Overview

This proposal is about implementing proper multihoming support in I2P that can scale up to large sites.

Motivation

Multihoming is a hack and presumably won't work for e.g. facebook.i2p at scale. Say we had 100 multihomes each with 16 tunnels, that's 1600 LS publishes every 10 minutes, or almost 3 per second. The floodfills would get overwhelmed and throttles would kick in. And that's before we even mention the lookup traffic.

We need some sort of meta-LS, where the LS lists the 100 real LS hashes. This would be long-lived, a lot longer than 10 minutes. So it's a two-stage lookup for the LS, but the first stage could be cached for hours.

Specification

The meta-LeaseSet would have the following format:

- Destination
- Published Time stamp
- Expiration
- Flags
- Properties
- Number of entries
- Number of revocations

- Entries. Each entry contains:
  - Hash
  - Flags
  - Expiration
  - Cost (priority)
  - Properties

- Revocations. Each revocation contains:
  - Hash
  - Flags
  - Expiration

- Signature

Flags and properties are included for maximum flexibility.

Comments

This could then be generalized to be a service lookup of any type. The service identifier is a SHA256 hash.

For even more massive scalability, we could have multiple levels, i.e. a meta-LS could point to other meta-LSes.