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How DNS Resolvers work ??
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How DNS Resolvers work ??

Mahfuz_SS_EHLMahfuz_SS_EHL Member, Provider

Hello,

I was searching & trying to learn about DNS Systems but not getting much information.

Suppose, I setup 4 DNSOnly Servers in 3 Different regions e.g. US, EU (2), APAC. I set them as following:

ns1 = us
ns2 = eu
ns3 = eu
ns4 = apac

or,

ns1 = us, eu (2 ipv4 in 1 nameserver)
ns2 = eu, apac (same as above)

If the visitor is from India/Singapore, will it resolve from the APAC Region server ?? Or, it can take any of the 4. If the visitor from India gets the domain resolved from us dns server, then there should be no advantage.

Also, I want to how Domain resolves from a visitors internet browser. Can anyone explain it in a sequencial form ?? I mean, I know that how it is done but when there is more than 1 nameserver & the zones are different then how is it done ??

Regards.

AlphaSSL Revocation Issue is being investigated.

Comments

  • You need CDN then

    Thanked by 1Mahfuz_SS_EHL
  • Mahfuz_SS_EHLMahfuz_SS_EHL Member, Provider

    @Jorbox said:
    You need CDN then

    No, I just need that the visitor gets resolved from the nearest DNS Server for Domain Resolving. It can be done using AnyCast DNS, but can't find out any AnyCast DNS Supporting cPanel.

    AlphaSSL Revocation Issue is being investigated.

  • The DNS resolver could use any of the authoritative nameservers, because they don't know which one is closer to them.

    Last month I did a test: I setup a domain with one NS record that has both IPv4 and IPv6. I observed that the Google DNS resolver was sending two packets from different source address to each IP address listed as authoritative nameserver.

    I believe if you have multiple NS records, the Google DNS resolver would send to every IP address at the same time. In that case, your nearest authoritative nameserver would satisfy the query.

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  • As I understand DNS - the majority of systems send 'parallel' requestes to all NS servers. The first one to answer is used. Normally the first reply is the closest or alternatively is the least busiest.
    Some systems can however send 'sequentially' to NS servers so order can be significant.

  • WiredBladeWiredBlade Member, Provider

    @Mahfuz_SS_EHL said:
    Hello,

    I was searching & trying to learn about DNS Systems but not getting much information.

    Suppose, I setup 4 DNSOnly Servers in 3 Different regions e.g. US, EU (2), APAC. I set them as following:

    ns1 = us
    ns2 = eu
    ns3 = eu
    ns4 = apac

    or,

    ns1 = us, eu (2 ipv4 in 1 nameserver)
    ns2 = eu, apac (same as above)

    If the visitor is from India/Singapore, will it resolve from the APAC Region server ?? Or, it can take any of the 4. If the visitor from India gets the domain resolved from us dns server, then there should be no advantage.

    Also, I want to how Domain resolves from a visitors internet browser. Can anyone explain it in a sequencial form ?? I mean, I know that how it is done but when there is more than 1 nameserver & the zones are different then how is it done ??

    Regards.

    In order for it to pick the resolver closest to the visitor, you will have to configure Anycast. This is more of a networking issue rather than DNS.

    There is also GeoDNS using which the DNS server can provide the visitor with name servers in their region.

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  • WiredBladeWiredBlade Member, Provider

    @Mahfuz_SS_EHL said:
    Hello,

    I was searching & trying to learn about DNS Systems but not getting much information.

    Suppose, I setup 4 DNSOnly Servers in 3 Different regions e.g. US, EU (2), APAC. I set them as following:

    ns1 = us
    ns2 = eu
    ns3 = eu
    ns4 = apac

    or,

    ns1 = us, eu (2 ipv4 in 1 nameserver)
    ns2 = eu, apac (same as above)

    If the visitor is from India/Singapore, will it resolve from the APAC Region server ?? Or, it can take any of the 4. If the visitor from India gets the domain resolved from us dns server, then there should be no advantage.

    Also, I want to how Domain resolves from a visitors internet browser. Can anyone explain it in a sequencial form ?? I mean, I know that how it is done but when there is more than 1 nameserver & the zones are different then how is it done ??

    Regards.

    A full DNS resolution starts with SOA record for that domain name starting with the root name servers which are glue records. That follows the query for NS records (usually included as part of SOA record query). That usually follows a query for A and AAAA records which provides the IP address(es) to contact to obtain the website content using HTTP(S) protocol. Here is an example of how cnn.com would resolve:

    https://dynu.com/en-US/NetworkTools/Delegation?Host=cnn.com

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  • WiredBladeWiredBlade Member, Provider

    @Mahfuz_SS_EHL said:

    @Jorbox said:
    You need CDN then

    No, I just need that the visitor gets resolved from the nearest DNS Server for Domain Resolving. It can be done using AnyCast DNS, but can't find out any AnyCast DNS Supporting cPanel.

    To setup Anycast, you must have a class C IP address from ARIN. You can then advertise the same range at multiple locations and have the BGP configured so the closest routes can be picked up. There are some VPS providers who can assist you with the setup of BGP along with Anycast. The DNS server itself is not aware of the Anycast. Anycast is more of a traffic routing method.

    A very good example of Anycast is Google.com.

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  • Mahfuz_SS_EHLMahfuz_SS_EHL Member, Provider

    @WiredBlade said:

    @Mahfuz_SS_EHL said:
    Hello,

    I was searching & trying to learn about DNS Systems but not getting much information.

    Suppose, I setup 4 DNSOnly Servers in 3 Different regions e.g. US, EU (2), APAC. I set them as following:

    ns1 = us
    ns2 = eu
    ns3 = eu
    ns4 = apac

    or,

    ns1 = us, eu (2 ipv4 in 1 nameserver)
    ns2 = eu, apac (same as above)

    If the visitor is from India/Singapore, will it resolve from the APAC Region server ?? Or, it can take any of the 4. If the visitor from India gets the domain resolved from us dns server, then there should be no advantage.

    Also, I want to how Domain resolves from a visitors internet browser. Can anyone explain it in a sequencial form ?? I mean, I know that how it is done but when there is more than 1 nameserver & the zones are different then how is it done ??

    Regards.

    A full DNS resolution starts with SOA record for that domain name starting with the root name servers which are glue records. That follows the query for NS records (usually included as part of SOA record query). That usually follows a query for A and AAAA records which provides the IP address(es) to contact to obtain the website content using HTTP(S) protocol. Here is an example of how cnn.com would resolve:

    https://dynu.com/en-US/NetworkTools/Delegation?Host=cnn.com

    For CNN.com, the last thing they got is their nameserver which they use awdns. There were 4 of them. I wanted to know from which one they got the resolving IP / A Record, or how that gets done.

    AlphaSSL Revocation Issue is being investigated.

  • I would say the best way for DNS that is best in all locations is one of these options

    • Use Amazon GeoDNS, basically you can have multiple addresses for one domain, and it will return one (or multiple) addresses based on the IP Location, latency etc. So I have an example zone which is in Los Angeles and one in Sydney. If someone queries from Sydney, it will go to Sydney since it is the closest
    • The other way would be using Anycast DNS, but you would probably need to do IP Announcements, BGP stuff. Its an effort but I think it works best.
  • WiredBladeWiredBlade Member, Provider

    @Mahfuz_SS_EHL said:

    @WiredBlade said:

    @Mahfuz_SS_EHL said:
    Hello,

    I was searching & trying to learn about DNS Systems but not getting much information.

    Suppose, I setup 4 DNSOnly Servers in 3 Different regions e.g. US, EU (2), APAC. I set them as following:

    ns1 = us
    ns2 = eu
    ns3 = eu
    ns4 = apac

    or,

    ns1 = us, eu (2 ipv4 in 1 nameserver)
    ns2 = eu, apac (same as above)

    If the visitor is from India/Singapore, will it resolve from the APAC Region server ?? Or, it can take any of the 4. If the visitor from India gets the domain resolved from us dns server, then there should be no advantage.

    Also, I want to how Domain resolves from a visitors internet browser. Can anyone explain it in a sequencial form ?? I mean, I know that how it is done but when there is more than 1 nameserver & the zones are different then how is it done ??

    Regards.

    A full DNS resolution starts with SOA record for that domain name starting with the root name servers which are glue records. That follows the query for NS records (usually included as part of SOA record query). That usually follows a query for A and AAAA records which provides the IP address(es) to contact to obtain the website content using HTTP(S) protocol. Here is an example of how cnn.com would resolve:

    https://dynu.com/en-US/NetworkTools/Delegation?Host=cnn.com

    For CNN.com, the last thing they got is their nameserver which they use awdns. There were 4 of them. I wanted to know from which one they got the resolving IP / A Record, or how that gets done.

    The browser will take the first A/AAAA record from the list. The DNS servers usually rotate the record results to ensure Round Robin results which ensure load balancing. The following command will show the same result but in different order each time.

    nslookup cnn.com

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