Subject: Re: [Sigtran] M2PA version 7 changes

From: Gaiser Franz <[email-masked]>
Date: Thu, 23 Jan 2003 15:58:40 +0100

Dear All,

some remarks to the new draft version 07:

1.)  Figure 7. M2PA Link State Transition Diagram:
Why is there an arrow from state INITIAL ALIGNMENT to state ALIGNED NOT READY  ? If the local side is in processor outage, the PROVING period should be passed before moving to ALIGNED NOT READY state.
2.) Figure 7. M2PA Link State Transition Diagram:
Missing the handling of receiving LS PO in state ALIGNED READY. Transition to PROCESSOR OUTAGE ? If so, the state PROCESSOR OUTAGE handles both local and remote processor outage and then there must be an arrow from PO to IN SERVICE in case of receiving LS PO Recovered (no local PO situation).
3.) Figure 7. M2PA Link State Transition Diagram:
Missing the handling of receiving User data in state ALIGNED NOT READY. Transition to PROCESSOR OUTAGE ? What is to do with this message then ?
4.) 4.2.1 Paragraph "If M2PA receives a User Data message with an FSN that is out of order, M2PA SHALL take the link out of service."
Does "take the link out of service"  mean also that the peer side is informed via sending LS OOS message.
5.) Figure 13. Example: Link Initialization - Proving
New Timer T3 "ALIGNED" is missing in the figure.

best regards, Franz 

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---

From: Tom George <[email-masked]>
Date: Wed, 29 Jan 2003 15:27:50 -0600

> some remarks to the new draft version 07:
  [...]
> New Timer T3 "ALIGNED" is missing in the figure.

Franz,

Thanks for pointing this out. While looking at this, I found another
error in 4.1.3. 

================================================
When M2PA has both sent and received the Link Status Alignment
message, it has completed alignment.  M2PA starts the aligned timer T3
and moves to the proving state.

M2PA stops timer T3 when it receives a Link Status Proving Normal or
Proving Emergency message and starts proving period timer T4.

If timer T3 expires, then M2PA reports to MTP3 that the link is out of
service.  M2PA sends Link Status Out of Service to its peer.  M2PA
SHOULD leave the association established.  M2PA waits for MTP3 to
initiate the alignment procedure again.

During the proving period (i.e., after M2PA starts the proving period
timer T4), M2PA sends Link Status Proving messages to its peer at an
interval defined by the protocol parameter Proving_Interval. M2PA
================================================

This way, both sides will send and receive LS Alignment, start their
respective T3 timers, and sit and wait for the other side to send LS
Proving. 

I think this problem crept in when I was inserting the new text about
T3. I should say something like this: 

================================================
When M2PA has both sent and received the Link Status Alignment
message, it has completed alignment.  M2PA starts the aligned timer T3
**and the proving period timer T4,** and moves to the proving state.

M2PA stops timer T3 when it receives a Link Status Proving Normal or
Proving Emergency message[DELETE "and starts proving period timer T4"].

If timer T3 expires, then M2PA reports to MTP3 that the link is out of
service.  M2PA sends Link Status Out of Service to its peer.  M2PA
SHOULD leave the association established.  M2PA waits for MTP3 to
initiate the alignment procedure again.

During the proving period (i.e., after M2PA starts the proving period
timer T4), M2PA sends Link Status Proving messages to its peer at an
interval defined by the protocol parameter Proving_Interval. M2PA
================================================

And, of course, Figure 13 should be updated accordingly.

-- 
* Tom George       PB7-24001 (near B-21)      [email-masked]  *
* 972-519-3168   Intranet:  http://www.ssd.usa.alcatel.com/~tgeorge/  *
* Alcatel USA, Inc.; 1000 Coit Rd, MS PB7-SWPRO; Plano TX 75075-5813  *
* 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: Tom George <[email-masked]>
Date: Wed, 29 Jan 2003 15:52:14 -0600

Franz and others,

Yes, in that case M2PA should send LS OOS to its peer. 

There are several places in the document where the link goes OOS. As it
stands now, I do not always state all of the actions to be taken because
they are more-or-less understood:

- Send LS OOS to the peer.
- Notify MTP3 of Out of Service condition.
- Leave the SCTP association up. (a SHOULD)
- Wait for MTP3 to begin alignment.

What is the best way to explain this? Repeat it throughout the document,
or have a little OOS section (similar to 4.2.3  Link deactivation), or
just leave it as is and count on the reader to understand it?

tomG.

  [...]
> 4.) 4.2.1 Paragraph "If M2PA receives a User Data message with 
> an FSN that is out of order, M2PA SHALL take the link out of service."
  [...]

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 29 Jan 2003 17:06:59 -0700

Tom,

The problem is the LSC doesn't really have a proving state (only IAC
has proving state).  LSC always moves from INITIAL ALIGNMENT to either
ALIGNED READY or ALIGNED NOT READY.  You might change the diagram as
follows:

 From: 

  |                       |                            |                
  |                       | MTP3 Start                 |                
  |                       V                            |                
  |                 +-----------+                      |                
  |                 |  INITIAL  |                      |                
  +<----------------| ALIGNMENT |--------------------->+                
  |      MTP3 Stop  +-----------+     SCTP Comm Error  |                
  |   OR T2 Expiry        |  ^     OR SCTP Comm Lost   |                
  |   OR Receive LS OOS   |  |                         |                
  |                       |  +-------------------------|--------+      
  |                       |              LPO/LPR       |        |      
  |                       |                            |        |
  |                       | Receive LS Align           |        |
  |                       |                            |        |
  |                       V                            |        |
  |                 +-----------+        LPO/LPR       |        |
  |                 |  PROVING  |<---------------------|--------+
  |<----------------|           |--------------------->+        |
  |      MTP3 Stop  +-----------+     SCTP Comm Error  |        |
  |   OR T3 Expiry        |        OR SCTP Comm Lost   |        |
  |   OR Receive LS OOS   |                            |        |      
  |                       | T4 Expiry                  |        |      
  |                       | Send LS Ready              |        |      
  |                       V                            |        V      
  |                 +-----------+        LPO/LPR       |  +-----------+
  |                 |  ALIGNED  |<---------------------|->|  ALIGNED  |
  +<----------------|   READY   |--------------------->+  | NOT READY |
  |      MTP3 Stop  +-----------+     SCTP Comm Error     +-----------+
  |   OR T1 Expiry        |        OR SCTP Comm Lost         |       |
  |   OR Receive LS OOS   |                                  |   T1  | 
  |   OR Receive LS Align | Receive LS Ready      Receive    | Expiry|
  |                       | OR Receive User Data    LS Ready | OR Rcv|
  |                       |                       OR Receive |    LS |
  |                       |                         LS PO    |  Align|
  |                       |                                  |       |

 To:

  |                       |                            |               
  |                       | MTP3 Start                 |               
  |                       V                            |               
  |                 +-----------+        LPO/LPR       |  +-----------+
  |                 |  INITIAL  |<---------------------|->|  INITIAL  |
  +<----------------| ALIGNMENT |--------------------->+  | ALIGNMENT |
  |      MTP3 Stop  +-----------+     SCTP Comm Error  |  +-----------+
  |   OR T2 Expiry        |        OR SCTP Comm Lost   |        |      
  |   OR Receive LS OOS   |                            |        |      
  |                       | Receive                    |   Recv |      
  |                       | LS Align                   |     LS |      
  |                       |                            |  Align |      
  |                       V                            |        V      
  |                 +-----------+        LPO/LPR       |  +-----------+
  |                 |  PROVING  |<---------------------|->|  PROVING  |
  |<----------------|           |--------------------->+<-|           |
  |      MTP3 Stop  +-----------+     SCTP Comm Error  |  +-----------+
  |   OR T3 Expiry        |        OR SCTP Comm Lost   |        |      
  |   OR Receive LS OOS   |                            | T4 Exp |      
  |                       | T4 Expiry                  |   Send |      
  |                       | Send LS Ready              |  LS PO |      
  |                       V                            |        V      
  |                 +-----------+        LPO/LPR       |  +-----------+
  |                 |  ALIGNED  |<---------------------|->|  ALIGNED  |
  +<----------------|   READY   |--------------------->+  | NOT READY |
  |      MTP3 Stop  +-----------+     SCTP Comm Error     +-----------+
  |   OR T1 Expiry        |        OR SCTP Comm Lost         |       | 
  |   OR Receive LS OOS   |                                  |   T1  | 
  |   OR Receive LS Align | Receive LS Ready      Receive    | Expiry| 
  |                       | OR Receive User Data    LS Ready | OR Rcv| 
  |                       |                       OR Receive |    LS | 
  |                       |                         LS PO    |  Align| 
  |                       |                                  |       | 
  |                       |                                  |       | 
  |                       V                                  V       | 
  |                 +-----------+        LPO/LPR       +-----------+ | 
  |                 |    IN     |<-------------------->| PROCESSOR | | 
  |                 |  SERVICE  |                      |   OUTAGE  | | 
  |                 +-----------+                      +-----------+ | 

This would indicates that the LSC moves from INITIAL ALIGNMENT to
ALIGNED READY or ALIGNED NOT READY regardless of PROVING.  That is what the
line from INITIAL alignment to ALIGNED NOT READY was intended to indicate
in shorthand.

I suppose one could draw it as:

  |                       | MTP3 Start                 |               
  |                       |                            |               
  |                       |   +-------+                |               
  |                       |   |       | LPO/LPR        |               
  |                       V   V       |                |               
  |                 +-----------+     |                |               
  |                 |  INITIAL  |<----+                |               
  +<----------------| ALIGNMENT |--------------------->+               
  |      MTP3 Stop  +-----------+     SCTP Comm Error  |               
  |   OR T2 Expiry        |        OR SCTP Comm Lost   |               
  |   OR Receive LS OOS   |                            |               
  |                       | Receive                    |               
  |                       | LS Align                   |               
  |                       |                            |               
  |                       |   +-------+                |               
  |                       |   |       | LPO/LPR        |               
  |                       V   V       |                |               
  |                 +-----------+     |                |               
  |                 |  PROVING  |<----+                |               
  |<----------------|           |--------------------->+               
  |      MTP3 Stop  +-----------+     SCTP Comm Error  |               
  |   OR T3 Expiry        | |      OR SCTP Comm Lost   |               
  |   OR Receive LS OOS   | |                          |               
  |                       | +--------------------------|--------+      
  |                       |                            |   T4   |      
  |                       | T4 Expiry                  | Expiry |      
  |                       | Send LS Ready              | Send   |      
  |                       V                            | LS PO  V      
  |                 +-----------+        LPO/LPR       |  +-----------+
  |                 |  ALIGNED  |<---------------------|->|  ALIGNED  |
  +<----------------|   READY   |--------------------->+  | NOT READY |
  |      MTP3 Stop  +-----------+     SCTP Comm Error     +-----------+
  |   OR T1 Expiry        |        OR SCTP Comm Lost         |       | 
  |   OR Receive LS OOS   |                                  |   T1  | 
  |   OR Receive LS Align | Receive LS Ready      Receive    | Expiry| 
  |                       | OR Receive User Data    LS Ready | OR Rcv| 
  |                       |                       OR Receive |    LS | 
  |                       |                         LS PO    |  Align| 
  |                       |                                  |       | 
  |                       |                                  |       | 
  |                       V                                  V       | 
  |                 +-----------+        LPO/LPR       +-----------+ | 
  |                 |    IN     |<-------------------->| PROCESSOR | | 
  |                 |  SERVICE  |                      |   OUTAGE  | | 
  |                 +-----------+                      +-----------+ | 

The effect is the same.  The diagram is certainly not intended to be 100%
complete, it is an overview.  The text should be consulted.

--brian

Tom George wrote:                                   (Wed, 29 Jan 2003 17:18:23)
> IMHO if there is a local PO while in INITIAL ALIGNMENT, M2PA should
> continue sending/receiving LS Alignment, i.e., remain in INITIAL
> ALIGNMENT. 
> 
> After the LS Alignment is sent and received, M2PA would move to PROVING
> and send/receive LS Proving messages. 
> 
> When T4 expires, it seems to me that M2PA would go ahead and
> send/receive the LS Ready messages. That's the ALIGNED READY state. 
> 
> In short, it looks to me that if there is a local PO, M2PA should
> continue with alignment and proving and should not go into ALIGNED NOT
> READY until it is completed with the ALIGNED READY state.
> 
> Or if M2PA does go to ALIGNED NOT READY earlier than that, it should
> continue doing what it would have done in INITIAL ALIGNMENT, PROVING,
> and ALIGNED READY. Which looks like a confusing way to explain it. 
> 
> tomG.
> 
> Gaiser Franz wrote:
> > 
> > Dear All,
> > 
> > Why is there an arrow from state INITIAL ALIGNMENT to state 
> > ALIGNED NOT READY  ? If the local side is in processor outage, 
> > the PROVING period should be passed before moving to 
> > ALIGNED NOT READY state.
>   [...]
> 
> -- 

-- 
Brian F. G. Bidulock
[email-masked]
http://www.openss7.org/

---

From: Tom George <[email-masked]>
Date: Wed, 29 Jan 2003 17:18:23 -0600

tomG.

  [...]

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 29 Jan 2003 15:27:05 -0700

Tom,

I like the little OOS section idea.

--brian

Tom George wrote:                                                                      (Wed, 29 Jan 2003 15:52:14)