U.S. patent application number 09/072809 was filed with the patent office on 2001-08-09 for optimum routing of calls over the public switched telephone network and the internet.
Invention is credited to DUNN, JAMES PATRICK, KOZIK, JACK.
Application Number | 20010012355 09/072809 |
Document ID | / |
Family ID | 22109885 |
Filed Date | 2001-08-09 |
United States Patent
Application |
20010012355 |
Kind Code |
A1 |
DUNN, JAMES PATRICK ; et
al. |
August 9, 2001 |
OPTIMUM ROUTING OF CALLS OVER THE PUBLIC SWITCHED TELEPHONE NETWORK
AND THE INTERNET
Abstract
A method and apparatus for selectively establishing a connection
via a telephone network, or via the Internet. A network access
switch decides whether to use the telephone network or the
Internet. If connections are established using the Internet, the
establishment of connection is controlled using existing CCS7
interoffice signaling messages. Advantagesouly, this permits most
of the switching control software to be retained and allows the
access switches to interface with the present array of operations
support systems.
Inventors: |
DUNN, JAMES PATRICK;
(NORTHVILLE TOWNSHIP, IL) ; KOZIK, JACK;
(NAPERVILLE, IL) |
Correspondence
Address: |
WERNER ULRICH
434 MAPLE STREET
GLEN ELLYN
IL
601373826
|
Family ID: |
22109885 |
Appl. No.: |
09/072809 |
Filed: |
May 5, 1998 |
Current U.S.
Class: |
379/230 ;
379/221.01 |
Current CPC
Class: |
H04L 61/00 20130101;
H04L 61/10 20130101; H04L 2012/6486 20130101; H04M 7/0009 20130101;
H04M 7/0006 20130101; H04L 2012/6475 20130101; H04L 2012/6443
20130101; H04L 2012/6472 20130101; H04L 12/6418 20130101; H04Q
3/0025 20130101 |
Class at
Publication: |
379/230 ;
379/221.01 |
International
Class: |
H04M 007/00 |
Claims
1. A method of establishing a connection between two switches, both
of which have access to a telephone network and the Internet,
comprising the steps of: responsive to receipt of a request to
establish a telephone connection, determining whether to establish
the connection using a telephone network, or using the Internet; if
a decision is made to establish the connection using the telephone
network, establishing the connection in accordance with procedures
of the prior art; if a decision is made to establish the connection
using the Internet, transmitting an (LAM) initial address message
over an interoffice signaling network to the terminating switch,
the IAM including an Internet Protocol address of the originating
switch; responsive to receipt of said IAM, transmitting an
acknowledgment message comprising an IP (Internet Protocol) address
of said terminating switch over said interoffice signaling network;
establishing an Internet connection between said originating and
said terminating switch, using said IP addresses; and confirming
establishment of said connection by another interoffice signaling
message between the two switches sent over said interoffice
signaling network.
2. The method of claim 1 wherein said telephone network is a
private network, and the step of establishing the connection in
accordance with procedures of the prior art comprises the step of
establishing a private network connection in accordance with
procedures of the prior art for private network connections.
3. The method of claim 1 wherein said Internet connection is
established over a private Internet Protocol network.
4. The method of claim 1 wherein the step of establishing an
Internet connection comprises the step of: checking that a call
identifier returned in the acknowledgment message is the same as a
call identifier sent in the IAM.
5. The method of claim 1 further comprising the steps of: selecting
an IP address in the switch transmitting said IAM; selecting a
different IP address in the switch transmitting said acknowledgment
message; and changing to said different IP address in the switch
transmitting said IAM.
6. The method of claim 1 wherein said interoffice signaling network
is a CCS7 network.
7. In a network access switch, apparatus for controlling the
establishment of a connection to another network access switch,
wherein both switches have access to a telephone network and the
Internet, comprising: means for accessing an interoffice signaling
network; means for establishing a connection to said telephone
network; means for establishing a connection to the Internet;
processor means for controlling transmission of messages over said
interoffice signaling network, for receiving messages from said
interoffice signaling network, and for controlling said means for
establishing a connection in said network access switch; said
processor means, operative under program control for: responsive to
receipt of a request to establish a telephone connection,
determining whether to establish the connection using a telephone
network, or using the Internet; if a decision is made to establish
the connection using the telephone network, establishing the
connection in accordance with procedures of the prior art; if a
decision is made to establish the connection using the Internet,
controlling transmission of an initial address message over said
interoffice signaling network to the terminating switch, the IAM
(initial address message), including an Internet Protocol address
of the network access switch; responsive to receipt of an
acknowledgment message from said another switch, said
acknowledgment message comprising an IP (Internet Protocol) address
of said terminating switch over said interoffice signaling network,
controlling the establishment of an Internet connection between
said network access switch and said another network access switch,
using said IP addresses; and confirming establishment of said
connection by controlling transmission of another interoffice
signaling message to said another switch.
8. The apparatus of claim 7 wherein said means for accessing an
interoffice signaling network comprises means for accessing a CCS7
network.
9. The apparatus of claim 7 wherein said means for establishing a
connection to a telephone network comprises means for establishing
a connection to a private telephone network.
10. A method of establishing an Internet voice connection between
two switches, comprising the steps of: transmitting an (IAM)
initial address message over an interoffice signaling network to
the terminating switch, the IAM including an Internet Protocol
address of the originating switch; responsive to receipt of said
IAM, transmitting an acknowledgment message comprising an IP
(Internet Protocol) address of said terminating switch over said
interoffice signaling network; establishing an Internet connection
between said originating and said terminating switch, using said IP
addresses; and confirming establishment of said connection by
another interoffice signaling message, transmitted over said
interoffice signaling network between the two switches.
11. The method of claim 10 wherein said interoffice signaling
network is a CCS7 network.
12. In a network access switch, apparatus for controlling the
establishment of a voice connection via the Internet to another
network access switch, comprising: means for accessing an
interoffice signaling network; means for establishing a connection
to the Internet; processor means for controlling transmission of
messages over said interoffice signaling network, for receiving
messages from said interoffice signaling network, and for
controlling said means for establishing a connection in said
network access switch; said processor means, operative under
program control for: controlling transmission of an initial address
message over said interoffice signaling network to the terminating
switch, the IAM (initial address message), including an Internet
Protocol address of the network access switch; responsive to
receipt of an acknowledgment message from said another switch, said
acknowledgment message comprising an IP (Internet Protocol) address
of said terminating switch over said interoffice signaling network,
controlling the establishment of an Internet connection between
said network access switch and said another network access switch,
using said IP addresses; and confirming establishment of said
connection by controlling transmission of another interoffice
signaling message over said interoffice signaling network to said
another switch.
13. The apparatus of claim 12 wherein said means for accessing an
interoffice signaling network comprises means for accessing a CCS7
network.
Description
TECHNICAL FIELD
[0001] This invention relates to arrangements for switching calls
from central offices switches to the public switched telephone
network, or to a fast packet network such as the Internet, in such
a way as to incur lowest costs for a call.
PROBLEM
[0002] The Internet has made it possible to use a radically
different network for carrying voice calls. This network is
becoming cost competitive with the public switched telephone
network.
SOLUTION
[0003] Applicants have recognized that a problem with the prior art
is that it is difficult to assign individual calls served by a
central office switching system to a choice of the Internet and the
public switched telephone network. The problem is especially
aggravated by the difficulty of making extensive changes in the
call routing arrangements because of the widespread use of
different standard protocols for use with the public switched
telephone network, and for use with the Internet.
[0004] The above problem is solved and an advance is made over the
prior art in accordance with this invention wherein a decision is
initially made in an originating switching system to select a
public switched telephone network trunk, or an Internet connection;
if an Internet connection is selected, an interoffice signaling
message such as the CCS7 initial address message, (IAM), contains
both a call identification, and an Internet Protocol (IP), address
of the originating switch. The terminating switch in its
acknowledgment, returns an Internet Protocol address of the
terminating switch for a communication session. The originating
office then sends an identification of the call, in this embodiment
the prior art PSTN (Public Switched Telephone Network) circuit
identifier code, and of the far end IP address in a real time
protocol/IP (RTP/IP) packet over the Internet to the terminating
switch. The terminating switch then is able to associate the
Internet connection with the type of information that has been
received in the IAM over the CCS7 network; the terminating switch
is able to complete the connection from the terminating switch to
the called customer using the information in the IAM in the
standard way. The voice packets sent and received over the Internet
are then interfaced in the originating switch and the terminating
switch with a Vocoder which converts these Internet packets into a
PCM (pulse code modulation) bit stream for transmission to the
calling and called customers' switches, thence, as an analog signal
or PCM digital telephone signal to the customers. Advantageously,
even though the call is being served by Internet facilities, the
call set-up operations can be performed in basically the same way
that they are performed using only the public switched telephone
network, (PSTN), so that the effect on the call processing program
is minimized. In addition, the path across the Internet is verified
by an exchange of call identifications and Internet addresses in
both directions.
[0005] The changes in the call processing program and procedures
include:
[0006] 1. Internet Protocol (IP) address administration is
required.
[0007] 2. Vocoders must be connected to calls routed over the
Internet.
[0008] 3. Matching Vocoders must be selected in the two switches
terminating an Internet connection.
[0009] 4. The IP address is validated to secure the Internet
against intrusion by unauthorized users (hackers).
[0010] 5. Call identification numbers and IP addresses of the two
ends are bonded.
[0011] 6. An IP address field must be added to the IAM (Initial
Address Message) and ACK (Acknowledgment) messages.
[0012] 7. A new class of service is added for Internet
connections.
[0013] 8. New billing options can be provided for Internet
connections.
[0014] However, advantageously, by using procedures that are linked
to the type of call setup used with the PSTN (Public Switched
Telephone Network), the existing array of Operations Support
Systems can continue to be used for operations, administration,
maintenance, installation, traffic measurements, and provisioning.
For example, the "no circuit available" counts maintained for most
trunk groups can be used as they are today, to request the addition
of trunks, or, in this case, addition of Internet network
capacity.
BRIEF DESCRIPTION OF THE DRAWING
[0015] FIG. 1 is a block diagram illustrating the basic operation
of Applicants' invention;
[0016] FIG. 2 is a flow diagram illustrating operations at an
originating switch; and
[0017] FIG. 3 is a flow diagram illustrating operations at a
terminating switch.
DETAILED DESCRIPTION
[0018] FIG. 1 illustrates the operation of Applicants' invention.
An originating station 25 is connected via a local public switched
telephone network 21 to an originating toll access switch 1. The
toll access switch 1 contains a Protocol handler/vocoder 3 for
interfacing between Internet voice packets, and the pulse code
modulation, (PCM), bit stream received from the local PSTN 21. Note
that in some cases the originating station may be directly
connected to the toll access switch 1. The toll access switch of
this example is a specific example of a network access switch,
i.e., a switch for accessing a network such as the Internet or a
toll network.
[0019] Each of the toll access switches has a program controlled
processor, such as processor 5 of switch 1, for controlling
establishment of Internet and telephone network connections,
receiving and controlling transmission of interoffice signaling
messages. Each switch also has a switching network such as network
6 of switch 1 for establishing connections between the incoming
local PSTN and the Internet or the toll network.
[0020] The terminating station 26 is connected via local PSTN 22 to
the terminating toll access switch 2, which contains a protocol
handler/vocoder 4 for interfacing between the voice packets
transmitted over the Internet 10, and a PCM stream to the local
PSTN 22. Note that at the terminating end also the terminating
station 26 may be directly connected to the terminating toll access
switch 2.
[0021] When the originating switch 1 receives a request to
establish a connection from originating station 25, the originating
toll access switch 1 first tests whether the call should be sent
over the telephone toll network 11 which interconnects originating
toll access switch 1, and terminating toll access switch 2, or via
the Internet 10, which also interconnects the two toll access
switches. The decision on whether to select the telephone toll
network 11, or the Internet 10, can be based on a number of
factors. One of the most important factors is the charge for the
use of the Internet, or the telephone toll network; if the owner of
the toll access switch is not also the owner of the telephone toll
network, then the charges for the telephone connection should
probably be competitive, otherwise, only one of the two networks
will be used. Another factor which is taken into account in making
the decision on how to route the call, is the present state of the
two networks, whether either one is presently overloaded. In
addition to these decisions which are based on the sate of the
Internet and telephone network, the decision can be based on
customer input. A customer may have a class of service which
requires that all toll calls are routed over the Internet, or that
all toll calls are routed over the telephone network. Additionally,
dialed information, such as one or more preliminary digits or
symbols, can be used to specify that a particular call or series of
calls are to be routed over the Internet, or are to be routed over
the telephone network.
[0022] In accordance with this embodiment, the well known standard
H.323 protocol is used for actually transmitting data representing
voice on established stable calls. However, protocols using CCS7
signaling are used to establish the connection. In this embodiment,
CCS7 is the interoffice signaling system of choice. Advantageously,
the protocols using CCS7 are in existence and have already been
integrated into the software of the toll access switches. This
allows, for example, interfaces with existing operations support
systems, to be essentially maintained. In contrast, a great deal of
new software would be required to try to implement call set-up
using the prior art H.323 protocol.
[0023] If the originating toll access switch decides to route the
call over telephone network 11, this function is carried out in the
manner of the prior art. If, however, the decision is made to route
the call over the Internet 10, then a series of packets are
exchanged between the originating toll access switch 1, and the
terminating toll access switch 2. Initial address message, (LAM 40)
is sent from the originating toll access switch 1 to the
terminating toll access switch 2 over the CCS7 network 5. The IAM
40 contains a call identifier 41, and in accordance with the
principles of Applicants' invention also contains the Internet
Protocol address of switch 1, (IP 1), in field 42 of the IAM 40. In
response to receipt of IAM 40, terminating toll access switch 2
returns an IAM acknowledgement message 45, which also contains the
call identifier 46, and in accordance with Applicants' invention,
the Internet Protocol address, IP 2, of the terminating toll access
switch 2 in field 47. As a result of this exchange of initial
address message and acknowledgment, both the originating and the
terminating access switch have been informed of each other's
Internet Protocol address, and the terminating toll access switch
has been informed of the identification of the terminating station,
(in the initial address message), so that the terminating toll
access switch can subsequently establish a connection via local
PSTN (Public Switched Telephone Network) 22 to the terminating
station 26. Next, in order to establish an Internet connection
between switches 1 and 2, switch 1 sends a packet, including the
call identification, and including the identification of switch 2,
(IP 2), over the Internet 10 to terminating toll access switch 2.
Terminating toll access switch 2 responds by returning a packet
including the call identification, and headed by the identification
of switch, (IP 1), and the two switches are enabled to communicate
over the Internet since each knows the other's identification, and
since the packets for the conversation can be tagged by the call
identification. The call set up is completed when switch 2 sends
the standard CCS7 Setup Complete Message when Station 26 goes
off-hook.
[0024] FIG. 2 is a flow diagram illustrating operations performed
in the originating toll access switch. The origination is detected,
(Action Block 201), and the toll access switch analyzes the digits
of the call, (Action Block 203). The originating toll access switch
then makes the decision of how to route the call, (Action Block
205). Test 207 is used to determine whether the decision has been
made to route the call over the Internet. If a decision has been
made to not route the call over the Internet, then normal call
set-up is performed, (Action Block 209). If a decision has been
made to use the Internet for routing the call, then an initial
address message (IAM) is generated which includes the Internet
Protocol address of the originating switch, (Action Block 211).
This message is sent over the CCS7 network. Test 213 determines
whether the originating toll access switch received an
acknowledgment, a return from the far end, i.e., the terminating
toll access switch. If not, an attempt is repeated to send the IAM
message. If an acknowledgment has been received, then the
acknowledgment had returned the Internet Protocol address of the
terminating toll access switch, (see below with respect to Action
Block 307). The originating toll access switch then inserts the
call identification of the call, and the far end Internet Protocol
address into a Real Time Protocol/Internet Protocol, (RTP/IP),
packet and sends this packet over the Internet with the address of
the far end terminating toll access switch, (Action Block 215).
Test 217 determines whether an acknowledgment to that RTP/IP packet
had been received over the Internet; if not, then the originating
switch waits a certain amount of time before making a second
attempt to send the packet. CCS7 procedures, including
Acknowledgment timers are used when necessary to force call
abandonment. Once the acknowledgment has been received over the
Internet, (note that the sending toll access switch knows where to
send the acknowledgment because it has previously received IP-1 and
the identity of the originating toll access switch in the IAM
transmitted over the CCS7 network). A voice path bond exists
between the two switches and this bond is acknowledged via a CCS7
message, (Action Block 219). The bond messages are packets 50 and
55 (FIG. 1); the bond comes from validating that the values
correspond in both switches. The two switches are now ready to send
and receive voice packets which in their respective Vocoders will
be converted into PCM streams for transmission to the originating
and terminating stations, (Action Block 221).
[0025] FIG. 3 is a flow diagram illustrating operations performed
by the terminating toll access switch. The terminating toll access
switch is first informed of the call by receiving an IAM message,
(transmitted in Action Block 211, FIG. 2), over the CCS7 network,
(Action Block 301). Test 303 is used to determine whether an
Internet connection has been selected. This decision can be made
based on whether or not there is an IP address in the IAM message.
If not, then normal call set-up procedures are used, (Action Block
305). If it is recognized that the connection is to be established
using the Internet, and this is recognized because an Internet
Protocol address has been included in the received IAM message,
then the terminating toll access switch sends an acknowledgment
message which includes the call identifier to associate the message
with the proper call, and the IP address of the terminating toll
access switch (Action Block 307). Subsequently, the terminating
toll access switch sends an RTP/IP packet, including the call
identifier, the IP address of the originating toll access switch,
and an RTP/IP packet transmitted via the Internet to the
originating toll access switch.
[0026] Note that a toll access switch may have several IP
addressees representing different segments of the trunk plant
connected to the Internet. Only the IP address of the selected
group of trunks is sent and is used for this connection.
[0027] Test 311 is then used to determine whether a voice path
acknowledgment has been received over the CCS7 link, (this
corresponds to the message sent in Action Block 219, FIG. 2). If
so, then the two switches are ready to send and receive voice
packets.
[0028] The above arrangements can also be used for private
networks, wherein private network access switches replace the toll
access switches. Such private network can use private facilities;
private facilities may be dedicated, leased, or leased for periods
of time.
[0029] This preferred embodiment uses the protocols described
above. Other protocols such as ISUP which is supported by CCS7 can
also used for some, or all of the steps described above.
[0030] More than one IP address can be used by an originating
switch to communicate with a terminating switch. For example, if
several different Internet subnetworks connect the two switches, a
different IP address would be used for each subnetwork to ensure
that a call is transmitted over a selected subnetwork.
[0031] The above is only one preferred embodiment of Applicants'
invention. Many alternatives will be apparent to those of ordinary
skill in the art. The invention is only limited by the attached
claims.
* * * * *