International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 3 - Mar 2014
Performance Evaluation of
DNS Caching in a Campus Wide Network
Ridhi#1, S.Charanjit Singh*2
# Research Scholar, Computer Science, RIMT, Mandi Gobindgarh, India
*Assistant Professor, Computer Science, RIMT, Mandi Gobindgarh, India
Abstract— This paper involves analysis using DNS caching
in order to achieve the enhancement of the performance of
network as it reduces external access and provide fast
responses and recursive query support reduction in traffic
across the link which results in a single query across the
network thereby removing unnecessary traffic which is
affecting the network). Whenever a query generated by a
client and then saves (caches) the data locally. And
whenever a second or subsequent request is made by
another client for the same data, then the Caching Server
that acts as a resolver will respond with its locally stored
data (cache data) until the time-to-live (TTL) value of the
response expires, at which time the server will refresh the
data from the zone master. Effective use of caching
reduces load on server, reduces time delays for the host
and the client for transferring data, reduces effective time
in processing queries and thereby improving bandwidth of
network.
Keywords— Domain Name System (DNS), DNS queries, LAN
,IP address, DNS Caching.
I. INTRODUCTION
DNS works same as that of the telephone directory of the
Internet. .Every device on the network has its unique, IP
address, mapped to a particular domain name such as
www.google.com. It is the most essential component of
internet. It is a part of TCP/IP protocol and all the connections
are configured with IP address of atleast one DNS server to
perform resolution over the network. It is implemented as the
hierarchical and distributed database containing domain names.
As number of hosts have increased on network so the traffic
generated has also increased to a level. As for any network,
bandwidth is the basic requirement ,it refers to overall capacity
of a connection or the amount of data that can be send on a
network within a given time-period and Latency or delay is an
important factor that characterize performance of a network.
The delay of a network specifies how long it takes for a data to
travel across the network from one node to another. Both the
factors are important for the network to perform well. By the
use of localization of DNS and Caching ,the network
performance can be improved.
ISSN: 2231-5381
A. Domain Name System Concepts
A DNS server provides name resolution for TCP/IP-based
networks. That is, it makes it possible for users of client
computers to use names rather than numeric IP addresses to
identify remote hosts. A client computer sends the name of a
remote host to a DNS server, which responds with the
corresponding IP address. The client computer can then send
messages directly to the remote host's IP address. If the DNS
server does not have an entry in its database for the remote
host, it can respond to the client with the address of a DNS
server that is more likely to have information about that
remote host, or it can query the other DNS server itself. This
process can take place recursively until either the client
receives the IP address or it is known that the queried name
does not belong to a host within the specific DNS namespace.
The Domain Name System is essential part of Internet. It’s
main purpose is to resolve symbolic name to IP addresses
and retrieves information associated with the domain name
.When a DNS client issues a recursive query to a local name
server, the server attempts to resolve the name completely
with full answers or with an error by following the naming
hierarchy all the way to the authoritative name server. The
client requesting queries receive address information only
from the local name server.
B. DNS Components
The various DNS Components are the domain name space, the
naming servers and the name resolvers , as shown in Fig 1.
Domain Name Space
Domain Name Space defines the overall naming structure of
the Internet ,Name Server that maintains a portion of the
domain name spaces, resolves lookups, and maintains a cache.
Domain Name Resolution that maps a domain name to an IP
address .The domain name space defines the overall naming
structure of the Internet. It consists of an inverted tree with the
root node at the top. Each node has a label the root node has a
null label, written as “” read left to right as shown in Fig 1.
Just below the root domain there are major domains such
as .com, .net, and .org.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 3 - Mar 2014
operation (typically from a zone master) and it will respond as
authoritative for those zones for which it is defined to be a
'slave' . It is possible to have number of slave servers for any
zone. The master or slave server status is defined in open
source software BIND 8 including 'type master' in the zone
declaration section of the named.conf file .
Fig 1 shows DNS Namespace in inverted tree structure
Domain namespace consists up to 127 node levels. To ensure
that each node is uniquely identified, DNS requires that
sibling nodes ie “children” of the same “parents” must be
uniquely named.
Zones
The name space tree is sub-divided into zones. A zone
consists of a group of linked nodes served by an authoritative
DNS name server.
Resource Records (RRs)
Each node in the tree has one or more resource records, which
hold information about the domain name as IP address,
domain name server record (which indicates which computer
is to be used to retrieve information about the domain name
space for a particular domain name),address record (it tells the
name server about the correct IP address for the domain) etc.
DNS zones and records in inverted tree structure as shown in
fig 2.
Primary Name Servers
In primary name servers “authoritative” information about
domains is stored, as well as cached data requested from other
name servers.
Secondary Name Servers
Secondary name servers can get copy of zone information
from a primary name server using a process called a “zone
transfer.”
Fig 3 shows DNS name servers
C .Domain Name Resolution
Fig 2 show s DNS Zones and Records in inverted tree structure
Name Servers
The name servers store information about the name space in
units called “zones” and a loaded complete zone is said to be
authoritative zone. More than one name servers are
authoritative for the same zone that spreads the load and also
single name server is authoritative for many zones. The two
main types of servers that work on DNS are authoritative that
maintains the data .It works as Master-Slave master where the
data is edited and Slave where data is being replicated to.
Second one is Cache server that stores data obtained from
name servers. The two types of name servers are primary and
secondary. Every zone’s data to be stored on both a primary
and a secondary name server or said to be master or slave
server a slave DNS gets its zone data using a zone transfer
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Resolvers
Resolution is retrieving data from domain name spaces and
other name servers’ domain name seats whenever a page is
requested by a client. It is necessary for translation of IP
addresses. The resolver acts as a link between two computers
the one that is requesting a domain’s IP address, and other that
is holding that information and it returns the domain’s IP
address to the client that requested the information. It has to
query several servers that are authoritative to find the
necessary information.
Fig 4 shows DNS Resolution process
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International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 3 - Mar 2014
Advantage of DNS
A DNS system is very important part of the Internet
framework. Its hierarchical name space structure ,network
made of name servers, and efficient local caching provides
high-speed communication over network. DNS being highly
scalable, offer good performance even under high load. Use of
caching and effective naming system of DNS is helpful in
reducing load on the root server at the top of the name space
hierarchy and caching helps in limiting delays at the client
side and access time for host by reducing number of iterative
requests processed by name server. Thereby improving
effective use of network bandwidth .
performed by a non-local DNS and then a local DNS ,the
results of both are compared.
III.RESEARCH METHODOLOGY
In present work study is to check the impact of localization of
DNS on the network bandwidth with the help of parameters
such as delay and throughput. Method used to demonstrate the
impact of localization of local DNS is calculated in terms of
time taken by data packet (in milli seconds) and size of
message (in bytes). To show the impact of local DNS, two
different scenarios are created and results of both are
compared. Local and Non- local ping time tests are taken out ,
by which after and before effect is calculated on network.
II. RELATED WORK
In previous years ,much work has been done using DNS to
improve the performance of network as Balachander
Krishnamurthy in 2001 discussed in different sections to
improve of CDN’s by employing DNS redirection to balance
load among the servers and how the network performance is
improved in terms of latency ,reduction in traffic over the
network. In 2004 Jeffrey Pang, Aditya Akella and Annees
Shaikh studied DNS techniques as mirroring , ISP homing to
achieve the goals of scalability and availability. Again in the
year 2004 Park et. Researched to introduce CoDNS, a
lightweight, cooperative DNS lookup service that can be
independently and incrementally deployed to augment
existing name servers. It uses a locality and proximity-aware
design to distribute DNS requests, and achieves low-latency,
low. Tamrakar (2008) discussed how due to large number of
usage of social networking sites, the performance of network
has been degraded due to large amount of traffic on network.
Also most of the networking sites have redefined the way,
users interact online. Most of the social networking sties
provide customizable personal pages to its members. During
customization user may embed contents from different web
sites that provide contents in a form of HTML embed codes.
Thus a page may contain different contents from several
different web sites. As a result when a page download may
generate hundreds of DNS queries and even if number of
people access these social networking sites at the same time
using same Internet service provider, the number of DNS
queries sent to local DNS server increases. So it lead to slow
performance of network . In this paper, Tamrakar mentioned
some of available methods that social networking sites could
implement to reduce such traffic and improve the network
.performance. Ager et. al (2010) defined Domain Name
System (DNS) as crucial part of Internet The performance
more and more applications depend not only on the
responsiveness of DNS, but also the exact answer returned by
the queried DNS resolver. In this paper ,the existing work is
done by the use of Localisation of DNS ,the performance of
campus wide network is evaluated ,in terms of bandwidth and
time delay. By the use of Local cache the effective time of
data transfer and processing of queries and retrieval is reduced
thereby enhancing performance of network. Firstly queries are
ISSN: 2231-5381
A local DNS
In the local DNS technique server is deployed at a location as
in case of LAN within the organization (as shown in the
figure) so that the queries generated by users from different
locations can be answered locally ie within the organization
and no need to go to other DNS server outside the
organization ,at a location. For users at different locations,
router forward the queries from various users to the local DNS
server. As the server is localised within the organisation. This
approach will reduce delay as queries are resolved locally by
using local cache, which stores the data, used in query
resolving process. This will enhance network throughput as a
result less bandwidth is consumed as DNS look up data need
to travel shorter path as compared to other approach.
Fig 5 shows local DNS within the campus
A Non-Local DNS
In the Non-Local DNS technique server is configured to
resolve the DNS queries. In this case DNS queries are
answered by single DNS server. Packets have to travel a
longer path and use more network resources. Sometimes TTL
is expired and queries remain unanswered thereby increasing
load on the single DNS server which results in delay,
consumption of more time and more bandwidth. Even there
will be no use of high speed of network ,if resolver takes lot
of time to resolve a query .So there is need of local DNS
which improves network performance.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 3 - Mar 2014
DNS Cache
Time –to Live value in Resource record indicates the time for
which the DNS cache information be used before expiring.
The data stored in local cache can be used to answer the
queries ,the cached data has limited TTL ,if TTL is
short,utisation of server increases and if TTL is long,
utilization of server decreases the utilization of DNS and
reduces network traffic . A caching server have named.conf
file, a server that provide caching , support recursive queries.
If the caching server obtains its data directly from a zone
master it is said to be as 'authoritative', if the data is taken
from local cache the response is taken as 'non-authoritative'.
Message Size
( Bytes)
Time (ms)
128
0.98
256
1.24
512
1.98
1024
3.96
4096
5.34
IV.RESULTS AND DISCUSSIONS
The Ping test parameters of local and non -local DNS server
are arranged in Table 1 and Table 2 respectively. Table 1
shows ping time for local DNS server and Table 2 represent
ping time for non-local DNS server.
Message Size
( Bytes)
Time (ms)
128
0.25
256
0.78
512
1.56
1024
2.80
4096
4.58
TABLE 1 Non- Local DNS PING Time
From the table it is understood that in case of non local
server,as message size increases from 128 bytes ,response
time is increasing . It means if message length is high ,it will
take longer time for the response ,load on server will increase
and lead to more consumption of bandwidth of the network. If
the user is demanding repetitive queries ,if DNS is
localized ,local cache will be used which will help in reducing
time delays, thereby increasing performance of network in
terms of reduced RTT .So the main advantages of using local
DNS and DNS Cache are : Firstly it provides facility that
queries can be completed by the local DNS . Secondly, it
reduces the delay of DNS queries in the network and lead to
Improvement of response time of web servers. Moreover it
facilitate lookups to be resolved within the network and
thereby reducing dependency of local network on the entire
network.
5
Table 2 Local PING Time
4
Time
(ms)
3
Non local
DNS
2
Local DNS
1
0
128 256 512 1024
Message Size
Fig 6 shows graph comparison of network delay
The graph shows the comparison of the network latency in
case of local DNS and Non local DNS server. Blue line in the
graph shows the delay in case of Non –Local DNS and red
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International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 3 - Mar 2014
line shows the new delay of Local DNS. It can be seen from
the graph that delay in case of local than is less than the case
of Non Local DNS .In case of localization, the network traffic
remains local . So DNS queries travel shorter distance which
reduces transmission delay ,manage traffic thereby improve
bandwidth by reducing latency. So it is effective to use Local
DNS in terms of reduced delay and Increased throughput
which means that bandwidth of network is being used in more
efficient way.
V. CONCLUSIONS
In the present study, an attempt is made to study the effect of
DNS over the distributed LAN or WAN for the different
message size. As the message is increased the response time
increases drastically and affecting the campus network
bandwidth as shown in the tables and graph. The caching of
the DNS in the local server is effective in handling the
repeated request which is meant for the local domains and
virtual private network having dedicated bandwidth to access
the central services. This proposed design of the campus
network will be effective and responsive to the queries from
the local computers.
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IEEE. ,2004.
[6] J. Jung, E. Sit, H. Balakrishnan, and R. Morris, “DNS
performance and the effectiveness of caching. IEEE/ACM
Transactions on Networking, 10(5), October 2003.
[7] Anees Shaikh Renu Tewari Mukesh Agrawal, “On the
Effectiveness of DNS-based Server Selection”, IMC
[8] Sandeep Tamrakar, “Impact of Social networking sites on Local
DNS server,2008.
[9] M. Corporation, “How DNS Query Works”,Technical Manual,
Microsoft Corporation ,2005.
[10] IBM, “ Understanding DNS queries. Technical manual”, IBM.
[11] ] A. S. Tanenbaum, “Computer Networks”, Prentice-Hall
Inc, 4th edition, 2003.
ACKNOWLEDGMENT
The author would like to thank the Editor, respected guide and
other faculty members for their valuable suggestions and
expert comments.
REFERENCES
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