HTTP2 分享记录

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

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

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