Abstract:
The present invention generally relates to a node and method for quality of service (QoS) control. The present invention particularly relates, but is not limited to, a technology that enables QoS control for a communication that is based on a protocol such as the Hypertext Transfer Protocol (HTTP), which does not mandate the use of a session description protocol (SDP) message.

Description:
TECHNICAL FIELD 
       [0001]    The present invention generally relates to a node and method for quality of service (QoS) control. The present invention particularly relates, but is not limited to, a technology that enables QoS control for a communication that is based on a protocol such as the Hypertext Transfer Protocol (HTTP), which does not mandate the use of a session description protocol (SDP) message. 
       BACKGROUND 
       [0002]    Currently, services such as voice over IP (VoIP) communication services and video streaming services are widespread. Because such services are delay-sensitive, it is important to provide adequate quality of service (QoS). 
         [0003]    WO 2007/045278 proposes a mechanism to ensure quality of service interoperability between two or more networks. According to WO 2007/045278, a media type described in an SDP message is mapped to a UPnP TrafficClass value, which corresponds to priority of communication traffic in a Universal Plug and Play (UPnP) network. 
         [0004]    However, because WO 2007/045278 relies on an SDP message, it is not possible to provide QoS for a communication that is based on a protocol such as HTTP, which does not mandate the use of an SDP message. 
         [0005]    Meanwhile, when a communication traverses two or more networks as described in WO 2007/045278, if priority for the communication set in one network is not consistent with priority for the communication set in another network, communication resource is likely wasted. For example, assume the case that high priority is set in a first network and low priority is set in a second network connected to the first network. In this case, the communication traffic will go through the first network with little delay, but it may be delayed in the second network. As a result, the communication resource of the first network, which is reserved in order to give high priority to the communication, will be wasted. 
         [0006]    However, there is no conventional art that enables consistent QoS control in a plurality of networks. 
       SUMMARY 
       [0007]    The present invention is intended to address the above-described problem, and it is a feature thereof to introduce a technology that enables QoS control for a communication that is based on a protocol such as HTTP, which does not mandate the use of an SDP message. 
         [0008]    Another feature of the present invention is to enable consistent QoS control in a plurality of networks. 
         [0009]    According to the first aspect of the present invention, there is provided a control node for use in an environment where a network includes a decision node for deciding a quality of service (QoS) parameter, and a first communication device and a second communication device are connected to the network, comprising: 
         [0010]    a request receiving unit for receiving a QoS request for providing QoS for a communication session between the first communication device and the second communication device, the QoS request including session-related information from which QoS required for the communication session is derived; 
         [0011]    a requesting unit for requesting the decision node to decide a QoS parameter for enforcing QoS for the communication session based on the session-related information; 
         [0012]    a parameter receiving unit for receiving a QoS parameter for the network decided by the decision node, for enforcing QoS for the communication session in the network; and 
         [0013]    a sending unit for sending a result of the decision of the QoS parameter for the network to the second communication device. 
         [0014]    According to the second aspect of the present invention, there is provided a control node for use in an environment where a first network is connected to a second network via a gateway node, the first network includes a first communication device, the second network includes a decision node for deciding a quality of service (QoS) parameter, and a second communication device is connected to the second network, comprising: 
         [0015]    a request receiving unit for receiving a QoS request for providing QoS for a communication session between the first communication device and the second communication device, the QoS request including session-related information from which QoS required for the communication session is derived; 
         [0016]    a requesting unit for requesting the decision node to decide a QoS parameter for enforcing QoS for the communication session based on the session-related information; 
         [0017]    a parameter receiving unit for receiving a QoS parameter for the second network decided by the decision node, for enforcing QoS for the communication session in the second network; and 
         [0018]    a sending unit for sending a result of the decision of the QoS parameter for the second network to the second communication device. 
         [0019]    According to the third aspect of the present invention, there is provided a decision node for deciding a quality of service (QoS) parameter in an environment where a first network is connected to a second network via a gateway node, the first network includes a first communication device and a first QoS enforcement node for enforcing QoS in the first network, the second network includes a second QoS enforcement node for enforcing QoS in the second network, and a second communication device is connected to the second network, comprising: 
         [0020]    a receiving unit for receiving a request for deciding a QoS parameter for a communication session between the first communication device and the second communication device, the request including session-related information from which QoS required for the communication session is derived; 
         [0021]    an obtaining unit for obtaining, from a control node which communicates with the gateway node, first network-related information from which highest QoS enforceable for the communication session in the first network is derived, and for obtaining, from the second QoS enforcement node, second network-related information from which highest QoS enforceable for the communication session in the second network is derived; 
         [0022]    a deciding unit for deciding a first QoS parameter for enforcing QoS for the communication session in the first network and a second QoS parameter for enforcing QoS for the communication session in the second network based on the session-related information, the first network-related information, and the second network-related information; and 
         [0023]    a sending unit for sending the first QoS parameter to the first QoS enforcement node, and for sending the second QoS parameter to the second QoS enforcement node. 
         [0024]    According to the fourth aspect of the present invention, there is provided a method for controlling a control node for use in an environment where a network includes a decision node for deciding a quality of service (QoS) parameter, and a first communication device and a second communication device are connected to the network, comprising: 
         [0025]    a request receiving step of receiving a QoS request for providing QoS for a communication session between the first communication device and the second communication device, the QoS request including session-related information from which QoS required for the communication session is derived; 
         [0026]    a requesting step of requesting the decision node to decide a QoS parameter for enforcing QoS for the communication session based on the session-related information; 
         [0027]    a parameter receiving step of receiving a QoS parameter for the network decided by the decision node, for enforcing QoS for the communication session in the network; and 
         [0028]    a sending step of sending the QoS parameter for the network to the second communication device. 
         [0029]    According to the fifth aspect of the present invention, there is provided a method for controlling a control node for use in an environment where a first network is connected to a second network via a gateway node, the first network includes a first communication device, the second network includes a decision node for deciding a quality of service (QoS) parameter, and a second communication device is connected to the second network, comprising: 
         [0030]    a request receiving step of receiving a QoS request for providing QoS for a communication session between the first communication device and the second communication device, the QoS request including session-related information from which QoS required for the communication session is derived; 
         [0031]    a requesting step of requesting the decision node to decide a QoS parameter for enforcing QoS for the communication session based on the session-related information; 
         [0032]    a parameter receiving step of receiving a QoS parameter for the second network decided by the decision node, for enforcing QoS for the communication session in the second network; and 
         [0033]    a sending step of sending the QoS parameter for the second network to the second communication device. 
         [0034]    According to the sixth aspect of the present invention, there is provided a method for controlling a decision node for deciding a quality of service (QoS) parameter in an environment where a first network is connected to a second network via a gateway node, the first network includes a first communication device and a first QoS enforcement node for enforcing QoS in the first network, the second network includes a second QoS enforcement node for enforcing QoS in the second network, and a second communication device is connected to the second network, comprising: 
         [0035]    a receiving step of receiving a request for deciding a QoS parameter for a communication session between the first communication device and the second communication device, the request including session-related information from which QoS required for the communication session is derived; 
         [0036]    an obtaining step of obtaining, from a control node which communicates with the gateway node, first network-related information from which highest QoS enforceable for the communication session in the first network is derived, and for obtaining, from the second QoS enforcement node, second network-related information from which highest QoS enforceable for the communication session in the second network is derived; 
         [0037]    a deciding step of deciding a first QoS parameter for enforcing QoS for the communication session in the first network and a second QoS parameter for enforcing QoS for the communication session in the second network based on the session-related information, the first network-related information, and the second network-related information; and 
         [0038]    a sending step of sending the first QoS parameter to the first QoS enforcement node, and for sending the second QoS parameter to the second QoS enforcement node. 
         [0039]    The main advantage of the present invention is that QoS control is enabled for a communication that is based on a protocol such as HTTP, which does not mandate the use of an SDP message. 
         [0040]    Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0041]      FIG. 1  illustrates an overview of a communication system  100  according to the first embodiment; 
           [0042]      FIG. 2  is a functional block diagram of an application server (AS)  111  according to the first and second embodiments; 
           [0043]      FIG. 3  is a sequence diagram illustrating a procedure for providing QoS for a communication session between a user equipment (UE)  120  and a service providing server (SPS)  130  according to the first embodiment; 
           [0044]      FIG. 4  is a sequence diagram illustrating a procedure for providing QoS for a communication session between the UE  120  and the SPS  130  according to an alternative scenario of the first embodiment; 
           [0045]      FIG. 5  illustrates an overview of a communication system  500  according to the second embodiment; 
           [0046]      FIG. 6  is a functional block diagram of a policy decision function (PDF)  530  according to the second embodiment; 
           [0047]      FIG. 7  is a sequence diagram illustrating a procedure for providing QoS for a communication session between the UE  120  and the SPS  130  according to the second embodiment; and 
           [0048]      FIG. 8  is a sequence diagram illustrating a procedure for providing QoS for a communication session between the UE  120  and the SPS  130  according to an alternative scenario of the second embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0049]    Embodiments of the present invention will now be described with reference to the attached drawings. Each embodiment described below will be helpful in understanding a variety of concepts from the generic to the more specific. 
         [0050]    It should be noted that the technical scope of the present invention is defined by the claims, and is not limited by each embodiment described below. In addition, not all combinations of the features described in the embodiments are always indispensable for the present invention. 
       First Embodiment 
       [0051]      FIG. 1  illustrates an overview of a communication system  100  according to the first embodiment. The communication system  100  includes a wide area network (WAN)  110 , which may be, for example, the Internet. A user equipment (UE)  120 , which acts as a first communication device, and a service providing server (SPS)  130 , which acts as a second communication device, are connected to the WAN  110 . The UE  120  and the SPS  130  may communicate with each other via the WAN  110 . 
         [0052]    The WAN  110  includes an application server (AS)  111 , a policy decision function (PDF)  112 , and a policy enforcement function (PEF)  113 . The AS  111  is configured to periodically obtain device-related information of the UE  120 , which represents, for example, capability and presence status of the UE  120 . In some scenarios, the AS  111  is also configured to act as a proxy server that mediates the communication between the UE  120  and the SPS  130 . 
         [0053]    The PDF  112  is a functional entity that determines and authorizes policies, including a QoS policy, for a user. The PDF  112  is configured to decide QoS parameters for enforcing the QoS policy. The PDF  112  may be Policy and Charging Rule Function (PCRF) as defined in 3GPP Policy and Charging Control Architecture (PCC) (3GPP TS 23.203), Resource and Admission Control Subsystem (RACS) as defined in ETSI TISPAN (ETSI ES 282 003), or Policy Decision Point (PDP) as defined in IETF (IETF 2753). 
         [0054]    The PEF  113  is a functional entity that enforces the QoS policy, based on the QoS parameters decided by the PDF  112 . The PEF  113  may also enforce the other policies determined by the PDF  112 . To be exact, the PEF  113  is implemented in respective nodes (such as access routers) that are located in the data transmission path between the UE  120  and the SPS  130 , but such nodes are not shown in  FIG. 1  for the sake of simplicity. 
         [0055]    It should be noted that although the specific terms such as SPS are used in the description, the present invention is not limited thereto. For example, a cellular phone may be employed instead of the SPS  130 . 
         [0056]      FIG. 2  is a functional block diagram of the AS  111  according to the first embodiment. It should be noted that the functionality of each block in the AS  111  may be implemented using dedicated hardware, using software executed by a processor (not shown) or a combination thereof. 
         [0057]    The AS  111  comprises a request receiving unit  201 , which receives a QoS request for providing QoS for a communication session between the UE  120  and the SPS  130 . The request receiving unit  201  may receive the QoS request from the SPS  130 . In some scenarios, the request receiving unit  201  is also configured to act as a proxy server that mediates communication between the UE  120  and the SPS  130 . In this case, the request receiving unit  201  receives the QoS request from the UE  120  instead of the SPS  130 . The operations of the other blocks in the AS  111  will be described later with reference to the sequence diagrams of  FIGS. 3 and 4 . 
         [0058]      FIG. 3  is a sequence diagram illustrating a procedure for providing QoS for a communication session between the UE  120  and the SPS  130  according to the first embodiment. For the sake of simplicity, operations that are not necessary to describe the present embodiment are omitted in the following sequence diagrams. It should be noted that the present invention is not limited to the protocols described below. For example, the HTTP GET request described below may be replaced by a SIP INVITE message. 
         [0059]    In step S 301 , the UE  120  sends device-related information of the UE  120  to the AS  111  by means of, for example, an HTTP POST request. The device-related information is received by the obtaining unit  202  of the AS  111 . The device-related information represents, for example, capability and presence status of the UE  120 , and examples of the capability includes the highest bit rate that the UE  120  can handle. The operation of step S 301  is periodically performed while the UE  120  is attached to the WAN  110 . 
         [0060]    In step S 302 , the UE  120  sends an HTTP GET request to the SPS  130  for establishing a communication session between the UE  120  and the SPS  130 . The HTTP GET request may include a service ID, which identifies a service to be received from the SPS  130 , a user ID, which identifies a user of the UE  120 , and a QoS request for providing QoS for the communication session. The QoS request includes session-related information from which the QoS (e.g., bandwidth, priority, etc.) required for the communication session is derived. It should be noted that the IP packets that send the HTTP GET request include session identification information (e.g., IP addresses and port numbers of the UE  120  and SPS  130 , and protocol type to be used) that identifies the communication session. 
         [0061]    In step S 303 , the SPS  130  analyzes the QoS request and determines whether or not the SPS  130  supports the required QoS. If the SPS  130  does not support the required QoS, it modifies the QoS request such that the session-related information indicates the QoS supported by the SPS  130  as the QoS required for the communication session. 
         [0062]    In step S 304 , the SPS  130  sends the QoS request and the session identification information to the AS  111 . The QoS request is received by the request receiving unit  201  of the AS  111 . The SPS  130  may also send the user ID to the AS  111 . 
         [0063]    In step S 305 , the requesting unit  203  of the AS  111  analyzes the QoS request and requests the PDF  112  to decide QoS parameters for enforcing QoS based on the QoS request (in particular, based on the session-related information which indicates the required QoS). In this step, the requesting unit  203  also sends the session identification information to the PDF  112 . In addition, the requesting unit  203  may send the device-related information to the PDF  112  and ask the PDF  112  to decide the QoS parameters further based on the device-related information. Moreover, in the case that the request receiving unit  201  has received the user ID in step S 304 , the requesting unit  203  may retrieve preferences regarding QoS, which are associated with the user ID of the user of the UE  120 , send the preferences to the PDF  112 , and ask the PDF  112  to decide the QoS parameters further based on the preferences. 
         [0064]    In step S 306 , the PDF  112  decides QoS parameters to be used by the PEF  113  for enforcing the required QoS in the WAN  110 . In this step, the PDF  112  may retrieve the current congestion status in the WAN  110  and decide the QoS parameters based on the current congestion status. In the case that the PDF  112  has received the device-related information in step S 305 , the PDF  112  may decide the QoS parameters such that they do not exceed the capability of the UE  120 . Moreover, in the case that the PDF  112  has received the preferences of the user in step S 305 , the PDF  112  may decide the QoS parameters according to the preferences. 
         [0065]    In step S 307 , the PDF  112  sends the decided QoS parameters and the session identification information to the PEF  113 . 
         [0066]    In step S 308 , the PEF  113  enables QoS, using the QoS parameters received in step S 307 , for the communication session identified by the session identification information. 
         [0067]    In step S 309 , the PEF  113  returns a response to the PDF  112  to notify that QoS was successfully enabled. 
         [0068]    In step S 310 , the PDF  112  sends the QoS parameters decided in step S 306  to the AS  111 . The QoS parameters are received by the parameter receiving unit  204  of the AS  111 . 
         [0069]    In step S 311 , the sending unit  205  of the AS  111  sends a result of the decision of the QoS parameters to the SPS  130 . For example the result represents “success” or “failure” of the decision based on the QoS request sent in step S 304 . Alternatively, the sending unit  205  may sends the decided QoS parameters to the SPS  130  as the result of the decision. In the latter case, if the QoS based on the QoS parameters is lower than a given threshold, the instructing unit  206  of the AS  111  may instruct the SPS  130  to change the protocol of the service identified in step S 302  to a less delay-sensitive protocol. For example, assume the case that a video streaming service that uses RTP/UDP/IP packets for real time media transport and a bit rate of 1 Mbps at minimum is requested in step S 302 , but the available bit rate is only 500 Kbps. In this case, the instructing unit  206  may instruct the SPS  130  to send the video data regarding the requested video streaming service as a single file to the UE  120  by means of, for example, File Transfer Protocol (FTP). 
         [0070]    In step S 312 , the SPS  130  establishes a communication session with the UE  120 , and enables QoS for the communication session in the SPS  130  based on the QoS parameters received in step S 311 . 
         [0071]    In step S 313 , the SPS  130  sends data regarding the service requested in step S 302  to the UE  120  via the PEF  113  of the WAN  110 . Because the data is relayed by the PEF  113 , which has enabled QoS in step S 308 , the UE  120  can receive the data in a manner whereby the given QoS is ensured. 
         [0072]    In an alternative scenario, the AS  111  may act as a proxy server. Specifically, the request receiving unit  201  of the AS  111  acts as a proxy server that mediates the communication between the UE  120  and the SPS  130 . 
         [0073]      FIG. 4  is a sequence diagram illustrating a procedure for providing QoS for a communication session between the UE  120  and the SPS  130  according to the alternative scenario of the first embodiment. For the sake of simplicity, explanations regarding the use of service IDs, user IDs, preferences, and so on will be omitted, but they can be used in a manner similar to the case of  FIG. 3 . Moreover, the session identification information is transferred in a manner similar to the case of  FIG. 3 . 
         [0074]    In step S 401 , the UE  120  sends an HTTP GET request to the request receiving unit  201  of the AS  111  for establishing a communication session between the UE  120  and the SPS  130 . 
         [0075]    In step S 402 , the requesting unit  203  of the AS  111  analyzes the QoS request and determines whether or not the AS  111 , which acts as the proxy server, supports the required QoS. If the AS  111  does not support the required QoS, the requesting unit  203  modifies the QoS request such that the session-related information indicates the QoS supported by the AS  111  as the QoS required for the communication session. 
         [0076]    In step S 403 , the requesting unit  203  of the AS  111  requests the PDF  112  to decide QoS parameters for enforcing QoS based on the QoS request (in particular, based on the session-related information which indicates the required QoS). In this alternative scenario, the requesting unit  203  may request the PDF  112  to decide QoS parameters to be used by the enforcing unit  207  in addition to QoS parameters to be used by the PEF  113 . 
         [0077]    In step S 404 , the PDF  112  decides the QoS parameters to be used by the PEF  113  for enforcing the required QoS in the WAN  110 . Moreover, the PDF  112  may decide the QoS parameters to be used by the enforcing unit  207  of the AS  111  for enforcing the required QoS in the request receiving unit  201 , which acts as the proxy server. In this step, the PDF  112  may retrieve the current congestion status in the WAN  110  and decide the QoS parameters based on the current congestion status. 
         [0078]    In step S 405 , the PDF  112  sends the QoS parameters for the PEF  113  and the QoS parameters for the enforcing unit  207  decided in step S 404  to the AS  111 . The QoS parameters are received by the parameter receiving unit  204  of the AS  111 . 
         [0079]    In step S 406 , the enforcing unit  207  of the AS  111  enables QoS, using the QoS parameters for the enforcing unit  207  received in step S 405 , for the communication session in the request receiving unit  201  identified by the session identification information. 
         [0080]    In step S 407 , the sending unit  205  of the AS  111  sends the QoS parameters (both for the PEF  113  and the enforcing unit  207 ) to the SPS  130 . Moreover, the sending unit  205  sends the service ID received in step S 401  in order to request the SPS  130  for establishing the communication session between the UE  120  and the SPS  130 . In this step, the instructing unit  206  of the AS  111  may instruct the SPS  130  to change the protocol in a manner similar to the case of step S 311  of  FIG. 3 . 
         [0081]    In step S 408 , the SPS  130  may invoke the process of re-negotiating and modifying QoS by sending a QoS updating request to the request receiving unit  201  of the AS  111 . This operation is performed in the case that, for example, the SPS  130  cannot satisfy the QoS based on the QoS parameters received in step S 407 . 
         [0082]    In step S 409 , the SPS  130  sends data regarding the service requested in step S 407  to the UE  120  via the request receiving unit  201  of the AS  111  in addition to the PEF  113  of the WAN  110 . Because the data is relayed by the request receiving unit  201  and the PEF  113 , which have enabled QoS in step S 406  and step S 308 , the UE  120  can receive the data in a manner whereby the given QoS is ensured. 
         [0083]    In  FIG. 4 , it is assumed that the data regarding the service requested by the UE  120  is sent from the SPS  130  to the UE  120  via the AS  111  as described in step S 409 . However, the SPS  130  may send the data to the UE  120  without going through the AS  111 . In this case, enabling QoS in step S 406  and the related operation can be omitted. 
         [0084]    As described above, because the AS  111  handles the QoS request received from the UE  120  or the SPS  130 , QoS control is enabled for communications that are based on a protocol such as HTTP, which does not mandate the use of an SDP message. 
       Second Embodiment 
       [0085]    The concept of the present invention can also be applied to the case where the UE  120  is included in a network that is different from the WAN  110 . 
         [0086]      FIG. 5  illustrates an overview of a communication system  500  according to the second embodiment. The communication system  500  includes a home network  510  (also referred to as a first network) and a wide area network (WAN)  110  (also referred to as a second network). The home network  510  is an IP network and is connected to the WAN  110  via a gateway (GW)  520 . The GW  520  includes a PEF for enforcing QoS in the home network  510 . The WAN  110  may comprise the PDF  112 , as is the case for the first embodiment. However, in the case that the WAN  110  comprises a PDF  530  as shown in  FIG. 5 , which will be described in detail later with reference to  FIGS. 6-8 , the PDF  530  enables consistent QoS control in the home network  510  and the WAN  110 . 
         [0087]      FIG. 6  is a functional block diagram of a policy decision function (PDF)  530  according to the second embodiment. It should be noted that the functionality of each block in the PDF  530  may be implemented using dedicated hardware, using software executed by a processor (not shown) or a combination thereof. The operations of each block in the PDF  530  will be described later with reference to the sequence diagrams of  FIGS. 7 and 8 . 
         [0088]      FIG. 7  is a sequence diagram illustrating a procedure for providing QoS for a communication session between the UE  120  and the SPS  130  according to the second embodiment. For the sake of simplicity, explanations regarding the use of service IDs, user IDs, preferences, and so on will be omitted, but they can be used in a manner similar to the case of  FIG. 3 . Moreover, the session identification information is transferred in a manner similar to the case of  FIG. 3 . 
         [0089]    In step S 701 , the GW  520  collects network-related information of the home network  510 . The network-related information includes, for example, the number of the on-going sessions and available bandwidth in the home network  510 . In other words, the network-related information is information from which highest QoS enforceable for the communication session in the home network  510  can be derived. The GW  520  also collects the device-related information of the UE  120 . Then, the GW  520  sends the device-related information and the network-related information to the AS  111  by means of, for example, an HTTP POST request. The operation of step S 701  is periodically performed while the GW  520  is attached to the WAN  110 . 
         [0090]    In step S 702 , the UE  120  sends an HTTP GET request to the SPS  130  via the GW  520  for establishing a communication session between the UE  120  and the SPS  130 . 
         [0091]    In step S 703 , the receiving unit  601  of the PDF  530  receives a request for deciding the QoS parameters for the communication session. The request includes the session-related information. 
         [0092]    In step S 704 , the obtaining unit  602  of the PDF  530  obtains the network-related information of the home network  510  from the AS  111 . The obtaining unit  602  also obtains the network-related information of the WAN  110  from the PEF  113 . The network-related information of the WAN  110  is, as with the network-related information of the home network  510 , information from which the highest QoS enforceable for the communication session in the WAN  110  can be derived. 
         [0093]    In step S 705 , the deciding unit  603  of the PDF  530  decides QoS parameters to be used by the PEF  113  for enforcing the required QoS in the WAN  110 . The deciding unit  603  also decides QoS parameters to be used by the PEF of the GW  520  for enforcing the required QoS in the home network  510 . In this step, the deciding unit  603  makes the decision of the QoS parameters based on the network-related information of the home network  510  and the network-related information of the WAN  110  in addition to the session-related information which indicates the required QoS, such that the QoS for the home network  510  is consistent (or aligned) with the QoS for the WAN  110 . For example, assume a case wherein the session-related information indicates that the communication session requires 5 Mbps at minimum and requires 10 Mbps if possible, the network-related information of the home network  510  indicates that the highest bit rate available in the home network  510  is 10 Mbps, and the network-related information of the WAN  110  indicates that the highest bit rate available in the WAN is 6 Mbps. In this case, the deciding unit  603  decides the QoS parameters for the home network  510  and for the WAN  110  so that 6 Mbps is reserved for the communication session both in the home network  510  and the WAN  110 . In this way, wasting of communication resources for a given network can be avoided (as compared with the case where 10 Mbps is reserved for the home network  510  and (10−6) =4 Mbps is wasted therein). In this step, the deciding unit  603  may make a decision of the QoS parameters further based on the device-related information of the UE  120 . 
         [0094]    In step S 706 , the sending unit  604  of the PDF  530  sends the QoS parameters for the WAN  110  to the AS  111 . The sending unit  604  also sends the QoS parameters for the home network  510  and the session identification information to the AS  111 . 
         [0095]    In step S 707 , the AS  111  sends the QoS parameters for the home network  510  and the session identification information to the GW  520 . Alternatively, the sending unit  604  may send the QoS parameters for the home network  510  and the session identification information directly to the GW  520  in step S 706 . 
         [0096]    In step S 708 , the PEF of the GW  520  enables QoS, using the QoS parameters received in step S 708 , for the communication session identified by the session identification information. 
         [0097]    In step S 709 , the GW  520  returns a response to the AS  111  to notify that QoS was successfully enabled in the home network  510 . 
         [0098]    In step S 710 , the SPS  130  sends data regarding the service requested in step S 702  to the UE  120  via the PEF  113  of the WAN  110  and the GW  520 . Because the data is relayed by the PEF  113  and the GW  520 , which have enabled QoS in step S 308  and step S 708 , the UE  120  can receive the data in a manner whereby the given QoS is ensured. 
         [0099]    In an alternative scenario, the AS  111  may act as a proxy server. Specifically, the request receiving unit  201  of the AS  111  acts as a proxy server that mediates communication between the UE  120  and the SPS  130 . 
         [0100]      FIG. 8  is a sequence diagram illustrating a procedure for providing QoS for a communication session between the UE  120  and the SPS  130  according to the alternative scenario of the second embodiment. For the sake of simplicity, explanations regarding the use of service IDs, user IDs, preferences, and so on will be omitted, but they can be used in a manner similar to the case of  FIG. 3 . Moreover, the session identification information is transferred in a manner similar to the case of  FIG. 3 . 
         [0101]    In step S 801 , the UE  120  sends an HTTP GET request to the request receiving unit  201  of the AS  111  via the GW  520  for establishing a communication session between the UE  120  and the SPS  130 . 
         [0102]    In step S 802 , the requesting unit  203  of the AS  111  requests the PDF  530  to decide QoS parameters for enforcing QoS based on the QoS request (in particular, based on the session-related information which indicates the required QoS). In this alternative scenario, the requesting unit  203  may request the PDF  530  to decide QoS parameters to be used by the enforcing unit  207  in addition to QoS parameters to be used by the PEF  113 . The QoS request is received by the receiving unit  601  of the PDF  530 . 
         [0103]    In step S 803 , the deciding unit  603  of the PDF  530  decides the QoS parameters to be used by the PEF  113  for enforcing the required QoS in the WAN  110 . The deciding unit  603  also decides the QoS parameters to be used by the PEF of the GW  520  for enforcing the required QoS in the home network  510 . Moreover, the PDF  112  may decide the QoS parameters to be used by the enforcing unit  207  of the AS  111  for enforcing the required QoS in the request receiving unit  201 , which acts as the proxy server. In this step, the deciding unit  603  makes the decision such that the QoS parameters for the home network  510 , the QoS parameters for the PEF  113 , and the QoS parameter for the enforcing unit  207  of the AS  111  are consistent with each other in order to avoid a waste of communication resources. 
         [0104]    In step S 804 , the sending unit  604  of the PDF  530  sends the QoS parameters for the home network  510 , the QoS parameters for the PEF  113 , and the QoS parameters for the enforcing unit  207  decided in step S 803  to the AS  111 . 
         [0105]    In step S 805 , the SPS  130  may invoke the process of re-negotiating and modifying QoS by sending a QoS updating request to the request receiving unit  201  of the AS  111 . This operation is performed in the case that, for example, the SPS  130  cannot satisfy the QoS based on the QoS parameters received in step S 407 . 
         [0106]    In step S 806 , the SPS  130  sends data regarding the service requested in step S 407  to the UE  120  via the request receiving unit  201  of the AS  111  in addition to the PEF  113  of the WAN  110  and the GW  520 . Because the data is relayed by the request receiving unit  201 , the PEF  113 , and the GW  520  which have enabled QoS in step S 406 , step S 308 , and step S 708 , the UE  120  can receive the data in a manner whereby the given QoS is ensured. 
         [0107]    In  FIG. 8 , it is assumed that the data regarding the service requested by the UE  120  is sent from the SPS  130  to the UE  120  via the AS  111  as described in step S 409 . However, the SPS  130  may send the data to the UE  120  without going through the AS  111 . In this case, enabling QoS in step S 406  and the related operation can be omitted. 
         [0108]    As described above, because the AS  111  handles the QoS request received from the UE  120  or the SPS  130 , QoS control is enabled for communications based on a protocol such as HTTP, which does not mandate the use of an SDP message. 
         [0109]    Moreover, because the PDF  530  decides the QoS parameters for the home network  510  and the WAN  110  in a centralized manner, consistent QoS control may be enabled in a plurality of networks. 
         [0110]    (Variations) 
         [0111]    As shown in  FIG. 7 , the AS  111  has the function of collecting the network-related information of the home network  510 . However, this function can be separated from the AS  111 . In this case, the PDF  530  may obtain the network-related information of the home network  510  from, for example, a presence server managing the home network  510 . 
         [0112]    The concept of the present invention can be applied to cases where the UE  120  sends and receives the application level session control messages without using the GW  520  as a proxy. In this case, the QoS parameters for the home network  510  can be transferred from the PDF  530  to the UE  120  without going through the GW  520 . 
         [0113]    The concept of the present invention can be applied to cases where the request for establishing the communication session between the UE  120  and the SPS  130  is initiated by a third party device. However, it is not necessary for the third party device to be included in the home network  510 . 
         [0114]    The AS  111  can provide the PDF  530  with the address information of the GW  520  so that the PDF  530  can send the QoS parameters for the home network  510  to the GW  520  directly (i.e., without going through the AS  111 . 
         [0115]    While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.