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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…….
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