Abstract:
A selective blocking request is sent from a requesting network element to an SCF (system control function component), where the request identifies a targeted network element. The SCF may then block communications from the targeted network element to the requesting network element, or it may send an ACG (automatic code gapping) message to the targeted network element requesting it to stop sending communications to the requesting network element. This technique offers the advantage of allowing an overloaded network element to reduce its workload while informing other components of the network that messages from a targeted network component will not be accepted by the overloaded network element.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to communication systems; more particularly, controlling traffic in communication systems. 
   2. Brief Description of the Related Art 
     FIG. 1  illustrates a typical communication system. The communication system consists of network elements or components  10 ,  12 ,  14  and  16 . The network elements (NEs) each communicate with a central system control function component (SCF)  18 . Central system control function  18  coordinates traffic between the network elements and may be, for example, a network signaling center or a traffic routing node. In the case of a wireless communication system, the network elements may be, for example, mobile switching centers (MSCs) or base stations. Additionally, wireless communication systems include components such as home location register (HLR)  20  and wireless network point (WNP)  22 . The home location register is used, for example, to authenticate the identity of mobiles requesting access to the network, and wireless network point  22  may be a wireless base station or an access point in a wireless local area network. 
   The SCF controls its workload by controlling the communications between it and each of the network elements. For example, if SCF  18  is overloaded by communications from a particular network element, such as network element  12 , it may send an ACG (automatic code gapping) message or block command to network element  12 . The AGC message commands network element  12  to stop sending messages to SCF  18  for a specified length of time. The ACG message is known as a automatic code gapping message in networks using the ANSI-41 communication protocol. In addition to the SCF becoming overloaded, it is possible for a network element such as network element  16  to become overloaded. In this case, network element  16  simply stops accepting communications from the SCF in order to reduce its workload. Unfortunately, SCF  18  and any network element or component trying to communicate with network element  16 , is not informed of the overload condition at network element  16 . This results in network element  16  ignoring messages sent from other elements or components within the network while the elements or components sending the messages are operating under the assumption that network element  16  is receiving and responding to messages sent. 
   SUMMARY OF THE INVENTION 
   The present invention solves the aforementioned problems by providing a selective blocking request that is sent from a requesting network element to an SCF (system control function component), where the request identifies a targeted network element. The SCF may then block communications from the targeted network element to the requesting network element, or it may send an ACG (automatic code gapping) message to the targeted network element requesting it to stop sending communications to the requesting network element. This technique offers the advantage of allowing an overloaded network element to reduce its workload while informing other components of the network that messages from an identified network component will not be accepted by the overloaded network element. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a communication network; 
       FIG. 2  illustrates a communication network using a selective blocking request; 
       FIG. 3  illustrates the format of a selective blocking request; 
       FIG. 4  illustrates the control flow of a selective blocking request and the format of an ACG message; 
       FIG. 5  illustrates a flow diagram of a network element sending a blocking request to an SCF; 
       FIG. 6  illustrates the flow diagram followed by an SCF when it receives a selective blocking request from a network element; 
       FIG. 7  illustrates a flow diagram for a network element when it receives a message during a blockout period; and 
       FIG. 8  illustrates a flow diagram for an SCF that receives a message during a blockout period. 
   

   DETAILED DESCRIPTION 
     FIG. 2  illustrates a communication network such as a wireless communication network having network components such as network elements (NEs)  30 ,  32 ,  34  and  36 . The network elements may be, for example, mobile switching centers or base stations. The network also includes components such as home location register (HLR)  38 , wireless network point (WPN)  40  and system control function component (SCF)  42 . Wireless network point  40  may be, for example, a wireless base station or an access point on a wireless local area network. When network element  36  (the requesting NE) becomes overloaded it may send a selective blocking request to SCF  42 . The selective blocking request specifies which of the network elements (the targeted NE) should be blocked from sending messages to network element  36 . The request may also include the duration of time over which the selective block should remain in effect, and it may also include intervals during the blocking period when a message may be accepted from the blocked or targeted network element. In response to receiving the selective blocking request, SCF  42  sends a response message back to requesting network element  36  indicating whether the request is accepted or rejected. If the blocking request is accepted, SCF  42  will block communications from the targeted network element, or it will send an ACG (automatic code gapping) message to the targeted element informing the targeted element not to send messages to the requesting network element. 
     FIG. 3  illustrates the format of the selective blocking request. Command field  60  identifies the message as a selective blocking request. Address field  62  identifies the address of the targeted element; the targeted element is the element or network component from which requesting element addressed messages should be blocked. Duration field  64  indicates the duration of time or blocking period over which messages from the targeted element should be blocked. Subduration field  66  indicates the intervals during the duration time or blocking period when a message will be accepted from the targeted network element. Typically, one message is accepted per interval specified by the subduration field. Action field  68  provides a command to the targeted network element indicating, for example, where messages that are blocked should be sent as an alternative to the requesting network element. For example, the messages may be sent to a network element that has a load sharing function with the requesting network element. It should be noted that the command provided in action code field  68  may be modified by SCF  42 . 
     FIG. 4  illustrates the control flow associated with the selective blocking request. Initially in step  80 , requesting network element  36  determines through an internal process, such as a load monitoring process, that traffic or messages from a specific origination address such as target network element  32  should be blocked. In step  82 , requesting network element  36  sends a selective blocking request to SCF  42 . The request is a form such as the format discussed with regard to  FIG. 3 . In step  84 , SCF  42  evaluates the effect of the blocking request on the communication network, and based on that evaluation, either accepts or rejects the response. The accept or reject message is then sent to requesting network element  36 . In step  86 , requesting network element  36  then responds based on whether the message from SCF  42  was an accept or reject. For example, if the response was an accept, network element  36  will reject messages received from the targeted network element, and if the response from SCF  42  was a reject, network element  36  will continue to accept messages from targeted network element  32 . In step  88 , if SCF  42  accepted the selective blocking request, ACG message  90  is sent to targeted network element  32 . 
   The ACG message is formatted using several fields. ACGDIR field  92  identifies the message as an ACG message. DESTADDR field  94  identifies the address of the requesting network element  36 . This provides target network element  32  with the address to which messages should not be sent. CTYPE field  96  indicates whether the ACG message is originating from a requesting network element or SCF  42 . GAPDUR field  98  indicates the length of time during which the block is to remain in force. GAPINT field  100  specifies the minimum amount of time the targeted network element must wait before sending another message to the requesting network element. This is based on the subduration field  66  of the original selective blocking request transmitted by the requesting network element  36 . Field  100  may specify the length of time to the beginning of the next interval during which a communication will be accepted, or it may simply specify the times and durations of each of the intervals during which a message may be sent to the requesting network element. 
     FIG. 5  illustrates a flow diagram for a network element sending a selective blocking request to an SCF. In step  110 , the network element determines that a blocking request is required. This determination may be based, for example, on an overload condition at the network element. In step  112 , the selective blocking request message is formatted. The formatting includes providing the address of the targeted network element, the duration of the blocking period, and identifying the intervals during the blocking period when a message will be accepted from a targeted element. In some cases, the selective blocking request includes a suggested action to be taken when messages are not being sent to the requesting network element. These actions may include, for example, sending the messages to a network element that is used to loadshare with the requesting network element. In step  114 , the selective blocking request message is sent to SCF  42 . In step  116 , a response timer is set. In step  118 , it is determined whether a response message is received from SCF  42 . If no response is received, step  120  is executed to determine if the timer has expired. If the timer has expired, a return is executed and the network element continues to perform its normal tasks which may include identifying a different network element for selective blocking. If in step  120 , it is determined that the time has not expired, step  118  is once again executed to determine if a response has been received. If in step  118 , it is determined that a response has been received, step  122  is executed where it is determined whether the response is an accept or reject. If the response was a reject, step  124  is executed where the request is marked as a reject and the requesting network element returns to its normal processing which may include determining whether a selective blocking request should be sent identifying the same or different targeted network element. If in step  122 , it is determined that an accept response is received from the SCF, the targeted address is marked as blocked in step  126 . In steps  128  and  130 , the duration timer and the interval timers are set, respectively. The network element then returns to its normal processing; however, it now blocks messages from the targeted network element. A further discussion of this blocking function will be carried out with regard to  FIG. 7 . 
     FIG. 6  illustrates a flow diagram executed by the SCF when it receives its selective blocking request from requesting network element  36 . In step  150 , the selective blocking request is received. In step  152 , the SCF determines whether or not to accept the request. This determination is made, for example, based on the overall effect on the network that will result from blocking communication between the targeted network element and the requesting network element. If the SCF determines that the blocking request is to be rejected, step  154  is executed where a rejection message is sent to the requesting network element and then the SCF returns to its normal functioning. If in step  152 , it is determined that the blocking request will be accepted, an accept message is sent to the requesting network element in step  156 . In step  158 , the duration timer is set based on the duration of the blocking period as specified in field  64  of the selective block message. In step  160 , interval timer(s) are set to identify the interval or intervals specified in subduration field  66  of the selective blocking request message. These intervals are the times when a message may be transferred from the targeted network element to the requesting network element. Typically these intervals are limited to one message; however, more than one message may be permitted. In step  162 , the address of the targeted network element is marked as blocked. In step  164 , SCF  42  determines whether to send an ACG message or blocking command to the targeted network element. If the SCF is underloaded, it may perform the blocking function at the SCF and not send an ACG message to the targeted network element. If the SCF determines that its present workload does not permit performing the blocking function at the SCF, step  166  is performed where an ACG message is formatted. As discussed with regard to  FIG. 4 , the ACG message identifies the duration, the requesting network element, the blocking duration, intervals when a message may be sent, and an alternative action to be taken in lieu of sending a message to a requesting network element. In step  168 , the ACG message is sent to the targeted network element and then the SCF returns to its normal functioning. 
     FIG. 7  illustrates the actions taken by a requesting network element if it receives a message from a targeted network element during the blocking period. In step  180 , the requesting network element receives a message from the targeted network element. In step  182 , the requesting network element determines whether this is an interval during which a message will be accepted. If it is determined that this is not an interval during which a message will be accepted, in step  184  the message is ignored and then the network element returns to its normal processing. If in step  182 , it is determined that this is an interval during which a message will be accepted, in step  186  the message is processed. In step  188 , it is determined whether the blocking duration has expired. If the duration has not expired, in step  190  the interval timer is reset so that the requesting network element may determine the beginning and end of the next interval during which a message will be accepted. If in step  188 , it is determined that the blocking duration has expired, step  192  is executed where the blocking function is deactivated and then in step  194 , the block duration timer and interval timers are reset. The requesting network element then returns to its normal functioning. 
     FIG. 8  illustrates the flow diagram that SCF  42  executes when it receives a message from a blocked targeted network element. In step  200 , the SCF receives a requesting element addressed message from the targeted network element. In step  202 , the SCF determines whether the message was received during an interval that corresponds to a period during which messages are accepted notwithstanding that a block is in effect. If it is determined in step  202 , that this is not an acceptance interval, the message is ignored in step  204  and then the SCF returns to its normal processing. If in step  202  it is determined that the message was received during an acceptance interval, step  206  is executed where the message is forwarded to the network element that requested the blocking. In step  208 , it is determined whether the blocking duration has expired. If the blocking duration has not expired, step  210  is executed where the interval timers are reset so that the next interval during which communications are accepted may be identified. If in step  208 , it is determined that the blocking duration has expired, step  212  is executed where the blocking function is deactivated and then step  214  is executed where the blocking duration and interval timers are reset. The SCF then returns to its normal functioning.