Subject: m3ua v6 - Protocol Data parameters

From: Barry Nagelberg <[email-masked]>
Date: Tue, 20 Mar 2001 13:47:21 -0500

Greg,

In Section 3.3.1 (Payload Data Message), it is not clear why the draft
specifies the format of the SIO and routing label Protocol Data parameters.
Nowhere does the draft state any use that the M3UA layer may make of these
fields.

I assume that these fields are an integral part of the MTP3 signaling as
defined in Section 1.3.2.1 (Support for the transport of MTP3-User
Messages), and do not require any composition or decoding by the M3UA layer:

"... the SCCP and ISUP messages received from the SS7 network by the SG are
not re-encoded into a different format for transport between the M3UA peers.
The MTP3 Service Information Octet (SIO) and Routing Label (OPC, DPC, and
SLS) are included, encoded as expected by the MTP3 and MTP3-User protocol
layer."

If they are encoded "as expected" by the other layers, do not require any
composition, decoding or re-encoding by the M3UA layer, and if there is no
M3UA-specific use stated for them, then why are we specifying them in the
draft?

Barry Nagelberg
Member Technical Staff
S-Link Corp.
[email-masked]
+1-856-642-9229 x237

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From: "Sidebottom, Greg [BCNR:7M01:EXCH]" <[email-masked]>
Date: Thu, 29 Mar 2001 13:16:12 -0500

Hi Barry,

You are correct that the SIO and Routing Label are not M3UA parameters in
themselves and the M3UA does not require their decoding.  

The ITU and ANSI format of the SIO and Routing Label bits are only shown in
the M3UA (as examples!) because it was pointed out by several people that
the way the ITU and the IETF document message bits/bytes and the way the
bits go on the wire is quite different and this could be a potential problem
for inter-operability of Data messages.   In short, the ITU represents the
MTP3 messages as a series of bytes sent as string of bits on to the wire
(LSB to MSB).  The IETF shows messages in 4-byte words that don't go on the
wire the same way - Joyce Archibald explained this best in a message to the
list (I have captured the relevant explanation below):

        "Octets are related to 32-bit words as follows:

                  Octet 1 = bits 0-7
                  Octet 2 = bits 8-15
                  Octet 3 = bits 16-23
                  Octet 4 = bits 24-31

         Octets are transmitted in order (i.e. octet 1 first), least
significant bit 
         first (i.e., the first bit transmitted is bit 7 of octet 1)"

Basically, if we are not clear in the representation of the Payload Data
parameter bits and bytes then the sender and receiver may not be on the same
page for the bits on the wire and we could have an inter-operability issue,
with the receiver not being able to parse the Payload Data.   I consider
this point to be valid because when I tried the exercise of how the MTP3
bits are represented in the M3UA message I got a completely different (and
incorrect too!) answer than others.

Hope this helps,

    Greg

 -----Original Message-----
From: 	Barry Nagelberg [mailto:[email-masked]] 
Sent:	Tuesday, March 20, 2001 1:47 PM
To:	[email-masked]
Cc:	[email-masked]; Gene Litt
Subject:	m3ua v6 - Protocol Data parameters

Greg,

Barry Nagelberg
Member Technical Staff
S-Link Corp.
[email-masked]
+1-856-642-9229 x237

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