Re: [Babel-users] CRXN/DN42: interconnecting overlay networks with Babel and BGP
Hello! >> So if you're not careful you could end up in a situation where Babel >> maintains a loop-free forwarding graph, BGP maintains a loop-free >> forwarding graph, but there exists a loop that goes Babel -> BGP -> Babel. >> >We almost experienced such a situation as well. Bird >always prefers Babel over BGP, unfortunately. In BIRD, you can set the preference per route, this way you may prefer any route over any else. Maria ___ Babel-users mailing list Babel-users@alioth-lists.debian.net https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users
Re: [Babel-users] CRXN/DN42: interconnecting overlay networks with Babel and BGP
On Mon, 20 Feb 2023 16:51:52 +0100 Juliusz Chroboczek wrote: > > I think the answer should be that no matter how you mess with the metrics > > babel should still remain loop-free, right? > > Both Babel and BGP should remain loop-free whatever you do. However, when > you redistribute routes between protocols, there's no guarantee that the > union of the two graphs remains loop-free. > > So if you're not careful you could end up in a situation where Babel > maintains a loop-free forwarding graph, BGP maintains a loop-free > forwarding graph, but there exists a loop that goes Babel -> BGP -> Babel. > > -- Juliusz We almost experienced such a situation as well. Bird always prefers Babel over BGP, unfortunately. > > ___ > Babel-users mailing list > Babel-users@alioth-lists.debian.net > https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users -- Marek Küthe m...@mk16.de er/ihm he/him pgpMuY5mLR_2C.pgp Description: OpenPGP digital signature ___ Babel-users mailing list Babel-users@alioth-lists.debian.net https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users
Re: [Babel-users] CRXN/DN42: interconnecting overlay networks with Babel and BGP
> I think the answer should be that no matter how you mess with the metrics > babel should still remain loop-free, right? Both Babel and BGP should remain loop-free whatever you do. However, when you redistribute routes between protocols, there's no guarantee that the union of the two graphs remains loop-free. So if you're not careful you could end up in a situation where Babel maintains a loop-free forwarding graph, BGP maintains a loop-free forwarding graph, but there exists a loop that goes Babel -> BGP -> Babel. -- Juliusz ___ Babel-users mailing list Babel-users@alioth-lists.debian.net https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users
Re: [Babel-users] CRXN/DN42: interconnecting overlay networks with Babel and BGP
> Hence my question some time ago at the Mailling list if there is some > kind of "include" statement in babeld. You may use multiple '-c' options on the command-line to include multiple configuration files. There's no include statement currently, but I could certainly add one. ___ Babel-users mailing list Babel-users@alioth-lists.debian.net https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users
Re: [Babel-users] CRXN/DN42: interconnecting overlay networks with Babel and BGP
> I guess it would also help if babel could send some kind of metadata along > with the routes. Like BGP communities or some such. Has this been thought > about already? No objection, but there are a few questions we'd need to answer first: 1. Should the metadata be mandatory or not? Suppose that a router receives a route with a kind of metadata that it doesn't understand, should it drop the route? 2. If the route doesn't get dropped, should the metadata be transitive? If a router receives a route with a kind of metadata that it doesn't understand, should it drop the metadata, or should it reannounce the route with the metadata unchanged? 3. What should be the format of the metadata? One octet of metadata kind, followed with opaque binary data? 4. Which kinds of metadata should be defined initially? -- Juliusz ___ Babel-users mailing list Babel-users@alioth-lists.debian.net https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users
Re: [Babel-users] CRXN/DN42: interconnecting overlay networks with Babel and BGP
The bird filter engine is clearly more complex and diverse. I have now solved the problem (at least partially) with the following filters: ``` redistribute ip fd5c:3e37:2666:ea00::/56 eq 56 allow redistribute local deny redistribute deny in ip fd5c:3e37:2666:ea00::/56 deny in ip fd5c:3e37:2666::/48 le 56 allow in ip fd5c:3e37:2666::/48 deny in ip fd92:58b6:2b2::/48 le 48 allow in ip fd92:58b6:2b2::/48 deny in ip fd08:8441:e254::/48 le 64 allow in ip fd08:8441:e254::/48 deny in ip fd40:aa42:4f39::/48 le 64 allow in ip fd40:aa42:4f39::/48 deny in ip fd96:cd8b:f25d::/48 le 64 allow in ip fd96:cd8b:f25d::/48 deny in ip fda2:a9b0:a02b::/48 le 64 allow in ip fda2:a9b0:a02b::/48 deny in ip fdae:d3e4:83e4::/48 le 64 allow in ip fdae:d3e4:83e4::/48 deny in ip fdc2:9471:e3ba::/48 le 64 allow in ip fdc2:9471:e3ba::/48 deny in ip fdd2:cbf2:61bd::/48 le 64 allow in ip fdd2:cbf2:61bd::/48 deny in ip fdf1:1dc1:f54d::/48 le 64 allow in ip fdf1:1dc1:f54d::/48 deny in ip fd96:21ef:a9ba::/48 le 64 allow in ip fd96:21ef:a9ba::/48 deny in ip fdd4:975c:1440::/48 le 64 allow in ip fdd4:975c:1440::/48 deny in ip fda7:3ae7:e04d::/64 le 64 allow in ip fda7:3ae7:e04d::/64 deny in ip fd00::/8 le 64 ge 44 allow in deny ``` If it is a CRXN prefix, the maxlen is checked and the prefix is accepted or filtered accordingly. For non-CRXN prefixes it is only checked if they are between /64 and /44. If so, they are also accepted. The problem here is that now non-CRXN and non-dn42 routes can be propagated and they are not filtered. The only possibility would be to extend the babeld configuration file by 3000 lines accordingly. Hence my question some time ago at the Mailling list if there is some kind of "include" statement in babeld. On Sun, 19 Feb 2023 15:53:03 +0100 Juliusz Chroboczek wrote: > https://mk16.de/blog/the-crxn-dn42-interconnection-is-up/ > > Interestingly, the two networks use overlapping prefixes, which requires > enumerating hundreds of prefixes in their filters. This is a case where > BIRD's support for Babel is likely to be useful: babeld's filtering > engine is simply not designed for large numbers of filtering rules. > > -- Juliusz > > ___ > Babel-users mailing list > Babel-users@alioth-lists.debian.net > https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users -- Marek Küthe m...@mk16.de er/ihm he/him pgpRveKCVIwSy.pgp Description: OpenPGP digital signature ___ Babel-users mailing list Babel-users@alioth-lists.debian.net https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users
Re: [Babel-users] CRXN/DN42: interconnecting overlay networks with Babel and BGP
On Mon, 20 Feb 2023 01:29:40 +0100 Daniel Gröber wrote: > Interesting, > > Did you notice this passage: > > > This problem could be solved by calculating the Babel metric based on the > > AS path length, but I am unsure if this is technically possible, on the > > other hand this may compromise the loop-free nature of Babel. This > > problem, but with no potential solution, also occurs with the Default > > Route. > > I think the answer should be that no matter how you mess with the metrics > babel should still remain loop-free, right? The metrics thing actually works. I use the following "formula" in bird: ``` babel_metric = 70 + (2 * bgp_path.len); ``` My understanding is that it should remain loop-free as long as each Babel hop increments the metric by at least one. > > On Sun, Feb 19, 2023 at 03:53:03PM +0100, Juliusz Chroboczek wrote: > > Interestingly, the two networks use overlapping prefixes, which requires > > enumerating hundreds of prefixes in their filters. This is a case where > > BIRD's support for Babel is likely to be useful: babeld's filtering > > engine is simply not designed for large numbers of filtering rules. > > I guess it would also help if babel could send some kind of metadata along > with the routes. Like BGP communities or some such. Has this been thought > about already? That's right. This would be very practical a kind of BGP communities for Babel. The only reason I personally prefer babeld over bird is that babeld can calculate latency on its own with the RTT extension. > > For example while debugging rtt based routing metrics I would have loved to > be able to send along the raw RTT value along with each route :) > > --Daniel > > ___ > Babel-users mailing list > Babel-users@alioth-lists.debian.net > https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users -- Marek Küthe m...@mk16.de er/ihm he/him pgpWbMBJgsDvC.pgp Description: OpenPGP digital signature ___ Babel-users mailing list Babel-users@alioth-lists.debian.net https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users
Re: [Babel-users] CRXN/DN42: interconnecting overlay networks with Babel and BGP
Interesting, Did you notice this passage: > This problem could be solved by calculating the Babel metric based on the > AS path length, but I am unsure if this is technically possible, on the > other hand this may compromise the loop-free nature of Babel. This > problem, but with no potential solution, also occurs with the Default > Route. I think the answer should be that no matter how you mess with the metrics babel should still remain loop-free, right? On Sun, Feb 19, 2023 at 03:53:03PM +0100, Juliusz Chroboczek wrote: > Interestingly, the two networks use overlapping prefixes, which requires > enumerating hundreds of prefixes in their filters. This is a case where > BIRD's support for Babel is likely to be useful: babeld's filtering > engine is simply not designed for large numbers of filtering rules. I guess it would also help if babel could send some kind of metadata along with the routes. Like BGP communities or some such. Has this been thought about already? For example while debugging rtt based routing metrics I would have loved to be able to send along the raw RTT value along with each route :) --Daniel ___ Babel-users mailing list Babel-users@alioth-lists.debian.net https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users
