HTTP 1.1

Properties

An HTTP request consists of the following:

• Method -> GET, POST, PUT, DELETE, PATCH, OPTION
• PATH -> domain.tld/path?pathwith=parameters
• Protocol -> HTTP/1.1, HTTP/2
• Headers ->
• Body -> Payload

An HTTP response consists of the following:

• Protocol
• Code -> 200, 404, 503, etc. status codes
• Code Text -> Ok, Not Found, Internal server error, etc., the description of the above codes
  • It got removed in HTTP/2
• Headers
• Body

HTTP/1.1 response

HTTP/2 response

HTTP/1.0

• New TCP connection with each request -> Initially, keeping a connection open was costly.
• Slow
• Buffering (transfer-encoding: chunked didn't exist)
• No multi-homed websites (HOST header) -> Vercel.com hosting multiple websites would not have worked.

HTTP/1.1

• Persisted TCP Connection
• Low Latency & Low CPU Usage
• Streaming with Chunked transfer
• Pipelining (disabled by default) -> Due to ordering requirements like HTML needs to come first, then images.

HTTP/2

• SPDY
• Compression
• Multiplexing
• Server Push
• Secure by default
• Protocol Negotiation during TLS (NPN/ALP)
• It needs a secure connection. It is not backward compatible.
  We will learn more on HTTP/2.

HTTP over QUIC (HTTP/3)

• Replaces TCP with QUIC (UDP with Congestion control)
• AIL HTTP/2 features
• Without HOL
  We will learn more on HTTP/3.