Request ID [32 Bit]

• The Request ID field shall consist of a Client ID field [16 bits] and a Session ID field [16 bits].
  Request ID 字段應由Client ID字段[16位]和Session ID 字段[16位]組成。
• The Client ID is not used for Service Discovery, The Client ID shall be set statically to 0x0000.
  Client ID不用于Service Discovery ，Client ID 應靜態設置為0x0000。
• The Session ID is used to detect the reboot or restart of other Service Discovery instances in the vehicle in order to repair the local state of the Service Discovery module.
  Session ID用于檢測車輛中其他服務發現實例的重新引導或重新啟動，以修復服務發現模塊的本地狀態。
• After initialization of the Service Discovery Module, the Session ID for messages sent by the local ECU shall be 0x0001.
  Service Discovery模塊初始化后，本地ECU發送的消息的Session ID應為0x0001。
• The Session ID shall be incremented and stored separately for multicast and every single unicast communication partner every time SoAd_IfTransmit() is called.
  每次調用SoAd_IfTransmit()時，對于組播和單播通信伙伴，Session ID都會單獨增加并單獨存儲。
• Every time, the Session ID wraps around, the Session ID shall restart with the value 0x0001.
  每次Session ID循環， Session ID需要從0x0001重新開始。

Note注意:

• This means that the first SD message sent out to the multicast address has Session ID 0x0001 as well as the first SD message sent out to any unicast communication partner has the Session ID 0x0001 as well.
  這意味著發送到多播地址的第一條SD消息具有會話ID 0x0001，并且發送給任何單播通信伙伴的第一條SD消息也具有會話ID 0x0001。
• Wrap around means that the current value of the Session ID is the max value (0xFFFF) and the next increment would mean the counter must start again.
  循環意味著會話ID的當前值是最大值（0xFFFF），再增加一次session意味著計數器必須重新啟動。