Subject: [Sigtran] IIDs

From: "Sachin Sharma" <[email-masked]>
Date: Wed, 20 Mar 2002 09:40:53 +0530

Hi,
I am new to ISDN and IUA.I would like to know as to how is the IID to
physical interface mapping done?How do D channels and TEIs fit into all
this?What are the various componnets of an IID?
I would apprecite if a small example can be given.

Regards,
Sachin

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 20 Mar 2002 00:47:23 -0600

Sachin,

Someone correct me if I'm wrong, but this mailing list is for
Working Group discussions on SIGTRAN UAs, including IUA.  It
is not really intended as a resource for helping you learn about
ISDN.  There are groups on usenet for that (comp.dcom.idsn or
some such) and, of course, there are the ISDN standards
specifications and a number of good books written on the subject.

Sachin Sharma wrote:                                       (Wed, 20 Mar 2002 09:40:53)
> physical interface mapping done?

By configuration at the SG.

> How do D channels and TEIs fit into all this?

IIDs identify D channels.

> What are the various componnets of an IID?

Basically a 32-bit integer.  Text identifiers can be used.

> I would apprecite if a small example can be given.

See the RFC 3057 for examples.

--brian

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

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From: "Sachin Sharma" <[email-masked]>
Date: Wed, 20 Mar 2002 15:48:08 +0530

Consider this scenario:
Suppose we need two ASPs to handle traffic for a particular AS.Now one of
the ASPs becomes active and sends ASP Active.The SG responds with ASP Active
Ack for that.Now logically that ASP can send data to that SG.But as we
require two ASPs to handle traffic,the SG won't handle traffic from that
ASP.
Now SG knows it can send data to that ASP but it won't send it.But the ASP
doesn't know if to send data to the SG/not.
Don't we risk losing data in this case?
Or the SG won't send the ASP Active ACK even for the first ASP?

Sachin

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From: "Sundaresan M" <[email-masked]>
Date: Wed, 20 Mar 2002 17:45:50 +0530

Hi,

Please note that the ASP Active contains something called as Interface
Identifiers and it is to these IID's SG responds for.

The ASPAC contains one or more IID's to indicate for which AS the ASPAC
applies to. Now SG responds to the ASP with a ASPAC ACK msg and hence starts
sending traffic for the corresponding AS to that ASP.

Brian, is it okay.

Best Regards,
Sundar.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of
Sachin Sharma
Sent: Wednesday, 20 March 2002 3:48 PM
To: [email-masked]
Cc: [email-masked]
Subject: [Sigtran] ASP states

Consider this scenario:

Sachin

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From: "Siddhartha Prasad" <[email-masked]>
Date: Wed, 20 Mar 2002 17:33:35 +0530

Sachin

 As per the drafts of sigtran UAL (user adaptation layers) , AS is an
logical entity & may have n number (max 16) of ASP`s associated with it,
note that one ASP can be associated with more than one AS also.
 SG does send Ack for ASP up message though it may be the first ASP. Incase
of some failure or transition (no ASP is active), SGP will buffer the
message destined for this AS for a time t( ) or until an ASP becomes
available. When no ASP becomes available before expiry of  t( ), the SGP
will flush the buffered messages and initiate the appropriate return or
refusal procedures.

 Would appreciate comments on this.

Siddhartha

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From: "Tolga Asveren" <[email-masked]>
Date: Wed, 20 Mar 2002 09:03:31 -0500

For m3ua, it was added, that it is responsibility of ASPs -how this is
achieved is implementation dependent- to know the number of active ASPs for
a particular AS and act according to this. I expect the other UAs behave
similar.

   Tolga

> Sent: Wednesday, March 20, 2002 5:18 AM
> To: [email-masked]
> Cc: [email-masked]

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From: Andrew Booth <[email-masked]>
Date: Fri, 22 Mar 2002 09:45:55 -0500

Hi Sachin,

I think the answer to your question will depend on who's SG you're talking
with, here are some extra comments.

Relevant info:
M3UA draft 12 section 4.3.4.3 paragraph 11 or so, indicates that for loadshare
mode the SGP SHOULD withhold sending a NOTIFY ( AS Active ) until there are
sufficient ASPs Active.  It also says ( in paragraph 2 ) that by sending ASPAC
Ack, the SG is indicating that it is ready to send and receive traffic to the
related routing context.  To me, these two statements are somewhat
contradictory.
I could not find an analogous paragraph in SUA ( describing withholding the
Notify ).

One interpretation would be to wait for the Notify( AS Active ) before sending
traffic.  I'm not sure the draft is clear/stringent enough about Notify
procedures to make this reliable though.  For example, what will the SG do if
an ASP becomes inactive, resulting in insufficient ASPs active in an AS?  I
don't see anywhere that the Active ASPs should get notified in any way when
there are insufficient ASPs.  The actions of the SG will probably be
implementation specific and should reasonably be tied to how it handles
messages when there are insufficient ASPs.

Conclusion: Talk to your SG vendor if possible to make sure your procedures
align.  If you're trying to build a "generic" ASP, you may have to put in some
flexibility with configuration ( or implement inter ASP communication) to
handle various possible SG interpretations.

Andrew

Sachin Sharma wrote:

> Hi Andrew,
> Assume that one SG is serviced by two ASPs in an AS.Lets say the N+1st ASP
> in that AS comes up and sends ASP Active and inturn receives ASP Ack.Can it
> now send and recieve data fom the SG?Or will it wait for some NOTIFY(which
> won't be sent as there is no AS state change)?
>
> Sachin
> From: Andrew Booth <[email-masked]>
> To: Sachin Sharma <[email-masked]>
> Sent: Thursday, March 21, 2002 10:24 PM
> Subject: Re: [Sigtran] ASP states
>
> > Hi Sachin,
> >
> > If I remember correctly there was some debate on the list about this a
> while
> > ago for M3UA/SUA, it was proposed that if the AS needs n ASPs to handle
> traffic
> > (e.g. in loadshare mode) then the SG could withhold sending Notify( AS
> Active )
> > until the nth ASP is active.  In this way the Notify would let the ASPs
> know
> > when to begin sending traffic.  I don't know what the status of this
> proposal
> > is, and I'm afraid I don't have the thread reference easily available.
> >
> > Andrew
> >
> > Sachin Sharma wrote:
> >
> > > Consider this scenario:

---

From: "Tolga Asveren" <[email-masked]>
Date: Fri, 22 Mar 2002 11:40:22 -0500

Andrew,

Please see comments below.

  Tolga

> Andrew Booth
> Sent: Friday, March 22, 2002 9:46 AM
> To: Sachin Sharma
> Cc: [email-masked]; [email-masked]
> Subject: [Sigtran] ASP states in N+K redundancy mode.
>
>
> Hi Sachin,
>
[TOLGA] It was proposed to make ASPs withhold traffic till NTFY was
recevied, but because at this time m3ua was close to be RFC, no big changes
were desirable. So, it was added that it is ASPs responsibility to decide,
when n ASPs are active for a particular AS.
> there are insufficient ASPs.  The actions of the SG will probably be
[TOLGA] When Figure5-"AS State Transition Diagram" is updated accordingly,
in the scenario you described a NTFY will be sent from SG to ASP, because AS
state will change.
> > > > Suppose we need two ASPs to handle traffic for a particular
> AS.Now one
> > of
> > > > the ASPs becomes active and sends ASP Active.The SG
> responds with ASP
> > Active
> > > > Now SG knows it can send data to that ASP but it won't send
> it.But the
> > ASP