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A Study of MPLS Department of Computing Science & Engineering DE MONTFORT UNIVERSITY, LEICESTER, U.K. By PARMINDER SINGH KANG Email: firstname.lastname@example.org 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
Application Application Transport Transport Internet Internet Internet Internet Data Link Data Link Data Link Data Link Ethernet Ethernet Core Network 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.
3 Router 2 1 3 1 3 1 2 Router 1 Router 4 3 2 1 Node 1 Node 2 2 Router 3 2 • 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
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 Application Transport Transport Internet Internet MPLS MPLS MPLS MPLS Data Link Data Link Data Link Data Link Ethernet Ethernet Core Network
IP Routing Protocol IP Routing Table Control plane Label Selection and Distribution Protocol LIB Label Forwarding table Data plane 32 bits DLL MPLS IP Higher Layer Protocols 20 3 1 8 bits • Operation is divided into two planes: Control plane and Data Plane. • Forwarding is based upon label switching instead of long IP address match. Label QoS S TTL
FEC = 3 Interface = 1 Label = 40 Interface = 2 Label = 14 Source address Destination address 18.104.22.168 100.101.4.11 LSR1 LSR2 Link 1 Link 2 LER1 IP network Interface = 3 Label = 10 Link 3 LER2 MPLS Domain
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.
LSR1 LSR2 LER2 LER1 Incoming stream S, FEC F LABEL_REQUEST LABEL_REQUEST LABEL_REQUEST LABEL MAPPING LABEL MAPPING LABEL MAPPING Data Flow • Working • Discovery • Session establishment. • Label binding. • Data Transfer.
Downstream LSR Upstream LSR UDP Hello UDP Hello TCP Connection Establishment Time LDP Initializations LDP Label Request LDP Label Mapping Data Transfer
16 bits 16 bits 0 Notification (0x0001) Length Message ID Mandatory Parameters Optional Parameters • Concept of TLV • Unique message structure. • Type, Length and Value.
MPLS Domain Ingress LER Egress LER Client LSR MPLS_Monitor Implementation • Topology Used • 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.