Hilarious. People called this issue out as an obvious flaw when HTTP/2.0 was first proposed, got ignored, and here the issue is.

For those unfamiliar:

HTTP/2.0 uses an unsigned 31-bit integer to identity individual streams over a connection.

Server-initiated streams must use even identifiers.

Client-initiated streams must use odd identifiers.

Identifiers are not reclaimed once a stream is closed. Once you've initiated (2^31)/2 streams, you've exhausted the identifier pool and there's nothing you can do other than close the connection.

For comparison, SSH channels use a 32-bit arbitrary channel identifier, specified by the initiating party, creating an identifier tuple of (peer, channel). Channel identifiers can be re-used after an existing channel with that identifier is closed.

As a result, SSH doesn't have this problem, or the need to divide the identifier space into even/odd (server/client) channel space.