FR2968153A1 - METHOD FOR FORMING LOOPS IN CALL RETURNS - Google Patents

Abstract

When a call from VolP is sent by a calling client device (A) belonging to a first network (1), in which the session control signals are not able to convey a call forwarding counter, at destination a called client device (B) belonging to a second network (2), in which the session control signals are able to convey a call diversion counter: a) an interconnection device (10) located at the interface between said first network (1) and said second network (2) inserts in the signaling of said call a header comprising a counter displaying a zero value, and b) in the case where this call is then sent back to a third network ( 1 '), in which the session control signals are not able to convey a call forwarding counter, an interconnection device (10') located at the interface between the second network (2) and the said third network network (1 ') detects the presence, in the signa the call, of said header having a counter displaying a zero value, and interrupts call setup.

Description

The present invention relates to telecommunications networks of IP ("Internet Protocol") type, and in particular those of IP networks that are able to implement session control protocols. advanced. IP networks allow the transmission of conversational data, such as "Voice over IP" (VoIP), "Content Sharing", or "Instant Messaging".

More particularly, the present invention relates to the means put in place to ensure that a telephone call which has been the subject of call diversions between two networks having different signaling levels can only form one loop at the most. It will be said that a device-client ("User Equipment" in English) "belongs" to the network of a given operator when the user of this device-client has an account with this operator, and this, whatever the Access network used by the client device to connect to the operator network. These client devices may for example be a fixed or mobile terminal, or a residential gateway (English) or located in a company, or a network operator gateway ("Voice Gateway" in English) such as a DSLAM-SIP (DSLAM) are the initials of the words "Digital Subscriber Line Access Multiplexer" meaning "Digital Subscriber Line Access Multiplexer", it is a device that collects DSL data traffic that passes through on a number of telephone lines). In order to establish a VoIP call, the IP network to which the calling client device belongs must know the IP domain to which the called client device belongs. In IP networks, a short string of characters called "Uniform Resource Identifier" (URI) is used to identify a physical or virtual resource. The syntax of URIs is defined in RFC 3986 of the Internet Engineering Task Force (IETF). The knowledge of the URI of a resource allows (via a DNS query) to obtain the IP address of a device of the network of the operator managing this resource. Traditional advanced session control protocols, such as the H.323 protocol and the SIP protocol, use so-called "signaling" messages, which are messages allowing a terminal to request a connection with another terminal, or also messages indicating that a telephone line is busy, or signaling that the called telephone is ringing, or signaling that such telephone is connected to the network and can be attached in such or such a way.

H.323 stands for a set of communication protocols for voice, image and IP data. These protocols were developed by ITU-T. These protocols can be grouped into three categories: signaling, codec negotiation (coder-decoder), and information transport.

The SIP protocol (initials of the words "Session Initiation Protocol" meaning "Session Initialization Protocol") has been defined by the IETF in RFC 3261. This protocol allows the establishment, modification and termination of sessions. multimedia in a network using the IP protocol. In the context of the present invention, will be called "SIP network" any network using the SIP protocol for session control purposes. For example, IMS type infrastructures (initials of the words "IP Multimedia Subsystem" meaning "Multimedia subsystem over IP") constitute such "SIP networks". IMS has been defined by the 3rd Generation Partnership Project (3GPP) and TISPAN (Telecommunications and Internet Converged Services and Protocols for Advanced Networking). It is a network architecture introduced by 3GPP for mobile networks, then taken over by TISPAN for fixed networks. This architecture enables the dynamic establishment and control of multimedia sessions between two clients, as well as the reservation of resources at the level of the network for transporting multimedia streams. With this architecture, network operators can conveniently implement a management policy, provide a predetermined Quality of Service, and calculate billings to customers. The IMS currently provides access to telephony, videophone, Presence and Instant Messaging services, which it also manages. In SIP networks, there are two types of resource identifiers: those of the form "SIP-URI" as defined in RFC 3261, or those of the form "tel-URI" as defined in RFC 3966. A SIP-URI is of the form "user @ host" (for example, alice @ domain1), where the "host" part identifies the domain of the operator responsible for the user represented by the "user" part. Such a URI is of the form "tel: phone number" (for example, tel: +33123456789). The present invention relates to the return of telephone calls in IP networks. In this regard, it is recalled that "call forwarding" refers to a change in the final destination of a request, or a change in the URI of a request, when the change does not result from a decision. Routing. Call forwarding may occur when, in the request, the "user" portion of the URI is changed for any reason other than expansion or translation; a call forwarding may also occur when, in the request, only the "domain" part of the URI has been modified if this change does not result from a routing decision. Each IP network operator chooses a maximum allowed of successive referrals of the same call (up to 5 in principle, but only 1 in the usual way). Refers to the entity that invoked call forwarding. The SIP networks are able to convey, in the signaling of VoIP telephone calls, information concerning a prior call forwarding, or a plurality of prior call forwarding. This information is advantageously used by various service providers and management applications to provide extended functionality to the end user.

This call forwarding signaling can conveniently follow the recommendations of the IETF RFC 5806 "Diversion Indication in SIP" edited by S. Levy and M. Mohali (March 2010, available on the website http: // www. .rfc-editor.org / rfc / rfc5806.txt). This document provides an extension to the SIP protocol. This extension provides a call redirecting client device with the means to identify who has forwarded the call and why the call was forwarded; it defines a general SIP header, called "Diversion", which forwards to the called client device call forwarding information from proxy servers or other SIP client devices. The Diversion header is used when a proxy server, call forwarding SIP server, or SIP client device changes the final destination of the call, or when features such as call forwarding change the call forwarding. URI of a query. Call forwarding information is not inserted in the case of normal URI changes related to call routing; for example, you do not insert a Diversion header when features such as speed dial change the URI of a request. When call forwarding occurs, a Diversion header is inserted into the forwarded request or forwarded response. The Diversion header must contain a reason for call forwarding. The Diversion header contains the URI that was mentioned in the request before the call forwarding. The Diversion headers contained in a received request are not deleted or modified in the forwarded requests; likewise, the Diversion headers contained in a received response are not deleted or modified in the forwarded response. According to RFC 5806, each Diversion header has a counter indicating an integer value greater than or equal to 1, indicating the number of prior call forwardings. Generally, each counter displays the value 1 because each header represents a return. It is possible, however, that the counter has a value greater than 1 when the inserted header represents the last one in a series of several references that have not been plotted in the signaling; indeed, the counter must be able to reflect the actual number of referrals even if the identities of the different referrals, as well as the reason for each referral, are not available. On the other hand, if the counter is not present in the header, it will be counted in the same way as if it were present and equal to 1. In the event that an additional call forwarding is invoked, the server responsible for managing this additional call forwarding totals the counter values of all Diversion headers contained in the request, and allows or forbids this additional call forwarding based on the comparison between the total thus obtained and the maximum number of referrals authorized by the SIP network operator. On the other hand, some SIP networks as well as some networks other than SIP networks, in particular certain networks using the H.323 protocol without the H450.3 extension, are such that the signaling is not able to convey a reference counter. call; in the context of the present invention, it will be said that these networks are "poorly signaled networks"; by contrast, it will be said that the networks whose session control signals are able to convey a call forwarding counter are "rich signaling networks". Under these conditions, there is therefore a risk of loopback when successive calls are sent back between a lean signaling network and a rich signaling network, since it is not possible to record such a loop, for example on the basis of the number of these call diversions. To guard against such loops, the operator of a rich signaling network can naturally prohibit its subscribers to exchange calls with correspondents belonging to a lean signal network. But it goes without saying that this "solution" is not likely to satisfy subscribers. To be able to authorize these exchanges without risk of loopback, a conventional solution consists, for calls coming from signal-poor networks and entering a rich signaling network, to artificially position, in the signaling of the rich signaling network, the total number of returns recorded at a high value, or even greater than the maximum allowed by the operator of the rich signal network, so as to prohibit any call forwarding. The disadvantage of this conventional solution is that it prevents, occasionally, a subscriber to have a call forwarding (for example, forwarding on messaging), while the previous number of call forwarding is actually less than maximum allowed. Note in passing that the network RTCP ("Public Switched Telephone Network" or "PSTN"), as well as ISDN ("Integrated Services Digital Networks", "Integrated Services Digital Network" Or ISDN), are able to recognize a forwarding to another subscriber station for sending to another subscriber station. This is not the case for SIP networks, hence the choice in the state of the art to deny for anti-whistling all call forwarding from a poor signaling network. It is understood that this conventional provision can have very unfortunate consequences, for example when the initial recipient of the call is an emergency service that has invoked a call forwarding: indeed, the call forwarding will be refused when this initial call comes from a client device belonging to a poorly signaled network. The present invention thus relates to a method of anti-knocking in call forwarding. This method is notable in that, when a VoIP call is issued by a calling client device belonging to a first network, in which the session control signals are not capable of carrying a call forwarding counter. call - to a called client device belonging to a second network, in which the session control signals are able to convey a call forwarding counter, a) an interconnection device located at the interface between said first network and said second network inserts in the signaling of said call a header comprising a counter displaying a zero value, and b) in the case where this call is then returned to a third network, in which the control signals of session are not able to convey a call forwarding counter, an interconnection device located at the interface between the second network and said third network 20 - detects the presence, in the a call signaling, said header having a counter displaying a zero value, and - interrupts call setup. Note that the third network may be identical or not to said first network. It will also be appreciated that the present invention is particularly advantageous when combined with the recommendations of RFC 5806 (in particular, the meter according to the invention can be inserted by said interconnection device at the interface between the first and second network and the second network, in a Diversion header according to RFC 5806); however, it is not necessary, in order to implement the invention, to adopt any recommendation of RFC 5806. Thus, according to the present invention, when entering a signaling network rich in a call VoIP (request or response) from a network identified as being a lean signaling network, the signaling of this call includes a header whose counter displays a zero value (whereas the document RFC 5806 prescribes, remember, a counter value at least equal to 1). In the case, in particular, where the call is subsequently returned to a lean signal network, the presence in the signaling of this counter displaying a value zero will be interpreted as meaning that the call establishment must be interrupted. With these provisions, calls from poorly signaled networks are controlled, and the risk of infinite looping is discarded. The operator of the rich signaling network can thus, safely, allow its subscribers both to benefit from multiple successive references of the same call (up to the maximum allowed value), and to exchange calls with correspondents belonging to poorly signaled networks.

According to particular features, said interconnection device further inserts, in the signaling of said VoIP call, information concerning the identity of said calling client device. This identity of the caller may take a known form, for example his URI, or any other form.

It should be noted that this appellant could, if necessary, be a referee himself. Thanks to these arrangements, said interconnection equipment can conveniently determine that the call comes from a lean signal network, provided that it has been configured to consult a database constituted by the operator of the SIP network and listing networks known as poor signaling networks. According to other particular features, said interconnection device further inserts, in the signaling of said VoIP call, an indication that it is a call forwarding whose reason is unknown. Indeed, the header according to the invention can be seen as a fictitious Diversion with regard to RFC 5806. Thanks to these provisions, it can be confirmed that the header 10 considered is a header according to the invention, and not a Diversion header according to RFC 5806. Correlatively, the invention relates to various devices. It thus relates, firstly, to an interconnection device between a first network, in which the session control signals 15 are not able to convey a call forwarding counter, and a second network, in which the control signals session are able to convey a call forwarding counter. Said device is remarkable in that, when a VoIP call is issued by a calling client device belonging to said first network to a called client device belonging to said second network, said interconnection device has means for inserting in the signaling of said call a header comprising a counter displaying a zero value. According to particular features, said interconnection device furthermore has means for inserting, in the signaling of said VoIP call, information concerning the identity of said calling client device.

According to other particular features, said interconnection device also has means for inserting, in the signaling of said VoIP call, an indication that it is a call forwarding whose reason is unknown.

According to still other particular features, said interconnection device furthermore has means for inserting said counter displaying a zero value into a Diversion header according to the document RFC 5806. The invention also relates, secondly, to a device interconnection between a second network, in which the session control signals are able to convey a call forwarding counter, and a third network, in which the session control signals are not capable of carrying a reference counter. 'call. Said device is remarkable in that, when a VoIP call is returned - by an application server associated with a return belonging to said second network - to a called client device belonging to said third network, said device Interconnection has means for: detecting the possible presence, in the call signaling, of a header comprising a counter displaying a zero value, and in the case of positive detection, interrupting the call establishment. Naturally, the same interconnection device may comprise both the means of a first device as briefly described above, and the means of a second device as briefly described above. In another aspect, the invention relates to interconnection equipment comprising at least one of the devices briefly described above.

The advantages offered by these devices and interconnection equipment are essentially the same as those offered by the correlative methods succinctly set forth above. Note that it is possible to realize these devices in the context of software instructions and / or in the context of electronic circuits. The invention also relates to a computer program downloadable from a communication network and / or stored on a computer readable medium and / or executable by a microprocessor. This computer program is notable in that it includes instructions for executing the steps of the anti-knocking procedure succinctly set forth above, when run on a computer. The advantages offered by this computer program are essentially the same as those offered by said method.

Other aspects and advantages of the invention will appear on reading the detailed description below of particular embodiments, given by way of non-limiting examples. The description refers to the single figure that accompanies it and which represents an example of implementation of the invention.

As explained above, RFC 5806 defines a general SIP header called "Diversion", which contains useful information regarding prior call forwarding. This Diversion header obeys the following format: Diversion = "Diversion" ":" 1 # (name-addr * (";" diversion_params)) diversion-params = diversion-reason (diversion-counter (diversion-limit diversion-privacy (diversion-screen 1 diversion-extension diversion-reason = "reason" "_" ("unknown" ("user-busy" ("no-answer" ("unavailable" "unconditional" ("time-of-day" " do-not-disturb "" deflection "(" follow-me "" out-of-service "" away "ltoken quoted-string) diversion-counter =" counter "" _ "1 * 2DIGIT diversion-limit =" limit " "_" 1 * 2DIGIT diversion-privacy = "privacy" "_" ("full" "name" "uri" 1 "off '1 quoted-string token) diversion-screen =" screen "" _ "(" yes " For example: the parameter "name-addr" (whose presence is mandatory according to RFC 5806) could be : Carol @ C 10 (returning URI), the "diversion-reason" parameter could be: "reason = user-busy" elé is busy), the "diversion-counter" parameter could be: 15 "counter = 1" (the counter value is 1), and the "diversion-privacy" parameter could be: "privacy = full" (the returning wishes to remain anonymous). An exemplary embodiment will now be described with reference to FIG. 1. FIG. 1 represents a client device A belonging to a first IP network 1, which is a lean signaling network, for example a network using the protocol. H.323 without the H450.3 extension. This client device A sends a VoIP call to a client device B belonging to a second network 2, which is a rich signaling network, for example a SIP network implementing RFC 5806. In accordance with FIG. In the invention, the interconnection equipment 10 located at the interface between the networks 1 and 2 includes in the call signaling a header according to the invention comprising a counter displaying a zero value: "counter = 0". Preferably, this header according to the invention also comprises a parameter (of the type "name-addr") mentioning the identity of the caller, in this case: userA @ dom 1. Preferably, this header according to the invention also comprises the parameter (type "diversion-reason") following: "reason = unknown" meaning that the reason for the return is unknown. Suppose then that the client device B invoked call forwarding to a client device C belonging to a third IP network which is a lean signal network (FIG. 1 illustrates the particular case where said other network 1 'is identical to the first network 1). It will be noted in passing that, in a conventional manner, the initial call is, in certain call configurations, routed to the client device B, and is then sent back to the AS (initials of the English words "Application Server" meaning " Application Server ") 20 in charge of the client device B in case, for example, of occupation or non-response of the client device B; in other call configurations, the initial call is routed directly to the AS 20 without being sent beforehand to the client-device B (it is said that an "unconditional referral" has been set up).

In any case, in accordance with RFC 5806, the AS 20 returns the call to the client device C after inserting into the signaling a Diversion header including, on the one hand, a counter parameter with a value equal to 1, and on the other hand a "name-addr" parameter mentioning the identity of the referrer, in this case: userB @ dom2; in addition, by analogy with the recommendations of RFC 5806, the signaling retains the information received by the AS 20 and contained in the header according to the invention, namely: userA @ dom 1, and "counter = 0 ". When the call thus returned to the client device C reaches the interconnection equipment 10 '(identical to the interconnection equipment 10 in the case illustrated in FIG. 1) located at the interface between the second network 2 and the third network 1 ', this interconnection equipment 10' notes the presence in the signaling of a counter displaying a zero value (in addition to the conventional counter displaying a value equal to 1). As a result, the call setup is interrupted by the interconnection equipment 10 '. This implementation example can be immediately generalized in the event that several successive references (client device B to a client device B ', and so on - not shown in FIG. 1) have occurred in the second network 2. before the call is forwarded to the third network 1 ': the call establishment will then, as before, interrupted by the interconnection equipment 10' due to the presence in the signaling of the counter of zero value . In particular, when, as in FIG. 1, the third network 1 'is identical to the first network 1, it can be seen that the embodiment just described prevents a subsequent forwarding of the call from the client device C to the client device B (directly or indirectly).

Thus, any risk of loopback is advantageously eliminated. Still with reference to FIG. 1, this example of implementation can also be generalized in the event that said call sent by the client device A to the client device B was in fact itself the return of a call issued initially by the client device B and having succeeded (directly or indirectly) in the client device A. In this case, the SIP signaling of the initial call sent by the client device B only includes one (or several) header (s) according to RFC 5806; the establishment of this call is not interrupted by the interconnection equipment 10 when it enters the lean signal network 1. As the call is then returned from the client device A to the client device B In this case, a loop of call forwarding was formed. However, when the call is entered in the second network 2, the interconnection equipment 10 has, in accordance with the invention, inserted into the call signaling a header comprising a counter displaying a zero value. ; therefore, the establishment of a possible call forwarding from the client device B to a client device C belonging to the lean signal network 1 will be interrupted by the interconnection equipment 10, and any risk of constituting a second loop (and, consequently, of infinite looping) is advantageously discarded.

The invention can be implemented within network interconnection equipment by means of software and / or hardware components. The software components can be integrated into a conventional network node management computer program. Therefore, as indicated above, the present invention also relates to a computer system. This computer system conventionally comprises a central processing unit controlling signals by a memory, as well as an input unit and an output unit. In addition, this computer system may be used to execute a computer program including instructions for implementing any of the anti-knock methods of the invention. Indeed, the invention also relates to a downloadable computer program from a communication network comprising instructions for executing the steps of an anti-knocking method according to the invention, when it is executed on a computer. This computer program may be stored on a computer readable medium and may be executable by a microprocessor. This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any another desirable form. The invention also relates to an information carrier, irremovable, or partially or completely removable, readable by a computer, and comprising instructions of a computer program as mentioned above. The information carrier may be any entity or device capable of storing the program. For example, the medium may comprise storage means, such as a ROM, for example a CD-ROM or a microelectronic circuit ROM, or a magnetic recording medium, for example a floppy disc. ) or a hard disk. On the other hand, the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The computer program according to the invention can in particular be downloaded to a network of the type 1nternet. Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the performance of any of the anti-knocking methods of the invention.

Claims (12)

REVENDICATIONS1. Anti-knockout method in call forwarding, characterized in that, when a Voice over IP (VoIP) call is issued - by a calling client device (A) belonging to a first network (1), in which the session control signals are not able to convey a call forwarding counter - to a called client device (B) belonging to a second network (2), in which the session control signals are adapted to convey a call forwarding counter, a) an interconnection device (10) located at the interface between said first network (1) and said second network (2) inserts in the signaling of said call a header having a counter displaying a zero value, and b) in the event that this call is then sent back to a third network (1% in which the session control signals are not able to convey a call forwarding counter, a device interconnection (10 ') at the interface between the second network (2) and said third network (1 ') - detects the presence, in the call signaling, of said header having a counter displaying a zero value, and - interrupts call setup. An anti-squashing method according to claim 1, characterized in that said interconnection device (10) further inserts, in the signaling of said VoIP call, information concerning the identity of said calling client device (A). A method of anti-buckling according to claim 1 or claim 2, characterized in that said interconnection device (10) further inserts, in the signaling of said VoIP call, an indication that it is a call forwarding whose reason is unknown. 4. Anti-knocking method according to any one of claims 1 to 3, characterized in that said counter displaying a zero value is inserted in a header "Diversion" according to RFC 5806. Interconnection device (10) between a first network (1), in which the session control signals are not able to convey a call forwarding counter, and a second network (2), in which the session control signals are capable of carrying a call forwarding counter, characterized in that, when a Voice over IP (VoIP) call is issued - by a calling client device (A) belonging to said first network ( 1) - to a called client device (B) belonging to said second network (2), said interconnection device (10) has means for inserting in the signaling of said call a header comprising a counter displaying a null value. 6. Interconnection device (10) according to claim 5, characterized in that it further has means for inserting, in the signaling of said VoIP call, information concerning the identity of said calling client device (A). . 7. Interconnection device (10) according to claim 5 or claim 6, characterized in that it further has means for inserting, in the signaling of said call VoIP, an indication that it is a question of a call forwarding whose reason is unknown. 8. interconnection device (10) according to any one of claims 5 to 7, characterized in that it further has means for inserting said counter displaying a zero value in a header "Diversion" according to the document RFC 5806. An interconnection device (10 ') between a second network (2), wherein the session control signals are able to convey a call forwarding counter, and a third network (1'), wherein the session control signals are not capable of carrying a call forwarding counter, characterized in that, when a Voice over IP (VoIP) call is returned - by an application server (20) associated with a returning (B) belonging to said second network (2) - to a called client device (C) belonging to said third network (1 '), said interconnection device (10') has means for: - detecting the possible presence, in the call signaling, of a header including a counter displaying a zero value, and - in case of positive detection, abort the call establishment. Interconnection equipment, characterized in that it comprises at least one interconnection device according to any one of claims 5 to 9. 11. Non-removable or partially removable or removable data storage means having computer program code instructions for performing the steps of an anti-lock process according to any one of claims 1 to 4. Computer program downloadable from a communication network and / or stored on a computer readable medium and / or executable by a microprocessor, characterized in that it comprises instructions for the execution of the steps of a method of The anti-squirting device according to any one of claims 1 to 4 when executed on a computer.