Subject: Re: [SUA issues 3,6,7] text

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Mon, 3 Sep 2001 18:50:10 -0500

Sandeep,

Please see comments below...

On Mon, 03 Sep 2001, [email-masked] wrote:
> 
> 
> 
> John ,
> 
> You  can blame me for being stuck with a trivial issue , I still request ( once
> again) for following clarifications in the text.
> 
> 
> Best Regards,
> -Sandeep
> 
> 
> 
> 
> 
> 
> [email-masked] on 09/03/2001 03:50:38 PM
> 
> Please respond to [email-masked]
> 
> To:   "sigtran" <[email-masked]>
> cc:   [email-masked] (bcc: Sandeep Mahajan/HSS)
> 
> Subject:  RE: [SUA issues 3,6,7] text
> 
> 
> 
> 
> Hi all,
> 
> Here is my (final) proposal for these issues.  Please check if they
> are sufficient.
> 
> John
> 
> 3.10.1 SS7 Hop counter
> 
>    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 = 0x0101          |             Length = 8        |
>   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>   |                unused                         | SS7 Hop Count |
>   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> 
> SS7 Hop Counter (3.18/Q.713)
> 
> The value of the SS7 Hop Counter is decremented with each global title
> translation and should be in the range 15 to 1.
> 
> Optional in CLDT, CLDR, CORE.
> 
> Sandeep >> I suggest the term "global title translation" be changed with "relay
> node".

All relay nodes perform GTT.  GTT may be performed more than once at
an SG which appears to the SS7 network as more than one relay node.
What constitutes a relay node is poorly defined in SUA (and SCCP for
that matter).  IMO the GTT statement is clearer.

> 
> ========================================================================
> 
> 3.10.e Sequence Control
> 
>    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 = 0x010e         |             Length = 8         |
>   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>   |                                               | Seq  Control  |
>   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> 
> Sequence Control (1.1.2/Q.714)
> 
> The field is coded with the value of the sequence control parameter
> associated with a group of messages and are chosen so as to ensure  proper
> loadsharing of message groups over SLS values while ensuring that sequence
> control values within message groups have the sequence control value coded
> with the same value as the initial message of the message group.
> 
> 
> Mandatory in CLDT, CORE, COAK, COIT.
> 
> Sandeep >> Above definition of sequence control is very encrypted and it is not
> clear how SUA recommends this parameter to be used. As this parameter is used
> for
> a) Transporting "sequence control" parameter of N-UNITDATA request primitive
> from SCCP/SUA user to SCCP in a backhaul case
> b) Something similar to how SCCP uses SLS in RL of incoming SS7 message for
> maintaining sequence of messages and loadsharing purposes in IPSP (peer to peer)
> case

Sequence control is defined by SS7 specifications.  Why not just add the
text:

  The use of Sequence Control is defined in Q.711 clause 6.2.2.2.2 Sequence
  Control.

There is no need for the proposed text as it duplicates to a large extent
the description in Q.711.

--brian

> 
> I suggest following text to start with
> 
> For Class 1
> At originating SUA node, SUA user passes "sequence control" parameter to SUA in
> N-UNITDATA request primitive. SUA use this parameter as input to AMF function
> for SCTP asssociation and stream selection and copy the same in CLDT message.
> While processing CLDT message (for protocol Class 1) at relay node , sequence
> control parameter received in the CLDT
> message SHOULD be used by AMF function for selecting next hop SCTP association
> and stream. While processing CLDT message the terminating end SUA passes the
> sequence control parameter received in CLDT message to SUA-USER using N-UNITDATA
> indication primitive. Above procedure insures sequencing of class 1 messages
> that are transferred either between IP and SS7 networks or within IP network.
> 
> For Class 0, 2 and 3
> For these protocol classes SUA User does not pass sequence control parameter to
> SUA. While processing N-CONNECT request, N-CONNECT response , and N-UNITDATA
> request (protocol class 0) primitives , SUA based on some implementation
> dependent loadsharing algorithm chooses a value of sequence control parameter.
> This should be used as input to AMF for choosing next hop SCTP association and
> stream and should be copied in CORE, COAK and CLDT (class 0) messages. At relay
> node while processing these message SUA MAY use this sequence control value for
> selecting next hop SCTP association and stream.
> Note: There is no usage of this parameter for messages of these protocol class
> transferred between IP to SS7 network, as for these protocol classes this
> parameter can not be passed across IP and SS7 networks.
> 

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

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