Packets of the University of Auckland DNS traffic were collected starting Monday 2003-09-15 05:38 UTC for 64.5 hours (from Monday, September 15, 17:38 till Thursday, September 18, 10:08 local time). Our sample contains 111430 queries to root servers from 19 U. of Auckland hosts, and 257455 queries to gTLD servers from 18 hosts. The average query rates (per minute) are 28.8 to roots and 66.5 to gTLDs.
Figure 1 shows the cumulative distribution function of number of clients.
Fig. 1. Cumulative distribution function of number of clients.
We define as high level users (HLU) the UA hosts that sent more than 10,000 mesages to either root servers or to gTLD servers.
HLU for roots (3 out of 19 name servers)
|measurement data||inside information|
|# of queries (%)||ip address||host name||software||comments|
|38212 (34.3)||22.214.171.124||kronos1.cs.auckland.ac.nz||bind 9.2.1||cs local resolver|
|33570 (30.1)||126.96.36.199||kronos2.cs.auckland.ac.nz||bind 9.2.1||cs local resolver|
|22973 (20.6)||188.8.131.52||dns2.auckland.ac.nz||bind 9.2.2||ua main local resolver|
HLU for gTLDs (5 out of 18 name servers)
|# of queries||IP address||Host name|
Figure 2 (a,b) shows the rate of queries (measured in 5 minutes intervals) vs. time. These plots are similar to Nevil's NeTraMet plots and can be directly compared witd his data.
Fig. 2a. Number of queries to roots per 5 minute intervals. Each line is shifted up by 100.
Queries to roots clearly exhibit a periodic "comb-like" structure with a peak approximately in the middle of every hour. Closer check showed that this pattern is entirely due to two of the three HLUs: kronos1 and kronos2.
Fig. 2b. Number of queries to gTLDs per 5 minute intervals. Each line is shifted up by 100.
There is no evidence of periodic "comb-like" structure in queries to gTLD. Query rate to all gTLDS increases simultaneously at around 21:00 UTC on 09/15. Other simultaneous peaks are at 3:00 UTC and at 21:00 UTC on 09/16. Note that 21:00 UTC corresponds to 9:00 of local time. The peak might be due to the beginning of a work day in New Zealand.
(Note: UA is in New Zealand and at the moment of observation there was an anycast F-root server nearby. B, L are in Southern California; E is in Northern California; A, C, D, G, H, J are on East Coast; I and K are in Europe; M is in Japan.)
Fig. 3. Distribution of queries among root servers.
Figure 3 shows distribution of queries to root servers for three top users (accounting for 85% of all UA queries), and for the rest of UA name servers (15% of all queries). The two highest users (kronos1 and kronos2, local resolvers for Computer Science Department that generate 34% and 30% of the total UA DNS traffic, correspondingly) distribute their requests among all 13 root servers in a nearly uniform manner. The tdird highest user (dns2, main local resolver for the whole University, generates 21% of the total trafiic) prefers F-root (as expected), but still sends more than 50% of its queries to other roots. The remaining 16 UA nameservers send less than 25% of their queries to F-root. The next two popular root servers for them are A and J - which may indicate Windows behavior (check witd Duane).
All three HLU of roots run the latest versions of BIND. In order to understand the differences in their root selecting patterns, we considered the distributions of response times from roots to each host (Figure 4).
The dns2 host appears to select root servers based on response time (as expected for BIND algoritdm): F is its most preferred root (43% of queries), B, L, and J follow (about 6-7% of queries to each of tdose), while the remaining nine root servers receive about 4% of queries each. However, kronos1 and kronos2 resolvers that also run BIND send their queries to all roots in a more or less uniform pattern seemingly ignoring the response times.
Assuming that the distributions of response times are similar for all UA nameservers, we see that the relatively frequent choice of A root by the remaining 16 nameservers also is not based on its performance.
We have looked at types of queries sent by the UA nameservers. The results are summarized in the Table below.
|hosts||A (1)||PTR (12)||MX (15)||AAAA (28)||other||total||bad|
|all other||7090||4645||1374||1202||2207||16518||157 (<1%)|
The Table provides more questions than answers.
Note from Nevil (insider information): I've gone through our BIND config (for dns2), it's very close to just relying on BIND's default behaviour right through. The kronos* servers are - I believe - much the same, except that they'll specify dns2 as a forwarder.