Network-Based Mobility Extensions
Network-Based Mobility Extensions WG
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Proxy Mobile IPv6, specified in RFC 5213, is a network-based mobility
protocol. It uses a Mobile Access Gateway (MAG) and a Local Mobility
Anchor (LMA) to allow hosts to move around within a domain while keeping
their address or address prefix stable. Proxy Mobile IPv6 has been
incorporated into a number of products and deployments are starting.
Certain deployment considerations, including localized routing and bulk
refresh of lifetime are already emerging.
The working group will focus on the following topics relevant for
Localized Routing: a specification for routing traffic between the
MAG(s) without involving the LMA. That is, allow the MAGs to route
traffic between hosts from one MAG to another, without being tunneled
all the way to the LMA. This reduces latency and backhaul load.
Applications such as voice can benefit from the reduced latency.
The working group will produce a problem statement and a
specification of the localized routing mechanism.
Bulk Refresh: a specification of improving the signaling load for
binding lifetime refresh. The current specifications call for the
handling of each mobility session independent of each other. When a
large number of hosts are served by a single MAG, a periodic refresh of
the binding lifetimes can lead to a signaling storm. The purpose of the
Bulk Refresh feature is to construct a protocol feature that allows such
refreshes to occur on a per-MAG basis.
LMA Redirection: a specification for allowing an LMA to redirect a MAG
to another LMA. This is primarily needed as a way to perform load
balancing. This functionality is complementary to implementation
techniques that allow distributed MAG implementations to move tasks
around without a visible impact at the protocol level, and the
initial LMA discovery work in the NETLMM WG. An applicability statement
describing the situations where the new functionality is or is not
applicable has to be included in the specification.
Hiding access technology changes from host IP layer: Proxy mobility is
based on the assumption that changes in host IP stacks are
undesirable. However, link layer implementations can hide the
actually used physical interfaces from the IP stack. For instance, a
"logical interface" at the IP layer may enable packet transmission and
reception over different physical media. Such techniques can be used
to achieve inter-access handovers or flow mobility, i.e., the movement
of selected flows from one access technology to another. It is
assumed that an IP layer interface can simultaneously and/or
sequentially attach to multiple MAGs (possibly over multiple media).
The hiding mechanisms also need to work together with existing RFC
5213 handover hint mechanisms. The specification of any actual link
layer mechanisms is outside the scope of the working group, but the
group works on the following:
- Informational applicability statement that analyzes the issues
involved with this approach and characterizes the contexts in which
such use is or is not appropriate.
- The working group will determine what protocol extensions are
required between the Proxy Mobile IPv6 network nodes (MAGs and LMAs)
to support the ability for an interface (at the IP layer) to
transmit packets over different media, the ability to distribute
specific traffic flows on different media components of that
interface, and making this work with the handover hints in the base
protocol. The relevant protocol extensions will be developed as
Radius Extensions to PMIP6: In order to enable network based
mobility using PMIP6, the policy profile needs to signal a set of
attributes and policies to the MAG and LMA. New Radius attributes
need to be specified that are relevant to PMIP6 based
mobility. This work item will specify Radius extensions and
attributes specific to PMIP6.
The work in this charter is entirely internal to the network and does
not affect host IP stack operation in any way (except perhaps through
impacting packet forwarding capacity visible to the hosts). The working
group is not allowed to specify new IP layer protocol mechanisms to
signal mobility related events between the host and the network.
The proposed activity will be complementary to the existing IETF Working
Groups, notably the NETLMM and MEXT WGs. The NETEXT working group will
also act as the primary forum where new extensions on top of the Proxy
Mobile IPv6 protocol can be developed. The addition of such new
extensions to the working group involves addition of the extension to
this charter through the normal rechartering process.