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addrv2 BIP proposal #766

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laanwj commented Feb 27, 2019

Proposal for wider v2 address messages.

Last time this went around (as a github gist) there were some considerations still to be discussed, for lack of a working mailing list I'll post them here:

Considerations

  • ''Client MAY store and gossip address formats that they do not know about'': does it ever make sense to gossip addresses outside a certain overlay network? Say, I2P addresses to Tor? I'm not sure. Especially for networks that have no exit nodes as there is no overlap with the globally routed internet at all.

  • Lower precision of time field? seconds precision seems overkill, and can even be harmful, there have been attacks that exploited high precision timestamps for mapping the current network topology.

    • (gmaxwell) If you care about space time field could be reduced to 16 bits easily. Turn it into a "time ago seen" quantized to 1 hour precision. (IIRC we quantize times to 2hrs regardless).
  • Rolling port into addr, or making the port optional, would make it possible to shave off two bytes for address types that don't have ports (however, all of the currently listed formats have a concept of port.). It could also be an optional data item (see below).

  • (gmaxwell) Optional (per-service) data could be useful for various things:

    • Node-flavors for striping (signalling which slice of the blocks the node has in selective pruning)

    • Payload for is alternative ports for other transports (e.g. UDP ports)

    • If we want optional flags. I guess the best thing would just be a byte to include the count of them, then a byte "type" for each one where the type also encodes if the payload is 0/8/16/32 bits. (using the two MSB of the type to encode the length). And then bound the count of them so that the total is still reasonably sized.

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