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Detecting Network Attachment

Document Charter Detecting Network Attachment WG (dna)
Title Detecting Network Attachment
Last updated 2009-10-23
State Approved
WG State Concluded
IESG Responsible AD Jari Arkko
Charter edit AD (None)
Send notices to (None)

When an IPv6 node detects or suspects that its
   underlying link layer (L2) connectivity has or
   may have undergone a change, it needs to check
   whether its IP layer (L3) addressing and routing
   configurations are still valid or have changed.
   In the case that the L3 connectivity has changed,
   the node needs to reconfigure and may need to
   initiate mobility procedures, such as sending
   Mobile IP binding updates. Changes in an L2
   connection do not necessarily mean that
   there has been change in L3 connectivity.
   For the purposes of detecting network attachment,
   an L3 link is defined as the topological range
   within which IP packets may be sent without resorting to
   forwarding. In other words, a link is the
   range where a given IP configuration is valid.
   In IPv6, the IP layer configuration information
   includes the set of valid unicast addresses[RFC 2462,
   RFC 3315], the Duplicate Address Detection (DAD)
   status of the addresses[RFC 2462], valid routing
   prefixes[RFC 2461], set of default routers[RFC 2461],
   neighbor and destination caches[RFC 2461], multicast
   listener (MLD) state[RFC 2710]. The current IPv6
   stateless and stateful autoconfiguration procedures
   may take a fairly long time due to delays associated
   with Router Discovery and Duplicate Address Detection.
   The main goal of this WG is to develop mechanisms that
   reduce or avoid such delays, in cases where they are
   not necessary. For example if an interface comes back
   up after having been down momentarily, it can be
   quicker to verify that one is still attached to the
   same link than rerunning the full reconfiguration as
   if one were connecting to a new L3 link and had no
   previous configuration information cached.
   In some wireless technologies, the link layer state
   and events may not give an accurate indication of
   whether or not the IP addressing configuration and
   routability have changed. For example, a host may
   be able to see a base station but still be unable to
   deliver or receive IP packets within the L3 link.
   Moreover, a hardware indication that a radio link
   is up does not necessarily mean that all link layer
   configuration, such as authentication or virtual
   LAN connectivity has been completed. Therefore
   detecting network attachment requires not only
   change detection but IP layer connectivity testing.
   The purpose of the DNA working group is to define
   standards track and BCP documents that allow hosts
   to detect their IP layer configuration and
   connectivity status quickly, proposing some
   optimization to the current specifications that
   would allow a host to reconfigure its IPv6 layer
   faster than today.
   The group will define a set of goals for detecting
   network attachment, describing existing issues
   and important properties of potential solutions.
   The working group will describe best current practice
   for nodes making use of existing information
   for detecting network attachment.
   The working group will define a set of extensions to the
   current IPv6 configuration protocols [RFC 2461, 2462,
   possibly RFC 3315] that allow the nodes to
   discover whether L3 configuration or connectivity
   may have changed more reliably and easily than today.
   Initiation of L3 link change detection procedures can
   be achieved either through reception (or lack of
   reception) of messages at the IP layer or through
   indications from other layers. The working group
   will produce an informational document that
   contains a catalogue of the indications currently
   available from a subset of wireless link layer
   The DNA WG will not define new procedures or APIs
   related to link layers.
       * Define goals for detecting network attachment in IPv6
       * Specify recommendations for detecting network
             attachment and L3 link change in IPv6 networks (BCP).
       * Define a protocol extension for detecting network
           attachment and L3 link change in IPv6 networks
           more reliably and easily (Standards Track).
       * Document existing link layer (L2) information which is
           useful to start detecting network attachment