Subject: [Sigtran] What is FSN and BSN values of the Link Status Massages in M2PA

From: "Bibhuti Bhusan Tosh" <[email-masked]>
Date: Mon, 15 May 2006 15:50:27 +0530

Hi All

Kindly clarify my following question on M2PA.

Q1.    As per RFC 4165. the M2PA common header contains only the FSN and BSN values. 

2.2.1.  Backward Sequence Number (BSN)

     This is the FSN of the message last received from the peer.

 2.2.2.  Forward Sequence Number (FSN) 

  This is the M2PA sequence number of the User Data message being sent. 

  The FSN and BSN values range from 0 to 16,777,215.

 So the FSN and BSN values are updated in User Data Messages only. What will be its value for Link Status messages?

Q2. M2PA RfC 4165 says that The association SHALL contain two streams in each direction.Stream 0 is designated for Link Status messages.  Stream 1 is designated for User Data messages, as well as Link Status messages that must remain in sequence with the User Data messages. During ChangeOver The MTP3 retrivses the data from M2PA and transfers them using alternate links. 

My Question is that While retriving the FSN and BSN of these messages are lost and MTP3 transfers using new alternate M2PA layer or the different SCTP Stream of same M2PA layer as multiple User data streams may be available in underlying SCTP Association?

Regards,
Bibhuti

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