Subject: [Sigtran] query for bit 1 in Segmentation parameter (RFC 3868 - SUA)

From: pankaj <[email-masked]>
Date: Wed, 13 Jul 2005 18:22:32 +0530

Hi All,

            Please find below the text for segmentation parameter in section
3.10.23. (Segmentation) of RFC 3868.

"The segmentation paramter consists of the following:

   o  bit 0: first/remaing segment bit: first = 1,  remaining = 0

   o  bit 1: sequence delivery option as original demanded(= before the

      segementing) by the SCCP application.  class 0 = 0, class 1 = 1.

   o  bit 2-3: spare

   o  bit 4-7: number of remaining segments(4 bits, values 0 -15)

   o  bit 8-31:segmentation reference(3 byte integer)"

Why we need the bit 1 value to find the protocol class. I think protocol
class parameter is mandatory parameter

for both SCCP Connectionless message and SUA Connectionless message. I am
not finding the usability of this

bit 1 in segmentation parameter. Please correct me if I am wrong. Also for
protocol class 0, Is it required to do

the fragmentation and reassembly.

Also in section 3.10.23.  "The field would thus be coded 1000 0000 (first,
no remaining    segments) for a un-segmented CLDT"

How will be 1000 0000 for protocol class 1?  I think, this should be either
1000 0000 (for protocol class 0) and 1100 0000 

(for protocol class 1).

Thanks in Advance,

==Pankaj Nath==

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---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Thu, 14 Jul 2005 02:56:27 -0600

Pankaj,

bit 1 is needed because all segments of a segmented message are sent as
protocol class 1 (ordered) regardless of whether the original (unsegmented)
message as protocol class 0 or 1.  This is normal SCCP procedure.  The bit
is required to restore the proper protocol class after reassembly.

Yes, the example could have said 1100 0000 for protocol class 1, but it is
(obviously) a protocol class 0 example.

--brian

pankaj wrote:                                         (Wed, 13 Jul 2005 18:22:32)
> 
>    Hi All,
> 
>                 Please  find below the text for segmentation parameter in
>    section 3.10.23. (Segmentation) of RFC 3868.
> 
>    Why  we  need  the  bit  1  value  to find the protocol class. I think
>    protocol class parameter is mandatory parameter for both SCCP
>    Connectionless message and SUA Connectionless message. I am not
>    finding the usability of this
> 
>    bit 1 in segmentation parameter. Please correct me if I am wrong. Also
>    for protocol class 0, Is it required to do the fragmentation and
>    reassembly.
> 
>    Also  in  section  3.10.23.   "The field would thus be coded 1000 0000
>    (first, no remaining    segments) for a un-segmented CLDT"
> 
>    How  will  be 1000 0000 for protocol class 1?  I think, this should be
>    either 1000 0000 (for protocol class 0) and 1100 0000 (for protocol
>    class 1).
> 
>    Thanks in Advance,
> 
>    ==Pankaj Nath==

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