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Prop140:

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- Add definitions of user, client (with sub-definitions for balancer, frontend
  and backend), and router
- Replace "edge router" with "router"
- Add a second diagram showing a multi-client setup with split-out balancer,
  frontends and backend
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str4d
2017-07-04 18:21:24 +00:00
parent 4de3987af6
commit 334b6df0e4
1 changed files with 121 additions and 59 deletions
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180
i2p2www/spec/proposals/140-invisible-multihoming.rst
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@@ -5,7 +5,7 @@ Invisible Multihoming
:author: str4d
:created: 2017-05-22
:thread: http://zzz.i2p/topics/2335
:lastupdated: 2017-05-22
:lastupdated: 2017-07-04
:status: Open
.. contents::
@@ -14,8 +14,9 @@ Invisible Multihoming
Overview
========
This proposal outlines a design for a protocol enabling an I2P client or service
to transparently use multiple routers to host a single [Destination]_.
This proposal outlines a design for a protocol enabling an I2P client, service
or external balancer process to manage multiple routers transparently hosting a
single [Destination]_.
The proposal currently does not specify a concrete implementation. It could be
implemented as an extension to [I2CP]_, or as a new protocol.
@@ -30,10 +31,10 @@ router independently; the router that gets used by clients at any particular
time is the last one to publish a [LeaseSet]_.
This is a hack and presumably won't work for large websites at scale. Say we had
100 multihoming routers (edges) each with 16 tunnels. That's 1600 LeaseSet
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.
100 multihoming routers each with 16 tunnels. That's 1600 LeaseSet 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.
[Prop123]_ solves this problem with a meta-LeaseSet, which lists the 100 real
LeaseSet hashes. A lookup becomes a two-stage process: first looking up the
@@ -41,45 +42,126 @@ meta-LeaseSet, and then one of the named LeaseSets. This is a good solution to
the lookup traffic issue, but on its own it creates a significant privacy leak:
It is possible to determine which multihoming routers are online by monitoring
the published meta-LeaseSet, because each real LeaseSet has corresponds to a
single edge.
single router.
We need a way for an I2P client or service to spread a single Destination across
multiple edge routers, in a way that is indistinguishable to using a single
router (from the perspective of the LeaseSet itself).
multiple routers, in a way that is indistinguishable to using a single router
(from the perspective of the LeaseSet itself).
Design
======
Definitions
-----------
User
The person or organisation wanting to multihome their Destination(s). A
single Destination is considered here without loss of generality (WLOG).
Client
The application or service running behind the Destination. It may be a
client-side, server-side, or peer-to-peer application; we refer to it as
a client in the sense that it connects to the I2P routers.
The client consists of three parts, which may all be in the same process
or may be split across processes or machines (in a multi-client setup):
Balancer
The part of the client that manages peer selection and tunnel
building. There is a single balancer at any one time, and it
communicates with all I2P routers. There may be failover balancers.
Frontend
The part of the client that can be operated in parallel. Each
frontend communicates with a single I2P router.
Backend
The part of the client that is shared between all frontends. It has
no direct communication with any I2P router.
Router
An I2P router run by the user that sits at the boundary between the I2P
network and the user's network (akin to an edge device in corporate
networks). It builds tunnels under the command of a balancer, and routes
packets for a client or frontend.
High-level overview
-------------------
Imagine the following desired configuration:
- A client application with one Destination.
- Four edge routers, each managing three inbound tunnels.
- Four routers, each managing three inbound tunnels.
- All twelve tunnels should be published in a single LeaseSet.
Single-client
`````````````
.. raw:: html
{% highlight lang='text' %}
-{ [Tunnel 1]===\
|-{ [Tunnel 2]====[Edge Router 1]-----
|-{ [Tunnel 3]===/ \
| \
|-{ [Tunnel 4]===\ \
[Destination] |-{ [Tunnel 5]====[Edge Router 2]----- \
\ |-{ [Tunnel 6]===/ \ \
[LeaseSet]--| [Client]
|-{ [Tunnel 7]===\ / /
|-{ [Tunnel 8]====[Edge Router 3]----- /
|-{ [Tunnel 9]===/ /
| /
|-{ [Tunnel 10]==\ /
|-{ [Tunnel 11]===[Edge Router 4]-----
|-{ [Tunnel 2]====[Router 1]-----
|-{ [Tunnel 3]===/ \
| \
|-{ [Tunnel 4]===\ \
[Destination] |-{ [Tunnel 5]====[Router 2]----- \
\ |-{ [Tunnel 6]===/ \ \
[LeaseSet]--| [Client]
|-{ [Tunnel 7]===\ / /
|-{ [Tunnel 8]====[Router 3]----- /
|-{ [Tunnel 9]===/ /
| /
|-{ [Tunnel 10]==\ /
|-{ [Tunnel 11]===[Router 4]-----
-{ [Tunnel 12]==/
{% endhighlight %}
Multi-client
````````````
.. raw:: html
{% highlight lang='text' %}
-{ [Tunnel 1]===\
|-{ [Tunnel 2]====[Router 1]---------[Frontend 1]
|-{ [Tunnel 3]===/ \ \
| \ \
|-{ [Tunnel 4]===\ \ \
[Destination] |-{ [Tunnel 5]====[Router 2]---\-----[Frontend 2] \
\ |-{ [Tunnel 6]===/ \ \ \ \
[LeaseSet]--| [Balancer] [Backend]
|-{ [Tunnel 7]===\ / / / /
|-{ [Tunnel 8]====[Router 3]---/-----[Frontend 3] /
|-{ [Tunnel 9]===/ / /
| / /
|-{ [Tunnel 10]==\ / /
|-{ [Tunnel 11]===[Router 4]---------[Frontend 4]
-{ [Tunnel 12]==/
{% endhighlight %}
General client process
``````````````````````
- Load or generate a Destination.
- Open up a session with each router, tied to the Destination.
- Periodically (around every ten minutes, but more or less based on tunnel
liveness):
- Obtain the fast tier from each router.
- Use the superset of peers to build tunnels to/from each router.
- By default, tunnels to/from a particular router will use peers from
that router's fast tier, but this is not enforced by the protocol.
- Collect the set of active inbound tunnels from all active routers, and create a
LeaseSet.
- Publish the LeaseSet through one or more of the routers.
Differences to I2CP
```````````````````
To create and manage this configuration, the client needs the following new
functionality beyond what is currently provided by [I2CP]_:
@@ -93,34 +175,13 @@ in how the client manages its tunnels:
- Tell a router to build an inbound or outbound tunnel using a given list of
peers.
General client process
``````````````````````
- Load or generate a Destination.
- Open up a session with each edge router, tied to the Destination.
- Periodically (around every ten minutes, but more or less based on tunnel
liveness):
- Obtain the fast tier from each edge.
- Use the superset of peers to build tunnels to/from each edge.
- By default, tunnels to/from a particular edge router will use peers from
that router's fast tier, but this is not enforced by the protocol.
- Collect the set of active inbound tunnels from all active edges, and create a
LeaseSet.
- Publish the LeaseSet through one or more of the edges.
Protocol outline
----------------
.. raw:: html
{% highlight %}
Client Edge Router
Client Router
---------------------> Create Session
Session Status <---------------------
@@ -186,10 +247,10 @@ Messages
Security implications
=====================
From the perspective of the edge routers, this design is functionally equivalent
to the status quo. The edge router still builds all tunnels, maintains its own
peer profiles, and enforces separation between router and client operations. In
the default configuration is completely identical, because tunnels for that edge
From the perspective of the routers, this design is functionally equivalent to
the status quo. The router still builds all tunnels, maintains its own peer
profiles, and enforces separation between router and client operations. In the
default configuration is completely identical, because tunnels for that router
are built from its own fast tier.
From the perspective of the netDB, a single LeaseSet created via this protocol
@@ -217,13 +278,14 @@ observer to determine that the LeaseSet is multihomed:
- In a single-homed setup, a full 16-tunnel LeaseSet would have 16 IBGWs
randomly selected from a set of up to (say) 20 peers.
- In a 4-edge multihomed setup using the default configuration, a full 16-tunnel
LeaseSet would have 16 IBGWs randomly-selected from a set of at most 80 peers,
though there are likely to be a fraction of common peers between edge nodes.
- In a 4-router multihomed setup using the default configuration, a full
16-tunnel LeaseSet would have 16 IBGWs randomly-selected from a set of at most
80 peers, though there are likely to be a fraction of common peers between
routers.
Thus with the default configuration, it may be possible through statistical
analysis to figure out that a LeaseSet is being generated by this protocol. It
might also be possible to figure out how many edge nodes there are, although the
might also be possible to figure out how many routers there are, although the
effect of churn on the fast tiers would reduce the effectiveness of this
analysis.
@@ -236,9 +298,9 @@ Compatibility
=============
This design is completely backwards-compatible with the network, because there
are no changes to the [LeaseSet]_ format. All edge routers would need to be
aware of the new protocol, but this is not a concern as they would all be
controlled by the same entity.
are no changes to the [LeaseSet]_ format. All routers would need to be aware of
the new protocol, but this is not a concern as they would all be controlled by
the same entity.
Performance and scalability notes
@@ -255,8 +317,8 @@ modifications:
underlying transports, and is therefore around 16kB.
- Implement [Prop123]_ for tiered LeaseSets. In combination with this proposal,
the Destinations for the sub-LeaseSets could be spread across multiple edges,
effectively acting like multiple IP addresses for a clearnet service.
the Destinations for the sub-LeaseSets could be spread across multiple
routers, effectively acting like multiple IP addresses for a clearnet service.
Acknowledgements