Title: Voice over IP optimization for mobile IP
Abstract: An invention is disclosed that includes a Foreign Agent that supports Mobile IP and is configured to enable a node visiting the Foreign Agent to send IP packets including voice information via an IP address obtained from an H.323 gateway. This is accomplished, in part, by sending an agent advertisement identifying an H.323 gateway on the foreign network. A packet is received from the node, where the packet is addressed to the H.323 gateway and requests an IP address associated with a destination. A packet including the requested IP address is forwarded to the node. An IP packet addressed to the IP address and including voice information may then be received from the node. A node visiting the Foreign is capable of sending IP packets including voice information and receives an agent advertisement identifying an H.323 gateway on a foreign network associated with the Foreign Agent. The node sends a packet addressed to the H.323 gateway, where the packet requests an IP address associated with a destination. A packet including the requested IP address is received by the node. The node may then send an IP packet addressed to the IP address and including voice information from the node.
Patent Number: 6,963,918 Issued on 11/08/2005 to Leung
| Inventors:
|
Leung; Kent K. (Mountain View, CA)
|
| Assignee:
|
Cisco Technology, Inc. (San Jose, CA)
|
| Appl. No.:
|
608460 |
| Filed:
|
June 29, 2000 |
| Current U.S. Class: |
709/228; 709/238; 709/245; 370/329 |
| Intern'l Class: |
G06F 015/16; H04Q 007/21.6 |
| Field of Search: |
709/227,228,238-245,202
370/329,331
|
References Cited [Referenced By]
U.S. Patent Documents
| 4692918 | Sep., 1987 | Elliott et al.
| |
| 5016244 | May., 1991 | Massey, Jr. et al.
| |
| 5018133 | May., 1991 | Tsukakoshi et al.
| |
| 5218600 | Jun., 1993 | Schenkyr et al.
| |
| 5371852 | Dec., 1994 | Attanasio et al.
| |
| 5473599 | Dec., 1995 | Li et al.
| |
| 5572528 | Nov., 1996 | Shuen.
| |
| 5619552 | Apr., 1997 | Karppanen et al.
| |
| 5729537 | Mar., 1998 | Billström.
| |
| 5825759 | Oct., 1998 | Liu.
| |
| 5862345 | Jan., 1999 | Okanoue et al.
| |
| 6061650 | May., 2000 | Malkin et al.
| |
| 6078575 | Jun., 2000 | Dommety et al.
| |
| 6195705 | Feb., 2001 | Leung.
| |
| 6339830 | Jan., 2002 | See et al.
| |
| 6674734 | Jan., 2004 | Hsu et al.
| |
| 6766168 | Jul., 2004 | Lim.
| |
| 2002/0026527 | Feb., 2002 | Das et al.
| |
| 2002/0032751 | Mar., 2002 | Bharadwaj.
| |
| 2002/0058507 | May., 2002 | Valentine et al.
| |
| 2002/0194259 | Dec., 2002 | Flykt et al.
| |
| 2003/0182433 | Sep., 2003 | Kulkarni et al.
| |
| 2003/0208568 | Nov., 2003 | Inoue et al.
| |
Other References
Lu, et al, "Toward the PSTN/Internet Inter-Networking-Pre-PINT Implementation,"
RFC2458, Nov. 1998, pp. 1-60.
Li, et al"Cisco Hot Standby Router Protocol(HSRP )," Mar., 1998,
Network Working Group RFC 2281 (http://ftp.ietf.org/rfc/rfc2281.txt?number=2281).
Release notes for 3Com Corporation, "Conducting a Redundant Route for Network
Resiliency",Mar. 1994, NET Builder Family Bridge/Router , pp. 26-29.
J. Moy, "OSPF Version 2", RFC 1247, Jul. 19, 1991.
D. Oran, "OSI IS-IS Intra-domain Routing Protocol", RFC 1142, Feb. 1990.
Uyless Black, "TCP/IP and Related Protocols", 1992, McGraw-Hill, Inc.,
pp. 226-249.
Chambless, et al., "Home Agent Redundancy Protocol(HARP )", Oct.
27, 1997.
C. Perkins, "IP Mobility Support", Networking Working Group, RFC 2002
Oct. 1996.
|
Primary Examiner: Winder; Patrice
Attorney, Agent or Firm: Beyer Weaver & Thomas LLP
Claims
1. A Foreign Agent that supports Mobile IP, the Foreign Agent being on a foreign
network and configured to enable a mobile node that supports Mobile IP visiting
the Foreign Agent to send IP packets including voice information via an IP address
obtained from an H.323 gateway, the Foreign Agent comprising:
a processor; and
a memory, the memory storing therein the following instructions:
instructions for sending an agent advertisement, the agent advertisement identifying
an H.323 gateway on the foreign network;
instructions for receiving a packet from the mobile node, the packet being addressed
to the H.323 gateway on the foreign network and requesting an IP address associated
with a destination;
instructions for forwarding a packet including the requested IP address to the
mobile node; and
instructions for receiving an IP packet including voice information from the
mobile node, the IP packet being addressed to the IP address.
2. The Foreign Agent as recited in claim 1, further comprising:
instructions for receiving the packet including the requested IP address from
the H.323 gateway.
3. The Foreign Agent as recited in claim 1, further comprising:
instructions for determining whether the H.323 gateway has access to the requested
IP address associated with the destination;
instructions for obtaining the requested IP address from the H.323 gateway when
the H.323 gateway does have access to the requested IP address associated with
the destination; and
instructions for obtaining the requested IP address from a second H.323 gateway
located at a home network of the mobile node when the H.323 gateway does not have
access to the requested IP address associated with the destination.
4. The Foreign Agent as recited in claim 3, wherein the instructions for obtaining
the requested IP address from a second H.323 gateway located at a home network
of the mobile node comprise:
instructions for sending a request for the requested IP address to the Home Agent; and
instructions for receiving the requested IP address from the Home Agent.
5. The Foreign Agent as recited in claim 1, further comprising:
instructions for sending the IP packet addressed to the IP address to the IP address.
6. The Foreign Agent as recited in claim 1, wherein the IP address is associated
with a PSTN gateway.
7. The Foreign Agent as recited in claim 1, further comprising:
instructions for sending a registration request to a Home Agent associated with
the mobile node;
instructions for receiving a registration reply from the Home Agent associated
with the mobile node; and
instructions for forwarding the registration reply to the mobile node.
8. The Foreign Agent as recited in claim 7, further comprising:
instructions for receiving an IP packet including voice information from the
Home Agent, the IP packet being addressed to the mobile node; and
instructions for forwarding the IP packet to the mobile node.
9. The Foreign Agent as recited in claim 1, further comprising:
instructions for notifying a corresponding node having the IP address that the
mobile node is visiting the Foreign Agent.
10. The Foreign Agent as recited in claim 1, further comprising:
instructions for notifying a corresponding node having the IP address that a
care-of address of the mobile node is an address of the Foreign Agent.
11. The Foreign Agent as recited in claim 10, wherein the corresponding node
is a PSTN gateway.
12. The Foreign Agent as recited in claim 11, wherein the PSTN gateway supports
Mobile IP and wherein notifying the corresponding node having the IP address that
the care-of address of the mobile node is an address of the Foreign Agent comprises
sending a mobile IP packet including the care-of address to the PSTN gateway.
13. The Foreign Agent as recited in claim 1, further comprising:
instructions for notifying a corresponding node having the IP address that the
mobile node is no longer visiting the Foreign Agent.
14. A mobile node visiting a Foreign Agent on a foreign network and being capable
of sending IP packets including voice information via an IP address obtained from
an H.323 gateway, the mobile node comprising:
a processor; and
a memory storing therein the following instructions:
instructions for receiving an agent advertisement, the agent advertisement identifying
an H.323 gateway on the foreign network;
instructions for sending a packet from the mobile node, the packet being addressed
to the H.323 gateway on the foreign network and requesting an IP address associated
with a destination;
instructions for receiving a packet including the requested IP address; and
instructions for sending an IP packet including voice information from the mobile
node, the IP packet being addressed to the IP address.
15. The mobile node as recited in claim 14, further comprising:
instructions for saving H.323 gateway information associated with the H.323 gateway.
16. A Foreign Agent that supports Mobile IP, the Foreign Agent being on a foreign
network and configured to enable a mobile node visiting the Foreign Agent to send
IP packets including voice information via an IP address obtained from an H.323
gateway, the Foreign Agent comprising:
means for sending an agent advertisement, the agent advertisement identifying
an H.323 gateway on the foreign network;
means for receiving a packet from the mobile node, the packet being addressed
to the H.323 gateway on the foreign network and requesting an IP address associated
with a destination;
means for forwarding a packet including the requested IP address to the mobile
node; and
means for receiving an IP packet including voice information from the mobile
node, the IP packet being addressed to the IP address.
17. A mobile node visiting a Foreign Agent on a foreign network and being capable
of sending IP packets including voice information via an IP address obtained from
an H.323 gateway, the mobile node comprising:
means for receiving an agent advertisement, the agent advertisement identifying
an H.323 gateway on the foreign network;
means for sending a packet from the mobile node, the packet being addressed to
the H.323 gateway on the foreign network and requesting an IP address associated
with a destination;
means for receiving a packet including the requested IP address; and
means for sending an IP packet including voice information from the mobile node,
the IP packet being addressed to the IP address.
18. A computer readable medium for enabling a mobile node visiting a Foreign
Agent to send IP packets including voice information via an IP address obtained
from an H.323 gateway, the Foreign Agent being on a foreign network, comprising:
instructions for sending an agent advertisement, the agent advertisement identifying
an H.323 gateway on the foreign network;
instructions for receiving a packet from the mobile node, the packet being addressed
to the H.323 gateway on the foreign network and requesting an IP address associated
with a destination;
instructions for forwarding a packet including the requested IP address to the
mobile node; and
instructions for receiving an IP packet including voice information from the
mobile node, the IP packet being addressed to the IP address.
19. A computer-readable medium for enabling a mobile node visiting a Foreign
Agent to send IP packets including voice information via an IP address obtained
from an H.323 gateway, the Foreign Agent being on a foreign network, comprising:
instructions for receiving an agent advertisement, the agent advertisement identifying
an H.323 gateway on the foreign network;
instructions for sending a packet from the mobile node, the packet being addressed
to the H.323 gateway on the foreign network and requesting an IP address associated
with a destination;
instructions for receiving a packet including the requested IP address; and
instructions for sending an IP packet including voice information from the mobile
node, the IP packet being addressed to the IP address.
20. In a Foreign Agent that supports Mobile IP, a method of enabling a mobile
node visiting the Foreign Agent to send IP packets including voice information
via an IP address obtained from an H.323 gateway, the Foreign Agent being on a
foreign network, the method comprising:
sending an agent advertisement, the agent advertisement identifying an H.323
gateway on the foreign network;
receiving a packet from the mobile node, the packet being addressed to the H.323
gateway on the foreign network and requesting an IP address associated with a destination;
forwarding a packet including the requested IP address to the mobile node; and
receiving an IP packet including voice information from the mobile node, the
IP-packet being addressed to the IP address.
21. In a mobile node visiting a Foreign Agent on a foreign network, a method
of sending IP packets including voice information via an IP address obtained from
an H.323 gateway, the method comprising:
receiving an agent advertisement, the agent advertisement identifying an H.323
gateway on the foreign network;
sending a packet from the mobile node, the packet being addressed to the H.323
gateway on the foreign network and requesting an IP address associated with a destination;
receiving a packet including the requested IP address; and
sending an IP packet including voice information from the mobile node, the IP
packet being addressed to the IP address.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to Mobile IP network technology. More particularly,
the present invention relates to optimizing voice over IP in a Mobile IP environment.
2. Description of the Related Art
Mobile IP is a protocol which allows laptop computers or other mobile computer
units (referred to as "Mobile Nodes" herein) to roam between various sub-networks
at various locations—while maintaining internet and/or WAN connectivity.
Without Mobile IP or related protocol, a Mobile Node would be unable to stay connected
while roaming through various sub-networks. This is because the IP address required
for any node to communicate over the internet is location specific. Each IP address
has a field that specifies the particular sub-network on which the node resides.
If a user desires to take a computer which is normally attached to one node and
roam with it so that it passes through different sub-networks, it cannot use its
home base IP address. As a result, a business person traveling across the country
cannot merely roam with his or her computer across geographically disparate network
segments or wireless nodes while remaining connected over the internet. This is
not an acceptable state-of-affairs in the age of portable computational devices.
To address this problem, the Mobile IP protocol has been developed and implemented.
An implementation of Mobile IP is described in RFC 2002 of the Network Working
Group, C. Perkins, Ed., October 1996. Mobile IP is also described in the text "Mobile
IP Unplugged" by J. Solomon, Prentice Hall. Both of these references are incorporated
herein by reference in their entireties and for all purposes.
The Mobile IP process and environment are illustrated in FIG. 1. As shown there,
a Mobile IP environment
2 includes the internet (or a WAN)
4 over
which a Mobile Node
6 can communicate remotely via mediation by a Home Agent
8 and a Foreign Agent
10. Typically, the Home Agent and Foreign Agent
are routers or other network connection devices performing appropriate Mobile IP
functions as implemented by software, hardware, and/or firmware. A particular Mobile
Node (e.g., a laptop computer) plugged into its home network segment connects with
the internet through its designated Home Agent. When the Mobile Node roams, it
communicates via the internet through an available Foreign Agent. Presumably, there
are many Foreign Agents available at geographically disparate locations to allow
wide spread internet connection via the Mobile IP protocol. Note that it is also
possible for the Mobile Node to register directly with its Home Agent.
As shown in FIG. 1, Mobile Node
6 normally resides on (or is "based at")
a network segment
12 which allows its network entities to communicate over
the internet
4 through Home Agent
8 (an appropriately configured
router denoted R
2). Note that Home Agent
8 need not directly connect
to the internet. For example, as shown in FIG. 1, it may be connected through another
router (a router R
1 in this case). Router R
1 may, in turn, connect
one or more other routers (e.g., a router R
3) with the internet.
Now, suppose that Mobile Node
6 is removed from its home base network
segment
12 and roams to a remote network segment
14. Network segment
14 may include various other nodes such as a PC
16. The nodes on
network segment
14 communicate with the internet through a router which
doubles as Foreign Agent
10. Mobile Node
6 may identify Foreign Agent
10 through various solicitations and advertisements which form part of the
Mobile IP protocol. When Mobile Node
6 engages with network segment
14,
Foreign Agent
10 relays a registration request to Home Agent
8 (as
indicated by the dotted line "Registration"). The Home and Foreign Agents may then
negotiate the conditions of the Mobile Node's attachment to Foreign Agent
10.
For example, the attachment may be limited to a period of time, such as two hours.
When the negotiation is successfully completed, Home Agent
8 updates an
internal "mobility binding table" which specifies the care-of address (e.g., a
collocated care-of address or the Foreign Agent's IP address) in association with
the identity of Mobile Node
6. Further, the Foreign Agent
10 updates
an internal "visitor table" which specifies the Mobile Node address, Home Agent
address, etc. In effect, the Mobile Node's home base IP address (associated with
segment
12) has been shifted to the Foreign Agent's IP address (associated
with segment
14).
Now, suppose that Mobile Node
6 wishes to send a message to a corresponding
node
18 from its new location. An output message from the Mobile Node is
then packetized and forwarded through Foreign Agent
10 over the internet
4 and to corresponding node
18 (as indicated by the dotted line "packet
from MN") according to a standard internet protocol. If corresponding node
18
wishes to send a message to Mobile Node—whether in reply to a message from
the Mobile Node or for any other reason—it addresses that message to the
IP address of Mobile Node
6 on sub-network
12. The packets of that
message are then forwarded over the internet
4 and to router R
1 and
ultimately to Home Agent
8 as indicated by the dotted line ("packet to MN(1)").
From its mobility binding table, Home Agent
8 recognizes that Mobile Node
6 is no longer attached to network segment
12. It then encapsulates
the packets from corresponding node
18 (which are addressed to Mobile Node
6 on network segment
12) according to a Mobile IP protocol and forwards
these encapsulated packets to a "care of" address for Mobile Node
6 as shown
by the dotted line ("packet to MN(2)"). The care-of address may be, for example,
the IP address of Foreign Agent
10. Foreign Agent
10 then strips
the encapsulation and forwards the message to Mobile Node
6 on sub-network
14. The packet forwarding mechanism implemented by the Home and Foreign
Agents is often referred to as "tunneling."
Voice over IP (VoIP) is a term used in IP telephony for a set of facilities
for managing the delivery of voice information using the Internet Protocol (IP).
In general, this means sending voice information in digital form in discrete packets
rather than in the traditional circuit-committed protocols of the public switched
telephone network (PSTN). A major advantage of VoIP and Internet telephony is that
it avoids the tolls charged by ordinary telephone service.
ITU-T H.323 is the current standard for sending voice (audio) and video using
IP on the public Internet and within intranets. Using VoIP, an enterprise positions
a VoIP device at an H.323 gateway. The H.323 gateway receives packetized voice
transmissions from users within the company and then routes them to other parts
of its intranet (local or wide area network) or sends them over the PSTN.
An important component of an H.323 enabled network is a gatekeeper. A gatekeeper
acts as the central point for all calls within its zone and provides call control
services to registered endpoints. Gatekeepers perform two important call control
functions. The first is address translation from LAN aliases for terminals and
gateways to IP or IPX addresses. The second function is bandwidth function. A gatekeeper
is not required in an H.323 system. However, if a gatekeeper is present, terminals
must make use of the services offered by gatekeepers. Gatekeeper functionality
may be incorporated into the physical implementation of gateways.
An optional, but valuable feature of a gatekeeper is its ability to route H.323
calls. By routing a call through a gatekeeper, it can be controlled more effectively.
Service providers need this ability in order to bill for calls placed through their
network. This service can also be used to re-route a call to another endpoint if
a called endpoint is unavailable. In addition, a gatekeeper capable of routing
H.323 calls can help make decisions involving balancing among multiple gateways.
For instance, if a call to a particular destination phone number is routed through
a gatekeeper, that gatekeeper can then re-route the call to one of many gateways
based upon some routing logic. In addition, the gatekeeper typically provides an
IP address associated with the appropriate H.323 gateway.
In a Mobile IP environment, when a node roams to a Foreign Agent on a foreign
network, calls are often set up through a gatekeeper on the roaming node's home
network. This gatekeeper will then select an H.323 gateway to the PSTN that is
located on the home network associated with the roaming node's Home Agent. However,
it is important to note that the distance between the Home Agent and the Foreign
Agent may be substantial. Moreover, voice is particularly sensitive to latency.
In view of the above, it would be desirable to improve the routing path in order
to optimize voice over IP in a Mobile IP environment.
SUMMARY OF THE INVENTION
The present invention provides methods and apparatus for optimizing voice over
IP in a Mobile IP environment. This is accomplished, in part, by using a local
H.323 gateway rather than an H.323 gateway on the home network when possible. In
this manner, the routing path is minimized thereby reducing latency in the voice traffic.
In accordance with one aspect of the invention, a Foreign Agent that supports
Mobile IP is located on a foreign network and configured to enable a node visiting
the Foreign Agent to send IP packets including voice information via an IP address
obtained from an H.323 gateway. This is accomplished, in part, by sending an agent
advertisement identifying an H.323 gateway on the foreign network. A packet is
received from the node, where the packet is addressed to the H.323 gateway and
requests an IP address associated with a destination. A packet including the requested
IP address is forwarded to the node. An IP packet addressed to the IP address and
including voice information may then be received from the node.
In accordance with another aspect of the invention, a node visiting a Foreign
Agent on a foreign network is capable of sending IP packets including voice information
via an IP address obtained from an H.323 gateway. The node receives an agent advertisement
identifying an H.323 gateway on the foreign network. The node sends a packet addressed
to the H.323 gateway, where the packet requests an IP address associated with a
destination. A packet including the requested IP address is received by the node.
The node may then send an IP packet addressed to the IP address and including voice information.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram illustrating a Mobile IP network segment and associated environment.
FIG. 2 is a block diagram illustrating a system in which voice over IP may be
optimized within a Mobile IP environment in accordance with an embodiment of the invention.
FIG. 3 is a process flow diagram illustrating a control flow enabling a node
to initiate a call in accordance with an embodiment of the invention.
FIG. 4 is a process flow diagram illustrating a data flow from a node in accordance
with an embodiment of the invention.
FIG. 5 is a process flow diagram illustrating a return data flow path to the
node in accordance with a first embodiment of the invention.
FIG. 6 is a process flow diagram illustrating a return data flow path to the
node that is optimized in accordance with a second embodiment of the invention.
FIG. 7 is a process flow diagram illustrating a control and data flow that enables
packets to be received by a node when the node is no longer visiting the Foreign
Agent in accordance with an embodiment of the invention.
FIG. 8 is a block diagram of a network device that may be configured to implement
aspects of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In the following description, numerous specific details are set forth in order
to provide a thorough understanding of the present invention. It will be obvious,
however, to one skilled in the art, that the present invention may be practiced
without some or all of these specific details. In other instances, well known process
steps have not been described in detail in order not to unnecessarily obscure the
present invention.
FIG. 2 is a block diagram illustrating a system in which voice over IP may be
optimized within a Mobile IP environment in accordance with an embodiment of the
invention. When a person wishes to send and/or receive voice over an IP data network
202, the person may connect to the IP data network
202 using a router
such as a Foreign Agent
204. Through connecting to this router
204,
a person may send and receive voice in IP packets through a phone
206, a
personal computer (PC)
208 or a node such as a mobile node
210. In
order to send packets to and/or receive packets from phone
212 via PSTN
214, an IP address associated with a particular destination (e.g., phone
number) must be obtained. The destination may be a PSTN gateway
216 or another
device. In this instance, since the call is being made to the phone
212,
the destination of the IP connection is the PSTN gateway
216. Typically,
a node such as a mobile node obtains an IP address associated with a destination
from an H.323 gateway
218 on the node's home IP data network
222.
The H.323 gateway
218 provides an appropriate destination IP address to
the Foreign Agent
204. For instance, the H.323 gateway
218 may return
the IP address of a PSTN gateway
220 on the home network
222. The
Foreign Agent
204 then connects to the PSTN gateway
220 using the
obtained IP address. IP data packets including voice information may then be routed
to and from the Foreign Agent
204 via Home Agent
224.
In order to optimize voice over IP in a Mobile IP environment, the present invention
enables a local H.323 gateway
226 to be discovered by the mobile node
210
initiating the call. In accordance with one embodiment, the Foreign Agent
204
sends an agent advertisement identifying the local H.323 gateway
226 on
the foreign IP data network
202. From this agent advertisement, the mobile
node
210 may obtain and save H.323 gateway information associated with the
local H.323 gateway
226. The mobile node
210 may then send a packet
addressed to the local H.323 gateway requesting an IP address associated with a
destination. For instance, the destination may be a device or a PSTN gateway. The
Foreign Agent
204 then forwards a packet including the requested IP address
to the mobile node
210. The IP address is preferably obtained from the local
H.323 gateway
226. However, when the IP address cannot be obtained from
the local H.323 gateway
226, the IP address may be obtained from the H.323
gateway
218 on the home IP data network
222. Once the mobile node
210 obtains the IP address, the mobile node may address an IP packet including
voice information to the obtained IP address and send the IP packet via the obtained
destination address.
As described above, the data flow from a mobile node may be optimized through
a local H.323 gateway. In addition, data flow may also be optimized on the return
path to the mobile node (e.g., from a PSTN gateway). The PSTN gateway typically
sends IP packets including voice information to the node via the Home Agent
224,
which tunnels the packets to the Foreign Agent
204. The Foreign Agent
204
then forwards these IP data packets to the mobile node
210. Rather than
requiring all data packets to be sent via the Home Agent
224, the corresponding
node (e.g., PSTN gateway) may be notified by the Home Agent
224, Foreign
Agent
204 or mobile node
210 that the mobile node
210 is visiting
the Foreign Agent
204. For instance, a packet including the care-of address
associated with the Foreign Agent
204 may be sent to the corresponding node
(e.g., PSTN gateway
216). The corresponding node may then tunnel packets
directly to the care-of address. The Foreign Agent
204 may then forward
the IP data packets to the mobile node. In this manner, the transmission of IP
data packets via the return data path may similarly be optimized.
FIG. 3 is a process flow diagram illustrating a control flow enabling a node
to initiate a call in accordance with an embodiment of the invention. The Foreign
Agent advertises a local H.323 gateway on the foreign network by sending an agent
advertisement identifying the local H.323 gateway at block
302. The mobile
node receives the agent advertisement at block
304. The mobile node may
then save H.323 gateway information associated with the advertised H.323 gateway
at block
306. The mobile node then sends a packet to the learned H.323 gateway
to obtain an IP address associated with a particular destination at block
308.
For instance, the destination may be a device or a PSTN gateway where communication
with a telephone or other device over the PSTN is desired.
The local H.323 gateway may not have access to the desired IP address. Thus,
it is determined at block
310 whether the learned H.323 gateway has access
to an IP address associated with the destination. When the local H.323 gateway
does not have access to the desired destination IP address, the IP address may
be obtained at block
312 from a second H.323 gateway located at the home
network via the Home Agent. Alternatively, when the local H.323 gateway has access
to the destination IP address, the local H.323 gateway returns the IP address associated
with the destination to the mobile node at block
314. The mobile node then
initiates a call with the obtained IP address at block
316. The Foreign
Agent then sends IP data packets addressed to the obtained IP address to the IP address.
Once a call is initiated, IP packets including voice information may be sent
by the node to its specified destination. FIG. 4 is a process flow diagram illustrating
a data flow from a node in accordance with an embodiment of the invention. As described
above, once the IP address is obtained, the mobile node may send an IP packet to
the IP address. Thus, the mobile node sends an IP packet including voice information
to the Foreign Agent at block
402. The Foreign Agent then sends the IP packet
to the IP address at block
404. For instance, the IP address may identify
a PSTN gateway or other device.
Once a call is initiated, IP data packets may be sent to the mobile node. FIG.
5 is a process flow diagram illustrating a return data flow path to the node in
accordance with a first embodiment of the invention. As shown, at block
502
a packet is sent from the destination to the Home Agent. The Home Agent then tunnels
the packet to the Foreign Agent at block
504. The Foreign Agent then forwards
the packet to the mobile node at block
506.
While the method shown and described with reference to FIG. 5 enables IP data
packets to be received by a roaming node, this method is not the optimum. FIG.
6 is a process flow diagram illustrating a return data flow path to the
node that is optimized in accordance with a second embodiment of the invention.
More particularly, the corresponding node with which the mobile node is communicating
(e.g., PSTN gateway or other device) is notified of the care-of address of the
mobile node at block
602. Each PSTN gateway preferably supports Mobile IP
so that it may receive a mobile IP packet including the current care-of address
of the mobile node. The corresponding node then tunnels IP data packets to the
care-of address at block
604. The Foreign Agent identified by the care-of
address then forwards the IP data packets to the mobile node at block
606.
When the mobile node roams to a new Foreign Agent, the mobile node will be unable
to receive IP packets via the old Foreign Agent. FIG. 7 is a process flow diagram
illustrating a control and data flow that enables packets to be received by a node
when the node is no longer visiting the Foreign Agent in accordance with an embodiment
of the invention. When the mobile node leaves, it registers with its Home Agent
via a new care-of address associated with a new Foreign Agent at block
702.
The old Foreign Agent then detects that the mobile node is no longer visiting the
old Foreign Agent or, alternatively, the Home Agent notifies the old Foreign Agent
that the mobile node has left at block
704. As described above with reference
to FIG. 6, the corresponding node may correspond directly with the Foreign Agent.
Moreover, the mobile node may not necessarily de-register with the Home Agent when
it roams to the new Foreign Agent. Thus, since the Home Agent may not be aware
of whether the corresponding node and the mobile node are still communicating,
the Foreign Agent notifies the corresponding node that the mobile node is no longer
visiting at block
706. The corresponding node then re-sends the packet to
the Home Agent at block
708. The Home Agent tunnels the packet to the new
care-of address at block
710. The new Foreign Agent identified by the new
care-of address then forwards the packet to the mobile node at block
712.
The present invention provides a mechanism for discovery of a local H.323 gateway
that is located on a foreign network. Through this discovery mechanism, a node
that is roaming may send IP data packets including voice information via a shortened
route via this local H.323 gateway. In this manner, voice over IP is optimized
in a Mobile IP environment.
The invention can also be embodied as computer readable code on a computer readable
medium. The computer readable medium is any data storage device that can store
data which can thereafter be read by a computer system. Examples of the computer
readable medium include read-only memory, random-access memory, CD-ROMs, magnetic
tape, and optical data storage devices.
The apparatus (Home Agent, Foreign Agent, multicast router and/or node) of this
invention may be specially constructed for the required purposes, or may be a general
purpose programmable machine selectively activated or reconfigured by a computer
program stored in memory. The processes presented herein are not inherently related
to any particular router or other apparatus. In a preferred embodiment, any of
the Home and Foreign Agents of this invention may be specially configured routers
such as specially configured router models 2500, 2600, 3600, 4000, 4500, 4700,
7200, and 7500 available from Cisco Systems, Inc. of San Jose, Calif. A general
structure for some of these machines will appear from the description given below.
Generally, the present invention may be implemented on software and/or
hardware. For example, it can be implemented in an operating system kernel, in
a separate user process, in a library package bound into network applications,
on a specially constructed machine, or on a network interface card. In a specific
embodiment of this invention, the technique of the present invention is implemented
in software such as an operating system or in an application running on an operating system.
A software or software/hardware hybrid registration system of this invention
is
preferably implemented on a general-purpose programmable machine selectively activated
or reconfigured by a computer program stored in memory. Such programmable machine
may be a network device designed to handle network traffic. Such network devices
typically have multiple network interfaces including frame relay and ISDN interfaces,
for example. Specific examples of such network devices include routers and switches.
For example, the routers of the present invention may be specially configured routers
such as specially configured router models 1600, 2500, 2600, 3600, 4500, 4700,
7200, 7500, and 12000 available from Cisco Systems, Inc. of San Jose, Calif. A
general architecture for some of these machines will appear from the description
given below. In an alternative embodiment, the present invention may be implemented
on a general-purpose network host machine such as a personal computer or workstation.
Further, the invention may be at least partially implemented on a card (e.g., an
interface card) for a network device or a general-purpose computing device.
Referring now to FIG. 8, a router
1110 suitable for implementing
the present invention includes a master central processing unit (CPU)
1162,
interfaces
1168, and a bus
1115 (e.g., a PCI bus). When acting under
the control of appropriate software or firmware, the CPU
1162 is responsible
for such router tasks as routing table computations and network management. It
may also be responsible for updating mobility binding and visitor tables, etc.
It preferably accomplishes all these functions under the control of software including
an operating system (e.g., the Internetwork Operating System (IOS®) of Cisco
Systems, Inc.) and any appropriate applications software. CPU
1162 may include
one or more processors
1163 such as a processor from the Motorola family
of microprocessors or the MIPS family of microprocessors. In an alternative embodiment,
processor
1163 is specially designed hardware for controlling the operations
of router
1110. In a specific embodiment, a memory
1161 (such as
non-volatile RAM and/or ROM) also forms part of CPU
1162. However, there
are many different ways in which memory could be coupled to the system.
The interfaces
1168 are typically provided as interface cards (sometimes
referred to as "line cards"). Generally, they control the sending and receiving
of data packets over the network and sometimes support other peripherals used with
the router
1110. Among the interfaces that may be provided are Ethernet
interfaces, frame relay interfaces, cable interfaces, DSL interfaces, token ring
interfaces, and the like. In addition, various very high-speed interfaces may be
provided such as fast Ethernet interfaces, Gigabit Ethernet interfaces, ATM interfaces,
HSSI interfaces, POS interfaces, FDDI interfaces and the like. Generally, these
interfaces may include ports appropriate for communication with the appropriate
media. In some cases, they may also include an independent processor and, in some
instances, volatile RAM. The independent processors may control such communications
intensive tasks as packet switching, media control and management. By providing
separate processors for the communications intensive tasks, these interfaces allow
the master microprocessor
1162 to efficiently perform routing computations,
network diagnostics, security functions, etc.
Although the system shown in FIG. 8 is one specific router of the present
invention, it is by no means the only router architecture on which the present
invention can be implemented. For example, an architecture having a single processor
that handles communications as well as routing computations, etc. is often used.
Further, other types of interfaces and media could also be used with the router.
Regardless of network device's configuration, it may employ one or more
memories or memory modules (including memory
1161) configured to store program
instructions for the general-purpose network operations and mechanisms for registration
and routing functions described herein. The program instructions may control the
operation of an operating system and/or one or more applications, for example.
The memory or memories may also be configured to store tables such as mobility
binding and visitor tables, etc.
Because such information and program instructions may be employed to implement
the systems/methods described herein, the present invention relates to machine
readable media that include program instructions, state information, etc. for performing
various operations described herein. Examples of machine-readable media include,
but are not limited to, magnetic media such as hard disks, floppy disks, and magnetic
tape; optical media such as CD-ROM disks; magneto-optical media such as floptical
disks; and hardware devices that are specially configured to store and perform
program instructions, such as read-only memory devices (ROM) and random access
memory (RAM). The invention may also be embodied in a carrier wave travelling over
an appropriate medium such as airwaves, optical lines, electric lines, etc. Examples
of program instructions include both machine code, such as produced by a compiler,
and files containing higher level code that may be executed by the computer using
an interpreter.
Although illustrative embodiments and applications of this invention are
shown and described herein, many variations and modifications are possible which
remain within the concept, scope, and spirit of the invention, and these variations
would become clear to those of ordinary skill in the art after perusal of this
application. For instance, although the specification has described routers, other
entities used to tunnel packets to mobile nodes on remote network segments can
be used as well. For example, bridges or other less intelligent packet switches
may also employ the standby protocol of this invention. Moreover, although the
node is described as a mobile node, the node may also be a node that does not support
Mobile IP. For instance, the Foreign Agent may perform proxy registration on behalf
of the node by sending a registration request packet to the Home Agent and processing
a registration reply packet received from the Home Agent. Accordingly, the present
embodiments are to be considered as illustrative and not restrictive, and the invention
is not to be limited to the details given herein, but may be modified within the
scope and equivalents of the appended claims.
*
