Overall, I think the charter is good enough and we should ship it.
A few minor comments.
Many hosts have the ability to attach to multiple networks
simultaneously. This can happen over multiple physical network
interfaces, a combination of physical and virtual interfaces (VPNs or
tunnels), or even through multiple default routers being on the same
link.
Nit: this last point isn't really accurate. Having two routers on a
network doesn't mean one is attached to "multiple networks". The
"multiple" is at least one hop away in this case...
For instance, current laptops and smartphones typically have
multiple access network interfaces.
A host attached to multiple networks has to make decisions about default
router selection, address selection, DNS server selection, choice of
interface for packet transmission, and the treatment of configuration
information received from the various networks. Some configuration
objects are global to the node, some are local to the interface, and
some are related to a particular prefix. Various issues arise when
multiple configuration objects that are global to the node are received
on different interfaces.
Specifically, issues arise (only) when the information is in some
sense contradictory, forcing the host to make decisions about which
object to use under various circumstances. This is the root cause of
all the problems being discussed.
At best, decisions about these matters have an
efficiency effect. At worst, they have more significant effects such as
security impacts, or even lead to communication not being possible at all.
A number of operating systems have implemented various techniques to
deal with attachments to multiple networks. Some devices employ only one
interface at a time and some allow per-host configuration of preferences
between the interfaces but still use just one at a time. Other systems
allow per-application preferences or implement sophisticated policy
managers that can be configured by users or controlled externally.
The purpose of the MIF working group is to describe the issues of
attaching to multiple networks on hosts, document existing practice, and
make recommendations about best current practice.
Charter does seem to say here that BCP documents will be an
output. That goes beyond just describing the problem.
Personally, I'm skeptical that there is much in this space being done
today that would qualify as a BCP recommendation.
But that is something that we can figure out definitively when the WG
tries to produce such a document and we see what they are actually
recommending. So, as long as it is clear that one possible outcome is
that no BCP is possible at the current time, I'm OK with going
forward.
Thomas
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