Mechanisms for OAM on MPLS

in large IP backbone networks

 

 

 

Masters Thesis,

Information and Communication Technology

 

Agder University College

Faculty of Engineering and Science

 

 

 

By

 

Hallstein Lohne

Johannes Vea

 

Grimstad, May 2002

 

 

 

 

Keywords: OAM, MPLS, BACKBONE, IP, ETHERNET, SNMP


Abstract

The telecom industry has an ongoing work on the Operation and Maintenance (OAM) mechanisms for the MultiProtocol Label Switching (MPLS) technology. We are expecting that this technology will be the future platform for sending Internet Protocol (IP) packets through the backbone networks. OAM functionalities that exist or are proposed for MPLS are: Reachability and failure detection, avoidance of congested routers, Simple Network Management Protocol (SNMP) features, fast rerouting functions, traffic engineering and ad-hoc mechanisms like Ping.

 

Our work shows that through a comparison of OAM mechanisms of MPLS to IP, MPLS is superior on the failure detection, fast rerouting and the traffic engineering functionalities. A mechanism shows how one can use our new algorithm (a patent application is planned) to detect specific traffic behavior, making the MPLS backbone handle this traffic more logic. Different OAM mechanisms for MPLS give different levels of redundancy, which is often proportional to the OAM traffic load. We have found that the Connectivity Verification (CV) traffic load should be differentiated between the Label Switched Paths (LSPs) that need protection switching and those that do not. A short period between LSP CV packets is needed whilst still providing the best available bandwidth for working traffic A table shows different proposed fast rerouting and protection switching mechanisms, easing the operator’s choice of that mechanisms to use in large MPLS backbone networks. We propose the ITU-T LSP connectivity verification mechanism, fast rerouting and protection switching, and the use of MPLS MIB as recommended OAM mechanisms for large backbone networks.


Preface

This thesis is written for the Network Access department at Ericsson, Grimstad, and is a part of the Graduate degree (Siv. ing) in Information and Communication Technology (ICT) at Agder University College. This thesis is also a contribution to the research and development program The Mobile Student.

 

The work on this thesis began in January 2002 by getting an overview of the main technologies involved and an understanding of the meaning of the term OAM. In the beginning of February 2002 we got in contact with Cisco in Norway, hoping to run a MPLS testbed at their test labs in Oslo. Many days were used for studying Cisco routers, MPLS protocols, packet monitoring and various software solutions for various measurements. When we were prepared to start testing in the start of April, Cisco did not get the equipment needed in time, and therefore the testbed was not feasible.

 

Three supervisors have inspired us and been helpful in our work; they are Frode Trydal (Ericsson), Stein Bergsmark (Systems Manager, Ericsson) and Frithjof Fjeldstad (Agder University College). Discussion with and questions to persons attending various mailing lists have also given valuable information, and vice versa. We would like to thank the following people for providing us with answers to our questions posted at the various resources we have been using: Neil Harrison (British Telecom), David Allan (Nortel Network), Carlos Patriawan (Pluris.com), Carrie D. Harris (former Ericsson employee), Eng Wee, Mr. Ganesh (lntinfotech.com), Mark Gibs (onorchestream.com), Nirmit Kachrani (avaya.com), Mathew Lodge (cplane.com), Peter Morgan (AT&T), Mahesh Vsjetti (hns.com), Pall Ramanathan (arrisi.com), Robert Raszuk (Cisco), Roger Clark Williams (nordlink.com), Dr. Sidnie Feit (The Standish Group and a well-known author), Thomas D. Nadeau (Cisco) and Vic Nowoslawski (mac.com).

 

Our thesis can be used to get an overview over MPLS and IP networks and provide an understanding of the OAM principles within an MPLS backbone network. We hope it will help Ericsson and others in finding the best solution to their future backbone networks.

 

 

Grimstad, May 2002

Johannes Vea and Hallstein Lohne


Contents

Title
Abstract
Preface

1 Introduction

1.1 Thesis introduction
1.2 Thesis description
1.3 thesis progress
1.4 literature review
1.5 Report outline

2 An outline of IP and MPLS technologies

2.1 Introduction
2.2 OAM and backbones in general
2.2.1 What is OAM?
2.2.2 A short introduction to backbones
2.3 Forwarding mechanisms in IP
2.3.1 An overview of the IP architecture
2.3.2 Routing and forwarding
2.4 The MPLS architecture and its forwarding mechanisms
2.4.1 The MPLS architecture
2.4.2 The control component
2.4.3 The forwarding component
2.4.4 An example of forwarding

3 A classification of OAM functionalities

3.1 Introduction
3.2 Network Management
3.2.1 Network Management Architectures
3.2.2 SNMP
3.3 OAM on IP
3.3.1 Ping and ICMP
3.3.2 Traceroute
3.3.3 IP MIBs
3.3.4 New OAM functions in IPv6
3.3.5 ITU-T's future OAM on IP
3.4 OAM on MPLS
3.4.1 Current work overview
3.4.2 LSP connectivity
3.4.3 MPLS Ping
3.4.4 RSVP node failure detection
3.4.5 Protection Switching
3.4.6 Fast rerouting
3.4.7 MPLS and traffic engineering
3.4.8 MPLS SNMP MIBs

4 A comparative analysis of OAM mechanisms

4.1 Introduction
4.2 Failure detection
4.3 Reachability features
4.4 Avoidance of congested routers
4.5 SNMP features
4.6 Ping and traceroute
4.7 Fast rerouting and Protocol switching
4.8 Traffic engineering

5 Our recommended mechanisms and new ideas

5.1 Introduction
5.2 Recommended OAM mechanisms for large backbone networks
5.3 Differentiation of connectivity traffic
5.4 Classifying the traffic

6 Conclusion

Abbreviations
Terms
References

Appendix A - Configuring Routers
Appendix B – Open Shortest Path First (OSPF)
Appendix C – An MPLS Scenario
Appendix D – Classifying the traffic (restricted)


MECHANISMS FOR OAM ON MPLS IN LARGE IP BACKBONE NETWORKS (c) 2002 Hallstein Lohne, Johannes Vea, a graduate thesis written for AUC/ERICSSON