This paper describes the network response time which represent a significant indicator for network performance and how load balancing can improve the network performance.response time, load balancing, throughput, network performance

Madalina MLAK

English

Research Papers in Economics

Revista Informatica Economică, nr. 4 (44)/2007  64 
Analyzing the Network Response Time and Load Balancing 
 
Mădalina MLAK, Bucharest, Romania, Madalina.Mlak@ie.ase.ro  
 
This paper describes the network response time which represent a significant indicator for 
network performance and how load balancing can improve the network performance. 
Keywords: response time, load balancing, throughput, network performance 
 
esponse time is the total time it takes 
from when a request will wait to receiv-
ing a response.  
For network, the number of bits counted di-
vided by the media speed determines the net-
work response time. 
A basic advice regarding response time has 
been about the same for 40 years ago [1]. 
2. Types of response time 
The main categories of response time are the 
following: 
- CPU or processing response time; 
In real-time systems the response time of 
process or thread is the time elapsed between 
when task is ready to execute and the time 
when is finishes the job. 
In data processing, the response time per-
ceived by the end user is the interval between 
the instant at which a user at a terminal enters 
a request for a response from a computer and 
the instant at which the first character of the 
response is received at the terminal. 
-  disk response time; 
Disk response time is the total time it takes to 
serve a request on disk. 
-  monitor response time; 
Response time for monitors is the amount of 
time a pixel in a monitor takes to go from ac-
tive to inactive and back to active again. 
Long response time creates blur pattern 
around moving objects. 
- server response time; 
Server response time is the total time it takes 
to serve a request on server. 
The response time of a server is the sun of 
the weight of the processes assigned to it. 
-  proxy response time; 
Proxy response time is the total time it takes 
to serve a client request. 
-  message response time; 
For communications the response time is the 
interval between receipt the end of transmis-
sion of an inquiry a message and the begin-
ning of transmissions of a response message 
to the source station. 
-  network response time. 
Network response time refers to the amount 
of time it takes to send a request and wait for 
a response to come back using a network. 
Network response time involve bi-directional 
traffic from source to destination (only in the 
client-to-server direction). 
In the following, is referring network re-
sponse time.  
3. Factors which affect the network re-
sponse time 
The following situations can affect the net-
work response time: 
-  a congestion path or limited path 
can indicate a slower response time; 
If the response time for each successive user 
will be longer that the previous one, that re-
sult that the average response time will grow 
without limits and the network will have 
congestion. A solve of this problem are limit-
ing the number of users and this implies that 
the average response time has a stabile value. 
- if the connection is broken, the response 
time is absent; 
A solve of this physic problem is to use ping 
message to localize the place. 
Use ping to find response time from several 
hosts of the network. If the response time 
from one host is absent or is not in a good 
field, you can analyze the host. Physical 
problems are caused by the following rea-
sons: missing terminations, loose cables, 
loose connectors, improper grounding or re-
flection of signal. 
- when the network response time become 
greater and the operating of networks are 
timing out, the reason may be broadcast 
storm (burst).  
As conscience the user cannot log to servers 
  R
 Revista Informatica Economică, nr. 4 (44)/2007  65
or access services. In the end, the network 
becomes unusable. A solve of this problem is 
growing of throughput. 
- a growing in using of network can de-
termine a poor response time and a sloe 
network performance.  
A solve of this problem is segmentation of 
network and determine the users’ domains. 
4. Measuring and calculating response 
time 
Response time measures the total time that 
system takes to serve a request. This time in-
cludes latency. Do not confuse response time 
with latency.  
Latency represent the delay in communicat-
ing a message “spend” in the network. La-
tency is the amount of time takes for a packet 
to reach its destination after it is transmit and 
it increases when the network has a bottle-
neck. 
Latency is affected by physical component 
and utilization of network.  
Response time can affect by changes in the 
processing time of your system and by 
changes in latency, which occur due the 
change in hardware resource or utilization. 
Response time measurement may be made 
by: 
- operating system commands; 
- operating system performance monitor; 
- applications. 
For example, UNIX command time output 
the amount of elapsed time (real), the user 
CPU time and the system CPU time and is 
good for CPU response time. You can use 
this command to invoke an instance of your 
application or perform a data base operation. 
 In Windows, you can use Performance Mo-
nitor to measure user time, processor time 
and elapsed time. 
The output of ping (one per second) gives 
you the round trip response time (RTT). 
Ping doesn’t use TCP or UDP to measure re-
sponse time. It uses ICMP (Internet Control 
Management Protocol), so the test can lead to 
inaccurate results. ICMP packets are smaller 
than TCP or UDP packets and ICMP may be 
handled differently by connecting devices 
such as routers, because has a diminished 
priority from busy routers and can produce 
unreliable results. Putting ping test near the 
devices for analyze you can reduce ping 
overhead and can produce more reliable re-
sults. For small network the difference be-
tween ping and other TCP applications for 
test response time may be negligible. I-t is 
much better to use for measure response time 
a separate monitoring application to collect 
highly reliable measurements for analyze. 
Note: The response time of a single request 
isn’t representative in all cases for the typical 
response time of the system. For have a good 
measure of response time will usually calcu-
late the average response time of many re-
quests. 
To measure response time choose a traffic 
type for which you like to investigate re-
sponse time. For example: HTTP traffic it will 
be analyzes response time on the Web. 
Response time is usually measured in sec-
onds/request. 
To calculate response time use formula: 
response time = latency + processing time 
On systems where the CPU is not necessarily 
busy, such as a client system, the benefit of 
offloading checksum may be seen in better 
network response time, rather than in no-
ticeably improved throughput. 
Parallel database systems and multi-user mod 
is required to achieve high throughput and 
for reducing response time. 
Throughput and  response time are linearly 
related and the influence is reciprocal of one 
another. Throughput and response time are 
inversely proportional. 
Throughput is the rate at which a computer 
or network sends or receives data. 
To calculate throughput use formula: 
throughput  = 1/ response time 
Response time is a performance indicator for 
a network, like the throughput. 
If response time increases when the load is 
increased, the degradation of system per-
formance (implicit network) is greater. A 
poorly scaling application is indicated by re-
sponse time that degrades gradually as more 
users are added.  
We can reduce the response time for each 
user by reducing wait times or increase 
throughput. This throughput will be main-
 Revista Informatica Economică, nr. 4 (44)/2007  66 
tained. 
And the driver must periodically adjust the 
hardware and software to maximize the 
throughput and response time. 
5. Response time for Web applications 
End-to-end Web performance is influent by 
many factors including Web server platform, 
protocol and network characteristics. 
Exists the following alternatives Web serving 
architectures [2] on client-perceived response 
time and the information may be place like 
following: 
- single server location; 
The classical approach of storing information 
in a single data center that uses a single net-
work provider. 
- single server location with multiple ISPs; 
The data center provides direct connectivity 
to many ISPs to provide performance and 
availability usually with additional control 
over BGP routing. 
- multiple server locations; 
The information is placed in few regional da-
ta center to improve performance and avail-
ability. 
- widely distributed servers. 
The information is served from a distributed 
network which has a set of small servers 
spread across many service providers. 
Each of these steps in communication intro-
ducing its own delay in getting a Web page 
from the serve to the user and those delays 
are cumulative: 
- the throughput of the server; 
- server’s connection to Internet; 
- Internet itself (has bottleneck especially 
for cross-continent connections and for 
use at peak hours); 
- the user’s connection to Internet; 
- speed of the user’s browser application; 
- speed of the user’s computer; 
- upgrade of the software and for the dri-
ver of hardware. 
6. Managing network response time 
Performance management can manage re-
sponse time. Network performance is meas-
ured in throughput and response time. For 
performance of system and for the network 
performance it is desirable that all processes 
get a minimum response time (waiting time) 
and a maximum CPU utilization and 
throughput. 
Response time varies with the amount of 
bandwidth available for applications and for 
communications. 
To improve the traffic it is recommended 
load balancing and traffic analyze. 
7. Load balancing 
Load balancing is the process of improving 
the performance of system through a distri-
bution of loads among the processors. 
In network refers to balancing a workload 
amongst multiple computer devices. 
The load balancing analysis is based on load 
balancing algorithms. 
Load balancing and capacity planning im-
prove the network performance and has ef-
fect on network response time. 
Load balancing options [3] for network con-
nections: 
- least numbers of open connections to the 
server; 
At Web sites where are servers with differ-
ence between performance, this option per-
forms very well. 
- weight to each server with percent; 
In this option, servers with a higher activity 
will receive a larger percentage of connec-
tions. 
- Round Robin policy; 
This option directs the network connection to 
the next server and treats all servers as equal 
numbers of connections or response time. 
Round Robin is superior because not exists 
propagation delay. When a server is not re-
sponding we can determinate that. 
- fastest connections to the server; 
This option directs the network connections 
to the server with the fastest response time. 
Web-server performance does not follow a 
linear progression of response time to num-
ber of connections. In this situation, this op-
tion will tend to overload a particular server 
before moving on to another. 
- setting maximum number of connections. 
Specifying the maximum number if connec-
tions for each server and setting this limit 
which a server can accept, you can avoid ex-
ceeding the capacity limit of the server. 
 
 Revista Informatica Economică, nr. 4 (44)/2007  67
Bibliography 
  [1] Miller, R.B. – Response time in man-
computer conversational transaction – Vol. 
33 Proc. AFIPS Fall Join Computer Confer-
ence, 1968 
[2] IBM research 
[3] www.cisco.com - Load Balancing Op-
tions 
[4] Kai Shen, Tao Yang, and Lingkun Chu - 
Cluster Load Balancing for Fine-grain Net-
work Services - Department of Computer 
Science - University of California at Santa 
Barbara 
[5] Erhard Rahm, Robert Marek - Analysis of 
Dynamic Load Balancing Strategies for Par-
allel Shared Nothing Database Systems -
University of Kaiserslautem , Germany 
[6] Sameer Bataineh, Jamal Al-Karaki - 
Closed form solution for response time of 
fault tolerant network of processors - Com-
puters & Electrical Engineering, Volume 30, 
Issue 4 , June 2004, Pages 291-308 
[7]  Robin Schumacher - Response-Time 
Analysis Made Easy in Oracle Database 10g 
(www.oracle.com)
 

Jamal Al-Karaki -Closed form solution for response time of fault tolerant network of processors -

Load Balancing Options

Response time in mancomputer conversational transaction –

Response-Time Analysis Made Easy in Oracle Database 10g (www.oracle.com)

Robert Marek - Analysis of Dynamic Load Balancing Strategies for Parallel Shared Nothing Database Systems -University of Kaiserslautem ,

Tao Yang, and Lingkun Chu -Cluster Load Balancing for Fine-grain Network Services -

Analyzing the Network Response Time and Load Balancing

http://www.revistaie.ase.ro/content/44/7%20mlak.pdf

Analyzing the Network Response Time and Load Balancing

Abstract

Similar works

Full text

Available Versions

Research Papers in Economics