First published 2011 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc. Adapted and updated from Gestion des ressources et des défaillances dans les réseaux IP, MPLS et Ethernet published 2009 in France by Hermes Science/Lavoisier © LAVOISIER 2009

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Library of Congress Cataloging-in-Publication Data

Perez, Andre.

[Gestion des ressources et des defaillances dans les reseaux IP, MPLS et Ethernet. English]

IP, Ethernet, and MPLS networks: resource and fault management / Andre Perez.

p. cm.

Includes bibliographical references and index.

ISBN 978-1-84821-285-5

1. Computer networks--Management. 2. Computer networks--Quality control. 3. Resource allocation. 4. Fault-tolerant computing. I. Title.

TK5105.5.P471613 2011

004.6--dc22

2011006657

British Library Cataloguing-in-Publication Data

A CIP record for this book is available from the British Library

ISBN 978-1-84821-285-5

Preface

This book addresses two aspects of network operation quality; namely, resource management and fault management.

Network operation quality is among the functions to be fulfilled in order to offer quality of service, QoS, to the end user. It is characterized by four parameters:

– packet loss;

– delay;

– jitter, or the variation of delay over time;

– availability.

Resource management employs mechanisms that enable the first three parameters to be guaranteed or optimized. Fault management aims to ensure continuity of service.

Internet Protocol (IP), Multiprotocol Label Switching (MPLS) and Ethernet are the main technologies deployed by operators, in the case of wide area networks (WANs), and by businesses, in the case of local area networks (LANs). Initially, these technologies were not designed to deal with resource management, which partly explains their simplicity and commercial success. The features offered were sufficient at the time to offer services without QoS (best effort) constraints, such as web access and electronic messaging.

Resource management is indispensable when QoS constraints need to be taken into account. Voice and video are two applications illustrative of strong QoS requirements. Resource management can be provided using two different approaches:

– resources are managed node by node. No resource is allocated to a flow from end to end. In this case, there is a risk of congestion, as the resources of one node may become insufficient to meet demand. The network thus offers relative QoS;

– resources are allocated to a flow from end to end. The Connection Admission Control (CAC) function allows congestion to be avoided in the network, in that case offering guaranteed QoS.

Deployed networks essentially implement relative QoS, as they have the advantage of simplicity compared with guaranteed QoS. The oversizing of current networks, associated with traffic measurement functions that feed into capacity planning, has so far enabled congestion problems to be solved in a satisfactory manner.

Such a mode of operation can prove inadequate in cases of large increases in video traffic. The latter can be classified according to two communication patterns:

– broadcast video. A video source broadcasts one and the same program to several users. Resource consumption depends on the number of sources and is relatively independent from the number of users. A network offering relative QoS allows for the transport of this type of traffic, whose increase is not dramatic;

– unicast video. The video signal is exchanged in real time between a source and a user (on-demand video) or between two users. Resource consumption depends on the number of users. Given the required throughput per video program, oversizing the network may not be an adequate response. A network offering guaranteed QoS may prove to be the only option for this type of traffic.

Fault management relies on devices that enable a reconfiguration of the network following a fault in a node or link, and the reconfiguration of a node following a fault in the data processing board of the control plane.

The main parameter associated with the reconfiguration of the network is the convergence time. This is relatively long for IP and Ethernet networks. Depending on network size, it can reach several tens of seconds. These values may be sufficient for businesses that deploy LANs. In contrast, operators that deploy WANs require substantially quicker times and seek values less than one second or even one tenth of a second.

The reconfiguration of the node, upon its detection by adjacent nodes, will cause a first reconfiguration of the network when the processor board is faulty, and a second reconfiguration of the network once switching to the standby board has taken place. The purpose of Graceful Restart-type mechanisms is to avoid this double switching.

Consequently, this book is structured in 10 chapters; the main topics discussed therein are summarized in the following table.

Chapter
Designation
Description

1
Network Operation
IP, MPLS, Ethernet technologies

2
Characterizing Quality of Service
Operation quality parameters, requirements of applications, the service contract

3
Transport Protocols
The TCP, UDP, RTP, DCCP, and SCTP protocols

4
Implementing Operation Quality
Mechanisms associated with the user plane

5
IP Technology – Resource Management
Relative QoS: the DiffServ model; Guaranteed QoS: the IntServ model and the RSVP protocol

6
IP Technology – Fault Management
Network reconfiguration: LAN-side HSRP and VRRP protocols, WAN-side OSPF and BGP routing protocols.
Node reconfiguration: the Graceful Restart mechanism

7
MPLS Technology – Resource Management
Relative QoS: DiffServ support; Guaranteed QoS: traffic engineering and the RSVP-TE and OSPF-TE protocols

8
MPLS Technology – Fault Management
Node reconfiguration: the Graceful Restart mechanism and the LDP and RSVP-TE protocols.
Network reconfiguration: the FRR mechanism

9
Ethernet Technology – Resource Management
Relative QoS: frame tagging; the PON access network.
Guaranteed QoS: the SBM protocol

10
Ethernet Technology – Fault Management
Network configuration: the STP, RSTP, and MSTP protocols; linear protection.
Link reconfiguration: the LACP protocol

Chapter 1

Network Operation

1.1. Basic concepts

The purpose of the network is to convey data between the terminal stations, or hosts. The network is comprised of nodes that are interconnected with one another by links. The network nodes perform two elemental functions:

transmission: this function allows for the adaptation of the data to be transmitted on the transmission medium (copper pair, optical fiber, free space);

connectivity: this function allows for the transfer of the data between an input and an output of the network node.

The network includes two entities:

the local area network (LAN): this is a private network, deployed inside a company, and provides a connection between hosts (client stations, servers, telephone terminals);

the wide area network (WAN): this is a public network, deployed by operators or service providers, and provides interconnection between LANs. The WAN is comprised of access networks, aggregation networks, and a core network.

1.1.1. Layered structure

The transmitted data are structured in layers (Figure 1.1). Each layer implements an encapsulation that corresponds to a PCI (protocol control information) header including fields whose interpretation is defined by a protocol. The Internet or Transmission Control Protocol (TCP)/Internet Protocol (IP) model is composed of three layers:

the application layer (layer 7), which enables communication between distant software applications. The obtained data structure constitutes the message;

the transport layer (layer 4): the TCP and UDP (User Datagram Protocol) are the most common protocols. The transport layer enables a remote application to be addressed through a target port number. The TCP additionally makes it possible to check that the data transfer was performed properly from end to end. The Real-time Transport Protocol (RTP) complements the UDP. It is used for real-time applications (e.g. voice or video). The obtained data structure constitutes a segment;

the network layer (layer 3): the Internet model defines two versions of the IP, IPv4 and IPv6. The network layer allows data to be transferred across the network. The information used is the destination IP address. The network nodes that perform such a transfer are the routers. The network layer therefore fulfils the connection function. IP operates in a non-connected mode: the data transfer is not conditional upon the implementation of a path between the two endpoints. The obtained data structure constitutes a packet.

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