Technical data

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This site lists Internet-Drafts documents, all of which are works in
progress and subject to change at any time.
The Internet Protocol Version 6 (IPv6) was designed to support mobility through
features like its extensible header structure, address autoconfiguration, security
(IPsec) and tunneling. mobile IPv6 builds upon these features.
In a mobile IPv6 environment, nodes can have the following roles:
• Mobile node, which is a host or router that can change its point of attachment
from one link to another while still being reachable through its home address.
• Correspondent node, which is a peer node with which a mobile node is
communicating. The correspondent node (host or router) can be either mobile
or stationary.
• Home agent, which is a router on a mobile node’s home link with which the
mobile node registers its current care-of address. (Currently, OpenVMS cannot
operate as a home agent).
A mobile node on its home link has a home address. The subnet prefix of
this address is the home network’s subnet prefix. The mobile node is always
addressable by its home address.
When the mobile node is away from home, on a foreign link, it acquires a care-of
address. The subnet prefix of this address is the foreign network’s subnet prefix. A
mobile node can have multiple care-of addresses, the care-of address registered
with the mobile node’s home agent is called its primary care-of address.
The association of the mobile node’s home address with its care-of address is
called a binding. This association has a lifetime. Each node maintains a cache of
all bindings.
When the mobile node is on its home link, packets from the correspondent node
that are addressed to the mobile node’s home address are delivered through
standard IP routing mechanisms.
When the mobile node is on a foreign link, it configures a care-of address and
registers it with its home agent by sending the home agent a binding update.
Packets sent by a correspondent node to the mobile node’s home address arrive
at its home link. The home agent intercepts the packets, encapsulates them, and
tunnels them to the mobile node ’s registered care-of address.
After the mobile node receives the tunneled packets, the mobile node assumes that
the original sending correspondent node has no binding cache entry for the mobile
node care-of address, otherwise the correspondent node sends the packet directly to
the mobile node using a routing header.
The mobile node then sends a binding update to the correspondent node. The
correspondent node creates a binding between the home address and care-of
address.
Packets flow directly between the correspondent node and mobile node. This
route optimization eliminates what is commonly known as triangle routing.or
congestion at the mobile node’s home agent and home link. It also reduces the
impact of any possible failure of the home agent, the home link, or intervening
networks leading to or from the home link, since these nodes and links are not
involved in the delivery of most packets to the mobile node.
9–2 IPv6