Lab Eight : The Domain Name System
Members:
Edmund Chang
70813570
Lin He
__________
Negar Mohades
__________
Prelab 8
1.) host - DNS lookup utility. host is a simple utility for performing DNS lookups. It is
normally used to convert names to IP addresses and vice versa. When no arguments or
options are given, host prints a short summary of its command line arguments and
options.
2.) Terms used in the Domain Name System:
a. Top-level domain = The top portion of the hierarchical name space. Divides up
the Internet Name Space into categories such as COM, EDU, GOV, MIL, NET,
ORG, INT, US, ARPA. The DNS has a root domain at the top of the hierarchy
and directly under are the top-level domains.
b. CNAME (canonical name) = A host's official name as opposed to an alias. The
official name is the first hostname listed for its Internet address in the hostname
database.
c. Resolver = The resolver is the DNS client used on most Linux and BSD systems.
It comes with glibc. Its configuration file /etc/resolv.conf (note the spelling)
determines the DNS servers to use, and various other options.
d. Name server = A name server's purpose is to receive queries from resolvers and
return answers to those queries. Usually, a resolver, or some other program, will
make a query and the name server will either return an answer, or the address of
the place that the resolver can look to find an answer. Name servers hold
information about a domain's structure. If a name server holds complete
information for a specific zone, it is considered authoritative for that zone. Being
authoritative, that server is responsible for maintaining accurate information about
that zone.
e. Label = Naming in DNS begins with giving each domain, or node, in the DNS
name space a text label. The label identifies the domain within the structure, and
must follow certain syntax rules.
f. FQDN (fully qualified domain name) = A fully qualified domain name consists of
a host and domain name, including top-level domain. For example,
www.webopedia.com is a fully qualified domain name. www is the host,
webopedia is the second-level domain, and.com is the top level domain. A FQDN
always starts with a host name and continues all the way up to the top-level
domain name, so www.parc.xerox.com is also a FQDN.
g. BIND = BIND (Berkeley Internet Name Domain) is an implementation of the
Domain Name System (DNS) protocols and provides an openly redistributable
reference implementation of the major components of the Domain Name System.
The BIND DNS Server is used on the vast majority of name serving machines on
the Internet, providing a robust and stable architecture on top of which an
organization's naming architecture can be built. The resolver library included in
the BIND distribution provides the standard APIs for translation between domain
names and Internet addresses and is intended to be linked with applications
requiring name service.
h. Inverse lookup = Inverse queries where you perform a lookup for the hostname
belonging to an IP address.
i. RR (resource record) = A DNS uses resource records to resolve host names and IP
addresses. These records are stored in the DNS zone files. The record types NS,
SOA, CNAME, and PTR form the basic infrastructure of DNS.
j. SOA (start of authority) = Start of authority record. Specifies the server that
contains the zone files for the domain.
3.) Types of DNS queries:
a. Inverse queries work differently. When a DNS server receives an inverse query, it
returns the friendly name for an IP address, rather than an IP address for a friendly
name. However, searching the entire Internet for a friendly name match would
prove time consuming. Rather than waste resources, use of the in-addr.arpa
domain notifies name servers of an inverse query. Special pointer (PTR) records
are added to the in-addr.arpa domain, and these PTR records match IP addresses
(whose octets are actually reversed to delegate administration of A, B, and C class
addresses) to friendly domain names. For example, clients seeking to determine
the friendly name for the IP address 192.168.1.2 would send the local name server
a request for the PTR record for 2.1.168.192.in-addr.arpa.
b. Iterative queries: When the name server of a host cannot resolve a query, it sends
a referral to another server to the resolver.
c. Recursive query: When the name server of a host cannot resolve a query, the
server issues a query to resolve the query.
4.) Domain name servers store information about part of the domain name space called a
zone. The name server is authoritative for a particular zone. A single name server can be
authoritative for many zones. Understanding the difference between a zone and a domain
is sometimes confusing. A zone is simply a portion of a domain. For example, the
Domain Microsoft.com may contain all of the data for Microsoft.com,
Marketing.microsoft.com and Development.microsoft.com. However, the zone
Microsoft.com contains only information for Microsoft.com and references to the
authoritative name servers for the subdomains. The zone Microsoft.com can contain the
data for subdomains of Microsoft.com if they have not been delegated to another server.
For example, Marketing.microsoft.com may manage its own delegated zone.
Development.microsoft.com may be managed by the parent, Microsoft.com. If there are
no subdomains, then the zone and domain are essentially the same. In this case the zone
contains all data for the domain.
5.) Some of the top-level domains in the DNS namespace:
com
Commercial organizations
edu
Educational institutions
gov
Government institutions
int
International organizations
mil
U.S. military institutions
net
Networking organizations
org
Non-profit organizations
6.) No, domain names are not case sensitive. The constraints on the length of domain names
is that each label can be at most 63 characters and the total length of the FQDN can be at
most 255 characters.
7.) Root Servers of the Internet:
A.ROOT-SERVERS.NET.
(VeriSign, Dulles, VA)
198.41.0.4
B.ROOT-SERVERS.NET. (ISI, Marina Del Rey CA)
192.228.79.201
C.ROOT-SERVERS.NET. (Cogent Communications) 192.33.4.12
D.ROOT-SERVERS.NET. (University of Maryland)
128.8.10.90
E.ROOT-SERVERS.NET. (Nasa Ames Research Center)
192.203.230.10
F.ROOT-SERVERS.NET. (Internet Systems Consortium)
192.5.5.241
G.ROOT-SERVERS.NET. (US Department of Defense) 192.112.36.4
H.ROOT-SERVERS.NET. (US Army Research Lab)
128.63.2.53
I.ROOT-SERVERS.NET.
(Stockholm, Sweden) 192.36.148.17
J.ROOT-SERVERS.NET. (Herndon, VA)
192.58.128.30
K.ROOT-SERVERS.NET. (London, United Kingdom) 193.0.14.129
L.ROOT-SERVERS.NET. (IANA, Los Angeles) 198.32.64.12
M.ROOT-SERVERS.NET. (WIDE, Tokyo)
202.12.27.33
8.) The .arpa domain is the Address and Routing Parameter Area domain and is designated
to be used exclusively for Internet-infrastructure purposes.
9.) Result of nslookup:
C:\Documents and Settings\Edmund Chang>nslookup www.cnn.com
*** Can't find server name for address 192.168.0.1: Non-existent domain
*** Default servers are not available
Server: UnKnown
Address: 192.168.0.1
Non-authoritative answer:
Name:
cnn.com
Addresses: 64.236.16.84, 64.236.16.116, 64.236.24.4, 64.236.24.12
64.236.24.20, 64.236.24.28, 64.236.16.20, 64.236.16.52
Aliases: www.cnn.com
The computer chose 64.236.24.28.
Report
Questions from EXERCISE:
CHECKLIST FORM FOR LAB 8
Prelab 8 question sheet
Checkoff for Part 1
Checkoff for Part 2
Checkoff for Part 3
Checkoff for Part 4
Checkoff for Part 5
Checkoff for Part 6
Feedback sheet
Lab report
FEEDBACK FORM FOR LAB 8
Part 1
Network Setup
Part 2
Name Resolution
without DNS
Part 3
Configuring a DNS
Server
Part 4
DNS Traffic
Part 5
Caching-Only
Servers
Part 6
Hierarchy of DNS
Servers
Difficulty
1
Interest Level
2
Time to Complete
73 minutes
1
2
60 minutes
1
2
73 minutes
1
2
60 minutes
1
0
50 minutes
1
2
60 minutes
What I liked about this lab:
-I liked the fact that it showed us how to use The Domain Name System.
What I disliked about this lab:
-The report questions were a little long and required extra research.
My suggestion to improve this lab:
-Make clearer questions and maybe a standard of what data to show since some of the
captures are huge but I am not sure what parts they want to see even though I know which ones
are relevant to my answers.