RE: What is FSN and BSN values of the Link Status Massages in M2PA

Hello Bibhuti,

>Q1 What will be its value for Link Status messages?

The BSN is the FSN of the last non-empty user data message to be acknowledged
as received. If no non-empty user data messages has been received, then the
BSN is the initial sequence number minus one. The FSN is the M2PA sequence
number of the last non-empty user data message sent. If no non-empty user data
message has been sent, then the FSN is the initial sequence number minus one. 
Note that except for the case of synchronization after processor recovery, the
sequence numbers of Link Status messages are ignored by the receiver.

>Q2 While retriving the FSN and BSN of these messages are lost and MTP3 transfers
>using new alternate M2PA layer or the differentSCTP Stream of same M2PA layer as
>multiple User data streams may be available in underlying SCTP Association?

I am not sure I understand the question, but I'll attempt an answer. If MTP3
retrieves MSUs from an M2PA signaling link instance and re-routes the MSUs via
another M2PA signaling link instance, then the MSUs will become new M2PA user data
messages having sequence numbers appropriate for the new M2PA signaling link. The
situation would be similar if the new link was ATM or E1 or T1, rather than M2PA.

Regards,

Jeff
________________________________________
From: Bibhuti Bhusan Tosh [mailto:[email protected]] 
Sent: Monday, May 15, 2006 6:20 AM
To: [email protected]
Subject: [Sigtran] What is FSN and BSN values of the Link Status Massages inM2PA

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 differentSCTP Stream of same M2PA layer as multiple User data streams may be available in underlying SCTP Association?
 
Regards,
Bibhuti