A Study of MPLS

Department of Computing Science & Engineering

DE MONTFORT UNIVERSITY,

LEICESTER, U.K.

By

PARMINDER SINGH KANG

Email: pkang@dmu.ac.uk

Home: www.cse.dmu.ac.uk/~pkang

Why MPLS?

• Interest.

• New and Different concept.

• MPLS merges the connection oriented and packet switching approach.

• Overlays the layer of intelligence over existing IP network.

• Different implementation approaches.

Introduction

• Introduction to Networks

•Technical Description

•MPLS: The Basic Concept

•MPLS: The Data Plane

•MPLS: The Control Plane

•Implementation

•LDP

•Conclusion and Future Work

Introduction to Networks

• What is a Network?

• Broadcasting and Switching.

• Connection Oriented Packet Switching.

• Operation

Call Setup

Data Transfer

Call Termination

Traditional Approach

• Connectionless mechanism.

• IP address based Forwarding.

• Routing Decision is based upon routing tables.

• Main routing protocols are: RIP, IGRP, OSPF, IS-IS and BGP.

Application

Transport

Internet

Data Link

Internet

Data Link

Internet

Data Link

Application

Transport

Internet

Data Link

Ethernet EthernetCore Network

• packets are routed independently to the destination even if they are from the same source.

•Consider two Paths:

Path1: node1-router1-router2-router4-node2

Path2: node1-router1-router3-router4-node2

Router 1

Router 2

Router 3

Router 4

Node 1

Node 2

3 2 1

3

1

1

3

2

2

3 1 2

• Major Drawbacks:

• Difficult to deliver QoS in multi service network.

• There is no relation between packet and forwarding path opted.

• Routing Bottlenecks.

•Inefficient utilization of network resources.

• Solution? MPLS

MPLS: Connection Oriented Packet Switching

• MPLS: Multiprotocol Label Switching.

• Merges the concept of Packet Switched networks and Connection oriented approach.

• Implemented as an individual layer between IP layer and DLL layer.

Application

Transport

Internet

Data Link

MPLS

Data Link

MPLS

Data Link

Ethernet EthernetCore Network

MPLS

Application

Transport

Internet

Data Link

MPLS

• Operation is divided into two planes: Control plane and Data Plane.

• Forwarding is based upon label switching instead of long IP address match.

Label Selection and Distribution

Protocol

LIB

Data plane

Control plane

IP Routing Protocol

IP Routing Table

Label Forwarding table

DLL MPLS IP Higher Layer Protocols

32 bits

20 3 1 8 bits

Label QoS S TTL

Link 1 Link 2

Link 3

LER1LSR2

LER2MPLS Domain

120.10.4.1 100.101.4.11

IP network

Destination address Source address

FEC = 3Interface = 1Label = 40

Interface = 3Label = 10

Interface = 2Label = 14

LSR1

Router Incoming Label Outgoing Label Incoming interface Outgoing Interface

LER1 N/A 40 10 1

LSR1 40 10 1 3

LSR2 10 14 3 2

LER2 14 IP based Forwarding

2

Advantages of MPLS

• Defines relation between stream and LSP.

• Fast Switching.

• Effective network resource utilization.

• Easy to implement VPN and QoS delivery.

• Can interoperate with other major technologies; FR and ATM.

• Connectionless operation is still available.

LDP

• LDP: Label Distribution Protocol

• LDP plays vital role in data transfer.

• LDP is divided into two major categories:

Explicit: LDP Hop-by-Hop and LDP-CR.

Extension to existing protocols: RSVP-TE, MPLS-BGP.

• Four message Types: Notification, Discovery, Session and Advertisement.

• Working

• Concept of TLV.

• Working

LER1 LSR1 LER2LSR2Incoming stream S, FEC F

LABEL_REQUEST LABEL_REQUEST LABEL_REQUEST

LABEL MAPPING LABEL MAPPING LABEL MAPPING

Data Flow

Discovery

Session establishment.

Label binding.

Data Transfer.

Upstream LSR Downstream LSR

UDP Hello

UDP Hello

TCP Connection Establishment

LDP Initializations

LDP Label Request

LDP Label Mapping

Data Transfer

Time

0 Notification (0x0001) Length

16 bits 16 bits

Message ID

Mandatory Parameters

Optional Parameters

• Concept of TLV

Unique message structure.

Type, Length and Value.

Implementation

•Topology Used

Ingress LER

Egress LER

LSRClient

MPLS Domain

MPLS_Monitor

•Assumptions:

• Communication is Unidirectional only.

• Single LSP.

•Only one MPLS domain exists.

•Each router has only two interfaces.

•This model uses static routing tables.

Conclusion and Future Work

• Conclusion.

• Future Work:

• Multicasting in MPLS.

• Solution for Data plane and Control plane failure. One possible approach is OAM.

• LDP Security.

• Lack of outgoing label.

• Loop prevention plays a vital role in effective operation.

• Finally, overlaying TE capabilities on existing structure.

Thanks…..

Questions…….