(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2003/0018810 A1
`
`(43) Pub. Date:
`Jan. 23, 2003
`Karagiannis et al.
`
`US 20030018810A1
`
`(54) SEAMLESS HANDOFF IN MOBILE IP
`
`Related US. Application Data
`
`(75)
`
`Inventors: Georgios Karagiannis, Neede (NL);
`Geert Heijenk, Enschede (NL); Karim
`El Malki, Roma (IT); Hesham
`Soliman, Endeavour Hills (AU)
`
`(60) Provisional application No. 60/241,539, filed on Oct.
`18, 2000.
`
`Publication Classification
`
`Correspondence Address:
`Spencer C. Patterson
`Jenkens & Gilchrist, RC.
`3200 Fountain Place
`1445 Ross Avenue
`
`Dallas, TX 75202-2799 (US)
`
`(73) Assignee: Telcfonaktiebolaget
`(publ)
`
`(21) Appl. No.:
`
`10/084,879
`
`(22)
`
`Filed:
`
`Oct. 18, 2001
`
`L M Ericsson
`
`(5 1)
`(52)
`
`(57)
`
`Int. Cl.7 ................................................... G06F 15/173
`US. Cl.
`.............................................................. 709/238
`
`ABSTRACT
`
`In a system and method for handing off a mobile node in a
`seamless manner in a wireless access network, procedures
`are implemented for allowing the mobile node to synchro-
`nize the handoff with a base node (e.g., a home agent) and
`a correspondent node. In this way, a seamless handoff may
`be achieved, since few or no data packets sent between the
`base node or the correspondent node and the mobile node are
`lost. The procedures are supported by both Mobile IPv4 and
`Mobile IPv6 as well as Hierarchical Mobile IPv4 and
`Hierarchical Mobile IPv6.
`
`A
`
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`

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`Patent Application Publication
`
`Jan. 23, 2003 Sheet 1 0f 46
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`US 2003/0018810 A1
`
`Jan. 23, 2003
`
`SEAMLESS HANDOFF IN MOBILE IP
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`
`[0001] The present application is related to, claims priority
`from, and incorporates by reference,
`the subject matter
`disclosed in Us. Patent Application No. 60/241,539,
`entitled “Scamless Handoff in Mobile IPv4 and Mobile
`IPv6,” filed with the US. Patent and Trademark Office on
`Oct. 18, 2000.
`
`BACKGROUND OF THE INVENTION
`
`[0002]
`
`1. Field of the Invention
`
`[0003] The present invention is related to mobile network-
`ing and, more particularly, to mobile networking using the
`Mobile IP standard.
`
`[0004]
`
`2. Description of the Related Art
`
`[0005] Advances in wireless communication technology
`have given rise to a number of wireless applications such as
`pagers, cellular phones, and mobile computing and network—
`ing applications. Mobile computing and networking allows
`a mobile device capable of connecting to a network to freely
`move while remaining connected to the network and to the
`Internet. As the mobile device moves between different
`networks and sub-networks, the connection to the old net-
`work or sub-network is dropped as needed, and a connection
`to a new network or sub-network is established. Such a
`handofi' is made possible through an extension of the Internet
`Protocol (IP) referred to as Mobile IP. In general, Mobile IP
`creates the perception that the mobile device is always
`attached to the same network or sub-network even as it is
`
`moving around. Specifically, Mobile IP allows the mobile
`device to retain the same network or IP address regardless of
`the particular network or sub-network to which the mobile
`device is actually connected. Thus, a remote application can
`send data packets to the mobile device at the same IP address
`no matter how many handoffs (i.e., changes in network or
`sub-network connections) may have occurred.
`
`[0006] Mobile IP accomplishes the above function by
`allowing the mobile node to use two IP addresses. The first
`IP address, called the home address, is static and is used to
`identify the mobile device when it is in its home network. A
`home network is the network in which the mobile device
`
`appears to be located for the rest of the network or the
`Internet. More formally, the home network is the network
`which contains the home registration of the mobile device.
`The second IP address, called the care-of address,
`is
`dynamic and is used to identify the mobile device when it is
`away from the home network. As the mobile device is
`handed off to each new network or sub-network, it obtains
`a care-of address from that network or sub-network. The
`mobile device is likely to use multiple different care-of
`addresses as it roams between different networks and sub-
`
`networks. Upon obtaining a new care-of address, the mobile
`device registers the new care-of address with the home
`network Thereafter, the home network redirects data packets
`that are destined for the mobile device at its home address
`
`(in the home network) to the new care-of address.
`
`[0007] Although Mobile IP allows the mobile device to
`freely move between different networks and sub-networks
`while appearing to maintain the same network connection,
`
`the transition is not always a seamless one. For example,
`when a handoff occurs in the middle of an ongoing data
`transfer session, some data packets may be sent to the old
`care-of address before registration of the new care-of
`address can be completed. As a result, these data packets
`may become lost, thereby disrupting the flow of data packets
`to the mobile device. Depending on the duration of the
`disruption, the data transfer session may be only slightly
`affected or severely affected. For example, where the net—
`work is particularly slow or congested (hence, registration is
`delayed), a large number of data packets may be lost,
`possibly causing the application session to terminate or
`otherwise fail.
`
`[0008] Accordingly, it is desirable in a wireless access
`network to provide a system and method for handing off a
`mobile device in a substantially seamless manner.
`SUMMARY OF THE INVENTION
`
`[0009] The present invention is related to a system and
`method for handing off a mobile node in a seamless manner
`in a wireless access network. Procedures are implemented
`for allowing the mobile node to synchronize the handoff
`with a base node and a correspondent node. In this way, a
`seamless handoff may be achieved, since few or no data
`packets sent between the base node or the correspondent
`node and the mobile node are lost. The procedures are
`supported by both Mobile IPv4 and Mobile IPv6 as well as
`Hierarchical Mobile IPv4 and Hierarchical Mobile IPv6.
`
`In general, in one aspect, the invention is directed
`[0010]
`to a method of handing off a mobile node from an old
`sub-network router to a new sub-network router in an
`Internet Protocol based wireless access network. The
`
`method comprises using information from a lower layer of
`the OSI (Open Systems Interconnection) model to notify the
`mobile node that a connection with the old sub-network
`
`router will be discarded within a predetermined amount of
`time, obtaining a new care-of address for the mobile node
`from the new sub-network router, and sending a request
`message from the mobile node to a base node via the new
`sub-network router requesting a new binding. The method
`further comprises creating a new care-of address binding in
`the base node, issuing a reply message from the base node
`to the mobile node via the new sub-network router indicat-
`
`ing that the new care-of address binding has been created,
`and synchronizing a transfer of old care-of address data
`packets from the base node to the mobile node.
`
`the invention is
`in another aspect,
`In general,
`[0011]
`directed to an Internet Protocol based wireless access net-
`
`work. The network comprises a mobile node adapted to
`obtain a new care-of address from a new sub-network router
`
`and to issue a request message via the new sub-network
`router requesting a new binding upon being notified from a
`lower layer of the OSI (Open Systems Interconnection)
`model that a connection with an old sub-network router will
`
`be discarded within a predetermined amount of time. The
`system further comprises a base node adapted to create the
`new carc-of address binding upon receiving the request
`message from the mobile node and to issue a reply message
`to the mobile node via the new sub-network router indicat-
`
`ing that the new carc-of address binding has been created,
`wherein the mobile node and the base node are further
`adapted to transfer old care-of address data packets from the
`base node to the mobile node in a synchronized manner.
`
`

`

`US 2003/0018810 A1
`
`Jan. 23, 2003
`
`In general, in yet another aspect, the invention is
`[0012]
`directed to a method of handing off a mobile node from an
`old sub-network router to a new sub-network router in an
`Internet Protocol based wireless access network. The
`
`method comprises using information from a lower layer of
`the 081 (Open Systems Interconnection) model to notify the
`mobile node that a connection with the old sub-network
`
`router will be discarded within a predetermined amount of
`time, obtaining a new care—of address for the mobile node
`from the new sub-network router, and sending a request
`message from the mobile node to a base node via the new
`sub—network router requesting a new binding, the base node
`being a predetermined one of a home agent, a gateway
`foreign agent, and a mobility anchor point. The method
`further comprises the steps of creating a new care-of address
`binding in the base node, issuing a reply message from the
`base node to the mobile node via the new sub-network router
`indicating that the new care-of address binding has been
`created, and synchronizing a transfer of old care-of address
`data packets from the base node to the mobile node.
`
`[0013] Advantages of the invention include a faster hand-
`off wherein the number of data packets that are lost during
`a disruption in data transfer can be minimized or eliminated.
`Moreover, the invention provides a more eflicient handoff
`since no additional network bandwidth is required during the
`disruption duration. Yet another advantage is that the inven-
`tion does not require the establishment and maintenance of
`simultaneous bindings. Other advantages of the invention
`will become apparent from the following description and the
`claims.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0014] A more detailed understanding of the method and
`system of the present invention may be had by reference to
`the following detailed description when taken in conjunction
`with the drawings, wherein:
`
`[0015] FIG. 1 illustrates the flow of data packets in a
`wireless access network;
`
`[0016] FIG. 2 illustrates the registration of a mobile
`device in a wireless access network;
`
`[0017] FIGS. 3A & 3B illustrate the flow of data packets
`during a handoff in Mobile IPv4.
`
`[0018] FIGS. 4A & 4B illustrate the flow of data packets
`during a handoff in Mobile IPv6 where route optimization is
`used;
`
`[0019] FIGS. 5A & 5B illustrate the flow of data packets
`during a handoff in Mobile IPv6 where no route optimization
`is used;
`
`[0020] FIGS. 6A & 6B illustrate the flow of data packets
`during a smooth handoff in Mobile IPv4 where route opti-
`mization is used;
`
`[0021] FIGS. 7A & 7B illustrate the flow of data packets
`during a fast handoff in Mobile IPv4 where multicasting is
`uscd;
`
`[0022] FIGS. 8A & 8B illustrate the flow of data packets
`during a fast handoff in Hierarchical Mobile IPv4;
`
`[0024] FIG. 10A & 10B illustrate the flow of data packets
`during a fast handoff in Hierarchical Mobile IPv6 where
`route optimization is used;
`
`[0025] FIGS. 11A & 11B to 15A& 15B illustrate the flow
`of data packets during a handoif in Mobile IPv4 according
`to some embodiments of the invention where no route
`
`optimization is used, and the mobile device is capable of
`simultaneously accessing two wireless networks;
`
`[0026] FIGS. 16A & 16B to 17A& 17B illustrate the flow
`of data packets during a handoff in Mobile IPv4 according
`to some embodiments of the invention where no route
`
`optimization is used, and the mobile device is capable of
`accessing only a single wireless network at a time;
`
`[0027] FIGS. 18A & 18B to 22A& 22B illustrate the [low
`of data packets during a handoff in Mobile IPv4 according
`to some embodiments of the invention where route optimi-
`zation is used, and the mobile device is capable of simul-
`taneously accessing two wireless networks;
`
`[0028] FIGS. 23A & 23B to 24A & 24B illustrate the flow
`of data packets during a handoff in Mobile IPv4 according
`to some embodiments of the invention where route optimi-
`zation is used, and the mobile device is capable of accessing
`only a single wireless network at a time;
`
`[0029] FIGS. 25A & 25B to 29A & 29B illustrate the flow
`of data packets during a handoff in Hierarchical Mobile IPv4
`according to some embodiments of the invention where the
`route optimization is not used and the mobile device is
`capable of simultaneously accessing two wireless networks;
`
`[0030] FIGS. 30A & 30B to 31A & 31B illustrate the flow
`of data packets during a handoff in Hierarchical Mobile IPv4
`according to some embodiments of the invention where
`route optimization is not used and the mobile device is
`capable of accessing only a single wireless network at a
`time;
`
`[0031] FIGS. 32A & 32B to 36A & 36B illustrate the flow
`of data packets during a handoff in Mobile IPv6 according
`to some embodiments of the invention where route optimi-
`zation is not used and the mobile device is capable of
`simultaneously accessing two wireless networks;
`
`[0032] FIGS. 37A & 37B to 38A & 38B illustrate the flow
`of data packets during a handoff in Mobile IPv6 according
`to some embodiments of the invention where no route
`optimization is used and the mobile device is capable of
`accessing only a single wireless network at a time;
`
`[0033] FIGS. 39A & 39B to 43A & 43B illustrate the flow
`of data packets during a handoff in Mobile IPv6 according
`to some embodiments of the invention where route optimi—
`zation is used and the mobile device is capable of simulta-
`neously accessing two wireless networks;
`
`[0034] FIGS. 44A & 44B to 45A & 45B illustrate the flow
`of data packets during a handoff in Mobile IPv6 according
`to some embodiments of the invention where route optimi-
`zation is used and the mobile device is capable of accessing
`only a single wireless network at a time;
`
`[0023] FIGS. 9A & 9B illustrate the flow of data packets
`during a fast handoff in Hierarchical Mobile IPv6 where no
`route optimization is used;
`
`[0035] FIGS. 46A & 46B to 50A& 50B illustrate the flow
`of data packets during a handoff in Hierarchical Mobile IPv6
`according to some embodiments of the invention where
`
`

`

`US 2003/0018810 A1
`
`Jan. 23, 2003
`
`route optimization is not used and the mobile device is
`capable of simultaneously accessing two wireless networks;
`and
`
`[0036] FIGS. 51A & SIB to 52A & 52B illustrate the flow
`of data packets during a handoff in Hierarchical Mobile IPv6
`according to some embodiments of the invention where the
`mobile device is capable of accessing only a single wireless
`network at a time.
`
`DETAILED DESCRIPTION OF THE DRAWINGS
`
`[0037] Following is a detailed description of the drawings
`wherein reference numerals for like and similar elements are
`
`carried forward. For purposes of this description, a “net-
`work” refers to a wireless access network such as the Global
`
`System for Mobile Communication (GSM) that is capable of
`connecting let users therein to the Internet. A“sub—network”
`refers to a smaller portion of the network through which a
`network connection may be established. Also,
`the terms
`“connected” and “connection,” and “attached” and “attach—
`ment” may be used interchangeably to mean a wireless link
`to a network or sub-network.
`
`[0038] Embodiments of the invention provide a system
`and method for performing seamless handoff in a mobile
`networking environment. In some embodiments, the handoff
`involves a mobile node being notified that a connection with
`an old wireless sub—network will be discarded within a
`
`predetermined amount of time. The mobile node thereafter
`obtains a new care-of address from a new wireless sub-
`
`network, and sends a request message to a base node (e.g.,
`home agent) requesting a new binding. The base node
`creates a new care-of address binding and issues a reply
`message to the mobile node indicating that the new care-of
`of address binding has been created. The transfer of old
`care-of address data packets from the base node to the
`mobile node is thereafter synchronized to achieve a seamless
`handoff.
`
`[0039] As mentioned previously, Mobile IP is an extension
`of IP and is supported by both IPv4 and IPv6. A detailed
`description of Mobile IP support in IPv4 can be found in “IP
`Mobility Support,” C. Perkins, ed., IETF RFC 2002, Octo—
`ber 1996. Likewise, see Johnson, D., B., Perkins, C.,
`“Mobility Support in IPv6,” Internet draft, draft-ietf—mo-
`bileip-ipv6-12.txt, Work in progress, April 2000,
`for a
`detailed description of Mobile IP support in IPv6.
`
`[0040] Hierarchical Mobile IP is an extension of Mobile IP
`designed to handle regional traffic. Support for Hierarchical
`Mobile IP in IPv4 and IPv6 is described, respectively, in
`Gustafsson E., Jonsson A., Perkins C., “Mobile IP Regional
`Registration,” Internet draft, draft-ietf-mobileip-reg-tunnel-
`02.tXt, Work in progress, March 2000; and El Malki K.,
`Soliman H., “Hierarchical Mobile IPv4/v6 and Fast Hand—
`off,” Internet draft, draft-elmalki-soliman-hmipv4v6-00.txt,
`Work in progress, March 2000.
`
`in IPv4, or Mobile IPv4, is
`[0041] Mobile IP support
`substantially transparent to the transport and higher layer
`protocols (e.g., TCP) and does not require any significant
`changes to Internet hosts and routers that are currently being
`used. The key feature of Mobile IPv4 is that all the func-
`tionality required for processing and managing mobility
`information are embedded in well-defined entities: the home
`
`agent (HA), foreign agent (FA), and mobile node (MN).
`
`[0042] The home agent is a node, typically a router, on the
`home network that effectively allows the mobile node to be
`reachable by the rest of the Internet at its home address, even
`when the mobile node is not attached to its home network.
`
`The foreign agent is a node, also typically a router, on a
`foreign network that can assist the mobile node in receiving
`data packets delivered to the care-of address. The home
`agent and the foreign agent are often referred to as mobility
`agents, which is a general term for nodes that provide
`mobility support services to the mobile node.
`
`[0043] The mo