Re: [homenet] homenet-babel-profile: determining link type
>> Should we really only suggest that the router dynamically probe the >> quality of wireless links? Or would it make sense to suggest dynamic >> probing of all links, because assuming the entire path between 2 >> routers uses a single physical layer technology may not be a good >> assumption? > I agree that is should probe all interfaces! Then you need to define suitable algorithms for non-WiFi interfaces. I'm open to collaboration, of course, since dynamically computed metrics is something that's close to my heart. (Somebody promised to send me some G.hn hardware at some point, but they must have forgotten.) > Some wires might be better than others; assume use of random joiners between > cat3,cat5,cat6 and chicken wire in the home. Babeld's wireless link quality estimation triggers around 5% packet loss; on WiFi, it only works because we're careful to send frames that are not protected by ARQ -- after ARQ, the loss rate is way below that, even on dodgy links. You're not going to get loss rates that over chicken wire (unless you've got really bad quality chicken wire). > (a booth at N+I back in ~2000 or something had a very nice GbE over > barbed wire demo) Somewhat charged politically ;-) -- Juliusz ___ homenet mailing list homenet@ietf.org https://www.ietf.org/mailman/listinfo/homenet
Re: [homenet] homenet-babel-profile: determining link type
STARK, BARBARA Hwrote: > Should we really only suggest that the router dynamically probe the > quality of wireless links? Or would it make sense to suggest dynamic > probing of all links, because assuming the entire path between 2 > routers uses a single physical layer technology may not be a good > assumption? I agree that is should probe all interfaces! Some wires might be better than others; assume use of random joiners between cat3,cat5,cat6 and chicken wire in the home. (a booth at N+I back in ~2000 or something had a very nice GbE over barbed wire demo) -- Michael Richardson , Sandelman Software Works -= IPv6 IoT consulting =- signature.asc Description: PGP signature ___ homenet mailing list homenet@ietf.org https://www.ietf.org/mailman/listinfo/homenet
Re: [homenet] homenet-babel-profile: determining link type
>REQ6: a Homenet implementation of Babel SHOULD distinguish between >wired and wireless links ; if it is unable to determine whether a link >is wired or wireless, it SHOULD make the worst-case hypothesis that >the link is wireless. It SHOULD dynamically probe the quality of >wireless links and derive a suitable metric from its quality >estimation. The algorithm described in Appendix A of RFC 6126 MAY be >used. > Some older powerline technologies perform worse than Wi-Fi. But since > powerline is "wired", this requirement suggests it would be preferred. Do you have a suggestion for better wording? I guess we could say "lossless wired links" and "potentially lossy links". I'll think about it. > Also, it's not uncommon to use Wi-Fi to Ethernet or powerline bridges in > home networks. A router attached to Ethernet that is subsequently > bridged to Wi-Fi would look to the router like a wired link. Yes, that's a problem for Babel in general, not just for Homenet. It is impossible to reliably determine the layer-2 topology. There are two factors that mitigate the issue: 1. usually, there is a wireless bridge on just one side of a link; if the link is being treated as wireless on the other side, we still end up with a reasonable metric; 2. powerline links are not usually laid up in places where they are redundant; if there's a powerline, it's the only path, and so the metric doesn't matter in the first place. > Should we really only suggest that the router dynamically probe the > quality of wireless links? We only have implementation experience with three categories of links -- lossless, wireless, and tunnels. If we are to suggest a strategy for powerline, we need to do more research. We also need evidence that it makes a difference. > Or would it make sense to suggest dynamic probing of all links, because > assuming the entire path between 2 routers uses a single physical layer > technology may not be a good assumption? Link-quality estimation slows down convergence, so I think we should only suggest it where it makes a difference. For it to make a difference, you need to satisfy two conditions: (1) variable quality links that can be measured and (2) sufficiently diverse paths so that the metric can make you choose different paths. It's easy to get the two to happen with wireless links, much more difficult with powerline. If you have evidence otherwise, I'm interested. -- Juliusz ___ homenet mailing list homenet@ietf.org https://www.ietf.org/mailman/listinfo/homenet
Re: [homenet] homenet-babel-profile: determining link type
Hi Barbara, > Should we really only suggest that the router dynamically probe the quality > of wireless links? Or would it make sense to suggest dynamic probing of all > links, because assuming the entire path between 2 routers uses a single > physical layer technology may not be a good assumption? Good point. My gut feeling is that the percentage of cases where that assumption would be wrong is small but significant enough that we should consider probing all links. Anybody with better (=any) data? Cheers, Sander ___ homenet mailing list homenet@ietf.org https://www.ietf.org/mailman/listinfo/homenet