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ISP DNS can be dumb and confuse CDN geolocation. When I lived in Malmö my ISP DNS would result in Akamai CDN content being served from Stockholm rather than Co

ISP DNS can be dumb and confuse CDN geolocation. When I lived in Malmö my ISP DNS would result in Akamai CDN content being served from Stockholm rather than Copenhagen which was a lot closer and faster. When I switched to 1.1.1.1 this problem went away

viraptor 3y ago
It's not that they're dumb, it's more that geolocation is just guessing. There will be mistakes and edge cases and setups which can't be geolocated. The only dumb part here would be providing a service where you can't override the download server. (Or relying entirely on the DNS rather than probing the speed)
- worik 3y ago
  > it's more that geolocation is just guessing. Does DNS care about geolocation? It measures distance in b/s dose it not?
  - viraptor 3y ago
    You can have DNS with different answers provided to different locations. https://en.wikipedia.org/wiki/GeoDNS https://en.wikipedia.org/wiki/GeoDNS The issue starts when you move from your hotspot to your wifi and keep the cached results. Or your ISP has a large address pool that's used between multiple states/countries. Or the caching DNS server gets a different answer than you would get directly. Or .... It's a mess.
    - worik 3y ago
      > https://en.wikipedia.org/wiki/GeoDNS https://en.wikipedia.org/wiki/GeoDNS I did not know that Is it widely used?
lloeki 3y ago
> ISP DNS can be dumb and confuse CDN geolocation. Or they have a vested interest in keeping customers hitting specific locations which may be suboptimal for the end user. Around here some rather have you stay in their preferred AS as much a possible and stick to DCs in Paris than Frankfurt (to direct peering?), even though FRA is a stone throw away. This conveniently disappears when using ISP-independent DNS (at the cost of sometimes, some regional-specific content not being primed in the CDN, which I think is why sometimes downloads start slow then shoot way up). e.g tested quickly today with mtr: - Home to Akamai PAR1 = 8 hops: 1-5: ISP, 5 hops 6-7: Zayo, 2 hops 8: Akamai intx-par1 best: 22, worst: 80, stdev: 10 - Home to Akamai FRA1 = 4 hops: 1-2: ISP, 2 hops 3: Akamai intx-fra1 best: 27, worst: 51, stdev: 4 Yet my ISP DNS consistently throws me towards PAR1. In practice this results in general jitter and reduced throughput (ranging from two-thirds to one third; e.g Xbox game downloads never go above 200Mb/s on par1 but shoot up to 600Mb/s on fra1).
- pastage 3y ago
  Seems more likely to be a random issue with where the dns resolver is located. Playing with the egress of your dns server like that is sad, would be interesting if you were right. Considering how badly ISPs manage DNS it is most likely incompetance.
- astrange 3y ago
  I don't think they have nearly that much control over other random sites' choice of anycast.
nottorp 3y ago
It was something about their CDN. May have been fixed now, the ps5 downloads at full speed, and I think the ps4 did too before i retired it. If google would work, I could find the old forum threads about the problem. But not any more. Oh I probably should have mentioned. The problem seems to have been global. Not any particular ISP.

viraptor 3y ago

It's not that they're dumb, it's more that geolocation is just guessing. There will be mistakes and edge cases and setups which can't be geolocated. The only dumb part here would be providing a service where you can't override the download server. (Or relying entirely on the DNS rather than probing the speed)

worik 3y ago
> it's more that geolocation is just guessing. Does DNS care about geolocation? It measures distance in b/s dose it not?
- viraptor 3y ago
  You can have DNS with different answers provided to different locations. https://en.wikipedia.org/wiki/GeoDNS https://en.wikipedia.org/wiki/GeoDNS The issue starts when you move from your hotspot to your wifi and keep the cached results. Or your ISP has a large address pool that's used between multiple states/countries. Or the caching DNS server gets a different answer than you would get directly. Or .... It's a mess.
  - worik 3y ago
    > https://en.wikipedia.org/wiki/GeoDNS https://en.wikipedia.org/wiki/GeoDNS I did not know that Is it widely used?

lloeki 3y ago

> ISP DNS can be dumb and confuse CDN geolocation. Or they have a vested interest in keeping customers hitting specific locations which may be suboptimal for the end user. Around here some rather have you stay in their preferred AS as much a possible and stick to DCs in Paris than Frankfurt (to direct peering?), even though FRA is a stone throw away. This conveniently disappears when using ISP-independent DNS (at the cost of sometimes, some regional-specific content not being primed in the CDN, which I think is why sometimes downloads start slow then shoot way up). e.g tested quickly today with mtr: - Home to Akamai PAR1 = 8 hops: 1-5: ISP, 5 hops 6-7: Zayo, 2 hops 8: Akamai intx-par1 best: 22, worst: 80, stdev: 10 - Home to Akamai FRA1 = 4 hops: 1-2: ISP, 2 hops 3: Akamai intx-fra1 best: 27, worst: 51, stdev: 4 Yet my ISP DNS consistently throws me towards PAR1. In practice this results in general jitter and reduced throughput (ranging from two-thirds to one third; e.g Xbox game downloads never go above 200Mb/s on par1 but shoot up to 600Mb/s on fra1).

pastage 3y ago
Seems more likely to be a random issue with where the dns resolver is located. Playing with the egress of your dns server like that is sad, would be interesting if you were right. Considering how badly ISPs manage DNS it is most likely incompetance.
astrange 3y ago
I don't think they have nearly that much control over other random sites' choice of anycast.

nottorp 3y ago

It was something about their CDN. May have been fixed now, the ps5 downloads at full speed, and I think the ps4 did too before i retired it. If google would work, I could find the old forum threads about the problem. But not any more. Oh I probably should have mentioned. The problem seems to have been global. Not any particular ISP.