JP2007318707A - Interconnection technique of ip communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of restricting traffic when roaming communication is carried out. <P>SOLUTION: In an interconnection system of IP communication network, a first terminal 16 of a first network 10 and a second terminal 46 of a second network 40 are subjected to interconnection through networks (20, 30) equipped with at least one NAT (Network Address Translation) function and ALG (Application Level Gateway) function. In the interconnection system, a path of control packet and a path of media packet in the mutual communication of the first terminal and the second terminal are permitted to be different. The system includes means (22, 24) for setting a path of media packet so that the media packet passes an optimum path. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an interconnection system and an interconnection method between a plurality of operators in a communication network using IP packets.

  There is a roaming service that enables the service of a contracted telecommunications carrier to be received by using the facilities of another interconnected carrier even outside the service area provided by the carrier. Next-generation networks that realize fixed or mobile communication services such as telephone calls and various broadband services based on IP packets adopt IMS (IP Multimedia Subsystem) based on the characteristics of SIP (Session Initiation Protocol) for roaming communication Support (see Non-Patent Document 1 and Non-Patent Document 2).

  In a next-generation network, when roaming communication is performed while a terminal is moving from a subscriber network to another network, a control signal packet such as SDP (Session Description Protocol) describing session capability transmitted together with SIP Are exchanged between terminals via a subscriber network in which subscriber information of terminals is managed by an HSS (Home Subscriber Server).

  A connection IP address and a port number for performing media communication are described in the control signal SDP and exchanged via an S / BC (Session Border Controller). In Non-Patent Document 2, S / BC is defined by functions of IBCH and I-BGF. The S / BC has a NAT (Network Address Translation) function that performs media stream address conversion and an ALG (Application Level Gateway) function that rewrites the contents of the protocol description (both are also referred to as “NAT / ALG function”). Therefore, when there is address conversion, the network (between terminals) is appropriately connected while rewriting the IP address and port number for media communication described in SDP or the like.

  FIG. 15 is a diagram illustrating a packet flow when communication is performed in an interconnection system in which the first and second terminals are connected to each other. FIG. 15 shows a first roaming network 10, a first terminal subscriber network 20, a second terminal subscriber network 30, and a second roaming network 40. Note that the subscriber network 20 of the first terminal is a carrier network to which the first terminal 16 is subscribed, and the subscriber network 30 of the second terminal is subscribed to the second terminal 46. It is an operator network. In FIG. 15, it is assumed that the first terminal 16 is in the first roaming network 10 and the second terminal 46 is in the second roaming network 40. The first roaming network 10 includes a P-CSCF (Proxy-Call State Control Function) 14 and an S / BC 12. The subscriber network 20 of the first terminal includes a first S / BC 22, an I / S-CSCF (Interrogate / Serving-Call State Control Function) 26, a second S / BC 24, and an HSS (Home Subscriber). Server) 28. The subscriber network 30 of the second terminal includes a first S / BC 32, an I / S-CSCF 36, a second S / BC 34, and an HSS 38. The second roaming network 40 includes a P-CSCF 44 and an S / BC 42. The first terminal 16 and the second terminal 46 are communicably connected via the first subscriber network 20 and the second subscriber network 30. A case where a connection request is made from the first terminal 16 to the second terminal 46 in the above configuration will be described. An example of a basic sequence of communication between providers is shown in FIG.

  When there is an INVITE (session establishment request) from the first terminal 16 in the first roaming network 10, the request arrives at the second terminal 46 through each of the above units in order. Here, if the second terminal 46 can talk, a 200 OK response (that is, a response that can be answered) is issued, and the 200 OK response arrives at the first terminal 16 along the reverse path. Thereby, communication is established, and communication between the first terminal 16 and the second terminal becomes possible. In this case, the S / BC operates as a SIP-UA, is a B2BUA (Back-to-Back User Agent) including a NAT function and an ALG function, and terminates a media stream. Thus, in the interconnection communication involving a plurality of providers, the control signal packet and the media packet must take the same path as shown in FIG.

  Here, the inter-operator interconnection method is generally a method in which the S / BC rewrites the media connection IP address and port number described in SDP and holds an address conversion table. The next generation network is divided into a call control signal plane (C-plane) that handles control signal packets and a transfer plane (U-plane) that handles media packets. When the address translation is performed, the address translation is performed so that the control signal packet and the media packet must pass through the same path. For this reason, the media packet becomes inefficient in terms of delay time and traffic. Further, there is a problem that the media packet path is similarly complicated as the path of the control signal is complicated.

ITU-T FG-NGN, http://www.itu.int/ITU-T/ngn/fgngn/, March 16, 2006.

ETSI TISPAN ES 283 003, “IP Multimedia Call Control Protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP) Stage 3 Protocol Specification,” Feb. 2006.

  It is an object of the present invention to provide a technology that enables media delay (call delay time) and traffic suppression in the case of performing interconnection communication between a plurality of carriers by roaming, transfer service, and the like.

  The invention according to the aspect of the present invention is an IP communication network in which at least one NAT / ALG function is provided by a first terminal in a first network and a second terminal in a second network. An interconnection system for performing interconnection via a network, wherein the control packet path and the media packet path in the mutual communication between the first terminal and the second terminal are permitted to be different The system further comprises means for setting a route of the media packet so that the media packet passes through an optimum route.

  As described above, the present invention is characterized in that the function of determining the path of the control signal and shortcutting the path as necessary is added. Specifically, a function for checking the necessity of a route shortcut and changing the processing contents of the S / BC depending on the presence or absence of the shortcut is added to the conventionally used S / BC function. In addition, this invention is materialized not only as a system but as an invention of only S / BC which implement | achieves the method and the function as described in embodiment.

  According to the present invention, in the IP communication network interconnection method, media packets are routed through an optimum route and are not routed through an extra network, so that traffic due to media communication or the like can be suppressed. Thereby, the delay time of media (sound, image, etc.) communication can be suppressed.

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a state in which media communication is optimally performed between networks in an interconnection system in which first and second terminals are mutually connected between different communication networks. In FIG. 1, the same parts as those in FIG.
In FIG. 1, as in FIG. 15, the first roaming network 10, the first terminal subscriber network 20, the second terminal subscriber network 30, and the second roaming network 40 It is shown. Note that the subscriber network 20 of the first terminal is a carrier network to which the first terminal 16 is subscribed, and the subscriber network 30 of the second terminal is subscribed to the second terminal 46. It is an operator network. In FIG. 15, it is assumed that the first terminal 16 is in the first roaming network 10 and the second terminal 46 is in the second roaming network 40. The first roaming network 10 includes a P-CSCF 14 and an S / BC 12. The subscriber network 20 of the first terminal includes a first S / BC 22, an I / S-CSCF 26, a second S / BC 24, and an HSS 28. The subscriber network 30 of the second terminal includes a first S / BC 32, an I / S-CSCF 36, a second S / BC 34, and an HSS 38. The second roaming network 40 includes a P-CSCF 44 and an S / BC 42. The first terminal 16 and the second terminal 46 are communicably connected via the first subscriber network 20 and the second subscriber network 30.

  In this case, the media packet does not follow the same route as the control signal, but may be a route that passes through the S / BC 12 in the first roaming network 10 and the S / BC 42 in the second roaming network 40. There is no need to go through the subscriber network 20 of the first terminal and the subscriber network 30 of the second terminal. Accordingly, media packets may be exchanged directly between the S / BC 12 in the first roaming network 10 and the S / BC 42 in the second roaming network 40. A method for optimizing the media packet path will be specifically described below.

  In the embodiment of the present invention, media address information described in SDP that has been rewritten to S / BC in the conventional method is temporarily or continuously stored in a control signal packet, and the S / BC controls the media address information. By extending the signal packet, media communication can be performed through an optimum route.

There are four patterns in the destination of the mobile terminal: the roaming network of the first terminal, the subscriber network of the first terminal, the subscriber network of the second terminal, and the roaming network of the second terminal. Considering the movement of both terminals, there are a total of 2 ⁴ −1 = 15 cases of roaming communication. The case of communication in which both terminals are in their respective subscriber network is not roaming communication, so 1 is subtracted. FIG. 2 is a diagram illustrating six cases out of a total of 15 roaming communication cases. Here, when the first terminal 16 and the second terminal 46 are in different roaming networks (this case is hereinafter referred to as “Category 1”), and when they are in the same roaming network (in this case) Hereinafter referred to as “Category 2”).

For category 1,
(1-1) A case where the first terminal is roaming to another operator network and the second terminal is in the subscriber operator network of the second terminal.
(1-2) When the first terminal and the second terminal are roaming to another carrier network, respectively.
(1-3) The case where the first terminal is roaming to another operator network and the second terminal is roaming to the subscriber operator network of the first terminal.
(1-4) A case where the first terminal is roaming to the subscriber network of the second terminal and the second terminal is roaming to the subscriber network of the first terminal.
There are four possible cases.

For Category 2,
(2-1) When the second terminal is roaming to the subscriber's A network of the terminal.
(2-2) When the first terminal and the second terminal are roaming to the same other operator network.
There are two possible cases.
In the above case, in classification 1 roaming, since the first terminal and the second terminal are in different networks, the S / BC of the network where the first terminal is located and the network where the second terminal is located It is only necessary to exchange media packets with other S / BCs. Further, in the roaming of category 2, since the first terminal and the second terminal are in the same network, it is only necessary to exchange media packets directly between the first terminal and the second terminal. For this reason, in order to perform communication using the optimum media packet path, it is necessary to satisfy the following three conditions.

First, in category 1 roaming,
(1) Two S / BCs on the optimum media path hold the IP addresses / port numbers of the other S / BCs in the address conversion table (NAT table).
(2) The terminal must know the IP address / port number of the S / BC of the network where it is currently located.
In the case of classification 2 roaming, the following two conditions are necessary:
(3) The terminal directly knows the IP address / port number of the partner terminal.
Is required.

  An embodiment for realizing an optimal communication method between networks that satisfies the above-described conditions in a network in which S / BC is deployed will be described in detail. First, the function of the S / BC according to an embodiment of the present invention will be described. FIG. 3 is a block diagram showing functions of the S / BC according to the embodiment of the present invention. In FIG. 3, the protocol interwork function 12a to the NAT-connected ALG function 12k have the same functions as those in the prior art, and a description thereof will be omitted. The S / BC according to this embodiment further includes a media path shortcut function 12l. This media route shortcut function 121 is a function that omits a carrier network that can omit a media packet route. This omissible operator network does not need to pass media packets, so it may or may not pass. Conventionally, as shown in FIG. 4, since the control signal is directly transmitted to the other carrier network as it is, the media packet is transmitted via all the networks. However, in the embodiment of the present invention (details will be described in the second embodiment), as shown in FIG. 5, for example, to a carrier network that wants to pass a media packet to charge in the middle of a route. On the other hand, in order not to omit the operator, the route is determined, and then a signal is transmitted to another operator network. This will be specifically described below.

(First embodiment)
What can be said in common with the roaming of the classification 1 shown in FIG. 2 is that it is optimal to establish a media communication path between the network through which the SIP signal (control signal) first passes and the network through which the SIP signal last passes. . For this purpose, as mentioned in the condition (1), it is necessary to know the address / port number of each S / BC so that two optimum S / BCs can transmit packets. However, address conversion is performed in the process in which the SIP signal passes through several networks, and the SDP information is also modified. This flow is shown in FIG. FIG. 6 is a diagram showing the flow of S / BC processing at the entrance and exit in each network through which a packet passes. In the description of the present specification, the S / BC at the exit is an S / BC that sends a signal from the inside of the network to the outside of the network, and the S / BC at the entrance is a signal from outside the network to the inside of the network. S / BC to call.

The S / BC process at the entrance of the network is as follows (step 611). The S / BC rewrites “c =” and “m =” in the SDP description in accordance with the NAT of the U-plane. For example,
c = IN IP4 SBC @ local. home_A
m = audio 3456 RTP / AVP 97 96
It can be rewritten as Note that the NAT table is held in the same manner as in the past, and as an address conversion table, for example,
SBC @ global. visit_A: 2345
⇔ SBC @ local. home_A: 3456
have.

At the exit of the network, S / BC processing is performed as follows (step 612). The S / BC rewrites “c =” and “m =” in the SDP description in accordance with the NAT of the U-plane. For example,
c = IN IP4 SBC @ local. home_A
m = audio 3456 RTP / AVP 97 96
It can be rewritten as Note that the NAT table is held in the same manner as in the past, and as an address conversion table, for example,
SBC @ local. home_A: 3456
⇔ SBC @ global. home_A: 4567
have. Therefore, in the conventional method as shown in FIG. 6A, the S / BC address of the optimum network can be notified by “c =” and “m =” in the SDP description that originally notifies the media address. Can not.

Therefore, in the first embodiment of the present invention, the following processing is performed. FIG. 6B shows the processing flow.
First, it is determined whether the SIP message is from within the network (step 621). This determination is made by, for example, S / BC (S / BC is preferable, but not limited to S / BC) using SDP media address information and the like. If it is determined in step 621 that the SIP message is from outside the network, it is determined whether the SIP message is a message returned to the local network (step 622). This determination is made in the same manner as in step 621 by using, for example, SDP (S / BC is preferable, but not limited to S / BC) using SDP media address information. In step 622, when the message is returned to the local network (Yes in step 622), the SDP media address information is corrected to that of the terminal with reference to the NAT table (step 624).
As an example of this description, for example,
c = IN IP4 SBC @ global. home_B
m = audio 6789 RTP / AVP 97 96
Such as
c = IN IP4 UE-A @ local. visit_A
m = audio 1234 RTP / AVP 97 96
a = temp SBC @ global. visit_A 2345
And so on.

If it is determined in step 622 that the SIP message is not returned to the local network (No in step 622), the SDP media address information is stored in a temporary storage area in the SDP or the like, and a flag is set ( Step 623).
That is, the S / BC temporarily stores the address information before rewriting the “c =” and “m =” lines of the SDP description in the “a = temp” line, which is another SDP area. The SDP description at this time is, for example,
c = IN IP4 SBC @ local. home_A
m = audio 3456 RTP / AVP 97 96
a = temp SBC @ global. visit_A 2345
It can be rewritten as Note that the NAT table is held in the same manner as in the past, and as an address conversion table, for example,
SBC @ global. visit_A: 2345
⇔ SBC @ local. home_A: 3456
have.

If it is determined in step 621 that the SIP message is from within the network (Yes in step 612), it is determined whether there is a flag set in the S / BC process in step 623 (step 625). If there is a flag (Yes in step 625), the S / BC writes the address information temporarily stored in a-temp back to “c =” and “m =”. And a-temp is deleted. This
c = IN IP4 SBC @ global. visit_A
m = audio 3456 RTP / AVP 97 96
It becomes. Note that the NAT table is held in the same manner as in the past, and as an address conversion table, for example,
SBC @ local. home_A: 3456
⇔ SBC @ global. home_A: 4567
have.
If there is no flag (No in step 625), the media address information in the SDP is modified to the one in this S / BC together with the NAT processing as in the prior art (step 626).

  With reference to FIG. 7, the flow of the SIP signal in classification 1 roaming will be specifically described. FIG. 7 is a diagram illustrating a sequence example of a SIP signal in classification 1 roaming. In FIG. 7, when the first terminal and the second terminal are in different roaming networks, the media packet path passing through the subscriber network of the first terminal and the subscriber network of the first terminal is An example of the case where it is omitted is shown.

The first terminal transmits the IP address and port number for media communication in the SDP description. The S / BC of the roaming network of the first terminal sets the media connection address of the terminal to the global address of the S / BC, for example,
c = IN IP4 SBC @ global. visit_A
m = audio 3456 RTP / AVP 97 96
Rewrite as follows. The address conversion table at this time is
UE-A @ local. visit_A: 1234
⇔ SBC @ global. visit_A: 2345
It has become.

When this signal is transmitted to the first S / BC of the subscriber network of the first terminal, the first S / BC corresponding to the entrance S / BC is “c =” and “m =”. The area address and the port number information are temporarily stored in another area (for example, “a-temp”). Thereafter, the “c =” and “m =” regions are rewritten as in the conventional case. At this time,
c = IN IP4 SBC @ local. home_A
m = audio 3456 RTP / AVP 97 96
a = temp SBC @ global. visit_A 2345
It becomes. The address conversion table is
SBC @ global. visit_A: 2345
⇔ SBC @ local. home_A: 3456
It has become.

Then, the second S / BC corresponding to the exit S / BC rewrites the address and port number information stored in another area (“a-temp”) to “c =” and “m =”. Later, the area is deleted. At this time,
c = IN IP4 SBC @ global. visit_A
m = audio 2345 RTP / AVP 97 96
The address conversion table is
SBC @ local. home_A: 3456
⇔ SBC @ global. home_A: 4567
It becomes.

When this signal is transmitted to the first S / BC of the subscriber network of the second terminal, the first S / BC corresponding to the entrance S / BC is the subscriber network of the first terminal. As in the first S / BC, the addresses and port number information of the “c =” and “m =” areas are temporarily stored in another area (for example, “a-temp”). Thereafter, the “c =” and “m =” regions are rewritten as in the conventional case. At this time,
c = IN IP4 SBC @ local. home_B
m = audio 5678 RTP / AVP 97 96
a = temp SBC @ global. visit_A 2345
It becomes. The address conversion table is
SBC @ global. visit_A: 2345
⇔ SBC @ local. home_A: 5678
It has become.

Then, the second S / BC corresponding to the exit S / BC rewrites the address and port number information stored in another area (“a-temp”) to “c =” and “m =”. Later, the area is deleted. At this time,
c = IN IP4 SBC @ global. visit_A
m = audio 2345 RTP / AVP 97 96
The address conversion table is
SBC @ local. home_A: 5678
⇔ SBC @ global. home_A: 6789
It becomes.

When this signal is transmitted to the S / BC of the roaming network of the second terminal, the S / BC temporarily stores the address and port number information in the “c =” and “m =” areas in another area ( For example, “a-temp”). Thereafter, the “c =” and “m =” regions are rewritten as in the conventional case. At this time,
c = IN IP4 SBC @ local. visit_B
m = audio 7890 RTP / AVP 97 96
a = temp SBC @ global. visit_A 2345
It becomes. The address conversion table is
SBC @ global. visit_A: 2345
⇔ SBC @ local. visit_B: 7890
It becomes. Finally, the second terminal can obtain the address of the S / BC that can perform the media communication by shortcut to the first terminal. That is, the address conversion table held by the S / BC of the roaming network of the second terminal is
SBC @ global. visit_A: 2345
⇔ SBC @ local. visit_B: 7890
Therefore, data can be directly exchanged between the S / BC of the roaming network of the first terminal and the S / BC of the roaming network of the second terminal.

  An example of classification 2 roaming is an embodiment in which the first terminal and the second terminal are in different roaming networks, but referring to FIG. 8, the first terminal and the second terminal are An embodiment in the case of being in the same roaming network will be described. In the following description, detailed description of the same operation as in FIG. 7 is omitted. FIG. 8 is a diagram illustrating an example of a sequence of SIP signals in classification 2 roaming. In FIG. 14, when the first terminal and the second terminal are in the same roaming network, the media packet path passing through the subscriber network of the first terminal and the subscriber network of the second terminal is An example of the case where it is omitted is shown.

In FIG. 8, the operation from the S / BC of the roaming network of the first terminal to the second S / BC of the subscriber network of the second terminal is the same as in FIG.
In the roaming communication of category 2, since the SIP signal (control signal) transmitted from the network where the first terminal is located returns to the same network again, the network of the network where the first terminal and the second terminal exist. The SDP description “c =” and “m =” lines are rewritten to the media connection address information of the terminal by S / BC. At this time,
c = IN IP4 UE-A @ local. visit_A
m = audio 7890 RTP / AVP 97 96
a = temp SBC @ global. visit_A 2345
It becomes. Thereby, since the second terminal can obtain the media address information of the first terminal, the data is directly transmitted between the first terminal and the second terminal without going through the S / BC deployed in the network. Can be exchanged.

  In FIG. 8, when the S / BC rewrites the media address information of the terminal, if there are a plurality of S / BCs in the network, the media address information of the terminal managed by the S / BC is stored in each S / BC. Since S / BC differs, the S / BC that rewrites the terminal address does not hold the address information of the terminal to be rewritten. Two methods by which the S / BC obtains terminal address information are shown.

Each S / BC manages terminal addresses in the NAT table, and centrally manages this information in the network. Therefore, a NAT table management function 53 as shown in FIG. 9 is provided in the network.
When the first S / BC 51 processes the SIP signal (control signal) and manages the correspondence information between the address of the first terminal 56 and the first S / BC 51 in the NAT table, the NAT table management function 53 in the network The correspondence information is also written, and the NAT table management function 53 manages the correspondence information. The second S / BC 52 that processes the SIP signal that has returned to the same network again determines that the SIP signal transmitted from the first terminal 56 has returned to its own network again based on the SDP address information or the like ( Step 627 in FIG. 6B), referring to the media address of the terminal from the SDP address information from the NAT table management function 53, the media address of the SDP description is obtained from the address information rewritten by another S / BC. Rewrite to the terminal address of. As a result, communication between terminals becomes possible by roaming of category 2.

In order to mutually refer to NAT table information held by a plurality of S / BCs, S / BCs in the same network are mutually connected. When the second S / BC 52 receives the media connection address and port number of the first S / BC of the same network, the second S / BC 52 receives the media connection address and port from the first S / BC 51. With reference to the media connection address information of the terminal corresponding to the number, the address information in the SDP description is rewritten with the address information of the original terminal.
Even when the NAT management function 53 is not provided, the NAT table only needs to be shared by the first S / BC 51 and the second S / BC 52 as shown in FIG.

FIG. 11 is a sequence diagram in the case of performing release of media resources and closing of pinholes in a network to be omitted in roaming communication. Since the basic sequence is almost the same as that in FIG. 7, the description of the same parts as those in FIG. 7 is omitted.
In FIG. 11, the omitted subscriber network 20 of the first terminal and the subscriber network 30 of the second terminal are networks through which the SIP signal (control signal) passes without being terminated at the terminal. Here, the entry S / BCs 22 and 32 of the subscriber network 20 of the first terminal and the subscriber network 30 of the second terminal indicate that the network is omitted in the SDP description or the like. For example, the following description is temporarily stored.
a = temp SBC @ global. visit_A: 2345
If the temporary storage line as described above is included in the signal received by the network exit S / BC 24, 34, it indicates that the own network is omitted. Accordingly, the exit S / BCs 24 and 34 open the media resources and close the pinholes of the network to which the S / BC belongs in response to the reception of the signal. The egress SBC flags a signal such as a SIP 183 Session Progress message, and performs media resource release and pinhole closure of the network to which the egress S / BC belongs.

In the above case, when there is a carrier network that does not want to omit the media packet route, the S / BC of the carrier network may be controlled to perform the process of FIG.
In the first embodiment, the media packet route optimization process is completed within each carrier network, so that control signal packets output outside the carrier network can be output in the same SDP description format as before. . Further, the S / BC media connection address and port number of the extra network are not transferred, so that it is safer from the viewpoint of security.

(Second Embodiment)
The second embodiment is characterized in that a new media address information area that cannot be rewritten by the other S / BC in the first S / BC is added to the SDP description. Specifically, for example, information on the “c =” and “m =” areas of the first S / BC is stored in lines named “a = roam-c” and “a = roam-m”. Note that the information stored in the lines named “a = roam-c” and “a = roam-m” is not the first S / BC (or the S / BC on the optimum route on the route). However, when there is a business operator who wants to pass a media packet, new media address information is added as in the via header of the SIP description. Other S / BCs do not rewrite the contents of the “a = roam-c” and “a = roam-m” lines. Each S / BC creates a NAT conversion table based on the address / port number information in the “a = roam-c” and “a = roam-m” areas. A flow chart of this S / BC process is shown in FIG. FIG. 12 is a diagram showing the flow of processing of S / BC at the entrance and exit in each network through which a packet passes in the second embodiment.

  First, it is determined whether there is a flag indicating roaming (ie, a new SDP line) in the SDP (step 900). If there is no flag indicating that the terminal is roaming in step 900, it is determined whether the terminal is roaming (step 910). This determination can be confirmed by various known methods. For example, it can be determined because the URI of the terminal is not that of the own network.

If it is determined in step 910 that roaming has not occurred, the S / BC at the entrance performs the following process (step 911).
The S / BC rewrites the “c =” and “m =” areas of the SDP description in accordance with the NAT of the U-plane. In this case, the “c =” and “m =” lines are rewritten as follows.
c = IN IP4 SBC @ local. home_A
m = audio 3456 RTP / AVP 97 96
Here, as in the prior art, the following address conversion table is held.
SBC @ global. visit_A: 2345
⇔ SBC @ local. home_A: 3456
At the exit of the network, the S / BC process is performed as follows (step 912). The S / BC rewrites “c =” and “m =” in the SDP description as follows in accordance with the NAT of the U-plane.
c = IN IP4 SBC @ local. home_A
m = audio 3456 RTP / AVP 97 96
Note that the address conversion table is similar to the conventional one, for example,
UE-A @ local. visit_A: 1234
⇔ SBC @ global. home_A: 2345
Is retained.

If it is determined in step 910 that the terminal is roaming, the S / BC at the exit of the roaming network where the terminal is located performs the following process (step 913).
The S / BC adds “a = roam-c” and “a = roam-m” lines to the SDP, and stores its own global address and port number in the area. In this case, the SDP description is
c = IN IP4 SBC @ global. visit_A
m = audio 3456 RTP / AVP 97 96
a = roam-c SBC @ global. visit_A
a = roam-m audio2345 RTP / AVP 97 98
It becomes.

Note that the address conversion table is similar to the conventional one, for example,
UE-A @ local. visit_A: 1234
⇔ SBC @ global. home_A: 2345
Is retained. This is the first S / BC process.
In step 900, if the SDP has a flag indicating roaming, it is determined from the new area whether the S / BC is the same network (step 920). This determination is performed by, for example, a URI.
If it is determined in step 920 that the S / BC is not the same network, it is determined whether or not this S / BC may be omitted from the media packet path (step 930). If not omitted, the SDP area is
c = IN IP4 SBC @ local. home_A
m = audio 3456 RTP / AVP 97 96
a = roam-c SBC @ global. visit_A
a = roam-m audio2345 RTP / AVP 97 98
Thus, newly added “a = roam-c” and “a = roam-m” are prevented from being rewritten. Here, an address conversion table is created so that packets can be transmitted to this S / BC. In this case, for example,
SBC @ global. home_A: 1234
⇔ SBC @ local. home_A: 3456
It becomes.

At the exit of the network, the S / BC process is performed as follows (step 932). The S / BC rewrites “c =” and “m =” in the SDP description as follows in accordance with the NAT of the U-plane.
c = IN IP4 SBC @ global. home_A
m = audio 3456 RTP / AVP 97 96
a = roam-c SBC @ global. visit_A
a = roam-m audio2345 RTP / AVP 97 98
a = roam-c SBC @ global. home_A
a = roam-m audio3456 RTP / AVP 97 98
Thus, new “a = roam-c” and “a = roam-m” are added to the SDP. Note that the address conversion table is similar to the conventional one, for example,
SBC @ local. home_A: 3456
⇔ SBC @ global. home_A: 4567
Is retained.

On the other hand, when the S / BC may be omitted from the media packet path in step 930, the S / BC is associated with the NAT of U-plane and “c =” and “m =” in the SDP description. Is rewritten as follows (step 933).
c = IN IP4 SBC @ local. home_A
m = audio 3456 RTP / AVP 97 96
a = roam-c SBC @ global. visit_A
a = roam-m audio2345 RTP / AVP 97 98
It becomes. Note that the address conversion table is similar to the conventional one, for example,
SBC @ global. visit_A: 1234
⇔ SBC @ local. home_A: 3456
Is retained.

Conventional processing is performed at the exit of the network (step 934). For example,
c = IN IP4 SBC @ global. home_A
m = audio 3456 RTP / AVP 97 96
a = roam-c SBC @ global. visit_A
a = roam-m audio2345 RTP / AVP 97 98
As described above, “a = roam-c” and “a = roam-m” are not deleted.

Also, if it is determined in step 920 that the S / BC is the same network, the two terminals may be in the same network, so the ingress S / BC sets the media connection address and the port number of the terminal. A local address is set (step 921). In this case,
c = IN IP4 UE-A @ local. visit_A
m = audio 1234 RTP / AVP 97 96
a = roam-c SBC @ global. visit_A
a = roam-m audio2345 RTP / AVP 97 98
It becomes. As a result, an optimum media path can be established in the category 1 roaming. An embodiment according to the above flow will be described with reference to FIG. FIG. 13 is a diagram illustrating an example of a SIP signal sequence using the second embodiment in classification 1. In the following description, detailed description of the same operation as in FIG. 7 is omitted.

First, the first terminal transmits the IP address and port number for media communication in the SDP description. The S / BC of the roaming network of the first terminal sets the media connection address of the terminal to the global address of the S / BC, for example,
c = IN IP4 SBC @ global. visit_A
m = audio 3456 RTP / AVP 97 96
It is rewritten as
a = roam-c SBC @ global. visit_A
a = roam-m audio2345 RTP / AVP 97 98
Is added to the SDP. The address conversion table at this time is
UE-A @ local. visit_A: 1234
⇔ SBC @ global. visit_A: 2345
It has become.

When this signal is transmitted to the first S / BC of the subscriber network of the first terminal, the “c =” and “m =” areas are rewritten as in the conventional case. At this time, since the added contents of “a = roam-c” and “a = roam-m” are not rewritten,
c = IN IP4 SBC @ local. home_A
m = audio 3456 RTP / AVP 97 96
a = roam-c SBC @ global. visit_A
a = roam-m audio2345 RTP / AVP 97 98
It becomes. The address conversion table is
SBC @ global. visit_A: 2345
⇔ SBC @ local. home_A: 3456
It has become.

Then, the second S / BC corresponding to the exit S / BC outputs the content of the SDP rewritten by the first S / BC as it is. At this time, the address conversion table is
SBC @ local. home_A: 3456
⇔ SBC @ global. home_A: 4567
It becomes. Hereinafter, the address conversion table is the same as that in FIG.

When this signal is transmitted to the first S / BC of the subscriber network of the second terminal, the first S / BC corresponding to the entrance S / BC is the subscriber network of the first terminal. As in the first S / BC, “c =” and “m =” are rewritten. At this time,
c = IN IP4 SBC @ local. home_B
m = audio 5678 RTP / AVP 97 96
a = roam-c SBC @ global. visit_A
a = roam-m audio2345 RTP / AVP 97 98
It becomes.

Then, the second S / BC corresponding to the exit S / BC outputs the content of the SDP rewritten by the first S / BC as it is. At this time,
c = IN IP4 SBC @ local. home_B
m = audio 6789 RTP / AVP 97 96
a = roam-c SBC @ global. visit_A
a = roam-m audio2345 RTP / AVP 97 98
It becomes.

When this signal is transmitted to the S / BC of the roaming network of the second terminal, the “c =” and “m =” areas are rewritten in the same manner as the S / BC of each entrance described above. At this time,
c = IN IP4 SBC @ local. visit_B
m = audio 7890 RTP / AVP 97 96
a = roam-c SBC @ global. visit_A
a = roam-m audio2345 RTP / AVP 97 98
It becomes. The address conversion table is
SBC @ global. visit_A: 2345
⇔ SBC @ local. visit_B: 7890
It becomes. Finally, the second terminal can obtain the address of the S / BC that can perform the media communication by shortcut to the first terminal. That is, the address conversion table held by the S / BC of the roaming network of the second terminal is
SBC @ global. visit_A: 2345
⇔ SBC @ local. visit_B: 7890
Therefore, data can be directly exchanged between the S / BC of the roaming network of the first terminal and the S / BC of the roaming network of the second terminal. In addition, about the classification 2, since what is necessary is just to combine the content demonstrated in FIG. 8, and said content, description is abbreviate | omitted.

  As another method of the IP interconnection method, the control signal packet path may be changed to take a path similar to the shortcut path of the media packet. However, when interconnecting communications between different operators, adding or changing a control signal packet route defined by standardization specifications may deteriorate the control signal packet traffic. On the other hand, in the embodiment of the present invention, the media path is short cut using an existing SIP procedure by adding a function to the S / BC. For this reason, the traffic of the media packet can be made efficient without deteriorating the traffic of the control signal packet.

  Also, the optimal media route is not available for the reason that the operator in the middle of interconnection communication wants to charge according to the usage fee or usage time of the media stream, wants to read the contents of the media stream, or provides other additional services. However, if it is desired to use the media route, it is possible to use the optimum route possible through these operator networks. FIG. 14 shows such a manner. FIG. 14 is a diagram illustrating a packet flow when communication is performed via an operator on the way in the interconnection communication in the interconnection system in which the first and second terminals are connected to each other. In the case of FIG. 14 as well, the first embodiment and the second embodiment can be applied as they are, and detailed description thereof will be omitted. As described above, in the second embodiment, since all the address information of the S / BC to which the media packet is to be transmitted is transferred by the control signal packet, more information for selecting a route can be transferred.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention at the stage of implementation.
For example, in the above description, only roaming communication has been described. However, the present invention can be applied not only to roaming communication but also to communication between a plurality of providers due to a transfer service or the like.
Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements.

  In addition, for example, even if some structural requirements are deleted from all the structural requirements shown in each embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the effect of the invention Can be obtained as an invention.

FIG. 2 is a diagram illustrating an optimum media communication between networks in an interconnection system in which first and second terminals are connected to each other between different communication networks. It is the figure shown about the various cases of roaming communication according to the movement destination of a portable terminal. It is a block diagram which shows the function of S / BC which concerns on one Embodiment to this invention. It is a figure which shows the flow of the control signal in the past. It is a figure which shows the flow of the control signal in this invention. It is a figure which shows the flow of a process of S / BC of the entrance and exit in each network through which a packet passes. It is a figure which shows the example of a sequence of the SIP signal in the roaming of classification 1. It is a figure which shows the example of a sequence of the SIP signal in the roaming of classification 2. It is a figure which shows the example in the case of deploying the NAT table management function 53 in the interconnection system which connects a 1st and 2nd terminal mutually. It is a figure which shows the example in the case of not providing the NAT management function 53 in the interconnection system which connects a 1st and 2nd terminal mutually. FIG. 11 is a sequence diagram in a case where a network resource to be omitted and a pinhole are closed in roaming communication. It is a figure which shows the flow of a process of S / BC of the entrance and exit in each network where a packet passes in 2nd Embodiment. It is a figure which shows the example of a SIP signal sequence using 2nd Embodiment in the classification | category 1. FIG. It is a figure which shows the flow of a packet in the case of communicating via a provider in the middle in the interconnection communication in the interconnection system which mutually connects the 1st and 2nd terminal. It is a figure which shows the flow of a packet in the case of communicating in the interconnection system which connects a 1st and 2nd terminal mutually. It is a figure which shows the example of the basic sequence of communication between providers.

Explanation of symbols

10: First roaming network 12 ... S / BC (session border controller)
12a ... Protocol interwork function 12l ... Media path shortcut function 14 ... P-CSCF
16 ... First terminal 20 ... First subscriber network 22 ... First S / BC
24 ... Second S / BC
26 ... I / S-CSCF
28 ... HSS
30 ... Second subscriber network 32 ... First S / BC
34 ... Second S / BC
36 ... I / S-CSCF
38 ... HSS
40 ... second roaming network 42 ... S / BC
44 ... P-CSCF
46 ... second terminal

Claims (11)

In an IP communication network, a first terminal in a first network and a second terminal in a second network are interconnected via a network having at least one NAT / ALG function. In a connection system, wherein the path of the control packet and the path of the media packet in the mutual communication between the first terminal and the second terminal are permitted to be different,
An interconnection system comprising means for setting a route of the media packet so that the media packet passes through an optimum route. 2. The interconnection system according to claim 1, wherein the setting unit omits a route that does not pass through the network so that the media packet does not need to pass through the network. The interconnection system according to claim 1 or 2, wherein each of the networks includes a session border controller.
In a network where the media packet does not need to pass, the session border controller on the ingress side temporarily writes in the area before rewriting the area where the address and port number are described in the SDP (Session Description Protocol) description. The stored address and port number information is stored in another area, and the session border controller on the exit side writes the temporarily stored address and port number information in the area where the address and port number are described in the SDP description. An interconnection system characterized by output after returning. In the interconnection system according to claim 1 or 2, when the first terminal and the second terminal are in the same network, the session border controller corresponding to the network entrance of the second terminal is: The media connection address and the port number of the first terminal are temporarily stored in another area, and then the media connection address and the port connection number are rewritten to the first terminal address information on the calling side. Connection system. 3. The interconnection system according to claim 1, wherein when the first terminal and the second terminal are in the same network, the session border controller arranged in the network uses SDP media address information. And determining that the first terminal and the second terminal are in the same network, and using the media address information without passing through the session border controller, the first terminal and the second terminal. An interconnection system, wherein the media addresses of the first and second terminals are changed so that can communicate directly with each other. The interconnection system according to claim 1 or claim 2,
Means for determining whether at least one of the first terminal or the second terminal is roaming;
Means for adding a flag indicating roaming to the SDP if the determination means determines that roaming is present and there is no flag indicating that roaming is present in SDP (Session Description Protocol) An interconnect system further comprising: 7. The interconnection system according to claim 6, wherein the contents of the flag are a media connection address and a port number of a session border controller of a roaming network. In an IP communication network, a first terminal in a first network and a second terminal in a second network are interconnected via a network having at least one NAT / ALG function. A connection method, wherein the control packet path and the media packet path in the mutual communication between the first terminal and the second terminal are allowed to be different,
An interconnection method characterized by determining and setting a route of the media packet so that the media packet passes through an optimum route. 5. The interconnection system according to claim 4, further comprising means for centrally holding address translation information held by each session border controller in the network when there are a plurality of session border controllers in the same network. ,
An interconnection system, wherein a session border controller refers to the address translation information to rewrite the media connection address and the port connection number to the first terminal address information on the calling side. 5. The interconnection system according to claim 4, wherein when there are a plurality of session border controllers in the same network, the session connection controllers refer to each other to obtain the media connection address and the port connection number. An interconnection system, wherein the first terminal address information is rewritten. 4. The interconnection system according to claim 3, wherein the session border controller on the egress side of the network omitted from the media packet path specifies an area in which the address and port number are described in the SDP description as an ingress session border of the network. Interconnection characterized by terminating the media resource reservation of the omitted network and closing the pinhole of the session border controller, triggered by writing back to the address and port number information temporarily stored by the controller system.

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