FR2865595A1 - METHOD FOR FILTERING EXCHANGED MEDIA IP FLOW PACKETS IN A TELECOMMUNICATION NETWORK - Google Patents

Abstract

The present invention relates to a method of filtering IP media stream packets exchanged in a telecommunications network (6) between a source termination (2) and a destination termination (4) during a conversational session described by the description protocol. Session Description Protocol (SDP) and signaled by the Session Initialization Protocol (SIP). This method comprises the following steps: - constructing a logical filter that can be parameterized by information identifying the source termination (2) and the destination termination (4) involved in said session, - memorizing said logical filter, - and during the phase of initialization of said session, supplementing the stored filter with parameters exchanged by said terminations (2, 4) via SIP signaling.

Description

2865595 1

  METHOD FOR FILTERING MEDIA IP FLOW PACKETS

  EXCHANGES IN A TELECOMMUNICATION NETWORK

DESCRIPTION

TECHNICAL AREA

  The invention is in the field of telecommunications and relates more specifically to a method of filtering IP media stream packets exchanged in a telecommunication network between a source termination and a destination termination during a conversational session described by the protocol. Session Description Protocol (SDP) session description, which is signaled by the Session Initialization Protocol (SIP).

  The invention also relates to a device for implementing this method.

  Recall that SIP is a protocol for managing call signaling in an IP network and establishing interactive multimedia communications between two terminals connected to the IP network, and that SDP is a textual protocol for describing multimedia sessions in view, for example , to announce these sessions, to invite these sessions or to describe any other operation aimed at providing a user with the necessary resources to enable him to have access to telecommunication services.

  STATE OF THE PRIOR ART When a first terminal connects to a second terminal during a conversational session via an IP network, the data packets exchanged between the two terminals must be identified in order to perform selective processing on the streams. media exchanged.

  Generally, these packets contain the headers that are analyzed by an intermediate network element designated hereinafter by the expression ERI (Middlebox in English) and which performs a filtering of exchanged packets according to the following parameters: - IPsource address: representing the IP address of the source termination of the media stream, Address I Pdestination: representing the IP address of the destination termination of said stream, - Protocol: representing the transport protocol used to convey the media stream, generally this protocol is the UDP (For User Datagramm Protocol in English).

  - Portsource, destination: is a number associated with a service or network application.

  The ERI (Middlebox) cooperates with the server of an application software application ALG (Application Layer Gateway in English) to examine the traffic and assist the ERI in the realization of flow control filters for example or to perform any operation allowing the ERI to fulfill its function, notably the modification of the data of the flow, the filtering of flows etc ...

  There is known a first method of the prior art for allowing an Middlebox to filter the IP packets of the media stream when this media stream is signaled by the SIP / SDP protocols for (Session Initialization Protocol / Session Description Protocol, in English). This method consists in extending the SDP protocol to allow the client installation to signal the couple (IPsource address, POrtsource) of said packets. An example of an extension of the SDP protocol that allows this method to be implemented is defined in http://www.ietf.org/internetdrafts/draft-ietf-mmusic-sdp-srcfilter-02.txt.

  A second known method is to extend the SDP protocol or the SIP protocol and the protocol for transporting the media streams, example RTP (for Real Time Transport Protocol in English), so that the client installations can include a token in the call signaling.

  The ALG passes this token to the ERI to receive the media streams, the latter includes in its filtering criteria the verification of the received token. An example of implementation of this method is described in http: //wwwietf.orq/rfc/rfc3313.txt.

  A disadvantage of the methods described above is that they are limited only to client installations that support an SDP extension.

  A third method of the prior art to allow an Middlebox to filter the IP packets of the media stream consists of filtering in two phases: In the first phase, the ALG positions in the Middlebox filters constituted by the 2865595 4 informations ( IPdestinationr Portdestinationr Protocol) that are present in the SDP body of a SIP message. These filters correspond to the reception addresses of the media streams indicated in the SDP body of the SIP message received by the ERI.

  In the second phase, when the ERI (Middlebox) detects the first packets corresponding to a positioned filter, it completes this filter with the information (IPsource address, Portsource) presented by the received packets.

  A disadvantage of this method comes from the fact that it is likely to have malfunctions or risk of diversion of service if the first packets corresponding to the filter positioned by the ALG in the Middlebox are sent from another IP address than that used by the client installation to emit media streams.

  The object of the invention is to overcome the disadvantages of the prior art described above.

  DISCLOSURE OF THE INVENTION The invention recommends a method of filtering IP media stream packets exchanged between a source termination and a destination termination during a conversational session described by the Session Description Protocol (SDP). and signaled by the SIP (Session Initialization Protocol) log-in protocol comprising the following steps: constructing a parameterizable logical filter with information identifying the source termination and the destination termination involved in said session, - storing said logical filter, and during the initialization phase of said session, complete the filter stored by parameters exchanged by said terminations via the SIP signaling.

  The invention thus makes it possible to limit the access to the specific processes (example specific quality of service (QoS)) offered by a network only to the flows of IP packets exchanged between the endpoints of the conversational session SIP / SDP.

  Preferably, said filter is parameterized by data included in an SDP response sent by the destination end of the media stream to the source termination of said stream in response to an SDP offer sent by said source termination to said destination termination.

  In a preferred embodiment of the invention, the logical filter parameter data includes the IP address of the source of the stream packets, the destination IP address, the destination port and the transport protocol used during the transmission. initialization phase of the SIP session.

  According to the preferred embodiment, said logic filter is stored in an intermediate network element so as to block the transmission of the media stream between the source termination and the destination termination if said logical filter is not parameterized with the IP addresses of the network. source termination, the IP address of the destination termination, the destination port, and the transport protocol used.

  The invention also relates to a device for filtering IP media stream packets exchanged between a source termination and a destination termination during a conversational session described by the Session Description Protocol (SDP) session description protocol and reported by the Session Initialization Protocol (SIP). This device comprises: - means for constructing a parameterizable logic filter with information identifying the endpoints involved in said session, - an intermediate network element arranged between said source termination at said destination termination for storing said logical filter during the initialization phase of said session, means for completing the filter stored by parameters exchanged by said terminations via the SIP signaling.

BRIEF DESCRIPTION OF THE DRAWINGS

  Other features and advantages of the invention will emerge from the description which follows, taken by way of non-limiting example, with reference to the appended figures in which: - Figure 1 schematically illustrates the device and the construction steps of a logic filter for the source termination of an SDP offer according to the invention.

  FIG. 2 schematically illustrates the device and the steps for constructing a logical filter for the destination termination of an SDP offer according to the invention.

  DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS The following description relates to the implementation of the method according to the invention during a conversational session between a source termination 2 and a destination termination 4 for exchanging a media stream over the Internet network 6 during a videophone session for example.

  An intermediate server 8 designated by ALG for (Application Level Gateways in English), hosts a software application intended to examine and possibly modify the packets of the media stream exchanged between the source termination 2 and the destination termination 4.

  An intermediate network element ERI 10 (called Middlebox in English), also arranged between the source termination 2 and the destination termination 4, is intended to uniquely identify the IP packets constituting the media streams.

  The principle of the method according to the invention consists in constructing a filter containing the information (IPsource Address IPdestinationr POrtdestinationr Protocol Address) during each SDP offer / reply exchange during a SIP session.

  The IPsource address information is determined from the SDP response corresponding respectively to the offer 2865595 8 SDP to which the filter corresponds (IP address destination r Portdestinationr Protocol). This filter being positioned in the ERI 10 by the ALG 8. When the ALG 8 receives the first packets corresponding to the stored filter, it completes it with the Portsource indicated by the packets received.

  In the exemplary embodiment illustrated in FIG. 1, ICA will be referred to as the source termination 2 and ICB as the destination termination 4. In this case, the sending termination of the SDP offer is also receiving the corresponding SDP response.

  In step 12, ICA sends a SIP message containing an SDP offer. For each media stream n offered in the SDP offer, the ALG 8 calculates from the information in this offer a logical filter containing the information: (IPsource address = *, Portsource = *, IPdestinationAddress = @ IPICA r Portdestination = Port (ICA, Media n), Protocol = Protocol (ICA, Media n) In step 14, the ALG 8 transmits the received SIP message to ICB via the Internet 6.

  In step 16, ICB receives the SDP offer and prepares a corresponding SDP response.

  In step 18, ICB transmits to ICA a SIP message containing the SDP response to the offer issued by ICA.

  In step 20 the ALG 8 receives the SDP response for ICA and completes the filters calculated in step 12 with the receive address of the ICB media streams contained in the SDP response.

  at. the logical filters corresponding to the IP packets to be received by ICA are calculated as follows: (IPsource address = @ IPICB, Portsource = *, Address 2865595 9 IPdestination = @ IPICAr POrtdestination = POrt (ICAr Media n) r Protocol = Protocol (ICA , Media n)) b. The filters corresponding to the IP packets to be sent by ICA are calculated as follows: (IPsource address = @ IPICA, Portsource :, IP address = IPICBr POrtdestination = POrt (ICB, Media n), Protocol = Protocol (ICB, Media n) At step 22, the ALG 8 sets the filters calculated in step 20 in the ERI 10 and, in step 24, transmits the SDP response to ICA.

  Once the logical filters are completed, ICB starts transmitting the packets constituting the media streams indicated by the current SIP session (step 26), and when the ERI 10 receives the packets transmitted by ICB (step 28), it applies the filters going on these packages. Thus, as long as step 22 has not taken place, the packets are blocked, once step 22 has taken place the packets are sent to ICA (step 30).

  In step 32, ICA starts transmitting the packets constituting the media streams reported by the current SIP session. The ERI 10 receives the packets sent by ICA and applies the current filters to these packets. Thus, as long as step 22 did not take place, the packets are blocked, and once step 22 has taken place the packets are sent to ICB (step 34).

  In step 36, ICB receives the packets transmitted by ICA.

  Figure 2 illustrates the case of constructing the filters for the receiver of an SDP offer.

  In step 40, ICB sends a SIP message containing an SDP offer. For each media stream 2865595 10 offered in the SDP offer, the ALG 8 calculates from the information in this offer a logical filter containing the information: (IPsource address = *, Portsource = *, IPdestinationAddress = @ IPICB r Portdestination = Port (ICB, Media n), Protocol = Protocol (ICB, Media n)) In step 42, the ALG 8 transmits the received SIP message to ICA.

  In step 44, ICA sends a SIP message containing the SDP response to the offer issued by ICB. Upon receipt of this response, the ALG 8 supplements the filters calculated in step 42 with the reception address of the ICA media streams contained in the SDP response.

  at. the logical filters corresponding to the IP packets to be received by ICB are calculated as follows: (IPsource address = @ IPICA, Portsource = * r IP address destination = @ IPICBr Port of destination = POrt (ICBr Media) r Protocol = Protocol (ICB, Media n)) b. The filters corresponding to the IP packets to be transmitted by ICB are calculated as follows: - (IPsource address = @ IPICBr Portsource = *, IP addressdestination = @ IPICBr Portdestination = Port (ICB, Media n), Protocol = Protocol (ICA, Media n In step 46, the ALG 8 sets the filters calculated in step 42 in the ERI 10 and, in step 48, transmits the SDP response to ICB.

  Once the logical filters are completed, ICA starts transmitting the packets constituting the media streams reported by the current SIP session (step 50), and when the ERI 10 receives the packets transmitted by ICB, it applies the current filters to these packets. Thus, as long as step 46 has not taken place, the packets are blocked, and once step 46 has taken place, the packets are sent to ICB (step 30).

  In step 52, ICB starts transmitting the packets constituting the media streams reported by the current SIP session. The ERI 10 receives the packets transmitted by ICB and applies the current filters to these packets. Thus, as long as step 46 did not take place, the packets are blocked, and once step 46 has taken place the packets are sent to ICA (step 56).

Claims (5)

  A method of filtering IP media stream packets exchanged in a telecommunication network (6) between a source termination (2) and a destination termination (4) during a conversational session described by the SDP session description protocol (for Session Description Protocol) and signaled by the SIP (Session Initialization Protocol) log-in protocol, characterized in that it comprises the following steps: - constructing a logical filter parameterizable by information identifying the source termination ( 2) and the destination termination (4) involved in said session, storing said logical filter, - and during the initialization phase of said session, completing the stored filter by parameters exchanged by said terminations (2, 4) via SIP signaling.   2. Method according to claim 1, characterized in that said filter is parameterized by data included in an SDP response sent by the destination end (4) of the media stream to the source termination (2) of said stream in response to an SDP offer sent by said source termination (2) to said destination termination (4).   3. Method according to claim 2, characterized in that said logic filter is stored in an intermediate network element (10) so as to block the transmission of the media stream from the source termination (2) to the destination termination (4) if said logical filter is not set with the IP address of the source termination, the IP address of the destination termination, the destination port, and the transport protocol used 4. Method according to claim 3, characterized in that the parameterization data of the logical filter comprise the IP address of the source of the stream packets, the destination IP address, the destination port and the transport protocol used.   A device for filtering IP media stream packets exchanged between a source termination (2) and a destination termination (4) during a conversational session described by the Session Description Protocol (SDP) session description protocol and reported. by the session initiation protocol (SIP), a device characterized in that it comprises: means for constructing a parameterizable logical filter with information identifying the endpoints involved in said session; intermediate network (10) arranged between said source termination and said destination termination for storing said logical filter during the initialization phase of said session, - means for completing the stored filter by parameters exchanged by said terminations via the SIP signaling.