How to implement mpls

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Enhancing Quality of services of Multi-Protocol Label
Switching (MPLS) Networks and MPLS/Differentiated
Services Networks
A Dissertation Report Submitted in the Partial Fulfilment of
The Award of the Degree of
MASTER OF TECHNOLOGY
IN
COMPUTER SCIENCE AND ENGINEERING
Under Guidance of: Submitted By:
Ms. Renu Singla Divya Sharma
(Asst. Professor) Roll No:13M106
DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING

ABSTRACT
The introduction of Multi-Protocol Label Switching (MPLS) as a part of the Internet forwarding
architecture has immediate applications in traffic engineering (TE) and Quality of Service
(QoS).In this thesis, we evaluated the QoS performance measures such as delay variation, delay,
page response time, throughput, utilization, and packet drop for different types of traffics (data,
voice, and video) for both MPLS and MPLS/Differentiated Services platforms and then we
improve the QoS of MPLS networks and MPLS/Differentiated Services network.. The main
objective of this thesis is to improve the performance of MPLS and MPLS/Differentiated
Services networks using the well known network simulator ―OPNET Modeler‖. OPNET
Modeler, v14.5, provides a platform to replicate a real world network scenario using latest
simulation techniques, where different QoS parameters can be measured to compare networks
performance. Our approach in this thesis is that, we have designed and built a National Carrier
based core and edge network to simulate a real live scenario that spans the kingdom of Saudi
Arabia. Some of the results in the thesis are presented against simulation time and some against
network load. The results of comparing and evaluating these two core networks (MPLS and
MPLS/Differentiated Services) through well know QoS parameters show that complimenting
MPLS by Differentiated Services give better results than MPLS alone. We have also examined
different queuing polices of MPLS/Differentiated Services to have further understanding for this
type of network and find the best polices. We test also the failover mechanism for
MPLS/Differentiated Services, and see how the network recovers after fail through secondary
LSP.

Chapter 1
INTRODUCTION
1. Introduction:
MPLS is an elegant solution for the problems that are present in today networks, e.g. speed,
scalability, traffic engineering and quality of service (QoS) management. MPLS is also a
versatile solution to meet the requirements related to service requirements and bandwidth
management for the next generation IP based core networks [1]. MPLS is an emerging
technology which enhanced the capabilities of large scale IP networks and the routers forwarding
speed is also increased. Over the last few years the internet is used everywhere and is required a
variety of new applications that can fulfill the business and enterprise network requirements.
This variety of applications requires the guaranteed speed and bandwidth. The exponential
growth in users and volume of traffic is a great challenge to the existing internet infrastructure.
Despite these initial challenges and to meet the service and bandwidth requirements through the
next generation networks MPLS will have to play an important role in packet forwarding,
switching and routing.
2. Problem Statement:
In this thesis, we evaluated the QoS performance measures such as delay variation, delay, page
response time, throughput, utilization, and packet drop for different types of traffics (data, voice,
and video) for both MPLS and MPLS/Differentiated Services platforms and then we improve the
QoS of MPLS networks and MPLS/Differentiated Services network.. The main objective of this
thesis is to improve the performance of MPLS and MPLS/Differentiated Services networks using
the well known network simulator ―OPNET Modeler‖. OPNET Modeler, v14.5, provides a
platform to replicate a real world network scenario using latest simulation techniques, where
different QoS parameters can be measured to compare networks performance. Our approach in

this thesis is that, we have designed and built a National Carrier based core and edge network to
simulate a real live scenario that spans the kingdom of Saudi Arabia.
3. Motivation:
IP networks are increasingly carrying multimedia traffic along with Internet traffic as more and
more organizations are using IP networks for their businesses. Corporate World is increasingly
relying on IP network for their intra-network or inter-network needs. Many VPNs (Virtual
Private Networks) are deployed on an IP backbone, demanding end-to-end guaranteed service
from IP network. IP was designed to provide best-effort service for delivery of data packets and
to run across virtually any network transmission media and system platform. IP network is trying
to find solutions to adapt to this growing demand by providing different services like VoIP
(Voice over IP). Still IP network is not successful in providing ultimate quality of service, as it
has no means to handle traffic engineering very effectively. IP networks also lack the speed of
layer 2 switching [1]. The architectures that we will analyze are mainly the MPLS architecture as
implemented by Service Providers (SPs) and MPLs / DiffServ. We will primarily compare the
performance of the two networks, after successfully implementing the architectures in OPNET
(Optimized Network Engineering Tool) Modeler; by measuring some of the network
performance parameters, such as delay, delay Variation, etc. For this purpose, we will take
different kinds of traffic into account, such as normal data traffic or FTP, VoIP traffic and Video
streaming Traffic. Each traffic type is distinct in its behavior, and has its own constraints and
requirements. In this way, we will try to simulate a real world scenario as implemented by a
Service Provider for a customer on National Level in the Kingdom of Saudi Arabia, with a
Service Level Agreement contracted for a committed data connection. MPLS is a promising
solution to take over the next generation IP networks in terms of enhancing QoS. Additionally,
MPLS can be combined with DiffServ to provide QoS along with traffic engineering as both
have many things in common. In order to achieve our objective, our thesis requires the use of a
powerful Network Simulation Tool called OPNET Modeler v14.5.
4. DiffServ (Differential Services):

DiffServ emerged as simpler solution to provide QoS, as implementing IntServ and RSVP was
difficult. The main goal of DiffServ was to meet the performance requirements of the user.
Differentiated service mechanisms allow network providers to allocate different levels of service
to different users of the Internet. User needs to have Service Level Agreement (SLA) with
Internet Service Provider (ISP) to get DiffServ. The goal of the DiffServ framework is to provide
a means of offering a spectrum of services in the Internet without the need for per-flow state and
signaling in every router. By carefully aggregating a multitude of QoS-enabled flows into a small
number of aggregates that are given a small number of differentiated treatments within the
network. DiffServ eliminates the need to recognize and store information about each individual
flow in core routers. Each DiffServ flow is policed and marked at the first trusted downstream
router according to a contracted service profile, after which the flow is mingled with similar
DiffServ traffic into an aggregate. All subsequent forwarding and policing is performed on the
aggregates. The packets are marked by designating the ―Per-hop Behavior‖ (PHB) that packets
are to receive by setting a few bits in the Internet Protocol (IP) v4 header Type of Service (TOS)
octet as in figure (1.1) [25].
Figure 1.1 IPV4 Type of Service I
n this mapping, the first 6 bits, called the ―Differentiated Services Code Point” (DSCP) as
shown in figure (1.2) [25], define the PHB. The PHBs are expected to be simple and they define
forwarding behaviors that may suggest, but do not require, a particular implementation or
queuing discipline. In addition to DiffServ enabled packet forwarders, the network also requires
classifiers, polices, markers and a new kind of network component known as a bandwidth
broker. Per-flow policing and marking is performed by the first trusted edge router downstream
from the sending host.

Figure 1.2 Differentiated Services
When a local admissions control decision has been made by the sender's cloud, the edge router is
configured with the contracted per-flow service profile. Downstream from the first edge router,
all traffic is handled as aggregates. Network domains may need to shape traffic on egress to
prevent otherwise conforming traffic from being unfairly policed at the next downstream
domain. On domain ingress, incoming traffic is classified by the PHB bits into aggregates, which
are policed according to the aggregate profiles in place.
Depending on the particular DiffServ service model in question, out-of-profile packets are either
dropped at the edge or are remarked with a different PHB. Finally, to make appropriate internal
and external admissions control decisions and to configure leaf and edge device polices
correctly, each domain is outfitted with a bandwidth broker (BB). Currently, two PHBs have
been proposed by the IETF, namely Assured Forwarding (AF) , and Expedited Forwarding (EF) .
5. Multi-Protocol Label Switching (MPLS)
Multi-Protocol Label Switching (MPLS) [26] has evolved from the fast IP switching solutions
proposed in the mid-1990s by a plethora of companies such as Epsilon, Cisco and IBM. In
traditional network layer routing, as a router receives a packet it makes an independent
forwarding decision for that packet. Each router analyze the packet‘s header and performs a best
match routing table lookup to make an independent decision as to what the next hop for the
packet should be. MPLS emerged from the IETF‘s effort to standardize these proprietary

solutions, with the primary objective of integrating label switched forwarding with network layer
routing [27].
The objective of MPLS is to increase the efficiency of data throughput by optimizing packet
processing overhead in the IP networks. The MPLS technology uses a short fixed-length label to
route packets in the network. The edge routers in the network, called the Label Edge Routers
(LERs), attach this label to the packet. The core routers in the network, called the Label
Switching Routers (LSRs), then route the packet based on the assigned label rather than the
original packet header. The label assignments are based on the Forwarding Equivalence Class
(FEC) of the packet, where packets belonging to the same FEC are assigned the same label and
generally traverse through the same path across the MPLS network. An FEC may consist of
packets that have common ingress and egress nodes, or same service class and same
ingress/egress nodes, etc. A path traversed by packets in the same FEC is called a Label
Switched Path (LSP). The Label Distribution Protocol (LDP) and an extension to the Resource
Reservation Protocol (RSVP) are used to establish, maintain (refresh), and tear-down LSPs.
MPLS performs a much faster forwarding than IP since the packet headers do not need to be
analyzed at every hop in the path. MPLS also provides Traffic Engineering (TE) by allowing
traffic to be explicitly routed in the network to achieve efficient load balancing. The MPLS
architecture in a network node is shown in Figure 1.3 below [26].

Figure 1.3 MPLS Architecture
6. Simulation Tool used:
Network R&D is no longer a process that can be conceded to spreadsheets or traditional
software. In order for Network R&D organizations to innovate, they need robust network
simulation software to easily and intuitively model the intricate end-to-end behavior of protocols.
The solution must also be able to efficiently analyze the performance of these protocols and
technologies in network infrastructure models of realistic scale. OPNET (Optimized Network
Engineering Tool) provides a comprehensive development environment for the specification,

simulation and performance analysis of communication networks. OPNET provides four tools
called editors to develop a representation of a system being modeled. These editors, the Network,
Node, Process and Parameter Editors, are organized in a hierarchical fashion, which supports the
concept of model level reuse. For my thesis, OPNET proved to be an essential entity in modeling
my research and realizing the various variables of complex network architecture effectively and
efficiently.
6.1 OPNET MODELER:
OPNET Modeler uses modern simulation techniques to reduce research costs and ensure proper
insight of a theoretical network. OPNET Modeler‘s cutting-edge technology provides an
environment for designing protocols and technologies as well as testing and demonstrating
designs in realistic scenarios prior to production. OPNET Modeler is used by the world's largest
network equipment manufacturers to enhance the design of network devices, technologies such
as VoIP, TCP, OSPFv3, MPLS, IPv6, and much more. For our research work we have
implemented multiple design scenarios, using OPNET Modeler, in order to compare the results
at the time of execution. OPNET Modeler 14.5 is a significant software update to the OPNET
11.5 & 12 software releases that we started our thesis work with. The previous versions were
very limited in features and did not comply with the requirements of our thesis. The release 14.5
contains many new features and enhancements to existing capabilities. This release also
implements suggestions and fixes many software problems reported in earlier releases.

Figure 1.4 OPNET MODELER
7. MPLS / DiffServ:
The focus of our thesis is essentially based on the Service Provider‘s management of Quality of
Service in maintaining delay – sensitive applications such as Voice over IP or Live video
streaming over an IP Network. It is a fact that even with many Layer -2 and Layer -3 switching
facilities, Service Providers face network Transit delays and have to face a lot of problems in
providing Service Level committed bandwidths. Bandwidth availability is a necessary condition
for ensuring QoS and could also be a sufficient one for an SP network that would be strictly
oversized at any time, with respect to the offered traffic. Below could be some reasons to this
[25]:

 Links or nodes become unavailable during some time, either for planned maintenance, or
due to unexpected failures.
 Services are increasingly demanded from ISPs, with lower-priced rates, that are mostly
well above the committed rate and even up to the access port capacity, leading to
congested networks at peak times.
 There is a minimum time needed for planning and realizing the capacity upgrade of the
network.
The above scenario provides us with the conclusion that certain methods are definitely required
to ensure QoS to the customers in order to provide committed bandwidth rates throughout the
Service Level Agreement lifetime. Traditional Quality of Service (QoS) architectures are generic
and all encompassing and do not deal with the peculiarities of specific link-layer mechanisms.
These architectures do not take into account the differences in QoS requirements at the internet
service provider (ISP) level access networks and backbone networks. These differences in QoS
requirements arise due to differences in the volume of traffic handled at ISP and backbone
networks. Therefore, the generic QoS architectures were not able to handle the customized
requirements at the provider level.
These traditional generic QoS architectures are either very strict in their QoS enforcement, like
ATM-based architectures, or lenient in their enforcement, like DiffServ-based architectures.
Both of these architectures present problems as strict enforcement leads to poor scalability, due
to high state information storage requirements. Lenient enforcement allows ill-behaved flows to
enter the core of the network and cause network resource over-utilization and loss of revenue
among other such issues related to ISPs [25]. To achieve optimal QoS based on individual traffic
types, it is required that the system is;
 Scalable
 Have control on resource utilization
To achieve above characteristics in QoS architectures, we are going to look at the details of two
technologies that exist on their own and we suggest combining them to provide the flexibility

elements that can be used to customize the architecture for a particular domain. These
architectures are:
 MPLS (Multi Protocol Label Switching)
 DiffServ (Differential Services)
We will now look at these technologies a bit closely to see their functionality.

Chapter 2
LITERATURE REVIEW
2. Related Work:
This chapter provides the references that were used as a background study for this thesis. The
initial research using these references was conducting to understand the basic underlying
concepts in each of the MPLS and DiffServ technologies and their practical applications in the
real world. We were also looking for similar or related work to compare our results with. 1.
Reference [11] deals with adaptive sampling for network performance measurement under voice
traffic. It addresses the issue of how to carry out the sampling in an adaptive fashion, so that the
accuracy for measuring the quality of service parameters (delay, loss, Delay Variation,
throughput) is better if we know something about the traffic type and traffic parameters. Two
realistic network topologies based on MPLS networks are setup to evaluate the proposed
adaptive sampling scheme for monitoring and measuring network performance metrics.
2. Reference [12] discusses the enhancement of the MPLS QoS routing by adding QoS
protection. In this paper, a method for enhancing current QoS routing methods by means of QoS
protection is presented. QoS protection is defined as a function of QoS parameters, such as
packet loss, restoration time, and resource optimization. In an MPLS network, the segments
(links) to be protected are predefined and an LSP request involves, apart from establishing a
working path, creating a specific type of backup path (local, reverse or global). The final result is
a transparent and flexible method that addresses this lack of QoS protection. A Backup Decision
Module (BDM) is introduced in the framework as the crucial element. An analysis of different
cases shows that the BDM can select the most suitable backup method for each LSP request, thus
avoiding expensive evaluations.

3. Reference [13] implements an MPLS network simulator which supports Label Distribution
Protocol (LDP) and constraint-based LDP (CR-LDP). In order to show MPLS simulator's
capability, the basic MPLS function defined in MPLS standards is simulated; label distribution
schemes, flow aggregation, ER-LSP, and LSP Tunnel. This paper describes design,
implementation, and capability of an MPLS simulator. The proposed MPLS simulator helps
researchers to simulate and evaluate their MPLS related techniques. For example, the MPLS
simulator may be easily applied to the area of traffic engineering by using its function such as the
establishment of ER-LSP and LSP Tunnel verified this paper. The simulator proposed in this
paper is still in premature stage; that means, there still remain a lot more capabilities to be added
and extended such as RSVP extension for MPLS and QoS support on each MPLS node and so
on.
4. Reference [14] implements the designing of a new routing simulator for DiffServ MPLS
networks. The paper present the design and implementation of a new routing simulator called
Extended QoS-based Routing Simulator (EQRS). The objective in this version is to provide new
capabilities that enable simulating DiffServ MPLS networks. EQRS allows users to configure
parameters of DiffServ MPLS networks, where the dynamics of constraint based routing
algorithms as well as traffic engineering mechanisms can be investigated. The simulation results
prove that: 1) QoS routing achieves better network performance under careful configuration. 2)
The simulator is suitable for modeling, designing and evaluating DiffServ MPLS networks.
Constraint based routing plays an important role in DiffServ MPLS networks for supporting real
time traffic transmission. The result proves that QoS routing algorithms achieves better
performance than shortest path algorithms and also EQRS is flexible and suitable for modeling,
designing and evaluating DiffServ MPLS networks.
5. Reference [15] introduces the concepts and simulation of DiffServ and MPLS. DiffServ is
scalable for deployment in today‘s Internet, and MPLS provides fast packet switching and the
opportunity for traffic engineering. Thus, the combination of DiffServ and MPLS presents a very
attractive strategy to backbone network providers. This paper attempts to explain the concepts of
DiffServ + MPLS and illustrate its effectiveness by performing a simulation using Network

Simulator NS-2. MPLS-based traffic engineering is another important advantage to DiffServ.
The paper focuses on how MPLS and DiffServ coordinate well with each other due to some
synergies between them. Both push the complexity of the network to the edge. Therefore MPLS
and DiffServ edge routers perform a similar set of functions that can be combined when both are
implemented in a network. MPLS and DiffServ are complementary solutions for the problem of
providing different service levels in a single network. DiffServ defines different behaviors in the
nodes while MPLS deals with the paths between different nodes. There is some scalability
problems derived from the use of different labels associated to different QoS for the same path.
They can be minimized without allocating all the possible labels at the same time. Different
methods are available but the philosophy of all of them is not to allocate resources when no
traffic is going to use them. There are two main protocols that can be used for exchanging MPLS
labels with different service levels: RSVP with extensions and CR-LDP. Both RSVP and CR-
LDP provide capability to control the nodes that the LSP passes. Both protocols are suitable for
label exchange and distribution in DiffServ MPLS domains but RSVP can be more easily
employed if the network is already using it for resource reservation. The paper gave general
conclusions and did not give any numbers to compare with.
6. Reference [16] implements a discrete event simulation of the DiffServ-over-MPLS with NIST
GMPLS Light wave Agile Switching Simulator (GLASS). The paper, explains the discrete event
network simulation for DiffServ-aware-MPLS on the GMPLS-based WDM Optical Network.
The GLASS has been developed to support the R&D works in the area of Next Generation
Internet (NGI) networking with GMPLS-based WDM optical network, and Internet traffic
engineering with DiffServ-over-MPLS. The paper, focused on the functions of NIST GLASS for
DiffServ-over-MPLS, and analyzed the experimental simulation results of the DiffServ-over-
MPLS packet processing. The paper gave general conclusions and did not give any numbers to
compare with.
7. Reference [17] evaluates MPLS performance in backbone network. This paper introduces a
new method to describe the lookup process of IP and MPLS in backbone network. Relative
MPLS performance compared to IP is evaluated. This paper introduces a method based on DP-

Tri algorithm to measure the lookup time in IP and MPLS. Using this method, the average packet
delay in IP and MPLS can be solved.
8. Reference [18] proposes MPLS performance modeling using traffic engineering to improve
QoS routing on IP networks. MPLS supports throughput and delay sensitive real-time media
services such as Internet-Based Distance Learning or I-DL. Future networks require high QoS
guarantees. The Multi-Service Core Network tries to achieve adequate QoS provisioning by
adopting an application-based MPLS network. 9. Reference [19] describes MPLS-BGP based
LSP setup techniques. The application of the route reflector in the network reduces the
convergence time.
10. Reference [20] introduces MPLS DiffServ-aware traffic engineering. MPLS traffic
engineering (TE) enables resource reservation, fault-tolerance, and optimization of transmission
resources. MPLS DiffServ-TE combines the advantages of both DiffServ and TE. The QoS
delivered by MPLS DiffServ-TE allows network operators to provide services that require strict
performance guarantees, such as voice, and to consolidate IP and ATM/FR networks into a
common core.
11. Reference [21] describes packet loss probability for DiffServ over IP and MPLS reliable
homogeneous multicast networks. The paper present a new fair share policy (FSP) that utilizes
Differentiated Services to solve the problems of QoS and congestion control when reliable
Automatic Repeat Request (ARQ) multicast is used. The results should provide insight into the
comparisons of the residual packet loss probability between IP multicast in MPLS networks
using FSP and plain IP multicasting using the same policy when DiffServ are adopted and when
reliable ARQ multicast is considered.
12. Reference [22] describes residual multicast loss for ARQ/DiffServ over IP and MPLS
homogeneous networks. In order to provide QoS in group communications for real time
applications such as video conferencing, reliable multicasting is used. Miscellaneous efforts have
been undertaken to provide reliability on top of IP multicast. Two error control strategies have

been popular in practice. These are the FEC (Forward Error Correction) strategy, which uses
error correction alone, and the ARQ (Automatic Repeat Request) strategy, which uses error
detection, combined with retransmission of data. The paper present a new fair share policy (FSP)
that utilizes Differentiated Services to solve the problems of QoS and congestion control when
reliable ARQ multicast is used. The results should provide insight into the comparisons of the
residual packet loss probability between IP multicast in MPLS networks using FSP and plain IP
multicasting using the same policy when DiffServ are adopted and when reliable ARQ multicast
is considered.
The above mentioned few references along with other reference (mentioned at the end of the
thesis), formed the basis for this thesis. Many of these references provide theoretical and
practical applications of next generation networks and provide different ways of implementing
QoS for different type of traffics. For our thesis, we have considered the above works to explain
how MPLS / DiffServ, while working together, provide higher efficiency levels for different
class of traffics.
2.1Multiprotocol Label Switching
2.1.1 Introduction
Multiprotocol Label Switching (MPLS) is growing in popularity as a set of protocols for
provisioning and managing core networks. The networks may be data-centric like those of ISPs,
voice-centric like those of traditional telecommunications companies, or one of the modern
networks that combine voice and data. These networks are converging on a model that uses the
IP to transport data. MPLS overlays an IP network to allow resources to be reserved and routes
predetermined. Effectively, MPLS superimposes a connection-oriented framework over the
connectionless IP network. It provides virtual links or tunnels through the network to connect
nodes that lie at the edge of the network. A well-established requirement in telephone networks
is that the network should display very high levels of reliability and availability. Subscribers
should not have their calls dropped, and should always have access to their service. Downtime
must consequently be kept to a minimum, and backup resources must be provided to take over
when any component (link, switch, switch sub-component) fails. Operations, Administration and
Maintenance (OAM) are the generic term concerning issues like these. The data world is

increasingly demanding similar levels of service to those common in the arena of telephony.
Individual customers expect to be able to obtain service at all times and expect reasonable levels
of bandwidth. Corporate customers expect the same services, but may also have data streams that
are sensitive to delays and disruption.
As voice and data networks merge they inherit the service requirements of their composite
functions. Thus, modern integrated networks need to be provisioned using protocols, software
and hardware that can guarantee high levels of availability. High Availability (HA) is typically
claimed by equipment vendors when their hardware achieves availability levels of at least
99.999% (five 9s). This may be achieved by provisioning backup copies of hardware and
software. When a primary copy fails, processing is switched to the backup. This process, called
failover, should result in minimal disruption to the data plane. Network providers can supply the
required levels of service to their customers by building their network from equipment that
provides High Availability. This, on its own, is not enough, since network links are also prone to
failure, and entire switches may fail. The network provider must also provide backup routes
through the network so that data can travel between customer sites even if there is a failure at
some point in the network. [30] This chapter describes the basic terminology, and signaling
characteristics of MPLS. MPLS is an emerging IETF standard that integrates link layer media,
such as ATM, for label-switching along with IP routing, as shown in figure 2.1, in order to
provide efficient routing and switching of IP traffic through the network. [31]
MPLS is a standards-approved technology for speeding up network traffic flow and making it
easier to manage. MPLS involves setting up a specific path for a given sequence of packets,
identified by a label put in each packet, thus saving the time needed for a router to look up the
address to the next node to forward the packet to. MPLS is called multiprotocol because it works
with IP, ATM, and FR network protocols. With reference to the standard model for a network,
the OSI model (see figure 13), MPLS allows most packets to be forwarded at layer 2 (switching)
level rather than at layer 3 (routing) level. In addition to moving traffic faster overall, MPLS
makes it easy to manage a network for QoS. For these reasons, the technique is expected to be
readily adopted as networks begin to carry more and different mixtures of traffic. [32] MPLS is a

key development in Internet technologies that will assist in adding a number of essential
capabilities to today's best effort IP networks, including: Layer 2 (Ethernet, ATM, FR) VPNs. It
is a technology to meet the service requirements and bandwidth management of IP-based
backbone networks. This chapter includes a description of MPLS trends, fundamental MPLS
technology.
Figure 2.1: Label Switching along with IP routing.
IP flows are switched via a MPLS tunnel, called Label Switched Path (LSP). Labels are
distributed using various protocols like Label Distribution Protocol (LDP), Resource Reservation
Protocol-Traffic Engineering (RSVP-TE), and Constraint Based Routed LDP (CR-LDP). The
labels are of fixed-length, which enables high-speed switching of packets between links. Some
major concepts in MPLS: [31]
 Label Edge Routers (LER): maps IP to/from MPLS label packets; pushed and
pops labels.
 Label Switching Routers (LSR): swaps MPLS labelled packets.
 Forward Equivalence Class (FEC): policy (e.g. IP address prefix, Autonomous
System) which determines which IP packets enter a LSP.
 Label Switched Path (LSP): logical connection, typically multi-point to point (if
LDP signalled) or point to point, that forwards MPLS labelled packets.

 Label Distribution Protocol (LDP): One of three protocols that establish labels
used to carry MPLS traffic.
2.1.2 Why MPLS?
MPLS addresses network backbone requirements effectively by enhancing networking IP QoS in
the core network. MPLS offers the following capabilities in the network:
 Interoperability: MPLS provides a bridge between access IP and core ATM.
 Scalability: MPLS can be used to avoid some problems associated with IP over
ATM/FR overlay.
 IP QoS: MPLS uses end-to-end traffic engineering throughout the Core network to
ensure guaranteed QoS.
2.1.3 LERs and LSRs:
The devices that participate in the MPLS protocol mechanisms are classified into:
1. Label Edge Routers (LERs).
2. Label Switching Routers (LSRs)
 Label Edge Routers: A Label Edge Router (LER) is a device that operates at the
edge of the MPLS network. It forwards traffic from various dissimilar transport networks
(ATM, Frame Relay, Ethernet), at the ingress, on to the MPLS network after establishing
LSPs, using the label signalling protocol, and distributes the traffic back to the access
network at the egress. LERs assign and remove labels as traffic flows in and out of the
MPLS network. LERs push and pop labels, LSRs swap labels.
 Label Switching Routers: A Label Switching Router (LSR) is a router device in the
core of a MPLS network that participates in the establishment of LSPs using the
appropriate label signalling protocol and then switches data traffic based on the
established paths. LSRs swap labels while LERs pop/push labels at the edge.

2.1.4 Forward Equivalence Class:
The Forward Equivalence Class (FEC) is an important concept in MPLS. A FEC is any subset of
packets that have the same requirements for their transport. They can be forwarded out the same
interface with the same next hop and label, given the same class of service, outputted on same
queue, given same drop preference, or any other option available to the network operator, as
shown in figure 2.2. When a packet enters the MPLS network, it is mapped into a FEC by the
LER. In the current LDP specification, only three types of FECs are specified: IP address prefix
(source and/or destination prefix). Router ID. Flow (port, destination-address, source-address,
etc.). The specification states that new elements can be added as required.
Figure 2.2: FEC mapping example.
.
2.1.5 Label-Switched Paths
LSPs are a sequence of labels at each and every node along the path from the source to the
destination. LSPs can be either control-driven or topology driven.
2.2 MPLS Background:
MPLS was originally proposed by a group of engineers from Ipsilon Networks. Cisco Systems,
introduced a related proposal, not restricted to ATM transmission, called "Tag Switching". It was
a Cisco proprietary proposal, and was renamed "Label Switching". It was handed over to the
IETF for open standardization. The IETF work involved proposals from other vendors, and
development of a consensus protocol that combined features from several vendors work. The

motivation was to allow the creation of simple high-speed switches, since for a significant length
of time it was impossible to forward IP packets entirely in hardware. Therefore, the advantages
of MPLS primarily revolve around the ability to support multiple service models and perform
traffic management.
MPLS is a highly scalable and data-carrying mechanism and it belongs to packet switched
networks. In this kind of network, data packets are assigned labels. Packet forwarding decisions
are made solely on the contents of this label, without the need to examine the packet itself. This
allows one to create circuits across any type of transport medium, using any protocol. The
benefit was to eliminate dependence on a particular Data Link Layer technology, like Ethernet
and eliminate the need for multiple Layer 2 networks to satisfy different types of traffic.
MPLS operates between Layer 2 - Data Link Layer and Layer 3 – Network layer of OSI network
model. It was designed to provide a data carrying service for both circuit and packet switched
based clients. It can be used to carry many different kinds of traffic, such as IP packets, Ethernet
and ATM frames. However, MPLS provides the same goals like the previous technologies such
as ATM and frame relay but was equipped with some enforcements to face the strengths and
weaknesses of ATM mechanism.
MPLS has replaced almost all these technologies in the marketplace [8]. As the packets travel
from one router to another, each of these routers make an independent forwarding decision. Each
router runs a routing algorithm and does analysis of each packet header to examine where to send
it after. For this reason, each router chooses a next hop for each packet based on packet header
analysis [9]. A router forwards an IP packet according to its prefix. In a given router, the set of
all addresses that have the same prefix, is referred to as the Forwarding Equivalent Class (FEC)
and packets that belong to the same FEC, have the same output interface. On the other side, in
MPLS technology, each FEC is associated with a different label. This label is a short fixed length
identifier and has always local significance. MPLS label is useful for the identification of the
output interface of an IP packet without having to look up its IP address every time in the
forwarding table. This label has the same functionalities to Virtual Path Identifier/Virtual Circuit
Identifier (VPI/VCI) value associated with an Asynchronous Transfer Mode (ATM) cell [20].

MPLS has many benefits which are higher reliability, integration, better efficiency, better way to
support multicast and (RSVP), direct classes of service implementation, traffic engineering
capabilities, more robust - reduces load on network cores and finally Virtual Private Network
(VPN) scalability and manageability [20]. As it concerns the integration, MPLS integrates IP and
ATM functionality rather than overlaying IP on ATM. For this reason, the ATM infrastructure is
made visible to IP routing and there is not any need for mapping between IP and ATM features.
The result is that MPLS does not need ATM addressing and routing techniques. Better
efficiency, means when all the Permanent Virtual Circuits (PVCs) are seen by IP routing as a
single hop paths with the same cost. Another benefit of MPLS is the higher reliability that was
mentioned above. MPLS is an easy solution for integrating routed protocols with ATM.
Traditional IP over ATM involves setting up a mesh of Permanent Virtual Circuits (PVCs)
between routers around the ATM cloud. With this approach, there are number of problems. The
most serious problem is that a single ATM link failure could make several router to router links
fail, creating problems with large amounts of routing update and subsequent processing. Direct
classes of service implementation is another MPLS benefit. In this situation, MPLS makes use of
the ATM queuing and buffering capabilities to provide different Classes of Service (CoS). This
allows direct support of IP precedence and CoS on ATM switches without complex translations
to the ATM. On the other hand, MPLS provides VPN scalability and manageability. This means
that MPLS can make IP VPN services more scalable and more easy to manage. With an MPLS
backbone, VPN information can be processed only at the ingress and egress nodes, with MPLS
labels carrying packets across a shared backbone to their correct exit point. Moreover, MPLS
benefits include Traffic Engineering (TE) capabilities needed for the efficient use of network
resources. TE is possible to shift the traffic load from over utilized portions to underutilized
portions of the network, according to traffic type, traffic load and traffic destination. Last but not
least benefit that the MPLS provides, is the load reduction on core network. MPLS allows access
to the internet routing table only at the ingress and exit points of a service provider network. The
transit traffic entering at the edge of the providers autonomous system can be given labels that
are associated with specific exit points. The result is that the internal transit routers and switches
need only process the connectivity with the providers edge routers [20].

An MPLS network consists of MPLS nodes, Label Switching Routers (LSRs) and Label
Switching Paths (LSPs). MPLS node is also an LSR but it does not have necessarily the
capability to forward IP packets based on prefixes. As it concerns LSR, is an IP router that is
capable to run the MPLS protocol. Its LSR is responsible to bind labels to FECs, forward IP
packets based on their labels and carry the forwarding decision by carrying out a table look up in
the forwarding table using a prefix [10]. Below, in figure 2.3 we can distinguish that there are
two MPLS administrative domains and one domain that does not support the MPLS protocol. IP
packets, are switched using their MPLS label inside the MPLS domain.
Figure 2.3 MPLS domains, nodes and LSRs [10].
An MPLS domain can be connected to a node outside the domain, which might belong to an
MPLS or a non-MPLS IP domain. In figure above, the MPLS domain B consists of five routers,
two of which are LSRs (LSR 1 and LSR 2). The remaining three routers can be either LSRs or
MPLS nodes. For more simplicity, we can assume that all nodes within an MPLS domain are
LSRs [10]. MPLS domain B is connected to the MPLS domain A via LSR 1, and is connected to
the non-MPLS IP domain via LSR 2. LSRs 1 and 2 are referred to as MPLS edge nodes.
MPLS networks have three main applications. It is possible two or three of these capabilities
would be used simultaneously [20].
 IP Virtual Private Network (VPN) Services: A VPN service is offered by a
provider to many corporate customers and is the infrastructure of a managed Intranet and
Extranet service. The MPLS technology in combination with the Boarder Gateway
Protocol (BGP), allows one network provider to support thousands of customerʼs VPNs.

This combination offers a very scalable, flexible and manageable way of providing VPN
services on both ATM and packet-based equipment.
 IP and ATM Integration: MPLS integrates IP services directly on ATM switches.
the IP routing and Label Distribution Protocol (LDP) software resides directly on ATM
switches. For this reason MPLS allows ATM switches to optimally support IP multicast,
Virtual Private Network (VPN), IP class of service and Resource Reservation Protocol
(RSVP). This integration of IP and ATM means that the MPLS is less complex and more
scalable.
 IP Explicit Routing and Traffic Engineering (TE): IP networks have lack of
ability to finely adjust IP traffic flows to make best use of available network bandwidth.
Another problem is the lack to send selected flows down selected paths. Label Switched
Paths (LSPs) are used by MPLS and can be used on both ATM and packet-based
equipment. IP Traffic Engineering capability of MPLS uses special LSPs to finely adjust
IP traffic flows.
2.3 MPLS Applications
There are many applications for MPLS in the Internet, for example, Traffic Engineering, QoS
Routing, Tunnelling and Flow Merging. These are described below.
2.3.1 Traffic Engineering
Traffic engineering allows that traffic flows are moved away from the shortest route and onto
potentially less congested physical paths across the network. This can be implemented to force a
packet to follow an explicitly chosen route from the source to the destination. AB Shortest Path
Label Switched Path Label Switching From A to B From A to B Router Traffic engineering is
currently the primary application for MPLS. A successful traffic engineering solution can
balance a network‘s aggregate traffic load on the various links, routes, and switches in the
network so that none of its individual components is over utilized or under utilized. This results
in a network that is more efficiently operated and provides more predictable service.

2.3.2 QoS Routing
Another application of MPLS is Quality of Service (QoS) routing. QoS routing refers to a
method in which the route allocated to a particular traffic flow is chosen in response to the QoS
required for that traffic flow. An MPLS network can set up multiple label switching paths
between each pair of edge label switching routers. Each label switched path can be traffic
engineered to provide different performance and bandwidth guarantees. An ingress router could
place high-priority traffic in one label switched path, medium-priority traffic in another label
switched path, best-effort traffic in a third label switched path, and less-than-best-effort traffic in
a fourth label switched path. In this way, MPLS offers the network operator great flexibility in
the different type of services that it can provide its users.
2.3.3 MPLS Tunnelling
When a packet enters the MPLS network, a label is inserted in the front of the packet‘s IP
header, thus the packet is encapsulated within the MPLS network. MPLS creates a label switched
path through the network for the labelled packet, then the packet switching follows this label
switched path instead of routing the packet based on the destination address in the IP header.
Hence MPLS effectively creates tunnels through the network. This tunnel has a well-defined
entrance, a well-defined exit, and a gate (forwarding equivalence class mapping) to control what
is allowed into the tunnel. Packets entering the tunnel must pass the gating criteria. Once in the
tunnel, there are no branch exits since the packet is not routed at intermediate nodes. Since only
the network operator can create label switched paths, malicious users cannot create additional
tunnel entrances or disrupt the network.
The overheads caused by the MPLS tunnelling depend on the depth of the label stack. In the case
of a flat label stack, there is only one label stack entry and the overhead resulting from the
tunnelling encapsulation is only four bytes.
2.3.4 Flow Merging
MPLS allows the mapping from IP packet to forwarding equivalence class to be performed only
once at the ingress to the MPLS domain. A forwarding equivalence class is a set of packets that

can be handled equivalently for the purpose of forwarding and thus is suitable for binding to a
single label. From a forwarding point of view, packets within the same subset are treated by the
label switching router in the same way, even if the packets differ from each other with respect to
the information in the IP header. The mapping between the information carried in the IP header
of the packets and the forwarding equivalence class is many to one. That is, packets with
different contents of their IP header could be mapped into the same forwarding equivalence
class. For example, a set of packets whose IP destination addresses matches a particular IP
address prefix can be mapped into a particular forwarding equivalence class, therefore the
packets are labeled with the same label and follow the same label switched path in the MPLS
domain. Merged packets which have the same label are indistinguishable in the subsequent label
switching routers, except at the egress router where the label is removed and the packets are
forwarded by conventional forwarding.
2.4 Voice over MPLS
There is more than one way to use MPLS to implement voice traffic: An individual path can be
set up for each voice call, signalling the LSP at the same time as the call is signalled, for
instance. More often, system operators will find it better to create a smaller number of larger-
bandwidth pipes in advance, down which multiple calls can be tunnelled. In this case, fewer
LSPs have to be managed and generally there is no extra signalling delay to establish the LSP in
real time. But the routing of the call must take into account the selection of existing LSPs (and in
some cases may need to signal a new LSP). Several methods have been proposed for
accomplishing that task, including treating LSPs as if they were physical trunks and using a
combination of SIP and Megaco to distribute information about the LSPs. Whichever approach is
used, MPLS can provide the QoS guarantees required to transport voice, and running MPLS on
top of IP or ATM is a very effective way of doing it.
2.5 Efficiency Considerations:
When sending voice data over IP (or over MPLS, which in turn is running over IP), the RTP is
used, running over the UDP. This protocol, along with the RTCP, provides timing information in
voice packets to ensure that smooth voice reproduction can be achieved at the receiving end. The

RTP, UDP, and IP headers included in data transfer can be a significant overhead compared with
the size of the voice data. A voice packet may contain only 12 to 20 bytes of data; whereas the
UDP has a 8-byte header, the RTP header is 12 bytes long, an IP header is 24 bytes, and a MPLS
header (if MPLS is used) requires a further 4 bytes-for a total of 52 bytes of overhead on a single
voice packet. The IP header is needed for routing a sample through the IP network when running
directly over IP, but when using a MPLS LSP, no IP routing is required; hence, it should be
possible to remove the IP header and save 24 bytes. This is one of the issues that motivated the
formation of the VoMPLS Discussion Group, which in addition to considering how MPLS can
help deliver voice traffic over IP networks, also provides input to the IETF. Many issues must be
resolved: One of the key ones being that stripping and replacing the IP header at either end of the
LSP adds a performance overhead. Also, if a LSP is used for multiple voice channels, a
multiplexing mechanism is necessary. The mechanism could use the ports in the UDP header,
but it may require a (small) header specifically for that purpose.
2.6 Benefits and Advantages of MPLS
One of the major advantages of MPLS is the fact that it will be a standards-based implementation
of label switching technology. The development of standards results in an open environment
with multiple manufacturers‘ products all being interoperable. Competition also results in lower
prices, leads to more innovative features and stimulates early availability.
1) Explicit Routes
A key feature of MPLS is its support for explicit routes. Explicitly routed LSPs are far more
efficient than the source route option in IP. They also provide some of the functionality needed
for TE. Explicitly routed paths also have attractions as ‗opaque tunnels‘ where they can carry any
type of traffic that the two co-operating tunnel end points agree on. Because the intermediate
LSRs that ‗carry‘ the tunnel see only the MPLS labels arbitrary traffic can be carried in packets
sent on the tunnel.
2) Virtual Private Networks

Many organizations use private networks built using leased lines to connect multiple sites. A
carrier offering that emulates the secure, reliable, and predictable behavior of these networks
over shared carrier facilities holds the promise of providing extra service revenues to the carrier,
while also lowering the cost of ownership borne by the customer. VPNs are an emulation of
these Private Networks across carrier facilities in such a manner that each customer perceives hi
myself to be running on a Private Network. The carrier‘s infrastructure has been ‗Virtualized‘ to
support many independent mutually invisible networks. MPLS is a key ingredient in building
such networks; the MPLS labels can be used to isolate traffic between (and even within) VPNs.
3) Multiprotocol and Multilink Support
The label switching forwarding component is not specific to a particular Network Layer. For
example, the same forwarding component could be used when doing label switching with IP as
well as with Internetwork Packet Exchange (IPX). Label switching is also able to operate over
virtually any Data Link Layer protocols, although the initial emphasis is on ATM. The ‗Multi‘ in
MPLS applies above and below the label switching layer.
4) Evolvability
Label switching also has the advantage of a clean separation between its control and forwarding
functions. Each part can evolve without impacting the other part, which makes the evolution of
networks easier, less costly, and less prone to errors.
5) Inter-domain Routing
Label switching provides a more complete separation between inter and intra-domain routing.
This improves the scalability of routing processes and, in fact, reduces the route knowledge
required within a domain. This is a benefit to ISPs and carriers who may have a large amount of
transit traffic (i.e., traffic whose source and destination is not on the network).
6) Support for All Traffic Types
One other advantage of label switching which is not generally visible to the user is that it
supports all types of forwarding: unicast, with type of service, and multicast packets. Label

switching also improves upon the various methods that have been tried for integrating IP with
ATM-based sub networks. This may remove the need for complex procedures and protocols that
deal with issues such as address resolution and the different models for multicast and resource
reservation. Label switching can be used with QoS attributes that, in turn, allow different classes
of ISP access service to be defined. Label switching can permit the actual IP header in a packet
to be encrypted since all that must be available to the LSRs is the label itself. In this way the
sources and destinations of the data are no longer observable while in transit.
2.7 Network Simulators:
Network simulators perform detailed packet-level simulation of source, destinations, reception,
route, background load, links, data traffic transmission and channels. There are various types of
network simulators some of them are describes as follows.
1. NS-2:
Network Simulator (Version 2), called as the NS-2, is simply an event driven, open source,
portable simulation tool that used in studying the dynamic nature of communication network.
Several different NS-2 versions have been released over the last few years; the latest version
of NS-2 is the NS-2.35. Users are feeding the name of a TCL simulation script as an input
argument of NS-2 executable command ns.
Figure 2.4: Architecture of Network Simulators
NS-2 uses two key languages one is the C++ and second is the Object-oriented Tool Command
Language (OTCL). In NS-2 C++ defines the internal mechanism (backend) of the simulation

objects, and OTCL defines external simulation environment (i.e., a frontend) for assembling and
configuring the objects. After simulation, NS-2 gives simulation outputs either in form of NAM
files or trace files. In NS-2 some limitation can be found in terms of the installation process on
windows based operating systems. To run NS-2 on window based environment a software
program is used for creating Unix-like environment known as Cygwin; downloading and
installing of Cygwin on windows based system is quite complex because of large size of
packages of Cygwin.
2.OPNET:
Optimized Network Engineering Tool (OPNET) is a commercial network simulator environment
used for simulations of both wired and wireless networks. Several different OPNET versions
have been released over the last few years; the latest version of OPNET is the OPNET16.0.
Figure 2.5: Graphical user interface of OPNET IT GURU EDITION
At present OPNET is licensed under Riverbed technologies. It allows the user to design and
study the network communication devices, protocols, individual applications and also simulate

the performance of routing protocol. It supports many wireless technologies and standards such
as, IEEE 902.11, IEEE 902.15.1, IEEE 902.16, IEEE 902.20 and satellite networks. OPNET IT
GURU EDITION Academic Edition is available for free to the academic research and teaching
community. It provides a virtual network environment that models the behaviour of an entire
network including its switches, routers, servers, protocols and individual application. The main
merits of OPNET IT GURU EDITION are that it is much easier to use, very user friendly
graphical user interface and provide good quality of documentation.
3.GloMoSim:
GloMoSim (Global Mobile Information System Simulator) is a scalable simulation environment
especially designed of MANET and its applications. It is open source, portable and includes a
large set of routing protocols and several physical layer implementations. It was retired in 2000
but it is still possible to download for educational purposes only. On the other side, Scalable
Network Technologies introduced the commercial version of GloMoSim (Global Mobile
Information System Simulator) named as QualNet (Quality Networking) simulator. The main
merits of QualNet simulator (Quality Networking), is that it is open source portable, highly
scalable and extremely powerful simulator. One of the main merits of QualNet, is that it is run on
both Windows and Unix/Linux platforms.
4.QualNet:
Quality Networking (QualNet) simulator is a highly scalable, fastest simulator for large
heterogeneous network that supports the wired and wireless network protocol. QualNet execute
any type of scenario 5 to 10 times faster than other simulators.
It is highly scalable and simulate up to 50,000 mobile nodes. And this simulator is designed as a
powerful Graphical User Interface (GUI) for custom code development. The main merits of
QualNet simulator (Quality Networking), is that it is portable, highly scalable and extremely
powerful simulator. One of the main merits of QualNet is that it is run on both Windows and
Unix/Linux platforms.
Features:

 fast simulation results for thorough exploration of model parameters;
 fast model set up with a powerful Graphical User Interface (GUI) for custom code
development and reporting options;
 scalable up to tens of thousands of nodes;
 real-time simulation for man-in-the-loop and hardware-in-the-loop models;
 multi-platform support;
2.8. MPLS in OPNET Modeler
In the previous chapters we introduced MPLS and MPLS/DiffServ. In this chapter we will
explain what is necessary to configure in the OPNET Modeler to get an MPLS network working
[23]. There are two different types of LSPs:
2.8.1. Dynamic LSPs
The dynamic LSPs are signaled using RSVP or CR-LDP at the beginning of the simulation. It is
possible to specify some part of the LSP with an explicit route or only specify the beginning (the
ingress LER) and the end of the LSP and the protocols will find a path. In case of working with
dynamic LSP with explicit routes it is necessary to specify each individual router along the path.
It is needed to specify the objects in the same order that they occur in the LSP. In case of
dynamic LSP with OSPF routes it is only necessary to specify the beginning and the end. Also it
is possible to specify some routers or links that must be used.
2.8.2. Static LSPs
Using static LSPs it is possible to specify the static route used by a LSP. In this way, the user
have more control about LSP routes, but in case of a router or link failure the path would fall
down. For this reason, it is possible to specify a backup route when the user is setting static
LSPs. Before LSP are configured, the different devices of the network should have MPLS
enabled and the routing protocol must be OSPF or ISIS. ISIS cannot be used with the modules
we have in our license, so we had to configure the routers with OSPF. OSPF and ISIS are routing
protocols that supports extensions for traffic engineering. To configure MPLS on the routers
selected, it is possible to do it in this way [23]:

Select Protocol  MPLS  Configure Interface Status After the definition of the LSPs or any
changed in one of them, it is necessary to do the next step:
Select Protocols  MPLS  Update LSP Details In order to send traffic through LSPs, it is
necessary to configure more devices. We have to specify the traffic associated to a LSP. There
are two more options: static mappings or IGP shortcuts. a) IGP Shortcuts When the user is using
IGP shortcuts, the network consider the LSP as a single link. In this way, the user have no
control on the traffic that is sent through the LSP and there are no chance of traffic engineering
as it is impossible to differentiate the traffic going into a router. Although it can be useful in
some experiments, we tried several times to set it but it was impossible to send the traffic
through the LSP using IGP shortcuts. b) Static Mappings With the static mappings we are
creating forwarding equivalence classes (FECs) and traffic trunks, which are used to define the
different types of traffic. So, it is necessary to set in the workspace a node called ―MPLS
Configuration‖ and define an FEC and a traffic trunk. ―A traffic trunk is: an abstract
representation of traffic to which specific characteristics can be associated [24]‖. Another
definition is: ―A traffic trunk is a set of flows aggregated by their service class and then placed
on a LSP or set of LSPs called a traffic engineering tunnel‖. It is characterized by the ingress and
egress LSR, the forwarding equivalence class (FEC) and a set of attributes which determine its
behavioral characteristics. In order to define a FEC, the only needed fields we have to fill are:
 A name to differentiate one FEC of the others.
 The destination address of the FEC: give the address of the host or network destination.
The attributes that must be set to define a traffic trunk are:
 The name to identify the traffic trunk
 The characteristics of the traffic profile: maximum bit rate, average bit rate and the
maximum burst size
 The traffic class must be configured to EF, AF11, and AF12… AF42, AF43. This is
useful to define differentiated services for different traffic flows going through the same
LSP. In OPNET Modeler, the priorities between the different classes are defined in the
attribute called ―EXP  PHB‖. This attribute is a table where each value of one of

these classes is mapped to a different value of PHB. The default values, called ―Standard
Mappings‖ give the next priorities:
EF  AF41  AF32  AF31  AF22  AF21 AF11 The expedited forwarding (EF) PHB
is proposed in RFC2598, whereas the assured forwarding (AF) PHB group is presented in
RFC2597. The general Class of Service (CoS), is under the Type of service (ToS) as shown in
Figure 2.6.
Figure 2.6 Types of Traffic (under ToS)
After all the LSPs, FECs and traffic trunks are created, we have to define the static mappings or
the traffic engineering bindings that govern which packets are sent to one LSP or another. To set
these parameters, there are two ways:

1) Manually, do it in the LER‘s MPLS  MPLS Parameters  Traffic Mapping
Configuration attribute and specify the interface where the traffic in getting inside the
LER, the FEC, the traffic trunk and the primary and backup LSPs used.
2) Set it automatically using software developed in order to configure them. This software
is called the MPLS configurator and also set all the information about the FECs and the
traffic trunks.
2.8.3 Adding Traffic to the Network
After creating the network topology, the next step is to add traffic to the network. There are two
options to create traffic:
 Manually, by setting attributes on various network objects

Figure 2.7 types of Traffic (under Differentiated Service Code Point “DSCP”)
 Automatically, by importing traffic from external files or programs.
2.8.4. Types of Traffic
There are two types of traffic that can be modeled by OPNET Modeler: the explicit traffic and
the background traffic [24]. Explicit traffic: This kind of traffic is a packet-by-packet traffic, in
which the simulation models each packet-related event (packet created, packet queued, etc.) that
occurs during the simulation. Explicit traffic modeling provides the most accurate results
because it models all protocol effects. However, this also results in longer simulations (more
CPU instructions are needed) and higher memory usage (because the simulation allocates
memory for each individual packet). There are three general methods for explicitly modeling
traffic in OPNET:
 Packet generation: configuring certain node objects to generate streams of generic
packets. This is a basic method of adding traffic to a network topology.
 Application demands: creating application demands to represent the traffic flowing
between two nodes. The traffic generated by application demands can be purely discrete
(explicit), purely analytic (background), or a combination of these two (hybrid).
Application traffic models: OPNET Modeler includes a set of models for generating traffic based
on standard applications such as FTP, HTTP, voice and e-mail. It is also possible to design the
characteristics of a traffic application.
Background traffic: Background traffic affects the performance of explicit traffic by
introducing additional delays. The simulator model includes the effects of background traffic to
calculate queues on intermediate devices and delays based on the queue length, at any time
during in the simulation. However, each packet of this kind of traffic is not explicitly modeled,
so it will not generate an event in each state of the packet and it does not have a piece of memory
to keep all of its characteristics. Hence, the simulation will be faster and use less memory. In
Modeler there are three ways of generating background traffic:

 Traffic Flows: A traffic flow describes an end-to-end flow of traffic from a source to one
or more destination nodes. It is possible to create traffic flows manually or import them
from external files. The user can set this traffic also as an explicit traffic modifying the
value of the attribute called ‗Traffic Mix‘, where it is possible to set the percentage of
explicit traffic.
 Device/Link Loads: This type of traffic represents traffic as a background load on a link
or node object. Unlike a traffic flow, which can span multiple links and nodes, a traffic
load only affects one object. It is also able to convert existing link loads to traffic flows,
which allows flow analyses to account for these loads. It is also possible to import
device/link loads from external ASCII files.
 Application demands: Represent background traffic flowing between two nodes. As it
has been explained before, this kind of traffic can be purely explicit, background or any
combination of both types.
2.8.5 Detailed Traffic Configuration Options
In the following paragraphs, we give a description of each kind of traffic.
Packet generation: The OPNET model library includes traffic source/sink node models.
These models let the user generate streams of packets that contain no protocol data above layer
2. This way of generating traffic can be useful for studying layer-2 technologies but not for
studying routing protocols and MPLS. Thus, we must discard this way of generating traffic.
Application traffic models: This software includes a large set of models that allow the
user to create explicit traffic based on applications such as FTP, HTTP, etc. In order to set this
kind of traffic it is necessary to set an ―Application Configuration‖ and a ―Profile Configuration‖
in the workspace of the network. A profile is applied to a workstation, server, or LAN. It
specifies the applications used by a particular group of users. An application may be any of the

common applications (such as email and file transfer) or a custom application the user define.
Eight common applications are already defined: Database Access, Email, File Transfer, File
Print, Telnet Session, Video conferencing, Voice over IP Call, and Web Browsing. Furthermore,
it is necessary to place a server to answer the requests made by the different workstations and
also set the parameters in the workstations and in the server
Application demands: This is an easier way to introduce traffic in the network than with
application traffic models. It is not needed to configure some parameters in the sources and the
destinations of the traffic, it is only necessary to configure the application demand itself. These
demands characterize traffic in terms of the size and rate of the requests and responses going
back and forth between two nodes. As with the application traffic model, the traffic from
application demands flows as a series of requests and responses between the application layers of
the end nodes. The source node of the application demand sends requests to the destination node,
which returns responses to the source.
Traffic flows: Another type of background traffic is called a traffic flow, or background
routed traffic. Unlike a device/link load, which models traffic on one link or node, a traffic flow
traverses the network from one source to one or more destinations. The user can create traffic
flows in the network using traffic flow objects. A traffic flow is a network object that connects
two nodes (like a link object) and specifies:
 A traffic source and a traffic destination
 A period of simulation time, which may be divided into time slots
 The rate of traffic (in bits-per-second, packets-per-second, or some other measure) from
source to destination during each time slot.
After the description of each kind of traffic and describing its setting, the most straightforward
traffic to generate and the most suitable available traffic is the ―application demand‖. An
application demand has to be defined between 2 workstations and it is not possible to define it
between two routers. Thus, it is necessary to introduce a workstation linked to a router to

generate traffic between two nodes of the network (one workstation for the source and another
for the destination of the application demand).
Chapter 3
PROJECT ESSENTIALS
3.1 Front End Tool Used (OPNET 14.5):
OPNET Modeler uses modern simulation techniques to reduce research costs and ensure proper
insight of a theoretical network. OPNET Modeler‘s cutting-edge technology provides an
environment for designing protocols and technologies as well as testing and demonstrating
designs in realistic scenarios prior to production. OPNET Modeler is used by the world's largest
network equipment manufacturers to enhance the design of network devices, technologies such
as VoIP, TCP, OSPFv3, MPLS, IPv6, and much more. For our research work we have
implemented multiple design scenarios, using OPNET Modeler, in order to compare the results
at the time of execution. OPNET Modeler 14.5 is a significant software update to the OPNET
11.5 & 12 software releases that we started our thesis work with. The previous versions were
very limited in features and did not comply with the requirements of our thesis. The release 14.5
contains many new features and enhancements to existing capabilities. This release also
implements suggestions and fixes many software problems reported in earlier releases.
It provides a virtual network environment that models the behaviour of an entire network
including its switches, routers, servers, protocols and individual application. The main merits of

OPNET are that it is much easier to use, very user friendly graphical user interface and provide
good quality of documentation.
OPNET Modeler constitutes a network simulation program based on C and C++, which offers a
convenient GUI in order to facilitate users to conduct network experiments. OPNET Modeler
includes model libraries that represent various network hardware devices from many vendors and
various communication protocols. Thus, the OPNET Modeler users are able to simulate large
network environments with network devices and routing protocols of will, without the need of
pursuing real equipment, saving this way cost. The specific program also gives the capability to

Figure 3.1 OPNET MODELER
add or modify existing models, and bases its simulations on the Discrete Event Simulation
system which uses defined processes to model network events. Additionally, traffic patterns can
be simulated by the use of network layer traffic flows, by well-defined applications or by
transport layer application demands.
Fig: 3.2 Flowchart of OPNET
The sequence of the needed acts needed for a network simulation, includes the design and
configuration of the network topology, the selection of the desired measured metrics, the
simulation run and the analysis of the calculated statistics. Eventually, OPNET Modeler is
considered a reliable program when it comes to network evaluation, usually met on computer
networking publications and also used by industry. These advantages of the program led the
author to select it as the tool to facilitate the intended experiments.
3.2 Back End Tool Used (Visual Studio 2010):
Visual Studio is a complete set of development tools for building ASP.NET Web applications,
XML Web Services, desktop applications, and mobile applications. Visual Basic, Visual C#, and

Visual C++ all use the same integrated development environment (IDE), which enables tool
sharing and eases the creation of mixed-language solutions. In addition, these languages use the
functionality of the .NET Framework, which provides access to key technologies that simplify
the development of ASP Web applications and XML Web Services. Microsoft Visual Studio is
an integrated development environment (IDE) from Microsoft. It is used to develop computer
programs for Microsoft Windows, as well as web sites, web applications and web services.
Visual Studio uses Microsoft software development platforms such as Windows API, Windows
Forms, Windows Presentation Foundation, Windows Store and Microsoft Silver light. It can
produce both native code and managed code.
Visual Studio includes a code editor supporting IntelliSense as well as code refactoring. The
integrated debugger works both as a source-level debugger and a machine-level debugger. Other
built-in tools include a forms designer for building GUI applications, web
designer, class designer, and database schema designer. It accepts plug-ins that enhance the
functionality at almost every level—including adding support for source-control systems
(like Subversion) and adding new toolsets like editors and visual designers for domain-specific
languages or toolsets for other aspects of the software development lifecycle(like the Team
Foundation Server client: Team Explorer).
Visual Studio supports different programming languages and allows the code editor and
debugger to support (to varying degrees) nearly any programming language, provided a
language-specific service exists. Built-in languages include C, C++and C++/CLI (via Visual
C++), VB.NET (via Visual Basic .NET), C# (via Visual C#), and F# (as of Visual Studio 2010.

REFERENCES
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[8] Hunt R, "A review of quality of service mechanisms in IP-based networks - integrated and
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[14] Peng Z, Zhansong M, Raimo K, ―Designing A New Routing Simulator for DiffServ MPLS
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Polytechnic Institute and State University, 2001.
[16] Youngtak K, Eunhyuk L, and Douglas M. "Discrete Event Simulation of the DiffServ-over-
MPLS with NIST GMPLS Lightwave Agile Switching Simulator (GLASS)", National Institute
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Engineering To Improve QoS Routing on IP Networks‖, IEEE SoutheastCon conference, Florida
Institute of Technology, Melbourne, FL, 2002.

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