Monitoring.uk DNS 19 May 2006 Ian Meikle UKNOF4, Manchester

Monitoring .uk DNS

19 May 2006

Ian MeikleUKNOF4, Manchester

AgendaMonitoring .uk DNs

1. Nameserver Infrastructure

2. DNS Service Metrics

3. DNS Statistics

Questions.

Nameserver InfrastructureMonitoring .uk DNS

Nominet runs 12 authoritative nameservers for .uk/SLD.uk

• 7 Nominet-managed: ns[1-7].nic.uk

• 4 UltraDNS-managed: ns[a-d].nic.uk• 20 Anycast Instances

• 1 Hidden primary: ns0.nic.uk

3 nameservers reachable over IPv6


QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.


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. • co.uk

• 58 changes per hour• plc.uk

• less than one change per day


Physical configuration



DNS service MetricsMonitoring .uk DNS

How DNS service is monitored.

What it is measured.

How nameserver availability is determined.


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


Zone file age monitored every five minutes by nagios plug-in:

check_ddns_age!-p ns0.nic.uk ! -z co.uk ! -w 1500 ! -c 1800

Slow changing zones, e.g. sch.uk, 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




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 indexof < 100% is bad


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


DNSMON (http://dnsmon.ripe.net)

RIPE NCC subscription service

• Uses TTM boxes to monitor nameserver response

• Provides visual indicator of nameserver health

• Access to raw data is possible


DNS Statistics

Monitoring .uk DNS

New system for gathering statistics.

What queries arrive at the .uk nameservers?

Uses of this statistical data.

DNS Statistics

Monitoring .uk DNS

DSC

DSC - A DNS Statistics Collector(http://dns.measurement-factory.com/tools/dsc/)

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.

DNS Statistics

Monitoring .uk DNS



Modified Configuration

DNS Statistics

Monitoring .uk DNS

OARC: DSC

OARC - Operations, Analysis, and Research Center.(https://oarc.isc.org/faq.html)

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

DNS Statistics

Monitoring .uk DNS

DSC uses

Abuse detection, particularly data mining.

Detecting anomalous traffic.

DDoS agent identification, to help mitigate against attack.

Questions?Monitoring .uk DNS

Documents

Monitoring.uk DNS 19 May 2006 Ian Meikle UKNOF4, Manchester