Subject: [Sigtran] SUA: Data limitation based on SS7 SCCP specification.

From: "Sulakshan Vajipayajula" <[email-masked]>
Date: Tue, 23 Oct 2007 10:58:15 -0400

Hi all,

I have a question pertaining to limiting the data size in SUA connection
oriented messages such as CORE or RELRE. 

The RFC says the following.  My question is, if the implementation
should follow SS7 SCCP specification in limiting the data size or should
it allow the data size based on the section 3.10.11.  The SCCP spec
limits the data to 128 octets. Does this apply to SUA as well?

RFC 3868                          SUA                       October 2004

3.10.11.  Data

    0                   1                   2                   3
    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 = 0x010b         |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                             Data                              /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Data parameter field contains the SS7 SCCP-User application
   Message, for example an INAP/TCAP message.

SCCP Specification:
-------------------
Parameter Reference Type (F V O) Length (octets)
--------------------------------------------------
Data  |     3.16   |      O   |        3-130

Thank you
Sulakshan

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---

From: "Stewart Patch" <[email-masked]>
Date: Tue, 23 Oct 2007 16:03:13 -0400

It depends whether you are going to use SUA only in the IPSP
configuration or will be interworking with SS7 networks through a
signalling gateway. If you intend to pass through a gateway, you have to
be sensitive to the characteristics of the gateway, the network on the
other side, and the destination signalling point.

The network will have a limit on the size of a message, most likely the
traditional SS7 payload size of around 256 octets (less than that for
data in an SCCP message). So if there is no message segmentation, the
originating SP has to hold to that.

Segmentation requires support at the originating ASP or signalling
gateway and at the destination point (and the support should be assumed
to be absent unless known to be otherwise). 

Stewart Patch
Engineering
NewStep Networks Inc.
+1 416 979 5404 x485

-----Original Message-----
From: Sulakshan Vajipayajula [mailto:[email-masked]] 
Sent: 23 October 2007 10:58
To: [email-masked]
Subject: [Sigtran] SUA: Data limitation based on SS7 SCCP specification.

Hi all,

3.10.11.  Data

    0                   1                   2                   3

SCCP Specification:
-------------------

Thank you
Sulakshan

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Tue, 23 Oct 2007 15:03:05 -0600

Sulakshan,

Well, that's why I put this in: RFC 3868, Page 115:

4.7.  SCCP - SUA Interworking at the SG

4.7.1.  Segmenting / Reassembly

   When it is expected that signalling messages will not fit into a PDU
   of the most restrictive transport technology used (e.g., 272-SIF of
   MTP3), then segmenting/reassembly could be performed at the SG, ASP
   or IPSP.  If the SG, ASP or IPSP is incapable of performing a
   necessary segmentation/reassembly, it can inform the peer of the
   failure using the appropriate error in a CLDR or RESRE/COERR message.

--brian

Sulakshan Vajipayajula wrote:                  (Tue, 23 Oct 2007 10:58:15)

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