Active link layer and intra-domain mobility for IP networks

Details Active link layer and intra-domain mobility for IP networks Active link layer and intra-domain mobility for IP networks

2000-02-24

2002-12-03

Nguyen, Chau (Department: 2663)

Multiplex communications

Communication over free space

Having a plurality of contiguous regions served by...

C370S338000, C455S436000

Reexamination Certificate

active

06490259

ABSTRACT:

BACKGROUND OF THE DISCLOSURE
1. Field of the Invention
This invention relates generally to mobile communications, and, more particularly, to methodologies and concomitant circuitry for applying active networking to manage the mobility of IP (Internet Protocol) networks.
2. Description of the Background
The Internet is expected to see continued growth in supporting personal and commercial services. Currently the Internet Protocol (IP) provides services to end terminals that are attached to wired networks. With the proliferation of mobile and wireless services and as more users disconnect from their fixed access points and become mobile, there is an increasing need to adapt IP to the wireless domain.
The wireless environment is dynamic in nature due to the mobility of the end terminals and the variability of the over-the-air channel. Moreover, the mobile wireless environment is much more dynamic than the traditional wireline environment. The uncertainties of the wireless and mobile environments call for an increased level of adaptability. For more robust communications, mobility management must maintain connectivity when the mobile terminal is moving and/or the transmission capabilities are varying. Successful installation of real-time and non-real-time applications across network elements with differing capabilities and over a dynamic wireless channel requires mobility management to have flexible and self-adaptive functionality.
The IP network was originally designed without considering the possibility that devices such as mobile terminals may move from one place to another. Thus, the IP address of a mobile terminal represents both the “identification” and “location” of a terminal. The IP address specifies to which network and subnet the terminal can attach. This address, expressed in terms of the Open Systems Interconnection layer model, is used in the network layer (also referred to as the IP layer, or layer
3
) to find the terminal and to route packets to the terminal. The assumption, however, breaks in today's highly mobile environment, in which the identification and location of terminals must be decoupled.
Ideally, mobility management can be done in any layer. However the network layer is a more natural place to deal with IP mobility because it is the layer where packets are routed. Currently, mobility in IP networks is supported by the Mobile IP protocol. Mobile IP identifies a mobile terminal (MT) by its permanent home IP address, regardless of its current point of attachment in the communication system such as, for example, the Internet. While away from its home network, the MT acquires a “care-of” address—an address that reflects its current point of attachment—from an agent, which is referred to as a “foreign agent”. The care-of address can also be acquired by other means, such as a DHCP server. The MT then provides to its “home agent” in the home network the “care-of” address. Mobile IP uses the home agent to redirect (by encapsulation) packets destined for the home address to the “care-of” address. By this way, all IP packets sent to the mobile station (MT) will be received by home agent, which then forwards them to foreign agent or to the MT directly. Mobile IP hides the change of IP address and therefore the change of the MT's location. Higher layers do not need to know the location of the MT and can continue to use the same IP address to reach the MT.
Mobile IP is a simple and scalable way to deal with the mobility in network layer. However, the redirection by the home agent causes Mobile IP to be inefficient (triangular routing) and not robust (relies on a home agent and sometimes on a foreign agent). To deal with the triangular routing problem, mobility support in IPv
6
has moved in the direction of end-to-end location updates using the facilities of IPv
6
to send binding updates. In addition to sending its binding to its home agent, the MT can send the binding to the corresponding host communicating with it. When sending a packet, the corresponding host checks its binding for the destination address. The packet is then sent directly to the care-of address without going through the home agent if the binding is found. This improves routing efficiency. However, this still requires communications via the home agent when the corresponding host does not know the current location of the MT, or when both nodes can be mobile simultaneously, or if the MT wants to hide its location. More important, IPv
6
is not widely deployed currently.
Although Mobile IP is simple, scalable, and suitable for inter-domain mobility, it is now realized that Mobile IP may not be suitable for “intra-domain” mobility, especially when a MT moves frequently. As indicated above, Mobile IP is inefficient due to triangular routing. In addition, the registration of care-of address with the home agent when the MT moves to a new subnet will cause too many messages if the MT moves frequently between subnets. This registration from the MT to the home agent causes extra delay too. Besides, the IP network relies on ARP (address resolution protocol) to map the IP address to the MAC address (that is, the layer
2
or link layer address). The broadcast-and-reply nature of ARP wastes bandwidth and causes extra delay. Although cache memory can reduce the use of ARP, it is somewhat ineffective when the MT moves frequently. Moreover, all of the problems related to a roving mobile terminal outlined above are exaggerated for real-time services that require very fast handoff.
Active networks are a class of networks that can be leveraged to provide mobility management adaptability. An active network allows intermediate nodes to perform computations specified by packets or modify in-transit packets. This technique allows programs to be executed or structures to be reconfigured in the network based on the data contained in the packets traversing the network. Thus, this technique injects a degree of intelligence and flexibility into current network elements that can be configured and programmed to suit a variety of needs. Moreover, this type of processing can be customized on a per-user or per-application basis.
A recent disclosure relating to active networks is the subject matter of U.S. Pat. No. 5,949,780 issued to Gopinath. The subject matter of this patent relates to methodologies and concomitant circuitry for coalescing intelligence with communications in a switching node. The inventive aspects of '780 suggestions related to program execution in the switch based upon the following actions/events (an event triggers an action which, in turn, generates a desired response): the state of the program itself; the state of resources composing the switch; external control inputs serving the switch; other programs executing in the switch; data (packets) received over other ports of the switch; or combinations of these actions/events. In addition, the inventive aspects covered an implementation in conjunction with a switch wherein a new program may be downloaded to the switch, and then this new program may be executed, together with other stored programs if necessary, based upon data incoming to a port as well as any or all the foregoing actions/events.
In accordance with the broad method aspect of '780, a communications service is implemented with a program stored in a processing unit having input and output ports to receive and transmit messages—each message is composed of, canonically, a control tag and payload information. For each port, data is retrieved and then parsed by the program to determine if the control tag and/or the payload information are to be modified. Based upon the parsing, the incoming message can be sent to one or more other ports, or further processed by the program or other stored programs to produce desired actions.
The prior art is devoid of teachings or suggestions relating to generating an active packet to foster the fast handoff of a mobile terminal as the terminal moves from one cell to another in a subnet, and from a subnet to another subnet within an administrative

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