TS24.008 4.7.2.2中有一句话涉及T3312的启动： If the initial READYtimer value is zero, the timer T3312 is reset and started with its initialvalue, [url=]when the ROUTING AREA UPDATE REQUEST message is transmitted.中initial READY timer value指的是READY timer什么时候的值？还有为何要等到ROUTING AREA UPDATE REQUEST消息发出之后才重启T3312呢？[/url]
先放上个完整的版本"
In A/Gb mode, the timer T3312 is reset and started with its initial value, when the READY timer is stopped or expires. The timer T3312 is stopped and shall be set to its initial value for the next start when the READY timer is started. If after a READY timer negotiation the READY timer value is set to zero, timer T3312 is reset and started with its initial value. If the initial READY timer value is zero, the timer T3312 is reset and started with its initial value, when the ROUTING AREA UPDATE REQUEST message is transmitted."
蓝色的部分是你的问题。
我说下我的理解。
Initial Ready Timer应该是MS和SGSN在附着过程中进行ready timer协商（ready timer是允许协商的，但一般都没有开启）后得到的双方认可的一个值。这个值将用于后续的MM状态管理。所以叫Initial Ready Timer，并且允许在后续的附着流程中继续协商。
蓝色的部分实际上是两句话，第一句是If the initial READY timer value is zero, the timer T3312 is reset .第二句是started with its initial value, when the ROUTING AREA UPDATE REQUEST message is transmitted."两者是独立的关系。如果你单看第二句你会发现一点都不矛盾。第二句的意思就是当RAU Request消息发送的时候，T3312将按照初始值（例如30分钟）开始启动，这个启动start和前面的reset是两个场景，前面的reset产生条件是if the initial READY timer value is zero.