[net2-wg] collection stuff

[Philip Levis]

On Thu, 2006-04-20 at 16:50 -0700, Philip Levis wrote:

> Because the ForwardingEngine (FE) doesn't fill in the routing header
> until the packet is about to be sent, changing parents are not a big
> deal. I think that having the FE call a Send on the Routing Engine is
> unnecessary, and will just make the Routing Engine more complicated with
> little gain. 

On further thought, this is incorrect: the Routing Engine needs to have
an Send or AMSend. The reason for this is keeping track of payload
sizes. If I'm calling the RoutingEngine to calculate my payload size as
it might be adding headers, I can't then pass these values directly to
the link estimation component. 

E.g., imagine I have an app payload of 5 bytes, a network header of 3
bytes, a routing header of 2 bytes, and a le header of 2 bytes. The
sizes:

app payload to network: 5
network payload to routing: 8
routing payload to le: 10 
le payload to AM: 12

If my network layer calls routing to compute its payload, it will get 8.
If it passes this 8 to the LE layer, then it will cut off the last two
bytes.

Thoughts?

Phil