Sorry, too much working on the implementation side of NHDP/OLSRv2 in the last years... should have thought a bit more about the reply before sending it.
Yes, you are correct that RFC6130 does not contain the description of the link metric... it only contains a rough EWMA based "link quality" hysteresis that switches on and of links. I don't even think the algorithm defined in the RFC is really useful (but its easy to plug in a different one because the Link Quality calculation and decision is just local). I was thinking about the Link Metric NHDP extension defined in RFC7181 (which can easily be used without using the OLSRv2 routing), which is based on "Incoming/Outgoing Link Metric" values. (in my implementation I put the whole Link Metric and MPR code into NHDP to make them usable without OLSRv2) Henning Rogge On Tue, Mar 3, 2015 at 12:28 AM, Curtis Villamizar <[email protected]> wrote: > Henning, > > You cut the following off the top of your reply. > >> > The Neighborhood Discovery Protocol (RFC 6130) has a similar >> > mechanism... each node collects local link quality information and >> > then shares them from time to time with all neighbors, which means >> > everyone knows about both directions of a link. >> > >> > Henning Rogge >> >> >> RFC 6130 uses probes (hello message success rate). > > Cutting this off makes a big difference. See below. > > In message > <CAGnRvup-F4_A1-sHkh3EWRgrX=iuthbdmjzz+xk_g+7bm+e...@mail.gmail.com> > Henning Rogge writes: >> >> On Sun, Mar 1, 2015 at 11:14 PM, Curtis Villamizar >> <[email protected]> wrote: >> > RFC 6130 uses probes (hello message success rate). >> >> No, it does not... at least not for calculating the link metric. > > The discussion was the quality measurement. The quality measurement > uses hello message success rate. See section 14 in RFC 6130. > > The discussion was not link metrics. You chopped the prior discussion > when quoting the one sentence above. Below I describe the why RFC > 6130 Link Quality is nothing like LQM. > >> > For example: If an AP sends 100 packets a second to a neightbor and 5 >> > drop it would be better to send one LQM packet and know that loss is >> > 5% rather than have to send 100 hello packets in addition to the 100 >> > data packets to reliably know that loss is 5%. (In MPLS it could be a >> > billion packets between LM packets). >> > >> > LQM does not rely on a count of probe packet success. Please reread >> > what I sent earlier or read about PPP LQM or MPLS-TP LM OAM. >> > >> > Please compare RFC 6130 section 14.2 (Basic Principles of Link >> > Quality) >> >> "Link quality" and "Link metric" are two different kind of things for >> NHDP/OLSRv2. >> >> Link quality is used for a hysteresis mechanism that can make a link >> symmetric/asymmetric. >> >> Link metric (as defined in RFC 7181) is used for path selection. >> >> > with RFC 1989 and RFC 6375. In RFC 6375 look at Section 2.2 >> > (Packet Loss Measurement) and Section 3.1 (Loss Measurement Message >> > Format). RFC 6130 has no comparable mechanism. >> >> RFC6130 (NHDP) and RFC 7181 (OLSRv2) define the incoming link METRIC >> calculation as an external process. It can be anything, as long as it >> gives you a dimensional link cost in the right range. >> >> I admit the splitup between RFC6130 and RFC7181 is a bit confusing... >> >> Henning Rogge > > I know the difference between link quality and link metric. > > You just jumped from ND to OLSRv2 for MANET. RFC 7181 does not > preclude using a LQM-like mechanism, but neither RFC 6130 or RFC 7181 > define such a mechanism. > > The discussion was regarding doing something like LQM and three > messages ago you stated that RFC 6130 already had something like LQM. > Neither RFC 6130 or RFC 7181 define a mechanism anything like LQM. > > Curtis _______________________________________________ homenet mailing list [email protected] https://www.ietf.org/mailman/listinfo/homenet
