EP2606623A1 - Establishing a packet stream having symmetrical quality of service by means of the negotiation of the quality indicator - Google Patents

Abstract

The invention relates to a method for establishing a packet stream with another apparatus through a communication network, comprising a step of determining a first value of a priority indicator according to the type of data stream, and a step of exchanging signaling messages with said other apparatus in order to enable the establishment of the data stream. The first value is inserted into the first of said signaling messages. Upon receiving a signaling message comprising a received value of said priority indicator, a transmitted value is determined from said received value and inserted into the packet stream.

Description

 Establishment of a packet flow with symmetrical quality of service by negotiation of the quality indicator

The present invention is reluctive to reseve multimedia communication. These networks can transmit traffic of different sizes (voice, video, data ...) corresponding to voried applications: telephony, videophony, internet noviggtion, file downloading, real-time textual discussion ("instant messaging" or "instant messaging"). chat ") ... This traffic is conventionally transmitted in the form of packet streams, in particular IP packet (for" Internet Protocol "). The same application message can be transmitted in several IP packets and it must be reconstructed on receipt before delivery to the application. These applications and these types of traffic are associated with different quality of service criteria and, since the transmission capacity of the networks is limited, there appears to be a need to give greater priority to certain applications / traffic pairs than to others. For example, in the case of a voice call, the delay taken by some packets may cause a loss of voice quality. In the worst case, the audio message may be inaudible or incomprehensible.

 In the case of browsing the internet, a delay in some packages may lead to the feeling of a slower system, but most of the time the effect is imperceptible.

It therefore seems natural to give greater importance to voice traffic compared to data traffic. There are technical solutions for assigning priorities to the different data streams transmitted by a network. One of these solutions is the DiffServ mechanism, as defined in particular in RFC 2474 of the I ETF, "Definition of the Differentiated Field Services (DS Field) in the IPv A and IPv6 Headers".

The principle of this DiffServ mechanism is to insert into the packets of a stream a field, DS Field, the value of which determines a class of service (or code-point). Network devices (routers, gateways, etc.) located on the path of the packet stream must read the DS Field and process retransmission of packets based on this value, with the highest class of service packets being the highest. priority.

In this way, flows requiring a high quality of service may be preferred by the communication network compared to flows that do not require.

However, there is no mechanism to specify how the class of service should be determined. Each device inserting a class of service into a packet stream determines the value according to its own mechanisms and according to the different flows that it may have to manage. These mechanisms may depend on the supplier of the equipment.

In bidirectional communication, it can often result in each of the two terminals (or associated access equipment) using different policies to determine the class of service. As a result, the flows of each direction belong to different classes of service and, therefore, the behavior of the communication network with respect to them is different and generate different perceived qualities of service for the two directions. For example, in the case of bidirectional voice communication, an equipment flow connected to an echo-sensitive network could require a decrease in the delay. If this is not applied, users may suffer from echo problems (the delay parameter amplifies the echo perception).

The object of the invention is to overcome this problem by providing a mechanism that guarantees the same perceived quality of service for all the directions of a communication session.

 To do this, the invention relates to a network equipment comprising means for establishing a packet flow with another equipment through a communication network, means for determining a first value of a priority indicator in depending on the type of this data flow and means for exchanging with this other equipment signaling messages to allow the establishment of the data flow. The equipment of the invention furthermore has means for inserting this first value in the first of the signaling messages and means for, on receipt of a signaling message (si, s2) comprising a value received from the indicator of priority, determining a value issued from the received value and inserting this value transmitted in the packets of the packet stream.

The invention also relates to a method for establishing a packet flow with another equipment through a communication network, comprising a step of determining a first value of a priority indicator based on the type of data flow and a step of exchange, with this other equipment, signaling messages to allow the establishment of data flow. The first value is inserted into the first of these signaling messages. AT receiving a signaling message having a value received from this priority indicator, a value transmitted is determined from this received value, and inserted into the packets of the packet stream.

According to one embodiment of the invention, the value emitted is the maximum value between the value received and the value determined by the equipment as a function of the type of packet flow.

 The priority indicator may be in accordance with the DiffServ mechanism and the equipment may then be adapted to insert the third value in the "DS Field" field of the packet stream.

 The value sent can be inserted into an SDP compliant attribute in the signaling messages.

 The value sent can be inserted into a "DS Field" field of packets of the packet stream.

The invention will become clearer in the following description with reference to the appended figure. This figure schematizes the messages exchanged between two devices connected by a communication network and implementing the invention.

The implementation of a session on a communication network, in particular on an "internet" type data network, generally comprises two phases: a phase of establishment, during which the parties to the session exchange signaling messages, and a phase of communication proper during which the parties exchange the data: voice, video, text ...

In the embodiment shown in FIG. 1, two pieces of equipment A and B are connected via a communication network N. However, the invention is quite capable of being applied with more parts, and so in the case of "conferences" audios or videos. Both devices can be communication terminals: fixed or mobile phones, computers, PDAs (Personal Digital Assistants PDAs) and so on.

 It can also be equipment hosted at a service provider, such as servers. For example, the communication may be a communication between a content server and a communication terminal allowing the user of the latter to access audio, video content ... It may also be virtual equipment.

In the example of Figure 1, it is assumed that the equipment A initiates the creation of the communication session. It sends equipment B a first signaling message, SI. This message may typically be a SIP compliant invitation message as defined in IETF RFC 3261, Session Invitation Protocol.

 This "Invite" message may be relayed by various devices, such as "SIP Proxy", within the communication network N. These are not shown in FIG. 1 and will not be described any more insofar as they do not influence the invention itself.

The equipment A has means for determining a value of a priority indicator p as a function of the type of the data stream that must compose the communication session. The type of data to be transmitted is called "type" here: video, audio, audio-video, text, real-time text of the "messaging" or "chat" type, etc. The type may furthermore be more accurate and it may be possible to decline a grosgrain type as "video" into several types.

The supplier of the equipment A generally sets a correspondence table between these types of data streams and a value of the priority indicator. This priority indicator is preferably in accordance with the DiffServ mechanism as specified by RFC 2474, "Definition of the Differentiated Field Service (DS Field) in the IPv4 and IPv6 Headers". The equipment A can be provided to directly have a correspondence table between type of data flow and "codepoint".

According to the invention, the equipment has means for inserting this value, v1, into the first signaling message S I, that is to say the invitation message. This value can be inserted into an appropriate SDP (Session Description Protocol) attribute as defined by RFC 4566 of the IET.

 This attribute can be 8-bit encoded. For example, it can be called "Traffic-class".

 According to the ABN F grammar (Augmented Backus-Naur Form), this attribute can be of the form:

 Traffic-class = "a = traffic-class:" Traffic-class-value

 Traffic-class-value = * DIGIT

 The value that can be taken by this attribute is an integer between 0 and 255.

In the example of the figure, an SDP attribute can be found in the message IF P "I nvite" IF of type: a = traffic-class: vl On receipt of the signaling message SI, the equipment B must read this received value vl of the priority indicator p.

I l refers to the transmitting equipment Has a signaling message S2 which, conventionally, is a message SI P "200 Ok". It also has means for inserting in this signaling message S2 an "emitted" value of the priority indicator p. This value sent is determined from the value received v1. According to one embodiment of the invention, this transmitted value (v3) is equal to the received value.

According to another embodiment of the invention, this value emitted is equal to the maximum between the received value v1 and a value determined by the type of data flow. Indeed, like the equipment A, it has means for determining a value v2 for the priority indicator p associated with the type of data flow. It can determine the type of data flow through other fields and attributes of the SI signaling message. In particular, the attribute "m" of the description of the medium, SDP, can be used to determine this value v2.

 The value inserted in the message S2 is therefore a value v3 = max (v1, v2).

 And the message S2 has an attribute a = traffic-class: v3 On receipt of this message S2, the equipment A can read this attribute and take note of this value v3.

 In some situations, the equipment A may return a signaling message according to S3. This may be a SIP "ACK" message.

It is not necessary to insert a priority indicator since at that time the two devices are already in place. However, the invention obviously applies to the case where this indicator is inserted in the possible other signaling messages S3. The devices A and B also have means for establishing the packet flow F through the communication network N, according to the modalities and parameters negotiated during the signaling messages (CODEC etc.).

They can insert within these packets the value of the previously determined priority indicator, i.e., this value v3.

 As discussed earlier, this value may be in accordance with DiffServ specifications. In particular, it may be 8-bit coded with a 6-bit DSCP field (Differeniiaied Services CodePoinf) as specified in paragraph 3 of RFC 2474 of the I ETF.

 Thus, the value of the priority indicator can be directly inserted into the field "DS Field" of the outgoing packets. The insertion into the DS field of the packets is carried out in a manner known per se. The way in which the inserted value is determined is, on the other hand, novel: according to the invention, an equipment according to the invention must therefore choose as the DiffServ indicator to use for a packet flow the value received in the last signaling message received concerning this value. flux.

In this way, the packet stream has the same DiffServ value in both directions. The transmission of the packets is therefore symmetrical and the quality of service perceived by the two equipments A and B is identical. Although the embodiments described above use the DiffServ mechanism, the invention is not limited to this mechanism but can instead be applied to any protocol that makes it possible to define a priority or a quality of service indicator at a specific location. packet of data.

Claims

 claims 1) Network equipment (A, B) having means for establishing a packet flow (F) with another equipment through a communication network (N), means for determining a first value (v1) of a priority indicator (p) according to the type of said data stream and means for exchanging with said other equipment signaling messages (si, s2, s3) to enable the establishment of said data stream, furthermore having means to insert said first value in the first (if) of said signaling messages and means for, upon receipt of a signaling message (si, s2) having a value received from said priority indicator, determining a value transmitted from said received value and inserting said transmitted value into the packets of said packet stream. 2) Network equipment according to claim 1, wherein said value transmitted is the maximum value between said received value and the value determined by said equipment as a function of said type of packet flow. 3) network equipment according to one of claims 1 or 2 wherein said priority indicator is consistent with the DiffServ mechanism, and adapted to insert said third value in the field "DS Field" said packet stream. 4) Network equipment according to one of the preceding claims, adapted to insert said value transmitted in an SDP-compliant attribute in said signaling messages. 5) network equipment according to one of the preceding claims, adapted to insert said value transmitted in a field "DS Field" packets of said packet stream. 6) Method for establishing a packet flow (F) with another piece of equipment through a communication network (N), comprising a step of determining a first value (v1) of an indicator of priority (p) according to the type of said data stream and an exchange step with said other signaling message equipment (si, s2, s3) for enabling the establishment of said data stream, wherein said first value is inserted in the first (if) of said signaling messages, and wherein, upon receipt of a signaling message (si, s2) having a value received from said priority flag, a value transmitted is determined from said received and inserted value in the packets of said packet stream. 7) Method according to the preceding claim, wherein said value emitted is the maximum value between said received value and the value determined by said equipment as a function of said type of packet flow. 8) Method according to one of claims 6 or 7 wherein said priority indicator is consistent with the DiffServ mechanism, and adapted to insert said third value in the field "DS Field" of said packet stream. 9) Method according to one of claims 5 to 8, wherein said transmitted value is inserted into an attribute conforming to the SDP protocol in said signaling messages. 10) Method according to one of claims 5 to 9, wherein said transmitted value is inserted into a field "DS Field" packets of said packet stream.