The Design and Implementation of a Next Generation Name Service for the Internet

V. Ramasubramanian, E. Gun SirerCornell Univ.SIGCOMM 2004

Ciprian Tutu – Systems Seminar 8/4/04Johns Hopkins University

DNS: Current Operation and IssuesHigh latency in query resolve (low cache hit-rates)High load on root and TLD serversSlow update propagation (40% have TTL > 1 day)Lame delegationsImplementation errors (?)

Current DNS: bottlenecks

CoDoNS GoalsHigh Performance

Low latency, increased lookup performance

Resilience to AttacksDecentralizationDynamic load balancing

Fast Update PropagationSupport secure delegation

Beehive Prefix-matching DHTO(logN) lookup Pastry, Tapestry

Proactive cachingO(1) lookup

C=0.5 hopsxi=fraction of objects replicated at level Ib=DHT base

CoDoNS: ArchitectureDecouples namespace management from query resolutionDomain names mapped to 128bit unique identifiersDirect caching for localityHome node stores permanent copies of RR’sNo TTL associated with records inside CoDoNSSupports negative caching (NXDOMAIN)

CoDoNS (cont.)Supports DNSSEC signatures

Caches certificatesInsert/Update use version number to prevent replay attacks. (!! not Dynamic DNS compliant)Allows multiple operators to manage the same part of the name hierarchy

If conflicting records, clients “simply” pick records signed by an operator they trust (?!)

CoDoNS uses its own centralized authority to sign resource records fetched from legacy DNS (!!)

CoDoNS EvaluationMIT trace

12 hours; 281,943 queries; 47,230 unique domain names

Deployed on 75 PlanetLab nodes

Query Resolution Latency

CoDoNS Latency

CoDoNS: Flash-crowd Effect

Avg bw: 12.2KB/s/node AvgRecords/node: 4217 (10% of total, 13MB storage)

CoDoNS: Update Propagation

For 1 million node CoDoNS network it would take less than 1 minute to update 99% of replicas

ConclusionsDecouple management from query resolutionReduce resolver latencyImprove update propagation delayReduce load on root serversResistent to flash-crowd effect (?)Attempt to eliminate monopoly in namespace management

Questions/IssuesCompatibility with dynamic DNSGiving RR signing authority to CoDoNSNot really great behaviour for flash-crowdsCoDoNS caches any data that is queried (size issues)

Selective caching?No TTL on CoDoNS nodes -> if home node becomes partitioned, then no expiration.

Further issues related to CoDoNS network partitioning

Is there enough incentive for cooperation?