-REQ/RSP message. If the MS transmits a HO-IND message including the BS-ID of any BS other than the base stations which have already indicated support for seamless handover, then seamless handover is not applied to that BS. The MOB_BSHO-REQ or MOB_BSHO-RSP message may contain a specific action time. If a value for the action time is specified, pre-assigned CIDs are valid at the target BS after the expiration of the action time. A value of zero indicates that the pre-assigned CIDs are already valid and MS may initiate seamless handover at any time. During seamless handover, the target BS may allocate downlink and uplink resources for the MS before the RNG-REQ/RSP messaging, as shown in Figure 6-13. During seamless HO, the MS is required to initiate the RNG-REQ/RSP message exchange by sending a RNG-REQ message before the deadline specified by the Seamless HO Ranging Initiation Deadline parameter included in the MOB_BSHO-REQ/RSP message during handover preparation. The time is measured from the instant where the MOB_BSHO-REQ/RSP message is transmitted. If the target BS does not receive a RNG-REQ message from the MS within the deadline defined by the Seamless HO Ranging Initiation Deadline parameter, the target BS assumes that the seamless handover has failed and stops allocating bandwidth to the MS. The MS would assume the seamless handover has failed if it does not transmit the RNG-REQ message before the deadline. If the MS transmits RNG-REQ prior to the deadline, it may still consider the handover as failed, if it does not receive a RNG-RSP within a certain period after the last transmission or re-transmission of RNG- REQ that was performed within the permissible time. When the MS considers the seamless handover has failed, it invalidates the pre-assigned CIDs. In all cases, even when the RNG-REQ/ RSP message exchange has been initiated before the deadline, the seamless handover can fail if the RNG-REQ/RSP procedure does not succeed. When data packets are exchanged before the RNG- REQ/RSP procedures are completed,