Subject: [Sigtran] SUA routing contexts

From: Steve Hill <[email-masked]>
Date: Tue, 19 Jun 2007 14:47:36 +0100

In IPSP operation it is my understanding that the sending AS and receiving
AS do not both need to be assigned the same routing context number.  For
example:

       AS (rc = 1)
            |
           ASP 10.0.0.1:14001
            *
            *
            *
           ASP 10.0.0.2:14001
          /   \
AS (rc = 2)    AS (rc = 3)

In the above case, the AS at 10.0.0.1 can send messages to both the ASs at
10.0.0.2, despite the routing context numbers being different.  As such,
the routing context parameter in the CLDT message always identifies the
destination AS, not the source AS.

My question is regarding how the routing context parameter should be used
when sending to an SG.  The parameter is listed as mandatory, but when
sending to an SG I am unclear on what value should be placed in the
parameter since there is no concept of a destination routing context?

-- 
 - Steve Hill
   Software Engineer

Dialogic (UK) Limited
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---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Tue, 19 Jun 2007 08:02:22 -0600

Steve,

Steve Hill wrote:                               (Tue, 19 Jun 2007 14:47:36)
> destination AS, not the source AS.

The above is true only for IPSP DE mode, where the RC represents only a
_single_ direction of traffic flow.  For IPSP SE mode, there can only
be one RC between a pair of (local and remote) AS, representing _both_
directions of traffic flow.

> parameter since there is no concept of a destination routing context?

The ASP-SG mode is the same as the IPSP SE mode: there can only be one RC
value between an AS and an SGP, again representing _both_ directions of
traffic flow.

This is really no different for SUA than it is for M3UA.

--brian

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

---

From: "Ambika Tripathy" <[email-masked]>
Date: Wed, 20 Jun 2007 11:12:57 +0530

Hi Brain,

   Can I expect the same sequence number from the peer's CLDT message that i
have sent just to that end?

     -------------------CLDT-----------------> Sequence Number = 23
    <------------------CLDT------------------- Is it the peer will encode
the 23 here in the sequence Number field or encode the value as per its
implementation.

br,
Ambika

-- 
Br,
Ambika Prasad Tripathy
Nethawk Networks
Cell: +91-94375 47730

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 20 Jun 2007 00:15:57 -0600

Ambika,

Ambika Tripathy wrote:                         (Wed, 20 Jun 2007 11:12:57)
>
>        Can I expect the same sequence number from the peer's CLDT message
>    that i have sent just to that end?
> 
>         <------------------CLDT-------------------  Is  it  the peer will
>    encode the 23 here in the sequence Number field or encode the value as
>    per its implementation.

Each side chooses its Sequence Number (sequence control parameter and
ultimately SLS value) independently.  It is unlikely that it is in any
way related to the value chosen by the peer.  (The SCCP-User does not
normally have access to this value in receive N-UNITDATA-Indication
primitives, but may set Sequence Control in N-UNITDATA-Request primitives,
cf. Q.711.)

--brian

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