Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-06-02
2003-05-20
Hunter, Daniel (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S432300, C455S403000, C455S433000
Reexamination Certificate
active
06567664
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to methods for registering and re-registering mobile nodes with their home network while roaming in a foreign network.
A mobile node is a terminal which is able to change its point of connection to a packet data network, which includes, but is not limited to, the Internet, from one network or sub-network to another. For the sake of the present discussion, all references to the Internet which follow in this specification will be presumed to include all other packet data networks.
Mobile Internet Protocol (Mobile IP) allows mobile nodes to roam from network to network or move from place to place within a network while maintaining communication with the Internet and maintaining identification of the mobile node by its individual home address, regardless of the mobile node's current connection to the Internet. Mobile IP is described in the work-in-progress by Perkins et al. in “IP Mobility Support”, IETF Mobile IP Working Group, RFC 2002, 1996, and is herein incorporated by reference.
Using the known IPv4 protocol shown in
FIG. 1
, when a mobile node
1
has determined that it has roamed into a foreign network, that is, any network that is not the home network of the mobile node, the mobile node must register itself on the foreign network in order to establish and maintain a connection to the Internet via the home network of the mobile node. Such registration is limited in duration and registration may be performed repeatedly. In other words, registration enables the mobile node which is roaming on a foreign network to receive all data packets addressed to the mobile node's individual Internet home address on its respective home network. Accordingly, the mobile node can always be reached at its home address, regardless of the foreign network that it is located in. Furthermore, the mobile node must re-register itself in the foreign network if the duration of the mobile node's stay in the foreign network exceeds the duration of the validity of the original registration.
In
FIG. 1
, first a foreign agent
3
, which is a router on the foreign network, periodically sends out messages indicating its availability for service on behalf of mobile nodes roaming thereon. These “agent advertisements” enable the mobile node to first determine if it is on its home network or on a foreign network. The “agent advertisements” further provide the mobile node with a “care of” address, which is a temporary address reflecting a roaming mobile node's current point of connection to the Internet, at which the mobile node can be reached if it is on a foreign network.
If the mobile node determines that it is roaming in a foreign network, based on information provided in the agent advertisement, the mobile node
1
sends a registration request, which includes the “care of” address, to the available foreign agent
3
which then forwards the registration request to the home agent
4
of the home network
5
of the mobile node. The home agent
4
sends a registration reply to the foreign agent
3
acknowledging the registration. By having the mobile node
1
register its current location in a foreign network with its home agent, the home agent
4
is able to create or modify a mobility binding (i.e., the association of the home address of the mobile node to the care-of address thereof) and therefore the mobile node
1
can receive data packets addressed to its individual home address which are forwarded by the home agent thereof. In IPv4, the registration request from the mobile node
1
and the registration reply from the home agent
4
are sent via User Datagram Protocol (UDP).
As a result of the mobile node's registration, the home agent
4
, which is a router on the mobile node's home network
5
, encapsulates data packets addressed to the mobile node's home network address in an IP tunnel directed to the care-of address provided by the mobile node. The foreign agent
3
receives the encapsulated IP packets, and forwards them to the mobile node
1
. Furthermore, it should be noted that the mobile node
1
uses its individual home address as the source address of all IP data packets that it sends, even when on the foreign network.
Mobile IP version IPv6, shown in
FIG. 2
, does not utilize a foreign agent to acquire “care-of addresses” for the mobile nodes
1
, unlike the case for IPv4. Rather, IPv6 has built-in mobility support and utilizes “co-located care-of addresses,” whereby the mobile nodes acquire the co-located care-of addresses themselves. Such methods for acquiring the co-located care-of addresses for IPv6 are described in the work-in-progress by Johnson et al. entitled “Mobility Support in IPv6” IETF Mobile IP Working Group, 1998, which also is incorporated herein by reference.
According to the IPv6 Mobile IP, a roaming mobile node
1
registers one of its co-located care-of addresses with a router on its home network
6
, requesting the router to function as the home agent
4
for the mobile node. This is accomplished when mobile node
1
performs “binding” registration which is the association of the mobile node's home address with its co-located care-of address by sending a data packet including a “binding update” destination option to the home agent
4
, to thereby make known the mobile node's primary care-of address to the home network. Acknowledgment of the binding update data packet is then forwarded from the home agent
4
to the mobile node
1
. The binding update data packet and acknowledgment thereof between the mobile node
1
and the home agent
4
is transmitted using Internet Control Message Protocol (ICMP). The home agent then uses proxy neighbor discovery to intercept IPv6 data packets addressed to the mobile node's home address on the home link and tunnels any intercepted packet to the mobile node's primary care-of address. The aforementioned proxy neighbor discovery is described in the Johnson reference.
A known format of the Mobile IP Registration Request sent from the mobile node to the foreign agent or to the home agent, as described above, is depicted in FIG.
3
. As described in RFC 2002, the Mobile IP fields Registration Request include the following fields, which are common for both IPv4 and IPv6 Mobile IP, except where noted:
Type: identification as a Registration Request;
S:
Simultaneous bindings. The mobile node is requesting that the home agent retain its prior mobility bindings;
B:
Broadcast datagrams. The mobile node is requesting that the home agent tunnel any broadcast data packets addressed to the mobile node's home network address to the mobile node at its care-of address;
D:
Decapsulation by the mobile node. The mobile node is indicating that it will decapsulate data packets that are sent to the care-of address itself, that is the mobile node is using a co-located care-of address (for IPv6);
M:
Minimal encapsulation. The mobile node is requesting that its home agent use minimal encapsulation for data packets tunneled to the mobile node;
G:
Encapsulation. The mobile node is requesting that its home agent use a specified standard of encapsulation for data packets tunneled to the mobile node;
V:
The mobile node is requesting that either the home agent or foreign agent use Van Jacobson header compression over the corresponding link with the mobile node;
rsv:
Reserved bits;
Lifetime:
The amount of time (in seconds) remaining for valid registration of the mobile node;
Home Address:
The IP address of the mobile node;
Home Agent:
The IP address of the mobile node's home agent;
Care-of Address:
The IP address for tunneling of data packets;
Identification:
A 64-bit number used for matching Registration Requests with Registration Replies, composed by the mobile node; and
Extension(s): The fixed portion of the Registration Request can be followed by one or more extensions. The extension mechanism allows optional information to be carried by Mobile IP control messages or by ICMP Router Discover messages. Extensions are encoded in a Type-Length-Valu
Bergenwall Martin
Ekberg Jan-Erik
Flykt Patrik
Haverinen Henry
Månsson Jani
Antonelli Terry Stout & Kraus LLP
Hunter Daniel
Le Lana
Nokia Corporation
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