system software suppor t for router fault tolerancelatex ieee journal style)

1. System Software Support for Router Fault Tolerance
Ashenafi W. Author1
, (Student, Adama)
1
Adama Science and Technology University, Ethiopia
School of Electrical Engineering and computing
Department of Computer Science and Engineering
(e-mail: ashenafiworkie@gmail.com
ABSTRACT Communication Network become shifted from dedicated physical network devices to the
high level of functional software component of those network devices. Fault tolerant network has an ability
to find or detect any irregular situation that might resulted in temporarily malfunctions or permanent faults.
Depends on topologies and protocols used an actual faults does occur multiple alarm alerts could be
generated through multiple network elements. Modern network management helps to determine the root
cause of faults regardless of its type which may occur and perform fault detection. Routers are the most
important traffic maintaining device in a communications network and core network equipment that forward
data packets between computer networks.
INDEX TERMS Router, Router Faults, Fault Tolerance, Generalized Algorithm of Fault Tolerance,
Reliability
I. INTRODUCTION
COMMUNICATION Network has shifted from common
physical network devices to the high level of functional
software component of those network utility. The functional
software package can be run as a software utility on any
hardware cross platform. Such package are expected to give
communication through these networks in an efficient and
transparent manner. The network efficiency relies on how
the above components are able to tolerate a faults which
could be malfunction or permanent fault. A system which
provides full functionality for its application and can recover
transparently from predefined faults is called a fault tolerant
system (Schagaev and Zalewski, 2001).
Fault tolerant network has an ability to find, detect any
unexpected situation that might resulted in temporarily mal-
functions (for seconds) to permanent faults (several days).
There are two major approach of increasing reliability with
respect to faults in a system; namely, 1) fault prevention and
2) fault tolerance. Avoiding all faults from a system is in
most cases impossible or may cause some problems such as
the delay or difficulty in maintenance. So it bases on fault
tolerant algorithms to manages faults regarding to the fol-
lowing scenario [5] based on topologies and protocols used
when an actual faults does occur multiple alarm alerts could
be generated through multiple network elements. This is said
to be fault detection phases. Modern network management
helps to determine the main cause of faults regardless of
its type which may occur and perform fault detection, fault
isolation processes and localization simultaneously.
The most important traffic regulating device in a commu-
nications network is the router. The sustainability of router
hardware and software will determine the reliability level of
a particular network. Depending on the character and strength
of the fault, the networks downtime may last from a few
seconds to several days. Very often such network failures
are caused by hardware malfunctions. The appearance and
manifestation of a hardware fault may cause errors in data
transmission. The normal way to recover an erroneous re-
ception of data is to request retransmission of the particular
packet(s). However, the fault might have happened inside a
router during the process of path computation/determination
and/or packet encapsulation. In this case, a packet could be
corrupted whilst being read from the input buffer, written into
the processor cache, processed, or written into output buffers.
Thus the overall reliable operation of a router becomes criti-
cally important for network efficiency and performance.
Routers is the most important traffic maintaining device
in a communications network [2] and core network equip-
ment that forward data packets between computer networks
in different way. Besides the fundamental packet routing
capability, modern routers incorporate a variety of extended
functionalities such as traffic management, packet filtering,
and virtual private networks (VPNs). For this reason, router
systems are also becoming extremely creating exceedingly
and complex high barriers to network innovations. Muham-
mad Azam, et al argue that the sustainability of router hard-
ware and software will determine the efficiency level of a
particular network. Depending on the character and strength
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2. Author et al.: System Software Support for Router Fault Tolerance
of the fault, the communication system crash from a few mi-
croseconds to several days. The manifestation and occurrence
of a hardware fault may cause errors in data transmission
in network communication. The normal way to recover an
erroneous reception of data is to request retransmission of
the particular packet(s). Although the fault might have hap-
pened inside a router during the process of path computation,
determination and/or packet encapsulation. In this case, a
packet could be corrupted whilst being read from the input
buffer, written into the processor cache, processed, or written
into output buffers. Thus the overall reliable operation of a
router becomes critically important for network efficiency
and performance
A. BASIC IP ROUTER STRUCTURE AND FUNCTIONS
Generally, the router performs two major tasks these are:
1) control routines path and Data control path (switching).
Routers maintain and manipulate routing tables; they listen
for updates and maintain changes in the routing tables to
reflect the new network topology. The topology network
in the core of the Internet and in organizational networks
is largely dynamic and changes very often. Routers also
divide packets and perform control actions on the packets;
it performs Layer 3 switching and sometimes maintains sta-
tistical data on the data-flow. Typically, packets are obtained
from inbound network interface; they are then handled by
the processing module (CPU), possibly put in the buffering
module.
Figure 1 Conventional router architecture
II. LITERATURE REVIEW
In recent years, several approaches have been investigated to
achieve a good fault tolerant system supports capability in
router.
[1] In the improvements of router reliability using the gen-
eralized algorithm of fault tolerance (GAFT) are presented
using time, structure and information types of redundancy.
But the limitation of the research Separation of toleration
of malfunction and permanent faults is not well discussed in
terms of their impact on system reliability
[4] Hossam M.A. Fahmy et.al propose a routing algorithm
to handle complex faults in multicomputer networks with
dimension-order routers. Simple changes to router structure
and routing logic are proposed but problem shown that its
performance in terms of bisection utilization and message
latency is challenging
[7] Authors improved the single link failure tolerance,
by reconfiguration and defining a new deterministic rout-
ing algorithm for all routers on a cycle-free around faulty
path link The following table show the detail literature
III. RESEARCH QUESTION
This paper try to investigate and answer the following ques-
tion
1) What are faults in communication network?
2) What are the major approach of increasing reliability
with respect to faults in a system?
3) What is the basic router architecture and functionality
describe it’s mechanisms for fault detection and recov-
ery?
4) How generalized algorithm of fault Tolerance (GAFT)
is used as fault detection and recovery and show fault
tolerance FT routing table works and show flow chart?
IV. OBJECTIVE
The objective of the study is to improve the performance of
the router through applying the generalized algorithm of fault
tolerance (GAFT) that bases on time structure, redundancy
of information and a scheme of reliability improvement for
router using system software recovery points.
V. METHODOLOGY
A. CLASSIFICATION OF NETWORK TYPICAL FAULTS
ARE:
• Line outages, a failure of circuit;
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3. Author et al.: System Software Support for Router Fault Tolerance
• White noise, caused by thermal energy;
• Impulse noise, burst errors like lightning and poor con-
nections
• Cross-talk, an adjacent circuit pickup signal from other
circuit;
• Attenuation, loosing of capability due to distance.
• Jitter, caused by variation of frequency modulation and
maximum of amplitude.
• Harmonic distortion, wrong amplify of input signal.
Such faults needed to tolerate using general algorithm
for fault detection and recovery.
B. GAFT IMPLEMENTATION FOR THE ROUTER
Generalized Algorithm of Fault Tolerance (GAFT) Fault de-
tection, fault type identification, faulty component location,
and hardware reconfiguration, to achieve a repairable state
and re-establishment of a correct state.GAFT steps are imple-
mentable using various redundancy types; can be performed
either synchronously or asynchronously using hardware or
software redundancy. Some examples of hardware (HW) and
software (SW) redundancy are:
• HW (I) - a hardware redundancy to keep extra informa-
tion for GAFT purposes such as redundant line or 1-bit
register of data to check errors of data;
• HW(T) â ˘A¸S detect hardware redundancy such as hard-
ware delay (latch) to avoid malfunctions caused by
racing of signals;
• SW(S) â ˘A¸S detect software redundancy such as periodic
hardware testing procedures performed;
• SW(I) - informational redundancy of the program delib-
erately applied to recover a system.
Recovery Points can be analysis mathematically
• the rate of permanent fault for the system is: pf1
• the malfunction rate of the system is: kpf1 The prob-
ability of operation without failure within time interval
[0,T) is determined by the formula:
P(t) = e−((1+k)pf1)t(1)
The efficiency of hardware and system
software implementation of fault tolerance differs in terms
of type and power of faults, the variety of faults tolerated
and on performance degradation. The GAFT is initiated by
external reasons with the function of detecting faults. A
special phase of GAFT is introduced to locate the correct
recovery points (RP) and further recover a state of the system
from the trusted recovery point (Schagaev 1986, 90). Once
is proved that the software state was not damaged or that the
recovery was successfully completed, the router operational
functioning is resumed.Both checking and recovery steps
and their implementations are important and unavoidable
elements of GAFT. Recovery points should be made during
the regular operation of a router and should also be monitored
by the system software. Note that this statistical evaluation
of reliability includes two different processes (malfunctions
and permanent fault appearance) which are considered as two
independent random processes.
Fault tolerance can be implemented or supported using
different levels of time or structural redundancies within
hardware and system software. System software support for
fault tolerance assumes several levels of implementation.
These levels are instruction level, procedure level, module
level and task level (Schagaev, 2008), as shown in Figure 3
Figur2 GAFT router
The distributed processing architecture of the router (central
route processing and local processing subsystem) enables
mutual checking and recovery procedures to be performed
and excludes the core of the router in terms of reliability.
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4. Author et al.: System Software Support for Router Fault Tolerance
Distributed processing archtecture [1]Azam, N. Ioannides,
M. H. Rummeli, and I. Schagaev (2009)
VI. CONCLUSION
The approaches for router reliability clearly stated .General-
ized algorithm of fault tolerance were proposed to overcome
the problem of improving reliability in case router hardware
components. Router hardware is the major drawback in im-
proving reliability therefore, it is better to use software sup-
ports to handle such faults. Flexible real-time fault tolerant
systems apply different steps of the algorithm making an
option to design
The implementation of an algorithm assumes support and
coordination of the process of hardware checking and com-
posed of three sets of recovery points routing, inbound, and
outbound hardware of the router respectively. The recovery
procedures include searching of the correct recovery point
to restart operation; probability of this procedure depends on
quality and consistency of checking procedures. During the
recovery actions might be implemented in different router
hardware segments; thus reducing performance degradation
of the router as a whole even in recovery process. Distributed
architecture processing of the router (central route processing
and local processing subsystem) enables to perform mutual
verifying and recovery steps excluding core of the router in
terms of transparency.
.
APPENDIX A REFERENCE EXAMPLES
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ASHENAFI W DESSALGN. AUTHOR Ashenafi
Workie studied his Bsc at Adama Science and
Technology University in faculty of comput-
ing Software Engineering department in july 9
2016.Now He is pursuing Master of Computer
Science and Engineering at the same university
he did his Bsc. His research interest is Software
Engineering,computer Vision and Wireless sensor
network.
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