Miscellaneous

It is possible to find some funny names in the DNS. One such case was one MX record owned by ``bibsys.unit.no'' pointing to host ``taken.out.of.service.unit.no'' and the other was host name ``#gnasher.cineca.it''. It seems that the ``cineca.it'' administrator would want to comment this record in the master file (the comment caracter is ``;'', not ``#'').

In Ireland, it seems that renaming the ``IEUNet'' backbone was very popular. Besides the true name ``dec4ie.ieunet.ie'', there were also the folowing names in its DNS database: ``dec4ie.eu.net'' (with 19 references), ``dec4ie.ieunet.net'' and ``dec41e.ieunet.ie'' (both with 1 reference).

One of the most frequent cause of inconsistencies in DNS are CNAME RRs defining a local nickname for invalid hosts.

Some errors were caused by administrators that don't know what is the real usage of some resource records. One example of this is the insistence of using HINFO RRs to associate descriptive information to all type of domain names, like the following we have found:

uit.no.                         IN  HINFO   "University" "ofTromso"
localhost.rz.uni-karlsruhe.de.  IN  HINFO   "local" "local"

In Table 7 we present the top 40 most popular host names in Europe.


Table 7: Top 40 most popular host names in Europe (1992, April the 14th)

1168  localhost   59  castor
117  venus   57  sirius
102  pluto   56  saturn
91  pc1   54  pc5
89  cisco   52  xterm1
88  mars   52  uranus
88  loopback   52  mac2
88  iris   51  pc6
85  pc2   51  helios
84  obelix   50  titan
80  asterix   50  gauss
79  idefix   48  snoopy
75  jupiter   48  bilbo
73  pc3   47  marvin
72  hermes   47  mac1
71  zeus   47  loghost
69  pollux   47  frodo
67  orion   47  donald
65  charon   47  apollo
61  pc4   46  merlin
       46  gandalf


As expected, ``pc1'', ``pc2'', ``pc3'', ..., were very popular names. Curiously, ``mac2'' was more popular than ``mac1''. This is probably due to the fact that the name ``mac2'' is related to a ``Macintosh II'' computer model.

Another important point was the presence of ``localhost'' as the most popular host name in Europe and probably elsewhere. ``localhost'', as well as ``loopback'', are reserved names allowing any site to designate itself and its network. These names have the same role of ``self'' in the Smalltalk language for example. It is a general mechanism allowing a site to call himself without even knowing its name. ``localhost'' is directly related with the reserved address 127.0.0.1 and ``loopback'' is directly related with the network 127.0.0.0. These addresses denote a virtual host (``this host'') and a virtual network (``this network''). The introduction of these addresses in the DNS is meaningless except for providing the mapping of the name ``localhost'' to the address 127.0.0.1 and its reverse mapping.

However, sometimes we found ``localhost'', with or without the trailing dot as the right side of a MX or NS record. Whenever a server queries about the address of the mail relay, or the address of the name server, it can get, in these situations, the address 127.0.0.1, which means itself! This introduces denial of service or even some dangerous loops.

Ddt provides an extensive analysis of the presence of the name ``localhost'' in the database warning with several severity levels about the possible problems that this practice can introduce.