Subject: Re: [Sigtran] Interface Identifier in ASPTM message in M2UA

From: Rajesh Makhija <[email-masked]>
Date: Thu, 1 Sep 2011 14:20:47 +0530

Hello

It would be nice to reach a consensus on this matter. Requesting Brian and other forum member to share their valuable insights.....on last input from Supreet

------------
Hi Brain,

Thank you for giving insights on this matter.  It is now very clear that the length field should be equal to 8 for MAUP messages.

I would request you to throw some light for messages other than MAUP (such as ASPAC).

RFC 3331, section 3.2 states that:
-----
âThe Tag value for the Integer-based Interface Identifier is 0x1.  The  length is always set to a value of 8.â

 âThe M2UA specific message header will   immediately follow the common message header, but will âonlyâ be used   with âMAUPâ messages.â
----

As per RFC 3331, "The M2UA specific message header will immediately follow the common message header, but will only be used with MAUP messages".

For ASPTM (such as ASPAC) messages it is not very clear on what should be the value of length field.

As per RFC section 3.3.2.7, from the ASPAC message format it appears that multiple interface identifiers values can be used along with a single tag (0x1)â.

   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Tag (0xb)           |            Length = 8         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Traffic Mode Type                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Tag (0x1=integer)         |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                                                               \
   \                     Interface Identifiers*                    /
   /                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

It would be great if you could confirm if length can be greater than 8 for ASPAC messages or it has to be always set to 8 for ASPAC as well.

Thank you in advance for your views on this matter.

Thanks and Regards
Supreet Jain
----------
________________________________
From: Rajesh Makhija
Sent: Monday, August 29, 2011 4:59 PM
To: [email-masked]'; [email-masked]'
Cc: [email-masked]'; [email-masked]'
Subject: Re: [Sigtran] Interface Identifier in ASPTM message in M2UA

Hi Aditi

Thanks for your inputs.

With reference to your last mail:

"As per the structure of ASPAC defined under the section 3.3.2.7, the Interface Identifier (Tag 0x1), the value can be a set of "Interface Identifiers". The length can be other than 8."

However from one of the earlier discussion threads on Sigtran forum....:

www.ietf.org/mail-archive/web/sigtran/current/msg08554.html<http://www.ietf.org/mail-archive/web/sigtran/current/msg08554.html>

It appears that if multiple interface identifiers are to be sent they must be sent in the following manner....snippet from earlier discussions follows:

"If you want to list two Integer Interface Identifiers it is:

            Tag (0x1), Length (8)
            Integer interface id 1
            Tag (0x1), Length (8)
            Integer interface id 2

Therefore, from the earlier discussion thread, it appears that the length field can only be 8.  This is slightly different from what you mentioned. If possible, I would request Brian to throw more light on this matter.

It would be great if we can reach a consensus on this matter on this forum (.i.e. length can only be 8 or not more than 8 is also possible when tag is (0x1), as this can possibly lead to interoperability issues.

Thank you in advance for your views on this matter.

Thanks and Regards

Rajesh

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