FR2861520A1 - METHOD OF MONITORING MESSAGES FOR INITIALIZING MULTIMEDIA FLOW EXCHANGE SESSIONS, SERVER AND INSTALLATION USING THE SAME - Google Patents

Abstract

The invention relates to a method for monitoring messages intended for the initialization of multimedia stream exchange sessions, these messages being transmitted in packet mode via a monitoring server by a network between a sending terminal and at least one receiving terminal, comprising a step during which one estimates (50) a throughput value for at least one initialization packet received by the monitoring server, a step during which one compares (52) this value with a maximum authorized throughput value and a step during which the transmission of the initialization packet is authorized (40) only if the rate value for this packet does not exceed the maximum authorized rate value. Optionally, the estimated rate value is an average value measured over a sliding time window. The invention also relates to a server and an installation implementing the method of the invention.

Description

The present invention relates to a message monitoring method

  intended for the initialization of multimedia stream exchange sessions, a server and an installation implementing this method.

  More specifically, the invention relates to a message monitoring method for initialization of multimedia stream exchange sessions transmitted in packet mode via a network monitoring server between a transmitting terminal and at least one receiving terminal.

  Initialization means establishing, modifying or closing a session during which multimedia streams are exchanged.

  Subsequently, we will describe the invention based on the SIP protocol. The invention is however not limited to this protocol alone.

  SIP (Session Initialization Protocol) is an application layer protocol of the OSI model allowing the establishment, modification or closure of a session during which multimedia streams are exchanged between a transmitting terminal and at the same time. least one receiving terminal.

  This SIP protocol uses messages that circulate as packets in a SIP network composed of specific processing servers. The SIP network is a network overlaying an IP network. The path taken by the SIP messages is therefore not necessarily the same as that borrowed by the multimedia streams.

  The establishment of the session is to define, through the exchange of SIP messages, the type and format of multimedia streams (eg codecs used) that terminals want to be transmitted. During the session, SIP messages can be exchanged between the terminals to agree on a new format of multimedia streams. Finally, SIP messages are exchanged again when closing the session.

  Generally, the operator of the network on which the multimedia streams are exchanged charges the user of the terminal having established the connection, according to the duration of the multimedia stream exchange session. If the terminal can not establish the connection despite the exchange of SIP messages, the operator does not charge the user of this terminal.

  However, it is possible for a malicious user to use the SIP messages themselves and the bandwidth allocated by the operator for their transmission, to include data not related to the establishment of a connection, including the multimedia data themselves. Indeed, the operator does not generally check the contents of SIP messages.

  The user can therefore finally exchange multimedia information on the network without the operator charging him this exchange.

  In order to overcome this drawback, methods used by the SIP processing servers which consist in limiting the transmission of SIP messages to messages containing only predefined information elements, adapted to the data, are already known in the state of the art. services that the network operator wishes to provide to its users.

  However, this method requires a significant processing capacity at the SIP processing servers that compare each SIP message to the messages authorized by the operator. It also requires an update of the SIP processing servers each time the operator decides to change the types of SIP messages allowed to transit on his network. This solution is effective but complex and expensive to implement.

  The aim of the invention is to overcome these drawbacks by providing a message monitoring method for initiating multimedia stream exchange sessions capable of verifying that the session initialization messages are not used to transmit messages. way of information, without checking the content of each initialization message transiting the network.

  For this purpose, the subject of the invention is a method of monitoring messages intended for the initialization of multimedia stream exchange sessions, these messages being transmitted in packet mode via a monitoring server via a network between a transmitting terminal and at least one receiving terminal, characterized in that it comprises the following steps: estimating a bit rate value for at least one initialization packet received by the monitoring server, this value is compared to a maximum authorized bit rate value , the initialization packet transmission is allowed only if the rate value for this initialization packet does not exceed the maximum allowed rate value.

  By monitoring the rate of SIP packets passing through the network, the invention makes it possible to detect diverted SIP packets which, containing information useless to the SIP protocol, abnormally increase their own throughput. The transmission of these SIP packets is then interrupted.

  A packet mode transmitted message monitoring method according to the invention may further include one or more of the following features: for each pair formed of a transmitting terminal and a receiving terminal, defining a transmission channel , associated with a specific maximum allowed throughput value; the estimation of the bit rate value for the initialization packet received by the monitoring server comprises a step during which the sizes of the last initialization packets transmitted by the transmitting terminal to the receiving terminal are stored in memory and received by the monitoring server for a predetermined time and a step in which the sum of the sizes of the initialization packets stored by the predetermined duration is divided; the method is implemented by the monitoring server, the latter being further dedicated to the processing of session initialization packets; constraining the forwarding of session initialization packets to the monitoring server as the first processing server traversed by these session initialization packets; the monitoring server being any of the session initialization packet processing servers, routing rules are defined that ensure a systematic transit of session initialization packets by this processing server; and the transmitted session initialization messages use the SI P protocol. The subject of the invention is also a message monitoring server intended for the initialization of multimedia stream exchange sessions, these messages being transmitted in packet mode via a monitoring server by a network between a transmitting terminal and at least one receiving terminal, characterized in that it comprises: means for estimating a bit rate value for at least one initialization packet received by the server of monitoring, means for comparing this value to a maximum allowed rate value, means for authorizing the transmission of the initialization packet only if the rate value for this packet does not exceed the maximum allowed rate value.

  The invention also relates to a message transmission installation intended for the initialization of multimedia stream exchange sessions comprising a network and at least one monitoring server according to the invention.

  The invention will be better understood on reading the following description, which is given purely by way of example and with reference to the accompanying drawings, in which: FIG. 1 is a diagram showing an installation for setting According to a method according to the invention, FIG. 2 is a block diagram showing the successive steps of a method according to the invention.

  FIG. 1 shows a transmitting terminal 10 communicating with a receiving terminal 12 via a data transmission network 18.

  The terminals 10 and 12 are for example computers or telephones, and the data transmission network 18 is an IP network 18 or a switched telephone network in combination with an IP network.

  The data transmission network 18 is constituted by a set of interconnected routers 14, 16 whose function is to ensure a correct routing of the messages between the terminals 10 and 12, through the data transmission network 18 .

  Terminals 10 and 12 exchange both initialization messages for the initialization of multimedia streaming sessions and multimedia streams. We will consider in the following description that the initialization messages are SIP messages.

  These SIP messages are transmitted in packet mode, that is, they are transmitted as a plurality of packets.

  The data transmission network 18 is also constituted by servers 20, 22 for processing specific SIP packets, interconnected in the form of a network 24 overlying the data transmission network 18. This network 24 overlay of the transmission network 18 is called SIP network 24 in the following description because it is dedicated to the transfer of SIP messages. The function of the SIP processing servers 20, 22 is to ensure the correct routing of the SIP packets between the terminals 10 and 12 through the SIP network 24.

  When two terminals 10 and 12 wish to establish a connection for the exchange of a multimedia stream 26, they exchange a SIP stream 28 to define the type and format of this multimedia stream 26.

  These two streams generally follow different network paths. The path followed by the multimedia streams 26 depends on the IP addresses of the computers 10, 12.

  It is determined by the IP routers 14, 16 of the network. The path followed by the SIP streams 28 may depend on the IP addresses of the computers 10, 12, but also the telephone numbers or e-mail addresses of the users of the computers 10, 12. It is determined by the SIP processing servers 20, 22 and necessarily passes through the SIP network 24.

  In the SIP network 24, the SIP streams 28 are transmitted on different SIP channels and are identifiable by means of the addresses of the computers 10, 12 between which the streams are transmitted, or addresses (for example the telephone numbers) of the users computers 10 and 12.

  The monitoring method according to the invention is implemented by a monitoring server through which the SIP packets pass. This monitoring server is generally also dedicated to processing SIP packets.

  The monitoring method according to the invention is therefore implemented by one of the SIP processing servers 20, 22, and consists in monitoring the SIP messages transmitted in packet mode by the network 18 between the transmitting terminal 10 and the receiving terminal 12.

  For a given SIP channel, it is estimated a Dm rate value for a SIP packet transmitted on this SIP channel and this rate value Dm is compared to a maximum allowed rate value Dmax. The transmission of the SIP packet is then allowed only if the rate value Dm for this SIP packet does not exceed the maximum allowed rate value Dmax.

  The maximum authorized bit rate Dmax for a given SIP channel is previously defined and communicated by the operator to the SIP monitoring servers 20, 22 which implement the monitoring method. The operator also communicates the maximum allowed size Tmax for a packet. This data is useful for SIP monitoring servers when a new SIP channel is created, and the servers have not received enough SIP packets to be able to calculate the Dm rate value of the new packet sent on the newly created SIP channel.

  The values of the maximum allowed bit rate Dmax and the maximum allowed size Tmax depend on the SIP message channel, ie the terminals exchanging the SIP messages. Some users may for example require a larger authorized maximum SIP rate, especially when they use encrypted data, the encryption increasing the number of data to be transmitted.

  All SIP processing servers on the network are not necessarily SIP monitoring servers. Also, it must be ensured that among all the processing servers through which a SIP packet passes, at least one of these SIP processing servers is a SIP monitoring server.

  For example, the invention can be implemented by a single SIP monitoring server as the first processing server traversed by the SIP packets. It is then possible to use in routers 14, 16 a software device such as a firewall, to force the routing of SIP packets to this first SIP processing server.

  Alternatively, the invention can be implemented by a SIP monitoring server which is any of the SIP processing servers of the SIP network. Routing rules are then defined to ensure a systematic transit of SIP packets by this SIP processing server.

  The monitoring method shown in FIG. 2 comprises a first step 30 of receiving a SIP packet by the SIP monitoring server 20, 22.

  In the next step 32, the SIP monitoring server 20, 22 identifies the SIP channel relating to the received packet. This identification is possible thanks to the addresses of the sender and receiver of the received SIP packet.

  In the next test step 34, the SIP monitoring server 20, 22 tests whether the received SIP packet is relative to a newly created SIP channel or to a SIP channel in use.

  If the SIP channel is newly created, we proceed to a step 36 of creation of a list named Last Packet List which keeps in memory for each SIP channel the size and the reception time of all the packets relating to this received SIP channel. since a duration D previously fixed by the operator. The Last Pack List list works like a sliding time window: information about the last received packet is inserted into the list while information about packets received longer than the D duration is taken out of the list. The first packets entered in the list are also the first ones.

  In the next test step 38, the SIP monitoring server checks whether the size T of the received packet is smaller than the maximum allowed size Tmax for a packet.

  If the size T of the received packet is smaller than the authorized size Tmax, a step 40 of transmission of the packet received by the SIP monitoring server is carried out.

  Otherwise, it proceeds to a test step 42 in which the monitoring server tests whether the received SIP packet corresponds to a SIP request or a SIP response.

  If the received packet corresponds to a request, it proceeds to a step 44 during which the SIP monitoring server 20, 22 does not transmit this request to the recipient but deletes it and sends an error response to the sender of the packet. .

  If the received packet corresponds to a response, step 46 is taken in which the SIP monitoring server does not transmit the response to the recipient and sends a cancellation message to the recipient.

  If in step 34 the monitoring server finds that the received packet corresponds to a SIP channel in use, it proceeds to a step 48 of updating the list Last Packets relating to the received packet's SIP channel. This update consists in adding to this list the information concerning the last received packet and in removing from this list the information concerning the packets received for longer than the duration D of storage.

  In the next step 50, the SIP monitoring server estimates the average rate Dm of packets relating to the SIP channel of the last packet received. This average rate is estimated by dividing the sum of the packet sizes stored in the Last Pack List list by the storage duration D.

  In the next test step 52, the SIP monitoring server checks whether the average rate Dm is lower than the maximum allowed rate Dmax.

  If the average flow Dm is less than the maximum allowed flow Dmax, go to step 40.

  If the average flow Dm is greater than the maximum authorized flow Dmax, go to step 42.

Claims (9)

  A method of monitoring messages for initiating multimedia stream exchange sessions, which messages are transmitted in packet mode via a monitoring server (20, 22) over a network (18) between a transmitting terminal (10). ) and at least one receiving terminal (12), characterized in that it comprises the following steps: it is estimated (50) a bit rate value for at least one initialization packet received by the monitoring server (20, 22) , comparing (52) this value to a maximum allowed rate value, authorizing (40) transmission of the initialization packet only if the rate value for that initialization packet does not exceed the maximum allowed rate value.   A method for monitoring packet-transmitted messages as claimed in claim 1, wherein for each formed pair of transmitting and receiving terminals a transmission channel is defined, associated with a specific maximum allowed bit rate. .   The packaged message monitoring method of claim 1 or 2, wherein estimating (50) the rate value for the initialization packet received by the monitoring server includes the following steps: in memory the sizes of the last initialization packets transmitted by the transmitting terminal (10) to the receiving terminal (12) and received by the server (20, 22) for monitoring for a predetermined duration, the sum of the sizes of the initialization packets stored by the predetermined duration.   4. Method of monitoring messages transmitted in packet mode according to one of claims 1 to 3, implemented by the monitoring server (20, 22), the latter being further dedicated to the processing of the initialization packets of sessions.   The message monitoring method according to claim 4, wherein the routing of the session initialization packets to the monitoring server (20, 22) is constrained as the first processing server traversed by these initialization packets. of sessions.   The message monitoring method according to claim 4, wherein the monitoring server (20, 22) is any of the session initialization packet processing servers, transit routing rules are defined. Systematic session initialization packets by this processing server.   The method of monitoring packet-transmitted messages according to any one of claims 1 to 6, wherein the transmitted session initialization messages use the SIP protocol.   A message monitoring server (20, 22) for initiating multimedia stream exchange sessions, which messages are transmitted in packet mode via a network monitoring server (18) between a transmitting terminal (10). ) and at least one receiving terminal (12), characterized in that it comprises: means (50) for estimating a bit rate value for at least one initialization packet received by the monitoring server (20, 22), means (52) for comparing this value with a maximum allowed rate value, means for authorizing (40) the transmission of the initialization packet only if the rate value for this packet does not exceed maximum flow rate allowed.   Message installation apparatus for initiating multimedia stream exchange sessions comprising a network (18), comprising at least one monitoring server (20, 22) according to claim 8.