On Saturday 18 April 2009 12:25:17 ext Jari Arkko wrote:
When the work started, it was clearly about multiple interfaces. Upon
closer inspection, we have realized that the overall problem is somewhat
larger. Problems that occur with multiple interfaces also occur even
with one interface, when you have a number of default routers on the
same link. The current charter text reflects this in some parts of the
text, e.g.,
I don't quite agree here.
Multiple interfaces will typically have some differing properties, such as:
- bandwidth,
- latency,
- charging,
- power consumption,
- reliability,
- address transparency (e.g. what kind of NAT if any)
- filtering policy,
- IP protocol versions availability,
- set of reachable hosts (the Internet, the home, the office...),
- recursive DNS servers,
- DNS namespace,
- address filtering rules.
A host may have multiple default gateways on the same "interface". However,
those gateways should be usable interchangeably. All of those gateways should
have the same "values" for the properties above. Otherwise, I would argue the
network is broken and/or the host is misconfigured. In other words, it can
pick any of its live gateways outbound, and may receive packets from any of
those gateways in the other direction. If I'm not mistaken, the IETF IPv6
wireless network is an example of this.
But I think /that/ form of multi-homing has been solved for a long time by Ip
stack implementors. What was discussed at the MIF BoF were quite different
scenarios.
--
Rémi Denis-Courmont
Nokia Devices R&D, Maemo Software, Helsinki
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