Subject: [Roll] Changes in p2p-rpl-03

From: Mukul Goyal <[email-masked]>
Date: Sat, 14 May 2011 11:31:12 -0500 (CDT)

Hi all,

Here are the main differences between the new draft and the previous version:

1. Eliminated "route" constraints. The previous version supported two types of constraints: propagation constraints were to be applied by all the routers receiving a DIO whereas the route constraints were to be applied by only the target. The idea was to simplify the task of intermediate nodes that had to apply only the propagation constraints. However, there were issues with how to distinguish the two sets of constraints. Now, all the routers have to apply all the constraints. We can always mark some constraints as optional if we dont want all the nodes to apply them.

2. Similarly, eliminated the optional OCP from the Route Discovery Option. Now, the same OCP is to be used for DAG formation and route comparison.

3. Combined Source Route Option with Route Discovery Option. Now, both DIOs and DROs have to carry one Route Discovery Option. The Route Discovery Option allows carrying the target address and the addresses in the accumulated route in the compressed fashion.

4. DRO propagation: Previous version allowed lot of flexibility in sending DROs from the target to the origin. This would have certainly led to interoperability issues. This version allows just one way for DROs to travel: via link-local multicast along a route specified in the route discovery option contained in the DRO. Sending DROs via link-local multicast allows the DRO message to convey the completion of route discovery to nodes in the LLN (via the stop bit).

5. Route accumulation in DIO: Since the DRO is not going to travel using RH4, there was not much incentive to use RRH to accumulate the route travelled by a DIO. Since the DRO is going to travel along a route specified in the Route Discovery Option, it makes sense to accumulate the route travelled by a DIO in the Route Discovery Option itself. When the target generates a DRO, it can simply copy the Route Discovery Option from the DIO into the DRO.

6. Changes have been suggested to Trickle operation to meet the needs for low latency in route discovery while avoiding DIO storms. We will work with Trickle authors to see if we can achieve the desired results in a more compliant manner.

Thanks
Mukul