<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Dave,<div class=""><br class=""></div><div class="">Thanks for writing this up, it's an interesting read.</div><div class="">I agree with you on the topic of multicast. My implementation sends</div><div class="">everything unicast, with the exception of Hellos. I'm interested in</div><div class="">working on a way to allow unicast Hellos. I read your thoughts here:</div><div class=""><a href="https://github.com/dtaht/rabeld/blob/master/babel_unicast_hello.md" class="">https://github.com/dtaht/rabeld/blob/master/babel_unicast_hello.md</a></div><div class=""><br class=""></div><div class="">and was thinking that we might be able to make this even simpler,</div><div class="">by adding a new "I support unicast Hellos" bit in the IHU Reserved field.</div><div class="">That way when a node appears on a link, they send a multicast Hello,</div><div class="">and get IHUs in response. If all the IHUs have this bit, then the router</div><div class="">can go into unicast Hello mode. Similarly, when a node sees a new</div><div class="">neighbor, it sends it an IHU with this bit and if it receives a unicast</div><div class="">Hello from that node it knows they are supported, otherwise falls back</div><div class="">to multicast. You could then have different intervals for multicast and</div><div class="">unicast Hellos, with the multicast one being potentially much higher.</div><div class=""><br class=""></div><div class="">This proposal stays in the spirit of current Hellos as a measure for</div><div class="">packet loss rate. If as you describe this isn't a great metric, we</div><div class="">could take this thought process even further and simply get rid of</div><div class="">Hellos for link quality estimation. You would still have multicast Hellos</div><div class="">to detect new peers, but you can estimate by-directional reachability</div><div class="">simply by noticing of you receive any Babel packet from a host, and</div><div class="">IHU for the reverse direction. This makes particular sense if you were</div><div class="">able to query your link-layer for information on how many</div><div class="">retransmissions are required on average to reach that host, and what</div><div class="">rate the Wi-Fi chip is operating at.</div><div class=""><br class=""></div><div class="">Thoughts?</div><div class="">David</div><div class=""><br class=""></div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Dec 12, 2016, at 09:25, Dave Taht <<a href="mailto:dave.taht@gmail.com" class="">dave.taht@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">I've long been testing a few out of tree patches for babel and long<br class="">have had the intent to try a few more once the first phase of the<br class="">make-wifi-fast work was completed - which it mostly is, so far as lede<br class="">is concerned ( <a href="https://lwn.net/Articles/705884/" class="">https://lwn.net/Articles/705884/</a> ) - and babel-1.8<br class="">stablized.<br class=""><br class="">I wrote up some of my thinking then in:<br class=""><br class=""><a href="https://github.com/dtaht/rabeld/blob/master/rabel.md" class="">https://github.com/dtaht/rabeld/blob/master/rabel.md</a><br class=""><br class="">back when we were having powersave issues affecting multicast (which I<br class="">hope is now fixed), but I've partially deployed the "mo' unicast"<br class="">patch around my testbed with no ill results.<br class=""><br class="">Another thing that has come up a lot lately is the default gateway<br class="">failing for some reason or another, tighter integration with<br class="">babel-pinger might help.<br class=""><br class="">And lastly, I had a chance to look at some packet captures from the<br class="">wlan-slovenia network, which is essentially flat, and is sending 14<br class="">packets worth of route information on a regular basis. Finding ways to<br class="">attenuate and create covering routes, and make DV more DV would be<br class="">nice.<br class=""><br class="">I'd also written up some partially crazy thoughts towards a unicast<br class="">hello extension in the same repo.<br class=""><br class="">-- <br class="">Dave Täht<br class="">Let's go make home routers and wifi faster! With better software!<br class="">http://blog.cerowrt.org<br class=""><br class="">_______________________________________________<br class="">Babel-users mailing list<br class="">Babel-users@lists.alioth.debian.org<br class="">http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/babel-users</div></div></blockquote></div><br class=""></div></body></html>