Address Selection Policies
Massar Networking
Swiss Post Box 101811
Zuercherstrasse 161
Zürich
CH-8010
CH
jeroen@massar.ch
http://jeroen.massar.ch
Internet
IPv6 Maintenance
IPv6
MTU
Header
PMTUD
ICMPv6
blackhole
latency
This document defines a hierarchical Address Selection Policy
distribution mechanism that is useful for multihomed networks
that have the need to provide to clients the details for
selecting proper source addresses for routing their packets
outbound based on policies defined by a central network
administration.
Using a new Router Advertisement option and a DHCPv6 option the URL of a HTTP server is disclosed
that contains the Address Selection Policy (ASP) of that network.
The ASP can be as simple as:
- 'two uplinks, use them randomly' or
- 'always use this address, otherwise fall back on this'
to more complex setups like:
- 'When sending packets to X use source Y'
- 'When wanting high speed use source Z'
- 'When wanting low priority use source G'
The destination is included in the data to be able to do selection based on destination address too.
(eg special properties for a route to a certain organisation)
We express each match as a route (source + destination). Both Source and Destination can be a prefix,
including the any (::/0 or 0.0.0.0/0) prefixes.
Matching of prefixes is done using a prefix tree style construct so tha the most-specific wins.
Address selection is related to GAI in that it orders addresses. A tool might still fail over to
alternative addresses, which is useful for the backup case.
- Priority
Priority causes one policy to be chosen over another
A Priority of 0
- Weight
A simple form of load-balancing can be caused using this
A node that is able to provide a fake address selection policy to hosts might cause disruption
or unwanted behavior.
Proper enforcement of access to the local network and which nodes can act as Router Advertisement
servers or DHCPv6 servers is thus required.