MXPA98010332A - Registration of data terminals of mobile packages after a transtorno in a system - Google Patents

Abstract

The present invention relates to attempts to register by a terminal (10,20,30,40,50,60) that uses a containment protocol to communicate with a central system (100) that are controlled by transmitting a registration index (510). ) from the central system to the terminal at specified time periods and modify the value of the registration index when the terminal must try with the central system. A mode indicator (515) is transmitted from the central system to the terminal at predetermined time intervals and the value of the mode indicator is modified when the central system recovers from a disaster, such that the terminal has to attempt to register immediately with the central system. During disaster recovery, the terminal has the ability to associate itself with one of a plurality of subintervals. The central system transmits a sub-interval designator (520) to the terminal at regular time periods during disaster recovery. The central system modifies the value of the sub-interval designator after a predetermined number of regular time periods. The flow of registration attempts by a community of terminals becomes uniform from a situation where essentially the entire terminal community refuses to register after a disaster to a situation where the sub-assemblies of the community attempt to register in respective sub-sets. -intervals after the disaster

Description

REGISTRATION OF MOBILE PACKAGE DATA TERMINALS AFTER A DISORDER IN A SYSTEM BACKGROUND OF THE INVENTION The present invention is concerned with a wireless packet data communication system having a central system and mobile terminals, and in particular with the recovery of a disaster in the central system. In a communication system that has a central system and mobile directional terminals, there is a sending or downstream channel, and a reverse or upstream channel. In the downstream channel, the central system broadcasts accessible information to, sometimes referred to as an ear, by all mobile terminals. Downstream broadcasting comprises control messages of the system including control messages at predetermined time intervals and message data packets respectively addressed to a single mobile terminal (or group of terminals sharing a common address). The downstream diffusion is essentially continuous. The downstream channel can comprise several frequencies and the central system can use a frequency for its transmission, or it can jump between frequencies. In the upstream channel, the mobile terminals respectively transmit REF data packets: 28784 messages and data related to the system to the central system using a containment protocol where, if the packets fail, retransmission is attempted after an interval of essentially random time. Mobile terminals communicate directly only with the central system, they do not communicate with each other. The upstream channel may comprise several frequencies and a mobile terminal may use a frequency for its transmission or may jump between frequencies. The communications system is designed in such a way that the central system is aware that each mobile terminal has the ability to communicate with it. When a new mobile terminal enters the geographic area that is serviced by the central system, which is presented from time to time, the mobile terminal must be registered with the central system. Registration begins when a mobile terminal sends, via the upstream channel, its public identity number to the central system together with a request for a temporary identifier. The public identification number and the temporary identifier request are examples of data related to the system. The central system responds by sending, via the downstream channel, a temporary identifier, which is a randomly chosen number in a predetermined range which has not been previously assigned to any other mobile terminal, in the range of communications of the central system, to the requesting mobile terminal. The temporary identifier is an example of a system control message which is sent as needed, that is, not at a regular interval. During the registration, the central system adds to its routing table an entry comprising the external address of the mobile terminal and the temporary identifier assigned to the mobile terminal. The channeling table may also include an upstream frequency for the mobile terminal. It will be appreciated that the routing table changes frequently due to the mobility of the terminals. Since the channeling table is stored in one place, the central system is vulnerable to the loss of the channeling table. The central system uses the temporary identifier as the address for the mobile terminal in the subsequent downstream message data packets. The temporary identifier is preferred to the other pre-existing identifiers for reasons of safety and handling or handling. The requesting mobile terminal and the central system then exchange encryption information. After secure communications are established, the mobile terminal sends its secret identity number to the central system. The central system uses the secret identity number to access a stored profile for the mobile terminal that contains various subscriber information, in which billing information is included. The profile stored for the mobile terminal also contains an external address for a subscriber associated with the mobile terminal. The public identity number of the mobile terminal may be its external address. From time to time, external systems send message data packets having the external address of the mobile terminal to the central system, which uses the external address and its stored route table to obtain the temporary identifier of the mobile terminal. Then the central system transmits the message data packets in the downstream channel with the temporary identifier as the destination address. The mobile terminal captures and processes the data packets addressed to its temporary identifier. If a problem occurs in the central system, such as the loss of its routing table, which affects essentially continuous transmission in the downstream channel, some mobile terminals may interpret such problem as an error condition and try to register again with the central system. As these mobile terminals try to register again, the performance of the downstream channel will be reduced, which may cause additional problems in the central system. Even more mobile terminals will perceive an error condition. Inevitably, essentially the entire population of mobile terminals will be in contention for the upstream channel while attempting to re-register, so that the performance of the upstream channel will be degraded to a very low value. Consequently, the registration will take a fairly long time, and the performance of the message packet of the communication system during such re-registration will become unacceptably low. Thus, there is a need for a way to register essentially the entire terminal population, that is, to reconstruct the channeling table of the central system of temporary identifiers, after a disaster in the central system which has obliterated its channeling table.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention, attempts to register by a terminal using a containment protocol to communicate with a central system are controlled by transmitting a registration index from the central system to the terminal at specified time periods. , and when modifying the value of the registration index when the terminal should try to register with the central system. The use of the registration index prevents unnecessary registration attempts by the terminal.

A flag or mode indicator is transmitted from the central system to the terminal at predetermined time intervals and the value of the mode indicator is modified when the central system recovers from a disaster, in such a way that the terminal confirms the immediate attempts to register with the central system during disaster recovery. During disaster recovery, the terminal has the ability to associate itself with one of a plurality of sub-intervals. The central system transmits a sub-interval designator to the terminal at regular time periods during disaster recovery. The central system modifies the value of the sub-interval designator after a predetermined number of regular time periods. The flow of registration attempts by a terminal community is standardized from a situation where essentially the entire terminal community is holding to register after a disaster to a situation where the subsets of the community try to register in the respective sub-units. intervals after the disaster. It is not proposed that the invention be summarized in the present in its entirety. Rather, additional features, aspects and advantages of the invention are summarized in, or are apparent from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a diagram of the environment in which the present invention is applied; Figure 2 is a diagram of the communication channels between the central system and the mobile terminals; Figure 3 is a flow diagram of actions in the central system; Figure 4 is a flow diagram of actions in the mobile terminal; Figures 5A and 5B are timing diagrams illustrating traffic in the downstream channel; and Figures 6A and 6B are timing diagrams illustrating traffic in the upstream channel.

DETAILED DESCRIPTION Figure 1 illustrates an environment having mobile terminals 10-60 in wireless communication with central system 100, which is accessible to external systems 150, 160 via conventional communication techniques. The central system includes a general purpose processor, memory, storage and other conventional data processing equipment. Each mobile terminal includes a processor, memory and storage, not shown or further described since the particular components are not critical to the present invention. As shown in Figure 2, the central system 100 sends information to the mobile terminals 30-50 via the downstream channel 5, while the mobile terminals 30-50 send information to the central system 100 via the upstream channel 6. The mobile terminals 10, 20 and 60 communicate with the central system 100 in a similar manner and are not shown to simplify the drawings in Figure 2. According to the present technique, a mobile terminal has a definite way to determine if it is You must register with the central system after what can be a disaster. For instances where registration is appropriate, the mobile terminal has a procedure by which it can determine when to register. System control messages broadcast at regular intervals by the central system 100 in the downstream channel are incremented to include a registration index and a flag or mode flag. The registration index indicates a period of validity for temporary identifiers, that is, a class of batch number. When the channeling table of the central system is unusable, also referred to as loss, the registration index is incremented. Normally, the registration index is a few bits long to ensure that even if a sequence of system failures are grouped, the registration process takes place fully after the last system failure. In contrast, if the registration index is only one bit long, then it has the same value after a group of two faults, in which the channeling table is lost and a mobile terminal is not aware that its temporary identifier is invalid. All valid temporary identifiers have the same registration index. The mode flag indicates whether the registry for a community of mobile terminals that share a central system, also referred to as central system disaster recovery, is in progress. Figure 3 is a flow diagram illustrating the actions in the central system 100. Figure 4 is a flow diagram illustrating the actions in, for example, the mobile terminal 10. Figures 5A-5B, 6A, 6B are diagrams showing the traffic in the downstream and upstream channels for a specific example of the present disaster recovery record scheme. In step 310, it is assumed that the central system 100 is in normal operation, according to the functions of an intermediate mobile data system (MDIS) described in Cellular Digi such Packet Da ta System Specification, Relay 1.0, July 19, 1993, and Relay 1.1, January 19, 1995, available from the CDPD Industry Input Coordinator, 650 Town Center Drive, Suite 820, Costa Mesa, CA 92626, which is incorporated herein by reference. The central system 100 broadcasts, that is, transmits downstream channel 5, system control messages at regular intervals. Figure 5A shows the messages 551-555 of the system control broadcast regularly; it is seen that the system control message 555 includes the registration index 510A, which is illustrated in those of two-bit length and has a value of "01", and the indicator 515A of mode, illustrated as being of one length of a bit and that has a value of "0" corresponding to being out of adjustment. In step 320 of FIG. 3, the central system 100 broadcasts the registration index and the mode indicator, such as the registration index 510A and the mode indicator 515A. In step 330, the central system 100 determines whether its routing table is appropriately available; if so, the central system 100 returns to normal operation 310. Assume that the mobile terminal 10 operates in general in accordance with the functions of a mobile end system as described in Cellular Digi such Packet Data System Specification. The mobile terminal 10 enters the communications area of the central system 100, and in step 405 of figure 4, it is registered with the central system 100. As shown in Figure 6A, the registration begins with the mobile terminal 10 sending a registration request 610A, including its public identity number, in the present "717171" to the central system 100 via the upstream channel 6. The central system 100 responds to the registration request 610A by sending the registration response 530A, which includes a temporary identifier in the present "55682 to the mobile terminal 10 via the downstream channel 5. In the step 410 of figure 4, the mobile terminal 10 stores the temporary identifier "5568" and the registration index at the time of receipt of the temporary identifier.Figure 5A, the registration index in the broadcast message 552 has a value of "01." The block 600a of Figure 6A indicates a storage portion of the mobile terminal 10. After the registration is completed, in step 415 of Figure 4, the mobile terminal 10 goes into normal operation, for example, if the external system 150 wishes to sending a message to the mobile terminal 10 during normal operation (the central system 100 in the step 310 of figure 3 and the mobile terminal 10 in the step 415 of figure 4), the central system 100 receives the message from the external system 150 , and places the message in one or more message data packets, shown as the data packet 540A of the message in Figure 5A. Meanwhile the mobile terminal 10 listens to the packets broadcast on the downstream channel 6, recognizes its temporary identifier "5568" in the message data packet 540A, captures the message data packet 540A and processes them. In step 420 of FIG. 4, the mobile terminal 10 captures the broadcast register index and the mode indicator in each of the system control messages 553-555 broadcast. Since in step 425, the mobile terminal 10 determines that the value "01" of the broadcast registration index matches the value "01" of the stored registration index, the mobile terminal 10 returns to the normal operation 415. Even if the traffic on the downstream channel 5 was interrupted during this time, the mobile terminal 10 does not attempt to register again because the broadcast and stored registration rates coincide. It is seen that the use of the registration index prevents unnecessary registration. Suppose that a disaster has occurred in the central system 100, such that in step 330 of figure 3, it is found that the channeling table is unusable. The central system 100 now proceeds to the disaster recovery procedure in accordance with the present disaster recovery technique. During disaster recovery, the central system suspends the normal transmission of the message data packet and uses the downstream channel to transmit a sub-interval designator and register the mobile terminals. The sub-interval designator controls the number of mobile terminals that are allowed to attempt registration at any time. Suppose that the mobile terminal community is unknown and that each mobile terminal has a temporary identifier stored that is no longer valid. It will be appreciated that using only the least significant bit (LSB) of the invalid temporary identifier divides the mobile terminal community into two groups, the group (LSB = 0) and the group (LSB = 1). Similarly, by using the n least significant bits of the invalid temporary identifier, it divides the community of mobile terminals into 2n groups of essentially equal size, if the temporary identifiers were assigned randomly or sequentially. Instead of using its temporary identifier, each mobile terminal uses a random number or a different pre-stored number which is evenly distributed statistically over the mobile terminal community. Instead of using the least significant bits of its invalid temporary identifier, each mobile terminal could use the most significant bits; however, if the temporary identifiers are assigned sequentially, the most significant bits will not have a uniform statistical distribution and thus will not ensure that each group is essentially equal in size.

Let the record interval be divided into 2n subintervals. During the first subinterval, only the mobile terminals in the first group of the 2n groups of the mobile terminals are allowed to attempt the registration. During the second sub-interval, the mobile terminals in the second group and the mobile terminals as they are still not registered in the first group are allowed to attempt the registration. During the third sub-interval, the mobile terminals in the third group and the mobile terminals as yet unregistered in the second first group are allowed to attempt the registration. This procedure continues, so that during the last sub-interval, all mobile terminals, such as they are still without registration, are allowed to try to register. It will be appreciated that n and the temporal length of the sub-interval are questions of design choice. For example, as n increases, the number of mobile terminals trying to register in a sub-interval decreases, so that the efficiency of the upstream channel increases. It is important to appreciate that the number of mobile terminals that try to register during a sub-interval decreases with time, as a portion of them registers successfully. The sub-range designator functions as a blind address, since it selects an individually unknown but statistically manageable number of mobile terminals. The use of the sub-interval designator controls the registration flow of the mobile terminals. More specifically, the length of a subinterval is chosen depending on the contention protocol and the expected number of mobile terminals that are expected to service. Examples of contention protocols are segmented ALOHA, multiple carrier sense access with collision detection (CSMA / CD), multiple access with digital detection with collision detection (DSMA / CD). Important features of the contention protocol include retry numbers after an unsuccessful transmission, wait time before retry, and so on. In step 340, the central system 100 increments the registration index, for example, from "01" to "10" (addition in base 2) and adjusts the sub-interval to "-1". In step 350, the central system 100 increments the sub-interval to "0" and sets or adjusts a sub-interval timer to zero. In step 360, the central system 100 transmits the new registration index "10", transmits the mode indicator in a set condition, such as having a value of "1" and transmits the sub-interval "0". For purposes of this example, suppose that only the least significant digit (base 10) of the temporary identifier is used, such that there are ten sub-intervals. In other words, one tenth of the mobile terminals will be allowed to register during each sub-interval, plus the mobile terminals as they are still unregistered, if any, of the previous subintervals. In step 370, central system 100 receives and responds to registration requests from mobile terminals that have an invalid temporary identifier stored with a least significant digit of "0". At regular intervals, the central system 100 inspects whether the subinterval has been in advance for a sufficient time, as shown in step 380. If the subinterval has not reached its predetermined time duration, then steps 360-380 are repeated . If, in step 380, the central system 100 determines that the duration of the sub-interval has elapsed, then in step 390, the central system 100 determines whether all sub-ranges, in the present, all ten sub-intervals have been executed. If not, the central system 100 returns to step 350, increments the sub-interval, resets the sub-interval timer and repeats steps 360-380 as described generally above. After the central system 100 increases the registration index in step 340 and diffuses the increased registration index "10" in step 360, the mobile terminal 10 will find that the index "10" of the broadcast record does not match its register index "01" stored in step 425 of FIG. 4. Consequently, the mobile terminal 10 knows that its temporary identifier "5568" does not it is valid. In step 430, the mobile terminal 10 inspects whether the most recently broadcast mode indicator is set. It will be recalled that in step 360, the mode indicator was broadcast by the central system 100 upon being established. Because the indicator of the broadcast mode is set, the mobile terminal 10 knows that a disaster recovery is in progress. The use of the mode indicator allows the suspension of the normal registration procedure for the community of mobile terminals that are serviced by the central system. In step 435 of FIG. 4, the mobile terminal 10 captures the broadcast interval. In the first execution of step 360 of figure 3, the interval has a value of "0". In step 440 of FIG. 4, the mobile terminal 10 compares the broadcast interval "0" with the least significant digit of its invalid temporary identifier "8". Since the above value, "0" is less than the subsequent value "8", the mobile terminal 10 effectively knows that it is not allowed to try to obtain a valid temporary identifier. The mobile terminal 10 repeats steps 435 and 440. As shown in Fig. 5A, the central system 100 inevitably executes step 360 which results in the diffusion of the message 561 of the system control which includes the registration index 510B with a value of "10" (base 2), the mode indicator 515B with a value of "1" (base 2), that is, the mode indicator is set, the subinterval indicator 520B with a value of "1" based 2) and the 525B sub-interval designator with a value of "5" (base 10). For convenience, the sub-interval indicator is transmitted in a system control message. When the sub-interval is not set or has a value of "0" as shown in field 52OA of system control message 551, it indicates that a sub-range designator is not transmitted. In contrast, when the subinterval indicator is set or has a value of "1" as shown in field 520B of message 561 of the system control, it indicates that a subinterval designator is also transmitted, such as the 525B subinterval designator . It is described that the sub-interval indicator has a length of one bit, which is consistent with the sub-interval designator having a predetermined length. Alternatively, if the bit length of the subinterval is determined dynamically, the length of the subinterval in bit must also be broadcasted. That is, the granularity of a sub-interval may be predetermined or dynamically determined as a function of for example the number of mobile terminals in the channeling table before the channeling table is lost. The dynamic determination of the length of a subinterval increases the efficiency and complexity of the recovery mechanism. By the aforementioned process, the central system 100 also generates and broadcasts system control messages 562-573, shown in Figures 5A-5B. After the subsequent executions of steps 435-440, the mobile terminal 10 captures the system control messages 562-567 and determines that it should not attempt the registration yet. Inevitably, in the execution of step 435, the mobile terminal 10 captures the broadcast system control message 568, shown in FIG. 6B, which has an interval value of "8". In step 440, the mobile terminal 10 finds that the sub-interval "8" broadcast is equal to the least significant digit of its invalid temporary identifier "8", such that the mobile terminal 10 proceeds to step 450 and register During the registration of step 450, the mobile terminal 10 sends the registration request 610B, shown in Figure 6B, to central system 100 via channel 6 upstream. The central system 100 responds to the registration request 610B by sending the registration response 530B, shown in Figure 5B, which includes the temporary identifier "2394" to the mobile terminal 10 via the downstream channel 5. In step 455 of figure 4, the mobile terminal stores the new temporary identifier "2394" and the registration index "10" at the time of receipt of the temporary identifier. Block 600B in Fig. 6B indicates a storage portion of mobile terminal 10 after step 455 of Fig. 4. In step 460, mobile terminal 10 captures the spread mode indicator in system control message 570 of Figure 5B. In step 465, the mobile terminal 10 determines that the mode indicator is set, which means that a disaster recovery is still in progress and such that the mobile terminal 10 should not attempt to send packets of the message data. The mobile terminal 10 repeats steps 460-465 for the system control messages 571-573. At some time after the broadcasting of the control message 573 of the system of FIG. 5B, the central system 100 executes the step 390 of FIG. 4, and determines that all the sub-intervals have elapsed, that is, the process of Post-disaster registration is over. At this point, the central system 100 has a valid routing table for the mobile terminals in communication therewith. In this manner, the central system 100 returns to normal operation in step 310. In the next execution of step 320, the central system 100 broadcasts the message 574 of the system control of FIG. 5B. If a message for the mobile terminal 10 arrives from the external system 160, the central system 100 places the message in the message data packet 540B, which is seen to have the new temporary identifier "2394" for the mobile terminal 10 and transmits the message. 540B packet of message data on channel 5 downstream. In the next execution of step 320, the central system 100 broadcasts the message 575 of the control message of the system. Immediately after the message 573 of the system control is broadcast, in the execution of steps 460-465, the mobile terminal 10 determines that the mode indicator is no longer set and returns to normal operation in step 415. During the normal operation, the mobile terminal 10 captures and processes the message data packet 540B in a conventional manner. As a further example illustrating the operation of the technique of the invention, suppose that after capturing and processing the control message 555 of the system in Figure 5A, the mobile terminal 10 enters a standby mode of power or for some other reason stops checking channel 5 downstream after a while. Assume further that the mobile terminal 10 then awakens or re-listens to the downstream channel 5 and in an execution of the step 420, captures the control message 575 of the broadcast system. In the next execution of step 425, the mobile terminal 10 determines that the broadcast record index "10" captured from the message 575, does not match its index "01" of the stored record (shown in block 600A of figure 6A) . In step 430, the mobile terminal 10 determines that the mode indicator in the message 575 was not set, such that the mobile terminal 10 effectively knows that a disaster recovery is not in progress. Then, the mobile terminal 10 proceeds to step 405 to obtain a new temporary identifier. An advantage of the scheme described above is that a mobile terminal can determine if its temporary identifier is valid, and in this way will endorse unnecessary registration even if there is a problem. Another advantage of the scheme described above is that only a subset of mobile terminals attempt to register at any time after a disaster, thereby avoiding harmful congestion in the upstream channel. An additional advantage of the scheme described above is that the duration of the disaster recovery registration period is substantially known in advance. Still another advantage of the scheme described above, is that coordination between individual mobile terminals is not required. Another advantage of the scheme described above is that the actual registration process for a specific mobile terminal after a disaster is the same as during normal operation, which avoids an increase in the complexity of the mobile terminal and the central system. The new mobile terminals that enter the area that is serviced by the central system while it has a recovery from the disaster is in progress allowing them to immediately join the registration process, that is, to consider themselves as mobile terminals that are still unregistered from a previous sub-interval. The result is that a new mobile terminal quickly obtains a registration number, then enters a standby mode of energy until disaster recovery is complete, which saves battery power in the mobile terminal. Normally, when a communication system provides a standby power mode for its mobile terminals, there is a system control message broadcast regularly that "wakes up" mobile terminals that have pending messages. In a modification, the new mobile terminals must wait until disaster recovery is complete before registering. A disadvantage of this scheme is that when disaster recovery is complete, which can be indicated by a diffusion of the central system that is routed globally to all mobile terminals, the group of new mobile terminals try all to register at approximately the same time , which can congest the communication channel.

Alternatively, a new mobile terminal selects a random number or other pre-stored number and uses the selected number instead of an invalid temporary identifier. This promotes the statistical dispersion of the new mobile terminals, but does not have the advantage of saving energy by maximizing the time in the standby mode. In another modality, the profiles associated with certain mobile terminals are designated by priority services. After a disaster, as soon as such mobile terminals are registered, the central system will transmit message data packets between external systems and such mobile terminals, while mobile terminals that do not have priority continue with post-disaster registration. This is useful for essential services such as ambulances, emergency crews and so on. In one modification, for priority mobile terminals, the central system allocates temporary identifiers having their n least significant bits equal to a predetermined value and this predetermined value is the first group allowed to register during the first subinterval after a disaster. This mode ensures that priority mobile terminals have the shortest service interruption. For example, the central system reserves temporary identifiers that end in "00" for priority mobile terminals. During a normal registration, the central system does not assign temporary identifiers that end in "00" after having access to the profile of a newly registered mobile terminal and determine that it has priority status, the central system sends a revised temporary identifier that ends in "00" to the priority mobile terminal. The embodiments described above are concerned with a configuration having a central system serving a mobile terminal community. It will be appreciated that the central system may correspond to a radio cell in a cellular system and that the disaster recovery registration scheme described above facilitates the orderly registration of subsets of the mobile terminals in a cell without any knowledge of which mobile terminals are they find in the cell. Since the identities of mobile terminals in a cell at any time are not predictable, it is important that the disaster recovery registration protocol works without such identities and without depending on the control messages addressed to the mobile terminals identified. Although illustrative embodiments of the present invention and various modifications thereof have been described in detail herein with reference to the accompanying drawings, it will be understood that the invention is not limited to these precise embodiments, and the modifications described and that various changes and Further modifications may be made thereto by those skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims. It is noted that, in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (31)

1. Claims 1. A method for controlling an attempt to register by a terminal, by using a containment protocol to communicate with a central system, the method is characterized in that it comprises the steps of: transmitting a registration index from the central system to the terminal to specified time periods, and modify the value of the registration index when the terminal should try to register with the central system. The method according to claim 1, characterized in that the central system has a channeling table and the register index value is modified when the channeling table is unusable. 3. The method of compliance with the claim 1 characterized in that the registration index is modified after a failure in the central system and where the registration index allows a sequence of system failures to be distinguished respectively. 4. The method of compliance with the claim 3, characterized in that the registration index has a length of at least two bits. The method according to claim 1, characterized in that the terminal obtains an identifier during the registration and stores the identifier and the index value of the register at the time in which the identifier is obtained. The method according to claim 5, characterized in that the terminal rushes the stored register index value and the value of the transmitted register index and determines that it should attempt to register with the central system when the stored and transmitted values of the record does not match 7. The method of compliance with the claim 5, characterized in that the terminal compares the value of the stored registration index and the value of the transmitted registration index and determines that it should be countersigned to attempt to register with the central system when the stored values transmitted from the registration index coincide. The method according to claim 1, characterized in that it further comprises the steps of: transmitting a mode indicator of the central system to the terminal at predetermined time intervals and modifying the value of the mode indicator when the central system is recovered from a disaster in such a way that the terminal is endorsed of immediately trying to register with the central system. 9. The method according to claim 8, characterized in that when the terminal determines that the registration index has been modified and that the mode indicator has not yet been modified, the terminal immediately attempts to register. The method according to claim 8, characterized in that when the terminal determines that the registration index has been modified and the mode indicator has been modified, the terminal stops trying to register immediately. The method according to claim 8, characterized in that the terminal has the ability to associate itself with one of a plurality of subintervals and further comprises the steps of: transmitting a sub-interval designator of the central system to the terminal at specified time intervals when the central system recovers from a disaster and modify the value of the subinterval designator after a predetermined number of the specified time intervals. The method according to claim 11, characterized in that the terminal has a stored value, the terminal compares the stored value with the transmitted sub-interval designator and the terminal determines that it must be associated by itself with a sub-slot in base to the comparison. The method according to claim 12, characterized in that the sub-range designator designates a specified number of least significant bits of the stored value. 14. The method according to claim 12, characterized in that the stored value is an identifier obtained during the registration. 15. A method for controlling a terminal communicating with a central system by using a containment protocol when the central system recovers from a disaster, the method is characterized in that it comprises the steps of: transmitting a mode indicator of the central system to the terminal to regular time periods and modify the value of the mode indicator when the central system recovers from a disaster. The method according to claim 15, characterized in that the central system suspends the transmission of message data packets from an external system to the terminal when the central system recovers from a disaster. The method according to claim 15, characterized in that the terminal suspends the transmission of message data packets for a system external to the central system when the central system recovers from a disaster. The method according to claim 15, characterized in that the terminal has the ability to associate itself with one of a plurality of subintervals and further comprises the steps of: transmitting a sub-interval designator of the central system to the terminal at specified time intervals when the central system recovers from a disaster and modifying the value of the sub-interval designator after a predetermined number of the specified time intervals. 19. The method according to claim 18, characterized in that the terminal has a stored value, the terminal compares the stored value with the designator of transmitted sub-intervals and the terminal determines that it must be associated by itself with a sub-interval in base to the comparison. 20. The method of compliance with the claim 19, characterized in that the sub-range designator designates a specified number of least significant bits of the stored value. 21. The method according to claim 19, characterized in that the stored value is an identifier obtained during the registration. 22. A method for associating a terminal with one of a plurality of sub-intervals, the terminal uses a containment protocol to communicate with a central system, the method is characterized in that it comprises the steps of: transmitting a sub-interval designator of the central system to the terminal to regular time periods and modify the value of the sub-interval designator after a number of the regular time periods. 23. The method according to the claim 22, characterized in that the terminal has a stored value, the terminal compares the stored value with the transmitted sub-interval designator and the terminal determines that it must be associated by itself with a sub-interval based on the comparison. 24. The method of compliance with the claim 23, characterized in that the sub-range designator designates a specified number of least significant bits of the stored value. 25. The method of compliance with the claim 24, characterized in that the stored value is an identifier obtained during registration. 26. The method according to claim 22, characterized in that the number of the regular time periods is predetermined. 27. The method according to claim 22, characterized in that the number of the regular time periods is determined dynamically. 28. The method according to claim 22, characterized in that the number of regular time periods depends on the characteristics of the containment protocol. 29. The method according to claim 22, characterized in that a plurality of terminals are serviced by the central system and the number of regular time periods depends on the number of terminals serviced by the central system. 30. The method according to claim 22, characterized in that the number of sub-intervals depends on the characteristics of the containment protocol. 31. The method according to claim 22, characterized in that a plurality of terminals are serviced by the central system and the number of subintervals depends on the number of terminals that are serviced by the central system. SUMMARY OF THE INVENTION Recording attempts are described by a terminal (10, 20, 30, 40, 50, 60) that uses a containment protocol to communicate with a central system (100) that are controlled by transmitting a registration index ( 510) from the central system to the terminal at specified time periods and modify the value of the registration index when the terminal should attempt to register with the central system. A mode indicator (515) is transmitted from the central system to the terminal at predetermined time intervals and the value of the mode indicator is modified when the central system recovers from a disaster, such that the terminal stops trying to register immediately with the central system. During disaster recovery, the terminal has the ability to associate itself with one of a plurality of subintervals. The central system transmits a sub-interval designator (520) to the terminal at regular time periods during disaster recovery. The central system modifies the value of the subinterval designator after a predetermined number of regular time periods. The flow of registration attempts by a community of terminals becomes uniform from a situation where essentially the entire terminal community is content to register after a disaster to a situation where the sub-sets of the community attempt to register in respective sub. -intervals after the disaster.