Subject: [Sigtran] SUA v16: TID and DRM labels

From: "Barry Nagelberg" <[email-masked]>
Date: Wed, 18 Feb 2004 15:26:12 -0500

We have several suggestions for improving the clarity of the definition and
use of the TID and DRM label parameters:

1. Clarity - After some head-scratching and detective work, we think we
understand their purpose. We're assuming that:

a. These labels are simply 16-bit masks that are logically ANDed onto the
received TCAP transaction ID, starting at the "Start" bit.

b. If the result of the AND operation exactly matches the "Label" field,
then the message is sent to the ASP that registered for this label via the
ASPAC msg.

c. An ASP that registers a label will be sent only those TID-bearing
messages that match its label.

d. An ASP that does not register a label may be sent any TID-bearing
message.

If these assumptions are correct, please state them explicitly in the
relevant sections of the draft(3.10.15, 3.10.16, 4.7.2.1 and 4.7.3.1). If
not, please clarify. It's not enough to say, as in 4.7.3.1, "the SG extracts
the label".

2. Redundancy - The label values are fixed length (16 bits). So why do we
need both a "Start" and an "End" position for applying the mask? One or the
other would seem to be enough.

3. Simplicity - Why bother with a partial-sized mask at a specified "start"
bit. Why not just specify a "full-sized" 32-bit (TID) or 23-bit (DRM) mask?

4. Contradictions - Section 4.7.2.1 states that "All the ASPs within the AS
_must_ specify a unique label at a fixed position in the TID or DRN
parameter." The "must" here contradicts that fact the the TID and DRM
parameters are listed as Optional in the ASPAC msg. We're guessing that the
intention here is either:

a. "If at least one of the ASPs within an AS specifies a label, then all the
ASPs within the AS must specify a unique label at a fixed position in the
TID or DRN parameter."

or

b. "All of the labels specified by the ASPs within an AS must start at a
fixed position in the TID or DRN parameter."

or maybe

(a) AND (b). Please clarify.

Barry Nagelberg

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 18 Feb 2004 14:16:43 -0700

Barry,

Barry Nagelberg wrote:                                                               (Wed, 18 Feb 2004 15:26:12)
> not, please clarify. It's not enough to say, as in 4.7.3.1, "the SG extracts

That's my understanding.  Some clarity would be good.  Can you provide text?

> other would seem to be enough.

The label does not have to be 16 (significant) bits.

> bit. Why not just specify a "full-sized" 32-bit (TID) or 23-bit (DRM) mask?

I don't know of any reason not to allow specification of a full 32-bit mask
either.

> (a) AND (b). Please clarify.

I think we meant, "The ASPs within the AS specifying a label, must specify a 
unique label at a fixed position in the TID or DRN parameter."  The point
being that no two labels (optionally specified) can overlap.

That said, the label mechanism is still broken, as detailed in previous
threads.  As it is an optional procedure, it might get fixed or fall out of
use in the future.

See draft-bidulock-sigtran-loadsel-02.pdf  I also have a session registration
draft (never submitted) that provides a superior approach to the same problem.
If someone is interested I will sumbit it.

--brian

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

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From: "Barry Nagelberg" <[email-masked]>
Date: Wed, 18 Feb 2004 17:21:43 -0500

Brian,

Thanks for the clarifications. Regarding your comments:

1. Suggested text - We already provided it. Please see #1 below.

2. Length of mask - Section 3.10.16 states that the length of the mask is 16
bits. No where else in the draft is it mentioned that not all of the bits
are significant. If you are contending that not all of the bits are
significant, then this is another aspect that must be clarified.

3. I agree with you that the label mechanism, as currently specified, is
broken. However it is NOT optional, because there is no mechanism specified
through which the SGP can indicate to the ASP that it doesn't support the
TID Label parameter in the ASPAC message (there is no "Unsupported
parameter" error code). Thus SUA itself is also broken. So the label
mechanism must either be fixed or removed.

Barry Nagelberg

> -----Original Message-----
> From: Brian F. G. Bidulock [mailto:[email-masked]]
> Sent: Wednesday, February 18, 2004 4:17 PM
> To: Barry Nagelberg
> Cc: SIGTRAN Mailing List; Seamus Gilchrist
> Subject: Re: [Sigtran] SUA v16: TID and DRM labels
>
>
> Barry,
>
> Barry Nagelberg wrote:

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 18 Feb 2004 16:57:17 -0700

Barry,

I think the decision at last call was that it would neither be fixed nor
removed.  Perhaps John an Lyndon could shed some light on the possibility
of doing either at this late date.

--brian

Barry Nagelberg wrote:                                                               (Wed, 18 Feb 2004 17:21:43)

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