Header Compression
In HTTP2
HTTP2 Provided
- Stream Multiplexing
- Binary Framing Layer
- Flow Control
- Server Push
- Priorities and dependencies
- Header Compression
RFC 7541:
RFC 7540:
HTTP2 is all about performance on the client side
We want:
- reduce RTT
- reduce latency
- reduce packet size
In HTTP/1.1
We are using:
- HTML compression by remove whitespace :)
- gzip
- combo
In HTTP/2
We can use:
- Header compression
Why we need Header Compression
25% network traffic is the protocol overhead
What is HPACK
(Copy from ilya grigorik's ppt)
Static Dictionary
Dynamic Table
- manage the header fields which is unlisted in static table
- sharing the table on the same connection (connection sensitive)
- consists of a list of header fields maintained in FIFO order
Static Huffman Encoding
- this code was generated from statistics obtained
- no known attack against a static Huffman encoding
HPACK Detail
Indexed Header Field Representation
已被索引的头部
Literal Header Field with Incremental Indexing -- Indexed Name
name在索引 value不在索引
Literal Header Field with Incremental Indexing -- New Name
name, value都没被索引
Literal Header Field without Indexing -- Indexed Name
name被索引， value未索引且不添加至动态字典
Literal Header Field without Indexing -- Indexed Name
name, value都未被索引且不添加至动态字典
Literal Header Field Never Indexed -- Indexed Name
name在索引表中， value不在，且绝对不允许被索引
Literal Header Field Never Indexed -- New Name
name 和 value 都不在索引表中，且绝对不允许被索引
How to test
brew update
brew install nghttp2
h2load https://anyh2website.com -n 2 | tail -6 |head -1
Reference
Thanks
Q ?
HTTP2
By 知白 Saviio
