Multiplex communications – Communication over free space – Portable address responsive receiver
Reexamination Certificate
2000-06-05
2003-04-15
Kizou, Hassan (Department: 2662)
Multiplex communications
Communication over free space
Portable address responsive receiver
C370S389000, C370S400000, C709S239000
Reexamination Certificate
active
06549522
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to the routing of data within communications networks, including but not confined to networks such as the Internet, and particularly, but not exclusively, to a method of routing data directed to a mobile node. The mobile node may be a mobile host, such as a portable computer, or it may be a router which is responsible for the mobility of one or more entire networks, for example, the mobile data network within an aircraft. In either case, the mobile node may change its point of attachment from one network or subnetwork to another.
Background
The routing of data around the diverse networks which make up the Internet is based on a protocol known as the Internet Protocol (IP). Data is transferred in the form of data units known as IP datagrams between points in the Internet specified by IP addresses. The use of IP hides the physical nature of the underlying networks from application processes running over the Internet. These networks may, for example, be a combination of wired and wireless local and wide area networks using different physical protocols such as Ethernet and token-ring, including networks linked by telephone through an Internet Service Provider (ISP), or through satellite or ground based radio or infrared links.
The detailed specification of IP is available in a “Request for Comments” document, RFC 791, maintained by the Internet Engineering Task Force (IETF). RFC documents are widely available on the Internet at, for example, “ftp://ds.internic.net/rfc/rfcxxxx.txt”, where “xxxx” represents the RFC number, so that RFC 791 is available as rfc791.txt.
The current version of IP, known as IPv4, does not itself support mobility, but a protocol entitled “IP Mobility Support”, commonly referred to as Mobile IP, has been designed to enhance IPv4 to support mobility. This protocol is described in document RFC 2002, available as detailed above. The use of Mobile IP to provide wireless network access for mobile computing users is described in “Wireless Network Extension Using Mobile IP”, Digest of Papers of Compcon (Computer Society Conference) 1996, Technologies for the Information Superhighway Santa Clara, Feb. 25-28 1996, no. Conf. 41, Feb. 25, 1996, pages 9-14, XP000628459 Institute of Electrical and Electronics Engineers. The next generation of IP (IPv6) is being specifically designed to deal with the mobility requirement.
IPv4 assumes that a node's IP address uniquely identifies the node's fixed point of attachment to the Internet. If the node is transferred to a different point, it can only be contacted by allocating it a new IP address. Mobile IP, however, enables a mobile node, such as a laptop or palmtop computer, to send and receive IP datagrams over the Internet regardless of the physical location at which it is connected to the Internet and without changing its IP address; One example of the mechanism by which it does so is illustrated in
FIGS. 1
a
and
1
b.
Referring to
FIG. 1
a
, the Internet comprises a large number of networks and sub-networks
1
,
2
,
3
,
4
connected via routers
5
. A router may be a general purpose computer programmed to perform routing tasks. Increasingly, routers throughout the Internet are dedicated pieces of hardware, controlled by software or firmware, provided by companies such as Cisco Systems, California, USA. In either case, the functionality of a router intended for use in an IP based network is defined in RFC 1812.
A mobile node (MN)
6
is normally connected to the Internet via a home network
1
. The unique IP address assigned to the node
6
is known as its home address. Mobility agents, known as foreign agents (FA) and home agents (HA), advertise their presence on a network via availability messages known as Agent Advertisements. A mobility agent is typically a router connected to a particular network; for example, a home agent
7
is a router connected to the home network
1
and a foreign agent
8
is a router connected to a foreign network
2
. The mobile node
6
may optionally solicit an Agent Advertisement message from, any local mobility agents via an Agent Solicitation message. By receiving Agent Advertisements, the mobile node
6
is able to determine whether it is on its home network
1
or on a foreign network
2
,
3
,
4
.
While the mobile node
6
is on its home network, it has no need for mobility services. When the mobile node
6
is temporarily moved to a foreign network
2
, as shown by the dotted box in
FIG. 1
a
, it obtains a temporary care-of address on the foreign network
2
. This can be a foreign agent care-of address, which is the IP address of the foreign agent, obtained by receiving or soliciting Agent Advertisements from any foreign agents based on the foreign network
2
. Alternatively, the care-of address may be obtained by using an external assignment mechanism, such as Dynamic Host Configuration Protocol (DHCP) (the reader is referred to RFC 1541 for further information), in which case it is known as a co-located care-of address.
The mobile node
6
then registers its new care-of address with its home agent
7
by exchanging Registration Request and Registration Reply messages with it. Registration provides a mechanism by which mobile nodes can communicate their current reachability information to their home agent. The registration process is described in more detail below, assuming that the mobile node
6
on the foreign network
2
is registering a foreign agent care-of address received via an Agent Advertisement from, for example, foreign agent
8
.
First, the mobile node
6
sends a Registration Request message to the foreign agent
8
, which processes it and forwards it to the mobile node's home agent
7
. The Registration Request message includes the IP address of the foreign agent. The home agent
7
sends a Registration Reply message to the foreign agent
8
granting (or denying) the registration request. The foreign agent
8
processes this Reply and forwards it to the mobile node
6
. This process establishes a temporary address for the mobile node
6
to which datagrams can be delivered while the node is roaming away from its home network
1
.
If the mobile node
6
is returning to its home network
1
having been on a foreign network
2
, it deregisters with its home agent
7
, through exchange of Registration Request and Registration Reply messages.
Referring to
FIG. 1
b
, when a correspondent node (CN)
9
attached to a network
4
sends a message intended for the mobile node
6
, while it is connected to the foreign network
2
, the message is intercepted by the home agent
7
, as shown by arrow A. The home agent
7
encapsulates the datagrams forming the message with the care-of address for the mobile node
6
, in this example being the IP address of the foreign agent
8
, and forwards the message to the foreign agent
8
. The transmission of the encapsulated datagrams, shown by arrow B, is known as tunnelling. The foreign agent
8
receives the datagrams, decapsulates them and forwards them to the mobile node
6
, as shown by arrow C. Messages from the mobile node
6
to other nodes in the Internet need not follow this route, but may be sent directly via an appropriate router, which may be foreign agent
8
.
The concepts of encapsulation and tunnelling are described in detail in RFC 2003, “IP Encapsulation within IP”. The model is that a tunnel is the path followed by a datagram while encapsulated. Encapsulation allows an IP datagram to be hidden from intermediate routers which would incorrectly attempt to route it to the mobile node. Instead, the datagram is routed between the encapsulator and a knowledgeable decapsulator, such as a foreign agent, which can correctly route the datagram. The home agent
7
and foreign agent
8
are known as the endpoints of the tunnel. In the case of the co-located care-of address, the mobile node itself acts as an endpoint of the tunnel.
To enable the tunnelling process described above to function correctly, the home agent
7
maintains r
British Telecommunications public limited Company
Kizou Hassan
Ly Anh-Vu H
Nixon & Vanderhye P.C.
LandOfFree
Mobile data rate enhancement via foreign agent load balancing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mobile data rate enhancement via foreign agent load balancing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mobile data rate enhancement via foreign agent load balancing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3027196