Subject: [Sigtran] M2PA: Revised section 3

From: Tom George <[email-masked]>
Date: Fri, 07 Mar 2003 21:13:45 -0600

3.  M2PA Link State Control

The M2PA link moves from one state to another in response to various
events.  The events that may result in a change of state include:

   - MTP3 primitive requests

   - SCTP notifications

   - Receipt of Link Status messages from the peer M2PA

   - Expiration of certain timers

Figure 7 illustrates state changes together with the causing events.
Note that some of the error conditions are not shown in the state
diagram.

Following is a list of the M2PA Link States and a description of each.

   POWER OFF - State of the link during power-up initialization.

   OUT OF SERVICE (OOS) - Out of service. Power-up initialization is
   complete.

   INITIAL ALIGNMENT - Alignment in Progress. M2PA is attempting to
   exchange Link Status Alignment messages with its peer.

   PROVING - M2PA is sending Link Status Proving messages to its peer.

   ALIGNED READY - Proving is complete. M2PA is waiting until peer
   completes proving.

   IN SERVICE (INS) - In service. Link is ready for traffic.

   ALIGNED NOT READY - A local processor outage condition began before
   the alignment and proving procedure was completed.

   PROCESSOR OUTAGE - A local processor outage condition began while
   the link was in service.

                    +-----------+                                       
                    |   POWER   |                                       
                    |    OFF    |                                       
                    +-----------+                                       
                          |                                             
                          | Power On                                    
                          |                                             
        Flush Buffers     |  +-------------------------+                
        OR Retrieval      |  |                         |                
               +-------+  |  |                         |                
               |       |  V  V                         |                
               |    +-----------+                      |                
               +--->|  OUT OF   |                      |                
  +---------------->|  SERVICE  |<--+                  |                
  |                 +-----------+   | Link Configured  |                
  |                       |   |     | (Associate)      |                
  |                       |   +-----+                  |                
  |                       |                            |                
  |                       | MTP3 Start                 |                
  |                       |                            |                
  |                       |   +-----+                  |                
  |                       |   |     | LPO/LPR          |                
  |                       V   V     |                  |                
  |                 +-----------+   |                  |                
  |                 |  INITIAL  |---+                  |                
  +<----------------| ALIGNMENT |--------------------->+                
  |      MTP3 Stop  +-----------+     SCTP Comm Error  |                
  |   OR T2 Expiry        |        OR SCTP Comm Lost   |                
  |                       |                            |
  |                       |                            |
  |                       | Receive LS Align           |
  |                       | OR Receive LS Proving      |
  |                       |                            |
  |                       |   +----+                   |                
  |                       |   |    | LPO/LPR           |                
  |                       |   |    | OR Receive LS     |                
  |                       |   |    |    Proving        |                
  |                       |   |    | OR Receive LS     |                
  |                       |   |    |    Ready          |                
  |                       |   |    | OR Receive LS PO  |                
  |                       |   |    |                   |                
  |                       V   V    |                   |                
  |                 +-----------+  |                   |
  |                 |  PROVING  |--+                   |
  |<----------------|           |--------------------->+
  |      MTP3 Stop  +-----------+     SCTP Comm Error  |
  |   OR T3 Expiry        |  |     OR SCTP Comm Lost   |
  |   OR Receive LS OOS   |  |                         |
  |                       |  +-------------------------|--------+
  |                       |     T4 Expiry (LPO)        |        |      
  |                       |     Send LS PO             |        |      
  |                       |                            |        |      
  |                       | T4 Expiry                  |        |      
  |                       | Send LS Ready              |        |      
  |                       |                            |        |      
  |                       |                            |        |      
  |                       V           SCTP Comm Error  |        V      
  |                 +-----------+  OR SCTP Comm Lost   |  +-----------+
  |                 |  ALIGNED  |--------------------->+  |  ALIGNED  |
  +<----------------|   READY   |<----------------------->| NOT READY |
  |      MTP3 Stop  +-----------+     LPO/LPR             +-----------+
  |   OR T1 Expiry        |        OR Receive LS PO/PR       |       |
  |   OR Receive LS OOS   |                                  |   T1  | 
  |   OR Receive LS Align | Receive LS Ready      Receive    | Expiry|
  |                       | OR Receive User Data    LS Ready | OR Rcv|
  |                       |                                  |    LS |
  |                       |                                  |  Align|
  |                       |                                  |       |
  |                       V                                  V       |
  |                 +-----------+                      +-----------+ |
  |                 |    IN     |<-------------------->| PROCESSOR | |
  |                 |  SERVICE  |     LPO/LPR          |   OUTAGE  | |
  |                 +-----------+  OR Receive LS PO/PR +-----------+ |
  |                       |                                  |       |
  |                       |                                  |       |
  |     MTP3 Stop         |                MTP3 Stop         |       |
  |  OR Receive LS OOS    |             OR Receive LS OOS    |       |
  |  OR SCTP Comm Error   |             OR SCTP Comm Error   |       |
  |  OR SCTP Comm Lost    |             OR SCTP Comm Lost    |       |
  |  OR T6 Expiry         |             OR M2PA Link Failure |       |
  |  OR T7 Expiry         |             OR Receive LS Align  |       |
  |  OR M2PA Link Failure |                                  |       |
  |  OR Receive LS Align  |                                  |       | 
  |                       V                                  V       V
 
+<----------------------+<---------------------------------+-------+      

                Figure 7. M2PA Link State Transition Diagram

Figure 8 illustrates state changes in the M2PA management of the SCTP
association together with the causing events.  Note that some of the
error conditions are not shown in the state diagram.

Following is a list of the M2PA Association States and a description
of each.

IDLE - State of the association during power-up initialization.

ASSOCIATE - M2PA is attempting to establish an SCTP association.

ESTABLISHED - SCTP association is established. 

                      +-----------+
                      |   IDLE    |
                      +-----------+
                            |
                            | Associate
                            | (Issue SCTP associate)
                            |
                            |   +----------------------+
                            |   |         (Issue SCTP  |
                            V   V          associate)  |
                      +-----------+                    |
                      | ASSOCIATE |------------------->+
                      +-----------+    SCTP Comm Error |
                            |                          |
                            |                          |
                            | SCTP Comm Up             |
                            |                          |
                            V                          |
                      +-------------+                  |
                      | ESTABLISHED |----------------->+
                      +-------------+   SCTP Comm Error
                                     OR SCTP Comm Lost

                Figure 8. M2PA Association State Transition Diagram

-- 
* Tom George       PB7-24001 (near B-21)      [email-masked]  *
* 972-519-3168   Intranet:  http://www.ssd.usa.alcatel.com/~tgeorge/  *
* Alcatel;  3400 West Plano Pkwy,  MS PB7-SWPRO;  Plano, Texas 75075  *
* I actively disclaim speaking for Alcatel USA, Inc. I do not purport *
* to advertise or represent its position,  operations, or activities. *
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---

From: "Subhashini" <[email-masked]>
Date: Tue, 11 Mar 2003 12:29:51 -0600

The following are my doubts as per the new changes.
 1. Once the SCTP communication is UP, why to send LS OOS to peer. Peer can
get this message only in Out Of Service or in Initial Alignment states,
since from version 0.6 on wards, SCTP communication is not closed in any
cases. In Fig 7, the action of LS OOS in these states is missing.

2. In Fig 7, processing of LS OOS in Initial Alignment is missing.

Please clarify.

thanks,

Subhashini ...

---

From: Tom George <[email-masked]>
Date: Tue, 11 Mar 2003 13:49:15 -0600

> since from version 0.6 on wards, SCTP communication is not closed in any

LS OOS is sent to make sure that both ends are in the same state. This
is similar to MTP2. 

> 2. In Fig 7, processing of LS OOS in Initial Alignment is missing.

I added those to Figure 7. In both cases (Initial Alignment and OOS
states), receipt of LS OOS causes no state transition.

Also, there was no reason to have 2 "loops" on the OOS state. Here is
the new version (as of now):

                    +-----------+                                       
                    |   POWER   |                                       
                    |    OFF    |                                       
                    +-----------+                                       
                          |                                             
                          | Power On                                    
                          |                                             
                          |  +-------------------------+                
                          |  |                         |                
                          |  | +---+                   | 
                          |  | |   | Link Configured   |
                          |  | |   |   (Associate)     |
                          |  | |   | OR Receive        |
                          |  | |   |    LS OOS         |
                          V  V V   | OR Flush Buffers  |
                    +-----------+  | OR Retrieval      | 
                    |  OUT OF   |--+                   |
  +---------------->|  SERVICE  |                      |
  |                 +-----------+                      |
  |                       |                            |
  |                       |                            |                
  |                       |                            |                
  |                       | MTP3 Start                 |                
  |                       |                            |                
  |                       |   +----+                   |                
  |                       |   |    | LPO/LPR           |                
  |                       V   V    | OR Receive        |                
  |                 +-----------+  |    LS OOS         |                
  |                 |  INITIAL  |--+                   |                
  +<----------------| ALIGNMENT |--------------------->+                
  |      MTP3 Stop  +-----------+     SCTP Comm Error  |                
  |   OR T2 Expiry        |        OR SCTP Comm Lost   |                
etc.

> Subhashini ...
  [...]

---

From: Andrew Booth <[email-masked]>
Date: Wed, 12 Mar 2003 12:44:33 -0500

Hi Tom,

Comment below.

>   - Receipt of Link Status messages from the peer M2PA
User Data can also trigger a state transition. Should we just say 
"Receipt of messages from the peer M2PA"?

Andrew

>[snip]

---

From: Tom George <[email-masked]>
Date: Wed, 12 Mar 2003 17:01:42 -0600

Andrew,

That looks right. I will make the change.

tomG.

---

From: "Subhashini" <[email-masked]>
Date: Thu, 13 Mar 2003 13:00:58 -0600

The following are our doubts as per the revised sections:
  1.. In "Proving" state, when T4 expires and LS Ready/User Data is already
received, state can be changed to INSERVICE.
  2.. In "Aligned Ready" state, when LS PO is received, go to "Processor
Outage", instead of "Aligned Not Ready". (Since, LS PO is sent only after
proving ends. This can be treated as LS Ready.)
  3.. Processing of STOP command in "Aligned Not Ready" and "Processor
Outage" is missing in Fig.7.
  4.. When T1 expires in "Aligned Not Ready" state, go to OOS, not to
"Processor Outage" state.
  5.. As per section 4.1.4, when LS PO ended is received, the notification
to MTP3 is done, only when it is in INSERVICE state. But, when LS PO is
received, state is not expected to be INSERVICE to notify it to MTP3. Is
there any reason for this?
  6.. In Fig. 7, what do you mean by "M2PA Link Failure" in INSERVICE state?
Is it out of sequence of FSN/BSN?
 Please clarify.

regards,

Subhashini, Rohan and Magesh.

---

From: "Subhashini" <[email-masked]>
Date: Thu, 13 Mar 2003 15:50:14 -0600

In Fig. 7, processing LS PO in "Aligned Not Ready" state is missing.
It shall change the state to "Processor Outage" and the timer T1 shall be
stopped.

regards,
Subhashini ...

---

From: "Subhashini" <[email-masked]>
Date: Thu, 13 Mar 2003 16:06:36 -0600

Please ignore the mail below.

regards, 
Subhashini ...

---

From: "Subhashini" <[email-masked]>
Date: Thu, 13 Mar 2003 16:15:07 -0600

If LS PO is received during proving, it shall be locally marked that LS PO
is received. When T4 expires in this case, the state can be changed to
"Processor Outage", assuming that ready procesure is over. This is missing
in Fig. 7.
Please consider the mail below also.
regards,
Subhashini ...
----- Original Message -----
From: "Subhashini" <[email-masked]>
To: "Subhashini" <[email-masked]>; "Tom George"
<[email-masked]>
Cc: "SIGTRAN e-mail list" <[email-masked]>
Sent: Thursday, March 13, 2003 4:06 PM
Subject: Re: [Sigtran] M2PA: Revised section 3