llllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllilll
`USOO5159592A
`
`[11] Patent Number:
`
`5,159,592
`
`[45] Date of Patent:
`
`Oct. 27, 1992
`
`“Implementation Of A Dynamic Address Assignment
`Protocol In A Local Area Network".
`Data Communications, vol. 16, No. 12, Nov. 1987, New
`York US, pp. 209-225; D. Retz: “TCP/IP: DOD suite
`marches into the business world’’.
`‘
`“Intemet Protocol DARPA Internet Program Protocol
`Specification”, Sep. 1981, Information Sciences Insti-
`tute, University of Southern CA, Marina del Rey, Calif.
`90291.
`~
`“Infrared Microbroadcasting Network For In—House
`Data Communication”, F. Gfeller. IBM Technical Dis~
`closure Bulletin, vol. 24, No. 3, Jan. 1982.
`
`Primary Ex‘aminer-Douglas W. Olms
`Assistant Examiner-——Alpus H. Hsu
`Attorney. Agent, or Firm-—Perman & Green
`
`ABSTRACT
`[57]
`Apparatus and method for managing bidirectional
`transmission of information between a wired network
`and at least one mobile communication unit (10) in wire-
`less communication with the wired network. The wired
`network is of the type wherein users of the network are
`each assigned a unique network address such as in, for
`example, a TCP/IP network. In accordance withthe
`invention there is provided a local gateway (16) cou-
`pled between a wireless LAN and the wired network
`for communication with a mobile communication unit.
`There is also provided a global gateway (18) coupled to
`the local gateway and to remote users of the network.
`The global gateway functions to maintain a plurality of
`network addresses and, in response to a request for an
`assignment of a network address from the mobile com-
`munication unit, assigns one of the plurality of network
`addresses to the requesting mobile communication unit.
`The global gatewayalso buffers and routes data re-
`ceived from a remote user, the data being directed to an
`addresss corresponding to the assigned network ad-
`dress, to the’ mobile communication unit having the
`assigned address.
`
`20 Claims, 5 Drawing Sheets
`
`FOREIGN PATENT DOCUMENTS
`0182417
`5/1986 European Pat. Off.
`.
`0328100
`8/1989 European Pat. Off.
`.
`»WO88/07794 10/1988 PCT Int‘! App].
`.
`OTHER FUBLICATIONS
`IEEE Transactions On Communications, vol. 38, No. 8,
`Aug. 1990, New York, pp. 1272-1280; D. J. Goodwin:
`“Cellular Packet Communications".'
`10th Conference On Local Computer Networks, Oct.
`1985, New York, US pp. 149—l57 W. M. Loucks et al.:
`
`
`
`Page 1 of 12
`
`Verizon Exhibit 1019
`
`United States Patent ‘[19]
`Perkins
`
`[54] NETWORK ADDRESS MANAGEMENT FOR
`A WIRED NETWORK SUPPORTING
`WIRELESS COMMUNICATION TO A
`PLURALITY OF MOBILE USERS
`
`Inventor: Charles E. Perkins, Peekskill, N.Y.
`[75]
`{73] Assignee:
`International Business Machines
`Corporation, Armonk, N.Y.
`[21] Appl. No.: 505,592
`[22] Filed:
`Oct. 29, 1990
`
`1m.c1.s ................_........... 1-104.1 3/24; H04B 7/00
`(51)
`[52] u.s.c1. ................................ 370/ss.7;37o/35.13;
`370/94.1; 370/95.1
`[53] Field ofSearcl1 ..................... .. 370/60, 35.1, 85.2,
`_
`370/853, 85.7, 85.13, 94.1, 94.3, 95.1;
`340/8255, 825.51; 455/39, 68, 53.1, 54.1, 54.2,
`55.1, 56.1
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`2/1987 Jennings ...................... 364/200
`4,644,461
`370/94. 1
`5/1987 Kirchner et al.
`4,665,519
`340/825.03
`4.706.081 ll/1987 Hart ‘cl al.
`..
`364/200
`4,750,109
`6/1988 Kita
`4,807,222 2/1989 Amilay .......
`4,809,257
`2/1989 Gantenbein e
`.
`4.893.307
`1/1990 McKay et al.
`4,914,652 4/1990 Nguyen ..........
`5.014.345
`5/1991 Comroe et al.
`5,029,183
`7/1991 Tymcs ........
`5,040,175
`8/1991 Tuch et al.
`.
`5,068,916 '11/1991 Harrison ct al.
`
`
`
`.......
`
`.
`
`

`
`U.S. Patent
`
`Oct. 27, 1992
`
`Sheet 1 of 5
`
`5,159,592
`
`I
`FIG.
`(PRIORART)
`
`HOST TYPE A
`
`APPLICATION APPLICATION
`PRO HI ‘
`PROGRAM
`
`MAIL
`APPLICATION
`
`APPLICATION
`PROGRAM
`
`'
`
`APPLICATION
`PROTOCOL
`.
`NATWE
`FTP I T NET
`A - T”
`5
`EL
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`OPTIONAL
`
`OTHER
`
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`HOST-HOST
`PROTOCOL
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`, s PROTOCOLS U822)
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`AANET ACCESS
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`
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`'
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`DON STANARD
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`X
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`
`B
`TERMINAL
`
`A
`TERMINAL
`
`HOST
`TYPE 8
`
`HOST
`TYPE c
`
`I
`
`Page 2 of 12
`
`

`
`U.S. Patent
`
`Oct 27, 1992
`
`Sheet 2of 5
`
`5,159,592
`
`n23
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`
`Page 3 of 12
`
`
`

`
`US.‘ Patent
`
`Oct. 27, 1992
`
`Sheet 3 of 5
`
`5,159,592
`
`FIGS
`
`
`
`
`
`TRANSMIT WIRELESS
`MESSAGE REQUESTING
`SERVICE ,
`ID
`
`
`
`
`FORWARD BUFFERED ’
`PACKETS
`IF ANY.
`
`FROM GL’oaAL
`I
`A WAY :3 TO
`I MOBILE UNIT I0
`
`
`
` ASSIGN PSEUDO-
`
`
`IP ADDRESS TO
`
`
`
`
`
`Page 4 of 12
`
` TRANSMIT
`
`
`
`
`
`
`
`ASSIGNED
`PSEUDO- IP
`ADDRESS TO
`MOBILE UNIT
`IO AND LOCAL
`GATEWAY I6
`
`
`
`

`
`U.S. Patent
`
`Oct. 27, 1992
`
`Sheet 4 of 5
`
`5,159,592
`
`@ FIG. 4
`
`‘ TRANSMIT
`RESUME
`SERVICE
`MESSAGE
`
`
`
`
`LOCAL“ GATEWAY I6
`INFORMS GLOBAL
`GATEWAY I8
`
`FORWARD BUFFERED
`PACKETS IF ANY,
`"FROM GLOBAL
`GATEWAY I8 TO
`
`
`MOBILE UNIT IO
`
`
`
`
`BUFFER PACKETS
`AT LOCAL
`' I GATEWAY
`I6
`
`
`
`-
`
`I
`
` Yés
`Nomry GLOBAL
`GATEWAY, PURGE
`QUFFERED DATA
`
`I
`
`
`
`
`YES
`DELIVERFACKETS
`TO MOBILE UNITS
`I0
`
`Page 5 of 12
`
`

`
`* U.S. Patent
`
`Oct. 27, 1992
`
`Sheet 5 of 5
`
`5,159,592
`
` FIG. 5
`
`
`
`
`NOTIFY LOCAL GATEWAY IS
`(AND GLOBAL GATEWAYIBI
`OF TERMINATION
`
` MAINTAIN ASSOCIATION
`
`BETWEEN PSEUDO-IP
`ADDR.AND MOBILE
`
`UNIT ID.
`
`
`
`DEALLOCATE PSEUDO-TIP
`BUFFER AT GLOBAL
`ADDRESS, RETURN IP
`GATEWAY I8 ANY PACKETS
`
`
`ADDRESS TO POL
`AQJRESSED TO PSEUDO-'
`IP ADDR
`
`
`
`
`
`
`
`NAME
`
`INQUIRY
`ASSOCIATED
`
`FAILS
`WITH REGISTERED
`. P ADIRES ,
`I
`
`.
`?
`I
`
`
`
`
`REMOTE USER sewn: DATA
`RETURN PSEUDO=~I'P
`ADDRESS TO REMOTE
`TO PSEUDO-IP ADDRESS
`USER
`VIA GLOBAL GW/I8 AND
`
`
`LOCAL. GW I6
`_
`
`
`
`
`Page 6 of 12
`
`

`
`2
`the Gateway to Gateway Protocol (GGP) to
`merit
`coordinate signalling and other internet control infor-
`mation.
`The Internet protocols were originally developed
`with an assumption that users, each of which is assigned
`a unique Internet address, would be connected to the
`network at fixed locations. However, for portable and
`handheld computers the movement, or migration, of
`users about the network is typically the rule rather than
`the exception. As a result, a problem is created in that
`the implicit design assumptions of the Internet protocol
`are violated by this type of usage.
`Other patents of interest include the following. In
`U.S Pat. No. 4,914,652, issued Apr. 3, 1990, Nguyen
`discloses a method for managing data transmissions in a
`single network, but not the routing and delivery of data
`between networks. In U.S. Pat. No. 4,750,109, issued
`Jun. 7, 1988, Kits teaches methods for allocating com-
`munication channels. In U.S. Pat. No. 4,706,081, issued
`Nov. 10, 1987, Hart et al. teach the merging of physi-
`cally separate networks into a single logical network at
`a level below the addressing considerations required to
`affect the Internet protocols. In U.S. Pat. No. 4,644,461,
`issued Feb. 17, 1987, Jennings discloses a computer
`architecture including cross-bar and queue structures
`for routing tokens within the computer.
`In commonly assigned U.S. Pat. No. 4,809,257, issued
`Feb. 28, I989, entitled “Hierarchical Distributed Infra-
`red Communication System” Gantenbein et al. disclose
`the integration "of workstations into an IR network.
`FIG. 1D shows a system that includes a gateway 23 to
`another network such as a ring or a bus local area net-
`work, or to a cable-bound subnetwork.
`Other patents of interest include the following. In
`U.S. Pat. No. 4,807,222, issued Feb. 21, 1989, N. Amitay
`discloses a wireless network using intelligent interfaces
`for each wired network connection-. The interface is to
`‘ a token bus network.
`In U.S. Pat. No. 4,665,519, issued May 12, 1987, T. L.
`Kirchner et al. disclose the use of VHF FM radio as a
`means of connecting computers and computer peripher-
`als. This patent describes the implementation of an asyn-
`chronous access, token based protocol. In International
`Patent W088/07794, published Oct. 6, 1988, G. Vacon
`discloses the use of a wireless microwave bridge be-
`tween two networks utilizing a CSMA/CD protocol.
`In IBM Technical.Disclosure Bulletin Vol. 24 No. 8,
`I982 F. Gfeller describes general control principles of
`an infrared wireless communication network incorpo-
`rating multiple base stations and multiple mobile com-
`puters. Transmission occurs over the wireless IR me-
`dium using different frequencies for the uplink and the
`downlink.
`.
`What is not taught by this prior art, and what is thus
`an object of the invention to provide, is method and
`apparatus for coupling wireless migrating usersto a
`network operating in accordance with the TCP/IP
`type-protocol.
`SUMMARY OF THE INVENTION
`
`The foregoing problems are overcome and other
`advantages are realized by method and apparatus that
`manages mobile communication unit address assign-
`ments and which assumes responsibility for the routing
`of all packets destined for the mobile units. Addition-
`ally, alocal mobile unit gateway service is provided on
`every network or LAN in order to route packets to the
`
`50
`
`I
`
`5,159,592
`
`NETWORK ADDRESS MANAGEMENT FOR A
`WIRED NETWORK SUPPORTING WIRELESS
`COMMUNICATION TO A PLURALITY OF
`MOBILE USERS
`
`FIELD OF THE INVENTION
`This invention relates generally to communication
`method and apparatus and, in particular, to method and
`apparatus for managing network address usignments in
`a network that includes mobile users.
`BACKGROUND OF THE INVENTION
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`Commonly assigned U.S. Pat. No. 4,893,307, issued
`Jan. 9, 1990, “Method and Apparatus for Linking SNA
`Terminals to an SNA Host Over a Packet Switched
`Communications Network”, D. B. McKay, R. M. Mor-
`ten and _M. P. Marsili, describes ‘an architectural model
`of the Department of Defense (DoD) protocol suite.
`Referring to FIG. I the architecture is said to be similar
`to, but not identical with, the International Standards
`Organization (ISO) Open Systems
`Interconnection
`(OSI) architecture.
`A Defense Data Network (DDN) standard estab-
`lishes criteria for an Internet Protocol (IP) which sup-
`ports the interconnection of communication LANs. It
`introduces the Internet Protocol’s role and purpose,
`defines the services provided to users, and specifies the
`. mechanisms needed to support those services. The stan-
`dard also defines the services required of the lower
`protocol layer, describes theupper and lower inter-
`faces, and outlines the execution environment services
`need for implementation.
`A Transmission Control Protocol (TCP) is a trans-
`port protocol providing connection-oriented, end-to-
`end reliable data transmission in packet-switched com-
`puter LANs and intemetworks.
`The lntemet Protocol (IP) and the Transmission ~
`Control Protocol‘ (TCP) are mandatory for use in all
`DoD packet switching networks which connect or
`have the potential for utilizing connectivity across net-
`work or subnetwork boundaries. Network elements,
`such as hosts, front-ends, gateways, etc., within such
`networks which are to be used for internetting must
`implement TCP/IP.
`The lntemet Protocol is designed to interconnect
`packet—switched communication LANS to form an in-
`temetwork. The IP transmits blocks of data, called
`internet datagrams,
`from sources .to destinations
`throughout the intemet. Sources and destinations are
`hosts located on either the same subnetwork or con-
`nected»LANs. The IP is purposely limited in scope to
`provide the basic functions necessary to deliver a block
`of data. Each internet datagram is an independent entity
`unrelated to any other internet datagrams. The I!’ does
`not create connections or logical circuits and has no
`mechanisms to promote data reliability, flow control,
`sequencing, or other services commonly found in vir-
`tual circuit protocols.
`The DDN standard specifies a host ll’. As defined in
`the DoD architectural mode,
`the Intemet Protocol
`resides in theinternetwork layer. Thus, the IP provides
`services to transport layer protocols and relies on the
`services of the lower network protocol. In each gate-
`way, a system interconnecting two or more LANS, an
`IF resides above two or more LANS protocol entities.
`Gatewaysimplement the internet protocol to forward
`datagrams between networks. Gateways also imple-
`
`S5
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`65
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`Page 7 of 12
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`mobile units coupled to the network. In accordance
`with the invention a network address, such as an Inter-
`net address, that is associated with a particular mobile
`unit encodes a network not physically embodied any-
`where, referred to herein as a ‘pseudo-network’. Rout-
`ers of data packets are instructed to forward packets,
`destined for the designated network, to the global gate-
`way. The global gateway subsequently executes meth-
`ods, described in detail, to accomplish the packet trans-
`mission to the target mobile unit. The Internet addresses
`for each mobile-unit are allocated and deallocated from
`a pool of addresses available for the pseudo-network. A
`‘permanent’ assignment of a pseudo-address to a mobile
`unit is also within the scope of operation of the global
`gateway.
`That is, the invention relates to apparatus and method
`for managing bidirectional transmission of information
`between a wired network and at least one mobile com-
`munication unit
`in wireless communication with the
`wired network. The wired network is of the type
`wherein users of the network are each assigned a unique
`network address such as in, for example, a TCP/IP
`network.
`In accordance with the invention there is
`provided a local gateway coupled between a wireless
`network and the wired network for communicating
`with a mobile communication unit. There is also pro-
`vided a global gateway coupled to the local gateway
`and to remote users of the network. The global gateway
`functions to maintain a plurality of network addresses 30
`and,
`in response to a request for an assignment of a
`network address from the mobile communication unit,
`assigns one of the plurality of network addresses to the
`requesting mobile communication unit. The global gate-
`way also buffers and routes data received from a remote
`user to the mobile communication unit having the as-
`signed address, the data being directed to an address
`corresponding to the assigned network address.
`BRIEF DESCRIPTION OF THE DRAWING
`The above set forth and other features of the inven-
`tion are made more apparent in the ensuing Detailed
`Description of the Invention when read in conjunction
`with the attached Drawing, wherein:
`FIG. I is a prior an architectural diagram of the
`Defense Data Network;
`FIG. 2 is a block diagram showing a global gateway
`coupled to a plurality of local gateways each of which
`may reside on a separate wired/wireless LAN; and
`FIGS. 3-6 are each a flowchart depicting various
`interactions between mobile units, a global gateway, a
`local gateway and remote users.
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`4
`Communication between mobile units 10 is through
`the header stations 12 via the LAN 14. Communication
`between the header stations 12 is primarily via the LAN
`14.
`One suitable embodiment for the header stations 12
`and the mobile units 10 is disclosed in commonly as-
`signed U.S. patent application Ser. No. 07/605,052, filed
`Oct. 29, 1990, entitled “Transceiver for Extending a
`CSMA/CD Network for Wireless Communication" by
`P. Hortensius and H. Winbom.
`The network 10 conforms, in the presently preferred
`embodiment of the invention, to a network protocol
`known as the Transport Control Protocol/Intcmet
`Protocol (TCP/IP), as described in detail in “Intemet-
`working with TCP/IP Principles, Protocols, and Ar-
`chitectures" by Douglas E. Comer, Prentice Hall, N.J.,
`I988. The teaching of the invention should, however,
`not be construed to be limited to only such a network
`protocol, but may be employed with any protocol that
`encodes a LAN identification into a network address.
`In accordance with an aspect of the invention each of
`the LANS 2 and 3 includes at least one local gateway
`(GW) 16 for coupling the mobile units 10, via the
`header stations 12 and the LAN 14, to a global gateway
`18. The global gateway 18 is also coupled to remote
`network users who may be dispersed over a wide geo-
`graphic area. The local gateways 16 may each be an
`“intelligent” header station or may be a separate dedi-
`cated network entity as shown. The global gateway 18
`is preferably a data processor having suitable network
`adapters and an archival facility for storing packets
`addressed to particular ones of the mobile units 10 dur-
`ing.a time when the mobile units are not in contact with
`the wireless network. The data ‘processor that com-
`prises the global gateway 18 includes means for assign-
`ing, maintaining and associating “pseudo-IP” addresses
`with particular ones of the mobile units 10, in a manner
`to be described.
`An IP address consists of four bytes, or 32 bits, that
`are partitioned into a LAN identification and a Host
`identification. By example, an IP address may have the
`form 123.45.67.12. The first two bytes encode a LAN
`address of 123 (byte l) and 45 (byte 2). The remaining
`two bytes generally encode Host information. There is
`a different Host associated with each LAN. Thus, in the
`example provided Host (12) may have up to 256 IP
`addresses associated therewith, as encoded in the third
`byte.
`~
`In accordance with IP practice each user of the net-
`work is assigned a unique network address. A problem
`solved by the invention relates to the assignment of IP
`addresses to the mobile units 10 which, inherently, do
`not maintain a fixed connection relationship with the
`network. This problem is solved, as described below, by
`allocating a plurality of IP addresses to the global gate-
`way 18. These allocated II’ addresses are subsequently
`dynamically assigned by the global gateway 18 to re-
`questing mobile units 10, either on a temporary basis
`(one network session) or on a permanent, extended,
`basis (several network sessions). At the termination of a
`session or sessions the IP address is returned to the
`global gateway 18 for subsequent reassignment to the
`same or another mobile unit 10. These assigned 1}’ ad-
`dresses are referred to herein as pseudo-IP addresses
`and represent a dynamic pseudo-network.
`In accordance with the invention a network address,
`such as an Internet address that is associated with a
`particular mobile unit 10 encodes a network not physi-
`
`5,159,592
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`$0
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`55
`
`Referring to FIG. 2 there is illustrated a communica-
`tions area network 1. _The network 1 includes one or
`more local area networks (LANS) 2 and 3. Each LAN
`includes a wireless network comprised of a plurality of .
`mobile communication units (MU) 10 in wireless com- 60
`munication with a plurality of header stations (HS) 12.
`Each of the header stations 12 is bidirectionally coupled
`to a wired LAN 14. In the presently preferred embodi-
`ment of the invention the wireless medium is comprised
`of infrared (IR) radiation, although other embodiments 65-
`may employ an RF wireless medium. Each of the
`header stations 12 has associated therewith a communi-
`cations coverage area, or cell 11.
`
`‘
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`the local gateway 16 instead begins to relay packets
`from those sessions, the packets being stored and for
`warcled by the global gateway 18. Likewise, when the
`global gateway 18 receives the request, it compares the
`incoming mobile unit 10 identifier, or serial number,
`with a list of serial numbers to purge any stored packets .
`that might have been saved for the mobile unit 10.
`If the global gateway 18 returns to the newly acti-
`vated mobile unit 10 a permanently registered pseudo-
`IP address, the global gateway 18 may also begin for-
`warding mcssagcs and other stored data to that mobile
`unit 10, through the local gateway 16. This data is origi-
`nally received from the network during a period that
`the mobile unit 10 associated with the permanently
`registered pseudo-IP address is inactive. This received
`data is buffeted by the global gateway 18 during this
`period for subsequent delivery to the mobile unit 10
`when the mobile unit 10 once more becomes active.
`
`5
`cally embodied anywhere and which is referred to
`herein as the pseudo-network. In accordance with an
`aspect of the invention the global gateway 18 “owns”
`all of associated pseudo-IP addresses and allocates and
`deallocates the pseudo-IP addresses as the mobile units 5
`10 enter and leave the LANs 2 and 3. A mobile unit 10
`typically maintains its assigned pseudo-IP address until
`it is turned off, or until the network session is actively
`terminated. Upon specific request by a particular one of
`the mobile units 10 a ‘permanent’ association is made
`between a mobile unit 10 and one of the pseudo-IP
`addresses. This permanent assignment is preferably not
`permanent‘ in the sense that the mobile unit 10 would
`own the address for all time, in that the available pool of
`pseudo-IP addresses could quickly be consumed. Pref- I5
`erably, the permanent assignment is only sufficiently
`long so as to accomplish a specific task which may
`require a plurality of separate network sessions. The
`global gateway 18 is responsible for maintaining the
`Resumption of Service (FIG. 4)
`permanent pseudo-IP association, even though a local
`When a mobile unit 10 enters a cell 11 and indicates
`gateway 16 may also maintain the relationship for so
`long as the mobile unit 10 stays in Contact with the local
`that it is to continue a previous network connection, it
`gateway 16. The global gateway 18 also buffers any
`sends a message to the local gateway 16, via a header
`packetsvdestined for a particular mobile unit 10 during
`station 12. The message causes the local gateway 16 to
`any time that the mobile unit 10 is out of touch with the
`notify the global gateway 18, and possibly a previous
`"network, such as the mobile unit 10' which is not lo-
`local gateway 16, that the mobile unit 10 has migrated
`cated within one of the communication cells 11.
`to the new cell 11. The local gateway 16 requests from
`A function of the local gateway 16 is to deliver data
`the global gateway 18 all packets currently queued for
`packets, v'ia the wireless downlink, to known mobile
`the mobile unit 10 pseudo-IP address and delivers the
`units 10 within its associated cell 11. If a mobile unit 10
`packets over the downlink wireless channel. The global
`is out of touch withothe wireless network no other local
`gateway 18 thereafter forwards to the local gateway 16
`gateway 16 participates in the transmission of packet
`all future packets addressed to the pseudo-IP address
`destined for_that mobile unit 10.
`_-
`associated, either temporarily or permanently, withthe
`Being out of touch for a predetermined period of time
`‘mobile unit 10. Any remote users having knowledge of
`causes the mobile unit’s local gateway 16 to notify the
`the pseudo-IP address may negotiate an optimal route
`global gateway 18, via LAN 14, that the mobile unit 10
`to the local gateway 16, employing known IP proto-
`is no longer a member of the group of mobile units
`cols. In this regard the local gateway 16 assumes re-
`associated with the local gateway 16. In response to
`sponsibility for breaking the route if and when the mo-
`being notified of the disappearance of the mobile unit 10
`bile unit 10 migrates out of the local gateway’s 16 cell
`the global gateway 18 terminates the forwarding of 40
`area.
`packets, through the local gateway 16, that are directed
`to the inactive mobile unit.
`‘
`.
`To avoid an unstable situation that may arise if the
`local gateway 16 purged internal data structures of all
`The following communication operations are now
`knowledge of a mobile unit 10 as soon as the mobile unit
`described in detail: (a) initialization of a mobile unit 10
`10 was determined to be out of touch, such as might
`and the initialization of network routing for the mobile 45
`' arise if a- particular mobile unit 10 wandered along the
`unit 10; (b) resumption of service to a mobile unit 10; (c)
`periphery of a cell 11; the local gateway 16 temporarily
`termination of service to a mobile unit 10; (d) delivery
`queues packets destined for the mobile units 10 within
`of packets to a mobile unit 10; and (e) transmission of
`the local gateway’s service area (or LAN). If the mobile
`packets from a mobile unit 10.
`unit 10 returns to the local gateway’s service area before
`Initialization (FIG. 3)
`the queuing time limit expires the local gateway 16
`When a mobile unit 10 first enters a LAN cell 11 it
`delivers the queued packets to the mobile unit 10. As
`such, so long as the mobile unit 10 returns to the service
`performs the following operations. The newly arrived
`area within a predetermined time interval
`the local
`mobile unit 10 first directs a message, via a header sta-
`gateway is not required to notify the global gateway 18
`tion 12, to the local gateway 16. This message requests
`that the local gateway 16 has relinquished responsibility
`the local gateway 16, through the global gateway 18, to
`for the mobile unit 1!).
`activate a pseudo-IP address for the mobile unit 10. The
`mobile unit 10 identities itself by transmitting a unique
`identifier, such as its serial number, that is permanently
`stored within a memory of the mobile unit 10. The
`requested pseudo-[P address may be either a pseudo-IP
`address that is permanently assigned to that mobile unit
`10, or a dynamically allocated pseudo—IP address that
`the global. gateway 18 selects from a pool of such ad-
`dresses.
`The local gateway 16 determines from the mobile
`unit's request that the mobile unit 10 does not expect to
`resume service from any previous sessions. Otherwise,
`
`50
`
`55
`
`60
`
`65
`
`Termination of Service (FIG. 5)
`If a mobile unit 10 intends to terminate incoming
`network service in an orderly manner it notifies the
`local gateway 16 via a header station 12. The local
`gateway 16 notifies the global gateway 18 that the mo~
`bile unit’s pseudo-IP address may be deallocated. The
`global gateway 18 also purges all stored information
`relating to the mobile unit 10. The global gateway 18
`does not purge the association between the pseudo-IP
`address and the particular mobile unit 10 if the mobile
`
`Page 9 of 12
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`8
`them as data within new IP packets destined for the
`local gateway 16. The local gateway 16, which may be
`one of the header stations 12, accomplishes further
`transmission of the data to the target mobile unit by
`using a 5 non-Internet protocol. That
`is, by whatever
`protocol is established for the wireless network commu-
`nication. Any packet transmitted to a pseudo-IP address
`using IP would be routed to the global gateway 18, thus
`negating the use of the pseudo-IP address. Indeed, the
`problem solved by the use of the invention is that of
`encoding the logical network number inside the IP
`address when the logical network number is associated
`with a mobile data communication entity.
`If instead a remote user is executing software to en-
`able special handling of pseudo-IP addresses, the re-
`mote user is, enabled to deliver the mobile unit 10 pack-
`ets directly to the mobile unit‘s local gateway 16, with-
`out requiring the intervention of the global gateway 18.
`This mode of operation requires the local gateway 16 to
`inform the remote user before the local gateway 16
`terminates service for the mobile unit 10, as in the case
`when the mobile unit becomes inactive or migrates out
`of the cells 11 served by the local gateway 16.
`In either situation described above the remote user is
`required to send mobile unit 10 data packets to the
`global gateway 18 for storage while the mobile unit 10
`_ is inactive.
`Transmission» from a Mobile Unit 10 to a Remote User
`
`Transmission of packets from a mobile unit 10 to a
`remote user is accomplished using conventional 11’ ad-
`dressing techniques. However, if the remote computer
`is known to be able to operate with multiplexed pseudo-
`IP address assignments, as described below, the mobile
`unit 10 encapsulates outgoing data within a header
`within the TCP packet to ensure that the remote user
`becomes aware of which specific mobile unit 10 is the
`source of the data.
`Having described the five communication operations
`listed above other aspects of the invention are now
`described, specifically multiple interactive global gate-
`ways and multiplexed, or shared, pseudo~IP addresses.
`
`,
`
`Multiple Interactive Global Gateways
`A single global gateway 18 may become a bottleneck
`if it is simultaneously managing many separate Internet-
`work mobile unit 10 sessions. This is unlikely, however,
`unless there are many remote users having no special
`knowledge of the special nature of the pseudo-IP ad-
`dress, but which nevertheless maintain active communi-
`cations with the mobile units 10. To eliminate this po-
`tential bottleneck several global gateways 18 are em-
`ployed to partition the set of all mobile units 10 into
`disjoint subsets. This may be accomplished in either of
`two ways. A first method employs different “pseudo-
`network” numbers, one per global gateway I8. Altcma-
`tively, each global gateway 18 maintains and shares
`with its peers a consistent set of tables describing the
`current routing information, or location, for each mo-
`bile unit 10. If each global gateway 18 has separate
`pseudo-networks,
`then IP routing will automatically
`send IP packets to the correct global gateway 18 that is
`primarily responsiblefor a mobile unit. Even so, the
`global gateways 18 must cooperate with one another if
`free movement and access to the same set of remote
`hosts is to be accomplished.
`
`7
`unit 10 has previously requested and received a penna-
`nently associated pseudo-IP address.
`
`5,159,592
`
`l0
`
`l5
`
`20
`
`25
`
`30
`
`Delivery of Packets to a Mobile Unit 10 (FIG. 6)
`All communication from a remote user to a mobile
`unit 10 employs the pseudo-IP address of the mobile
`unit 10. Fully qualified mobile unit 10 names specify a
`domain for use with network nameservers. By example,
`a mobile unit 10 having an associated name of "C...
`E_Perkins" may be located within a domain designated
`“hawII.np.watson.ibm.com" and thus have the fully
`qualified name “C__E...Perkins.hawII.np.watson.ibm.-
`com". When a remote user initiates a conversation with
`' a mobile unit 10 the remote user typically consults a
`network nameserver configured to send requests for
`specified mobile unit 10 names to a specified mobile unit
`10 global gateway 13. A request for a mobile unit 10
`name fails unless there exists an association registered
`between the mobile unit 10 name and a particular pseu-
`do-lP address.
`,
`Nameserver operation is now described in greater
`detail. If the requested name is associated to a perma-
`nently assigned address,'that address is returned by the
`nameserver even though the associated mobile unit 10 is
`turned off. If the requested name is temporarily regis-
`tered to a pseudo-IP address, that address is returned.
`However, if the name is associated with a previously
`known pseudo-IP address, a predetermined special II‘
`address is returned. The special pseudo~IP address is
`reserved only for this use and is not otherwise ever
`assigned to any mobile unit 10. This reserved address is
`specially handled by theglobal gateway 18 if it is used
`by remote hosts for incoming mail requests Using the
`example given previously the returned IP address may .
`35
`correspond to -123.45.199.12, where 199 corresponds to
`the reserved address.
`If a remote user obtains the pseudo-IP address of a
`registered mobile unit 10, the remote user is enabled to
`send messages, such as mail, to the mobile unit 10, even
`if the mobile unit 10 is inactive. In this case the message
`packets are stored, as previously described, by the
`global gateway 18 until such time as the mobile unit 10
`is active and the packets can be delivered via an associ-
`ated local gateway 16. TCP session requests for the
`mobile unit 10 from the remote user are denied by the
`global gateway 18 unless the mobile unit 10 is active,
`although the session request may be accepted by the
`global gateway 18 when the mobile unit is active but
`merely temporarily “out of touch". However, only
`permanently situated mobile units 10 having a regis-
`tered, permanent IP address may rely on conventional
`IP methods for point-to-point network communica-
`tions.
`A mobile unit 10 delivering a packet to a remote user
`employs conventional methods of network transmission
`and uses the IP address of the remote user.‘A remote
`user, running software having no provisions for mobile
`unit 10 communications, transmits a packet to a mobile
`unit 10 by routing the packet to the global gateway 18,
`' which then relays the packet to the local gateway 16
`that is managing mobile unit 10 network traffic for an
`associated subset of mobile units 10. This operation
`proceeds using a non-IP protocol; however, transmis-
`sion of the packets associated with the nonstandard
`- protocol, between the gateways 18 and 16,
`is accom-
`plished by conventional IP methods.
`In this regard packets bearing the IP address are
`routed to the global gateway 18 which