performance analysis of mpls over voip

International Journal of Science, Engineering and Technology Research (IJSETR), Volume 4, Issue 6, June 2015

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ISSN: 2278 – 7798 All Rights Reserved © 2015 IJSETR

Performance Analysis of MPLS over VOIP

Jyoti Aggarwal

1 Akansha Dhall

2

M-Tech Student1, Assit. Prof. 2 & Department of ECE & Shri Ram College of Engg. & Mgmt

Palwal, Haryana, India

Abstract— The recent developments of IP networks are viewing

IP applications getting more complicated and requiring more

bandwidth consumption. More lately, IP networks are using

MPLS, a technique that can be utilized to enhance the IP

networks performance. By employing MPLS, data packets can

be propagated based on labels instead of destination address.

MPLS supports various features like QoS, traffic engineering

(TE) and VPNs (Virtual Private networks) etc. The primary

feature of MPLS is its Traffic Engineering (TE), which makes a

vital part for decreasing the congestion by effective management

and load balancing of the network resources. Because of less

network delay, effective forwarding mechanism, scalability,

improving the speed of packet transmission and determinable

performance of the services given by MPLS technology builds it

more suitable for carrying out real-time applications i.e. video

Conferencing and VoIP. This paper measured the performance

matrices i.e. delay, delay variation, throughput, page response

time and packet loss for various kinds of traffic (voice, data,

video) in their motion in a congested network for both

conventional IP network and MPLS-TE. For simulating the both

networks OPNET modeler is used. In this paper, the simulation

study is carried out to clarify the advantages of employing

MPLS-TE for multimedia applications

Keywords: MPLS, VoIP, TE, MPLS-TE, IP, OPNET.

I. INTRODUCTION

Recently the Internet provides us with real-time applications

which require to have the minimum possible end-to-end delay.

These applications involve voice and video conferencing.

Such applications are bandwidth requiring and mostly, a new more capacity connection is required for providing the needed

delays, somewhat that it is not cost efficient. Thus, a new way

is required in order to operate these applications and even

preserve the less end-to-end delay without spending more

money on enhancing the network. In interactive applications

of real time sound transmission, the whole one way delay

requires to be less in order to provide the user an impression

of real time reactions. A higher value in the order of 0.1 to 0.5

seconds is needed to achieve this goal. For video application,

a video stream should not greater than 250ms. The best

attempt protocols cannot assure such limits. MPLS has came out as the primary integration technology for transporting data,

voice and video traffic throughout the same network by

supplying TE (traffic engineering) and Quality of Service

(QoS). Recent works concentrates on comparison of network

traffic performance by simulation between both MPLS and

non-MPLS. In this paper, we design a network model by using

OPNET simulator for comparison of Video Conferencing and

VoIP traffic performance in addition to general data FTP(File

Transfer Protocol) on both MPLS and non-MPLS networks.

II. TRADITIONAL IP ROUTING

The main purpose of IP is to deliver the data from the source

node to destination node. Data is made as a series of packets.

All the packets are propagated via a chain of routers and

various networks to arrive at destination. When a packet

reaches at a router, the router has to look up its routing table to

determine the next hop for that packet on the basis of packets

destination address in the packets IP header as described in

Fig. 1. To construct routing tables every router operates IP

routing protocols i.e. Open Shortest Path First (OSPF), Border

Gateway Protocol (BGP) or Intermediate System-to-Intermediate System (IS-IS). When a packet passes over the

network, every router does the same steps for discovering the

next hop for the packet until it arrive at the destination [7][12].

To provide more interactive application flows with less delay

and packet drop thresholds, there is a clear requirement to

more effectively use the existing network resources. The

process by which it is obtained is called traffic engineering

and MPLS provides these features. [6].

Fig. 1 Traditional IP routing


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III. MPLS

MPLS (Multi-Protocol Label Switching) , is a packet

switching technology of layer 3 that transmits traffic

efficiently and supports Quality of Service (QoS) on the

Internet. It is required that MPLS enhance the routing

performance in the network layer. MPLS is utilized in Internet

Service Provider (ISP) networks and as a backbone to Internet

Protocol (IP) to give assured Quality of Service (QoS) and

effective bandwidth provisioning in the network [4][5][15]. MPLS provide support to various Layer 2 protocols i.e. Frame

relay, ATM and Ethernet. MPLS is capable to demonstrate

end to- end IP connections with several QoS characteristics

linked with the many transport media [16], its aim is to

provide the router a strong power of communication [4]. So it

bases particularly on a label (number) introduced between the

layer 2(data link layer) and the layer 3(network layer) in the

OSI model as depicted in Fig. 2; thus it is called layer 2.5

protocol [2] [4].

Applications

TCP

IP

MPLS

PPP

UDP

Physical ( Optical- Electrical)

FR ATM

Fig. 2 OSI reference model for MPLS

In a MPLS network, incoming packets are assigned a "label" by a “LER (label edge router)”. Packets are forwarded along a

"label switch path (LSP)" where each "LSR (label switch

router)" makes forwarding decisions.

A. MPLS Shim Header

Data packets when arrives at the LER, “Shim Header” is

located in between layer 2 and 3 of the OSI model. MPLS

Shim Header is integrated into four parts has a overall length

of 32 bits; 20 bits for Label, 3 bits for Experimental (EXP), 1

bit for Bottom of Stack and 8 bits for Time to Live (TTL)

which is depicted in Fig. 3.

Link Layer

Header

MPLS SHIM

Header

HH

Network (IP) Layer

Header

H

Header

IP Packet data

Label (20 bits) EXP

3

S (1 Bit) TTL (8 bit)

Fig. 3. MPLS Shim Header

The MPLS Shim Header contains an identifier is called

“Label”. It behaves as an identifier of Forwarding

Equivalence Class (FEC), and it is also used for finding the

Label Switched Path (LSP). Second field is Experimental field

(EXP) which is preserved for the experimental use or are

frequently used for providing QoS. Stack field (S) shows

whether the label is at the rear of Stack. If the Label is the last

entry in stack then the value is adjusted to one otherwise it is

zero. The last field is the (TTL) value which decreases by one

on each hop as it passes through the LSRs. When the TTL value arrives zero the packet is lost. Label plays a very

significant role among all the fields of MPLS shim header.

B. MPLS Elements

Label: It helps to discover the route that the packet must adopt in the MPLS network which allow the routers to

enhance the routing speed.

Label Switch Router (LSR): A router which is placed in the MPLS domain and routes the packets on the basis of label

switching is known as LSR. When LSR gets a packet it

examines the lookup table and finds the next hop, then before

sending the packet to next hop it attaches the new label to the

header and removes the old label.

Label Edge Router (LER): LER manages L3 lookups that is responsible for removing or adding the labels from the packets when they enter into or exit from the MPLS domain. When a

packet is entering or leaving the MPLS domain then it has to

pass over LER router

Label Distribution Protocol (LDP): This is the protocol by which the label mapping information is interchanged among

LSRs. It is responsible for demonstrating and preserving

labels among routers and switches.

Forward Equivalence Class (FEC): FEC is collection of packets where they have related features which are propagated

on the same path with the same priority.

Label Switched path (LSP): LSP is the path in MPLS domain which is set by signaling protocols. There are number

of LSPs in MPLS domain that are developed at ingress router

and passes over one or more core LSRs and ends at egress

router.

MPLS has two planes:

1. Control Plane: Control Plane is used for the label

distribution and routing information exchange among

adjacent devices.

2. Data Plane: Data Plane is used for propagating

packets on the basis of label or destination IP address

using LFIB controlled by the control plane.

IV. TRAFFIC ENGINEERING IN MPLS

NETWORKS The recently developed networks are converged networks;

they can transport normal data, voice, videos by utilization of

same network resources. Some user data traffics i.e. videos,

voice or SQL bank Transactions are more significant and less

liberal to delay so they are preferred and dealt on the basis of


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their delivery needs i.e. maximum affordable delay and

bandwidth. If the increased number of internet users and

various network data traffic types are considered, internet

service providers (ISP) dealt with a challenge in the form of

Traffic Engineering [20]. The condition of traffic engineering

by conventional IP networks is truly a challenging work. In

these kinds of networks, IP packets are routed by taken into

consideration the Open shortest path first (OSPF) protocol

which selects the shortest path from source node to destination

node. Though the choice of the shortest paths may preserve

network resources, still they may cause to many problems [11]. To manage the problem of packet drop and low delay in the

transfer of multimedia applications, it is essential to think of

enhancements methods to employ more efficiently on the

existing network resources. MPLS-TE is a process that gives

this functionality [9]. Though the original thought behind the

growth of MPLS was to make easier fast packet switching,

presently its primary objective is to support traffic engineering

and supply quality of service [14]. When the objective is to

obtain the performance aims i.e. traffic placement on

particular links and optimization of network resources, Traffic

engineering is primarily required. The abstract idea of traffic trunk has been demonstrated for implementing TE in a MPLS

area. A traffic trunk is described as a collection of traffic

flows placed within a LSP [21][22].

V. SIMULATION METHODOLOGY

OPNET Simulator 16.0 is used to create the configuration as

indicated in Fig.5 and Fig. 6 for both conventional and MPLS

networks. Two scenarios are consisted in the simulation by

considering the same network configuration. Scenario 1 is

based on IP network without TE and Scenario 2 is based on

MPLS network with TE. The results obtained by these simulations are utilized to compare the two networks.

Fig. 4 (Scenario 1)

Fig. 5 (Scenario 2)

The network contains several components: six LSRs (LSR_1,

LSR_2, LSR_3, LSR_4, LSR_5 and LSR_6), Two LERs

(Ingress LER1and Egress LER2), these routers are connected

by PPP adv link work at data rate of 4.5Mbps, Four clients

(client_1, client_2, client_3, client_4), two switches (SW1 and

SW2), and three servers (voice server, video server and FTP

server) are used. The simulation time for each scenario is 400 seconds. The traffic initiates at the 110th second and

terminates at the 400th second of the simulation time. One of

the primary elements of this simulation is that it considers

various network loads condition in the two scenarios.

VI SIMULATION AND RESULTS

We have compared performance matrices of IP model

networks and MPLS_TE. The compared parameters are Delay

Variation, End to-End Delay, FTP Response Time and Packet

Receive and Send. MPLS TE performs better than conventional IP network model for all the performance

parameters. The better performance of MPLS_TE is more

apparent, in the situation of heavy load (worst possible

network load). All routers are usual IP routers in scenario

1(Fig.4). MPLS definition attribute is not taken into

consideration and the packets are propagated by using OSPF

protocol, thus all packets are routed over the shortest path

only (LER1<->LSR_4<->LER2) and doesn't take into account

the other two paths. In Scenario2 (Fig. 5) MPLS_TE is carried

out by generating LSPs, and describing how traffic is allotted

to the corresponding LSPs. The network load is equally

disseminated among the three LSPs :(LER1<->LSR_1<->LSR_2< >LSR_3,LER1<->LSR_4<->LER2 and LER1<-

>LSR_5<->LSR_6<->LER2) this makes MPLS an effective

technology.


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Fig. 6 Video Packet Send and Received

Fig.6 and Fig.7 provides the mean number of packets sent

and obtained in both conventional IP networks and MPLS for

both video and voice traffic. Simulation result presents that

MPLS model provides more throughput as compared to the IP

model, and indicates that in the IP network Video and voice

packets start to loss sooner in comparison of MPLS network

In heavy load condition, Fig. 8 and Fig 9 shows the end to end

delay of video and voice traffics. It is clear that MPLS has

lesser delay as compared to the IP model in the situation of

heavy load (worst network load). In the situation of both

interactive voice the delay is less than 200 ms and in video the delay is less than 250ms. The delay or jitter variation is

approximately (30-50) ms. The delay variation of video and

voice traffics are shown in Fig.10 and Fig. 11. The delay

variation result presents that MPLS TE has lesser delay in

comparison of IP network model in the case of worst possible

load like the end to end delay results. By the simulation results

in Fig.12 we observe that Voice Packet Jitter enhanced in both

network model but in MPLS TE jitter is much lesser as

compared to IP network model. The FTP response time of

MPLS TE (Traffic Enigineering) was more lesser than IP

network model as in Fig. 13, also the mean of packet obtained in MPLS TE better than IP network model as shown in Fig. 14.

Fig. 7 Voice Packet Send and Received

Fig. 8 Video Packet End to End Delay

Fig. 9 Voice Packet End to End Delay

Fig. 10 Video Packet Delay Variation


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Fig. 11 Voice Packet Delay Variation

Fig. 12 Voice Packet Jitter

Fig. 13 FTP Download Response Time

Fig. 14 FTP Traffic Received

CONCLUSION

The primary aim of the paper is based on the performance

evaluation of MPLS TE and conventional IP network for Non

Real Time applications and multimedia applications (Video Conferencing, VoIP). After the simulation results it can be

concluded that MPLS TE gives best solution in carrying out

these applications in comparison of conventional IP networks.

Also this paper describes poor link usage in conventional IP

networks. It is found that network set up with OSPF routing

techniques are not able of managing the incoming traffic

effectively. With the increment in network traffic, shortest

path from source to destination is heavily congested and cause

to drop of transmission data. We have presented and simulated

the MPLS TE is able of managing incoming traffic effectively

by disseminating the traffic over many LSPs according to

FEC which is not capable to obtain in conventional routing protocol. By the results analysis, it is clear that with suitable

MPLS TE employed to the network, the performance of the

network is importantly enhanced. Thus, network providers

and Internet service providers appear to have been taking the

benefit of this technology to give flexible support for a broad

range of services i.e. construct reliable internet services,

simplify network architecture and overcome some available

infrastructure restrictions.

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performance analysis of mpls over voip

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