Abstract:
The present invention relates to a method and arrangements in a mobile telecommunications network including a plurality of access points ( 203 ), a plurality of 5 network gateway devices ( 204 ). The method comprising the steps of: deciding a security setting needed for a dedicated bearer signal by a network component, communicating said decision to a node needed for establishing communication, configuring or selecting by said access point ( 203 ) a secure protocol ( 205 ) as needed between said access point and said gateway devices ( 204 ), and said decision being based on one or several of the network deployment being used and/or network operator policies.

Description:
TECHNICAL FIELD 
       [0001]    The present invention generally relates to a security method in a communications network between at least two nodes. More specifically the invention relates to deciding security settings when establishing a bearer for a session and ensuring that the initially decided security settings are maintained when the bearer is moved to other nodes. 
       BACKGROUND 
       [0002]    The LTE (Long Term Evolution) and SAE (System Architecture Evolution) architecture is currently being specified by 3GPP, e.g. for inclusion in 3GPP Release-8.  FIGS. 1   a  and  1   b  show conventional architectures so far agreed as part of the SAE/LTE standardization work in 3GPP, e.g. as described in 3GPP TS 23.401 for the non-roaming scenarios.  FIG. 1   a  shows Non-roaming architecture for 3GPP accesses and  FIG. 1   b  shows non-roaming architecture for 3GPP accesses in a single gateway option. 
         [0003]    Transport Network level security in the S1 interface (i.e. both the S1-MME and S1-U interfaces) is needed in many deployment scenarios between Evolved UTRAN (E-UTRAN), comprising a single node type called E-UTRAN NodeB (eNodeB), and the Core Network (CN) nodes, Mobility Management Entity (MME) and Serving Gateway ( FIGS. 1   a  and  1   b  also show the PDN Gateway and the combination of the Serving Gateway and PDN Gateway is also known as SAE-GW which is the term used in this application for both these gateway nodes). The S1 interface (both the S1-MME and S1-U interfaces) may traverse insecure IP networks. One example of such a deployment scenario is the Home eNodeB (HNB) concept currently being studied in 3GPP. 
         [0004]    The S1 interface security is based on IPsec tunnels which are established between the eNodeBs (or HNBs) and the Security GateWays (SEGW) in the network side. The SEGW functionality could theoretically be incorporated in SAE-GW&#39;s and MME&#39;s, however it&#39;s most likely that this will be handled by dedicated equipment due to the quite heavy processing capacity needed for IPsec. 
         [0005]    The signaling sequences to establish a dedicated SAE/LTE bearer is shown in  FIG. 3 . This figure shows as an example that the bearer is created for an IMS VoIP/SIP call/transaction in the case when network initiated bearer activation is applied via the Policy and Charging Rules Function (PCRF). 
         [0006]    The interface between the P-CSCF and the PCRF is called “Rx+”-interface and is based on the Rx-interface which is specified for 3GPP, e.g. Release-7 in 3GPP TS 29.214. The interface between the PCRF and the PDN gateway (and so the SAE-GW) is called S7-interface and is based on the Gx-interface which is specified for 3GPP, e.g. Release-7 in 3GPP TS 29.212. 
       SUMMARY 
       [0007]    The anticipated security architecture would mean that all communication between eNodeBs and SEGWs would need to use IPsec and be encrypted. This will put a heavy processing burden on eNodeBs and the SEGWs even though this strong security might not be needed for all the different types of bearers, e.g. bearer for web browsing or video streaming might not need security etc. In addition, some applications provide security on the application layers and it seems like waste of resources to also have transport level security for the bearers used in these cases. 
         [0008]    This invention allows dynamic selection of security settings on a bearer level. 
         [0009]    These and other advantages are achieved by means of method used in a mobile telecommunications network including at least one access point, at least one gateway device. The method comprises the steps of: deciding a security setting needed for a dedicated bearer signal by a network component, communicating the decision to a node needed for establishing communication, configuring or selecting by the access point a secure protocol as needed between the access point and the gateway devices, and the decision being based on one or several of the network deployments being used and/or network operator policies. According to one embodiment, the network component is an application level component being one or several of Proxy Call Session Control Function, P-CSCF, Interrogating Call Session Control Function, I-CSCF, or Serving Call Session Control Function, S-CSCF, or an IMS Application Server, AS. The network component transmits the security need to PCRF. Preferably, a session that needs security employs the secure protocol with encryption between the access point and the gateway device. In one embodiment, a session with less need for security uses a security protocol with message authentication and null encryption. 
         [0010]    Generally, depending on which node that determines need of security, various protocols and nodes are modified. When the network components decide if a session needs to be secured following information is used: encryption activated or not, level of encryption, message authentication activated or not, level of message authentication. The network components may decide security based on information included in the Session Description Protocol, SDP part of the signalling related to establishment of a session. It is possible that other network components decide security based on Application Server (AS) including additional indication about security need. The S-CSCF uses the indication when forwarding an indication to the P-CSCF which maps security information to a new parameter in an AA-Request (AAR) message. 
         [0011]    According to a second aspect of the invention the network component is PCRF (Policy Control and Charging Rules Function). The PCRF transmits the security information in a Re-Auth-Request (RAR) message to the SAE-GW which forwards the information to Mobility Management Entity, MME, and finally MME informs the access point about security setting requested together with additional information for the bearer to be established between the access point and gateway devices. The access points comprise information about the requested security setting and needed transport address information for the bearer signal to be established and the address information of the gateway devices IP-address and optionally a User Datagram Protocol, UDP, port for the bearer and based on this information the access point checks if a new IPsec relationship description, i.e. an IPSec Security Association (SA) needs to be established or if an existing IPsec SA can be used unmodified or needs to be updated. The method may further comprise using different transport address information for different bearer signals. The gateway device selects a local  1 P network address and signals this to the access point as part of the bearer establishment signalling. The gateway device may have separate logical IP-addresses locally based on multi-homing and comprises logical unit to select different local IP-addresses depending on the requested security setting. Preferably, GPRS Tunnelling (GTP) protocol may be used. The method may further comprise changing GPRS Tunnelling (GTP) protocol and selecting dynamically UDP port to be used for the different bearers and signalled between end nodes. The access point is configured to create a binding between a created radio bearer and the GTP tunnel to be used. 
         [0012]    The traffic may be mapped in downlink to different IPsec SAs by the gateway by using a traffic selector to map the traffic to different IPsec SAs. The PCRF may contain needed policies to decide what level of security is needed for different bearers. 
         [0013]    The decision on security settings may be updated based on a user equipment, UE, moving between different types of access points. The access point receives new parameter as part of handover and relocation signalling. When the access point receives an indication of the incoming handover request, it also receives information about the needed Serving GW addresses and security settings for all the active bearers that are to be handed over to the access point. 
         [0014]    In one embodiment, the application level component selects a security level including an indication about the level in Session Description Protocol, SDP, and transmitting to P-CSCF. The information or parts of thereof are transmitted in one or several of: over Rx+/Rx-interface of P-CSCF in SDP to the PCRF, a Diameter protocol on Rx+/Rx-interface, S7/Gx interface between the PCRF and the SAE-GW or PDN gateway part of SAE-GW, S11 interface between SAE-GW and MME, S1-MME interface between MME and eNodeB. 
         [0015]    The invention also relates to an infrastructure device adapted to receive and transmit signals to mobile stations and communication network, the device comprising memory, processing arrangement and receiver/transmitter arrangement for receiving/transmitting dedicated bearer signals. The receiver is further configured to receive a decided security setting, the decision being based on one or several of network deployments being used and/or network operator policies needed for a dedicated bearer signal by a network component in the network, and means to configure a secure protocol (IPsec) as needed between the device and a gateway device. 
         [0016]    The invention also relates to a functional element (PCRF) in a communications network comprising means to receive a signal for indication of security need requests depending on operator policies for different applications and current network deployments used. The functional element comprises: means for including this indication in a bearer establishment signalling to network nodes, whereby a security level is selected depending on application needs and/or the current network being used, and a logic part comprising means to decide whether security is needed and a level of security to apply based on. The application level components, which may be one or several of P-CSCF, IMS AS, are configured to indicate that security needs are to be applied on the bearer. The network nodes comprise one or several of MME, eNodeB or SAE-GW. 
         [0017]    The invention also relates to a data structure for use in a mobile telecommunications network, the network including at least one access point, at least one gateway device and at least one network component, the network component being configured to decide a security setting needed for a dedicated bearer signal, wherein the data structure comprises information on: encryption activation status, level of encryption, message authentication activation and/or level of message authentication. 
         [0018]    It should be understood by a skilled person that the access point mentioned does not limit the invention to a WLAN or similar access points but merely concerns a network accessing arrangement. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The present invention will be described in more details with reference to a number of drawings, in which: 
           [0020]      FIGS. 1   a  and  1   b  show conventional architectures so far agreed as part of the SAE/LTE standardization work in 3GPP, 
           [0021]      FIG. 2  is a network according to the present invention, 
           [0022]      FIG. 3  is a signal flow diagram according to the prior art, 
           [0023]      FIG. 4  is a signal flow diagram according to the present invention, 
           [0024]      FIG. 5  is a flow diagram illustrating the steps according to the present invention, 
           [0025]      FIG. 6  is a block diagram schematically illustrating an infrastructure node device according to the present invention, 
           [0026]      FIG. 7  is a block diagram schematically illustrating an access point device according to the present invention, and 
           [0027]      FIG. 8  is a block diagram schematically illustrating a functional element according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    In the following, the invention is described with reference to a general solution exemplified by reference to a LTE and SAE. However, it should be appreciated that the teachings of the invention can be applied to any network having nodes and infrastructure entities with ability to perform the teachings of the present invention. 
         [0029]    Generally, the needed additions are made to the protocols and architecture to allow dynamic control of encryption and other security settings in the S1-interface. 
         [0030]      FIG. 2  illustrates the invention in a network. The network  200  consists of Internet  201  and Intranet  202  parts. The Internet  201  (or some other public and unsafe networks) can be used to provide parts of the connectivity between the eNodeB  203  and the SAE Core Network elements (i.e. MME and Serving Gateway) in the safe Intranet  202 . In this case the eNodeBs  203  (eNB) are connected to the Intranet  202  through Security Gateways (SEGW)  204 . Communication is enabled and secured using IPsec tunnels  205 . SEGWs  204  enable communication for the eNodeBs  203  towards the SAE-GW  206  and MME  207 , which are also interconnected. SAE-GW  206  communicates with PCRF  208 , communicating with P-CSCF  209  communicating with IP Multimedia Subsystem (IMS) CN  210 , which communicates with one or more IMS Application Servers (AS)  211 . 
         [0031]    Depending on, e.g. operator policies for the different applications and(/or) the current network deployment being used, such as for a voice call, the application level components (e.g. P-CSCF or IMS AS in the case for IMS VoIP call) can indicate that security needs to be applied on the bearer. This is signaled to the PCRF  208 , which includes this indication in the bearer establishment signaling to the MME  207 , eNodeB  203  and SAE-GW  206 . This means that the security level is selected depending on application needs and the current network being used. In this way, a web browsing session, for example, can be done, using for example null encryption between eNodeB and SAE-GW and thus saving processing resources. Another possibility is that the PCRF contains the operator policies and the needed logic to decide whether security is needed for a specific application. The logic part is substantially the same as described earlier, i.e. the PCRF comprises means to decide whether security is needed and the level of security to apply based on, e.g. the requested bearer, the bearer properties, and the application requesting the bearer. 
         [0032]    Additionally, the P-CSCF may include in an AA-Request message an order to indicate the particular service that an Application Function (AF) session belongs to. This information can then also be used by the PCRF to decide the security level to be selected and communicated to the other nodes. In addition, the PCRF may receive the entire Session Description Protocol (SDP) describing the session to be established and any part of the SDP can be used in the selection of the security level. 
         [0033]    The Policy and Charging Control (PCC) Rule Function (PCRF) decisions may be based on one or more of the following:
       the session and media related information obtained from the AF via the Rx+/Rx reference point;   the bearer and subscriber related information obtained from the Policy and Charging Enforcement Function (PCEF) over the S7/Gx reference point. The SAE-GW is functioning as the PCEF in the exemplary network scenario described;   subscriber and service related data the PCRF may be aware of by configuration or through the Sp reference point (from the SPR);   pre-configured information in the PCRF.       
 
         [0038]    These rules (or subset) may also be used when selecting the security level. 
         [0039]    In more detail, substantially the main steps of the invention, illustrated in  FIG. 5 , are the following:
         501 : Either one or more of the application level nodes or the PCRF node identify the security settings needed for a dedicated bearer. This decision is based on current network being used and the network operator policies for the different applications,     502 : The above decision is communicated to all the needed nodes and     503 : Finally the eNodeB receiving the information and configuring the IPsec Security Associations (SA) as needed between the eNodeB and the SEGW.       
 
         [0043]    The sessions that need security use IPsec with encryption between the eNodeB and the SEGW. Sessions with less need for security could for example use IPsec with message authentication and ‘null encryption’. This would lower the processing requirements substantially in both the eNodeBs and the SEGWs. 
         [0044]    Another alternative would be to send data that do not require security outside the IPsec tunnel, but the most likely case would probably be to use ‘null encryption’ with message authentication. 
         [0045]    This would mean that (at least) two different IPsec tunnels (or two different IPsec SAs for one IKE SA) need to be established between eNodeB and SEGW, one with encryption and one without. The number of IPsec SAs could be higher than two if there is for example need to have different levels of encryption or different levels of message authentication. The main point is that the number of needed IPsec SAs between the eNodeB and the SEGW is based on the number of different security settings needed for the different bearers transported between the eNodeB and the SEGW. 
         [0046]    An automatic way to handle the establishment of the IPsec SA&#39;s is outlined below. 
         [0047]    The invention provides methods, procedures, protocols and node modifications in order to control the selection of the IPsec SAs to use between the eNodeB and the SEGW for both uplink and downlink traffic for the different bearers that are transported between the eNodeB and the SEGW. 
         [0048]    Depending on which node that determines if security is or is not needed, various protocols and nodes need to be modified. For example, once application level components have selected the security level then the indication about this is included in the SDP and passed to the P-CSCF which then passes the information in e.g. SDP over the Rx+/Rx-interface to the PCRF. Other possibility is to include some information in the Diameter protocol itself on the Rx+/Rx-interface. Another example is similar approach for the S7/Gx-interface and protocols used in this interface. 
         [0049]    Referring now to  FIG. 4 , assuming that it&#39;s the application level components (e.g. S-CSCF in the IMS CN or IMS AS) that decide if session needs to be secured and indicate that for example in the SDP sent to the P-CSCF (the latter shown in  FIG. 4 ), the following messages and corresponding node logic needs to be enhanced, highlighted in the sequence. The “new parameter” shown in the figure is the needed addition in the shown messages and protocols. It may contain different levels of configuration related to the security used between the eNodeB and the SEGW and it may contain e.g. the following information: 
         [0000]    a encryption activated or not,
 
b level of encryption,
 
c message authentication activated or not,
 
d level of message authentication.
 
         [0050]    The application level components (e.g. S-CSCF or AS) could decide based on information included in the Session Description Protocol (SDP) for the session to be established (or modified) that security is needed for this session and one or more of the associated bearers. This could also be based on AS including on additional indication about that security is needed in for example the SDP and then the S-CSCF using that indication when forwarding the indication to the P-CSCF which maps the security information to a new parameter in the AA-Request (AAR) message sent to the PCRF over the Rx+/Rx interface. The PCRF sends on the security information in the Re-Auth-Request (RAR) message to the SAE-GW over the S7/Gx interface, the SAE-GW then forwards the information to MME over the S11 interface and finally MME informs the eNodeB (over the S1-MME interface) about the security setting requested together with all other information for the bearer to be established between the eNodeB and the Serving GW (i.e. the part of SAE-GW that is visible towards the eNodeB). 
         [0051]    At this stage the eNodeB knows the requested security setting and also the needed transport address information for the bearer to be established. The transport address information consists of the Serving GW IP-address and optionally a Serving GW UDP port for the bearer. Based on this information the eNodeB can check if a new IPsec SA needs to be established or if an existing IPsec SA can be used unmodified or if an existing IPsec SA needs to be updated. The main problem here is to ensure that the established bearers are mapped to the correct IPsec SAs in both directions, i.e. in the uplink by the eNodeB and in the downlink by the SEGW. The uplink direction means here the direction from the UE towards the network i.e. from the eNodeB towards the SEGW in this context and the downlink direction means the opposite direction. The SEGW is not part of the bearer establishment even though the associated signaling is sent transparently through the SEGW. The eNodeB needs to ensure that the Traffic Selectors (TS) for the IPsec SAs in both the eNodeB and in the SEGW match the Serving GW transport address information for the established bearers. 
         [0052]    The TSes are defined separately in uplink (called TSi as Traffic Selector initiator) and downlink (called TSr as Traffic Selector responder). The TSes are defined for each IPsec SA and are effectively used to decide how the IP traffic and IP protocol messages are mapped to the different IPsec SAs. The information included in the TSes is IP-address (range), TCP/UDP port (range) and protocol information. This means that the different bearers that need different security settings must use different transport address information. This is needed so that the SEGW can map the traffic in the downlink to the correct IPsec SAs with correct security settings. 
         [0053]    The above need to use different transport address information for the different bearers means that either the IP-address or the UDP-port needs to be different for the different bearers. In the SAE case it is very likely that the Network initiated bearer activation procedure is used, and it is the Serving GW that selects the local IP network address and signals this to the eNodeB as part of the bearer establishment signaling. This means that the Serving GW would need to have separate logical IP-addresses locally based on e.g. multi-homing and have the logic to select different local IP-addresses depending on the requested security setting. This alternative should be possible with the existing GPRS Tunneling Protocol (GTP) which will to a certain extent be reused in the LTE/SAE architecture. 
         [0054]    Another option that would mean changes to the GTP protocol is that also the UDP port to be used for the different bearers is dynamically selected and signaled between the end points (i.e. Serving GW and eNodeB). Presently, the GTP protocol is specified to use one fixed UDP port. In this case the Serving GW would have the logic to select different local UDP ports depending on the requested security setting. 
         [0055]    Thus, using the above mechanisms, the eNodeB has ensured that the TSes for the IPsec SAs are correctly updated in both the eNodeB and the SEGW. The next step is to ensure that the traffic is also correctly mapped to these IPsec SAs. The eNodeB also creates a binding between the created radio bearer and the GTP tunnel to be used. The GTP-tunnel information contains the IP-address (and UDP port) to be used so when the eNodeB receives traffic from an UE using a specific radio bearer, it is capable of mapping this to a GTP tunnel. When the traffic is encapsulated with the IP address and UDP port information, the IPsec implementation in the eNodeB uses the traffic selectors to find the correct IPsec SA to send the traffic on towards the SEGW. 
         [0056]    The mapping of traffic in the downlink to different IPsec SAs is done by the SEGW. In this case, the SEGW doesn&#39;t have any information about the established GTP tunnels and uses the traffic selectors (as updated by the eNodeB) to map the downlink traffic to the different IPsec SAs towards the eNodeB. This would be standard functionality but is easily applied only in the case that different UDP-ports are used for different bearers. Otherwise the eNodeB would need to also have (at least) two different IP addresses. 
         [0057]    If it is decided that for example the IMS CN (e.g. I-CSCF or S-CSCF) is the decision point, logic needs to be added in these nodes and the SDP sent would need to be modified by a node in IMS CN, i.e. depending on decision point different protocols and node logic needs to be updated. 
         [0058]    As mentioned before, still an additional approach would be to keep the Rx+/Rx-interface unmodified and let the PCRF contain the needed policies to decide what level of security is needed for the different bearers as described earlier 
         [0059]    As the decision on the security settings may be based on the current network deployment and(/or) the type of the eNodeB being used, the security settings might also be updated because of the UE  220  moving between different types of eNodeBs (i.e. from the source eNodeB to the target eNodeB). This means that the target eNodeB needs to receive the described new parameter also as part of handover and relocation signaling so that the same logic can also be applied in these cases. By doing this, the invention may cover more cases than described, i.e. initial bearer establishment case. When the target eNodeB receives the indication of the incoming handover request, it also receives information about the needed Serving GW addresses and security settings for all the active bearers that are to be handed over to this eNodeB. The target eNodeB can then perform the same steps as described earlier i.e. if a new IPsec SA needs to be established or if an existing IP sec SA can be used unmodified or if an existing IPsec SA needs to be updated. 
         [0060]      FIG. 6  illustrates in a schematic block diagram an infrastructure node according to the present invention, wherein a processing unit  601  handles communication data and communication control information. The infrastructure node  600  further comprises a volatile (e.g. RAM)  602  and/or non volatile memory (e.g. a hard disk or flash memory)  603 , and an interface unit  604 . The infrastructure node  600  may further comprise a downstream communication unit  605  and an upstream communication unit  606 , each with a respective connecting interface (not shown). All units in the infrastructure node can communicate with each other directly or indirectly through the processing unit  601 . Software for handling communication to and from the mobile units and other network elements attached to the network is at least partly executed in this node and may be stored in the node as well; however, the software may also be dynamically loaded upon start of the node or at a later stage during for instance a service interval. The software can be implemented as a computer program product and distributed and/or stored on a removable computer readable media, e.g. diskette, CD (Compact Disk), DVD (Digital Video Disk), flash or similar removable memory media (e.g. compactflash, SD secure digital, memorystick, miniSD, MMC multimediacard, smartmedia, transflash, XD), HD-DVD (High Definition DVD), or Bluray DVD, USB (Universal Serial Bus) based removable memory media, magnetic tape media, optical storage media, magneto-optical media, bubble memory, or distributed as a propagated signal via a network (e.g. Ethernet, ATM, ISDN, PSTN, X.25, Internet, Local Area Network (LAN), or similar networks capable of transporting data packets to the infrastructure node). 
         [0061]    An infrastructure device  700 , e.g. eNodeB, illustrated very schematically in  FIG. 7 , adapted to receive and transmit signals to mobile stations and a communication network. The device comprises processor  701 , memory unit  702  and receiver and transmitter arrangements or interfaces  703  and  704 , respectively, for receiving transmitting dedicated bearer signals. The memory comprises instruction-set to configure the device to receive a decided security setting. The decision as mentioned earlier is based on one or several of network deployments being used and network operator policies needed for a dedicated bearer signal by a network component in the network. The processor further is arranged to instruct to configure a secure protocol (IPsec) as needed between the device and a gateway device. 
         [0062]    A functional element  800 , e.g. PCRF, is illustrated very schematically in  FIG. 8 , may comprise:
       processing arrangement  801 ,   memory unit  802 ,   a receiver  803 , which also receives a signal for indication security settings depending on operator policies for different applications and current network deployments used   logical unit  804  for including the indication in a bearer establishment signalling to network nodes, whereby a security level is selected depending on application needs and the current network being used,   transmitter part  805 , and   a logic part  806  comprising means to decide whether security is needed and a level of security to apply based on security need requests.       
 
         [0069]    The logical part and unit may of course comprise of the processing arrangement. 
         [0070]    It should be noted that those terms specific for special network standards are given as examples in the embodiments and similar wordings for entities and items having same functionality are not excluded from the invention. 
       ABBREVIATIONS 
       [0000]    
       
         AF Application Function 
         AVP Attribute Value Pair 
         CRF Charging Rules Function 
         IP-CAN IP Connectivity Access Network 
         PCC Policy and Charging Control 
         PCEF Policy and Charging Enforcement Function 
         PCRF Policy and Charging Rule Function 
         PDF Policy Decision Function 
         P-CSCF Proxy-Call Session Control Function 
         QoS Quality of Service 
         SDF Service Data Flow 
         SPR Subscriber Profile Repository 
         UE User Equipment