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Multiple Interfaces
charter-ietf-mif-03-00

The information below is for an older proposed charter
Document Proposed charter Multiple Interfaces WG (mif) Snapshot
Title Multiple Interfaces
Last updated 2013-10-13
State Draft Charter
WG State Active
IESG Responsible AD Terry Manderson
Charter edit AD (None)
Send notices to (None)

charter-ietf-mif-03-00

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 indirectly through multiple default routers and/or
address prefixes being on the same link. 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
contradictory configuration objects that are global to the node are
received on different interfaces. 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 and document existing practice.
The group shall also analyze the impacts and effectiveness of these
existing mechanisms. The WG shall employ and refer to existing IETF work
in this area, including, for instance, strong/weak models (RFC 1122),
address selection (RFC 3484), ICE and other mechanisms higher layers can
use for address selection, DHCP mechanisms, Router Advertisement
mechanisms, and DNS recommendations. The focus of the working group
should be on documenting the system level effects to host IP stacks and
identification of gaps between the existing IETF recommendations and
existing practice. After completing some of its initial goals in 2010 the
group is also developing three specific extensions:

1) Architecture document, defining consistent approach, recommended practices
and requirements for possible protocol changes to improve handling of multiple sets of network configuration objects in networks and nodes.

2) MIF API: While no changes are required for applications to run on
multiple interface hosts, a new API could provide additional services
to applications running on hosts attached to multiple provisioning
domains. For instance, these services could assist advanced
applications in having greater control over first-hop, source address
and/or DNS selection, interface and other network configuration
elements selection. This API will be defined as an abstract interface
specification, i.e., specific details about mapping to operating
system primitives or programming language will be left out.

Network discovery and selection on lower layers as defined by RFC 5113
is out of scope. With the exception of identifying requirements for
additional DHCP and/or ND options as well as requirements for possible
related changes in these protocols, group shall not assume any
software beyond basic IP protocol support on its peers or in network
nodes. No work will be done to enable traffic flows to move from one
interface to another. The group recognizes existing work on mechanisms
that require peer or network support for moving traffic flows such as
RFC 5206, RFC 4980 and the use of multiple care-of addresses in Mobile
IPv6. This group does not work on or impact such mechanisms.

Future work in this area requires rechartering the working group or
asking other, specialized working groups (such as DHC or 6MAN) to deal
with specific issues.