1. School of Electrical Engineering and Computer Science, 2004 Slide 1 Autonomic DNS Experiment Architecture, Symptom and Fault Identification

2. School of Electrical Engineering and Computer Science, 2004 Slide 2 Experiment Architecture l Physical system setup Three Dell workstations running Redhat Linux 9.0, configured on an isolated network via IP Tables. The network resides on the Computer Science Research network l Logical Domain Name System Two Root servers controlling two top level domains:.example.test Six sub-domains red.test, yellow.test, green.test white.example, orange.example, black.example

3. School of Electrical Engineering and Computer Science, 2004 Slide 3 Experiment Architecture l All instances of the DNS will consist of Bind 9.2.3 l Each domain will consist of one master DNS. l Each domain will have 0 to 5 slave DNS. Master (red) – ns.red.test Slave (red) – ns.yellow.test, ns.green.test, ns.white.example, ns.orange.example, ns.black.example Master (yellow) – ns.yellow.test Slave (yellow) – ns.green.test, ns.white.example, ns.orange.example, ns.black.example From the examples above, each zone will have n-1 slave name servers assigned to it. The last name server will be without a slave.

4. School of Electrical Engineering and Computer Science, 2004 Slide 4 Experiment Architecture l Having a varied number of slave name servers associated with the master name servers will allow us to test issues ranging from server performance on various levels to multiple user issues. l The experiments conducted will consist of the symptoms identified on the following slides

5. School of Electrical Engineering and Computer Science, 2004 Slide 5 DNS Symptoms l Loss of Network Connectivity l Response from unexpected source l Recursion Bugs l Client unsure on handling of NS record in authority section l No answer to query l Client calls on server too many times l Name server is infected with bogus cache data

6. School of Electrical Engineering and Computer Science, 2004 Slide 6 DNS Symptoms l A server refers to itself in the authority section l Cache leaks l Remote names can’t be looked up l Name error bugs l Lookups take a long time l Wrong or Inconsistent Answer l Slave name server data does not change when master server zone data changes l Is invalid proceeding anyway

7. School of Electrical Engineering and Computer Science, 2004 Slide 7 DNS Symptoms l Slave server can’t load zone data l Internet services refused l Host fails authentication checks l Inconsistant or missing bad data l Lame server reported l Name server fails to load l Name server reports “Too many open files”

8. School of Electrical Engineering and Computer Science, 2004 Slide 8 DNS Faults l Forgot to increment serial number l Forgot to reload primary master server after changes are made l Corrupt server cache l Ignored referral l To many referrals l Malicious server l Zero answer l Added name to db file, but forgot to add PTR record

9. School of Electrical Engineering and Computer Science, 2004 Slide 9 DNS Faults l Name server cache set too small l Server does not do negative caching l Syntax error in zone data file on master l Incorrect IP address for master on slave zone data file l Syntax error in configuration file or zone data file l Missing dot at end of a domain name in zone data file

10. School of Electrical Engineering and Computer Science, 2004 Slide 10 DNS Faults l Missing root.hints/db.cache data file l Missing subdomain delegation l TTL exceeded l Syntax error in resolv.conf l Incorrect labels in DNS name l Incorrect SOA format l Incorrect Glue records l Retry interval is set too low in SOA

11. School of Electrical Engineering and Computer Science, 2004 Slide 11 DNS Faults l Incorrect address in query list – allow-query { address_match_list; }; l Incorrect configuration named.conf listen-on { ip_address; }; l PTR record points to CNAME l Expire time exceeded l Loss of network connectivity

12. School of Electrical Engineering and Computer Science, 2004 Slide 12 Symptom/Fault Matrix