=====================
Introducer Expiration
=====================
Author: zzz
Created: 2017-02-05
Thread: http://zzz.i2p/topics/2230
Last updated: 2017-08-09
Status: Closed
Target: 0.9.30
Implemented in: 0.9.30


Overview
========

This proposal is about improving the success rate for introductions. See
[TRAC-TICKET].


Motivation
==========

Introducers expire after a certain time, but that info isn't published in the
[RouterInfo]. Routers must currently use heuristics to estimate when an
introducer is no longer valid.


Design
======

In an SSU [RouterAddress]  containing introducers, the publisher may optionally
include expiration times for each introducer.


Specification
=============

  iexp{X}={nnnnnnnnnn}

  X :: The introducer number (0-2)

  nnnnnnnnnn :: The time in seconds (not ms) since the epoch.


Notes
`````
* Each expiration must be greater than the publish date of the [RouterInfo],
  and less than 6 hours after the publish date of the RouterInfo.

* Publishing routers and introducers should attempt to keep the introducer valid
  until expiration, however there is no way for them to guarantee this.

* Routers should not use a published introducer after its expiration.

* The introducer expirations are in the [RouterAddress]  mapping.
  They are not the (currently unused) 8-byte expiration field in the [RouterAddress].

Example: ``iexp0=1486309470``


Migration
=========

No issues. Implementation is optional.
Backwards compatibility is assured, as older routers will ignore unknown parameters.



References
==========

[RouterAddress]
    http://i2p.net./spec/common-structures#struct-routeraddress

[RouterInfo]
    http://i2p.net./spec/common-structures#struct-routerinfo

[TRAC-TICKET]
    http://trac.i2p2.de/ticket/1352