Subject: [Sigtran] M2PA draft comments and questions.

From: "John Li" <[email-masked]>
Date: Tue, 11 Feb 2003 10:09:47 -0500

All,
I sent the following comments and questions to the group a while ago, and have not got responses yet. here goes again. 
thanks.
John

1.	In section 1.5: the following statement is somewhat confusing.
“The SG is an IPSP equipped with both traditional SS7 and IP
network connections. In effect, the Signaling Gateway acts as a
Signal Transfer Point (STP)” 

Perhaps we can say "The SG interconnects SS7 and IP networks by
converting signaling traffic" or just refer to the definition in
section 1.2

2.	Section 2.1.5 Message length
Should we specify the valid value range of the length?

3.	Section 2.3.1 User Data

statement "M2PA does not add padding to the MTP3 message.".
I think we should make it a requirement: “M2PA should not add padding
to the MTP3 message.”

4.	In section 4.1.3 Link alignment

perhaps we can specify the recommended practice for choosing
emergency proving vs. normal proving during alignment procedure.

5.	Section 4.1.8: 
"If a Link Status Alignment message with an unsupported
received by the newer version, the receiving end's M2PA
SHALL NOT complete the alignment procedure."

can we clearly define the behavior of not completing the alignment
procedure?

6.	section 4.2.1 sending and receiving messages
When M2PA receives a User Data message with Backward Sequence Number
equal to 'n', it may remove all messages with Forward Sequence Number
<= n from its queue.

This is incorrect. Consider at the time SN is cycled to 0 from 127
(assume 128 buffers), there are 127, 126, etc are waiting for
acknowledgement. We should replace it with “The message n and all
outstanding (not yet acknowledged) messages sent before the message n
may be removed from its queue.

7.	section 4.2.1
If M2PA receives an empty User Data message, it SHALL NOT send an
acknowledgement of that message.

What is empty User Data message? FISUs? 

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From: Tom George <[email-masked]>
Date: Thu, 20 Feb 2003 15:52:19 -0600

Summing up the discussion, here is what I plan to do for each of these
items....

John Li wrote:
> ?The SG is an IPSP equipped with both traditional SS7 and IP
> Signal Transfer Point (STP)?
> 

I reworded this paragraph slightly. 
          
	  Figure 2 shows an example of M2PA used in a Signaling
	  Gateway (SG). The SG is an IPSP equipped with both
	  traditional SS7 and IP network connections.  Any of the
	  nodes in the diagram could have SCCP or other SS7
	  layers. The Signaling Gateway acts as a Signal Transfer
	  Point (STP).  Other STPs MAY or MAY NOT be present in the
	  SS7 path between the SEP and the SG.

> Should we specify the valid value range of the length?

No. This is determined by MTP3. 

No change to the draft is necessary.

> I think we should make it a requirement: ?M2PA should not add padding
> to the MTP3 message.?

I changed this to "M2PA SHALL NOT add padding to the MTP3
message." It has to be a firm requirement.

> emergency proving vs. normal proving during alignment procedure.

No. This is determined by MTP3. 

No change to the draft is necessary.

> can we clearly define the behavior of not completing the alignment

I changed this sentence to: "If a Link Status Alignment
message with an unsupported version is received by the newer
version, the receiving end's M2PA SHOULD reply with a Link
Status Out of Service message and not complete the alignment
procedure."

> acknowledgement. We should replace it with ?The message n and all

There is a general warning about this in this section
(4.2.1).

> What is empty User Data message? FISUs?

It's an Ack (sections 2.3.1, 4.2.1). 

No change to the draft is necessary.

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