Subject: RE: [Sigtran] Re: M3UA NA in DATA message

From: "Schantz, John" <[email-masked]>
Date: Wed, 5 Mar 2003 16:43:25 -0600

OK, you have to remember that you are coming at this an IP or SS7-newbie
point of view.  I have had systems in the SS7 networks since 1988.
These systems have not gone away but are constantly growing (in size and
ability).

>From an existing SS7 system's point of view, the RK and RC are not
needed.  They are redundant and just an "index" form of the information
in the messages routing label.  In fact my system will ignore any RC it
receives in a message because it already supports all the SS7 functions
that use the routing label information.

Now let's look at an example.  Suppose my system is connected to an SG
that connects to 2 independent ITU networks.  Since ITU point code is
only 14-bits, there is no coordination of how point codes are assigned
to nodes in each network.  In fact my node would have a point code from
each network and there is a non-zero probability that the point code
from each network could be the same.  But we can assume that they are
different also.  If they are different, both of my system's point codes
could be used by another system in the other network.

Therefore, an NA is required in the messages my system receives and
sends.  For received messages, it tells me which network sent the
messages and is used to uniquely identify the sender (NA+OPC).  It is
very likely that the point code in the OPC will exist in both networks.
For outbound messages, NA tells the SG which network the message is
destined for.  If I remember right, there really isn't an RK/RC for
messages sent to an SG.

Now if independent associations are used to carrying the traffic for
different networks, then there are configuration methods for handling
this and NA wouldn't be needed anywhere.  But I don't think independent
associations has been required.

John 

-----Original Message-----
From: Brian F. G. Bidulock [mailto:[email-masked]] 
Sent: Wednesday, March 05, 2003 2:10 AM
To: B.Sasidhar Reddy
Cc: [email-masked]; [email-masked]
Subject: [Sigtran] Re: M3UA NA in DATA message

Sasidhar,

You don't need to send the Network Apperance parameter.  It is optional.

However, some implementations might need it to work properly. The note
in 3.3.1 says "the parameter may be configured to be present for the use
of the receiver."  Note also that the parameter is for SSNM as well as
DATA.

There was quite a lot of discussion about this before we came to a
workable concensus.

IIRC John Schantz' implementation (and possibly others) use this
parameter.

In our implementation, per 3.3.1, we send this parameter whenever it is
available to M3UA (i.e.  configured) for those peers that might benefit
from it.  Whenever we receive it in DATA or SSNM we check it if
available (again configured) and return the Invalid Network Appearance
error if it does not match configuration.  If it is not configured we
ignore NA parameters in received DATA and SSNM and do not send NA in
outgoing DATA or SSNM.

I think John could better summarize its uses as he was one of the main
advocates of including it in DATA and SSNM during the discussions.
John?

--brian

B.Sasidhar Reddy wrote:
(Wed, 05 Mar 2003 13:26:59)
> 
>    Brian,
> 
>         The Routing Key contains the Network Appearance parameter. So
the
>    Routing context itself identifies the network.
> 
>          Why we should again send the Network Appearance parameter in
the
>    DATA message.
>    Thanks
>    Sasidhar

-- 
Brian F. G. Bidulock
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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 5 Mar 2003 15:57:16 -0700

John,

Schantz, John wrote:                                                              (Wed, 05 Mar 2003 16:43:25)
> These systems have not gone away but are constantly growing (in size and

Who are you talking to?  (I _built_ SS7 networks before 1988.)

> destined for.  If I remember right, there really isn't an RK/RC for

The rules of 3.3.1 and the IG apply in both directions.

> associations has been required.

Thanks for the explanation.

--brian

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