Subject: Re: AIW5 Capabilities Exchange Proposal (fwd)

From: Frank Bordonaro <[email-masked]>
Date: Wed, 3 Aug 94 15:27:20 PDT

> > 
> > I agree with Scott, DLSw should allow the setting of any SAP within this CV
> > Also, I was under the impression that a 16 byte bit vector was agreed upon
> > at AIW5 for the structure of this vector. I will include what I understand
> > that to look like.
> > 
> >         +---------------------------------------------------------------+
> >         |   SAP List Support (X'86') Control Vector                     |
> >         |                                                               |
> >         |       The SAP List Support control vector identifies support  |
> >         |       for SAPs by the sending Data Link Switch. Each bit in   |
> >         |       the SAP control vector data field represents a SAP as   |
> >         |       defined below. This vector is required.                 |
> >         |                                                               |
> >         +---------------------------------------------------------------+
> > 
> >         Offset  Length  Value       Contents
> >         ------  ------  -----       --------
> >            0       1    X'12'       Length of the SAP List Support structured
> >                                     subfield
> >            1       1    X'86'       key = X'86' that identifies this as the
> >                                     SAP List Support structured subfield
> >           2-17    16                the 16-byte bit vector describing all
> >                                     even numbered SAP's enabled.
> > 
> >                                     Each Bit within the 16 byte bit vector will
> >                                     indicate whether an even numbered SAP is
> >                                     enabled (b'1') or disabled (b'0').
> > 
> >                                     Each Byte within the 16 byte bit vector
> >                                     will be numbered from 0 - F. (In the
> >                                     following 1 byte example x would be
> >                                     equal to the appropriate byte number.)
> > 
> >                                     bbbb bbbb
> >                                     |||| ||||
> >                                     |||| |||SAP 'xE' enabled or not
> >                                     |||| |||
> >                                     |||| ||SAP 'xC' enabled or not
> >                                     |||| ||
> >                                     |||| |SAP 'xA' enabled or not
> >                                     |||| |
> >                                     |||| SAP 'x8' enabled or not
> >                                     ||||
> >                                     |||SAP 'x6' enabled or not
> >                                     |||
> >                                     ||SAP 'x4' enabled or not
> >                                     ||
> >                                     |SAP 'x2' enabled or not
> >                                     |
> >                                     SAP 'x0' enabled or not
> 
> Why did you only list the EVEN saps above? This does not facilitate the
> setting of ANY sap by this CV, as Scott suggested. Your idea has the same 
> problem as the original proposal if it doesn't include all saps.

I would like to restate this. I think we should recognize the group bit 
in the dsap, to cover all future possibilities. At this point, this may be
an overkill, so just filtering even saps is also acceptable to me. The
responses on the mailer should decide the issue. 
Thanks.
Frank B.

> If we go this route where DLSw can support any sap, then we need to make 
> this a 32 byte vector. I originally wrote the proposal up this way, but 
> thought sending a 32 byte vector for sap support was extreme. It now seems 
> that if we don't allow for all cases, we'll likely run into trouble later. 
> 
> So, to set the base for continued discussion, the new proposal is
> a 32 byte vector where the bits are numbered left to right (as above).
> I think the RIG rules are that a proposal needs to be on the table for
> 3 weeks, before it can be resolved. Start the clock.
>

---

From: [email-masked] (Scott Barvick)
Date: Thu, 4 Aug 1994 14:09:12 -0400 (EDT)

There is definitely a tradeoff between full featured and simplicity.
It doesn't seem to be a real issue for current implementations so I would
accept just the even SAPs now with the possible future addition of the 
'Odd SAP Support CV' to complete the capability in the future, if
necessary.  Having 2 CVs would only be an extra 2 bytes, and we may
never have to worry about it.  We can use the existing CV 
definition and move on.  Objections?

Scott
[email-masked]