Clarify and document how socket/network or application level timeouts should be configured

Describe the problem

Server side fetch fails with

error TypeError: fetch failed
    at fetch (C:\Users\some-user\some-sveltekit-projekct\node_modules\undici\index.js:105:13)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
  cause: ConnectTimeoutError: Connect Timeout Error
      at onConnectTimeout (C:\Users\some-user\some-sveltekit-projekct\node_modules\undici\lib\core\connect.js:176:24)
      at C:\Users\some-user\some-sveltekit-projekct\node_modules\undici\lib\core\connect.js:123:46
      at Immediate._onImmediate (C:\Users\some-user\some-sveltekit-projekct\node_modules\undici\lib\core\connect.js:162:33)
      at process.processImmediate (node:internal/timers:471:21) {
    code: 'UND_ERR_CONNECT_TIMEOUT'
  }
}

How should developers deal with services that are

• slow during TCP/TLS handshake, "connect" phase
• slow when reading from the client (= sveltekit sending request)
• slow when writing to the client (= sveltekit waiting for response)

During connect, read and write timeouts can make the request fail. It is not clear how these can be configured

• depending on the platform/adater used
• depending on whether fetch is server side (= undici package) or client side ( = browser)

Related discord discussion

Describe the proposed solution

Clarify and document in sveltekit and adapters how different types of timeouts can be configured.
Is it correct that fetch (browser and/or undici?) supports http/1.1 only and is this a disadvantage? Is support for http2 or even http3 useful for reliability and performance?

Alternatives considered

No response

Importance

i cannot use SvelteKit without it

Additional Information

Nmap result when the service has a TCP connect timeout:

sudo nmap -Pn -sS -p 443 api.insee.fr
Starting Nmap 7.93 ( https://nmap.org ) at 2023-01-23 17:04 CET
Nmap scan report for api.insee.fr (143.196.255.207)
Host is up.
Other addresses for api.insee.fr (not scanned): 194.254.37.207

PORT    STATE SERVICE
443/tcp filtered  https

Nmap done: 1 IP address (1 host up) scanned in 3.15 seconds

Nmap result when the service does not have a TCP connect timeout:

sudo nmap -Pn -sS -p 443 api.insee.fr
Starting Nmap 7.93 ( https://nmap.org ) at 2023-01-23 17:04 CET
Nmap scan report for api.insee.fr (143.196.255.207)
Host is up (0.044s latency).
Other addresses for api.insee.fr (not scanned): 194.254.37.207

PORT    STATE SERVICE
443/tcp open  https

Nmap done: 1 IP address (1 host up) scanned in 1.29 seconds

The report points to server-side fetch through node_modules/undici/index.js and lib/core/connect.js, and asks about adapter- and browser-specific behavior; start by tracing those fetch entry points and existing adapter documentation. Done means documenting how connect, read, and write timeouts are configured across the mentioned environments and adapters.