Google DNS vs ISP DNS

[cavedog]

So I saw a few posts here on mybroadband about using 8.8.8.8 and 8.8.4.4 as your DNS since IS and now Telkom has a local mirror for it. Google has a locally hosted DNS server

How would this affect day to day internet should you choose to use google's DNS.

The DNS is mirrored locally now that is good because it will shorten response time but in terms of youtube and akamai servers. Would you still be served by local cache servers like the ISP's DNS or will it cause problems and serve content from international servers?

 

[Tinuva]

I noticed for akamai it randomly points to local and london servers. For google content excluding youtube you will get directed to the SA Google servers.

Ok just tested, for Youtube it also points to locally hosted youtube servers at Teraco on the ip range: 173.194.128.88 as an example.

Also it is not a local mirror, it is actual Google hosted dns servers in JHB. They have some servers at Teraco JHB.

So the good news is, nowadays it is probably not a bad idea to use Google DNS, where as in the past it wouldn't be the best choice.

 

[cavedog]

I noticed for akamai it randomly points to local and london servers. For google content excluding youtube you will get directed to the SA Google servers.

Ok just tested, for Youtube it also points to locally hosted youtube servers at Teraco on the ip range: 173.194.128.88 as an example.

Also it is not a local mirror, it is actual Google hosted dns servers in JHB. They have some servers at Teraco JHB.

So the good news is, nowadays it is probably not a bad idea to use Google DNS, where as in the past it wouldn't be the best choice.

It is actually interesting.

Since I posted I did some tests. IS and Telkom pings it as a local server with +- 29ms from Richards Bay aka Durban IPC. Afrihost adsl and MTN LTE reports pings of 250ms+ so they are not peering with the server or they are simply directing the traffic straight to Europe.

That said how can one compare the speed now with Telkom since SAIX server does not reply to ping requests...

I also did a test with Telkom one on default SAIX DNS and one with Google DNS and both times the video was served by Telkom Google cache server. So Google service will be good but would be interesting to see other services like akamai.

I see that the ISP actually also plays a big role here.

 

[giggity]

Pinging 8.8.8.8 on Afrihost shows that it is international, so I'm not sure if it is the best idea for me. I'm trying out IS DNS servers right now, and they seem to work quite well.

 

[mrlgm007]

my vox account is local google dns servers mmmm


C:\Users\GreenRock>ping 8.8.8.8

Pinging 8.8.8.8 with 32 bytes of data:
Reply from 8.8.8.8: bytes=32 time=16ms TTL=54
Reply from 8.8.8.8: bytes=32 time=16ms TTL=54
Reply from 8.8.8.8: bytes=32 time=16ms TTL=54
Reply from 8.8.8.8: bytes=32 time=65ms TTL=54

Ping statistics for 8.8.8.8:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 16ms, Maximum = 65ms, Average = 28ms

C:\Users\GreenRock>tracert 8.8.8.8

Tracing route to google-public-dns-a.google.com [8.8.8.8]
over a maximum of 30 hops:

1 14 ms 14 ms 14 ms dsl-x.x.x.x.voxdsl.co.za [197.x.x.x]
2 16 ms 16 ms 15 ms 196.41.25.6
3 18 ms 25 ms 18 ms 196.41.25.12
4 31 ms 17 ms 17 ms google.jb1.napafrica.net [196.46.25.166]
5 17 ms 18 ms 19 ms 72.14.239.53
6 15 ms 16 ms 15 ms google-public-dns-a.google.com [8.8.8.8]

Trace complete.

C:\Users\GreenRock>

 

[SauRoNZA]

I noticed for akamai it randomly points to local and london servers. For google content excluding youtube you will get directed to the SA Google servers.

Ok just tested, for Youtube it also points to locally hosted youtube servers at Teraco on the ip range: 173.194.128.88 as an example.

Also it is not a local mirror, it is actual Google hosted dns servers in JHB. They have some servers at Teraco JHB.

So the good news is, nowadays it is probably not a bad idea to use Google DNS, where as in the past it wouldn't be the best choice.

Out of interest how exactly does this work based on IP address being hosted in multiple location?

Via DNS it would make some sense to me but how do you effectively have the same IP in many locations and actually manage to pass any traffic to it?

 

[giggity]

Out of interest how exactly does this work based on IP address being hosted in multiple location?

Via DNS it would make some sense to me but how do you effectively have the same IP in many locations and actually manage to pass any traffic to it?

Each ISP defines the IP address location. It sort of overrides any other locations.

 

[SauRoNZA]

Each ISP defines the IP address location. It sort of overrides any other locations.

I realise that's obviously what's happening, I want to know HOW it works.

DNS makes sense to me as you resolve the IP differently as per the DNS server, but how to have the same IP in more than one place without natting/masquerading doesn't make sense to me.

 

[Tinuva]

You can look up how anycast works. Cloudflare also make use of the same mechanism for their CDN.

Basically, you have multiple servers, in multiple locations on the internet with the same ip address configured. They all announce this same ip range out to the internet via BGP. Then the different networks/nsps/isps can choose which route is optimal for them, or for certain locations on their networks can route different even.

For the servers with these duplicate ips to work, these ips are configured as secondary ips on a loopback interface, and they have another unique primary ip, so that each individual server still is reachable between each other ect.

ISPs also use anycast routing for redundancy and failover on dns caching servers. Thus anycast have many uses, all great uses and have their specific advantages that they are used for.

Either way, I am very happy that Google decided to have a South African DNS cache server and their own South African youtube servers.

 

[SauRoNZA]

And I was going to ask if it's based on BGP in my original post but didn't want to come across as an idiot.

Thanks for the detailed explanation.

Will go read up when I can.

 

[PostmanPot]

8.8.4.4 is local for me.

 

[Thor]

What DNS does IS use ?

 

[giggity]

What DNS does IS use ?

168.210.2.2
196.14.239.2

 

[Thor]

168.210.2.2
196.14.239.2

Thanks so much! Was thinking of giving this a try since AF routes it differently althou generally don't have issues with their DNS

 

[ambo]

As Tinuva said, the 8.8.8.8 address is a secondary IP. This front-end IP is now reachable at reasonable latencies locally.

The backend/primary IP will still be unique and Google does some weird stuff with their routing. Even though the new servers are in ZA, backend IPs are routing via Europe. This means that any backend lookups involving local servers are still likely to have slower responses than your ISPs own DNS servers.

 

[SauRoNZA]

As Tinuva said, the 8.8.8.8 address is a secondary IP. This front-end IP is now reachable at reasonable latencies locally.

The backend/primary IP will still be unique and Google does some weird stuff with their routing. Even though the new servers are in ZA, backend IPs are routing via Europe. This means that any backend lookups involving local servers are still likely to have slower responses than your ISPs own DNS servers.

If it's a cache server then there's no reason for it to do any lookups beyond itself.

 

[cavedog]

If it's a cache server then there's no reason for it to do any lookups beyond itself.

+1 it should have all the data that the international one would have then. What would be the point for google to bring a local server online which costs money just for it to act kind off like a proxy. Waste of money then.

It must have all the data stored on it. I used it for a day with my Telkom account and I feel no difference. Browsing is still fast like the Telkom DNS. Hard to judge performance like this though.

 

[ambo]

If it's a cache server then there's no reason for it to do any lookups beyond itself.

So how exactly does the data get into the cache in the first place? Pixie dust?

Also remember that many of the very busy sites that you visit will have very low TTLs so the data expires from the cache very quickly and has to be looked up again.

 

[Tinuva]

If it's a cache server then there's no reason for it to do any lookups beyond itself.

Actually that is exactly what a cache server does. It does the full lookup on behalf of the users using it.

Usually starts with the root servers. Then it has to query the TLD (top level domain) servers, and then finally the authoritative domain dns servers. Thus at least 3 separate lookups, many times 4 to 5 lookups.

That said however, even with a low ttl, a request will be cached for 5-10 seconds at the very least. Where google dns wins with this, is the potential that it will have many more users using their servers, meaning chances are that the record will be cached anyways, making it a far faster server to use in most cases. General browsing won't always be noticable, you have to do dns benchmarks and probably video streaming and downloading from cdns too, to really know which dns server give you the best overall results.

 

[SauRoNZA]

So how exactly does the data get into the cache in the first place? Pixie dust?

Also remember that many of the very busy sites that you visit will have very low TTLs so the data expires from the cache very quickly and has to be looked up again.

Actually that is exactly what a cache server does. It does the full lookup on behalf of the users using it.

Usually starts with the root servers. Then it has to query the TLD (top level domain) servers, and then finally the authoritative domain dns servers. Thus at least 3 separate lookups, many times 4 to 5 lookups.

That said however, even with a low ttl, a request will be cached for 5-10 seconds at the very least. Where google dns wins with this, is the potential that it will have many more users using their servers, meaning chances are that the record will be cached anyways, making it a far faster server to use in most cases. General browsing won't always be noticable, you have to do dns benchmarks and probably video streaming and downloading from cdns too, to really know which dns server give you the best overall results.

Okay well obviously the very first user to lookup something new that isn't cached is going to do the full lookup, but everyone else will then be server locally not so?

And doesn't this really account for just about any DNS server? I mean even the ISP's official servers don't specially sync every single entry all the time so at some point you'll do a full lookup to root servers if need be.