Subject: [Sigtran] question about OPC/DPC/SLS in M3UA

From: "Ling-Chih Kao" <[email-masked]>
Date: Wed, 15 Oct 2003 10:25:25 +0800

The number of bits for OPC/DPC/SLS is 14/14/4 in SS7.
Why does OPC/DPC/SLS change to 32/32/8 in M3UA?

Thanks

Ling-Chih Kao

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Tue, 14 Oct 2003 20:38:30 -0600

Ling-Chih,

Ling-Chih Kao wrote:                                                             (Wed, 15 Oct 2003 10:25:25)
>    The number of bits for OPC/DPC/SLS is 14/14/4 in SS7.

Not in ANSI, TTC, Australian, Canadian, China, ... variants.

In those it is: 24/24/8

Besides, it is not 32/32/8 in M3UA: see RFC 3332 section 3.4.1
on page 37.

--brian

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

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From: "Ling-Chih Kao" <[email-masked]>
Date: Wed, 15 Oct 2003 11:06:00 +0800

Brian

The OPC/DPC/SLS in Payload data of  section 3.3.1 is 32/32/8.

Thanks

Ling-Chih Kao

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Tue, 14 Oct 2003 21:21:02 -0600

Ling-Chih,

Ling-Chih Kao wrote:                                                             (Wed, 15 Oct 2003 11:06:00)
> The OPC/DPC/SLS in Payload data of  section 3.3.1 is 32/32/8.

Please read: (page 34, caps mine)

   Originating Point Code: 32 bits (unsigned integer)
   Destination Point Code: 32 bits (unsigned integer)

   The Originating and Destination Point Code fields CONTAINS THE OPC
   AND DPC FROM THE ROUTING LABEL OF THE ORIGINAL SS7 MESSAGE IN NETWORK
   BYTE ORDER, JUSTIFIED TO THE LEAST SIGNIFICANT BIT.  UNUSED BITS ARE
   CODED `0'.

This is NOT a 32 bit point code, it is the point code from the SS7
message justified to the least significant bit in a 32 bit field with
unused bits coded zero.  Which is precisely what is shown in section
3.4.1!!!!!

Also: (page 35, caps mine)

   Signalling Link Selection: 8 bits (unsigned integer)

   The Signalling Link Selection field CONTAINS THE SLS BITS FROM THE
   ROUTING LABEL OF THE ORIGINAL SS7 MESSAGE JUSTIFIED TO THE LEAST
   SIGNIFICANT BIT AND IN NETWORK BYTE ORDER.  UNUSED BITS ARE CODED
   `0'.

Gee, same thing for SLS....

This is NOT an 8 bit SLS, it is the SLS from the SS7 message justified
to the least significant bit in an 8 bit field with unused bits coded
zero.

Do you understand yet?

The size has not changed: it is only a matter of padding and alignment.

--brian

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