...

    • Http1.1 Optimization

  • Sprite Image
  • Domain sharding
  • Disable cookie
  • File concat

    • Then use http2

    Http1.1 Optimization in H2

  • Sprite Image
  • It depends, heigh cost, bg image load when visible
  • Domain sharding
  • wrong
  • Disable cookie
  • wrong
  • File concat
  • It depends, unnecessary almost

    • Client Support detect

  • Upgrade header
  • TLS
  • NPN (Next Protocol Negotiation)
  • ALPN (Application Layer Protocol Negotiation)
  • HTTP Alternative services

    • Upgrade header

    GET ws://example.com/ HTTP/1.1
Connection: Upgrade
Upgrade: websocket
Origin: http://swordair.com
Sec-WebSocket-Version: 13
Sec-WebSocket-Key: xxx

    HTTP/1.1 101 Switching Protocols 
Connection: Upgrade 
Upgrade: websocket 
Sec-WebSocket-Accept: xxxxx

    GET / HTTP/1.1 Host: example.com
Connection: Upgrade, HTTP2-Settings
Upgrade: h2c
HTTP2-Settings: <base64url encoding of HTTP/2 SETTINGS payload>

    Unsupport:
HTTP/1.1 200 OK
Content-Length: 243
Content-Type: text/html

    Unsupport:
HTTP/1.1 200 OK
Content-Length: 243
Content-Type: text/html

    but, just exist in RFC actually

    ALPN

    TLS connection ‘Client Hello’

    Client double confirm

    Connection preface

    PRI * HTTP/ 2. 0\ r\ n\ r\ nSM\ r\ n\ r\ n
  • SETTINGS client
  • SETTINGS ack server

    • HTTP2 basics

  • TCP socket
  • Steam
  • Frame

    • HTTP2 Steam

  • Steam is H2 independent, two-way frame change
  • A new request will rise a new steam
  • Steam id

    • H2 Frame

  • HTTP based on ‘Text splite’
  • HTTP2 based on Frame (key of one connection for parallelism)

    • Frame Type

    NAME ID DESC
    DATA
    0x0
    Steam data
    HEADERS
    0x1
    http header
    PRIORTY
    0x2
    Priority of steam
    RST_STEAM
    0x3
    Stop steam (error)
    SETTINGS
    0x4
    Set connection param
    PUSH_PROMISE
    0x5
    Server push tips
    PING
    0x6
    Test connection and rtt
    GOAWAY
    0x7
    Steam end
    WINDOW_UPDATE
    0x8
    Flow control
    CONTINUATION
    0x9
    Extends HEADERS frame

    Header Compression

  • deflate & CRIME (Compression Ratio Info-leak Made Easy)
  • Gzip is unsafe
  • HPACK
  • Header infos are similar
  • Index specific header and value

    • HPACK sample

    Header1: All work and no play
Header2: makes Steven
Header3: a dull boy

    Client generate this index and send to server, server will also create one

    Index Header name Value
    55
    Header1
    All work and no play
    56
    Header2
    makes Steven
    57
    Header3
    a dull boy

    Next item send: 55 56 57

    Every connection maintain it’s index status.

    Server Push

  • Reasonable push decrease 20% - 50% render time
  • Push will waste bandwidth (resource cached already)
  • Best Timing:
  • Server busy
  • Client idle
  • Frame Type “PUSH_RPOMISE”
  • Client can reject use “RST_STEAM”

    • FTTB in H2

    H2 Extra work:

  • Window size adjust
  • Dependency tree
  • Index header
  • Header compression
  • Priority change
  • Server pre push

    • Performance:
    H2 <= H1

    Experience
    H2 > H1

    HTTP2 debug

  • chrome://net-internals/ （early version）
  • Chrome debug tool -> network tab
  • Session key logging (env SSLKEYLOGFILE=~/key.log) wireshark
  • Firefox command mode record HTTP session log

    • TCP and UDP

  • TCP is not fast portocal but it is reliable
  • But we need more fast net

    • core problen is:

  • TCP/IP is integrated in system core
  • TCP is in core space
  • UDP is in user space

    • QUIC

  • Quick UDP Internet Connection
  • Google
  • Based on UDP which in user space
  • Provide equivalent HTTP2 new features

    • HTTP3 ?

    FIN

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