Method and apparatus for providing mobility within a network

ES 2 392 901 T3

DESCRIPTION

Procedure and apparatus for providing mobility within a network

Background of the invention

I. Field of the invention

The present invention relates to mobility within a telecommunications system. More particularly, the present invention relates to a method and apparatus for transparently relocating an anchor point within the serving network of a wireless telecommunications system from one location to another.

II. Description of Related Art

In the US patent application with serial number 09 / 158,047, filed by the applicant of the present invention and entitled "DISTRIBUTED INFRASTRUCTURE FOR WIRELESS DATA COMMUNICATIONS", it discloses the use of a decentralized server network for use in a system wireless telecommunications. The above application discloses a decentralized communication server network in which, instead of having a single control point, there are multiple control points distributed throughout the telecommunications system server network.

The Internet Engineering Working Group (IETF) is the standardization body that creates most of the standards related to Internet Protocol (IP). Many of the standards created by the IETF are called RFCs. RFC stands for “Request for Comments”.

The IETF standardized Open Shortest Path First (OSPF) to address, in part, the routing of packets in a network in which one or more of the routing devices experience failure, thus improving the reliability of a network . OSPF was designed in such a way that of all the routing devices that are operating at any given time, the shortest path is taken from node A to node B. Furthermore, OSPF was designed in such a way that if there are multiple equivalent routes from node A to node B, any one of the equivalent routes can be selected. With the implementation of OSPF, a network with redundant paths can carry out a balanced distribution of loads on the routing devices. OSPF is available on many makes and models of routing devices, and is described in IETF RFC 2328.

Mobile IP is present in many IETF standards to enable a device containing an IP address to roam a network (or networks). The RFC 2002 standard, "IP Mobility Support", addresses the problem of IP mobility and uses a solution called "Mobile IP". There are also several additional standards related to Mobile IP, such as RFCs 2006, 2041, 2290, 2344, and 2356. The IETF standards direct local area network (LAN) system administrators who want to support mobile IP use. Mobile IP provides support not only for mobility within a LAN, but also for mobility within a wide area network (WAN).

In a decentralized telecommunications network, the chosen service devices are widely available serial units that use open standards for their interface rather than proprietary protocols that are limited to a single vendor. Many, if not all, of the serving devices are designed to communicate with a single anchor point for each active session. This means that such serial devices and the protocols they incorporate are not designed to start a session with one device and end the same session with a different device. This restriction can lead to routing not optimized for individual sessions. Such non-optimized routing situations are illustrated in FIG. 8A and FIG. 8B. A method is needed whereby the anchor point of a service device can be relocated without the need for specific anchor point relocation support on the service device. Espe cally, such a procedure should be very efficient and robust, minimizing latency and bandwidth usage.

Attention is further drawn to international patent application WO 98/47302 A, which relates to a method for preventing packet loss in a handover in a packet-based telecommunications network and to a handover procedure. It discloses a connection-based packet-based communication network, such as ATM (asynchronous transfer mode), in which the terminal (MS) and the terminal's network access point can move in the network. When the terminal access point (MS) changes during an active connection, the routing of the connection must also be changed or extended from an old access point (BTS1) to a new one (BTS2). The old access point (BTS1) may comprise queued cells, which should be transferred to the new access point without packet loss. When required, a necessary connection is dynamically established from the old access point to the new one. Instead of being controlled by the old access point, the establishment of the connection is controlled by a third network element, which is responsible in any case for controlling the change of the access point. The third network element generates the required signaling and, in a certain way, "tunnels" this signaling to the old access point.

ES 2 392 901 T3 (BTS1), which transmits the signaling without interrupting it. Thus, the old access point can be arranged to send signaling messages and to establish a connection without requiring any additional intelligence at the access point. After the connection is established, the old access point forwards the unsent queued packets to the new access point (BTS2).

Attention is also drawn to the Valko AG paper, "Cellular IP: A New Approach to Internet Host Mobility", Computer Communications Review, US Association for Computing Machinery, New York, vol. 29, n ° 1, January 1999 (1999-01), pages 50-65, ISSN: 0146-4833. It unveils a new approach to Internet host mobility in which local and wide area mobilities are separated, in which it can significantly improve the performance of existing mobile host protocols (eg mobile IP). It proposes cellular IP, a new, lightweight and robust protocol that is optimized to support local mobility but efficiently interconnects with mobile IP to provide support for wide-area mobility. Cellular IP shows great benefit compared to existing host mobility proposals for environments where mobile hosts frequently migrate, which the inventors argue will be the rule, not the exception, as wireless Internet access become ubiquitous. Cellular IP maintains a distributed buffer for location management and routing purposes. The distributed notification buffer approximately maintains the position of the "idle" mobile hosts in a service area. Cellular IP uses this notification buffer to quickly and efficiently locate "idle" mobile hosts who wish to participate in "active" communications. This approach is beneficial because it can accommodate a large number of users attached to the network without overloading the location management system. The distributed routing buffer maintains the position of active mobile hosts in the service area and dynamically updates the routing status in response to the handover of active mobile hosts. These distributed location management and routing algorithms lend themselves to a simple, low-cost implementation of Internet host mobility that does not require any new packet formats, encapsulations, or address space allocation beyond what is present. on the IP.

Furthermore, Li and Leung's paper, "Protocol Architecture for Universal Personal Computing", IEEE Journal on Selected Areas in Communications, IEEE Inc., New York, USA, vol. 15, n ° 8, October 1, 1997, pages 1467-1476, ISSN: 0733-8716, unveils a new paradigm for networked computing on the Internet called personal computing, in which users can access computing resources , network services and customized computing environments anywhere using any available terminal. The user and system requirements are defined and an agent-based protocol architecture required to manage different mobile objects, ie, users and terminals, is presented in this computing environment. Modifications to the procedures for configuring connections between application programs are considered to allow addressing based on a global user identity. The use of personal agents is proposed to facilitate interconnection and management functions.

Summary of the invention

According to the present invention, a controlling entity operable in a communication system, as set forth in claim 1 and claim 4, and a method are provided for a controlling entity operable in a communication system to relocate an anchor point, as set forth in claim 8 and claim 11. Preferred embodiments of the invention are claimed in the dependent claims.

The present invention is a novel method and apparatus for providing transparent mobility of an entity within a serving network of a wireless telecommunications system. The invention enables the transparent mobility of a data anchor point within a network, allowing the anchor point to move from one physical location on the network to another physical location on the network. The type of mobility is called “transparent” because the peer entity communicating with the anchor point does not receive a message indicating that the anchor point has moved, nor is the peer required to carry out no special function to stay in communication with an anchor point that has been moved from one location to another. In other words, the peer entity that communicates with the data anchor point does not behave differently in a session in which the anchor point remains fixed than it behaves in a session in which the anchor point remains fixed. anchor point change physical location.

The present invention is applicable to decentralized networks where transparent mobility is desired. The present invention is particularly applicable in networks where it is desired that the mobility mechanism does not introduce latency or decrease the available bandwidth of the network. Such networks include, without limitation, a CDMA wireless data network and a GSM wireless data network.

All embodiments of the present invention are novel methods and apparatus for managing mobility within a server network of a wireless communication system. The exemplary embodiment of the present invention has a broader applicability, because it provides a novel method for mobility management in all types of networks, including corporate and state networks. Other models of

ES 2 392 901 T3 mobility may require a centralized network to manage anchor point mobility. Additionally, other mobility models can use a significant amount of available bandwidth and can significantly increase latency. The present invention has neither detrimental latency nor effects on bandwidth. In addition, the present invention uses standard protocols that are widely available from a plurality of equipment manufacturers on various platforms. Thus, the present invention provides a very cost-effective model for network providers wishing to support transparent mobility within their network.

The exemplary embodiment of the present invention uses OSPF to achieve transparent anchor point mobility. Mobile IP is used in an alternative embodiment of the present invention to provide transparent anchor point mobility in the serving network of a wireless communication system. OSPF is used in the exemplary embodiment of the present invention because the use of OSPF does not introduce the tunneling overhead that is introduced by mobile IP, and OSPF does not introduce the latency that can be caused by common indirect routing on the IP. mobile.

Brief description of the drawings

The features, objects, and advantages of the present invention will become more apparent from the detailed description presented below taken in conjunction with the drawings, in which similar reference characters identify corresponding parts from start to finish and in which:

FIG. 1 is a block diagram of an exemplary embodiment of an access terminal in communication with a decentralized wireless telecommunications server network;

FIG. 2 is a functional block diagram of an exemplary embodiment of a decentralized server network of a wireless telecommunications system;

FIG. 3 is a functional block diagram of an exemplary embodiment of an access point;

FIG. 4 is a functional block diagram of an exemplary embodiment of a modem bank controller;

FIG. 5 is a functional block diagram of an exemplary embodiment of a modem bank transceiver;

FIG. 6A is a network diagram of an exemplary embodiment of the data path from an access terminal to the Internet, in which the access terminal is in communication with a first transceiver of a bank of modems of a server network of an Internet service system. wireless telecommunications; FIG. 6B is a block diagram of the data path taken in connection with FIG. 6A;

FIG. 7A is a network diagram of an exemplary embodiment of the data path from an access terminal to the Internet, wherein the access terminal is in soft handoff with first and second transceivers of a bank of modems in a server network. a wireless telecommunications system;

FIG. 7B is a block diagram of the data path taken in connection with FIG. 7A;

FIG. 8A is a network diagram of an exemplary embodiment of the data path from an access terminal to the Internet, in which the access terminal is in communication with a second transceiver of a bank of modems of a server network of a network system. wireless telecommunications, and the handover of the anchor point of the present invention is yet to occur;

FIG. 8B is a block diagram of the data path taken in connection with FIG. 8A;

FIG. 9 is a flow chart illustrating an exemplary embodiment of the anchor point transfer methodology of the present invention;

FIG. 10A is a network diagram of an exemplary embodiment of the data path from an access terminal to the Internet, in which the access terminal is in communication with a second transceiver of a bank of modems of a server network of a network system. wireless telecommunications, and the anchor point handover methodology of the present invention has been used;

FIG. 10B is a block diagram of the data path taken in connection with FIG. 10A;

FIG. 11 is a functional block diagram of a preferred embodiment of a decentralized server network of a wireless telecommunications system.

Detailed description of preferred embodiments

FIG. 1 is a block diagram of an exemplary embodiment of an access terminal in communications with a decentralized wireless telecommunications server network. Access terminal 110 is a wireless terminal that can be used to access one or more of a plurality of services, including public switched telephone network (PSTN) and Internet services, offered by the serving network of a telecommunications system 120. wireless. The wireless telecommunications system 120, and the PSTN 122 and Internet 124 with which the wireless telecommunications system 120 connects, are further described with reference to FIG. 2. In the exemplary embodiment, the access terminal 110 is capable of connecting to the serving network of a wireless telecommunications system through the use of a radio antenna. The access terminal 110 may maintain a communication link with the serving network of a wireless telecommunications system by communicating with one or more access points, further described with reference to FIG. 2 and FIG. 3.

ES 2 392 901 T3

FIG. 2 is a functional block diagram of an exemplary embodiment of a decentralized server network of a wireless telecommunications system, also referred to as network 120. Access terminal 110 may communicate with network 120 over a wireless link.

The network 120 comprises a plurality of access points 220, which can communicate with the access points 110, and which are further described with reference to FIG. 3. Furthermore, the network 120 further comprises one or more routing devices 260, which connect the access points 220 with the service devices 270. The service devices 270 are connected to the PSTN 122 and the Internet 124. Although network 120 connects to external PSTN entities 122 and the Internet 124 in FIG. 2, the invention is not limited to a network that connects to these entities. One of ordinary skill in the art would know that other entities, such as an external private information provider or a billing service entity, could also be connected to the network 120. Furthermore, neither the PSTN 122 nor the Internet 124 is required to connect to the network 120. In FIG. 2 PSTN 122 and Internet 124 were listed to give an illustration of the type of entities that network 120 could connect to.

PSTN 122 represents the public switched telephone network, the sum of all circuit switched voice networks throughout the world. The acronym PSTN is well known to experts in the field of telecommunications.

The Internet 124 represents the public Internet, a world-spanning computer network used by individuals, governments, businesses, and organizations to share information between computers and computing devices. The term Internet is well known to experts in the field of telecommunications.

The H323 gateway 271 provides H.323 services according to the H.323 standard, thus providing standardized multimedia communications on a network. The H.323 standard was developed by the International Telecommunications Union and is described in the ITU-T H.323 recommendation. The H.323 gateway is connected to the PSTN 122 and the Internet 124. One skilled in the art in the related fields will be familiar with the services provided by an H323 gateway.

The NAS 272 is a network access server. The NAS 272 provides packet data services according to the IETF Internet draft "Network Access Server Requirements Next Generation (NASREQNG) NAS Model". One skilled in the art of related fields will be familiar with the services provided by a web access server.

The AAA server 274 provides authentication, authorization, and accounting services. A RADIUS server is an example of an AAA server and is described in IETF RFC 2138. One skilled in the art of related fields will be familiar with the services provided by an AAA server.

The DHCP server 276 provides dynamic host configuration services in accordance with the Dynamic Host Configuration Protocol, which is described in IETF RFC 2131. One skilled in the art of related fields will be familiar with the services provided by a DHCP server.

DNS server 278 provides domain name services. DNS is described in "Internetworking with TCP / IP Volume I, Principles, Protocols, and Architecture," by Douglas E. Comer. One skilled in the art of related fields will be familiar with the services provided by a DNS server.

All of the above devices are standard and use standard, non-proprietary protocols.

Although the illustration of service devices 270 contains the H323 gateway 271, the NAS 272, the AAA server 274, the server 276, and the DNS server 278, the invention is not limited to a network that contains exactly these service devices. . One skilled in the art would know that other services, such as an electronic page server, could be one of the service devices in the service devices 270. Furthermore, none or all of the service devices illustrated in the service devices 270 are required to be present. These chosen devices were illustrated to give an example of the type of entities that could be contained in service devices 270.

The network 120 connects access points 220 and service devices 270 together via various Ethernet connections and the use of a routing device 260. Routing device 260 is a serial routing device that routes (forwards) packets received from one physical interface to one or more additional interfaces using an internal process to determine which interface to forward each received packet. Routing devices are well known to those skilled in the art and are referred to by other names, such as gateways or switchboards. In the exemplary embodiment of the invention, the routing device 260 is a serial routing device that forwards IP (Internet Protocol) packets received from a plurality of Ethernet transports 280 to one or more of said Ethernet transports 280. In the exemplary embodiment, the routing device 260 supports the OSPF routing protocol. Ethernet is defined in IEEE 802.3, a standard published by the Institute of Electrical and Electronics Engineers (IEEE). The OSPF routing protocol is described in IETF RFC 2328. The OSPF routing protocol allows

ES 2 392 901 T3 send standard messages between routing devices to update their routing tables, so that IP packets can be distributed over the data path that has the lowest cost (the term "cost" is described in RFC 2328 of IETF). The OSPF routing protocol has an age field that is transmitted in every link state advertisement message. The age field indicates to a receiving routing device how long the link state advertisement should remain valid. A receiving routing device associates an age with the link status advertisement consistent with the age field received in a link status advertisement. A receiving routing device increases the associated ages for its routes as time passes. A receiving routing device compares these ages with the maximum age. Once an age associated with a route reaches the maximum age, the route is deleted. Hereafter, the maximum age is referred to as MaxAge, as in the IETF RFC 2328 description. One skilled in the data networking art will be familiar with Ethernet, IP, and OSPF.

Although the illustration of the network 120 connects the access points 220, the routing device 260, and the service devices 270 via an IP over an Ethernet transport 280, the invention is not limited to a network with a single consistent transport mechanism. in IP over Ethernet. One skilled in the art of networking is familiar with an Ethernet transport 280 that is used to transport IP packets from one point on the network to another. One skilled in the art will know that other transports, such as asynchronous transfer mode (ATM), could be used as the transport in all or a portion of the network 120, in an alternative embodiment. Although, in the exemplary embodiment, the network 120 consists of two subnets divided by a single routing device 260, an alternative embodiment could consist of two or more routing devices 260 connecting two or more subnets.

FIG. 3 is a functional block diagram of an exemplary embodiment of an access point. Access point 220 is the portion of network 120 that receives data from a serving device 270 and creates capsules and transmits them over a wireless link to an access terminal 110.

Access point 220 consists of a single MPC 320, further described with reference to FIG. 4, and zero or more connected MPTs 330, each of which is connected to an antenna, further described with reference to FIG. 5. In the exemplary embodiment, the MPC 320 and MPTs 330 are connected to the routing device 350 via IP over an Ethernet transport 340.

Although the illustration of the access point 220 connects the MPC 320 and the MPT 330 via an IP over Ethernet transport 340, the invention is not limited to such transport. In an alternative embodiment an ATM transport is used. In another alternative embodiment, the MPC 320, MPT 330, and routing device 350 are located in a single processing unit, and the routing device receives packets from these logical memory units through memory and signaling functions internal to the processor. One skilled in the art will know that various additional transports are also available.

FIG. 4 is a functional block diagram of an exemplary embodiment of a modem bank controller (MPC) 320. The MPC 320 is analogous to a base station controller plus a visitor location register (VLR), known to those skilled in the art of wireless telecommunication. While a base station controller controls certain functions in a centralized server network of a wireless telecommunications system, the MPC 320 performs many of those same functions in the exemplary decentralized network. For example, MPC 320 manages connection control for access terminals 110, and also manages radio link protocol (RLP) implementation. An RLP provides a means to transport a data stream between a remote station and a wireless telecommunications system. As is known to one skilled in the art, a radio link protocol (RLP) used for the TIA / EIA / IS-95B standard is described in the TIA / EIA / IS-707-A.8 standard, entitled "DATA SERVICE OPTIONS FOR SPREAD SPECTRUM SYSTEMS: RADIO LINK PROTOCOL TYPE 2 ”. The MPC 320 also manages a plurality of processes unique to the decentralized network and the present invention, especially as it relates to the present invention. The process of the present invention will be described in great detail in connection with FIG. 9.

For each active Internet data connection associated with a given MPC 320, the MPC 320 generates capsules to be transmitted by one or more MPT 330s and dispatches these capsules to the MPT 330. Likewise, when the MPC 320 receives a capsule from one or more MPT 330, decapsulates the capsule payload and processes the data. The MPC 320 contains one common controller (CC) 420 and zero or more dedicated controllers (DC) 430. Each dedicated controller 430 functions as an anchor point for the service device (s) 270 with which it is connected.

There is exactly one CC 420 for each instance of MPC 320. As illustrated in FIG. 4, the CC 420 is assigned two unique IP addresses: IPcct and IPcco. One of these IP addresses, IPcct, is used when communicating with the MPT 330s. The other IP address, IPcco, is used when communicating with entities present on the network 120 other than the MPT 330s.

Each time a session is initiated between an access terminal 110 and a network 120, the CC 420 dynamically allocates resources for a DC 430. Each DC 430 manages the generation and reception of capsules associated with the access terminal it is with. associated. Every time a session ends between an access terminal 110 and a network 6

ES 2 392 901 T3

120, the CC 420 deletes the instance of the DC 430. Always an instance of the DC 430 is deleted, the resources previously assigned to that instance are deallocated. As illustrated, a plurality of zero or more DC 430 may exist within the MPC 320 at any given time.

Each time the CC 420 allocates resources for a DC 430 instance, two unique IP addresses are assigned to the DC 430 instance: IPdct and IPdco. One of these IP addresses, IPdct, is used when communicating with MPT 330s. The other IP address, IPdco, is used when communicating with entities present on network 120 other than MPT 330s, such as NAS 272. In blocks 430A, 430B and 430N, the characters "A", "B" and "N", respectively, have been added to the subscripts of each of the IP addresses. This was done to illustrate that, in the exemplary embodiment, at any given point in time where multiple instances of DC 430 exist within the MPC 320, each such instance has its own unique pair of IP addresses.

The CC 420 and DC 430s send and receive messages about the IP transport 440 to the internal routing device 450. In the exemplary embodiment, the IP transport 440 is a memory bus over which IP packets can travel from one process to another and to an interface card. The internal routing device 450 is a network interface card that routes IP packets to / from the IP transport 440 and the external transport 340. The invention is not limited to this embodiment. As one of skill in the art will know, there are other embodiments, such as Ethernet, that could be used to transport IP packets within the MPC 320 and external transport 340.

FIG. 5 is a functional block diagram of an exemplary embodiment of a modem bank transceiver 330 (MPT). The MPT 330 manages the transmission and reception of capsules to / from the access terminal 110. In the exemplary embodiment, communications between the MPT 330 and the access terminal 110 use variable rate spread spectrum techniques, such as described in US Patent Publication No. 2003/0063583 entitled "Method and Apparatus for High Rate Packet Data Transmission ”, filed November 3, 1997, assigned to the assignee of the present invention. The MPT 330 contains a common transceiver (CT) 520 and a plurality of zero or more dedicated transceivers (DT) 530, each of which is capable of carrying out spread spectrum modulation and demodulation used for communications with one or more access terminals.

In the exemplary embodiment, there is exactly one CT 520 for each instance of MPT 330. As illustrated in FIG. 5, the CT 520 is assigned a unique IP address, IPcr, to communicate with entities present on the network 120.

Each time it is desired to open a dedicated communications link between an access terminal 110 and an MPT 330, the CT 520 dynamically creates a DT 530 instance. Each DT 530 manages the transmission / reception of capsules associated with the dedicated communications link. with an access terminal 110. Each time it is desired to close a dedicated communications link between an access terminal 110 and an MPT 330, the CT 520 deletes the DT 530 instance. As illustrated in FIG. 5, a plurality of zero or more DT 530 may coexist within the MPT 330 at any given time.

Each DT 530 instance is assigned its own unique IP address, IPdt, used to communicate with entities present on network 120. In blocks 530A, 530B and 530N, the characters “A”, “B” and "N", respectively, to the subscripts of each of the IP addresses. This was done to illustrate that, in the exemplary embodiment, at any given point in time where multiple instances of DT 530 exist within the MPT 330, each such instance has its own unique IP addresses. In other words, the IP addresses assigned to each concurrent MPT 330 instance are not the same.

The CT 520 and DT 530s send and receive messages about the IP transport 540 to the internal routing device 550. In the exemplary embodiment, the IP transport 540 is a memory bus over which IP packets can travel from one process to another and to an interface card. Internal routing device 550 is a network interface card that routes IP packets to / from IP transport 540 and Ethernet 340. The invention is not limited to this embodiment. As one skilled in the art will know, there are other embodiments, such as ATM, that could be used to transport IP packets within the MPT 330 and external transport 340.

In addition, the CT 520 and DT 530 transceivers have the ability to transmit and receive data to access the terminals through the use of a common antenna, as illustrated. In an alternative embodiment, the CT 520 and DT 530 transceivers have the ability to transmit and / or receive data through the use of a plurality of two or more antennas.

FIG. 6A is a network diagram illustrating entities that are used in an Internet data connection when an access terminal 110 has an open wireless data communication channel with a single access point 220. In FIG. 6A, the following labels apply.

In the exemplary Internet data connection, the access terminal 110 transmits and receives IP packets embedded in PPP packets by embedding the PPP packets, or portions thereof, in wireless packets that adhere to the wireless protocol.

ES 2 392 901 T3

The entities diagrammed within the access point 220A are only those entities that are part of the data path for the Internet data connection. For example, although only a single MPT is diagrammed, the MPT 330AA, there may be other MPT 330s within the access point 220 that are not part of the Internet data connection in question. The DC 430AA has an IP address of IPdcoaa associated with it for use in communicating with the NAS 272, and the DC 430AA has an IP address of IPdctaa for use in communicating with one or more instances of the MPT 330. The MPT 330AA is an instance of the MPT 330, described above with reference to FIG. 3 and FIG. 5.

Wireless protocol packets are transmitted between the MPT 330AA and the wireless transport access terminal 110 610.

FIG. 6B is a diagram showing the exemplary data flow for the Internet data connection adhering to the data path illustrated in FIG. 6A. On the forward link, an IP packet having a destination IP address associated with access terminal 110 travels from Internet 124 on Ethernet transport 280E to NAS 272. In the NAS 272, the packet is encapsulated in a PPP packet, which is further encapsulated in an L2TP packet with a destination IP address associated with the DC 430AA (IPdcoaa), located within the MPC 320A. L2TP is well known to those of skill in the networking art, and is described in IETF RFC 2661. This L2TP packet is transmitted over the Ethernet transport 280D to the routing device 260. The routing device 260 forwards this L2TP packet over the Ethernet transport 280C to the routing device 350A. The routing device 350A then forwards this L2TP packet over the Ethernet transport 340A to its destination on the DC 430AA. The DC 430AA, located in the MPC 320A, receives the L2TP packet and decapsulates the embedded PPP frame. The DC 430AA then encapsulates the PPP frame in one or more wireless protocol capsules, which are further encapsulated in IP packets with a destination address associated with the MPT 330AA. These IP packets are then transmitted over the Ethernet link 340A to the MPT 330AA. The MPT 330AA de-encapsulates the wireless protocol capsules from the IP packets and transmits these capsules to the access terminal 110 over the wireless transport 610.

As one of ordinary skill in the art readily understands, packets moving in the direction of the reverse link take the opposite path. One of ordinary skill in the art also readily understands that there are various link layer protocols that could be used in place of PPP and L2TP.

FIG. 7A is a network diagram illustrating entities that are used in an Internet data connection when access terminal 110 has an open wireless data communication channel with two access points 220. In particular, FIG. 7A illustrates the network entities that would be in use if the access terminal 110 was previously connected as diagrammed in FIG. 6A, and subsequently access terminal 110 went into soft handoff with access point 220B. In FIG. 7A, all labels have the same meaning as they had with reference to FIG. 6A, with the following only exception.

Access point 220B was not present in FIG. 6A. The entities diagrammed within the access point 220B are only those entities that are part of the data path for the aforementioned Internet data connection. Wireless protocol packets are transmitted between the MPT 330BA and the access terminal 110 over the transport 610. Although the MPT 330BA is different from the MPT 330AA, since the access terminal 110 receives a joint signal from these MPT 330s, it is considered a single transport 610.

FIG. 7B is a diagram showing the exemplary data flow for the Internet data connection adhering to the data path illustrated in FIG. 7A. On the forward link, an IP packet having a destination IP address associated with access terminal 110 travels from Internet 124 on Ethernet transport 280E to NAS 272. In the NAS 272, the packet is encapsulated in a PPP packet, which is further encapsulated in an L2TP packet with a destination IP address of DC 430AA (IPdcoaa), located inside the MPC 320A. This L2TP packet is transmitted over the Ethernet transport 280D to the routing device 260. The routing device 260 forwards this L2TP packet over the Ethernet transport 280C to the routing device 350A. The routing device 350A then forwards this L2TP packet over the Ethernet transport 340A to its destination on the DC 430AA. The DC 430AA, located in the MPC 320A, receives the L2TP packet and decapsulates the embedded PPP frame. The DC 430AA then encapsulates the PPP frame in one or more wireless protocol capsules, which are further encapsulated in IP packets that have one or more destination addresses associated with the MPT 330AA and MPT 330BA.

Packets destined for the IP address associated with the MPT 330AA are received by the MPT 330AA through the Ethernet transport 340A. The MPT 330AA de-encapsulates the wireless protocol capsules from the IP packets and transmits the wireless protocol capsules to the access terminal 110 over the wireless transport 610 at designated times in the IP packets.

Packets destined for the IP address associated with the MPT 330BA are received by the routing device 350A through the Ethernet transport 340A. . The routing device 350A forwards these IP packets over the Ethernet transport 280C to the routing device 350B. The routing device 350B forwards these IP packets over the Ethernet transport 340B to their destination on the MPT 330BA. The MPT 330BA de-encapsulates the wireless protocol capsules from the IP packets and transmits the capsules of the 8

ES 2 392 901 T3 wireless protocol to access terminal 110 over wireless transport 610 at designated times in IP packets.

In one embodiment, the IP packet timestamps are such that the same Internet payload from both the MPT 330AA and MPT 330BA is transmitted over link 610 at the same time.

As one of ordinary skill in the art readily understands, packets moving in the direction of the reverse link take the opposite path.

FIG. 8A is a network diagram illustrating, with one exception (MPC 320B), the entities that are used for forward and reverse link data flow in an Internet data connection when access terminal 110 has a communications channel open data wireless with a single access point 220, but in which the capsules received by the access point 220B are transmitted to an MPC 320A within another access point 220A. In particular, FIG. 8A illustrates the network entities that would be in use if the access terminal 110 was previously connected as diagrammed in FIG. 7A, and subsequently terminated the link between access terminal 110 and access point 220A. In other words, FIG. 8A may represent the entities associated with a given Internet data connection, immediately after the access terminal 110 completes a soft handoff. Alternatively, FIG. 8A illustrates the network entities that would be in use if the access terminal 110 was previously connected as diagrammed in FIG. 7A, and subsequently a hard handoff was carried out to MPT 330B within access point 220B. In FIG. 8A, all labels have the same meaning as they had with reference to FIG. 7A.

There is an entity diagrammed in FIG. 8A, the MPC 320B, the exception mentioned above, which is not used for the forward and reverse link data stream of said Internet data connection. This entity, the MPC 320B, is an instance of the MPC 320, described above with reference to FIG. 3 and FIG. 4. The use of the MPC 320B will be further described with reference to FIGURES 9 and 10.

FIG. 8B is a diagram showing the exemplary data flow for the Internet data connection adhering to the data path illustrated in FIG. 8A. On the forward link, an IP packet having a destination IP address associated with access terminal 110 travels from Internet 124 on Ethernet transport 280E to NAS 272. On the NAS 272, the packet is encapsulated in a PPP packet, which is further encapsulated in an L2TP packet with a destination IP address associated with the DC 430AA (IPdc_ORaa), located inside the MPC 320A. This L2TP packet is transmitted over the Ethernet transport 280D to the routing device 260. The routing device 260 forwards this L2TP packet over the Ethernet transport 280C to the routing device 350A. The routing device 350A then forwards this L2TP packet over the Ethernet transport 340A to its destination on the DC 430AA. The DC 430AA, located in the MPC 320A, receives the L2TP packet and decapsulates the embedded PPP frame. The DC 430AA then encapsulates the PPP frame in one or more wireless protocol capsules, which are further encapsulated in IP packets that have one or more destination addresses associated with the MPT 330BA.

Packets destined for the IP address associated with the MPT 330BA are received by the routing device 350A through the Ethernet transport 340A. . The routing device 350A forwards these IP packets over the Ethernet transport 280C to the routing device 350B. The routing device 350B forwards these IP packets over the Ethernet transport 340B to their destination on the MPT 330BA. The MPT 330BA de-encapsulates the wireless protocol capsules from the IP packets and transmits the wireless protocol capsules to the access terminal 110 over the wireless transport 610.

As one of ordinary skill in the art readily understands, packets moving in the direction of the reverse link take the opposite path.

FIG. 9 is a flow chart illustrating an exemplary embodiment of the anchor point transfer methodology of the present invention. The methodology presents a means by which an entity that exists in one location in a network can be moved to another location in the network, and in which such a methodology results in a very efficient use of network bandwidth.

It is worth noting that by the time block 1000 is reached, the MPC 320A has the ability to route packets to IPdcoaa at a nominally high cost. Although nominally high, this cost is the lowest cost path associated with delivering packets on network 120 to the IP address IPdcoaa.

At block 1000, a first MPC 320 makes the decision that one of its DC 430s should move to a second MPC 320 within the network. In the exemplary embodiment of the present invention, such a decision would be made when, in an Internet data connection, the resources of the DC 430 of an access point 220 are used, but in which said DC 430 does not communicate with any MPT 330 within the same access point 220. FIGURES 8A and 8B provide illustrations of an exemplary embodiment of a network at a time when it is desirable to implement the methodology of the present invention. FIGURES 10A and 10B provide illustrations of one embodiment

ES 2 392 901 T3 exemplary of a network in an instant immediately after the use of the methodology of the present invention.

For the sake of clarity and simplicity, FIG. 9 is described below with specific reference to the entities referenced in FIGS. 8A, 8B, 10A, and 10B, whenever possible. However, one skilled in the art will appreciate that the invention herein is not limited to the specific entities or network configurations of those figures. With reference to FIG. 8A, at block 1000, the mPc 320A makes the decision to move the DC 430AA from the MPC 320A to the MPC 320B. The procedure then proceeds to block 1010.

At block 1010, the MPC 320A sends a message to the MPC 320B. The message contains a request for the MPC 320B to begin configuring a DC 430 that contains information related to the network interface, such as NAS communication information, equivalent to that of the DC 430AA. In the exemplary embodiment, the message contains the L2TP tunnel status information associated with the DC 430AA, such as its IP address, IPdcoaa, and the tunnel ID of its L2TP session. The procedure then proceeds to block 1020.

In block 1020, the MPC 320B receives the message referenced in block 1010. According to the request for the message, the MPC 320B allocates resources for a new DC 430. The new DC 430 is initialized to the L2Tp tunnel values ​​received in the message previously mentioned. Although this new DC 430, present in the MPC 320B, has been created and initialized, it is not used at this point in an Internet data connection. The procedure then proceeds to block 1030.

At block 1030, the MPC 320B sends a message to its local routing device, the routing device 350B, specifying that the MPC 320B has the ability to route packets to IPdcoaa at nominally low cost. In the exemplary embodiment, this message is an OSPF link state advertisement (LSA). In one embodiment, the message sent is an IP multicast or broadcast message, thus allowing a plurality of local routing devices to receive the message. The routing cost advertised in this message, being nominally low, is less than the nominally high cost route that is currently associated with the MPC 320A. Since all routing devices on network 120 are OSPF-enabled, this new low-cost route, for packets that have a destination address of IPdcoaa, will propagate through routing devices on network 120. Thus, at some point Point of the future, after the propagation of the routing information has taken place, the routing devices will begin to route the packets having a destination address of IPdcoaa to the MPC 320B. The procedure then proceeds to block 1040.

At block 1040, the MPC 320B starts a first timer. The timer is set to a value representative of the maximum amount of time it should take for the low-cost route, mentioned in reference to block 1030, to propagate through network 120. The procedure then proceeds to block 1060.

The methodology of the present invention is such that the procedure does not proceed to block 1070 until it can be guaranteed that propagation of the low-cost path through network 120 has taken place. The stage represented by block 1060 is the one in which this security is achieved. In block 1060, the MPC 320B checks if said first timer has expired or if it has received a packet destined for IPdcoaa. If neither event has occurred, the procedure returns to block 1060, where the same check is performed again. In block 1060, if said first timer has expired or the MPC 320B has received a packet destined for IPdcoaa, the procedure then proceeds to block 1070.

At block 1070, the MPC 320B sends a message to the MPC 320A. The message contains a request that the MPC 320A complete the transfer from the DC 430AA to the MpC 320B.

At block 1080, the MPC 320A receives the aforementioned message. In response, the MPC 320A sends a message to its local routing device specifying that packets with a destination IP address of IPdcoaa and packets with a destination IP address of IPdctaa are no longer routed to the MPC 320A. In the exemplary embodiment, this message is an OSPF LSA. In one embodiment, the message sent is an IP broadcast message, thus allowing a plurality of local routing devices to receive the message. Since all routing devices on the network 120 are OSPF-enabled, the fact that the MPC 320A no longer functions as a routing device for devices that target addresses associated with the DC 430AA will be propagated by the routing devices of the network. network 120. Thus, at some point in the future, after the propagation of the routing information has taken place, the routing devices will no longer associate the MPC 320a as a routing device that can be used when attempting to route packets to the DC 430AA. The procedure then proceeds to block 1090.

At block 1090, the MPC 320A sends a message to the MPC 320B. The message contains communications information from transceivers (eg, MPT), such as the IPdctaa and IP address of the MPT 330BA. Additional useful information may also be included when transferring the DC 430AA from the MPC 320A to the MPC 320B. In one embodiment, RLP status information is contained in the message. In another embodiment, the wireless protocol layer 2 status information is contained in the message. The procedure then proceeds to block 1100. Layer 2 is a layer of the telecommunications system that allows correct transmission and reception.

ES 2 392 901 T3 of signaling messages, including the detection of partial duplicates. This is known to one of ordinary skill in the art and is described in the TIA / EIA / IS-95-B standard of the Telecommunications Industry Association, entitled "MOBILE STATION-BASE STATION COMPATIBILITY STANDARD FOR DUAL-MODE WIDEBAND SPREAD SPECTRUM CELLULAR SYSTEMS ”, hereinafter referred to as IS-95-B.

At block 1100, the MPC 320A deallocates all of its resources associated with the DC 430AA. The procedure then proceeds to block 1110.

At block 1110, the MPC 320B receives the message that had been transmitted by the MFC 320A, described with reference to block 1090. Upon receipt of this message, the MPC 320B completes the initialization of the new DC (the one referred to in the description of block 1020) initializing said new DC with the values ​​received in this message. At this point, said new DC of the MPC 320B is configured essentially the same as the DC 430AA was in the MPC 320A, before its deallocation specified in block 1100. Thus, although the new DC of the MPC 320B is physically housed in one address Unlike the DC 430AA, which was housed in the MPC 320A, the two DCs are essentially one and the same. Thus, at this point, considering that the DC 430AA was deallocated in block 1100, and considering that the new DC is essentially the same as the deallocated, the new DC of the MPC 320B is hereinafter referred to as DC 430AA, and is illustrated as such in FIG. 10A. The procedure then proceeds to block 1120.

At block 1120, the MPC 320B sends a message to its local routing device, the routing device 350B, specifying that the MPC 320B has the ability to route packets to IPdctaa at nominally low cost (a cost less than the associated cost). previously with the routing of this address to the MPC 320A). In the exemplary embodiment, this message is an announcement of the status of the OSPF link. Since all routing devices on network 120 are OSPF-enabled, this new low-cost path for packets that have a destination address of IPdctaa will be propagated by routing devices on network 120. Thus, at some point in the future After the propagation of the routing information takes place, the routing devices will begin to route packets having a destination address of IPdctaa to the MPC 320B. Due to the fact that all such packets originate from the MPT 330BA, and the fact that the MPT 330BA is on the same subnet as the MPC 320B, in all likelihood this operation will be extremely fast. Unwarranted ARP, a term known to those skilled in the network art, refers to the generation of an unsolicited ARP. In one embodiment, the MPC 320B sends an unjustified ARP message to all other members of its subnet informing those entities that all packets with the destination address of IPdctaa should be sent to the address of the Ethernet hardware of the MPC 320B. . Although not necessary, the use of unwarranted ARP by itself, or in conjunction with an OSPF message, can decrease the amount of time it takes for packets from the MPT 330BA to be routed to the MPC 320B. The procedure then proceeds to block 1130.

At block 1130, the MPC 320B starts a second timer. The timer is set to a value representative of the maximum amount of time it should take for the low-cost path, mentioned in reference to block 1120, to propagate through the network 120. In the exemplary embodiment, this second timer is set to the same The value that the first timer was set to in block 1040. The procedure then proceeds to block 1140.

The methodology of the present invention is such that the procedure does not proceed to block 1150 until it can be guaranteed that the propagation, mentioned above, of the low-cost path through the network 120 has taken place. The stage represented by block 1140 is the one in which this security is achieved. At block 1140, the MPC 320B checks if the second timer has expired or if it has received a packet destined for IPdctaa. If neither event has occurred, the procedure returns to block 1140, where the same check is performed again. At block 1140, if the second timer has expired or the MPC 320B has received a packet destined for IPdctaa, the procedure then proceeds to block 1150.

At block 1150, the MPC 320B sends zero or more messages to the access terminal 110 over the transport 610. In the exemplary embodiment, the newly initialized DC 430AA contains neither the RLP status nor the status of the wireless layer 2 that was in progress. present in the DC 430AA when it resided in the MPC 320A. Thus, in the exemplary embodiment, the DC 430AA transmits messages to the access terminal 110 requesting that the access terminal 110 restart its RLP layers and wireless layer 2. In an alternate embodiment, the DC 430AA contains all of the status information that was contained in the DC 430AA when it resided in the MPC 320B. In such a case, in this block 1150 no message is transmitted to the access terminal 110. The procedure then proceeds to block 1160.

The methodology of the present invention is such that the procedure does not proceed to block 1170 until it can be guaranteed that the propagation, mentioned above, of the low-cost routes through the network 120 has taken place. The stage represented by block 1160 is the one in which this security is achieved. At block 1160, the MPC 320B checks if the second timer has expired. In the exemplary embodiment, the first timer will always have expired at the point where the second timer has expired. If the second timer has not expired, the procedure returns to block 1160, where the same check is performed again. At block 1160, if the second timer has expired, then the procedure proceeds to

ES 2 392 901 T3 block 1170. In one embodiment, block 1140 is not present, and the procedure goes directly from block 1150 to block 1170. In another embodiment, block 1160 checks the expiration of the first timer instead of the second timer.

At block 1170, the MPC 320B sends a message to its local routing device, the routing device 350B, specifying that the MPC 320B has the ability to route packets to IPdcoaa and IPdctaa at a nominally high cost. In the exemplary embodiment, this message is an OSPF link state advertisement (LSA). In one embodiment, the message sent is an IP broadcast message, thus allowing a plurality of local routing devices to receive the message. The routing cost advertised in this message is nominally high. Since all routing devices on network 120 are OSPF enabled, this new high-cost path, for packets having destination addresses of IPdcoaa and IPdctaa, will be propagated by routing devices on network 120. Thus, at some point in the future, after the propagation of the routing information has taken place, the routing devices will replace the nominally low costs associated with routing these packets to the MPC 320B with nominally high costs. This step puts the network 120 in a state where the methodology of the present invention could be used again, at a later point in time, to move the DC 430AA from the MPC 320B to another MPC 320 located within the network 120. The procedure then proceeds to block 1180.

At block 1180, the procedure of the methodology of the present invention is complete. One skilled in the art will appreciate that FIG. 9 provides an arrangement of the steps for exemplary implementation of the methodology of the present invention. One skilled in the art will appreciate that several of the steps can be rearranged without departing from the scope of the invention.

The exemplary embodiment of the methodology of the present invention is a novel method for moving an entity containing an IP address from one location to another within a network. Not only is this methodology ideal for transparently moving an anchor point within a decentralized server network of a wireless telecommunications system, it is also ideal for moving an IP address across a corporate or university-level network.

The use of OSPF in the exemplary embodiments overcomes some of the drawbacks that might be encountered in a system using mobile IP.

The first drawback of mobile IP is that IP packets are susceptible to taking very indirect routes. For example, let's take the case in which a first node moves from its home network to a foreign network, in which a second node already resides. In such a case, if the second node sends one or more packets to the IP address assigned to the first node, all such packets will be routed from the foreign network to the visiting network, and then tunnelled back to the foreign network. The use of these indirect routes introduces latency and causes more bandwidth to be used than would have been used if a direct route had been taken and no extra tunneling had been needed.

The second drawback of mobile IP is the extra overhead that mobile IP adds to each packet. In mobile IP, packets routed from a home agent to a foreign agent are encapsulated, thus using extra bandwidth to support this overhead.

The third drawback of mobile IP is its lack of built-in redundancy support. With mobile IP, if the home agent experiences a failure, a mobile node visiting a foreign network will be unable to receive packets, because existing mobile IP standards do not address the issue of providing redundancy to the home agent.

The present invention provides mobility within a network using a novel methodology that does not suffer from any of the above-mentioned drawbacks. Thus, the invention can provide high efficiencies in networks other than those that function as a server network for a wireless telecommunications system. There are multiple alternative embodiments that support the use of the methodology of the present invention in various networks. In one embodiment, an entity containing an IP address, such as a laptop computer, frequently sends a broadcast (or multicast) link status advertisement in an age field that is slightly less than the MaxAge value. These link status ads contain a cost (a metric) equal to a constant value that is nominally low. Thus, when the entity moves from one network subnet to another, its old advertisements on the old subnet, which contained a nominally low metric, quickly reach the MaxAge value and expire. And, on the new subnet, new advertisements with the same nominally low metric quickly take hold, allowing packets to be routed to the new location without the need for a tunneling protocol such as mobile IP.

The present invention uses OSPF as a cost-effective and standardized means of moving an entity across a network, which is a novel use compared to the original intent of the OSPF protocol.

In the narrower scope of the present invention, the methodology that allows moving an anchor point specifically within a wireless telecommunications system, there are alternative embodiments. One such alternative embodiment uses mobile IP to achieve its goal of transparent one-point mobility.

ES 2 392 901 T3 anchorage within a wireless telecommunications system. In such an embodiment, each DC 430 is associated with a plurality of one or more self-agents. In one embodiment, the OSPF messages described with reference to FIG. 9 would be replaced by mobile IP registration messages that would be sent by each DC 430 after moving from one portion of the system to another.

FIG. 10A is a network diagram illustrating the entities that are used in an Internet data connection when the access terminal 110 has an open wireless data communication channel with a single access point 220B after the procedure has been used of the present invention, described with reference to FIG. 9. In particular, FIG. 10A illustrates the network entities that would be in use if the access terminal 110 was previously connected as diagrammed in FIG. 8A and subsequently used the methodology of the present invention, described with reference to FIG. 9. Alternatively, FIG. 10A illustrates the network entities that would be in use if the access terminal 110 was previously connected as diagrammed in FIG. 6A and subsequently a hard handoff was carried out to access point 220B, using the methodology of the present invention, described with reference to FIG. 9. Alternatively, FIG. 10A illustrates the network entities that would be in use if the access terminal 110 was previously connected as diagrammed in FIG. 7A and subsequently a hard handoff was carried out to access point 220B, using the methodology of the present invention, described with reference to FIG. 9.

In FIG. 10A, all labels have the same meaning as they had with reference to FIG. 8A, with the following only exception. As explained with reference to FIG. 9, the DC 430AA physically located within the MPC 320B, is a copy of the DC 430AA that was physically located within the MPC 320A. Although DCs exist within different MPCs and therefore use a different resource bank, and could have received different labels for this, DCs receive the same 430AA label. This is done to illustrate that both of the above-mentioned DCs have the same attributes, including IP addresses, and perform the same functions, regardless of their different locations .

FIG. 10B is a diagram showing the exemplary data flow for the Internet data connection adhering to the data path illustrated in FIG. 10A. On the forward link, an IP packet having a destination IP address associated with access terminal 110 travels from Internet 124 on Ethernet transport 280E to NAS 272. On the NAS 272, the packet is encapsulated in a PPP packet, which is further encapsulated in an L2TP packet with a destination IP address associated with the DC 430AA (IPdcoaa), which has been moved to the MPC 320B. This L2TP packet is transmitted over the Ethernet transport 280D to the routing device 260. The routing device 260 forwards this L2TP packet over the Ethernet transport 280C to the routing device 350B. The routing device 350B then forwards this L2TP packet over the Ethernet transport 340B to its destination on the DC 430AA. The DC 430AA, located in the MPC 320B, receives the L2TP packet and decapsulates the embedded PPP frame. The DC 430AA then encapsulates the PPP frame in one or more wireless protocol capsules, which are further encapsulated in IP packets with a destination address associated with the MPT 330AA. These IP packets are then transmitted over the Ethernet link 340A to the MPT 330AA. The MPT 330AA de-encapsulates the wireless protocol capsules from the IP packets and transmits these wireless protocol capsules to the access terminal 110 over the wireless transport 610.

As one of ordinary skill in the art readily understands, packets moving in the direction of the reverse link take the opposite path.

FIG. 11 is a functional block diagram of a preferred embodiment of a decentralized server network of a wireless telecommunications system. This preferred embodiment is an alternative embodiment of the exemplary embodiment illustrated in FIG. 2. This preferred embodiment differs from the exemplary embodiment in the following.

In FIG. 11, access points 220 communicate with external devices on network 120 via T1 transport 1120. This is in contrast to FIG. 2, wherein the access point 220 communicates with external devices on the network 120 via Ethernet 280. One skilled in the art readily understands that the T1 transport 1120 is one of a variety of transports, such as E1 or microwave , which can be used to connect access points 220.

In FIG. 11, packets sent from one access point 220A to another access point 220N must first travel through one or more routing devices 260. This is because, as illustrated, each access point is on its own physical subnet. This is in contrast to FIG. 2, in which the packets can be sent directly from one access point 220 to another access point 220 over a single transport. As illustrated in the exemplary embodiment, FIG. 2, this is possible in the exemplary embodiment because the transport 280 connects to all access points 220. One skilled in the art readily understands that in a network containing more than one subnet, each subnet need not be restricted to a single access point 220. In other words, one skilled in the art readily understands that some subnets may contain exactly one access point 220, while others contain more than one access point 220.

ES 2 392 901 T3

One skilled in the art also readily understands that each access point in a network 120 need not use the same physical transport to communicate with other devices on the network. For example, a network 120 could be designed such that an access point 220D communicates with a routing device 260 via a T1 transport, while another access point 220E communicates with a routing device 260 via of an E1 transport, while another access point 220F communicates with a routing device 260 via another transport, such as Ethernet.

Finally, one skilled in the art readily understands that the methodology of the present invention, described herein, works in all such embodiments of the network 120. In all such embodiments, the present methodology invention, described with reference to FIG. 9, stays the same. This is because the methodology of the present invention was designed to be flexible enough to work in various network configurations.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. The various modifications of these embodiments will be immediately apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of inventiveness. Thus, the present invention is not intended to be limited to the embodiments shown herein, but should be given the broadest scope consistent with the features set forth in the following claims.