Customizable Network Sizes

[cramt]

During stream morning stream james mentioned the possible future problem of "what if people wanna have really large networks".

A simple solution could be for the protocol to be generic

static STACK_U8: NetStack<u8, CSRMutex, Null> = NetStack::new();
static STACK_U16: NetStack<u16, CSRMutex, Null> = NetStack::new();
static STACK_U32: NetStack<u32, CSRMutex, Null> = NetStack::new();
//etc...

These would all be completely incompatible protocols, but since the intended use-case for ergot is not an global public internet protocol but a private closed one where all the parts are probably maintained by the same team. They just have to collectively decide on their network would best be served by having network ids be at a max of 2^8, 2^16 or 2^32.

For a simpler api it might smart to default this generic parameter to u16.

If this has some unforeseen consequence an alternative could also just be to have different features that could be enabled for the different sizes, u8, u16, u32, u64 and u128, Though this approach is less flexible than generics, but would mean technically not using generics if this courses some problem in the implementation

[jamesmunns]

Discussed a bit here: https://youtube.com/live/NKvU0w3IZQg

This seems interesting, but is probably a "not for now" design question!

[jamesmunns]

The more I think about this, the more I wonder if this would leave a door open for larger desktop to desktop comms. One mitigation we could do soonish (or at least before stabilizing) would be to limit net_ids and ports to <= 127, which matches a 1-byte varint limit (this would be annoying for broadcast messages, we might need to move that ID to 1 or something), and then in the future we could make a non-breaking wire change to make these arbitrary varints.

That being said: I still worry about compatibility: you could have a network with u32.u32:u32 addresses, and a device with u16.u8:u8 addresses, and they would MOSTLY work with each other, but ONLY if the u32.u32:u32 network only has small net/node/port numbers, which I could be very frustrating to debug if SOMETIMES it worked (because you happen to have 10.15:25 as a source), and SOMETIMES it doesn't (because you happen to have 10.15:1255 as a source).