Performance evaluation of real time applications for RIP, OSPF and EIGRP for flapping links using OPNET modeler

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Performance evaluation of real time applications for RIP, OSPF and EIGRP for flapping links using OPNET modeler. This paper investigates the performance of voice and video traffic in RIP, OSPF and EIGRP for flapping unstable links. We are considering the use of OPNET simulation tool to analyze the performance of these routing protocols i.e. RIP, OSPF and EIGRP.
International Journal of Computer Networks and Communications Security
VOL. 3, NO. 1, JANUARY 2015, 16–26
Available online at: www.ijcncs.org
E-ISSN 2308-9830 (Online) / ISSN 2410-0595 (Print)
Performance Evaluation of Real Time Applications for RIP, OSPF
and EIGRP for flapping links using OPNET Modeler
ARSALAN IQBAL1 and SAMEER LIAQAT ALI KHAN2
1 Network & Communications Infrastructure, IT Department, Georgian College, Barrie, ON, Canada
2 Computer Networks Department, Ryerson University, Toronto, ON, Canada
E-mail: 1arsalan.iqbal@georgiancollege.ca, 2sameerliaqatali.khan@ryerson.ca
ABSTRACT
Present day Internet and communication systems heavily rely on the basis of IP Routing protocols. These
different routing protocols are mainly categorized as static, dynamic and hybrid routing protocols. The
selection of these routing protocols depends upon the network requirement and performance parameters of
different real time applications. This paper investigates the performance of voice and video traffic in RIP,
OSPF and EIGRP for flapping unstable links. We are considering the use of OPNET simulation tool to
analyze the performance of these routing protocols i.e. RIP, OSPF and EIGRP. In this investigation the
impact of flapping links on convergence time, packet end-to-end delay, packets drop in IP network, voice
jitter, video packet delay variation and HTTP page response time is considered. The simulated results
showed that flapping links have a significant impact on the overall performance of IP based networks
affecting specially the network convergence time and packet drops in the network.
Keywords: Routing Protocols, Real Time Applications, Link flapping, Unstable networks.
1
INTRODUCTION
destination
node.
For
the
success
of
network,
routing protocols play the crucial role.
Today's technology is based on IP routing [1],
In
this
paper
three
routing
protocols,
RIP
[14],[15].
There
are
commonly
used
routing
(distance
vector
protocol),
OSPF
(link
state
protocols like Routing Information Protocol (RIP),
protocol)
and
EIGRP
(hybrid
protocol)
are
Open Shortest Path First (OSPF) and Enhanced
analyzed on the basis of convergence time, point-
Interior
Gateway
Routing
Protocol
(EIGRP).
to-point link utilization, queuing delay, packet drop,
Communication through routing protocols depends
voice/video
data
packet
delay
and
HTTP
page
on the algorithm which in turn is based on the
response
time.
The
scheme
of
the
paper
is
as
metrics. These metrics are used to calculate the
follows:
optimum path to transfer data from one network to
the other. Routing protocols are essentially
separated into two categories. First type is the
interior gateway routing protocols which are
distance vector, link state and hybrid routing
Implementation of routing protocols on
simulation tool
Setting up performance metrics
Analysis of results of simulation
protocol. RIP, OSPF, IGRP and EIGRP are the
cases of interior gateway routing protocols. Second
Comparison of results
type is the exterior gateway routing protocols. BGP
and MP BGP are the examples of exterior gateway
2
RELATED TECHNOLOGIES
routing protocols. The basic routing protocols move
traffic across the networks [4] and the
corresponding routers should be aware of where
they forward the data in order to reach the correct
2.1 Routing Information Protocol (RIP)
The Routing Information Protocol (RIP) is a
distance-vector based algorithm. RIP is one of the
first routing protocols used on TCP/IP. Data
17
A. Iqbal and S. L. Ali Khan / International Journal of Computer Networks and Communications Security, 3 (1), January 2015
packets are sent through the network using UDP.
• Route
lookup
for
every
packet
load
Each
router
using
this
protocol
has
limited
balancing on per packet basis
knowledge of the network around it. This simple
• It
disables
route
caching
which
is
not
protocol uses a hop-count mechanism to find an
suitable for high speed interfaces
optimal
path
for
packet
routing
[1],
[18].
A
• It can be configured on an interface with
maximum of 16 hops are employed to avoid routing
the command: no iproute-cache
loops, thus limiting the size of the networks that
this protocol may support. The popularity of this
b)
Fast Switching
protocol is largely due to its simplicity and easy
• Route
lookup
for
the
first
packet
to
a
configuration.
Its
disadvantages
are
slow
destination
convergence times, and its limit on scaling further.
• Then installs that route in the route cache
So,
this
protocol
performed
well
for
small
to
forward
subsequent
packets
for
the
networks.
same destination along the same route
• Selects
different
routes
for
different
2.1.1
Hold-Down and Triggered Update
destinations
load
balancing
on
per
There are different timers associated with RIP
and these timers become very important in making
RIP one of beneficial routing protocols. Split
horizon is a process of avoiding loops in RIP but
there are some situations when Split horizon fails.
This failure can be avoided by wisely using
different timers in RIP. This can be avoided by
'triggered update' means a node sends update as
destination bases
• The default mode in CISCO routers
• It can be configured on an interface with
the command: iproute-cache
Express Forwarding: iproute cache cef – FIB +
Adjacencies to keep L2 information
Distributed Forwarding: iproute cache distributed –
FIB is distributed in every line card.
soon as it discovers any change in its cost. It allows
fast re-convergence.
2.2
Open Shortest Path First (OSPF)
Hold down time is a situation when a node does
Open Shortest Path First is a routing protocol that
not accept route from other side for this hold down
was developed by the Interior Gateway Protocol
time and so when it receives an update from any
(IGP) working group of the Internet Engineering
other node with higher cost, then it sets up the hold
Task Force
for Internet Protocol (IP) networks.
down timer for that route, means put the route in
OSPF is a protocol based on link state routing that
hold down state. During this time, it does not accept
is used to distribute information within a single
any route, sets the route unreachable and advertises
autonomous system [8], [12], [13]. In 1989, the first
that
it
is
unreachable.
Hold
down
time
adds
version of OSPF was defined as OSPFv1, which
skepticism to accepting new high cost path, because
was published in RFC 1131. The OSPFv2 was
if high cost path has been propagated throughout
introduced in 1998, found in RFC 2328. In 1999,
the system it may potentially cause loop. Triggered
OSPFv3 was released for IPv6, published in RFC
updates may cause excessive load in the network,
2740 [14].
e.g. broadcasts any change in the route to N1 to A
and B on N2. This causes both A and B generate
2.2.1
OSPF Cost
triggered update on N3 so to avoid generating
excessive load, triggered updates are generated at a
random interval of 1-5/Sec.
The path cost of an interface in OSPF is called
metric that indicates standard value such as speed.
The cost of an interface is calculated on the basis of
2.1.2
Equal Cost Multipath Routing
bandwidth. Cost is inversely proportional to the
bandwidth. Maximum bandwidth is achieved with a
When a router learns multiple routes to a network
lower cost [12].
(or subnet) with similar cost, then the selection
Where 108 (100000000 bps) is a default value
among
those
routes
is
regarded
as
equal
cost
which is called reference bandwidth.
multipath routing. It allows load sharing among
equal cost routes. There are two approaches to use
2.2.2
Shortest Path First (SFP) Algorithm
equal cost multipath routes:
OSPF is a link state routing protocol that uses
a)
Process Switching
• Round robin – select different route for
every packet in a round robin fashion
shortest path first algorithm to calculate the least
cost path to all known points of destination.
Dijkstra Algorithm [4], [15] is used for getting the
smaller path. Different procedures of this algorithm
are given below:
18
A. Iqbal and S. L. Ali Khan / International Journal of Computer Networks and Communications Security, 3 (1), January 2015
For any change in routing information, link
state information is created by router. This
advertisement gives all link states information
on that particular router.
Fig. 1. EIGRP metric calculation formula
All routers exchange LSAs by flooding. The
For weights, the default values are:
link state information is collected by each
router and its copy is stored in link state
database. This link state update is forwarded
K1=1, K2=0, K3=1, K4=0, K5=0
These default values efficiently trim
above formula to:
down
the
to all other routers.
After creation
calculation of
of database, routers begin
shortest path tree to the
Fig. 2. EIGRP default metric
destinations. For finding the small path, the
router uses Dijkstra Algorithm.
The formula that EIGRP uses to calculate scale
bandwidth is:
If any changes present in the OSPF network
such as link cost, new network being included
or deleted, Dijkstra Algorithm is calculated
again to get the least cost path.
Here ( ) is in kilobits per seconds that represents
the minimum bandwidth on the interface to
All other router uses this algorithm at the root of
the tree to get the shortest path on the base of cost
to reach the destinations [10], [15].
destination. The formula that EIGRP uses to
calculate scale bandwidth is:
Delay= D (n)*256
Where D (n) represented in microseconds and it is
2.3
Enhanced Interior Gateway Routing Protocol
the sum of delays configured on the interface.
(EIGRP)
Enhanced Interior Gateway Routing Protocol
(EIGRP) is a Cisco proprietary protocol, which is
an improved version of the interior gateway routing
protocol (IGRP) [12]. EIGRP is being used as a
scalable protocol in both medium and large scale
networks since 1992. EIGRP is said to be an
extensively used IGP where route computation is
done through Diffusion Update Algorithm (DUAL)
[2]. However, EIGRP can also be considered as
hybrid protocol because of having link state
protocol properties [1].
2.3.2 Diffusion Update Algorithm
Anytime an input event occurs that changes an
existing route, the router performs local
computation. When router performs local
computation the route remains in passive state. If
one or more feasible successors are found, select
one with the lowest distance as the new successor.
The route distance is changed but the FD may not.
If no feasible successor is found, the route is
changed to active state and diffusing computation is
initiated. The router sends query to all its
neighbors, which contains its new distance it keeps
2.3.1 EIGRP Metrics
With the use of total delay and minimum link
bandwidth, it is possible to get the routing
information like metrics in EIGRP. Composite
metrics which consists of bandwidth, reliability,
delay and load are considered for the purpose of
calculating the preferred paths in the networks. The
EIGRP routing update [7] takes the hop count into
account though EIGRP does not include hop count
as a component of composite metrics. The total
the route in active state until it either receives
replies to all its queries or active time expires. It
calculates new feasible successors and update
distance and FD values. If the diffusing
computation does not result into a positive distance,
the destination is declared unreachable. The
Diffusion Update Algorithm (DUAL) uses
following provisions and theories which have
significant role in loop-avoidance mechanism [6],
[12], [17]:
delay and the minimum bandwidth metrics can be
achieved from values [3] which are put together on
interfaces. The formula used to compute the metric
is shown in the figure below:
2.3.3 Feasible Distance (FD)
The lowest cost needed to reach the destination is
usually termed as the feasible distance for that
specific destination.
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Performance evaluation of real time applications for RIP, OSPF and EIGRP for flapping links using OPNET modeler. This paper investigates the performance of voice and video traffic in RIP, OSPF and EIGRP for flapping unstable links. We are considering the use of OPNET simulation tool to analyze the performance of these routing protocols i.e. RIP, OSPF and EIGRP..

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International Journal of Computer Networks and Communications Security VOL. 3, NO. 1, JANUARY 2015, 16–26 Available online at: www.ijcncs.org E-ISSN 2308-9830 (Online) / ISSN 2410-0595 (Print) Performance Evaluation of Real Time Applications for RIP, OSPF and EIGRP for flapping links using OPNET Modeler ARSALAN IQBAL1 and SAMEER LIAQAT ALI KHAN2 1 Network & Communications Infrastructure, IT Department, Georgian College, Barrie, ON, Canada 2 Computer Networks Department, Ryerson University, Toronto, ON, Canada E-mail: 1arsalan.iqbal@georgiancollege.ca, 2sameerliaqatali.khan@ryerson.ca ABSTRACT Present day Internet and communication systems heavily rely on the basis of IP Routing protocols. These different routing protocols are mainly categorized as static, dynamic and hybrid routing protocols. The selection of these routing protocols depends upon the network requirement and performance parameters of different real time applications. This paper investigates the performance of voice and video traffic in RIP, OSPF and EIGRP for flapping unstable links. We are considering the use of OPNET simulation tool to analyze the performance of these routing protocols i.e. RIP, OSPF and EIGRP. In this investigation the impact of flapping links on convergence time, packet end-to-end delay, packets drop in IP network, voice jitter, video packet delay variation and HTTP page response time is considered. The simulated results showed that flapping links have a significant impact on the overall performance of IP based networks affecting specially the network convergence time and packet drops in the network. Keywords: Routing Protocols, Real Time Applications, Link flapping, Unstable networks. 1 INTRODUCTION Today's technology is based on IP routing [1], [14],[15]. There are commonly used routing protocols like Routing Information Protocol (RIP), Open Shortest Path First (OSPF) and Enhanced Interior Gateway Routing Protocol (EIGRP). Communication through routing protocols depends on the algorithm which in turn is based on the metrics. These metrics are used to calculate the optimum path to transfer data from one network to the other. Routing protocols are essentially separated into two categories. First type is the interior gateway routing protocols which are distance vector, link state and hybrid routing protocol. RIP, OSPF, IGRP and EIGRP are the cases of interior gateway routing protocols. Second type is the exterior gateway routing protocols. BGP and MP BGP are the examples of exterior gateway routing protocols. The basic routing protocols move traffic across the networks [4] and the corresponding routers should be aware of where they forward the data in order to reach the correct destination node. For the success of network, routing protocols play the crucial role. In this paper three routing protocols, RIP (distance vector protocol), OSPF (link state protocol) and EIGRP (hybrid protocol) are analyzed on the basis of convergence time, point-to-point link utilization, queuing delay, packet drop, voice/video data packet delay and HTTP page response time. The scheme of the paper is as follows: • Implementation of routing protocols on simulation tool • Setting up performance metrics • Analysis of results of simulation • Comparison of results 2 RELATED TECHNOLOGIES 2.1 Routing Information Protocol (RIP) The Routing Information Protocol (RIP) is a distance-vector based algorithm. RIP is one of the first routing protocols used on TCP/IP. Data 17 A. Iqbal and S. L. Ali Khan / International Journal of Computer Networks and Communications Security, 3 (1), January 2015 packets are sent through the network using UDP. Each router using this protocol has limited knowledge of the network around it. This simple protocol uses a hop-count mechanism to find an optimal path for packet routing [1], [18]. A maximum of 16 hops are employed to avoid routing loops, thus limiting the size of the networks that this protocol may support. The popularity of this protocol is largely due to its simplicity and easy configuration. Its disadvantages are slow convergence times, and its limit on scaling further. So, this protocol performed well for small networks. 2.1.1 Hold-Down and Triggered Update There are different timers associated with RIP and these timers become very important in making RIP one of beneficial routing protocols. Split horizon is a process of avoiding loops in RIP but there are some situations when Split horizon fails. This failure can be avoided by wisely using different timers in RIP. This can be avoided by 'triggered update' means a node sends update as soon as it discovers any change in its cost. It allows fast re-convergence. Hold down time is a situation when a node does not accept route from other side for this hold down time and so when it receives an update from any other node with higher cost, then it sets up the hold down timer for that route, means put the route in hold down state. During this time, it does not accept any route, sets the route unreachable and advertises that it is unreachable. Hold down time adds skepticism to accepting new high cost path, because if high cost path has been propagated throughout the system it may potentially cause loop. Triggered updates may cause excessive load in the network, e.g. broadcasts any change in the route to N1 to A and B on N2. This causes both A and B generate triggered update on N3 so to avoid generating excessive load, triggered updates are generated at a random interval of 1-5/Sec. 2.1.2 Equal Cost Multipath Routing When a router learns multiple routes to a network (or subnet) with similar cost, then the selection among those routes is regarded as equal cost multipath routing. It allows load sharing among equal cost routes. There are two approaches to use equal cost multipath routes: a) Process Switching • Round robin – select different route for every packet in a round robin fashion • Route lookup for every packet – load balancing on per packet basis • It disables route caching which is not suitable for high speed interfaces • It can be configured on an interface with the command: no iproute-cache b) Fast Switching • Route lookup for the first packet to a destination • Then installs that route in the route cache to forward subsequent packets for the same destination along the same route • Selects different routes for different destinations – load balancing on per destination bases • The default mode in CISCO routers • It can be configured on an interface with the command: iproute-cache Express Forwarding: iproute cache cef – FIB + Adjacencies to keep L2 information Distributed Forwarding: iproute cache distributed – FIB is distributed in every line card. 2.2 Open Shortest Path First (OSPF) Open Shortest Path First is a routing protocol that was developed by the Interior Gateway Protocol (IGP) working group of the Internet Engineering Task Force for Internet Protocol (IP) networks. OSPF is a protocol based on link state routing that is used to distribute information within a single autonomous system [8], [12], [13]. In 1989, the first version of OSPF was defined as OSPFv1, which was published in RFC 1131. The OSPFv2 was introduced in 1998, found in RFC 2328. In 1999, OSPFv3 was released for IPv6, published in RFC 2740 [14]. 2.2.1 OSPF Cost The path cost of an interface in OSPF is called metric that indicates standard value such as speed. The cost of an interface is calculated on the basis of bandwidth. Cost is inversely proportional to the bandwidth. Maximum bandwidth is achieved with a lower cost [12]. Where 108 (100000000 bps) is a default value which is called reference bandwidth. 2.2.2 Shortest Path First (SFP) Algorithm OSPF is a link state routing protocol that uses shortest path first algorithm to calculate the least cost path to all known points of destination. Dijkstra Algorithm [4], [15] is used for getting the smaller path. Different procedures of this algorithm are given below: 18 A. Iqbal and S. L. Ali Khan / International Journal of Computer Networks and Communications Security, 3 (1), January 2015 • For any change in routing information, link state information is created by router. This advertisement gives all link states information on that particular router. • All routers exchange LSAs by flooding. The link state information is collected by each router and its copy is stored in link state database. This link state update is forwarded to all other routers. Fig. 1. EIGRP metric calculation formula For weights, the default values are: K1=1, K2=0, K3=1, K4=0, K5=0 These default values efficiently trim down the above formula to: • After creation calculation of of database, routers begin shortest path tree to the Fig. 2. EIGRP default metric destinations. For finding the small path, the router uses Dijkstra Algorithm. • If any changes present in the OSPF network such as link cost, new network being included The formula that EIGRP uses to calculate scale bandwidth is: or deleted, Dijkstra Algorithm is calculated again to get the least cost path. All other router uses this algorithm at the root of the tree to get the shortest path on the base of cost to reach the destinations [10], [15]. 2.3 Enhanced Interior Gateway Routing Protocol (EIGRP) Enhanced Interior Gateway Routing Protocol (EIGRP) is a Cisco proprietary protocol, which is an improved version of the interior gateway routing protocol (IGRP) [12]. EIGRP is being used as a scalable protocol in both medium and large scale networks since 1992. EIGRP is said to be an extensively used IGP where route computation is done through Diffusion Update Algorithm (DUAL) [2]. However, EIGRP can also be considered as hybrid protocol because of having link state protocol properties [1]. 2.3.1 EIGRP Metrics With the use of total delay and minimum link bandwidth, it is possible to get the routing information like metrics in EIGRP. Composite metrics which consists of bandwidth, reliability, delay and load are considered for the purpose of calculating the preferred paths in the networks. The EIGRP routing update [7] takes the hop count into account though EIGRP does not include hop count as a component of composite metrics. The total delay and the minimum bandwidth metrics can be achieved from values [3] which are put together on interfaces. The formula used to compute the metric is shown in the figure below: Here ( ) is in kilobits per seconds that represents the minimum bandwidth on the interface to destination. The formula that EIGRP uses to calculate scale bandwidth is: Delay= D (n)*256 Where D (n) represented in microseconds and it is the sum of delays configured on the interface. 2.3.2 Diffusion Update Algorithm Anytime an input event occurs that changes an existing route, the router performs local computation. When router performs local computation the route remains in passive state. If one or more feasible successors are found, select one with the lowest distance as the new successor. The route distance is changed but the FD may not. If no feasible successor is found, the route is changed to active state and diffusing computation is initiated. The router sends query to all its neighbors, which contains its new distance it keeps the route in active state until it either receives replies to all its queries or active time expires. It calculates new feasible successors and update distance and FD values. If the diffusing computation does not result into a positive distance, the destination is declared unreachable. The Diffusion Update Algorithm (DUAL) uses following provisions and theories which have significant role in loop-avoidance mechanism [6], [12], [17]: 2.3.3 Feasible Distance (FD) The lowest cost needed to reach the destination is usually termed as the feasible distance for that specific destination. 19 A. Iqbal and S. L. Ali Khan / International Journal of Computer Networks and Communications Security, 3 (1), January 2015 2.3.4 Reported Distance (RD) 4 SYSTEM DESIGN A router has a cost for reaching the destination and it is denoted as reported distance. 2.3.5 Successor A successor is basically an adjacent router which determines the least-cost route to the destination. a) Feasible Successor (FS) FS is an adjacent router which is used to offer a loop free backup path to the destination by fulfilling the conditions of FC. b) Feasible Condition (FC) After the condition of FD is met, FC is used in order to select the reasonable successor. The RD advertised by a router should be less than the FD to the same destination for fulfilling the condition. 2.3.6 EIGRP Convergence Local computation does not involve message exchange among routers. Feasible successor is central to fast convergence, because when feasible successors are available then the router performs local computation and avoids diffusing computation. It also helps in reducing the diffusing computation cost as the query chain stops at a router that performs local computation. For this research, the system is designed using [16] OPNET modeler version 15. The implementation is done for RIP, OSPF and EIGRP routing protocols. To get accurate results the topology has been implemented exactly with the same number of devices (routers, servers and clients). The parameters are convergence time, packet drop, packet end-to-end delay for voice/ video traffic, queuing delay, link utilization and HTTP page response time. Standard application definition, profile definition, IP QoS and failure-recovery has been applied for the voice, video and http traffic for all the three routing protocols i.e. RIP, OSPF and EIGRP. Figure 3 shows the RIP implementation for voice, video and HTTP traffic. To accomplish more real world statistics, some background traffic has been generated using the demand model of OPNET modeler. The demand model is set in a way that background traffic is running in the whole network between the clients and servers through the routers. For the demand model the parameters set for traffic intensity are 900,000 bits/sec and 900 packets/ sec. 3 REAL TIME APPLICATION (RTA) A real time application [5], [9], [11] is a program that works in a time duration which user senses as current. The latency must be less than a decided value, generally calculated in seconds. Whether or not a given application qualifies as RTA is based on bad execution time (WCET), the max length of time a predefined task or group of actions requires on a provided hardware. The use of real time application is known as real-time computing (RTC). Examples of RTAs include: • Videoconference applications • VoIP (voice over Internet Protocol) • Online gaming • Community storage solutions • Some e-commerce transactions • Chatting • IM (instant messaging Fig. 3. RIP implementation main topology 5 IMPLEMENTATION The research has been simulated in two phases/ scenarios. In the first scenario only one link (the link between node_0 and node_2) has been set to flap between the nodes. The failure and recovery utility is used from the OPNET modeler to do the implementation. Figure 4 shows the flapping link (Node_0 to Node_2) in OSPF topology. 20 A. Iqbal and S. L. Ali Khan / International Journal of Computer Networks and Communications Security, 3 (1), January 2015 and are shown in table 1. Table 2: Node_2 to Node_1 link failure and recovery Fig. 4. OSPF Single link flapping topology Table 1 show the flapping (failure and recovery) timings for the links between node 0 and node 2. Table 1: Node_0 to Node_2 link failure and recovery Link 2 (Node_2 to Node_1) Failure and Recovery timings Time Status 410 Seconds Failure 450 Seconds Recovery 490 Seconds Failure 610 Seconds Recovery 660 Seconds Failure 697 Seconds Recovery 820 Seconds Failure 6 RESULTS AND ANALYSIS Link 1 (Node 0 to Node 2) Failure and Recovery timings Time Status 240 Seconds Failure 400 Seconds Recovery 450 Seconds Failure 510 Seconds Recovery 620 Seconds Failure 630 Seconds Recovery 639 Seconds Failure 800 Seconds Recovery 850 Seconds Failure 945 Seconds Recovery For both scenarios the results have been categorized as follows: 6.1 One Link Flapping Network 6.1.1 Network Convergence time (in seconds) Figure 6 below shows the network convergence time for all the three routing protocols. From the figure we can observe that EIGRP takes the least amount of time for convergence, followed by RIP and then OSPF. For the second scenario, two links are set to flap between three nodes. The first link is node_0 to node_2 and the second link is node_2 to node_1. Figure 6: Network convergence for RIP, OSPF and EIGRP Fig. 5. OSPF multilink flapping between three nodes 6.1.2 Packet Drop (packets/ sec) Table 2 shows the failure and recovery timings for the second flapping link (Node_2 to Node_1). The failure and recovery timings for the first flapping link are kept the same as the first scenario In IP network the packet drop per second is shown in figure 7. The figure shows that OSPF has the most number of dropped packets as compared to RIP and EIGRP. 21 A. Iqbal and S. L. Ali Khan / International Journal of Computer Networks and Communications Security, 3 (1), January 2015 Fig. 7. IP network packets drop Figure 9: Voice packet end-to-end delay 6.1.3 Video Packet end-to-end delay 6.1.5 HTTP page response time EIGRP and RIP showed a better performance for the video conferencing packet end-to-end delay as compared to OSPF. This is shown in figure 8 below. EIGRP did not show an optimal performance for web browsing. For HTTP traffic the response time of EIGRP network trend to be higher as compared to OSPF and RIP. The HTTP page response time is showed in figure 10 below. Fig. 8. Video conferencing packet end-to-end delay 6.1.4 Voice packet end-to-end delay Fig. 10. HTTP page response time The graph in figure 9 shows a steady performance of EIGRP for voice traffic. In the OSPF network, for a single flapping link the performance initially was not optimal. However, once the network was converged, a significant improvement in the performance is observed. 6.1.6 Link Utilization In terms of link utilization, OSPF showed the best results. In OSPF network most of the links were utilized as compared to RIP and OSPF networks. This is showed in figure 11. 22 A. Iqbal and S. L. Ali Khan / International Journal of Computer Networks and Communications Security, 3 (1), January 2015 Fig. 11. Node_0 to Node 2 link utilization

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