3 ms·

In case you want to calibrate your sense of armchair-ness: you have completely missed the point that discarding an individual attribute can quite badly change t

In case you want to calibrate your sense of armchair-ness: you have completely missed the point that discarding an individual attribute can quite badly change the meaning of a route, and since we're talking about the DFZ here, such breakage can spread around the planet to literally every DFZ participant. The only safe thing you can do is to drop the entire route. Maybe there was a point to this being discussed at quite some length by very knowledgeable people, before 7606 became RFC ;) (I haven't downvoted your comment, but I can see why others would — you're making very simple and definite statements about very complicated problems, and you don't seem to be aware of the complications involved. Hence: your calibration is a bit off.)

ExoticPearTree 1y ago
Funny enough, I actually have a few routers with a DFZ, so I have an idea or two about how BGP works. My point is that: - if you drop a connection, especially one through which you announce the full routing table, it is going to create a lot of churn to your downstreams. Depending on the kind of routers they use, it can create some network instability for quite a while. And if you drop it again when you receive that malformed route, the instability continues - removing only the malformed attribute maybe changes the way you treat traffic but you still route it. OK, you send it to maybe another interface, but no biggie - if you’re using a DFZ setup, dropping that single route could blackhole traffic to that destination if you’re the only upstream to another router
- wbl 1y ago
  Blackholes are acceptable when it comes to broken attributes. Blackholes spreading is not.
  - ExoticPearTree 1y ago
    If you just drop malfromed attributes, there is no blackhole spreading.
    - vbernat 1y ago
      If the attribute says "encapsulate this", dropping just the attribute will create a blackhole as you will attract traffic that should be encapsulated and packets following this route will be dropped it if not.
      - ExoticPearTree 1y ago
        I guess you're referring to RFC9012. Yes, but then again since you have logs of why it was dropped (like I suggested in my first post, to log everything dropped), you can easily troubleshoot the problem. A much better outcome than flapping a BGP session for no good reason and creating route churn and network instability.
        wbl 1y ago
        Or just drop the announced route (not the session) with the attribute you can't work with
- eqvinox 1y ago
  > Funny enough, I actually have a few routers with a DFZ, so I have an idea or two about how BGP works. And I'm TSC emeritus and >10 year maintainer on FRRouting, and active at IETF. Yet I hugely respect the other people there, all of whom have areas of expertise where they far outrank my own.
  - ExoticPearTree 1y ago
    Nice! (no sarcasm) I have very strong opinions about some subjects, one of them being BGP. I believe sessions should not be tear down just because you receive malformed data. You should be able to remove just the corrupt data. Or treat as a withdraw message like one of the RFC recommends. I for one one would like knobs to match on any attribute and value and remove/rewrite them at will. Imagine something akin to a very smart HTTP proxy.

ExoticPearTree 1y ago

Funny enough, I actually have a few routers with a DFZ, so I have an idea or two about how BGP works. My point is that: - if you drop a connection, especially one through which you announce the full routing table, it is going to create a lot of churn to your downstreams. Depending on the kind of routers they use, it can create some network instability for quite a while. And if you drop it again when you receive that malformed route, the instability continues - removing only the malformed attribute maybe changes the way you treat traffic but you still route it. OK, you send it to maybe another interface, but no biggie - if you’re using a DFZ setup, dropping that single route could blackhole traffic to that destination if you’re the only upstream to another router

wbl 1y ago
Blackholes are acceptable when it comes to broken attributes. Blackholes spreading is not.
- ExoticPearTree 1y ago
  If you just drop malfromed attributes, there is no blackhole spreading.
  - vbernat 1y ago
    If the attribute says "encapsulate this", dropping just the attribute will create a blackhole as you will attract traffic that should be encapsulated and packets following this route will be dropped it if not.
    - ExoticPearTree 1y ago
      I guess you're referring to RFC9012. Yes, but then again since you have logs of why it was dropped (like I suggested in my first post, to log everything dropped), you can easily troubleshoot the problem. A much better outcome than flapping a BGP session for no good reason and creating route churn and network instability.
      - wbl 1y ago
        Or just drop the announced route (not the session) with the attribute you can't work with
eqvinox 1y ago
> Funny enough, I actually have a few routers with a DFZ, so I have an idea or two about how BGP works. And I'm TSC emeritus and >10 year maintainer on FRRouting, and active at IETF. Yet I hugely respect the other people there, all of whom have areas of expertise where they far outrank my own.
- ExoticPearTree 1y ago
  Nice! (no sarcasm) I have very strong opinions about some subjects, one of them being BGP. I believe sessions should not be tear down just because you receive malformed data. You should be able to remove just the corrupt data. Or treat as a withdraw message like one of the RFC recommends. I for one one would like knobs to match on any attribute and value and remove/rewrite them at will. Imagine something akin to a very smart HTTP proxy.