fig3 illustrates protocol stack configuration for signalling transfer according to an advantageous embodiment of the invention . this figure illustrates the example case that a separate radio bearer is reserved for each cn domain . in fig3 , each radio bearer is represented by a rlc entity corresponding to the radio bearer . fig3 illustrates , that signalling from the circuit switched cn domain ( cm , mm ) is transmitted via a second rlc entity 102 , while signalling from the packet switched cn domain ( sm , pmm ) is transmitted via a third rlc entity 103 , while a first rlc entity is used for transmission of the rest of rrc messages . according to the invention , the rrc protocol can use one or more signalling radio bearers ( srb ) i . e . rlc entities for transmission of signalling traffic between the network and the mobile communication means , i . e . ue ( user equipment ). in other words , the signalling link between a ue and a rnc ( radio network controller ) can comprise one or more signalling radio bearers . the ue can be commanded to use only one signalling radio bearer for all signalling . an additional signalling radio bearer can be set up and the rrc layer and the ue can be configured to send all rrc direct transfer messages using this additional signalling radio bearer . further , more than one signalling radio bearers can be set up by the network . preferably , the network makes the decisions about the configuration of the signalling radio bearers . different rules for using the more than one signalling radio bearers can be used in different embodiments of the invention . for example , in an advantageous embodiment of the invention , separate signalling radio bearers are used for each cn domain protocol stack . such an embodiment is illustrated in fig3 . in such an embodiment , the rrc layer can route the rrc direct transfer messages to correct radio bearer by checking the cn domain identification information in the data units comprising the messages . as a second example , in an advantageous embodiment of the invention , separate signalling radio bearers are used for each higher layer protocol . in such an embodiment , the rrc layer can route the rrc direct transfer messages to correct radio bearer by checking the nas ( network access stratum ) protocol discriminator information in the data units comprising the messages . as a third example , in an advantageous embodiment of the invention , separate signalling radio bearers are used for various predefined groups of higher layer protocols . in such an embodiment , the rrc layer can route the rrc direct transfer messages to correct radio bearer by checking the nas ( network access stratum ) protocol discriminator information in the data units comprising the messages . in such an embodiment , each signalling radio bearer carrying higher level protocol signalling has a corresponding pre - defined set of nas protocol discriminators . the invention is not limited to these rules for deciding about the usage of the signalling radio bearers , since other types of rules can as well be used . for example , the decision of which signalling radio bearer to use for any given message can in an embodiment of the invention based on the pdu size . in such an embodiment , the length of each message is checked , and the bearer to be used is selected at least partly on the basis of the result of this checking . in a further advantageous embodiment of the invention , the routing is based on a quality of service parameter attached to the higher layer protocol data . in such an embodiment , higher layer protocols may add a qos parameter to single messages , to plurality of messages , or for example to all messages in order to ensure , that the messages are routed via a signalling radio bearer fulfilling the desired qos level . in such an embodiment , the rrc layer can route the rrc direct transfer messages to correct signalling radio bearer by checking the additional qos class information from the data units comprising the messages . there can be for example a predefined set of qos classes for higher layer signalling messages , for example two qos classes , or the number of qos classes can be decided by the network . preferably , for each qos class a separate radio bearer is set up . an example of this qos class separation could be the short message service ( sms ) which could use lower priority than other signalling . the functionality for performing the decisions about the number of signalling radio bearers and about the rules for dividing traffic to these signalling radio bearers can be implemented in many different network elements of a radio access network ( ran ). preferably , the network element performing the decisions about the number of signalling radio bearers and about the rules for dividing traffic to these signalling radio bearers is the radio network controller ( rnc ). in a further embodiment of the invention , the rules to be used can be selected out of a predefined set of rules by using the number of signalling radio bearers . in this embodiment , each possible amount of signalling radio bearers is associated with a predefined set of rules . in a further advantageous embodiment of the invention , one of the signalling radio bearers can be defined as a master signalling radio bearer . this radio bearer is set up only in the rrc connection establishment procedure and released only in the rrc connection release procedure . this master srb would be used as the prior art signalling bearer . such an embodiment ensures , that all signalling bearers are not released in error during the rrc connection , since the master srb in this embodiment cannot be controlled by radio bearer control messages . in an advantageous embodiment of the invention , the messages used for controlling radio bearers are used for controlling the signalling radio bearers as well . the messages are the rrc connection setup , radio bearer reconfiguration , radio bearer release , and radio bearer setup messages . the usage of the messages is described in the following with reference to fig4 . in the prior art , these messages are only used to control the user - plane radio bearers , not signalling . more details of the prior art use of these messages and a description of the other messages of the rrc protocols can be found in the rrc protocol specifications of the umts system . fig4 illustrates four rrc layer procedures , namely rrc connection establishment , radio bearer setup , radio bearer reconfiguration , and radio bearer release procedures . the rrc connection establishment procedure initiates the rrc connection between the mobile communication means and the network , while the other three of these four procedures listed here are used to control single radio bearers and may or may not occur during the lifetime of a rrc connection . fig4 shows signalling between a mobile communication means ( ue , user equipment ) and the radio access network ( utran , umts terrestrial radio access network ). the rrc connection establishment procedure is initiated by the ue , which sends 300 a rrc connection request message to the radio access network . the radio access network responds to the message by sending a rrc connection setup message , which comprises information about various parameters about the rrc connection to be established . the ue finishes the rrc connection establishment procedure by sending 310 a rrc connection setup complete message . the radio bearer setup procedure is initiated by the network , which sends 320 a radio bearer setup message to the ue . the message comprises information about various parameters of the radio bearer about to be established . the ue responds to the message by sending 325 a radio bearer setup complete message . the radio bearer reconfiguration procedure is initiated by the network , which sends 330 a radio bearer reconfiguration message to the ue . the message comprises information about new values of parameters for the radio bearer or bearers affected . the ue responds to the message by sending 335 a radio bearer reconfiguration complete message . the radio bearer release procedure is initiated by the network , which sends 340 a radio bearer release message to the ue . the message comprises information identifying the bearer to be released . the ue responds to the message by sending 335 a radio bearer release complete message . according to an advantageous embodiment of the invention , the setting up and configuration of all the signalling radio bearers is done during the rrc connection establishment procedure . this can advantageously be effected by adding information about the signalling radio bearers to be established to the rrc connection setup message . one advantageous example of the organization of such information is presented later in this application . in one advantageous embodiment of the invention , only one signalling radio bearer is set up and configured during the rrc connection establishment procedure . in such an embodiment , further signalling radio bearers can be set up and configured later during the rrc connection , if need for that arises . in an advantageous embodiment of the invention , the radio access network can set up additional signalling radio bearers during the rrc connection and configure how the higher layer signalling is mapped into the new and existing signalling radio bearers . this can advantageously be effected by adding information about the signalling bearers to be established to the radio bearer setup message . one advantageous example of the organization of such information is presented later in this application . in an advantageous embodiment of the invention , the radio access network can re - configure the mapping between higher layer signalling and any existing signalling radio bearer during the rrc connection . this can advantageously be effected by adding information about the signalling bearers to be reconfigured to the radio bearer reconfiguration message . one advantageous example of the organization of such information is presented later in this application . in an advantageous embodiment of the invention , the radio access network can release any signalling radio bbearers during the rrc connection and reconfigure the mapping between higher layer signalling and any remaining signalling radio bearers . this can advantageously be effected by adding information about the signalling bearers to be released and the new reconfiguration information to the radio bearer release message . one advantageous example of the organization of such information is presented later in this application . the following paragraphs and tables show examples according to various advantageous embodiments of the invention about how information pertaining to signalling radio bearers can be presented in the referred messages . in the rrc connection setup message , the information about signalling radio bearers can be presented among the radio bearer information elements as shown in the following table . note that for clarity , the following table lists only radio bearer ( rb ) information elements of the message . the parameter “ signalling radio bearer information ” indicates the number of signalling radio bearers . the other four parameters are then repeated the indicated number of times . the parameter “ rb identity ” identifies the radio bearer . the purpose of the “ signalling radio bearer type ” information element is to indicate the rlc parameters needed for the signalling radio bearer . advantageously , each possible value of “ signalling radio bearer type ” information element refers to a predefined set of parameters . the parameter “ rb mapping info ” indicates , as in prior art , details about multiplexing rlc frames to physical layer channels . the parameter “ srb mapping info ” indicates how various protocol messages are mapped to the particular srb . the parameter “ maxsrbcount ” defines the maximum number of signalling radio bearers . in the radio bearer reconfiguration message , the srb information can be represented by a “ srb mapping info ” parameter among the rb information elements . the parameter is optional , and only present if the particular radio bearer is a signalling radio bearer . in the radio bearer release message , the srb information can be represented by a “ srb mapping info ” parameter among the rb information elements . the parameter is optional , and only present if the particular radio bearer is a signalling radio bearer . in the radio bearer setup message , the srb information can be represented by a “ srb mapping info ” parameter among the new rb information elements , if the particular new rb is to be a srb , and by a “ srb mapping info ” parameter among information elements for other radio bearers affected by the message , if the particular other rb is a srb . these parameters are optional , and only present if the particular radio bearer is a signalling radio bearer . in one advantageous embodiment of the invention , the allowed values of “ srb mapping info ” parameter i . e . information element range from 0 to 7 with the following meanings : 0 all rrc signalling 1 all rrc signalling except rrc direct transfer messages 2 all rrc direct transfer messages 3 rrc direct transfer messages with specified cn domain identities 4 rrc direct transfer messages carrying nas message with the specified pd 5 only the specified rrc messages 6 - 7 reserved for future use if the value is 3 , 4 , or 5 , then also information elements describing details of correspondingly cn domain identities , nas pd information , and rrc message types are present . fig5 illustrates a method according to an advantageous embodiment of the invention . fig5 illustrates a method for transmission of signalling data in a cellular telecommunication system between the cellular network and a mobile communication means . according to the example of fig5 , the method comprises steps of setting up 200 of at least two signalling radio bearers for transmission of signalling traffic , and configuring 201 of how the signalling of higher layer protocols is mapped to said signalling radio bearers . according to an advantageous embodiment of the invention , the method further comprises the step of routing 210 of signalling traffic data units via said at least two signalling radio bearers according to predefined rules . in a further advantageous embodiment of the invention , said predefined rules are set by a network element of a radio access network of the cellular telecommunication system . in a still further advantageous embodiment of the invention , said predefined rules are set by a radio network controller . according to an advantageous embodiment of the invention , in said step of routing 210 , signalling from different core network domains is routed 210 a via separate signalling radio bearers . according to a further advantageous embodiment of the invention , in said step of routing 210 , signalling of a higher layer protocol is routed 210 b via a signalling radio bearer specific to said higher layer protocol . according to a still further advantageous embodiment of the invention , in said step of routing 210 , signalling traffic of a predefined group of higher layer protocols is routed 210 c via a signalling radio bearer corresponding to said pre - defined group . according to a still further advantageous embodiment of the invention , in said step of routing , signalling traffic of higher layer protocols is routed via a signalling radio bearer based on a quality of service parameter attached to the higher layer protocol data . in a further advantageous embodiment of the invention , said setting up and configuration of said signalling radio bearers is performed during the rrc connection establishment procedure . in an even further advantageous embodiment of the invention , the method comprises steps of setting up of a further signalling radio bearer during the rrc connection , and configuring the mapping of higher layer signalling to said further signalling radio bearer and previously existing signalling radio bearers . in an even further advantageous embodiment of the invention , the method comprises the step of reconfiguring the mapping of higher layer signalling to said signalling radio bearers . in an even further advantageous embodiment of the invention , the method comprises the step of releasing a signalling radio bearer . fig6 illustrates the functional structure of a typical radio network controller 400 of a cellular telecommunications network using as an example the structure of a rnc of a umts radio network utilizing wcdma ( wideband code division multiple access ) transmission method . the invention is not limited to the umts system , but can be used in other similar systems as well . the radio network controller 400 comprises a switching fabric unit ( sfu ) 450 to which several control processor units can be connected . multiplexing units ( mxu ) 440 can be used between a number of processor units and the sfu to map the low bit rate data flows from the processor units into the high bit rate data flows of the sfu input ports . the network interface units ( niu ) 410 handle the physical layer connections to different interfaces , such as iub interface toward node b elements , iur interface towards other rncs , and the iu interface towards core network nodes . the operations and maintenance unit ( omu ) 430 contains the rnc configuration and fault information and can be accessed from external operations and maintenance center . the signalling units ( su ) 420 implement all the control and user plane protocols required in the rnc . accordingly , the invention can be implemented in a rnc in the signalling units 420 . the invention can be implemented using means 460 comprising software executed in the processors of the signalling units , which software causes the signalling units to perform according to the invention . in an advantageous embodiment of the invention , a network element of a radio access network of a cellular telecommunication system is provided . according to the embodiment , the network element is arranged to set up at least two signalling radio bearers for transmission of signalling traffic and to configure how the signalling of higher layer protocols is mapped to said signalling radio bearers . in a further advantageous embodiment of the invention , the network element is a radio network controller . fig7 illustrates roughly the functional structure of a typical mobile communication means ( ue ) 500 . the ue comprises a user interface ( ui ) 550 , a control unit 540 , a dsp unit 530 , an rf unit 520 , and an antenna 510 . the rf unit handles the radio frequency processing of received and transmitted signals and converts the received signals to digital form . the dsp unit handles physical layer processing such as interleaving , channel coding , multiplexing , and segmentation . the dsp unit 530 can also implement a part of or all of layer 2 radio protocols such as the mac , rlc , and pdcp protocols . layer 3 protocols such as the rrc , mm , and cm protocols and typically also a part of layer 2 protocols are implemented in the control unit 540 . accordingly , the invention can be implemented in a ue in the control unit 540 . the invention can be implemented using means 560 comprising software executed in the processor 570 of the control unit , which software causes the control unit to perform according to the invention . according to a further advantageous embodiment of the invention , a mobile communication means for a cellular telecommunication system is provided . according to the embodiment , the mobile communication means is arranged to route radio resource control protocol messages to at least two signalling radio bearers as instructed by the cellular telecommunication system . the present invention has several advantages . for example , the inventive solution retains the beneficial aspects of the prior art solutions described previously , while retaining the present specifications as unmodified as possible . further , the inventive approach allows keeping of integrity protection in one protocol layer only , i . e . in rrc . the inventive method avoids the prior art problem of increasing the complexity of the pdcp protocol . the inventive method is at the time of writing this patent application fully compatible with the present solutions regarding cnd domain concepts and routing of higher layer signalling messages from or to cn domains based on cn domain identification information . the inventive method also requires no changes to iu interface specifications . the inventive method also allows prioritization between different types of signalling , such as between rrc signalling and higher layer signalling . the inventive method further allows the use of different qos parameters for different types of signalling . further , the inventive solution will also allow usage of different integrity algorithm for nas ( network access stratum ) and as ( access stratum ) signalling , if that would be later required . this can be effected by allocating separate bearers for these signalling flows , and applying a bearer specific integrity algorithm for the bearers . in the present application the term signalling is intended to cover transmission of messages of various protocols controlling various aspects of the functioning of the cellular telecommunication systems , i . e . other transmissions than payload data transmissions . the term higher layer protocol is in this application and particularly in the accompanying claims intended to cover the radio resource control protocol and any other layer 3 protocol acting between the mobile station and the radio access network and all layer 3 or higher layer signalling protocols between the mobile station and core network , such as for example the mobility management , call control , and session management protocols . the invention is applicable in so called third generation mobile cellular systems , such as the umts system ( universal mobile telecommunication system ) and corresponding systems . the various message names such as the rrc direct transfer message name are intended to be examples only , and the invention is not limited to using the message names recited in this specification . in view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention . while a preferred embodiment of the invention has been described in detail , it should be apparent that many modifications and variations thereto are possible , all of which fall within the true spirit and scope of the invention .