为什么BFD发包间隔比设置最小发包间隔还要小短

<HKBCP214>dis bfd session discriminator 3901

       Local Discr: 3901                 Remote Discr: 16514

         Source IP: 172.20.162.1       Destination IP: 124.217.129.34

     Session State: Up                      Interface: N/A

      Min Tx Inter: 1000ms               Act Tx Inter: 1000ms

      Min Rx Inter: 1000ms               Detect Inter: 15000ms

          Rx Count: 418991                   Tx Count: 478661

      Connect Type: Indirect           Running Up for: 116:23:21

         Hold Time: 14050ms                 Auth mode: None

       Detect Mode: Async                Chassis/Slot: 2/0

          Protocol: BGP            

           Version: 1              

         Diag Info: No Diagnostic   

例如，最小发包间隔是1秒，但是有时候发送时间间隔比较1秒还小

正常的，BFD实际发包时间，RFC5880规定按照配置值向下偏差0%~25%：

6.8.7.  Transmitting BFD Control Packets

   With the exceptions listed in the remainder of this section, a system

   MUST NOT transmit BFD Control packets at an interval less than the

   larger of bfd.DesiredMinTxInterval and bfd.RemoteMinRxInterval, less

   applied jitter (see below).  In other words, the system reporting the

   slower rate determines the transmission rate.

  The periodic transmission of BFD Control packets MUST be jittered on

   a per-packet basis by up to 25%, that is, the interval MUST be

   reduced by a random value of 0 to 25%, in order to avoid self-

   synchronization with other systems on the same subnetwork.