SGSN与BSC的PFC协商流程，是否存在一个参数控制这个流程

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重试次数和等待时间都有的。有关于等待对方报文的等待时间，BSS侧是T6计时器（发送DOWNLOAD-BSS-PFC PDU 启动 ，收到CREATE-BSS-PFC PDU后停止），SGSN侧是T7计时器（发送CREATE-BSS-PFC-ACK PDU启动，收到CREATE-BSS-PFC-NACK PDU停止）。

SGSN的重试次数是：“If a CREATE-BSS-PFC-ACK or CREATE-BSS-PFC-NACK PDU is not received in response to a CREATE-BSS-PFC PDU within T7 seconds, then the CREATE-BSS-PFC PDU shall be repeated a maximum of CREATE-BSS-PFC-RETRIES attempts. After CREATE-BSS-PFC-RETRIES+1 attempts the procedure is stopped and the O&M is informed.”

也就是SGSN上有一个叫做CREATE-BSS-PFC-RETRIES的重传次数定义的。

BSS上也有一个，如下“If a CREATE-BSS-PFC PDU is not received for a DOWNLOAD-BSS-PFC PDU within T6 seconds, then the DOWNLOAD-BSS-PFC PDU shall be repeated a maximum of DOWNLOAD-BSS-PFC-RETRIES attempts. After DOWNLOAD-BSS-PFC-RETRIES + 1 attempts the procedure is stopped and the O&M system is informed. If a BSS PFC is not received then the BSS shall handle uplink and downlink transfers according to a best-effort default aggregate BSS QoS profile.”

叫做DOWNLOAD-BSS-PFC-RETRIES计时器。

但这里的问题是SGSN为什么要重发BSS-PFC PDU？因为上面的计时器是指收不到BSS的BSS-PFC-ACK PDU来重发的，本例是已经收到了，所以最好有抓包看看，是不是协商有什么问题。