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An Analysis of Distributed Computer Network Administration
1Amit Kumar Sahu,
2Naveen Hemrajani
1M-Tech Scholar, Suresh Gyan Vihar University, Jaipur (India), [email protected] ,
2Vice Principal of Engineering, Suresh Gyan Vihar University, Jaipur (India), [email protected]
Abstract Computer Networking is necessary to human beings.
Peoples needed to share ideas, research knowledge, and
the way of life to their friends. In the modern time, the role
of computer networks became dreamy. Analyzing,
accessing, sharing and storing of data and information are
very easy with help of distributing computer networking.
Social networking sites look after human communication
in a better manner and create platforms for in agreement
individuals to share their thoughts and opinions. There is a
massive contribution of computer networking apparatus in
the progress which we see today.
But when manage computer networking traffic in
distributed computer environment, the quality of network
connection is challenging task for network Administrator.
Computer network properties are depends on different
types of applications. Important properties of the quality of
network connection are bandwidth, delay and reliability.
The network Administrator uses many troubleshooting
software to solving network problem regarding the quality
of connection.
This paper explores different properties for the
administration for the distributed computer network
environment like techniques for measuring and analyzing
the performance. This analysis precious for computer
network administrator, who administrating distribute
computer network.
Keywords: Networking traffic, Distribute computer
network, bandwidth, delay, reliability.
1. Introduction
1.1 Distributed computing
Distributed computing is a field of computer science that
studies distributed systems. A distributed system consists
of multiple autonomous computers that communicate
through a computer network. In distributed computing, a
problem is divided into many tasks, each of which is
solved by one or more computers. The study of distributed
computing became its own branch of computer science in
the late 1970s and early 1980s.
The platform for distributed systems has been the
enterprise network linking workgroups, departments,
branches, and divisions of an organization. Data is not
located in one server, but in many servers. These servers
might be at geographically diverse areas, connected by
WAN links [3].
There are two main reasons for using distributed systems
and distributed computing. First, the very nature of the
application may require the use of a communication
network that connects several computers. For example,
data is produced in one physical location and it is needed
in another location. Second, there are many cases in which
the use of a single computer would be possible in principle,
but the use of a distributed system is beneficial for
practical reasons.
Traditionally the server had processed both the client
environment and the production environment. In situations
where the data could be stored on the pc itself, the
processing of the production data could be executed on the
local processor. But this moved the bottleneck away from
the production server processors, and to the network
bandwidth [3].
Some advantages with the thick client approach are:
Lower server requirements, as a thick client does most
of the application processing itself.
Lower user environment network bandwidth usage,
because there is no keyboard or screen data that has
to be sent to and from the server.
Higher system reliability, as the thick clients can
operate even when the processing servers are
unavailable.
1.2 Computer Networks
A computer network, often simply referred to as a network,
is a collection of hardware components and computers
interconnected by communication channels that allow
sharing of resources and information. Where at least one
process in one device is able to send/receive data to/from
at least one process residing in a remote device, then the
two devices are said to be in a network.
1.2.1 Network Classification
Networks may be classified according to a wide variety of
characteristics such as the medium used to transport the
data, communications protocol used, range of the network,
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scale, topology, and organizational scope. Networks that
range a few meters are classified as personal area networks
(PAN). Networks that range a few hundred meters are
classified as local area networks (LAN). Networks that
within a range of some kilometers, known as metropolitan
area network (MAN). And any networks ranging more
than some kilometers are classified as Wide Area
Networks (WAN) [1].
1.2.2 Network Topologies
Network topology is the layout pattern of interconnections
of the various elements (links, nodes, etc.) of a computer
or biological network. Network topologies may be
physical or logical. Physical topology refers to the physical
design of a network including the devices, location and
cable installation. Logical topology refers to how data is
actually transferred in a network as opposed to its physical
design. In general physical topology relates to a core
network whereas logical topology relates to basic network.
There are several possibilities when connecting several
nodes together in a computer network. These possibilities
are called network topologies [1].
The study of network topology recognizes eight basic
topologies:
Point-to-point
Bus
Star
Ring or circular
Mesh
Tree
Hybrid
Daisy chain
1.2.3 Network Transmission Media
Various physical media can be used to transport a stream
of bits from one device to another. Each has its own
characteristics in terms of bandwidth, propagation delay,
cost, and ease of installation and maintenance. Each media
have different qualities and properties. Popular network
transmission Medias are Twisted Pair Cable, Coaxial
Cable, Optical Fiber Cable
1.2.4 Network Protocols
A protocol is a set of rules that governs the
communications between computers on a network. These
rules include guidelines that regulate the following
characteristics of a network: access method, allowed
physical topologies, types of cabling, and speed of data
transfer. A protocol can therefore be implemented as
hardware or software or both. Examples are IP, TCP,
UDPHTTP, FTP, SSH, MAC, ARP, FDDI, MPLS, etc.
1.2.5 Network Media Access Control
The Medium Access Control (MAC) protocol is used to
provide the data link layer of the Ethernet LAN system.
The MAC protocol encapsulates a SDU (payload data) by
adding a 14 byte header (Protocol Control Information
(PCI)) before the data and appending a 4-byte (32-bit)
Cyclic Redundancy Check (CRC) after the data.
Examples of media access control are ATM, FDDI, PPP,
Ethernet
1.3 Data security on network
The area of network security consists of the provisions
and policies adopted by the network administrator to
prevent and monitor unauthorized access, misuse,
modification, or denial of the computer network and
network-accessible resources. Network security involves
the authorization of access to data in a network, which is
controlled by the network administrator. Users choose or
are assigned an ID and password or other authenticating
information that allows them access to information and
programs within their authority [1].
In process to secure computer system, three following
properties are essential [8]
Confidentiality
Integrity
Availability
1.4 Measurements
The measure of computer network performance is
commonly given in units of bits per second (bps). This
quantity can represent either an actual data rate or a
theoretical limit to available network bandwidth. Modern
networks support very large numbers of bits per second.
Instead of quoting 10,000 bps or 100,000 bps, networkers
normally express these quantities in terms of larger
quantities like "kilobits," "megabits," and "gigabits."
Measurements are conducted in four stages [4].
Data collection
Analysis
Presentation
Interpretation
Time series
A time series diagram shows the x-axis in time, and the y-
axis as the measured values of data. Time series diagrams
are useful for describing the measured data, and spotting
trends. An example of a time series diagram can be found
in figure 1.
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Figure 1: Timeseries diagram.
2. Review of Literature
2.1 Quality of Service
These days, having stable network connections is a must.
With the ultimately modern world that we all live in today,
a lot of our activities would no longer progress if we do
not have a reliable internet connection. Communication,
bank transaction, research and even shopping all depend
on the worldwide web. With our extensive use of mobile
phones, computers, GPS devices, music and video players,
entertainment appliances and other gadgets, we certainly
need to be aware of the things that we need to do to ensure
that our connections are functioning well [1][12][13].
Quality of Service refers to a broad collection of
networking technologies and techniques. The goal of
Quality of Service is to provide guarantees on the ability
of a network to deliver predictable results. A network
monitoring system must typically be deployed as part of
Quality of Service, to insure that networks are performing
at the desired level [1][13]. The problem with a distributed
computer network is that the routes may have different
properties. The main properties for a distributed compute
network connections are[1][13]:
1) Bandwidth
2) Delay
3) Reliability
4) Jitter
2.2 Quality of Service Standards
With the growth of multimedia networking, often these ad
hoc measures are not enough. Serious attempts at
guaranteeing quality of service through network and
protocol design are needed. In the following sections we
will continue our study of network performance, but now
with a sharper focus on ways to provide a quality of
service matched to application needs. It should be stated at
the start, however, that many of these ideas are in flux and
are subject to change.IETF try to creating a architecture
for streaming multimedia. They result come with two
different analysis.
2.2.1 Differentiated Services
Recent work on differentiated services in the Internet has
defined new notions of Quality of Service (QoS) that apply
to aggregates of traffic in networks with coarse spatial
granularity. Most proposals for differentiated services
involve traffic control algorithms for aggregate service
levels, packet marking and policing, and preferential
treatment of marked packets in the network core. The
problem with this analysis is that there is no common
policy for the type of service field, and so when packages
pass through different networks, the packets may be
handled different then intended by the original sender
computer[1][13][12].
2.2.2 Integrated Services
Integrated services are an architecture that specifies the
elements to guarantee quality of service (QoS) on
networks. Integrated services can for example be used to
allow video and sound to reach the receiver without
interruption. Integrated services, create the path through
the network for the flow of data. This requires a setup for
the connection, when the connection between two nodes is
established. The idea of Integrated services is that every
router in the system implements Integrated services, and
every application that requires some kind of guarantees
has to make an individual reservation [1][13][12].
2.3 Bandwidth
Bandwidth in computer networking refers to the data rate
supported by a network connection or interface. One most
commonly expresses bandwidth in terms of bits per second
(bps). The term comes from the field of electrical
engineering, where bandwidth represents the total distance
or range between the highest and lowest signals on the
communication channel (band)[1][4].
Access Control Technology
Bits Bytes
Ethernet (10base-X) 10 Mb/s 1,25 MB/s
FastEthernet (100base-X) 100 Mb/s 12,5 MB/s
FDDI 100 Mb/s 12,5 MB/s
Gigabit Ethernet (1000base-X) 1.000 Mb/s 125 MB/s
Table 1: Description of Bandwidth provided by various access
technologies
Bandwidth is the throughput of the connection that is of
interest for the customer. "Throughput is
a measure of the amount of data that can be sent over
network in a particulate time[ 14]".
The throughput is determined by the formula:
Throughput =Data Transfer
Time Eq-1
2.4 Reliability
Reliability is term as "An attribute of any system that
consistently produces the same results, preferably meeting
or exceeding its specifications"[5]. To provide network
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reliability, it is also important to do preplanning and/or
advanced preparation. Of course, one way is to have
additional spare capacity in the network. However, there
can be a failure in the network that can actually take away
the spare capacity if the network is not designed properly
because of dependency between the logical network and
the physical network [20]. Thus, it is necessary to audit the
network and find the vulnerable points in the network and
then to equip the network with additional capabilities to
avoid such vulnerabilities. For example,
1. The network may be provided with
transmission-level diversity so that for any
transmission link failure there is at least another path not
on the path of the failure.
2. A redundant architecture at network nodes
can be built to address for a node
component or nodal failure; this may include dual or multi
homing to provide for multiple access and egress points to
and from the core network.
The failure rate (λ) has been defined as "The total number
of failures within an item population, divided by the total
time expended by that population, during a particular
measurement interval under stated conditions. It has also
been defined mathematically as the probability that a
failure per unit time occurs in a specified interval, which is
often written in terms of the reliability function, R(t), as,
λ =R t1 −R(t2)
t2−t1 R(t1) Eq-2
where, t1 and t2 are the beginning and ending of a
speci_ed interval of time, and R(t) is the reliability
function, i.e. probability of no failure before time t. The
failure rate data can be obtained in several ways. The most
common methods are[22]:
Historical data about the device or system under
consideration.
Government and commercial failure rate data.
Testing.
2.5 Delay
Network delay is an important design and performance
characteristic of a computer
network or telecommunications network. The delay of a
network specifies how long it takes for a bit of data to
travel across the network from one node or endpoint to
another. It is typically measured in multiples or fractions
of seconds. Delay may differ slightly, depending on the
location of the specific pair of communicating nodes.
Although users only care about the total delay of a
network. Thus, engineers usually report both the maximum
and average delay, and they divide the delay into several
parts:
Processing delay - time routers take to process the
packet header
Queuing delay - time the packet spends in routing
queues
Transmission delay - time it takes to push the
packet's bits onto the link
Propagation delay - time for a signal to reach its
destination
2.6 Jitter
Jitter is the amount of variation in latency/response time,
in milliseconds. Reliable connections consistently report
back the same latency over and over again. Lots of
variation (or 'jitter') is an indication of problems [1]. Jitter
shows up as different symptoms, depending on the
application you're using. Web browsing is fairly resistant
to jitter, but any kind of streaming media (voice, video,
music) is quite suceptible to Jitter [3]. Jitter is a symptom
of other problems. It's an indicator that there might be
something else wrong. Often, this 'something else' is
bandwidth saturation (sometimes called congestion) - or
not enough bandwidth to handle the traffic load [14].
3. Analysis of Present Investigation
In a network environment, authorized users may access
data and information stored on other computers on the
network. The capability of providing access to data and
information on shared storage devices is an important
feature of many networks. The state of a network link can
be determined by measuring the throughput, the delay, the
jitter and the packet loss. These four properties represent
the quality of the link. In the following studies I try to
measuring these properties in following section.
3.1 First Study: Traffic on Network
Here measuring traffic on network for a exact node we can
collect the information about the state of that particular
node. The collected information provides help for network
administrator to optimize the system performance in
distributed computer system network. The network
administrator can analysis the performance of a node, a
subnet, or the whole network.
There are mainly two locations, when we can perform
passive network measurements in distributed computer
system network:
The state of a particular network node in
distributed computer system network, performing
a routing function or may be performing
forwarding functions. Virtual private networks,
firewalls and routers are the example of such
node in distributed computer system network.
The state of a service host, that provides a
network service in distributed computer system
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network. HTTP, FTP and DNS are the examples
of network service in distributed computer system
network.
The SNMP service is method for collecting the
measurements, But it increase network traffic. With the
help of tcpdump program we can analyze the network
traffic.tcpdump command will work on most flavors of
unix operating system. tcpdump allows us to save the
packets that are captured, so that we can use it for future
analysis. The saved file can be viewed by the same
tcpdump command. The tcpdump command have many
options. When we execute tcpdump command without any
option, it will capture all the packets flowing through all
the interfaces. With the use of -i option with tcpdump
command, allows us to filter on a selected ethernet
interface. Following show the use of tcpdump command
with –i option.
The simlified output is shown following.
A another command is also used for this perpose, which is
tcpstat. tcpstat is a highly configurable program that
measures some data and may generate some statistics if
wanted. tcpstat is to automatically search for an
appropriate interface, and to show current statistics on it.
The result of this command including bandwidth being
used, number of packets, average packet size, bytes since
last measurement, ARP packets since last measurement,
TCP packets since last measurement, ICMP packets since
last measurement.
The following command was executed on both nodes.
tcpstat -i eth0 \-o "%S %A %C %V %I %T %U %a %d
%b %p %n %N %l \n"
Interval is the sample interval, in seconds, in which the
statistics are based upon and when in default mode, how
often the display is updated. If -1 is given, then the interval
is taken to be the entire length of the sample. Default is 5
seconds.
The tcpstat program extracts some data from the host
node. These values are based on the data that has been
measured since last measurement. Sample output shown
following.
The following values are processed by tcpstat itself, and
can be viewed in the raw data log. The values are from left
to right in sample output.
Timestamp
Number of packet pass through interface
The average/mean packet size.
The standard deviation of the size of each packet.
The number of bits per second.
The distribution of the transport layer protocols show in
the following figure 2. The transport layer protocols are
TCP and UDP; these protocols are encapsulated within the
IP protocol.
Figure 2: Distribution of the Transport Layer Protocols for Node One
To study above output and result we can say that Node
One never utilize the available bandwidth. Node Two may
utilize the bandwidth fully.
3.2 Second Study: Throughput
It should be possible to measure arbitrary one-way
singleton characteristics (e.g., loss, median delay, mean
delay, jitter, 85th percentile of delay)By performing active
measurements from one node to another node with equal
link speed, the state of the connection can be determined.
If the link speed is not as anticipated, countermeasures can
be taken to locate and remove the bottleneck.
By using a active measurement tool, the connection
between two nodes are to be benchmarked and analyzed.
The test should provide enough information to see trends
in the network, and determine if the node manage to utilize
the available bandwidth. To remove uncertainties in the
results, benchmarking should be executed from one node,
to two other nodes.
There are many tools to perform active measurements.
Known network throughput benchmarking tools are:
netperf, iperf, ttcp, and ftp. Netperf is a benchmark that
can be use to measure various aspect of networking
performance. The primary foci are bulk (aka
unidirectional) data transfer and request/response
performance using either TCP or UDP and the Berkeley
Sockets interface. To execute the experiment, a server
node and a client node has to be installed on each of the
nodes.
Description Node
One
Node
Two
Node
Three
Processor Model AMD Intel Pentium
IV
Intel Pentium
IV
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Processor Mhz 1800 Mhz 2800 Mhz 2800 Mhz
Memory 1 GB 1 GB 512 MB
Operation
System
Ubuntu(Linux
Based)
Ubuntu(Linux
Based)
Ubuntu(Linux
Based)
Network MAC Ethernet Ethernet Ethernet
Network Link 100 Mb/s 100 Mb/s 100 Mb/s
ISP UNINETT UNINETT UNINETT
IP Address 192.168.1.100 192.168.1.120 192.168.1.124
Table 2: Resources configuration for study
Netperf has two types of command-line options. The first
are global command line options. They are essentially any
option not tied to a particular test or group of tests. An
example of a global command-line option is the one which
sets the test type - -t.
The second type of options are test-specific options. These
are options which are only applicable to a particular test or
set of tests. An example of a test-specific option would be
the send socket buffer size for a TCP_STREAM test.
Global command-line options are specified first with
test-specific options following after a -- as in:
netperf <global> -- <test-specific>
For the experiment, the server program was installed on
Node Two and three, and the client software was installed
on Node One.
3.3 Third Study: Packet Loss, Delay and Jitter
The delay can be measured as the time it takes for one
packet to be sent from one node to another. a host. When
the objects are timing nodes, the maximum delay only
applies to the path between the two nodes. It is well known
that the delay time in communication links follows the
exponential distribution.
Jitter, which represents the variations in the network delay,
is measured using a moving average computation
technique for a given stream of UDP packets, we can
notice that the variations in trends of the jitter
measurements occurred only for the first route change
along the path, which is shown in figure 3. The round trip
time is measured as the time it takes for one packet to be
sent from a node to a destination node, until another packet
is received from the destination node.
There are many tools for measuring the round trip time or
we can say delay in one way traffic. The tools results
depends on packet .The available packet formats can be
ICMP, TCP or UDP. The Each TCP packet consists of a
header followed by a data field. The header length can
vary between 20 and 60 bytes, and the total size of the
packet can be up to 65535 bytes. Actually, many systems
cannot handle packets as large as the protocol allows, and
a working maximum size is 576 bytes.
In this study a script is used and it is a part of the pinger
measurement package, which is used to measure round trip
times from links all around the world. This program
contains facilities to send various kinds of probe packets,
including ICMP Echo messages, process the reply and
record elapsed times and other information in a data file,
as well as produce real-time snapshot histograms and
traces.
Figure 3: Route Changes
The data collected from the nodes by the pinger script,
where each line represents one measurement. The sample
output show in following .
The pinger script extracts data gathered from the active
measurements, it also provides some processed data based
on the measured data. The following values are processed
from the ten round trip time values measured for that
measurement:
The minimum RTT of the ten packages sent in
that measurement
The mean RTT for the ten packages sent in that
measurement.
The maximum RTT of the ten packages sent in
that measurement.
The following figure 4 shows Phase plot of Node One
& Node Two.
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Figure 4 shows Phase plot of Node One & Node Two
Figure 5 Distribution of jitter
4. Conclusion
This paper explores different properties for the
administration for the distributed computer network
environment like techniques for measuring and analyzing
the performance. Computer network properties are
depends on different types of applications. This thesis
includes some simple methods for analyzing and
presenting the measured data, these data analysis is very
useful for administrator, who maintains the distributed
computer network. The three studies were expressing the
functionality of the tools used to measure the four
properties in quality of service.
The objective of first study is to make use of passive
throughput measurement tools, to monitor the traffic on
two different nodes for a particular time. In first case study
the tcpstat tool successfully measured the data on nodes
and provides all required information for analysis.
The objective of second study is to make use of active
throughput measurement tools, to benchmark the
distributed network connection between two different
nodes for a particular time.
The netperf tool successfully measured the throughput. In
this study, the results did not match the results that
predicated earlier. The mismatch generated due to limited
hardware recourses.
The objective of third study is to make use of active delay
measurement tools. The round trip time measurement used
to find the delay and the jitter of a connection. The packet
loss data can be used to figure out.
Important properties of the quality of network connection
are bandwidth, delay and reliability. The network
Administrator uses many troubleshooting software to
solving network problem regarding the quality of
connection.
5. References
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