M2PA: resynchronization of sequence numbers after PO

Hi,

M2PA RFC 4165 state the following:

"When the local processor outage condition ends, M2PA SHALL send a
   Link Status Processor Recovered message to its peer on the User Data
   stream.  This message is used to signal the end of the processor
   outage condition, instead of an MSU or FISU, as is used in MTP2.  The

   BSN in the Link Status Processor Recovered message is set to the FSN
   of the last User Data message received (and not discarded) from the
   peer M2PA.  M2PA SHALL cease transmitting User Data messages after
   sending the Link Status Processor Recovered message, until it has
   received the Link Status Ready message (see below).

   Upon receiving the Link Status Processor Recovered message, the M2PA
   in RPO SHALL respond with a Link Status Ready message on the User
   Data stream.  The BSN in the Link Status Ready message is set to the
   FSN of the last User Data message received (and not discarded) from
   the peer M2PA.

   Upon receiving the Link Status Ready message, the M2PA formerly in
   LPO SHALL respond with a Link Status Ready message on the User Data
   stream.  The BSN in the Link Status Ready message is set to the FSN
   of the last User Data message received (and not discarded) from the
   peer M2PA.

   M2PA (at both the LPO and RPO ends) uses the BSN value in the
   received Link Status Ready message to resynchronize its sequence
   numbers, if this is required by MTP2.  M2PA SHALL NOT resume
   transmitting User Data messages until it has sent the Link Status
   Ready message.

Could you please explain why the second Link Status Ready (stream 1) is
needed?
thanks!
Kind regards, Dario



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