Subject: Re: [Roll] Ack the DAO?

From: "Roger Alexander" <[email-masked]>
Date: Thu, 1 Apr 2010 17:46:49 -0400

Hi Pascal,

There will need to be some additional specification work to complete the picture. Nonetheless, the basic idea for the support of DAO ACKs stems from the fact that in large urban networks there are long periods of time over which network connectivity for large segments of the network may remain largely stable. Under those circumstances it would be beneficial for improved scalability to maintain cache coherency without the need to repeat unchanged state information between nodes. The idea is to be able to limit the amount of information that is sent between a node and its DAO Parents by providing implicit updates and sending specific information only when a change in routing database or connectivity occurs. A la RFC 2091 (Triggered RIP), if a router has exchanged all routing information with its Parent and some routing information subsequently changes, only the changed information needs to be sent to the Parent. The DAO ACK will be an element to support this type of mechanism.

Roger

From: Pascal Thubert (pthubert) [mailto:[email-masked]] 
Sent: Tuesday, March 30, 2010 1:49 AM
To: Roger Alexander; [email-masked]
Subject: RE: [Roll] Ack the DAO?

Hi Roger:

This looks interesting. Could you please refine your ideas on this subject? 

Pascal

From: Roger Alexander [mailto:[email-masked]] 
Sent: Wednesday, March 10, 2010 2:58 PM
To: Pascal Thubert (pthubert); [email-masked]
Subject: RE: [Roll] Ack the DAO?

Hi Pascal, WG,

I do think DAOs should be acknowledged. From the perspective of a system employing ‘storing’ nodes, there will be additional benefits in terms of optimizations that reduce the overhead of exchanged state information if the DAO messages are reliably transmitted. This may require some additional update to the DAO message structure but will open the possibility for implementations to further reduce RPL overhead.

Roger

From: [email-masked] [mailto:[email-masked]] On Behalf Of Pascal Thubert (pthubert)
Sent: Wednesday, March 10, 2010 5:39 AM
To: [email-masked]
Subject: [Roll] Ack the DAO?

WG:

RPL 07 provides means for a node to advertise some reachability using a DAO mechanism. The DAO can be triggered by the node to match its own needs. It can also be stimulated by a parent, by incrementing the DTSN, or by the root, by setting the T bit that causes the DTSN increment to span the whole DODAG.

The DTSN was added as a replacement to a single bit because, due to the nature of an LLN, we thought that the bit might be lost whereas a DTSN increment must be seen at some point. But the other way around, the DAO message is not acknowledged so a node might not obtain the service that it expects, and a route propagation might be inappropriately delayed.

So the simple question is, should we make the DAO a bit more reliable by adding an ack? 

	

Pascal Thubert
Engineer.software Engineering
Product Development
 <mailto:[email-masked]> [email-masked]
Phone: +33 4 9723 2634
Mobile: +33 6 1998 2985

Cisco Systems France
Village d'Entreprises Green Side
400 Avenue de Roumanille 
Batiment T 3 
06410 
BIOT - SOPHIA ANTIPOLIS
France
 <http://www.cisco.com/global/FR/> Cisco.com

Think before you print.Think before you print.

Cisco Systems France, Société à responsabiité limitée, Rue Camille Desmoulins – Imm Atlantis Zac Forum Seine Ilot 7 92130 Issy les Moulineaux, Au capital de 91.470 €, 349 166 561 RCS Nanterre, Directeur de la publication: Jean-Luc Michel Givone, For corporate legal information go to:
http://www.cisco.com/web/about/doing_business/legal/cri/index.html