Re: [manet] Reactive Protocol Situation

On Nov 5, 2012, at 9:56 AM, Philip Levis wrote:

On Nov 4, 2012, at 11:21 PM, Henning Rogge wrote:

On Mon, Nov 5, 2012 at 2:38 AM, JP Vasseur (jvasseur)
<jvasseur@cisco.com<mailto:jvasseur@cisco.com>> wrote:
JP> We all agree, with a a non subtle nuance. I never said that reactive
routing was a bad idea. These protocol are very useful.
They are just ill-suited to LLNs.

At least that is your personal opinion. We got this, no need to repeat it again.

Henning Rogge

Henning,

At this point, I'm unsure what the difference between "proactive" and "reactive" is. I'm going to interpret "reactive" as "uses scoped floods to discover routes." That is, route request, route reply, etc. If I'm mistaken, then my comment below might be off the mark.

There's a lot of experimental evidence supporting the claim that using floods or scoped floods to discover routes is ill-suited to low-power and lossy networks (LLNs). This is due to the low-power requirement. In low-power wireless networks, broadcast packets usually cost much more to transmit than unicast ones. This is one of the reasons why RPL uses a Trickle timer to regulate its beaconing interval, so that if the current routes are operating well the broadcast rate approaches zero. Requiring a scoped flood every time a route breaks or is needed can be very costly.

If you want, I can walk you through the issues and a bibliography of low-power link layer and protocol designs. There's about a decade of work. If I were to recommend 3 papers to explain the issues and tradeoffs low power wireless introduces, then I'd suggest B-MAC (Polastre, SenSys 2004), X-MAC (Buettner, SenSys 2006) and A-MAC (Dutta, SenSys 2010). For protocol design, 3 papers I'd suggest Dozer (Burri, IPSN 2007), CTP (Gnawali, 2009), and a complete low power IP layer that greatly informed RPL's design (Hui, SenSys 2008).

I realize there are a lot of opinions on these topics. But there's thankfully also a lot of science and engineering. Let's not let the former get in the way of the latter.

Fully agreeing with Phil.

For the ones interested, please also refer to all tickets opened during the discussion about the design of routing protocol for LLN during the course
of 4 years of work in ROLL. There is also quite a bit of background in RFC6550 on the fundamental design principles of RPL for LLN. Last but not
least, you may all also be interested in the 4 uses case requirements of routing protocols for LLNs:

RFC 5548<http://datatracker.ietf.org/doc/rfc5548/>
(draft-ietf-roll-urban-routing-reqs<http://datatracker.ietf.org/doc/draft-ietf-roll-urban-routing-reqs/>)       Routing Requirements for Urban Low-Power and Lossy Networks     2009-05 RFC 5548 (Informational)                        Adrian Farrel
RFC 5673<http://datatracker.ietf.org/doc/rfc5673/>
(draft-ietf-roll-indus-routing-reqs<http://datatracker.ietf.org/doc/draft-ietf-roll-indus-routing-reqs/>)       Industrial Routing Requirements in Low-Power and Lossy Networks 2009-10 RFC 5673 (Informational)                        Adrian Farrel
RFC 5826<http://datatracker.ietf.org/doc/rfc5826/>
(draft-ietf-roll-home-routing-reqs<http://datatracker.ietf.org/doc/draft-ietf-roll-home-routing-reqs/>) Home Automation Routing Requirements in Low-Power and Lossy Networks    2010-04 RFC 5826 (Informational)
Errata<http://www.rfc-editor.org/errata_search.php?rfc=5826>                    Adrian Farrel
RFC 5867<http://datatracker.ietf.org/doc/rfc5867/>
(draft-ietf-roll-building-routing-reqs<http://datatracker.ietf.org/doc/draft-ietf-roll-building-routing-reqs/>) Building Automation Routing Requirements in Low-Power and Lossy Networks        2010-06 RFC 5867 (Informational)                        Adrian Farrel

Phil
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