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1 DNS 19 May 2006 Ian Meikle UKNOF4, Manchester

2 Agenda DNs 1. Nameserver Infrastructure 2. DNS Service Metrics 3. DNS Statistics Questions.

3 Nameserver Infrastructure DNS Nominet runs 12 authoritative nameservers 7 Nominet-managed: ns[1-7] 4 UltraDNS-managed: ns[a-d] 20 Anycast Instances 1 Hidden primary: 3 nameservers reachable over IPv6

4 Nameserver Infrastructure DNS

5 Nameserver Infrastructure DNS Dynamic DNS characteristics Potentially, 500 changes per minute Serial number is UNIX time of update, e.g. 1146832341 Propagation varies between nameservers BIND, <300s lag UltraDNS 3000 ~ 5000s lag Frequency of updates varies between SLDs, e.g. 58 changes per hour less than one change per day

6 Nameserver Infrastructure DNS Physical configuration

7 DNS service Metrics DNS How DNS service is monitored. What it is measured. How nameserver availability is determined.

8 DNS service Metrics DNS PINC - Nominet’s nagios-based monitoring system Regular polling to ascertain that: Nameserver is reachable (ping) DNS service is available (udp/tcp) Zone file age is within acceptable range

9 DNS service Metrics DNS Zone file age monitored every five minutes by nagios plug-in: check_ddns_age!-p ! -z ! -w 1500 ! -c 1800 Slow changing zones, e.g., have a ‘grace period’ of 30 seconds. Required as previous serial number may lag by many hours UltraDNS have much longer thresholds: Warn at 8000s Critical at 15000s

10 DNS service Metrics DNS

11 DNS service Metrics DNS

12 DNS service Metrics DNS Nameserver availability KPIs Each month, an individual nameserver must have no more than: 60 minutes unplanned downtime 120 minutes total downtime Nameserver constellation must have zero minutes downtime per month Creative statistical recording means that an availability index of < 100% is bad

13 DNS service Metrics DNS Nameserver availability KPIs Recording of downtime is presently a manual process Planned maintenance is logged in advance Outages recorded as they happened Once a month, nameserver availability verified using DNSMON

14 DNS service Metrics DNS DNSMON ( RIPE NCC subscription service Uses TTM boxes to monitor nameserver response Provides visual indicator of nameserver health Access to raw data is possible

15 DNS service Metrics DNS

16 DNS Statistics DNS New system for gathering statistics. What queries arrive at nameservers? Uses of this statistical data.

17 DNS Statistics DNS DSC DSC - A DNS Statistics Collector ( Two components to DSC: Collector, using libpcap to capture DNS traffic, storing it as XML Presenter, extracts data from XML and displays graphically. Collectors located at each Nominet-managed nameserver site. Presenters at Nominet, and at OARC.

18 DNS Statistics DNS Modified Configuration

19 DNS Statistics DNS OARC: DSC OARC - Operations, Analysis, and Research Center. ( Public service run by ISC: “The OARC provides a neutral forum for bilateral sharing of sensitive information during DNS attacks by organizations that are dependent on the proper operation of the DNS. The OARC also provides a continued stream of analysis on the operation of the global DNS.” OARC’s DSC presenter gives statistics for: C, E, and F-Root RFC1918 ISC Nominet

20 DNS Statistics DNS DSC uses Abuse detection, particularly data mining. Detecting anomalous traffic. DDoS agent identification, to help mitigate against attack.

21 Questions? DNS

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