Subject: [SUA issue 15]: Segmentation/Reassembly/Sequencing Part III

From: [email-masked]
Date: Thu, 6 Sep 2001 11:38:25 +0300

Hi all,

> > Subissue 3: Should segmentation parameter be included
> > ==========  in all CLDT messages sent by ASP.
> > 
> > Changes needed:
> > 
> > 1 New optional parameter for CLDT message:
> > 
> > Segmentation
> > 
> >    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 = 0x010x          |             Length            |
> >   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> >   | first/remain  |             Segmentation Reference            |
> >   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> > 
> > The first/remaining segments field is formatted as follows :
> > bit 8 (MSB) : indicates whether this is the first segment 
> > (1) or not (0)
> > 
> > bits 1-7 : indicate the number of remaining segments, value 
> > between 0 and 15
> > 
> > The field would thus be coded 1000 0000 (first, no 
> > remaining segments) for a non-segmented CLDT.
> > 
> > The segmentation reference field is a 3 byte integer, 
> > assigned by the ASP.
> > 
> > Procedures to be added
> > 
> > ASP -> SG direction
> > 
> > Text to add:
> > 
> > SGP/ASP/IPSP MUST be prepared to deal with segmented CLDT 
> > (reassembly, CLDS, etc..); an SGP SHOULD support segmentation 
> > of unsegmented CLDT where required;  an ASP SHOULD place 
> > segmentation parameter in CLDT where segmentation might be 
> > required at an SGP and MAY always include it; an
> > ASP/SGP/IPSP MAY segment CLDT.
> > 
> > Sandeep >> I have following concerns for supporting this 
> > functionality. Since there is a protocol conversion taking 
> > place at SG (from SUA to SCCP), it is not very clear if 
> > inclusion of segmentation parameter will avoid interworking
> > issues. What interworking problems does the inclusion of 
> > segmentation parameter avoids ?
> 
> It avoids assignment of the same segmentation reference 
> parameter (SLR) at multiple SGs.  The segmentation reference 
> must be assigned by the ASP to avoid this.  This parameter 
> also allows ASPs to segment if desired.

Additionally, there is always the 'Segmentation not supported'
error code, to ensure interoperability.
 
> > Considerations also needed for enhancing interface boundary between
> > NIF/SUA and NIF/SCCP for passing this parameter across from 
> > SUA to SCCP.

So, we need to add text that states:

When the ASP segments CLDT, the Segmentation parameter MUST
be passed from the SUA layer to the SCCP layer at the SG.

Comments?

John

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