Subject: RE: Capability Negotiation for OCP

From: "Reinaldo Penno" <[email-masked]>
Date: Fri, 18 Apr 2003 07:59:37 -0700

Hilarie,

I do not follow you. PPP has configure-request, configure-response,
configure-nak and configure-rej to indicate that some capabilities are
not-acceptable and others the peer proposes a differente value. 

Anyway, I understand your proposal, but is awkard to put every single
acceptable value/range/strings for every capability. There might be
excessive overhead. On another point, how would you express preference of A1
over A2? I guess ((A1) or A2)?

Alex,

In order to leverage cached negotiations, we can ask every negotiation to
bear a identification number that is unique. Other negotiations can refer to
it. 

Regards,

Reinaldo

> -----Original Message-----
> From: The Purple Streak, Hilarie Orman [mailto:[email-masked]] 
> Sent: Thursday, April 17, 2003 6:15 PM
> To: [email-masked]
> Cc: [email-masked]
> Subject: Re: Capability Negotiation for OCP
> 
> 
> 
> PPP, IPSec and IKE use "offer, select".  The trick is to 
> spell out the complete set of selections at offer time.  
> Don't say (A1 or A2) and (B1 or B2) if (A1 and B2) is not 
> permitted - say instead
> 
> 	{ A2 and (B1 or B2) } or { A1 and B1}
> 
> Hilarie
>

---

From: Alex Rousskov <[email-masked]>
Date: Fri, 18 Apr 2003 10:44:43 -0600 (MDT)

On Fri, 18 Apr 2003, Reinaldo Penno wrote:

> In order to leverage cached negotiations, we can ask every
> negotiation to bear a identification number that is unique. Other
> negotiations can refer to it.

Yes, of course, but I am worried about potential security-related
attacks on such cached IDs as well as stale information. For example,
"Yeah, I am the same guy who just talked to you and gave you
negotiation ID 12313". I would like, ideally, to reuse an existing
scheme that allows that sort of optimization rather than invent our
own negotiation caching scheme. Are there other protocols that are
concerned with the cost of renegotiation across independent
transport connections?

Thanks,

Alex.

---

From: "The Purple Streak, Hilarie Orman" <[email-masked]>
Date: Fri, 18 Apr 2003 12:17:47 -0600

One of the PPP authors told me several years ago that PPP only used two
messages; perhaps it has changed.  IKE does use just the two messages.

Preference of A1 over A2 is expressed as (A1 or A2); preference of A2 over
A1 is expressed as (A2 or A1), just like compilers do it.

OPES will have a rule compiler, it can certainly have a preference
compiler.

Hilarie

---

From: "Reinaldo Penno" <[email-masked]>
Date: Sat, 19 Apr 2003 15:51:17 -0400

I do not like the fact that suddenly the order of the elements in the OR
statement is important. Yes, compilers can optimize based onjthe order, but
the final result is indepdendent of the ordering. We need to think about
something different.

We still  need  a way for the peer to say that it does not understand a
capability and/or does not agree with any value proposed (and actually
conveys which value it would have agreed). It can be on the naswr message,
but we need a special notation for that.

regards,

Reinaldo

----- Original Message -----
From: "The Purple Streak, Hilarie Orman" <[email-masked]>
To: "Penno, Reinaldo [BL60:0430:EXCH]" <[email-masked]>
Cc: <[email-masked]>
Sent: Friday, April 18, 2003 2:17 PM
Subject: RE: Capability Negotiation for OCP

> negotiation to