Re: [Pana] Switching to direct communication [was Re: PANA relay draft]

["Alper Yegin" <[e-mail]>]

I think this text is fine.

 

From: Robert Cragie [mailto:[e-mail]] 
Sent: Wednesday, December 01, 2010 3:51 PM
To: Alper Yegin
Cc: 'Yoshihiro Ohba'; 'Rafa Marin Lopez'; [e-mail]; 'Ralph Droms'; 'Samita Chakrabarti'; 'Paul Duffy (paduffy)'
Subject: Re: Switching to direct communication [was Re: PANA relay draft]

 

Maybe I'm missing something but switching to direct communication has nothing to do with a *change* in the PAA address. I would suggest the following:

"If direct IP routing becomes available[1] and the PaC is notified about the PAA's[2] IP address using an out-of-band mechanism that is not specified in this document, the PaC may choose to directly communicate with the PAA without use of the relay operation.  The PaC[3] IP address update procedure defined in [RFC5191] may additionally[4] be performed to switch to non-relay operation, using the directly reachable IP address of the PAA."

[1] Removed ZigBee IP reference
[2] "the change of PAA's" -> "the PAA's"
[3] Added PaC as per Alper's suggestion
[4] Added "additionally" as this is independent from getting the PAA address

Comments?

Robert Cragie (Pacific Gas & Electric)

Gridmerge Ltd.
89 Greenfield Crescent,
Wakefield, WF4 4WA, UK
[phone]
[phone]
http://www.gridmerge.com <http://www.gridmerge.com/> 


On 30/11/2010 9:20 PM, Alper Yegin wrote: 

Looks good to me.
 
One minor update:
 
"The IP address update procedure" --> "PaC IP address update procedure"
 
 
Alper
 
 

-----Original Message-----
From: Yoshihiro Ohba [mailto:[e-mail]]
Sent: Tuesday, November 30, 2010 3:52 AM
To: Alper Yegin
Cc: 'Rafa Marin Lopez'; [e-mail]; 'Ralph Droms';
[e-mail]; 'Samita Chakrabarti'; 'Paul Duffy
(paduffy)'
Subject: Re: Switching to direct communication [was Re: PANA relay
draft]
 
OK.  How about the following change?
 
Current text:
 
"If direct IP routing becomes available (e.g., after the successful
PANA authentication as in the case of Zigbee IP), the PaC may
choose to directly communicate with the PAA without use of the relay
operation.  The IP address update procedure defined in
[RFC5191] may be performed to switch to non-relay operation."
 
Propose text:
 
"If direct IP routing becomes available (e.g., after the successful
PANA authentication as in the case of Zigbee IP) and the PaC is
notified about the change of PAA's IP address using an out-of-band
mechanism that is not specified in this document, the PaC may choose
to directly communicate with the PAA without use of the relay
operation.  The IP address update procedure defined in [RFC5191] may
be performed to switch to non-relay operation, using the directly
reachable IP address of the PAA."
 
Yoshihiro Ohba
 
(2010/11/29 21:10), Alper Yegin wrote:

Rafa,
 

El 26/11/2010, a las 08:21, Alper Yegin escribió:
 

Let me create a new thread on this specific topic.
 
It has been identified that switching from relay to direct
communication requires not only change of PaC's address but also
change of PAA's address.
 
But RFC 5191 supports change of PaC's address for a given PANA

session

but does not support change of PAA's address.

 
Yes, RFC 5191 has an explicit support for that.
 
 

So it seems that switching to direct communication requires to go
through a full PANA authentication.

 
I don't think that's necessary at all.
 
If the PaC learns another (or new) IP address of the PAA by some

out-

of

scope mechanism, then it can start using that IP address. And

that's

the

case in Zigbee.

 
[Rafa] What I believed is that a new PANA authentication was

necessary

when you switch the PAA's interface, as Yoshi has mentioned. It does
not mean that it is the best option of course, but what happens is

that

there is no support for PAA's address change. I believe this

scenario

was not considered in RFC 5191.

 
We didn't envision this scenario. Hence RFC 5191 is "silent" about

it.

In other words, there is no explicit facility to realize that (PAA IP
address change), and there is no prohibition against it either. Which

means,

if some implementation/SDO/deployment can figure out a way to enable

that

w/o breaking the RFC, it's OK. And that's the case with this Zigbee

Alliance

usage.
 
 

In the same way that "In order to
maintain the PANA session, the PAA needs to be notified about the
change of PaC address.", I would expect a mechanism saying that: "In
order to maintain the PANA session, the PaC needs to be notified

about

the change of PAA address."

 
We can say something to that affect in the relay I-D.
 
Alper
 
 
 
 

 
 

 
Alper
 
 
 
 

So if we mention "direct IP routing MAY be available" then we may

also

need to mention that "switching to direct communication requires a
full PANA authentication using the new PaC's and PAA's addresses."
 
What do you think?
 
Yoshihiro Ohba
 
 
(2010/11/24 21:32), Alper Yegin wrote:

 
[Rafa] In my opinion, after the successful PAA authentication, I
believe that it would be better that PaC does not require the

PRE

anymore. In other words, the PaC and the PAA know each other.

Moreover

I assume that after the successful PAA authentication the PaC

will

be

able to contact directly the PAA without the assistance of the

PRE.

If

these assumptions are reasonable, there will not be PAA-initated
messages that go through the PRE.

 
I think this spec shall not mandate or prohibit use of PRE after

the

first

successful PANA auth. Spec shall allow both, and the consumers

(deployments,

architectures) shall decide.
 

  If direct IP routing becomes available (e.g., after the

successful

  PANA authentication as in the case of Zigbee IP),
 
[Rafa]. Is the PRE informed by the PAA?. If it is, how?. In

other

words, how is this enabled after a successful PANA

authentication?

 
The PRE is not informed by the PAA when direct IP routing

becomes

available.
 
[Rafa] I mean that it is mentioned that direct IP routing is

available

, how is this enabled after a successful PANA authentication? is

the

PaC enabled to use a non link-local IPv6 address?.

 
I think the spec shall say "direct IP routing MAY be available".

In

the

specific case of zigbee, PaC receives RA and configures a global

IPv6

address. Such details belong to zigbee spec.
 

On the other hand, what entity is acting as EP?.
 

 
An EP may reside in the PRE, or it could be a separate entity

from

the PRE.

 

the PaC may choose
  to directly communicate with the PAA without use of the

relay

  operation.
 
[Rafa] However, it has been said that PaC that "From the PaC's
perspective, the PRE appears as the PAA."
This sentences seems to mean that PaC knows that it is talking

with

a relay first.

 
The PaC may not know that it is talking with a relay first.

OTOH,

the PaC may know, after successful PANA authentication, that it

was

talking with a relay, by using some out-of-band mechanism.  But

this

does not mean that switching to direct communication is needed.

The

point here is that we try to describe possible cases as much as
possible.
 

 

The IP address update procedure defined in [RFC5191] may
be performed to switch to non-relay operation.
 
[Rafa] Who is sending this notification?

 
The notification is generated locally by the node that has

updated

an

IP address.
 
[Rafa] What is that node? the PAA? the PaC? both?. I mean to

switch

to

non-relay operation, under PaC point of view the PAA is

switching

the

IP address (PaC thought the PAA was the PRE but now it is the

real

PAA)

 
That's right. Both PaC's and PAA's IP address are changing for

the

given

PANA session.
 

 
 

 
-------------------------------------------------------
Rafael Marin Lopez, PhD
Dept. Information and Communications Engineering (DIIC)
Faculty of Computer Science-University of Murcia
30100 Murcia - Spain
Telf: [phone] Fax: [phone] e-mail: [e-mail]
-------------------------------------------------------