U.S. patent application number 11/708988 was filed with the patent office on 2007-06-28 for peer to peer network communication.
Invention is credited to Jeremy Joseph Gordon, Adam Pierce Harris, Mark Jacob.
Application Number | 20070150552 11/708988 |
Document ID | / |
Family ID | 29406404 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070150552 |
Kind Code |
A1 |
Harris; Adam Pierce ; et
al. |
June 28, 2007 |
Peer to peer network communication
Abstract
Methods and apparatus for peer to peer network communication. In
one implementation, a method of communicating between a first
client system and a second client system includes: discovering
first address information for a first client system connected to a
first network address translation device; sharing the first address
information with a second client system; receiving second address
information for the second client system; and establishing
communication between the first client system and the second client
system using the second address information.
Inventors: |
Harris; Adam Pierce; (San
Diego, CA) ; Gordon; Jeremy Joseph; (San Francisco,
CA) ; Jacob; Mark; (San Diego, CA) |
Correspondence
Address: |
FROMMER LAWRENCE & HAUG
745 FIFTH AVENUE- 10TH FL.
NEW YORK
NY
10151
US
|
Family ID: |
29406404 |
Appl. No.: |
11/708988 |
Filed: |
February 21, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10215899 |
Aug 8, 2002 |
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11708988 |
Feb 21, 2007 |
|
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60380396 |
May 13, 2002 |
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Current U.S.
Class: |
709/218 |
Current CPC
Class: |
H04L 29/1233 20130101;
H04L 69/22 20130101; H04L 61/2532 20130101; H04L 29/12471 20130101;
H04L 41/0856 20130101; H04L 43/50 20130101; H04L 41/0853 20130101;
H04L 41/0866 20130101; H04L 29/12415 20130101; H04L 61/2514
20130101; H04L 61/2553 20130101; H04L 29/12009 20130101; H04L
29/12367 20130101 |
Class at
Publication: |
709/218 |
International
Class: |
G06F 15/16 20060101
G06F015/16 |
Claims
1-25. (canceled)
26. A network client system, comprising: a network connection
interface for connecting to a network; a network address manager
for sending an address request to an address server connected to
the network to determine address information for the network client
system; a network registration manager for registering the address
information of the client system with a matching server connected
to the network; a network sharing manager for sharing the address
information with a second client system connected to the network,
wherein the network connection interface is connected to a network
address translation device, wherein the address information
includes a local network address and a public network address,
wherein the local network address corresponds to the network client
system and is established by the network address translation
device, wherein the public network address corresponds to the
network address translation device, and wherein said network
address translation device establishes said local network address
for said network client system by mapping a port number associated
with said network client system using port address translation and
attaching the port number to said public network address.
27. The network client system of claim 26, further comprising a
network mapping maintenance manager for regularly sending messages
to a mapping maintenance server connected to the network.
28. (canceled)
29. The network client system of claim 27, where the public network
address includes a port number assigned by the network address
translation device to correspond to the network client system.
30. The network client system of claim 27, further comprising game
components for providing video game console functionality.
31-52. (canceled)
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/380,396 filed May 13, 2002, the disclosure of
which is incorporated herein by reference.
BACKGROUND
[0002] One typical type of NAT server (network address translation
server) acts as a gateway between a local network and an external
network, such as the Internet. This NAT server is a network device
that allows one or more machines (e.g., computers) in the local
network to share one public or external network address, such as an
Internet address. The NAT server maintains a set of unique local or
internal network addresses for the machines in the local network.
Accordingly, each machine in the local network has a local network
address and a public network address. For communication between the
local network and the external network, the NAT server translates
back and forth between the public network address and the local
network addresses for each of the machines. Typically this network
address translation is transparent to the individual machines
within the local network and so the machines are not aware of the
public address used by the NAT server.
SUMMARY
[0003] The present disclosure provides methods and apparatus for
peer to peer network communication. In one implementation, a
network system includes: a first network address translation
device, connected to a network and having a first public network
address; a first client system, connected to the first network
address translation device and having a first local network address
established by the first network address translation device; a
second network address translation device, connected to the network
and having a second public network address; a second client system,
connected to the second network address translation device and
having a second local network address established by the second
network address translation device; an address server, connected to
the network; a matching server, connected to the network; where the
first network address translation device, the second network
address translation device, the address server, and the matching
server can send data to each other through the network, where the
address server determines a public network address for a client
system from data received from the client system and returns the
derived public network address to the client system, where the
matching server includes a registry table for registering client
systems and storing the public network address and local network
address for one or more registered client systems, where the first
client system includes: a first network address manager for
communicating with the address server to determine the first public
network address, a first network registration manager for
registering the first client system with the matching server, a
first network sharing manager for sharing the first public network
address and the first local network address with the second client
system, where the second client system includes: a second network
address manager for communicating with the address server to
determine the second public network address, a second network
registration manager for registering the second client system with
the matching server, a second network sharing manager for sharing
the second public network address and the second local network
address with the first client system. In another implementation,
the network system also includes a mapping maintenance server
connected to the network.
[0004] In another implementation, a method of communicating between
a first client system and a second client system includes:
discovering first address information for a first client system
connected to a first network address translation device; sharing
the first address information with a second client system;
receiving second address information for the second client system;
and establishing communication between the first client system and
the second client system using the second address information.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 shows a network system architecture.
[0006] FIG. 2 is a block diagram of one implementation of a client
system.
[0007] FIG. 3 is a flowchart of establishing and maintaining peer
to peer network communication between two client systems.
[0008] FIG. 4 is a flowchart of a client system discovering its
local and public network addresses.
[0009] FIG. 5 is a flowchart of two client systems sharing their
local and public network addresses.
[0010] FIG. 6 is a flowchart of a first client system establishing
communication with a second client system.
[0011] FIG. 7 is a flowchart of the second client system
establishing communication with the first client system.
[0012] FIG. 8 is a flowchart of a client system maintaining the
mapping assigned by a connected NAT device.
[0013] FIGS. 9A-9C show alternative network configurations.
DETAILED DESCRIPTION
[0014] The present invention provides methods and apparatus for
peer to peer network communication. The present invention allows
two peer or client systems (e.g., network-enabled video game
console systems) to communicate with each other across a network
(e.g., the Internet) even though one or both client systems are
behind respective NAT devices (network address translation
devices). As described below, in one implementation, the network
communication uses a four part process: (1) discovery--each client
system discovers its public address on the network, (2)
sharing/distribution--each client system shares its address
information with other systems that wish to communicate, (3)
communication establishment--the client systems establish
communication, and (4) mapping maintenance--each client system
maintains its current address mapping in the corresponding NAT
device.
[0015] FIG. 1 shows a network system architecture 100. A first
client system 105 is connected to a first NAT device (network
address translation device) 110, forming a first local or internal
network 115. The first client system 105 is a network-enabled
system, such as a video game console system including a network
adapter or a computer system. As a video game console system, the
first client system 105 includes hardware and/or software providing
video game functionality and hardware and/or software providing
network communication as described below. In one implementation,
the first client system 105 is a "Playstation 2".TM. game console
by Sony Computer Entertainment Inc..TM. The first NAT device 110 is
a typical NAT box or NAT server, or alternatively is a type of
proxy server or part of a gateway, router, or firewall. One or more
additional systems or network devices, such as a computer, may also
be connected to the first NAT device 110 and be within the first
local network 115. Each system in the first local network 115 has a
local network address assigned and maintained by the first NAT
device 110. In one implementation, a local network address in the
first local network 115 includes an address number and a port
number, such as according to UDP/IP (e.g., where the address number
is an IP address). In an alternative implementation, the first
local network 115 uses a different communication protocol and so
the local network address includes different information to
identify a system.
[0016] The first NAT device 110 is connected to an external or
public network 120, such as the Internet. Each addressable system
or device connected to the external network 120 has a public
network address. A "public" network address is used on the external
network 120 and "local" network addresses are used within local
networks, such as the first local network 115. In one
implementation, a public network address includes an address number
and a port number, such as according to UDP/IP. In an alternative
implementation, the external network 120 uses a different
communication protocol and so the public network address includes
different information to identify a system. In one implementation,
the local network addresses of the first local network 115 are not
compatible with the external network 120 (e.g., the local network
addresses are not recognizable in the communication protocol of the
external network 120).
[0017] The first NAT device 110 has a public network address. The
first client system 105 is indirectly connected to the external
network 120 through the first NAT device 110 and does not have a
public network address. The first client system 105 shares the
public network address of the first NAT device 110 with other
systems in the first local network 115 (if any are present). The
first NAT device 110 assigns a local network address to each system
in the first local network 115. The first NAT device 110 translates
between the public network address and local network addresses to
route data between the external network 120 and the first local
network 115. In an alternative implementation, the first NAT device
110 has a two or more public network addresses to share among
systems in the first local network 115.
[0018] In one implementation, the first NAT device 110 maps port
numbers to systems in the first local network 115, such as by using
a PAT technique (Port Address Translation). The first NAT device
110 assigns a port number to a local system in the first local
network 115 when the local system sends data to a destination on
the external network 120. The first NAT device 110 stores the port
number as a port mapping between the port number and the local
system. The first NAT device 110 assigns and stores a single port
number for all outgoing data from a single local system. The first
NAT device 110 includes the assigned port number with the outgoing
data and so the recipient can use the port number when responding.
The first NAT device 110 determines which system in the first local
network 115 is the intended recipient of incoming data by comparing
the port number attached to the incoming data with the port
mappings stored within the first NAT device 110.
[0019] The first NAT device 110 establishes and adjusts the port
mappings dynamically according to data sent and received using the
mapping. If the first NAT device 110 does not receive data from a
local system or from the external network 120 including a port
number for a period of time, the first NAT device 110 releases the
port mapping for that port number (a "timeout"). As described
below, the first client system 105 can prevent this timeout by
periodically sending messages out to the external network 120.
[0020] In one implementation, the first NAT device 110 screens
incoming data (e.g., for security reasons) by comparing the network
address of the sender of the incoming data with addresses of
recipients of data sent by the local system indicated by the port
number. When the first NAT device 110 sends data from a local
system to a recipient on the external network 120, the first NAT
device 110 records the destination address along with the port
mapping for the local system. The first NAT device 110 does not
forward incoming data to a local system on the first local network
115 if the local system has not already sent data to a recipient at
the same network address as that of the incoming data. The first
NAT device 110 compares the network address of the sender of
incoming data with the recorded destination address(es) of outgoing
data using the port included with the incoming data. As described
above, the first NAT device 110 records destination addresses along
with port mappings, so the first NAT device 110 can use a port
number as an index to find destination addresses to which data has
been sent by a local system. If there is not a match, the first NAT
device 110 does not forward the incoming data into the first local
network 115. As described below, the first client system 105 uses
this security functionality to "approve" a system on the external
network 120 by sending data to that system and so causes the first
NAT device 110 to allow data from that approved system into the
first local network 115.
[0021] For example, when the first client system 105 sends data to
a recipient on the external network 120 the first NAT device maps a
port number to the first client system 105. The first NAT device
110 includes the public network address for the first NAT device
110 and the mapped port number for the first client system 105 with
the outgoing data. The first NAT device 110 also records the
address of the recipient. When the first NAT device 110 receives
data including that port number, the first NAT device 110 compares
the address of the sender with the recorded address of the
destination for the previously sent outgoing data. If the addresses
match, the first NAT device 110 forwards the data to the first
client system 105 using the local network address of the first
client system 105.
[0022] A second client system 125 is connected to a second NAT
device 130, forming a second local network 135. Similar to the
first client system 105, the second client system 125 is a
network-enabled system, such as a video game console system
including a network adapter. Similar to the first NAT device 110,
the second NAT device 130 is a typical NAT box or NAT server, or
alternatively is a type of proxy server or part of a gateway or
router. The second client system 125 and the second NAT device 130
operate similarly to the first client system 105 and the first NAT
device 110, respectively (e.g., in terms of port mapping and
screening incoming data). One or more additional network devices
may also be connected to the second NAT device 130 and be within
the second local network 135. Each system or device in the second
local network 135 has a local network address assigned and
maintained by the second NAT device 130, similar to the first local
network 115. In one implementation, the first local network 115 and
the second local network 135 are the same type of network and so
use the same communication protocol, however, in alternative
implementations, the local networks 115, 135 can be different
types.
[0023] Similar to the first NAT device 110, the second NAT device
130 is connected to the external network 120. Accordingly, the
second client system 125 is indirectly connected to the external
network 120 through the second NAT device 130. The NAT devices 110,
130 can send data to each other through the external network 120
according to the protocols of the external network 120.
[0024] Three server systems are connected to the external network
120 as well: an address server 140, a matching server 145, and a
mapping maintenance server 150. Each of the server systems 140,
145, 150 is a network server system, such as a computer system or a
mainframe system. Alternatively, some or all of the server systems
140, 145, 150 are included within a single system connected to the
external network 120. Each of the server systems 140, 145, 150 has
a respective network address on the external network 135. These
server network addresses are known to the client systems 105, 125.
The address server 140 assists the client systems 105, 125 with
address discovery. The matching server 145 assists the client
systems 105, 125 with address sharing. The mapping maintenance
server 150 assists the client systems 105, 125 with maintaining the
address mapping of the NAT devices 110, 130, respectively. In an
alternative implementation, the maintenance mapping server is
omitted.
[0025] FIG. 2 is a block diagram of one implementation of a client
system 200, such as first client system 105 in FIG. 1. The client
system 200 includes four managers: a network address manager 205, a
network registration manager 210, a network sharing manager 215,
and a network mapping maintenance manager 220. Each of the managers
205, 210, 215, 220 is implemented as a software component of the
client system 200. Alternatively, some or all of one or more of the
mangers 205, 210, 215, 220 is implemented in hardware. The network
address manager 205 controls communication between the client
system 200 and the address server 140 to discover a public network
address associated with the client system 200 by a connected NAT
device, such as the first NAT device 110. The network registration
manager 210 controls communication between the client system 200
and the matching server 145 to register the client system 200 with
the matching server 145. The network sharing manager 215 controls
communication with the matching server 145 to determine the public
and local network addresses of another client system that has
requested communication with the client system 200. The mapping
maintenance manger 220 controls communication with the mapping
maintenance server 150 to prevent the NAT device connected to the
client system 200 from timing out the mapping established for the
client system 200. In an alternative implementation, the client
system 200 does not include a mapping maintenance manager 220. The
client system 200 includes a network interface 225 for connecting
to and communicating with the local network of the client system
200. The network interface 225 includes a network communication
device, such as a network adapter or modem. The client system 200
also includes components for general operation, such as a CPU 230,
memory 235, and an I/O interface 240. For a game console client
system, the client system includes additional video, sound, and
application specific software and/or hardware ("game components").
As noted above, in one implementation, a client system 200 is a
"Playstation 2".TM. by Sony Computer Entertainment Inc..TM.
including hardware and software for network communication as
described herein.
[0026] FIG. 3 is a flowchart of establishing and maintaining peer
to peer network communication between two client systems, such as
the first client system 105 and the second client system 125 in
FIG. 1. Each client system discovers its address information, block
305. A client system, such as the client systems 105, 125 in FIG.
1, has associated address information including a public network
address and a local network address. As described below referring
to FIG. 4, a client system discovers its public network address by
communicating with the address server (recall the address server
140 in FIG. 1). A client system discovers its local network address
by accessing locally stored information or by querying the
corresponding NAT device. The client systems share their discovered
address information with each other, block 310. As described below
referring to FIG. 5, one or both of the client systems register
with the matching server (recall the matching server 145 in FIG.
1). One of the client systems requests communication with the other
registered client system and the matching server shares the address
information between the client systems. The client systems
establish communication with each other using the received address
information, block 315. As described below referring to FIG. 6,
each client system sends messages to the other client system using
the shared address information so that the NAT devices recognize
the incoming messages as "approved." While the client systems are
communicating, the client systems maintain the mapping established
by the corresponding NAT devices, block 320. As described below
referring to FIG. 8, each client system periodically sends messages
to the mapping maintenance server (recall the mapping maintenance
server 150 in FIG. 1) so that the corresponding NAT device does not
change or timeout the established port mapping for the client
system. In an implementation that does not include a mapping
maintenance server, the client systems do not maintain this mapping
using a mapping maintenance server.
[0027] FIG. 4 is a flowchart of a client system discovering its
local and public network addresses (recall block 305 of FIG. 3). As
described above, the local network address is the network address
of the client system in a local network and is assigned by a NAT
device connected to the local network. The public network address
is the network address on the external network shared by a NAT
device among the systems in the local network connected to the NAT
device. In one implementation, a local or public network addresses
includes an address number and a port number. The client system
uses its network address manager component to discover its public
and local network addresses (recall network address manager 205 in
FIG. 2).
[0028] A client system first discovers its local network address,
block 405. In one implementation, a client system discovers its
local public address by accessing local storage, such as by
querying the network stack software used by the client system. The
client system establishes the local port number when the client
system initiates communication with the NAT device and so the
client system is already aware of the port number. Alternatively,
the client system can request the local network address from the
corresponding NAT device. The client system sends an address
request to the address server to discover the public network
address, block 410. The client system sends the address request to
the address server through the NAT device. As part of the NAT
device's network address translation functionality, the NAT device
adds the public network address to the address request, such as in
header information for the address request. If the NAT device has
not already assigned a port number to the client system, the NAT
device assigns a port number and includes the port number in the
public network address in the address request (e.g., in the UDP
header). The address server extracts the public network address
from the address request and stores the public network address,
block 415. The public network address is located within the address
request at a known location (e.g., within the header) so the
address server can find the public network address in the address
request. In an alternative implementation, the address server does
not store the public network address or only stores the public
network address temporarily. The address server returns the public
network address to the client system by generating an address
report and sending the address report to the client system, block
420. The address report includes the extracted public network
address as part of the data or payload of the message as well as in
the addressing portion of the message (e.g., in the header). The
NAT device converts the public network address to the client
system's local network address according to the port number and
forwards the address report to the client system. For example, the
NAT device accesses the port mapping for the client system
according to the port number of the public network address and
retrieves the local network address. The NAT device then replaces
the public network address in the message's header information with
the local network address. Accordingly, the NAT device modifies the
header by removing the public network address, but does not modify
the data portion of the message. The client system receives the
address report and stores the included public network address,
block 425. The client system has now discovered its local and
public network addresses.
[0029] FIG. 5 is a flowchart of two client systems sharing their
local and public network addresses (recall block 310 of FIG. 3). A
first client system registers with the matching server, block 505.
A client system uses its network registration manager component to
manage registering with the matching server (recall network
registration manager 210 in FIG. 2). The first client system sends
a registration request to the matching server. The registration
request includes the first client system's discovered local and
public network addresses. The registration request indicates to the
matching server that the sending client system is available for
communication using the provided address information. The matching
server registers the first client system in a registry table, block
510. The matching server maintains a registry table with entries
storing address information for registered systems. The matching
server creates an entry in the registry table for the first client
system and records the provided address information in the entry.
The second client system sends a matching request to the matching
server, block 515. A client system uses its network sharing manager
component to manage obtaining the address information for another
client system from the matching server (recall network sharing
manager 215 in FIG. 2), both to select a registered client system
and to receive address information after registering, as described
below. The matching request indicates to the matching server that
the second client system is requesting information to establish
communication with another client system. The matching server sends
registry information to the second client system, block 520. In one
implementation, the matching server sends the registry table to the
second client system. In another implementation, the matching
server communicates with the second client system so that the
second client system can access the registry table to identify a
registered client system with which to communicate, such as by
accepting search queries from the second client system. The second
client system selects the first client system from among the
registered client systems, block 525. The second client system
stores the address information for the first client system, block
530. In one implementation, the registry information sent to the
second client system includes address information for the
registered client systems. In another implementation, the second
client system separately requests the address information for the
selected client system from the matching server. The second client
system sends a matching selection to the matching server, block
535. The matching selection indicates with which of the registered
client systems the second client system is to communicate (in this
case, the first client system). The matching selection also
includes the second client system's address information. In one
implementation, the matching selection also serves as a request for
the address of the first client system. The matching server sends
the second client system's address information to the first client
system as the selected client system, block 540. The first client
system receives and records the second client system's address
information, block 545. Each of the two client systems have now
shared their address information with the other client system
through the matching server.
[0030] FIG. 6 is a flowchart of a first client system establishing
communication with a second client system (recall block 315 of FIG.
3). The first client system sends one or more test messages to the
second client system, block 605. The first client system sends some
of the test messages to the second client system using the public
network address for the second client system (outgoing public
address test messages) and some of the test messages using the
local network address for the second client system (outgoing local
address test messages). As described above, the first client system
received the public and local network addresses for the second
client system when the two client systems shared address
information (recall FIG. 5). In an implementation where the local
network addresses of the second client system's local network are
not compatible with the external network (e.g., the local network
addresses are not recognizable under the communication protocol of
the external network), the first client system does not send test
messages using the local network address. The first client system
continues to send test messages to the second client system until
the first client system receives a confirmation message from the
second client system in block 630, as described below.
[0031] The NAT device connected to the first client system records
the destination addresses of the outgoing test messages, block 610.
The NAT device connected to the first client system (e.g., the
first NAT device 110 in FIG. 1) is a gateway between the local
network of the first client system and the external network.
Accordingly, the outgoing test messages pass through the NAT
device. As described above, the NAT device screens incoming data
and does not allow data to enter the NAT device's local network
unless the local network destination of the incoming data has
already attempted to communicate with the sender of the incoming
data. The NAT device records the destination address of outgoing
data from the systems on the local network as "approved" addresses
for the sender of the outgoing data. The NAT device compares the
origin address of the incoming data (i.e., the address of the
sender) with recorded "approved" addresses for the intended
recipient on the local network. The NAT device only forwards
incoming data to the local recipient when the origin address
matches one of the "approved" addresses for the local
recipient.
[0032] Accordingly, the NAT device records the destination
addresses of the outgoing test messages as "approved" addresses of
systems with which the first client system is attempting to
communicate. When the NAT device receives data for the first client
system that is from the same address as the destination address of
one of the first client system's outgoing test messages, the NAT
device forwards the incoming data to the first client system. The
first client system is sending test messages to addresses for the
second client system, so the NAT device will forward data from the
second client system to the first client system.
[0033] While the first client system is sending test messages to
the second client system, the second client system is sending test
messages to the first client system as well, as described below
referring to FIG. 7. As described above for the first client
system, the second client system sends outgoing public address test
messages (and outgoing local address test messages if appropriate)
using the address information for the first client system. The NAT
device connected to the second client system (e.g., the second NAT
device 130 in FIG. 1) records the destination addresses for the
outgoing test messages and so will forward incoming data for the
second client system received from the first client system.
[0034] The first client system receives a test message from the
second client system, block 615. As described above, the NAT device
connected to the first client system forwards an incoming test
message from the second client system to the first client system
because the NAT device matches the origin address of the incoming
test message with a recorded "approved" address. The first client
system records the origin address of the received test message,
block 620. The first client system sends a confirmation message to
the second client system using the recorded origin address, block
625. The outgoing confirmation message indicates to the second
client system that the first client system has received a test
message from the second client system. Similarly, the second client
system receives a test message from the first client system and
sends a confirmation message to the first client system using the
origin address of that test message. The first client system
receives a confirmation message from the second client system,
block 630. When the first client system receives a confirmation
message from the second client system, the first client system
stops sending test messages to the second client system. The first
client system has now established communication with the second
client system. After the second client receives the confirmation
message from the first client system, the second client system will
have established communication with the first client system. The
client systems have confirmed an address to which each system can
send data and have that data successfully pass through the NAT
device of the recipient system.
[0035] By first sending test messages addressed to the second
client system so that the NAT device will forward messages from the
second client system to the first client system, the first client
system is "punching holes" in the security features of the NAT
device. Accordingly, this technique is referred to as "hole
punching." Using "hole punching" the first and second client
systems can establish communication without altering the operation
of the NAT devices.
[0036] FIG. 7 is a flowchart of the second client system
establishing communication with the first client system. The
actions of FIG. 7 occur in conjunction with those described above
referring to FIG. 6. The second client system sends test messages
to the first client system using the address information received
when the client systems shared address information, block 705. As
noted above, the second client system sends outgoing public address
test messages using the first client system's public network
address and also sends outgoing local address test messages if the
local network address is compatible with the external network. The
second client system continues to send test messages to the first
client system until the second client system receives a
confirmation message from the first client system in block 730, as
described below. The NAT device connected to the second client
system records the destination addresses for the outgoing test
messages as "approved" addresses, block 710. As described above,
the first client system is also sending test messages to the second
client system and the second client system receives a test message
from the first client system, block 715. The second client system
records the origin address of the received test message, block 720,
and sends a confirmation message to the first client system using
the origin message, block 725. As described above, the first client
system also sends a confirmation message to the second client
system after receiving a test message from the second client system
and the second client system receives the confirmation message,
block 730. When the second client system receives a confirmation
message from the first client system, the second client system
stops sending test messages to the first client system. The second
client system has now established communication with the first
client system.
[0037] FIG. 8 is a flowchart of a client system maintaining the
mapping assigned by a connected NAT device (recall block 315 of
FIG. 3). A client system uses its network mapping maintenance
manager component to manage maintaining the address mapping of a
connected NAT device with the mapping maintenance server (recall
network mapping maintenance manager 220 in FIG. 2). As described
above, in one implementation, a NAT device assigns local network
addresses to the systems on the local network of the NAT device.
The NAT device also assigns port numbers for the public network
address used by local systems. When a local system sends data to
the external network, the NAT device assigns a port number to the
local system and stores the port number. When the NAT device
receives incoming data, the NAT device checks the port number in
the target address for the incoming data (e.g., in the header
information) to determine which local system is the intended
recipient. As described above the NAT device also uses the port
number to confirm that the sender of the incoming data is
"approved" before forwarding the data to the local system. Once the
NAT device has assigned a port number to a local system, the NAT
device begins counting down a timer. If the local system sends more
data to the external network, the NAT device uses the same port
number and resets the timer. Similarly, if the NAT device receives
incoming data using the port number, the NAT device resets the
timer. If the timer reaches zero, the NAT device frees the port
number (a "timeout") because the port number has not been used
recently. To prevent this "timeout" a client system periodically
sends mapping maintenance messages to the mapping maintenance
server while the client system is communicating or attempting to
communicate with another client system. As described above, in one
implementation, the mapping maintenance server is included within
the address server or the matching server and so the client system
sends mapping maintenance messages to the appropriate server. In
one implementation not including a mapping maintenance server, the
client system does not send mapping maintenance messages.
[0038] The client system sends a mapping maintenance message to the
mapping maintenance server through the connected NAT device, block
805. Referring to FIG. 1, the first client system 105 sends a
mapping maintenance message through the first NAT device 110 to the
mapping maintenance server 150. The NAT device receives the mapping
maintenance message and resets the timer for the port number
assigned to the client system, block 810. The NAT device sends the
mapping maintenance message to the mapping maintenance server,
block 815. After a predetermined period, the client system
evaluates whether to maintain the current address, block 820. If
the client system is communicating with another client system or
attempting to communicate with another client system, the client
system sends another mapping maintenance to the mapping maintenance
server to preserve the current port mapping, returning to block
805. If the client system is done communicating, the client system
does not send another mapping maintenance message and allows the
port mapping to timeout, block 825. In one implementation, the
mapping maintenance server does not respond to the client system.
Alternatively, the mapping maintenance server sends a mapping
maintenance confirmation message to the client system.
[0039] While the description above focuses on a network
configuration where two client systems are behind respective NAT
devices (recall FIG. 1), the operation of the two client systems
and the server systems are independent of the presence of NAT
devices. FIGS. 9A-9C show alternative network configurations. In
FIG. 9A, a first client system 905 is behind a NAT device 910 while
a second client system 915 is not connected to a NAT device. In
FIG. 9B, both client systems 930, 935 are not connected to NAT
devices. In FIG. 9C, both client systems 970, 975 are behind the
same NAT device 980 in the same local network 985. In each of these
alternative configurations, as well as other variations, the client
systems and server systems can interact in substantially the same
way as described above.
[0040] The various implementations of the invention are realized in
electronic hardware, computer software, or combinations of these
technologies. Most implementations include one or more computer
programs executed by a programmable computer. For example,
referring to FIG. 1, in one implementation, each client system 105,
125 and server system 140, 145, 150 includes one or more
programmable computers implementing the respective aspects of the
network system described above. In general, each computer includes
one or more processors, one or more data-storage components (e.g.,
volatile or non-volatile memory modules and persistent optical and
magnetic storage devices, such as hard and floppy disk drives,
CD-ROM drives, and magnetic tape drives), one or more input devices
(e.g., mice and keyboards), and one or more output devices (e.g.,
display consoles and printers).
[0041] The computer programs include executable code that is
usually stored in a persistent storage medium and then copied into
memory at run-time. The processor executes the code by retrieving
program instructions from memory in a prescribed order. When
executing the program code, the computer receives data from the
input and/or storage devices, performs operations on the data, and
then delivers the resulting data to the output and/or storage
devices.
[0042] Various illustrative implementations of the present
invention have been described. However, one of ordinary skill in
the art will see that additional implementations are also possible
and within the scope of the present invention. Accordingly, the
present invention is not limited to only those implementations
described above.
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