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Having thus described my invention, what I claim as new, and desire to
secure by Letters Patent, is:
1. A method for transmitting information in a network that includes a
wireless network and a wired network, the network having at least one
mobile communication unit in wireless communication with the wired network
over the wireless network, the network being characterized in that users
of the network are each assigned a unique network address, comprising the
steps of:
establishing, through the wireless network, communication between the wired
network and a mobile communication unit;
requesting an assignment of a network address for the mobile communication
unit, the request being made to a network gateway by the mobile
communication unit through the wireless network, the network gateway being
bidirectionally coupled to the wired network for providing communications
to remote users of the network;
in response to the request, assigning, with the network gateway, a network
address to the mobile communication unit, the assigned address being
transmitted from the network gateway to the wired network;
receiving the assigned network address with the mobile communication unit,
the assigned address being received through the wireless network; and
in response to the received network address, the mobile communication unit
thereafter communicating with the network by employing the assigned
network address.
2. A method as set forth in claim 1 wherein the steps of establishing,
requesting, transmitting, and receiving each include a step of routing
information between the wireless network and the wired network through a
local gateway, the local gateway being coupled between the wireless
network and, through the wired network, to the network gateway.
3. A method as set forth in claim 2, wherein, in response to the mobile
communication unit becoming uncoupled from the wireless network, the
method further includes the steps of:
notifying the network gateway that the mobile communication unit is no
longer active, the step of notifying including a step of sending a message
from the local gateway over the wired network to the network gateway; and
in response to the notification by the local gateway, deassigning, at the
network gateway, the assigned network address.
4. A method as set forth in claim 3 wherein the step of notifying includes
an initial step of buffering within the local gateway, for a predetermined
interval of time, any information received from the wired network that is
addressed to the mobile communication unit that is no longer active, and
wherein, if the mobile communication unit again becomes coupled to the
wireless network before the expiration of the predetermined interval of
time, the local gateway does not execute the step of notifying.
5. A method as set forth in claim 1 and further including a step of
buffering, at the network gateway, packets of data addressed to the
assigned network address during a time that the mobile communication unit
is not actively coupled to the wireless network.
6. A method as set forth in claim 5 wherein in response to the mobile
communication unit indicating that it is once more actively coupled to the
wireless network, further including the steps of:
retrieving the buffered packets of data;
forwarding the retrieved packets to a local gateway that is bidirectionally
coupled between the wired network and the wireless network; and
transmitting the retrieved packets from the local gateway to the mobile
communication unit over the wireless network.
7. A method as set forth in claim 1 wherein the step of assigning includes
a step of allocating the assigned network address from a pool of network
addresses that is maintained by the network gateway.
8. A method as set forth in claim 7 wherein the wired network conforms to a
Transmission Control Protocol/Internet Protocol standard and wherein the
step of allocating includes an initial step of reserving a plurality of
Internet Protocol addresses for use by the network gateway.
9. A method as set forth in claim 1 wherein the step of requesting includes
a step of transmitting, from the mobile communication unit to the network
gateway, an identifier that is unique to the mobile communication unit.
10. A method as set forth in claim 9 wherein the step of assigning assigns
a single network address to a plurality of mobile communication units, the
assigned network address including, for each of the plurality of mobile
communication units, the respective one of the unique identifiers so as to
differentiate the plurality of mobile communication units one from
another.
11. A method as set forth in claim 1 and, in response to a message from the
mobile communication unit that the mobile communication unit intends to
terminate communication with the wired network, the method includes a
further step of deassigning the assigned network address at the network
gateway.
12. A method as set forth in claim 1 and, in response to a name inquiry to
determine a network address that is associated with a name, further
including the steps of:
if the name is associated with a permanently assigned network address,
returning the permanently assigned network address in response to the
inquiry;
if the name is associated with a temporarily assigned network address,
returning the temporarily assigned network address in response to the
inquiry; and
if the name is associated with a previously assigned network address,
returning a predetermined network address that differs from the previously
assigned network address.
13. In a data communications network comprised of a wired network and a
wireless network, apparatus for managing the bidirectional transmission of
information between the wired network and at least one mobile
communication unit in wireless communications with the wired network over
the wireless network, the data communications network being characterized
in that users of the data communications network are each assigned a
unique network address, comprising:
local gateway means, coupled between a wireless Local Area Network (LAN)
and the wired network, for communicating with a mobile communication unit;
and
global gateway means coupled to the local gateway means and to remote users
of the data communications network, the global gateway means including
means for maintaining a plurality of network addresses, means for
receiving a request for an assignment of a network address from the mobile
communication unit, means for assigning one of the plurality of network
addresses to the requesting mobile communication unit; and means for
routing data received from a remote user, the data having an address
corresponding to the assigned network address, to the mobile communication
unit having the assigned address.
14. Apparatus as set forth in claim 13 wherein the global gateway means
further includes means for buffering data received from a remote user, the
received data being addressed to a mobile communication unit having one of
the assigned network addresses.
15. Apparatus as set forth in claim 13 wherein the data communications
network includes a plurality of wireless LANs each of which has at least
one local gateway means coupled thereto.
16. Apparatus as set forth in claim 15 and further comprising a plurality
of global gateway means individual ones of which are coupled to different
ones of the plurality of wireless LANs through at least one of said local
gateway means, each of said plurality of global gateway means including
means for assigning network addresses to mobile communication units in
wireless communication with their respective wireless LANs.
17. Apparatus as set forth in claim 13 wherein the network addresses
correspond to Internet Protocol address.
18. Apparatus as set forth in claim 13 wherein the local gateway means
includes means for buffering data addressed to one or more mobile
communication units that are coupled to the wireless LAN.
19. In a data communications network comprised of a wired network and a
wireless network, a method for managing the bidirectional transmission of
information between the wired network and at least one mobile
communication unit in wireless communication with the wired network over
the wireless network, the data communications network being characterized
in that users of the data communications network are each assigned a
unique network address, comprising the steps of:
maintaining a plurality of the unique network addresses with a global
gateway means, the global gateway means being bidirectionally coupled to a
local gateway means, through the wired network, and also to remote users
of the data communications network, the local gateway means being coupled
between the wireless and the wired network;
receiving, at the global gateway means, a request for an assignment of the
network address from a mobile communication unit;
in response to the received request, assigning one of the plurality of
network addresses to the requesting mobile communication unit; and
in response to a message received from a remote user, the message having an
address that corresponds to the assigned network address, routing the
message from the global gateway to the local gateway means, and from the
local gateway means to the wireless network for reception by the mobile
communications unit having the assigned network address.
20. A method as set forth in claim 19 wherein the wired network operates in
accordance with a protocol known as a Transmission Control Protocol,
wherein the step of maintaining maintains network addresses that
correspond to a protocol known as an Internet Protocol, and wherein the
wireless network operates in accordance with a protocol other than the
Transmission Control Protocol. |
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Claims |
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Description |
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FIELD OF THE INVENTION
This invention relates generally to communication method and apparatus and,
in particular, to method and apparatus for managing network address
assignments in a network that includes mobile users.
BACKGROUND OF THE INVENTION
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. Morten and M. P. Marsili,
describes an architectural model of the Department of Defense (DoD)
protocol suite. Referring to FIG. 1 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 establishes criteria for an Internet
Protocol (IP) which supports 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 standard also defines the services required of the lower
protocol layer, describes the upper and lower interfaces, and outlines the
execution environment services need for implementation.
A Transmission Control Protocol (TCP) is a transport protocol providing
connection-oriented, end-to-end reliable data transmission in
packet-switched computer LANs and internetworks.
The Internet 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 network 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 Internet Protocol is designed to interconnect packet-switched
communication LANs to form an internetwork. The IP transmits blocks of
data, called internet datagrams, from sources to destinations throughout
the internet. Sources and destinations are hosts located on either the
same subnetwork or connected 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 IP does not create connections or logical circuits and has
no mechanisms to promote data reliability, flow control, sequencing, or
other services commonly found in virtual circuit protocols.
The DDN standard specifies a host IP. As defined in the DoD architectural
mode, the Internet Protocol resides in the internetwork layer. Thus, the
IP provides services to transport layer protocols and relies on the
services of the lower network protocol. In each gateway, a system
interconnecting two or more LANs, an IP resides above two or more LANs
protocol entities. Gateways implement the internet protocol to forward
datagrams between networks. Gateways also implement the Gateway to Gateway
Protocol (GGP) to coordinate signalling and other internet control
information.
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 communication channels. In U.S. Pat.
No. 4,706,081, issued Nov. 10, 1987, Hart et al. teach the merging of
physically 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, 1989,
entitled "Hierarchical Distributed Infrared 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 network, 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 peripherals. This patent describes the implementation of an
asynchronous access, token based protocol. In International Patent
W088/07794, published Oct. 6, 1988, G. Vacon discloses the use of a
wireless microwave bridge between two networks utilizing a CSMA/CD
protocol.
In IBM Technical Disclosure Bulletin Vol. 24 No. 8, 1982 F. Gfeller
describes general control principles of an infrared wireless communication
network incorporating multiple base stations and multiple mobile
computers. Transmission occurs over the wireless IR medium 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 users to 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
assignments and which assumes responsibility for the routing of all
packets destined for the mobile units. Additionally, a local mobile unit
gateway service is provided on every network or LAN in order to route
packets to the mobile units coupled to the network. In accordance with the
invention a network address, such as an Internet address, that is
associated with a particular mobile unit encodes a network not physically
embodied anywhere, referred to herein as a `pseudo-network`. Routers of
data packets are instructed to forward packets, destined for the
designated network, to the global gateway. The global gateway subsequently
executes methods, described in detail, to accomplish the packet
transmission 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 communication 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
provided 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 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 gateway also buffers and routes data received from a
remote user to the mobile communication unit having the assigned 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 invention are made more
apparent in the ensuing Detailed Description of the Invention when read in
conjunction with the attached Drawing, wherein:
FIG. 1 is a prior art 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
Referring to FIG. 2 there is illustrated a communications 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 communication 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 embodiment of the
invention the wireless medium is comprised of infrared (IR) radiation,
although other embodiments may employ an RF wireless medium. Each of the
header stations 12 has associated therewith a communications coverage
area, or cell 11.
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 assigned 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/Internet Protocol (TCP/IP), as described in detail in
"Internetworking with TCP/IP Principles, Protocols, and Architectures" by
Douglas E. Comer, Prentice Hall, N.J., 1988. 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 geographic area. The local gateways 16 may each be
an "intelligent" header station or may be a separate dedicated 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 during a time
when the mobile units are not in contact with the wireless network. The
data processor that comprises the global gateway 18 includes means for
assigning, 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 1) 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 network 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 gateway 18. These allocated IP addresses are
subsequently dynamically assigned by the global gateway 18 to requesting
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 IP addresses 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 physically 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 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. Preferably, 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 permanent pseudo-IP association, even
though a local gateway 16 may also maintain the relationship for so long
as the mobile unit 10 stays in contact with the local gateway 16. The
global gateway 18 also buffers any packets destined for a particular
mobile unit 10 during any time that the mobile unit 10 is out of touch
with the network, such as the mobile unit 10' which is not located within
one of the communication cells 11.
A function of the local gateway 16 is to deliver data packets, via the
wireless downlink, to known mobile units 10 within its associated cell 11.
If a mobile unit 10 is out of touch with the wireless network no other
local gateway 16 participates in the transmission of packets destined for
that mobile unit 10.
Being out of touch for a predetermined period of time causes the mobile
unit's local gateway 16 to notify the global gateway 18, via LAN 14, that
the mobile unit 10 is no longer a member of the group of mobile units
associated with the local gateway 16. In response to being notified of the
disappearance of the mobile unit 10 the global gateway 18 terminates the
forwarding of packets, through the local gateway 16, that are directed to
the inactive mobile unit.
The following communication operations are now described in detail: (a)
initialization of a mobile unit 10 and the initialization of network
routing for the mobile unit 10; (b) resumption of service to a mobile unit
10; (c) termination of service to a mobile unit 10; (d) delivery of
packets to a mobile unit 10; and (e) transmission of packets from a mobile
unit 10.
Initialization (FIG. 3)
When a mobile unit 10 first enters a LAN cell 11 it performs the following
operations. The newly arrived mobile unit 10 first directs a message, via
a header station 12, to the local gateway 16. This message requests the
local gateway 16, through the global gateway 18, to activate a pseudo-IP
address for the mobile unit 10. The mobile unit 10 identifies 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-IP 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 addresses.
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, the local gateway 16 instead begins to relay packets
from those sessions, the packets being stored and forwarded 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 activated mobile unit 10 a
permanently registered pseudo-IP address, the global gateway 18 may also
begin forwarding messages and other stored data to that mobile unit 10,
through the local gateway 16. This data is originally 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 buffered 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.
Resumption of Service (FIG. 4)
When a mobile unit 10 enters a cell 11 and indicates that it is to continue
a previous network connection, it sends a message to the local gateway 16,
via a header station 12. The message causes the local gateway 16 to notify
the global gateway 18, and possibly a previous local gateway 16, that the
mobile unit 10 has migrated to the new cell 11. The local gateway 16
requests from the global gateway 18 all packets currently queued for the
mobile unit 10 pseudo-IP address and delivers the packets over the
downlink wireless channel. The global gateway 18 thereafter forwards to
the local gateway 16 all future packets addressed to the pseudo-IP address
associated, either temporarily or permanently, with the mobile unit 10.
Any remote users having knowledge of the pseudo-IP address may negotiate
an optimal route to the local gateway 16, employing known IP protocols. In
this regard the local gateway 16 assumes responsibility for breaking the
route if and when the mobile unit 10 migrates out of the local gateway's
16 cell area.
To avoid an unstable situation that may arise if the local gateway 16
purged internal data structures of all knowledge of a mobile unit 10 as
soon as the mobile unit 10 was determined to be out of touch, such as
might arise if a particular mobile unit 10 wandered along the periphery of
a cell 11; the local gateway 16 temporarily queues packets destined for
the mobile units 10 within the local gateway's service area (or LAN). If
the mobile unit 10 returns to the local gateway's service area before the
queuing time limit expires the local gateway 16 delivers the queued
packets to the mobile unit 10. As such, so long as the mobile unit 10
returns to the service area within a predetermined time interval the local
gateway is not required to notify the global gateway 18 that the local
gateway 16 has relinquished responsibility for the mobile unit 10.
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 mobile 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 unit 10 has previously requested
and received a permanently associated pseudo-IP address.
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.sub.-- E.sub.-- Perkins"
may be located within a domain designated "hawII.np.watson.ibm.com" and
thus have the fully qualified name "C.sub.-- E.sub.--
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 18. A request for a
mobile unit 10 name fails unless there exists an association registered
between the mobile unit 10 name and a particular pseudo-IP address.
Nameserver operation is now described in greater detail. If the requested
name is associated to a permanently 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 registered 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 IP 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 the global gateway 18 if it is used by
remote hosts for incoming mail requests Using the example given previously
the returned IP address may 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 associated 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 registered, permanent IP address may rely on
conventional IP methods for point-to-point network communications.
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, transmission of the packets associated with the
nonstandard protocol, between the gateways 18 and 16, is accomplished by
conventional IP methods.
In this regard packets bearing the IP address are routed to the global
gateway 18 which encapsulates 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 non-Internet protocol. That is, by whatever
protocol is established for the wireless network communication. 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 enable special handling
of pseudo-IP addresses, the remote user is enabled to deliver the mobile
unit 10 packets directly to the mobile unit's local gateway 16, without
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 IP addressing 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 gateways 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 Internetwork 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 address, but which
nevertheless maintain active communications with the mobile units 10. To
eliminate this potential bottleneck several global gateways 18 are
employed 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 18.
Alternatively, each global gateway 18 maintains and shares with its peers
a consistent set of tables describing the current routing information, or
location, for each mobile unit 10. If each global gateway 18 has separate
pseudo-networks, then IP routing will automatically send IP packets to the
correct global gatew | | |
