(mpls) and traditional networks core protocols

1

Sudan Engineering Society Journal, September 2014, Volume 60; No.2

COMPARISON BETWEEN NGN CORE NETWORKS PROTOCOL (MPLS) AND

TRADITIONAL NETWORKS CORE PROTOCOLS (RIP & OSPF) USING OPNET

Amir Ahmed Omer Yousif, Sami M. Sharif and Hamid Abbas Ali Electrical and Electronic Engineering Department, Faculty of Engineering, University of Khartoum

E-mail: [email protected]

Received July 2014, accepted after revision Sep. 2014

مـســتخـلـص

انشبكاث انتى تقو ف links utilizationانتصالث إستغالنت أساط عهى يقاست دساست انسق ز تقذو

Open Shortest (OSPF) ، بشتكلRIP Routing information Protocol)) بتشغم بشتكل

Path First بشتكل ((MPLS Multi-Protocol Label Switching. نحظ ضعف إستغالنت قذ

نشبكت يحاكاة يفصهت تى اخشاء دساست. RIP OSPF استخذاو حانت ف links utilizationانتصالث

MPLS أظشث انذساست ا شبكت حثMPLS تقهم االصدحاو تدب يا ؤدي انى انشابط يعظى تستغم

.صفف طهباث انخذي

تى . تحهها انشبكاث نتصى خصصا انضي انحقق يصىبشايح يحاكاة ف OPNETبشايح انـ

تك نب اي شبكت ي عذد ي ب نب انشبكاث انقذ انحذث. ا نهقاست OPNET إستخذاو يحاك

(FTP) انهفاث قم تى استخذاو بشتكل. (IP and MPLS )( ف حانت كم ي (routersانخاث

انتحهه.ف زا انرج انصث

Abstract

This paper presents comparison study based on link utilization in the networks

running over Routing information Protocol (RIP), Open Shortest Path First (OSPF) and

Multi-Protocol Label Switching (MPLS). Poor link utilization in case of RIP and OSPF is

identified. A detailed simulation study is performed over MPLS network where we

have shown MPLS network has utilized most of links resulting in congestion

avoidance and low queuing delay.

OPNET is a real time simulator specifically designed for network design and analysis.

OPNET Simulator is used here to compare the networks cores. The core of a network

consists of a number of routers in each of the two cases (IP and MPLS). FTP and

VOICE traffic were used in this simulation model.

Keywords: MPLS, RIP, OSPF, Link Utilization, Traffic Engineering, OPNET.

1 INTRODUCTION

OPNET is a real time simulator specifically

designed for network design and analysis.

OPNET simulator is used here to compare

the networks cores. The core of a network

consists of a number of routers in each of

the two cases (IP and MPLS). Three types of

traffic: FTP, VOICE and VIDEO are used on

client sides with three corresponding

servers on the receiving end.

This paper presents a comparison study

between NGN networks core protocol

(MPLS) and traditional networks core

protocols (RIP & OSPF) using OPNET. It will

cover the fundamental concepts of all

important areas of NGNs, such as network

evolution, convergence, fixed-mobile

mailto:[email protected]

2 Sudan Engineering Society Journal, September 2014, Volume 60; No.2

COMPARISON BETWEEN NGN CORE NETWORKS PROTOCOL (MPLS) AND TRADITIONAL NETWORKS CORE PROTOCOLS (RIP & OSPF) USING OPNET

convergence, NGN definition,

characteristics, architecture, migration,

regulation, and standards, as well as case

studies and experimental works in NGN.

Figure 1: The reference NGN architecture

Figure 1 shows the reference architecture

that has been used in this paper.

2 Methodology and Approach

A simulation study is performed using

OPNET to get statistical results or data. The

results are analyzed to establish the

differences between core protocols. To

accomplish this task, a network model is

designed, being run and results are

collected to compare the performance of

voice and data over IP-based and traditional

networks.

Routing Information Protocol (RIP), Open

Short Path First (OSPF) and Multiprotocol

Label Switching (MPLS) are compared by

considering parameters like point-to-point

link utilization and transmission delay.

Classic IP Routing: In IP routing, source

node sends the packet to the intermediate

nodes, if any, and later to destination node

based on destination IP address of the

packet.

MPLS Operation: MPLS is a new technology

to forward the packets in IP unaware

networks. Entire MPLS network can be

divided into two parts namely MPLS edge

and MPLS core.

2.1 Simulation Methodology

Network is simulated using OPNET modeler

14.5. OPNET is extensive and powerful

simulation software with wide variety of

possibilities.

Figure 2: Network components and general

topology

The simulated network, as shown in Figure

2, consists of three areas namely Site1,

Internet Core, and Site2. There are four end

nodes out of which voiceUSER1 and

httpUSER are located at Site1 and SERVER

and voiceUSER2 are located at Site2. The

internet core consists of five routers:

LER_node_0, to LSR_node_4. These routers

are connected with point-to-point DS1

cables of data rate 1.54 Mbps. The end

nodes are connected to Internet Core with

point-to-point DS3 cables of data rate

44.736 Mbps. Simulation duration is set to

600 seconds. Figure 3 gives general

overview of the configurable parameters.


Amir Ahmed Omer Yousif, Sami M. Sharif and Hamid Abbas Ali

(a) (b) (c) (d)

Figure 3: Workstations and server model attributes (a) HttpUSER (b) VoiceUSER1 (c)

VoiceUSER2 (d) Server

- Links

Within the core, the links are represented by

bi-directional DS1 (1.544 Mbps) connectors.

At the edges the end-stations are attached

via DS3 (44.736 Mbps).

- Application configuration

In the initial configuration, only explicit

traffic is configured. Http and voice

applications are organized by means of

Application Configuration object found in

Figure 4.

Figure 4: Application configuration object

attributes

Http traffic pattern is selected as Heavy

Browsing, while voice corresponds to IP

Telephony and Silence Suppressed.

Heavy Browsing is carried out with constant

distributed time between page requests

(with mean value of 30 minutes).

IP Telephony and Silence Suppresser

employ G.729 (silence) encoder scheme.

- Profile configuration

The applications flows are assigned to

follow specific order during simulation

course. This is done by Profile Configuration

object presented in Figure 5.

There are two profiles configured i.e. http

and voice users and there is one adequate

application used per user’s profile. In order

to provide more steady results for traffic

generation, the applications start times are

set to constant 200 seconds for http and

250 seconds for voice.

Figure 5: Profile configuration object

attributes



Traffic is mapped to specific workstations

with Application’s Supported Profiles. There

is one httpUSER that employs User-http

profiles. The other clients i.e. voiceUSER1

and voiceUSER2 have User-voice configured

as in Figure 6.

Figure 6: Application support profile for

workstation

2.2 Traffic Simulation

We have simulated web browsing and voice

application traffic using application and

profile configuration utilities provided by

OPNET IT Guru. To make simulated network

much more real we have added extra

background traffic with the help of a

demand model. The demand model is

connected between two tiers indicating the

traffic intensity in terms of Traffic (bits/sec)

and Traffic (packets/sec) and is set to

500,000 bits/sec and 500 packets/sec

respectively for each of the demand. In

Figures 7, 8, the demand models have been

set between all the end nodes shown using

purple colored links. For example line three

is a bidirectional traffic flow link between

httpUSER and SERVER.

Figure 7: Demand model for background

traffic

Traffic flow configuration attributes are

presented in Figure 8.

Figure 8: Traffic flow configuration

attributes

2.3 Simulation Scenarios

Three separate scenarios are created one

for each of the RIP, OSPF, and MPLS

protocol.

2.3.1 RIP Scenario

RIP is type of distance vector routing

algorithm. Hop count is used as routing

metric in RIP and a routing path from source

to destination can contain a maximum of 15

hops. The restriction on the number of hops

poses difficulty in building bigger networks

using RIP. RIP suffers from count to infinity

problem. RIP chooses only a single shortest



path from source node to destination node

out of available shortest paths. This leads to

over utilization of chosen path and

underutilization of other paths. This is

illustrated by simulating the RIP network

using OPNET, as depicted in Figure 9.

Figure 9: RIP scenario

The RIP scenario involves the network

configured to work using RIP. Here all the

nodes and interfaces are configured to RIP.

RIP is configured with the default settings

that are not explained in details here. It

should be reminded that RIP uses hop-

count as the metric for destination

evaluation. RIP timers configuration can be

read from Figure 10.

It is obvious that RIP selection would not be

suitable for huge networks due to its 15-

hops count limit indicating infinity in routing

tables, which means no connectivity for

longer paths.

Figure 10: RIP configuration attributes (at

the router)

2.3.2 OSPF Scenario

OSPF is a type of interior gateway protocol.

OSPF creates network topology map using

link state information and it can detect link

failures and converge on an alternate

congestion free shortest path. OSPF on the

other hand, uses the available shortest

paths and distributes the load over two

chosen shortest paths, which leads to

efficient link utilization. This is illustrated by

simulating the OSPF network using OPNET

as shown in Figure 11.

Figure 11: OSPF scenario

This scenario is like RIP scenario (using the

same network), but here OSPF configured

on all interfaces and nodes. In the rest of

the simulation, <-> indicates a bidirectional

link between two nodes while -> and <-

represents unidirectional link.

OSPF has a hierarchical area structure and

does not have the hop limitation. There are

few key OSPF attributes explained below.

Other parameters description is skipped, as

they preserve their default configurations as

in Figure 12.



Figure 12: OSPF configuration attributes (at

the router)

2.3.3 MPLS Scenario

The third scenario involves, MPLS enabled

OSPF network which is simulated by

doubling the traffic i.e. Traffic (bits/sec) =

1,000,000 Mbps and Traffic (packets/sec) =

1000 (packets/sec) as shown in Figure 13. In

this network, label switched path is created

indicated by red thick line from node_0 to

node_1. Here, node_0 is the ingress router

and node_1 is the egress router.

Figure 13: Doubling the traffic

MPLS Traffic Engineering efficiently

distributes the incoming traffic over

shortest path as well as other unutilized

links also. This will ensure low queuing

delay and low packet loss which is very

essential for delay sensitive voice

applications.

Figure 14: MPLS network scenario

LSP

For label switch paths (LSPs), it is important

to know what configuration is required

within network environments to make them

get established properly. This is also the

case when considering dynamic LSPs.

Therefore, there are few remarks on

dynamic LSPs settings given with the

objective to present their TE potential as

depicted in Figure 15.

Figure 15: Label Switch Path (LSP)

configurations

2.4 Configuring Start Time for both (RIP &

OSPF)

A key parameter in routing protocol setup is

its Start Time. For both protocols it is set to



constant value of 10 seconds. Start Time

configuration remains important as RIP or

OSPF should begin its operation to build up

routing tables. The constant value is of

critical meaning for further network

configuration, as seen in Figure 16.

Figure 16: Configuring Start Time for both

(RIP & OSPF)

3 Simulation Results and Analysis

The simulation results are first obtained for

networks with RIP and OSPF routing

protocols. RIP, as mentioned earlier, is a

type of distance vector routing algorithm. A

routing path from source to destination can

contain a maximum of 15 hops. The

restriction on the number of hops posses a

difficulty in building bigger networks using

RIP. RIP suffers from count to infinity

problem. RIP chooses only a single shortest

path from source node to destination node

out of available shortest paths. This leads to

over utilization of a chosen path and

underutilization of other paths.

The result shows; network utilization which

is the ratio of current network traffic to the

maximum traffic that the port can handle,

network throughput which is the average

rate of successful message delivery over a

communication channel, and queuing

delay which is the time a job waits in a

queue until it can be executed.

3.1 Result of Scenario 1 (RIP)

The following figures show RIP scenario

result.

Figure 17: Link utilization in scenario1

Figure 18: Throughputs in scenario1

Figure 19: Queuing delays in scenario1

Figure 20: LER_node_0 <-> LSR_node_3

Utilization

http://en.wikipedia.org/wiki/Queue_(data_structure)




utilization


queuing delay

3.2 Results of Scenario 2 (OSPF)

The following figures show RIP scenario results

Figure 23: Link utilization in scenario 2

Figure 24: Throughput in scenario2

Figure 25: Queuing delay in scenario2

Figure 26: LSR_node_2 <-> LER_node_0

utilization


utilization


queuing delay




utilization in both RIP and OSPF

3.3 Result of Scenario 3 (MPLS)

After simulating the MPLS network for 600

second, it is found that the MPLS has

efficiently utilized links as shown in (Figures

17, 23, 30, 31 and 32).

Figure 30: Link utilization in scenario3


(packet/second)


(bit/second)

Figure 33: Queuing delay in scenario3


utilization of scenario3




utilization of scenario3

Figure 36: LSR_node_4 <-> LSR_node_3

queuing delay scenario3

3.4 Performance Comparison

Comparing results obtained from scenarios

for links utilization (Figures 17, 23, and 30),

throughput (Figures 18, 24, and 32) and

queuing delay (Figures 19, 25, and 33) the

following is concluded:

Utilization:

(a) (b) (c)

Figure 37: Link utilization comparison among (a) RIP (b) OSPF (c) MPLS

Figure 38: Link utilization comparison for

the scenarios

Throughput:

(a) (b) (c)

Figure 39: Throughput comparison among (a) RIP (b) OSPF (c) MPLS

Figure 40: Throughput performance

comparison for the scenarios



Queuing Delay:

(a) (b) (c)

Figure 41: Queuing delay comparison

among (a) RIP (b) OSPF (c) MPLS

Figure 42: Queuing delay comparison for

the considered scenarios

The efficiency of each of the routing

technologies being considered is

summarized in the Table 1.

Table 1: Link utilization summary of RIP, OSPF and MPLS networks

Routing

Technologies

Link

Utlized

Total

Link

%

Utilization

RIP 4 14 29%

OSPF 8 14 58%

MPLS 13 14 93%

After simulating the MPLS network for 600

seconds, it is found that the MPLS has

efficiently used many of the unutilized links

shown in Table 1.

MPLS Traffic Engineering configuration has

utilized 13 links out of 14 links in the core

network which approximately matches to

93% of the total link utilization. This result is

obtained by setting the Traffic intensity i.e.,

Traffic (bits/sec) to 1,000,000 and Traffic

(packets/sec) to 1000 in the traffic demand

between all the end nodes in the network.

From this table it can be seen that MPLS

with OSPF protocol configured on all the

nodes and interfaces, maximum link

utilization is guaranteed.

4 CONCLUSION

This paper concluded that poor link

utilization in both RIP and OSPF networks

exist. It is clear that networks configured

with RIP and OSPF routing techniques are

not capable of handling the incoming traffic

efficiently. When the network traffic

increases, shortest path from source node

to destination node is heavily congested

and this leads to loss of transmission data.

It is also shown that MPLS is capable of

handling incoming traffic efficiently by

distributing the traffic over unutilized links.

This will ensure that the packets entering

into MPLS core will reach the destination

with minimum queuing delay. MPLS-TE is

most suitable for huge traffic volume.

In the preformed simulations, we have

considered aggregate data consisting of

web browsing and voice traffic only. In

future work, along with the aggregate data,

video data should be used to analyze

performance of MPLS enabled OSPF

network.

So to enhance the performance of a

network it is highly recommended to have

an IP based network with an MPLS core

protocol, because IP network support all

kinds of technologies and it is easy to

maintain and use.



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(mpls) and traditional networks core protocols

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