feature request: sip003 mux / multiplexing spec

[liudongmiao]

There is no relay in sip003, currenty it's implemented by plugin self.

• v2ray-plugin: use Mux.Cool
  • Mux.Cool can be turned off by set mux to 0

As it's shadowsocks is based on socks, entire payload can be encrypted, so there is no mux solution on shadowsocks payload.

Then, the mux should be done on plugin:

1. mux on payload, add mux header before payload
   1. Mux.Cool
   2. please note: it seems no way to compatible mux and non mux solution as mux header is not optional
2. mux on plugin's underlying protocol
   1. websockets based on http/1.1, use websockets's rsv and/or opcode.
      1. please note, there should be some simple stream flow control
   2. http2/http3, special stream and stream flow control
   3. other: I don't think other protocol can be supported by cdn

[liudongmiao]

There is another simple mux by @IrineSistiana at https://github.com/IrineSistiana/simple-mux

However, it's not standard, and the head length is 7 bytes.

For websocket, the head length is maximum 14 bytes, however, if we don't support more than 2**16 = 64K, the client data frame is 6 or 8 bytes (including mask 4 bytes), and the server data frame is 2 or 4 bytes (without mask 4 bytes). For mux, we can use 3 rsv bits, can support max 8 channel, and there are 10 unused opcodes, can be max to 18. For close stream, I'd suggest a payload length 0, as it's illegal for underlyling data, they never send data in 0. For ping / pong, there're in websockets.