[Tinyos-host-mote-wg] Discussion

[David Gay]

Ben Greenstein wrote:
> On Apr 11, 2005 5:30 PM, Philip Levis <pal at cs.berkeley.edu> wrote:
>>On the notion of connection-based versus connectionless protocols. The
>>distinction lies in how much state you can assume the other side
>>maintains. In a connectionless protocol, you need to include additional
>>state in every packet, state which in a connection-oriented protocol
>>would be maintained as part of the connection.
> 
> Yes. Another way to look at this problem is identify what information
> each device needs to know about its peer:
> - whether or not the peer is alive
> - sequence numbers for sliding window reliability over serial
> - device characterizations (e.g., micaz or mica2)
> - protocol characterizations (e.g. no compressed headers)
> Given these requirements, I am wholeheartedly in favor making the
> datalink layer (the sum of hdlc and ppp) connection-oriented.

Your list is not very strong support for that, though:
- peer alive: connection-oriented doesn't help
- protocol characteristics: this is an artifact of using ppp

So that only leaves
- device characteristics: at most a couple of bytes
- reliability: I think the connection is actually providing a known 
starting point (e.g., after the open, I know the window is fully 
available - without the known starting point you would have a potential 
race when receiving a message indicating N window slots available just 
after sending a message), not really saving space (this is in slight 
contradiction to Phil's point of course ;-))

David