[Roll] Transit vs. Target in P DAO

["Pascal Thubert (pthubert)" <[e-mail]>]

Dear all ;

Say we are building a serial path using P DAO: in that case,  we are building a tunnel from the Track Ingress to the Track Egress, where the Track is signaled in the packet by the local RPLInstanceID in the RPI and the destination IPv6 address. The outer header may also have a SRH in case of non storing P DAO.

In the current version of the P DAO draft we use a RPL Target Option (RTO) to signal the Track Egress and the new Via options (CMOs) to indicate the hops. But say we do not want to reach the Tunnel egress but one of its children or siblings. How can we signal that these guys are reachable over the tunnel?

Proposal A)

If we want to be able to signal that, it could be more consistent with RPL to use:
- one or more RTOs to indicate the targets of the route, can be any of the children and siblings
- Exactly one Transit Information Option (TIO) to indicate the tunnel egress
- then one VIO or one or more SRVIOs (as we currently do)

The result would be that the Track terminates at the "Parent" indicated in the TIO but can be used to reach any of the children and siblings indicates as targets

Proposal B)

Maybe we want to signal that only certain DetNet Flows should be placed in the Track. In that case, The RTO is not sufficient and we'd need the 6tuple. If we take that path, we'd need to create a new Flow option that is a Flow descriptor, in which case we'd get
- one or more Flow Options to indicate which flows  are encapsulated in the Track
- Exactly one RTO  (as we currently do) OR Exactly one TIO (as in Proposal A) to indicate the tunnel egress
- then one VIO or one or more SRVIOs (as we currently do)


What do you guys think?

Pascal