DNS based Destination Selection

[David Gethings <davidg@pipex.net>]

Hi,

I understand that DNS based solutions to the IPv6 multihomed problem
have been suggested before. However I believe my suggestion is a
different variant to previous suggestions.

Below is an overview of my suggestion. I believe it has merit and would
like the groups view.

Purpose
The purpose of this idea is to use DNS as a means for a multihomed site
to influence an external source's destination decision making. In that
way the multihomed site can influence which of its ingress points
traffic for a particular host will come in on.

Summary
Import MX priority values into AAAA and A6 records

Assumptions
That a multihomed site has a prefix provided by each transit provider

Description of Operation
A source wishes to get to a multihomed destination. When performing the
DNS look up the source gets all the IP addresses that resolve to that
hostname. Each IP address has a priority value attached to it (like MX
records).

If the source is compatible then the source used the IP address of the
most preferred priority value. It then establishes a connection to that
IP address.

Where a host is not compatible then standard address selection is
performed. In this instance the multihomed site preferrence (or policy)
cannot be enforced.

Where the source is compatible and receives multiple destination
addresses with the same priority the source may determine (but some yet
to be defined means) which IP address is preferred. The source then
establishes a connection to that IP address.

Problems
Security wise this should introduce no new problems. It is no less
secure than MX records
The question is, is DNS the right place to do this? If not why not?
Load balancing maybe a problem as it depends on implementation.
Most of the expense is put on the multihomed site: it must manage
multiple prefixes; manage the priority setting for hosts.

Advantages
Ensures the hierarchical nature of IPv6 stays intact
Does not require any IP address rewriting, tunnelling or encapsulation
Multihomed sites have a method of enforcing internal policy without
using complicated routing policies
The multihomed site does not require BGP routing

Requirements
The the DNS wg accept this idea and impliment.
That hosts IPv6 stack be updated to take this into account

Cheers

Dg