Date: Mon, 4 Jun 2012 01:27:37 -0500 (CDT)
From: Mukul Goyal <mukul@uwm.edu>
To: Joseph Reddy <jreddy@ti.com>
Message-ID: <515392394.582804.1338791257726.JavaMail.root@mail17.pantherlink.uwm.edu>
In-Reply-To: <2AA5AC69E924D149A8D63EB676AF87DB2CA3BB37@DLEE10.ent.ti.com>
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Cc: roll@ietf.org
Subject: Re: [Roll] P2P-RPL: Data-Option in P2P-DIO
Precedence: list

Hi Joseph

As Jakob mentioned there is no need for the origin to modify a data option =
during a route discovery. So I guess I can certainly make this change in P2=
P-RPL. Sequence numbers were introduced in Data option in response to Pasca=
l's question whether it was possible for the origin to modify the data opti=
on during a route discovery. I should have answered no right then. :(

I guess we could consider this item closed.

Thanks
Mukul

----- Original Message -----
From: "Joseph Reddy" <jreddy@ti.com>
To: "Mukul Goyal" <mukul@uwm.edu>, roll@ietf.org, "Jakob Buron (Jakob_Buron=
@sigmadesigns.com)" <Jakob_Buron@sigmadesigns.com>
Sent: Sunday, June 3, 2012 11:29:51 PM
Subject: RE: P2P-RPL: Data-Option in P2P-DIO


Hi Jakob,

If we agree to  remove the sequence numbers from the data option ( and, con=
sequently, require that the Origin must not modify the data-option during a=
 transmission ), that would be acceptable to me.

-Regards, Joseph


----- Forwarded Message -----
From: "Jakob Buron" <Jakob_Buron@sigmadesigns.com>
To: "Joseph' 'Reddy" <jreddy@ti.com>, "Mukul Goyal" <mukul@uwm.edu>
Cc: roll@ietf.org
Sent: Tuesday, May 29, 2012 8:24:03 AM
Subject: RE: P2P-RPL: Data-Option in P2P-DIO

Hi, please see my comments inline.

> -----Original Message-----
> From: roll-bounces@ietf.org [mailto:roll-bounces@ietf.org] On Behalf=20
> Of Reddy, Joseph
> Sent: Friday, May 25, 2012 11:08 PM
> To: Mukul Goyal
> Cc: roll@ietf.org
> Subject: Re: [Roll] P2P-RPL: Data-Option in P2P-DIO
>=20
> Hi Mukul,
>=20
> See response below...
>=20
> -Regards, Joseph
>=20
> -----Original Message-----
>=20
> [Joseph]
> Section 9.4
> Bullet 1:
> Under what conditions would a router receive the same DIO and a Data-=20
> Option with higher sequence number? I assume that only the Originator=20
> can include a Data-Option ? Same question also arises for section 9.5=20
> ( para
> 1 )
>=20
> [Mukul]
> Yes, only the origin can include a data option for delivery to the=20
> target(s). In theory, the origin might have newer data to convey to=20
> the
> target(s) while the route discovery is still going on. Sequence=20
> numbers accounts for that possibility. Note that Data option did not=20
> have a sequence number earlier (before the first LC). Then, Pascal=20
> raised the possibility what if origin changes the data option. How=20
> would intermediate routers and target know that this is the newer=20
> data? Hence, we introduced the sequence number.
>=20
> [Joseph]
> I don=E2=80=99t think the Origin should able to this. In fact, the Origin=
 must=20
> not make any changes to the contents of the DIO and retransmit it=20
> without updating the version number. If the Origin wants to send data,=20
> it should simply wait until the p2p route is setup and then use it.
>=20
> The whole idea of sending UDP Data messages in the ICMP message=20
> payload itself doesn=E2=80=99t seem quite right. It is also not simple fr=
om an=20
> implementation perspective to make this kind of cross layer interactions.
>=20
[Jakob]
I understand the concern about the Data Option and cross-layer interactions=
. I also believe that it is a sensible and necessary design choice for home=
 automation networks. Home automation frequently requires low-latency messa=
ges to be delivered to targets for which the originator has no route. An ex=
ample is a remote light switch that needs to control a relocated lamp. The =
fastest way to do that in a reactive routing scheme is to piggyback the dat=
a on the routing packets. The other option would be to use simple flooding,=
 with no trickle control, which would involve generating a huge number of p=
ackets. Piggybacking data on routing packets helps avoid generating extra p=
ackets.

Home automation networks do not need to update the Data Option while a disc=
overy is in progress. I am okay with removing the sequence numbers if they =
add too much complexity.

Best regards,
Jakob
>=20
>=20
>=20
>=20
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