[gtld-tech] Definition of "% of DNS Service Availability" used in Registrant Survey
rubensk at nic.br
Mon Sep 28 20:10:28 UTC 2015
> Em 28/09/2015, à(s) 16:58:000, Chris Baker <cbaker at dyn.com> escreveu:
> I was reading the recent ICANN Releases Phase One Registrant Survey on the Domain Name Landscape and saw mention in the metrics section a "% of DNS Service Availability." I was wondering if there was a definition for this measurement available? Possibly some details about how data is collected where it is collected from? ... etc
> Please let me know if you have any questions,
> Thank you for your time,
> "% of DNS Service Availability ( Present SLA is 100% )" Category - Trust in
> http://newgtlds.icann.org/en/reviews/cct/iag-metrics-final-recs-26sep14-en.pdf <http://newgtlds.icann.org/en/reviews/cct/iag-metrics-final-recs-26sep14-en.pdf>
DNS service availability
0 min downtime = 100% availability
DNS name server availability
£ 432 min of downtime (» 99%)
TCP DNS resolution RTT
£ 1500 ms, for at least 95% of the queries
UDP DNS resolution RTT
£ 500 ms, for at least 95% of the queries
DNS update time
£ 60 min, for at least 95% of the probes
<>3.1. DNS service availability. Refers to the ability of the group of listed-as-authoritative name servers of a particular domain name (e.g., a TLD), to answer DNS queries from DNS probes. For the service to be considered available at a particular moment, at least, two of the delegated name servers registered in the DNS must have successful results from “DNS tests” to each of their public-DNS registered “IP addresses” to which the name server resolves. If 51% or more of the DNS testing probes see the service as unavailable during a given time, the DNS service will be considered unavailable.
<>3.2. DNS name server availability. Refers to the ability of a public-DNS registered “IP address” of a particular name server listed as authoritative for a domain name, to answer DNS queries from an Internet user. All the public DNS-registered “IP address” of all name servers of the domain name being monitored shall be tested individually. If 51% or more of the DNS testing probes get undefined/unanswered results from “DNS tests” to a name server “IP address” during a given time, the name server “IP address” will be considered unavailable.
<>3.3. UDP DNS resolution RTT. Refers to the RTT of the sequence of two packets, the UDP DNS query and the corresponding UDP DNS response. If the RTT is 5 times greater than the time specified in the relevantSLR, the RTT will be considered undefined.
<>3.4. TCP DNS resolution RTT. Refers to the RTT of the sequence of packets from the start of the TCP connection to its end, including the reception of the DNS response for only one DNS query. If the RTT is 5 times greater than the time specified in the relevant SLR, the RTT will be considered undefined.
<>3.5. DNS resolution RTT. Refers to either “UDP DNS resolution RTT” or “TCP DNS resolution RTT”.
<>3.6. DNS update time. Refers to the time measured from the reception of an EPP confirmation to a transform command on a domain name, until the name servers of the parent domain name answer “DNS queries” with data consistent with the change made. This only applies for changes to DNS information.
<>3.7. DNS test. Means one non-recursive DNS query sent to a particular “IP address” (via UDP or TCP). If DNSSEC is offered in the queried DNS zone, for a query to be considered answered, the signatures must be positively verified against a corresponding DS record published in the parent zone or, if the parent is not signed, against a statically configured Trust Anchor. The answer to the query must contain the corresponding information from the Registry System, otherwise the query will be considered unanswered. A query with a “DNS resolution RTT” 5 times higher than the corresponding SLR, will be considered unanswered. The possible results to a DNS test are: a number in milliseconds corresponding to the “DNS resolution RTT” or, undefined/unanswered.
<>3.8. Measuring DNS parameters. Every minute, every DNS probe will make an UDP or TCP “DNS test” to each of the public-DNS registered “IP addresses” of the name servers of the domain name being monitored. If a “DNS test” result is undefined/unanswered, the tested IP will be considered unavailable from that probe until it is time to make a new test.
<>3.9. Collating the results from DNS probes. The minimum number of active testing probes to consider a measurement valid is 20 at any given measurement period, otherwise the measurements will be discarded and will be considered inconclusive; during this situation no fault will be flagged against the SLRs.
<>3.10. Distribution of UDP and TCP queries. DNS probes will send UDP or TCP “DNS test” approximating the distribution of these queries.
<>3.11. Placement of DNS probes. Probes for measuring DNS parameters shall be placed as near as possible to the DNS resolvers on the networks with the most users across the different geographic regions; care shall be taken not to deploy probes behind high propagation-delay links, such as satellite links.
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