4 ms·

Arista did 2, but it also dropped the whole connection which was probably bad. IMHO, just drop the broken attributes in the message and log them, and pass on t

Arista did 2, but it also dropped the whole connection which was probably bad. IMHO, just drop the broken attributes in the message and log them, and pass on the valid data if there's any left. If not, pretend you did not receive an UPDATE message from that particular peer. Monitoring will catch the offending originator and people can deal with this without having to deal with any network instability.

eqvinox 1y ago
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.
    - 1y ago

eqvinox 1y ago

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.
  - 1y ago