A Study of DNS Lameness by Ed Lewis ARIN Research Engineer Presented by Ray Plzak President

Agenda Definition Purpose Results September 2002 APNIC 14

Definitions Lameness is – an NS RR That Lameness might happen if: Contains no address record(s) Does not respond to queries Responds negatively for the zone Lameness might happen if: Domain name has multiple addresses Server responds non-authoritatively (recursively) September 2002 APNIC 14

Why Bother? ARIN membership raised the issue of cleaning this up Lame delegations cause Application Failure Service Delay Lame delegations can be limited easily Intermittent network problems make it infeasible to eliminate it completely September 2002 APNIC 14

Reverse Map This effort is targeted at ARIN's reverse map delegations ARIN's /8's Legacy /8's Not all /8's - not RIPE NCC, not APNIC Dependencies are simplifying assumptions about the parsing of the zone files summary output breaks results into /16's and /24's September 2002 APNIC 14

Early results Remember, this is not all of in-addr.arpa... As of July 2002 Number of NS RR's 548,667 Number of zones 231,240 Number of name server names 25,047 Number of IP unique addresses 21,846 September 2002 APNIC 14

per Zone demographics Servers per zone - max 7, avg 2.37 Addresses per zone - max 26, avg 2.32 Zones with no addresses 3,062 Zones with one address 7,365 All zones have multiple NS RR's Some lacked glue for one Some had two names with identical glue Some duplicates slipped through September 2002 APNIC 14

per Name Server Zones - max 5772, avg 21.9 No address - 3,178 Multiple addresses - 219 Addresses - max 24, avg not counted Longest name 41 chars September 2002 APNIC 14

per IP Zones - max 5772, avg 24.6 Addresses with multiple domain names pointing to them - 291 Max number of domain names pointing to an address - 9 PTR records not checked September 2002 APNIC 14

Counting By Zones Condition % Comment No IP address 1 Unreachable One IP address 3 Multi Address 95 “the requirement” No Working 38 Zone not reachable One Working 10 Multi Working 52 No Broken 49 “perfect zones” Some Broken 13 Notes "No working" – Never a reply "No broken" – All servers good "Some broken“ – Some lameness September 2002 APNIC 14

Next steps Measure number of faulty NS RRs Distribute and run from different locations Correlate results from different network locations Present observations to membership Investigate the use of this data September 2002 APNIC 14

Thank You September 2002 APNIC 14