United States Patent l19J
`Cheung et al.
`
`[54] METHOD AND APPARATUS FOR
`PROVIDING A 3-WAY CONNECTION
`BETWEEN A MOBILE COMPUTING
`DEVICE, A STATIONARY COMPUTING
`DEVICE AND A COMPUTER NETWORK
`
`(75]
`
`Inventors: Roger Yiu Ming Cheung, Scarborough;
`Murray Charles Baker, Toronto;
`David Newton, Concord, all of Canada
`
`(73] Assignee: International Business Machines
`Corporation, Armonk, N.Y.
`
`(21] Appl. No.: 08/755,422
`
`[22]
`
`Filed:
`
`Nov. 22, 1996
`
`[30]
`
`.Foreign Application Priority Data
`
`Jun. 18, 1996
`
`(CA]
`
`Canada ................................... 2179349
`
`Int. Cl.6
`............................. G06F 13/38; G06F 15/17
`[51]
`[52] U.S. CI . .................................. 395/200.8; 395/200.57;
`395/200.66; 370/463
`[58] Field of Search ............................ 395/200.3, 200.57,
`395/200.66, 200.8; 370/401, 338, 402, 463
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`I 1111111111111111 11111 111111111111111 IIIII IIIII IIIII lllll 111111111111111111
`US005953507 A
`[11] Patent Number:
`(45] Date of Patent:
`
`5,953,507
`Sep.14,1999
`
`........................... 370/401
`5,473,608 12/1995 Gagne et al.
`5,550,816
`8/1996 Hardwick et al. ...................... 370/401
`5,572,528 11/1996 Shuen ...................................... 370/402
`2/1998 Doviak et al. .......................... 455/403
`5,717,737
`
`Primary Examiner-Mark H. Rinehart
`or Firm-Edward H. Duffield
`Attorney,
`
`[57]
`
`ABSTRACT
`
`A method and apparatus for providing a rnr,,e-,;v~v connec(cid:173)
`tion between a mobile computing device, a stationary com(cid:173)
`puting device and a computer network. When there i-; an
`established connection between a mobile computing device
`(e.g. a notebook computer) and the stationary computing
`device (e.g. desktop PC) over the wireless communication
`channel (e.g. infrared link), the system operates in BRIDGE
`mode. In BRIDGE mode the system redirects information
`packets in the OSI layer 2 (data link layer). When a notebook
`computer is not attached, the system operates in
`PASSTIIROUGH mode and all non-broadcast message traf(cid:173)
`fic from the Ethernet lAN is filtered by the Ethernet adapter
`based on the network address or group address of the
`desktop PC.
`
`5,159,592 10/1992 Perkins .................................... 370/401
`
`18 Claims, 4 Drawing Sheets
`
`TCP/IP
`PROTOCOL
`
`NETBIOS
`LAN
`REQUESTER
`PROTOCOL
`
`SNA
`3270
`PROTOCOL
`
`NETWARE
`PROTOCOL
`
`I
`
`I 100
`
`r
`
`110
`
`106-1
`
`! "1 06-2
`
`106-3
`
`I
`106-4 I
`
`NDIS2
`MSPFORETHERNET/DOS
`
`102
`
`104
`
`NDIS2
`ETHERNET DEVICE DRIVER
`
`NDIS2
`IRDA DEVICE DRIVER
`
`-
`
`-
`
`-
`
`-
`
`-
`
`- - - -
`
`-
`
`-
`
`- - - - -
`
`-
`
`-
`
`_I
`54
`
`52
`
`ETHERNET
`HARDWARE
`
`10
`
`50/
`
`IRDA 1.1
`HARDWARE
`
`•
`
`6
`
`Ex.1017
`APPLE INC. / Page 1 of 11
`
`

`

`U.S. Patent
`
`Sep.14,1999
`
`Sheet 1 of 4
`
`5,953,507
`
`TCP/IP
`PROTOCOL
`
`NETBIOS
`LAN
`REQUESTER
`PROTOCOL
`
`SNA
`3270
`PROTOCOL
`
`"
`
`106-1
`
`j~
`
`110
`"- ,,
`
`j~ "
`,,
`
`106-2
`
`' "
`
`"
`
`106-3
`
`I
`
`NETWARE
`PROTOCOL
`
`I 100
`i/
`
`. "
`
`106-4
`
`NDIS2
`MSP FOR ETHERNET/ DOS
`
`.
`
`/104
`
`•
`NDIS2
`IRDA DEVICE DRIVER
`
`'
`
`/102
`
`'
`NDIS2
`ETHERNET DEVICE DRIVER
`
`- - - - - - ~ - - - - - - - - - - - - J -
`/52
`'
`IRDA 1.1
`HARDWARE
`
`ETHERNET
`HARDWARE
`
`-
`
`-
`
`-
`
`-
`/ 54
`
`10~
`
`50/
`
`•
`.....__..
`.....___..
`~
`
`FIG.1
`
`Ex.1017
`APPLE INC. / Page 2 of 11
`
`

`

`U.S. Patent
`
`Sep.14,1999
`
`Sheet 2 of 4
`
`5,953,507
`
`,..,.18
`
`10 WIRED
`LAN
`
`HOST ACCESS
`
`HOST COMPUTER
`SYSTEM
`
`22
`
`PRINT
`SERVER
`
`FIG.2
`
`Ex.1017
`APPLE INC. / Page 3 of 11
`
`

`

`U.S. Patent
`
`Sep.14,1999
`
`Sheet 3 of 4
`
`5,953,507
`
`DPC
`,
`- - - - - - - - - - - - - - - - - - - - - - -·
`
`FIG.3
`
`:
`:
`
`1~ t=,
`16 ~ ·
`
`: '\.._v~ MPC:
`
`~ ~ \
`: 12 DPC
`
`18
`
`/
`
`~NTER
`
`HOST ACCESS
`
`HOST COMPUTER
`SYSTEM
`
`22
`
`PRINT
`SERVER
`
`FIG.4
`
`WIRED
`LAN
`
`Ex.1017
`APPLE INC. / Page 4 of 11
`
`

`

`U.S. Patent
`
`Sep.14,1999
`
`Sheet 4 of 4
`
`5,953,507
`
`: OFFICE
`
`' -, DPC
`
`,
`
`\
`
`\
`
`\
`
`\
`
`\
`
`,'
`- - ... - .. -, - - - - .. - .. - - .. - - - - - - _,
`'
`,
`- - - - - - - - - - - - - - - - - - - - - -'-
`: CONFERENCE ROOM
`
`HOST
`COMPUTER SYSTEM
`
`22
`
`FIG.5
`
`Ex.1017
`APPLE INC. / Page 5 of 11
`
`

`

`5,953,507
`
`1
`METHOD AND APPARATUS FOR
`PROVIDING A 3-WAY CONNECTION
`BETWEEN A MOBILE COMPUTING
`DEVICE, A STATIONARY COMPUTING
`DEVICE AND A COMPUTER NETWORK
`
`FIELD OF THE INVENTION
`
`The present invention relates to computer networking,
`and in particular to a method and apparatus for providing a
`three-way connection between a mobile computing device,
`a stationary computing device and a computer network.
`
`BACKGROUND OF THE INVENTION
`
`30
`
`2
`program (MSP) for coupling a mobile PC to a desktop PC
`and a wired computer network.
`According to one aspect of the invention, the three-way
`bridge comprises a program running on the desktop PC that
`5 appears as a LAN hardware adapter device driver to the
`Network Operating System (NOS) of the desktop PC. The
`desktop PC NOS assumes it is communicating with the LAN
`hardware adapter directly.
`The three-way bridge according to the present invention
`10 runs on top of both the device driver for the wireless
`interface adapter and the device driver for the LAN adapter.
`The three-way bridge appears as a NOS to both the wireless
`interface adapter and the LAN hardware adapter. When all
`the connections between the notebook PC, the desktop PC,
`15 and the LAN are active simultaneously, the three-way bridge
`according to the present invention puts both the wireless
`adapter and the LAN adapter into a promiscuous mode.
`During initialization, the three-way bridge will discover the
`node address of the LAN hardware adapter. This address is
`20 used by the NOS on the desktop PC. To discover the node
`address of the notebook PC NOS, the three-way bridge
`program examines the first data that is originated from the
`notebook PC. The program checks the source address and
`the OSI (Open System Interconnection Standard) layer 2
`25 data link layer to determine the node address of the NOS for
`the notebook PC.
`In operation, all traffic originating from the NOS of the
`notebook PC is received by the three-way bridge program.
`The three-way bridge program checks the destination
`address in the OSI layer 2 (i.e. the data link layer) to
`determine if the data is destined for the NOS of the desktop
`PC. If the data is destined for the desktop PC NOS, the data
`is delivered to the desktop PC NOS as though it came from
`the LAN. If the data is intended for both the desktop PC and
`the LAN, e.g. broadcast frames, the data is sent to the LAN
`in addition to the desktop PC. If the data is intended for the
`LAN, the data is sent on to the LAN.
`It is a feature of the three-way bridge program that all
`traffic on the LAN is examined. The three-way bridge
`program checks the destination address in the OSI layer 2,
`i.e. the data link layer, to determine if the data is destined for
`the desktop PC NOS or the notebook PC NOS, or both. If the
`data is not destined to the desktop PC NOS or the notebook
`PC NOS, the three-way bridge program takes no further
`action. If the data is destined to the desktop PC NOS or the
`notebook PC NOS, or both, the three-way bridge program,
`depending on the destination address, sends the data either
`to the desktop PC NOS or the notebook PC NOS, or both.
`The traffic originating from the desktop PC NOS is also
`examined by the three-way bridge program. The bridge
`program checks the destination address in the OSI layer 2
`data link layer to determine if the data is destined for the
`notebook PC NOS or NOS's on the LAN, or both. If the data
`55 is destined for the notebook PC NOS only, the bridge
`program sends the data to the notebook PC. On the other
`hand, if the data is destined for the NOS's on the LAN, the
`three-way bridge program sends the data on to the LAN. If
`the data is destined for both the notebook PC NOS and the
`60 NOS's on the LAN, the program sends the data to both the
`notebook PC as well as the NOS's on the LAN.
`In a further enhancement, the three-way bridge program
`according to the present invention will re-program the LAN
`adapter to take it out of promiscuous mode and put it back
`65 into normal mode with the original node address in order to
`obtain optimal performance when the notebook PC is not
`connected to the desktop PC. In normal mode, the LAN
`
`Local area networks (LAN's) have historically consisted
`of nodes interconnected by physical telecommunications
`media (e.g. coaxial cable, twisted pair wire or fibre optics).
`Recently wireless LAN's, the nodes of which are not
`connected by means of a physical medium, have started to
`appear in the art. These wireless LAN's communicate by
`means of an infrared (IR), radio or other signals. One of the
`benefits of using wireless LAN's is that cabling is not
`required. This is particularly useful for mobile nodes such as
`laptop and notebook computers, PDA's (Personal Digital
`Assistant), and the like. If appropriately equipped with a
`suitable wireless adapter (which includes a transmitter/
`receiver and control card), such as an IR wireless adapter,
`the mobile nodes can move around and remain connected to
`the network, provided they do not move out of range for the
`IR adapter.
`To accomplish a simultaneous three-way connection
`between a notebook PC, a desktop PC and a LAN, there are
`two possible approaches. The first approach involves using
`a router. The Network Operating System (NOS) of the
`desktop PC is provided with a built-in router program and 35
`connected to the Network Operating System (NOS) on the
`LAN. The NOS of the notebook PC is connected to the
`router within the desktop PC NOS. Data in the form of
`information packets from the NOS of the notebook PC
`destined for either the NOS of the desktop PC or the NOS's 40
`on the LAN is first received by the router program on the
`NOS of the desktop PC. Based on the destination informa(cid:173)
`tion contained in the data packet, the router will either send
`the data packet to the NOS of the desktop PC or to NOS's
`on the LAN.
`The second approach is that of the present invention and
`involves using a three-way bridge. The NOS of the desktop
`PC is directly connected to the three-way bridge program on
`the desktop PC. The NOS of the notebook PC is directly
`connected to the same three-way bridge program. The
`NOS's on the LAN are also directly connected to the same
`three-way bridge program.
`The main difference between the router and the three-way
`bridge is that the router redirects data in the OSI (Open
`System Interconnection Standard) layer 3, i.e. the network
`layer, and the three-way bridge redirects data in the OSI
`layer 2, i.e. the data link layer.
`The three-way bridge is preferred in a specific environ(cid:173)
`ment having only one notebook PC, one desktop PC, and a
`LAN. The three-way bridge is preferred over a router due to
`its simplicity in setting up the connections, operation by the
`end-use, and the ease of implementation.
`
`45
`
`50
`
`SUMMARY OF THE INVENTION
`
`The present invention provides a method and apparatus
`for providing a three-way bridge or mobile support means or
`
`Ex.1017
`APPLE INC. / Page 6 of 11
`
`

`

`5,953,507
`
`3
`adapter hardware will filter out all the data that is not
`directed to the node address. In this situation, the three-way
`bridge program does not need to spend CPU cycles to
`perform the filtering. The desktop PC with the three-way
`bridge program should perform as well as one without the 5
`three-way bridge program.
`In a first aspect, the present invention provides an appa(cid:173)
`ratus for providing a three-way connection between a com(cid:173)
`puter network, a stationary computing device, and a mobile
`computing device, said apparatus comprising: (a) network 10
`interface means for interfacing to said computer network;
`(b) a network operating system on said stationary computing
`device and including means for processing information
`packets for and from said computer network; (c) communi(cid:173)
`cation interface means for communicating between said 15
`stationary computing device and said mobile computing
`device and including control means for transmitting and
`receiving information packets between said stationary com(cid:173)
`puting device and said mobile computing device; ( d) routing
`means for routing information packets between said com- 20
`puter network, said stationary computing device, and said
`mobile computing device, said routing means including
`detector means for detecting connection of a mobile com(cid:173)
`puting device to said communication interface means, and
`having redirector means responsive to a connection to said 25
`mobile computing device for redirecting information pack-
`ets between said computer network, said stationary comput(cid:173)
`ing device and said mobile computing device.
`In a second aspect of the present invention, there is
`provided a method for providing a three-way connection for 30
`transferring information packets between a stationary com(cid:173)
`puting device, a mobile computing device, and a network,
`said stationary computing device being coupled to said
`network through a network adapter, and said mobile com(cid:173)
`puting device utilizing a wireless communication channel 35
`for transferring information packets to said stationary com(cid:173)
`puting device, said method comprising the steps of: (a)
`determining if said mobile computing device is coupled to
`said stationary computing device via said wireless commu(cid:173)
`nication channel; (b) redirecting information packets origi- 40
`nating from said mobile computing device and destined for
`said network through said stationary computing device when
`said wireless communication channel is active as determined
`in step (a); (c) redirecting information packets originating
`from said network and destined for said mobile computing 45
`device through said stationary computing device when said
`wireless communication channel is active as determined in
`step (a).
`In another aspect of the present invention, there is pro(cid:173)
`vided a computer program product for use in a computer
`system comprising a stationary computing device, a mobile
`computing device and a network, said stationary computing
`device being coupled to said network and having a network
`operating system, and said mobile computing device utiliz(cid:173)
`ing a wireless communication channel for transferring infor(cid:173)
`mation packets to said stationary computing device, said
`computer program product comprising: a recording
`medium; means recorded on said medium for instructing
`said stationary computing device to perform the steps of: (a)
`determining if said mobile computing device is coupled to
`said stationary computing device via said wireless commu(cid:173)
`nication channel; (b) redirecting information packets origi(cid:173)
`nating from said mobile computing device and destined for
`said network through said stationary computing device when
`said wireless communication channel is active as determined
`in step (a); (c) redirecting information packets originating
`from said network and destined for said mobile computing
`
`4
`device through said stationary computing device when said
`wireless communication channel is active as determined in
`step (a).
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Reference will now be made to the accompanying draw(cid:173)
`ings which show, by way of example, a preferred embodi(cid:173)
`ment of the present invention, and in which:
`FIG. 1 shows in block diagram form a mobile support
`program according to the present invention;
`FIG. 2 shows in schematic form a configuration for
`providing a mobile PC with access to a wired computer
`network utilizing the mobile support program according to
`the present invention;
`FIG. 3 shows in schematic form another configuration for
`integrating a mobile PC with a desktop PC;
`FIG. 4 shows in schematic form another configuration for
`providing a desktop PC with access to a wired computer
`network utilizing the mobile support program; and
`FIG. 5 shows in schematic form another configuration for
`allowing a mobile PC to roam between desktop PC's uti(cid:173)
`lizing the mobile support program according to the present
`invention.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`The present invention provides a method and means for
`connecting a mobile or portable personal computer, referred
`to as a mobile PC, to a stationary or desktop PC. The desktop
`PC is coupled to a wired computer network.
`In the drawings, the wired computer network is denoted
`by reference 10, the desktop PC is denoted by reference 12,
`referred to individually as 12-1 and 12-2 in FIG. 5, and the
`mobile PC is denoted by reference 14. The mobile PC is
`described as a notebook or laptop computer, but may com-
`prise other mobile computing devices, such as, a personal
`digital assistant (PDA), a personal communication assistant
`(PCA), an electronic organizer or a two-way interactive
`TV/set-top box remote control. In the described system, the
`wired computer network 10 comprises a Local Area Net-
`work or LAN and is referred to as a wired LAN. It is,
`however, to be understood that other types of wired com(cid:173)
`puter networks are possible, for example, including an ATM
`network or a cable TV network.
`Data transmission over the LAN 10 is performed accord(cid:173)
`ing to well defined and internationally accepted protocol
`standards. In the present description, the LAN 10 is
`described (but not limited) in relation to known communi-
`50 cation protocol according to the Ethernet standard as will be
`within the understanding of those skilled in the art. Other
`protocols, such as, token ring, are also applicable and within
`the understanding of those skilled in the art.
`As will be familiar to those skilled in the art, an Ethernet
`55 frame, i.e. information packet, according to the MAC-layer
`(Medium Access Control) protocol comprises 7 bytes
`preamble, 1 byte frame delimiter, 6 bytes of information
`representing the source address, that is, the address of the
`originating or transmitting node, for the information packet,
`60 6 bytes of information representing the destination address
`for the information packet, 2 bytes for packet length/type, 46
`to 1500 bytes of data, and 4 bytes FCS. The arrangement of
`the various bits of information within the MAC-layer header
`has been standardized and is well-known to those skilled in
`65 the art.
`As shown in FIG. 2, the mobile PC 14 is coupled to the
`desktop PC 12 through a wireless communication channel
`
`Ex.1017
`APPLE INC. / Page 7 of 11
`
`

`

`5,953,507
`
`6
`5
`Reference is made to FIG. 1 which shows in block
`16. In the described system, the wireless communication
`channel 16 comprises an infrared communication channel,
`diagram form an implementation for the method and means
`although it is understood that other types of wireless com(cid:173)
`according to the present invention. The method and means
`munication links are possible. The implementation of the
`are embodied in computer software denoted generally by
`infrared channel 16 is within the understanding of those 5
`100 and computer hardware 50 which runs on the desktop
`skilled in the art using, for example, conventional IrDA
`PC 12. The software 100 runs the hardware 50 which
`chipsets, such as the IBM1502 IR controller chip from IBM
`couples the desktop PC 12 to the Ethernet LAN 10 and the
`Corp., or the NSC108IR controller chip from National
`wireless communication channel 16. The computer software
`Semiconductor Corp.
`100 comprises the workstation software for the Network
`In the description that follows, the following definitions 10
`Operating System or NOS.
`are used. Local area network (LAN) is a network that is
`The hardware 50 comprises a network adapter 52 and a
`usually confined to a small geographical area, e.g. within a
`wireless adapter 54. For an Ethernet based configuration, the
`building. IR WLAN is a wireless LAN, i.e. WLAN, that uses
`network adapter 52 comprises suitable Ethernet hardware
`infrared light as the communication medium. Mobile per(cid:173)
`which is coupled to the Ethernet LAN 10. For an infrared
`sonal computer (MPC) means any mobile device that has a
`IrDA 1.1 compatible infrared device. Desktop personal 15
`communication channel 16, the wireless adapter 54 com(cid:173)
`prises IrDA 1.1 hardware as will be familiar to one skilled
`computer (DPC) means any desktop device that has an IrDA
`in the art. The mobile PC 14 has a corresponding IrDA
`1.1 compatible infrared device. Access point (AP) means a
`device that connects a mobile PC to a wired LAN using a
`controller and device driver (not shown) for implementing
`wireless infrared connection between the access point and
`the communication channel 16.
`the mobile PC. Bridge means a bridge that operates at the 20
`As shown in FIG. 1, the workstation software 100
`OSI data link layer (i.e. layer 2) and copies frames from one
`includes an Ethernet device driver 102 and an IrDA device
`network to the other. The bridge often contains logic to copy
`driver 104. The Ethernet device driver 102 interfaces the
`only a subset of the frames it receives. This logic is known
`workstation software 100 to the Ethernet adapter 52 and the
`as filtering. A bridge is usually measured by its filtering rate
`IrDAdevice driver 104 interfaces the workstation 100 to the
`and forwarding rate.
`25 IrDA 1.1 adapter 54. In known manner, the Ethernet device
`The wired LAN 10 includes connections or nodes for
`driver 102 provides the workstation software 100 with the
`other terminals comprising a file server 18, a print server 20,
`capability to work with the specific Ethernet adapter 52 and
`and a host computer system 22. The file server 18, print
`perform data transmission on the LAN 10. Similarly, the
`server 20 and host computer 22 provide resources which can
`IrDA device driver 104 allows the workstation software to
`be shared between the mobile PC 14, the desktop PC 12 and 30
`transmit and receive information packets over the wireless
`other stations (e.g. mobile or desktop PC's) connected to the
`communication channel 16 through the IrDA adapter 54. In
`LAN 10. The file server 18 includes mass storage devices
`the described embodiment, each adapter 52, 54 comprises a
`(not shown) for providing file archival and retrieval. As
`NDIS type driver as will be understood by those skilled in
`shown in FIG. 2 (and FIG. 4), the print server 20 includes
`the art.
`a printer 24 for providing a printing resource for the network 35
`Referring to FIG. 1, the workstation software 100 pref(cid:173)
`10.
`erably includes upper layer protocol stacks 106 which
`The method and means according to the present invention
`support communication protocols for known Network Oper(cid:173)
`allows a mobile PC 14 to connect to an Ethernet wired LAN
`ating Systems (NOS). There is provided an upper layer
`10 via an existing desktop PC 12, thereby eliminating the
`protocol stack 106-1 for TCP/IP (Transmission Control
`need to purchase an additional access point (AP) or station
`Protocol/Internet Protocol) 106, an upper layer protocol
`box (not shown) for the mobile PC 14. In this mode, the
`stack 106-2 for NETBIOS LAN Requester, an upper layer
`mobile PC 14 is provided with access to the resources, e.g.
`protocol stack 106-3 for SNA 3270, and an upper layer
`file server 18 or the printer 24 on the network 10. The user
`protocol stack 106-4 for NETWARE™ 112. The upper layer
`of the mobile PC 14 may require access to the Ethernet
`protocol stacks 106 comprise software which will be well
`wired LAN 10 for the host computer 22, the file server 18,
`understood by one skilled in the art.
`the printer 24, etc. According to the present invention, the
`user can accomplish the connection via the desktop PC 12
`According to the invention, workstation software 100
`using the wireless infra-red communication link 16 between
`includes another device driver 110. As shown in FIG. 1, the
`the mobile PC 14 and the desktop PC 12.
`device driver 110 binds itself to the upper layer protocol
`50 stack 106. The device driver 110 also binds itself to the
`In another aspect, the present method allows the mobile
`Ethernet device driver 102 and the IrDA device driver 104.
`PC 14 to connect to the desktop PC 12 to provide the mobile
`PC 14 with access to the resources of the desktop PC 12, for
`The device driver 110 is implemented to mimic the
`example, a printer 26 as shown in FIG. 3 or a mass storage
`behaviour of a NDIS2 device driver in the described
`device. This feature is particularly useful to provide a
`embodiment. According to the invention, the device driver
`connection between the mobile PC 14 and the desktop PC 12 55
`110 takes on two personas. First, the device driver 110
`in order to synchronize files and/or databases.
`appears to the upper layer protocol stack 106, e.g. TCP/IP
`106-1, as an Ethernet NDIS2 device driver. On the other
`In another aspect, the method according to the present
`hand, for Ethernet device driver 102 and the IrDA device
`invention allows the desktop PC 12 to remain connected to
`driver 104, the device driver 110 appears as an upper layer
`the wired LAN 10 while the mobile PC 14 accesses the
`protocol stack 106.
`network 10 through the desktop PC 12. This aspect is 60
`depicted in FIG. 2.
`The device driver 110 according to the present invention
`operates in two modes: BRIDGE mode and
`In another aspect, the method according to the present
`invention allows the mobile PC 14 to roam between desktop
`PASSTHROUGH mode. The mode of operation depends on
`PC's 12-1 and 12-2 located on the same Ethernet LAN
`whether the mobile PC 14 has established a wireless infrared
`segment as illustrated in FIG. 5. This mode of operation and 65 connection with the desktop PC 12. The device driver 110
`the others shown in FIGS. 2 to 4 are described in more detail
`determines if a connection has been established by querying
`below.
`the MAC (Medium Access Control) statistics for the IrDA
`
`45
`
`40
`
`Ex.1017
`APPLE INC. / Page 8 of 11
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`5,953,507
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`7
`device driver 104. A specific field in the MAC statistics for
`the IrDA driver 104 serves to indicate whether an IrDA
`connection over the channel 16 exists.
`If there is an established connection over the wireless, i.e.
`infrared, communication channel 16 between the mobile PC
`14 and the desktop PC 12, the device driver 110 operates in
`BRIDGE mode. In BRIDGE mode, the device driver 110
`functions as an Ethernet transparent MAC-bridge that con(cid:173)
`nects the mobile PC 14 to the Ethernet wired LAN 10 via the
`desktop PC 12. The device driver 110 also acts as an 10
`Ethernet transparent MAC-bridge that connects the desktop
`PC 12 to the Ethernet wired LAN 10.
`In the BRIDGE mode of operation, the device driver 110
`puts both the Ethernet adapter 52 and the IrDA adapter 54
`into "promiscuous" mode. In promiscuous mode, the adapt(cid:173)
`ers 52, 54 receive all information packets regardless of the
`destination address. In BRIDGE mode, the device driver 110
`resends on the Ethernet LAN 10 any IR message received
`from the mobile PC 14 which is destined for a wired node,
`e.g. to the file server 18. On the other hand, an IR informa(cid:173)
`tion packet received from the mobile PC 14 and intended for
`the desktop PC 12 is forwarded by the device driver 110 to
`the upper layer protocol stack 106 that is bound to the device
`driver 110.
`Information packets originating from the desktop PC 12
`are handled as follows by the device driver 110 in BRIDGE
`mode. The device driver 110 sends any information packets
`destined for a wired node, e.g. print server 20, on the LAN
`10 and the packets are sent on the LAN 10 by the device
`driver 110 via the Ethernet device driver 102. Any informa(cid:173)
`tion packet from the desktop PC 12 destined for the mobile
`PC 14 is sent by the device driver 110 on the wireless
`communication channel 16 via the IrDA device driver 104.
`Information packets originating from the Ethernet LAN
`10 are routed by the device driver 110 as follows in BRIDGE
`mode. Any information packet received from the Ethernet
`LAN 10 and destined for the desktop PC 12 is forwarded by
`the device driver 110 to the upper layer protocol stack 106
`that is binded to the device driver 110 (provided such a stack
`exists). An information packet received from the LAN 10
`and destined to the mobile PC 14 is resent by the device
`driver 110 on the wireless communication channel 16 via the
`IrDA adapter 54.
`It will be appreciated that the device driver according to
`the present invention is not a standard-compliant ethernet
`MAC-bridge implementation. Rather, the primary function
`of the device driver 110 according to the present invention
`is to create a three-way connection between the Ethernet
`LAN 10, the desktop PC 12, and the mobile PC 14.
`The device driver 110 operates in PASSTHROUGH mode 50
`when there is no mobile PC 14 connected to the desktop PC
`12. In the PASSTHROUGH mode of operation, the device
`driver 110 puts the Ethernet adapter 52 back into NORMAL
`mode, i.e. to the preset universal or assigned network
`address and group address. The device driver 110 however
`keeps the IrDA adapter 54 in promiscuous mode.
`In PASSTHROUGH mode, the Ethernet adapter 52 filters
`out all non-broadcast message traffic from the Ethernet LAN
`10 that is not destined for its network address or group
`address. The device driver 110 passes all data packets 60
`received from the Ethernet adapter 52 to the upper layer
`protocol stack 116. In PASSTHROUGH mode, the device
`driver 110 does not examine or act on the data except for the
`following commands from the upper layer protocol stack:
`(1) Open_Adapter; (2) Close_Adapter; (3) Set_Station_ 65
`Address; ( 4) Add_Multicast_Address; (5) Delete
`Multicast_Address.
`
`8
`The device driver 110 is configured not to pass the
`Open_Adapter command to the Ethernet hardware adapter
`52. Instead, the device driver 110 returns an "Okay" indi(cid:173)
`cation to the upper layer protocol stack 106. Similarly, the
`5 device driver 110 does not pass the Close_Adapter com(cid:173)
`mand to the Ethernet adapter 54. Instead, the device driver
`110 returns an Okay indication to the upper layer protocol
`stack 106.
`The device driver 110 processes the Set_Station_
`Address command according to its mode of operation. In
`BRIDGE mode, the device driver 110 does not pass the
`Set_Station_Address command to the Ethernet adapter 52.
`Instead, the device driver 110 stores the station_address in
`memory and returns an Okay indication to the upper proto-
`15 col stack 106. When the device driver 110 switches to
`PASSTHROUGH mode, it sets the Ethernet adapter 52
`based on the station_address. In PASSTHROUGH mode,
`the device driver 110 passes the Set_Station_Address com(cid:173)
`mand to the Ethernet adapter 52. The device driver 110 also
`20 stores the station_address in memory. If the indication from
`the Ethernet adapter 52 is not okay, the device driver 110
`deletes the station_address from its memory.
`The device driver 110 processes the Add_Multicast_
`Address command differently depending on its mode of
`25 operation. In BRIDGE mode, the device driver 110 does not
`pass the Add_Multicast_Address command to the Ethernet
`adapter 52. Instead, the device driver 110 stores the
`multicast_address in memory and returns an Okay indica(cid:173)
`tion to the Ethernet adapter 52. When the device driver 110
`30 switches to PASSTHROUGH mode, the device driver 110
`sets the Ethernet adapter 52 based on the multicast_address.
`In PASSTHROUGH mode, the device driver 110 passes the
`Add_Multicast_Address command to the Ethernet adapter
`52. The device driver 110 also stores the multicast_address
`35 in memory. If the indication received from the Ethernet
`adapter 52 is not ok, the device driver 110 deletes the
`multicast_address from memory.
`Processing of the Delete_Multicast_Address also
`depends on the mode of operation for the device driver 110.
`In BRIDGE mode, the device driver 110 does not pass the
`Delete_Multicast_Address command to the Ethernet
`adapter 52. Instead, the device driver 110 deletes the
`multicast_address in memory and returns an Okay indica-
`45 tion to the Ethernet adapter 52. In PASSTHROUGH mode,
`the device driver 110 passes the Delete_Multicast_Address
`command to the Ethernet adapter 52. If the indication from
`the Ethernet adapter 52 is okay, the device driver 110 deletes
`the multicast_address from its memory.
`In another aspect, the device driver 110 provides roaming
`support. When the device driver 110 receives the first
`message from a mobi