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HTTP/2 & Multiplexing

Medium

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HTTP/1.1 GETLayer 7 · ApplicationHTTP/1.1

Issue

Head-of-line blocking: response 1 must complete before response 2 starts

Headers

Sent as plain text, repeated on every request (e.g. User-Agent, Cookie, Accept)

HTTP/1.1 GETLayer 7 · ApplicationHTTP/1.1

Issue

Head-of-line blocking: response 1 must complete before response 2 starts

Headers

Sent as plain text, repeated on every request (e.g. User-Agent, Cookie, Accept)

The HTTP/1.1 problem: head-of-line blocking

HTTP/1.1 sends one request at a time per connection. To get 3 files: 1. Request file A → wait → response A 2. Request file B → wait → response B 3. Request file C → wait → response C

Head-of-line blocking: if response A is slow, B and C must wait. Workaround: browsers open 6-8 parallel TCP connections per host — but each TCP connection has overhead and competes for bandwidth.

HTTP/1.1 GETHTTP

Packet structure

Payload

HTTP/1.1

Layer details (click to expand)

ApplicationHTTP/1.1

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TransportTCP

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Packets in motion — click to inspect:

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