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Lecturer :Assoc. Prof. Dr Mohamed Othman

By: Omer Mahmoud, Farhat Anwar , Momoh Jimoh E. Salami

Simulation and analysis of an admission control

mechanism for MPLS DS-TE

2008 Elsevier

Presenter : Nageeb Yahya Alsurmi GS21565

UPM University SKR 5306 Advanced Computer Network

Date : 15-07-2009

MPLS DS-TE

Introduction Problem Statement Objective

QoS – DiffServMPLS DS-TEAdmission Control Mechanism Methodlogy

Simulation Setup Performance metrics

Simulation results and analysisConclusionReferences

Outline

MPLS DS-TE

Introduction The internet architecture was originally designed to

provide IP based ‘‘best-effort” services to all its applications.

The Internet is currently a Single Queue Best Effort network– Internet2 Project Abilene is DiffServ multi-priority

QoS testbed

“Best-effort” service describes a network service which attempts to deliver traffic to its destination, but which does not provide any guarantees of delivery, without any commitments for delay, jitter, loss, and throughput (bandwidth)

It is inadequate for new classes of emerging applications with real time data such as audio and video streaming

In contrast, Quality of Service (QoS) provides a high data throughput (bandwidth) and low-latency.

Introduction

In order to provide a low-delay, low-jitter and low-loss service (QoS) the network must be engineered (MPLS TE) to remove all points of congestion (Admission Control) on the end-to-end path for that service; in order to assure different SLAs (Service Level Agreements) for different classes of traffic (hence minimizing cost).

QoS—quality of service. A measure of performance for a transmission system that reflects its transmission quality and service availability.

MPLS DS-TE

MPLS DS-TE

Introduction ….(cont…)

Proplem Statement When DiffServ traffic flows via an MPLS domain, a

DiffServ QoS might not be maintained.To preserve this QoS an arrangement is essential so that multiple DiffServ domains can be connected through MPLS backbone network for allocating and controlling the bandwidth within MPLS domains.

MPLS DS-TE

Introduction ….(cont…)

The Objective Improving the Admission control mechanism

whereby DiffServ expedited forwarding (EF) per-hop behavior can be admitted to an MPLS TE tunnel to ensure stable performance for the traffic in the MPLS Domain.

MPLS DS-TE

QoS

Intserv provides QoS by reserving the resources in the network from the source to destination using resource reservation signaling protocol (RSVP)

DiffServ provides a spectrum of services , classifying, managing network traffic, mark packets as belonging to a specific class and assign relative priorities to packets to reflect the differential level of treatment to be afforded that packet.

MPLS provides QoS by using switching mechanism unlike conventional IP routing mechanism ,MPLS uses label information to identify packets and forwards packets based on label information which is faster than if compared with packet’s IP destination address routing.

IP QoS

IntServ DiffServ MPLS

guaranteed QoS statistical QoSclassify packets

MPLS DS-TE

QoS architectures The component of QoS feature that recognizes and

distinguishes between different traffic streams. Without classification, all packets are treated the

same.

DiffServ provides a scalable means of service differentiation in the Internet. It classifies all the traffic into categories or classes in order to provide differential treatment between these classes.

DiffServ can be used to provide low-latency, guaranteed service (GS) to critical network traffic such as voice or video while providing simple best-effort traffic guarantees to non-critical services such as web traffic or file transfers.

DSCP: Differentiated Services Code Point marking each packet on the network with a DSCP code and appropriating to it the corresponding level of service.

MPLS DS-TE

Differentiated IP Services

Guaranteed: Latency and Delivery

Best Effort Delivery

Guaranteed Delivery

Voice

E-mail, WebBrowsing

E-Commerce

Application Traffic

Platinum Class Low Latency

Silver

Bronze

Gold

VoiceVoice

TrafficClassification

TrafficClassification

DiffServ Model

MPLS DS-TE

MPLS MPLS is a method of forwarding packets that

integrates layer 2 and layer 3 functionalities. MPLS uses a technique known as label switching to forward data through the network.

One of the significant initial applications of MPLS is its ability to use traffic engineering (TE).

TE: is the process of controlling how traffic flows through a network so as to optimize resource utilization and network performance.

TE algorithms calculate explicit routes to one or more nodes in the network called tunnel. MPLS is more suitable for use as a backbone ,it offers more flexible bandwidth management capabilities.

MPLS DS-TE

MPLS Applications

MPLS Applications MPLS VPN – Layer-3

Detailed Overview IOS Examples

MPLS Layer-2 Transport

PWE3/AToM Application Example

MPLS TE Traffic Engineering

Fast-ReRoute for Bandwidth Protection

MPLS QoS Diffserv over MPLS Diffserv TE (DS-TE)

Guaranteed Bandwidth Service Applications , Useful Implementations

Combining Multiple MPLS Services

IP version 6 (IPv6) Transport Methods over MPLS

6PE/6VPE (IPv6 Edge and VPN Support)

Combining TE, TE-FRR, and DS-TE, high-availability for low-latency applications (e.g. Voice and Virtual Leased Line)

MPLS DS-TE

MPLS DS-TE (TE aware DiffServ )

The basic functions provided by DS-TE are:• separate bandwidth reservations for different sets

of traffic classes.• admission-control procedures applied on a per-

class basis.

DS-TE is more than MPLS TE + MPLS DiffServ

DS-TE makes MPLS TE aware of DiffServ: DS-TE establishes separate tunnels for different

classes DS-TE takes into account the “bandwidth”

available to each class (e.g. to queue) DS-TE takes into account separate engineering

constraints for each class e.g. I want to limit Voice traffic to 70% of link

max, and the rest for other traffics.

DS-TE ensures specific QoS level of each DiffServ class is achieved

MPLS DS-TE

CORE

POP 4

POP

POPPOP

POP 1

MPLS DS-TE with DiffServ Network

Find Route and Set-Up Tunnel for 5 Mb/s of EF From POP1 to POP4

Find Route and Set-Up Tunnel for3 Mb/s of EF From POP2 to POP4

Find Route and Set-Up Tunnel for 15 Mb/s of BEFrom POP1 to POP4

Find Route and Set-Up Tunnel for 7 Mb/s of BE From POP2 to POP4

POP 2

MPLS DS-TE

Traffic admission control Admission control is the process of determining whether

a new traffic flow, stream or logical connection may be accepted, taking into account resource and policy constraints.

Admission control is to ensure that there is sufficient link or class capacity available at the required service level to accept a new request.

In case there is no admission control ,For real time traffic , if there is an VoIP application requests a 500kb/s as bandwidth to be reserved but the available is 200kb/s , then how will be the Quality of voice ?? The stream progress will be degraded.

The Admission control with DiffServ has the solution for this isuue, by classifying the traffic to service classes and allocating with reserving a resources in MPLS network with regard to the classes.

The Bandwidth agent BA is the controller of Admission control is not only allocation of the traffic to service classes within its domain but also to send the configuration parameters to the edge routers.

The BA first authenticates each requester and then decides whether there is sufficient bandwidth to meet the particular service request.

MPLS DS-TE

When is Admission Control Needed

Admission Control is only practically useful if the following four conditions are met :

Without admission control, the offered load may exceed the available capacity.

Network working case conditions. If there were insufficient bandwidth to support the peak call load in normal working case conditions,then AC would be required to cover both working and failure cases.

Single network element failure conditions : during network failures, AC provides the capability to reject new or rerouted service requests so that those already granted admission continue to maintain their committed service

Multiple network element failure conditions

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IP admission control taxonomy

IP admission control taxonomy :

MPLS DS-TE

Traffic admission control Mechanism

There are two domains, each one have a Bandwidth Agent (BA) for Admission control.

BA Can manage the requested resources in its domain.

the traffic is traversing

more than one domain, the BAs within these domains would communicate before admitting the traffic in order to ensure the availability of the

requested resources.

MPLS DS-TE

Admission Control Mechanism (Cont..)

The BA first authenticates each requester and then decides whether there is sufficient bandwidth to meet the particular service request.

The BA also maintains agreement with BAs in neighboring domains

For flows that request service to a destination in a different domain, the BA cheeks to see that the requested flow conforms to the prearranged allocation through the appropriate next-hop domain.

The BA then informs the appropriate neighboring bandwidth agent of the new rate allocation and notifies its border router to handle the new flow accordingly.

MPLS DS-TE

Admission Control Mechanism (Cont..)

BAs communicate with edge routers using the common open policy service (COPS) protocol . Communication is achieved by three kinds of COPS messages: request (REQ), decision (DEC) and report (RPT).

DiffServ edge router (DER) sends a REQ message requesting resource to maintain QoS parameter for its flow in MPLS domain. MPLS edge router (MER) forwards the REQ to the BA. The BA then replies by sending a DEC. the MPLS edge router communicates thedecision to DER. Then the DER sends (ACK) to indicate its position (e.g. acceptance). Then the MER replies by sending the configuration result

(i.e. success or failure) to the BA via a Report message Whenever there is a change in the resource availability,

the BA may initiate the admission control process by informing the MER through a DEC message containing the updated parameters.

MPLS DS-TE

Methodology

Simulation Setup The performance of the proposed mechanism has

been evaluated by NS-2 network simulator. It consists of two edge routers (R1 and R3) and one

core router (R2) representing the simulated MPLS domain.

The edge routers are capable of mapping incoming EF flows to specific MPLS tunnels.

Four flows (F1, F2, F3 and F4) are transmitted from sources S1 and S2 to the destination D 80% bandwidth of the link is dedicated to tunnel 1 20% bandwidth of the link is dedicated to tunnel 2 F1= 500kb/s, F2=500kb/s, F3=300kb/s, F4=500kb/s

S1= 1500kb/s

S2= 300kb/s

MPLS DS-TE

The QoS for the flow is maintained using multiple queues which are implemented in the routers of the MPLS domain

There are four simulation scenario to investigate impact of the proposed mechanism.

Performance metrics: Throughput Delay Jitter Packet Losses

MPLS DS-TE

Simulation results and analysis

Simulation scenario 1- Ideal state (one queue / two Queues)

ideal situation where resources (bandwidth) are adequate to accommodate all incoming traffic.

Used for comparison with other scenarios.

The link bandwidth between routers is set to 2 Mbps.

It is observed that all the traffic

(flow F1, F2, F3 and F4) achieve the required maximum throughput for both queuing arrangements

MPLS DS-TE

Results – scenario2

Scenario 2 (single Queue, single tunnel) – congested network

represents a situation where resources (bandwidth) are inadequate

to accommodate all incoming traffics Set link bandwidth between routes to 1.5 Mb/s Use one Queue

It is also observed that the achieved throughput is less than the required maximum throughput

This is due to packet loss in the routers as a result of congestion

MPLS DS-TE

Results – scenario3Scenario 3 (two Queues, two tunnels) –

congested network The same as scenario 2 Two queues for all routers. link bandwidth = 1.5Mb/s. (F1,F2,F4) use Tunnel 1 and Q1 with 80% utilization of

1.5mb/s= 1.2mb/s. F3 use Tunnel 2 and Q2 with 20% utlization of 1.5mb/s

= 300Kb/s. flow F3 has achieved the maximum throughput. Flow (F1,F2,F4) resulting Packet losses and this leads

to lower throughput.

MPLS DS-TE

Results – scenario4Scenario 4 (two Queues, two tunnels) –

congested network with delay: This is similar to scenario 3 except that flow F2 starts

to generate traffic 10 s later than the remaining flows

(F1, F3,F4).

flows F1, F3 and F4 achieve the maximum throughput for the first 10 s. After that decreased when F2 starts to generate traffic.

while F3 remains unaffected and maintains its throughput

MPLS DS-TE

Result Analysis -Delay, jitter and losses

scenario 2 and 3 are used to study the effect of the proposed mechanism on the delay, jitter and packet losses of the traffic flows.

all the flows in scenario 2 suffer from long delay, high-jitter and losses due to inadequate resources in the tunnel. This is because all the

flows are competing for the available bandwidth on equal basis. in scenario 3 shows that by utilizing separate

queues selected flows will be protected and achieve

stable performance . These results show that delay, jitter, and

throughput for flow F3 has improved when separate queue

(Q2) is dedicated and 100% throughput is achieved.

MPLS DS-TE

Conclusion

Traffic flows crossing an MPLS domain are adversely affected by inadequate resource in MPLS tunnels especially flows with high QoS parameters such as DiffServ EF.

An improved admission control mechanism has been proposed

which enables tunnel differentiation by employing multiple queues to improve the situation.

This allows QoS to be preserved in transit MPLS network leading to end to end QoS when handling DiffServ EF traffic.

MPLS DS-TE

References [1] R. Braden, D. Clark, S. Shenker, Integrated services in the

internet architecture: an overview, RFC 1633, 1994. [2] S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, W. Weiss,

An architecture for differentiated services, RFC 2475, 1998. [3] E. Rosen, A. Viswanathan, R. Callon, Multiprotocol label

switching architecture, RFC 3031, 2001. [4] J. Wroclawski, The use of RSVP with IETF integrated services,

RFC 2210, 1997. [5] F. Le Faucheur, W. Lai, Requirements for support of

differentiated services-awareMPLS traffic engineering, IETF, RFC 3564, July 2003.

[6] F. Le Faucheur, Protocol extensions for support of DiffServ-aware MPLS traffic, IETF, RFC 4124, June 2005.

[7] F. Le Faucheur, W. Lai, Maximum allocation bandwidth constraints model for DiffServ-aware MPLS traffic engineering, IETF, RFC4125, June 2005.

[8] B. Davie, A. Charny, J.C.R. Bennet, K. Benson, J.Y. Le Boudec, W. Courtney, S. Davari, V. Firoiu, D. Stiliadis, An expedited forwarding PHB (per-hop behavior), RFC 3246, 2002.

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