Designing Switch/Routers

351 Pages·2023·8.126 MB·English

Designing Switch/Routers
This book examines the fundamental concepts and design methods associated with
switch/routers. It discusses the main factors that are driving the changing network
landscape and propelling the continuous growth in demand for bandwidth and high-
performance network devices. Designing Switch/Routers: Fundamental Concepts
and Design Methods focuses on the essential concepts that underlie the design of
switch/routers in general.
This book considers the switch/router as a generic Layer 2 and Layer 3 forward-
ing device without placing an emphasis on any particular manufacturer’s device. The
underlying concepts and design methods are not only positioned to be applicable to
generic switch/routers but also to the typical switch/routers seen in the industry. The
discussion provides a better insight into the protocols, methods, processes, and tools
involved in designing switch/routers. The author discusses the design goals and fea-
tures switch/router manufacturers consider when designing their products as well as
the advanced and value-added features, along with the steps, used to build practical
switch/routers. The last two chapters discuss real-world 6 switch/router architectures
that employ the concepts and design methods described in the previous chapters.
This book provides an introductory level discussion of switch/routers and is writ-
ten in a style accessible to undergraduate and graduate students, engineers, and
researchers in the networking and telecoms industry as well as academics and other
industry professionals. The material and discussion are structured to serve as stand-
alone teaching material for networking and telecom courses and/or supplementary
material for such courses.

Designing Switch/Routers
Fundamental Concepts and Design Methods
James Aweya
First edition published 2023
by CRC Press
6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742
and by CRC Press
4 Park Square, Milton Park, Abingdon, Oxon, OX14 4RN
CRC Press is an imprint of Taylor & Francis Group, LLC
© 2023 James Aweya
Reasonable efforts have been made to publish reliable data and information, but the author and publisher
cannot assume responsibility for the validity of all materials or the consequences of their use. The authors
and publishers have attempted to trace the copyright holders of all material reproduced in this publication
and apologize to copyright holders if permission to publish in this form has not been obtained. If any
copyright material has not been acknowledged please write and let us know so we may rectify in any
future reprint.
Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced,
transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter
invented, including photocopying, microfilming, and recording, or in any information storage or retrieval
system, without written permission from the publishers.
For permission to photocopy or use material electronically from this work, access www.copyright.com
or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923,
978-750-8400. For works that are not available on CCC please contact mpkbookspermissions@tandf.
co.uk
Trademark notice: Product or corporate names may be trademarks or registered trademarks and are used
only for identification and explanation without intent to infringe.
ISBN: 978-1-032-31769-4 (hbk)
ISBN: 978-1-032-31582-9 (pbk)
ISBN: 978-1-003-31124-9 (ebk)
DOI: 10.1201/9781003311249
Typeset in Times
by SPi Technologies India Pvt Ltd (Straive)
Contents
Preface .....................................................................................................................xiii
Author ....................................................................................................................xvii
Chapter 1 The Era of High-Performance Networks ..............................................1
1.1 Introduction ...............................................................................1
1.2 Introduction to IP Routing .........................................................1
1.3 Characteristics of Enterprise and Service Provider
Networks ....................................................................................2
1.3.1 Characteristics of Enterprise Networks ........................2
1.3.2 Characteristics of Service Provider Networks ..............3
1.4 Understanding the Evolution to High-Performance
Networks ....................................................................................4
1.5 Introduction to Multilayer Switching and
the Switch/Router ......................................................................7
1.5.1 The Switch/Router as Merging the Best of Layer 2
Switching and IP Routing ............................................8
1.5.2 The Switch/Router as Reducing the Complexity of
Three-Tier Networking .................................................9
1.5.3 Layer 2/Layer 3 Convergence
on a Single Platform ...................................................11
Review Questions ...............................................................................12
References ..........................................................................................12
Chapter 2 Introducing Multilayer Switching and the Switch/Router .................13
2.1 Introduction .............................................................................13
2.2 Key Terminology and Definitions ............................................13
2.3 Routing Metric and Administrative Distance
(or Route Preference) ..............................................................19
2.4 Evolution of the Switch/Router ...............................................21
2.5 First-Generation Routing Devices ...........................................21
2.6 Second-Generation Routing Devices .......................................23
2.7 Third-Generation Routing Devices .........................................25
2.8 Fourth (Current) Generation Routing Devices ........................27
Review Questions ...............................................................................30
References ..........................................................................................31
Chapter 3 OSI and TCP/IP Reference Models ....................................................33
3.1 Introduction .............................................................................33
3.2 Development of Network Reference Models ..........................33
v
vi Contents
3.3 OSI Reference Model ..............................................................34
3.3.1 OSI Physical Layer .....................................................37
3.3.2 OSI Data Link Layer ..................................................38
3.3.3 OSI Network Layer ....................................................39
3.3.4 OSI Transport Layer ...................................................39
3.3.5 OSI Session Layer ......................................................41
3.3.6 OSI Presentation Layer ..............................................41
3.3.7 OSI Application Layer................................................41
3.4 TCP/IP Reference Model ........................................................42
3.4.1 TCP/IP Link Layer .....................................................43
3.4.2 TCP/IP Network Layer ...............................................45
3.4.3 TCP/IP Transport Layer .............................................46
3.4.4 TCP/IP Application Layer ..........................................48
Review Questions ...............................................................................51
References ..........................................................................................51
Chapter 4 Mapping Network Device Functions to the OSI
Reference Model ................................................................................53
4.1 Introduction .............................................................................53
4.2 Repeater and the OSI Model ...................................................53
4.3 Bridge (or Switch) and the OSI Model ....................................55
4.3.1 Bridge Logical Reference Model ...............................55
4.3.2 MAC Relay Entity ......................................................58
4.3.3 Filtering Database (MAC Address Table or
Layer 2 Forwarding Table) .........................................61
4.3.3.1 Contents of the Filtering Database .............61
4.3.3.2 Using a Content Addressable Memory
for the Filtering Database ...........................63
4.3.3.3 Aging Out Dynamic Filtering Entries .........63
4.3.4 Overview of IEEE 802.1D Transparent Bridging
Algorithm ...................................................................65
4.3.5 Special Focus: Ethernet MAC Address Format ..........66
4.3.5.1 Organizational Unique Identifier and
NIC-Specific Identifier ................................67
4.3.5.2 Individual/Group Address Bit .....................68
4.3.5.3 Universally/Locally Administered
Address Bit .................................................69
4.3.6 VLANs – A Mechanism for Limiting Broadcast
Traffic .........................................................................69
4.4 Router and the OSI Model .......................................................71
4.5 Multilayer Switching and the OSI Model: Integrated
Layer 2 Switching and Layer 3 Routing ..................................72
4.6 Layer 4-7 Switching – Going beyond Multilayer
Switching (Layer 2/3) ..............................................................76
Contents vii
4.6.1 Benefits of Layer 4+ Switching – Higher
Infrastructure Return-on-Investment ..........................78
4.6.2 Architecture and Configuration of Layer 4+
Switching ....................................................................79
4.6.3 Capabilities and Applications of Layer 4+
Switching ....................................................................80
4.7 Generic IP Host Architecture ...................................................83
4.7.1 Types of NICs .............................................................84
4.7.2 High-Level NIC Architecture .....................................87
4.8 Configuring MAC Addresses in Ethernet NICs.......................88
Review Questions ...............................................................................90
References ..........................................................................................91
Chapter 5 Review of Layer 2 and Layer 3 Forwarding .......................................93
5.1 Introduction .............................................................................93
5.2 Deciding When to Use Layer 2 or Layer 3 Forwarding
for an Arriving Packet ..............................................................93
5.3 Layer 2 Forwarding .................................................................95
5.3.1 Layer 2 Forwarding Basics .........................................95
5.3.2 Lookup Tables Used in Layer 2 Forwarding
Operations ..................................................................97
5.4 Internetworking Basics ..........................................................101
5.4.1 Bridging (Switching) in Internetworks .....................101
5.4.2 Routing in Internetworks ..........................................102
5.4.3 Switching within a Subnet ........................................104
5.4.4 Routing between Subnets .........................................104
5.5 Control Plane and Data Plane in the Router or
Switch/Router ........................................................................106
5.5.1 Control Plane ............................................................106
5.5.1.1 Basic Control Plane Operations ................108
5.5.1.2 Routing Table or Routing Information
Base ...........................................................108
5.5.1.3 Forwarding Table or Forwarding
Information Base ......................................122
5.5.2 Data Plane.................................................................123
5.5.2.1 Basic Data Plane Operations ....................124
5.5.2.2 Unicast Reverse Path Forwarding .............137
5.5.2.3 Multicast Reverse Path Forwarding ..........138
5.5.3 Examining the Benefits of Control Plane and
Data Plane Separation ..............................................140
5.5.3.1 Scalability and Distributed Forwarding
Architectures .............................................140
5.5.3.2 Control Plane Redundancy and Fault
Tolerance ...................................................143
5.5.4 Lookup Tables Used in Layer 3/4 Forwarding
Operations, QoS, and Security ACLs .......................144
viii Contents
5.6 Special Focus: Control Plane Management Subsystems .......150
5.6.1 Simple Network Management Protocol ...................151
5.6.2 Remote Network Monitoring ...................................154
5.6.3 Device GUIs and MIB Browsers ..............................160
Review Questions .............................................................................161
References ........................................................................................162
Chapter 6 Packet Forwarding in the Switch/Router: Layer 3
Forwarding Architectures .................................................................165
6.1 Introduction ...........................................................................165
6.2 Packet Forwarding in the Router or Switch/Router ...............165
6.3 Packet Forwarding Architectures ...........................................168
6.3.1 Traditional Centralized CPU-Based Forwarding
Architectures: Software-Based Forwarding
Using the IP Routing Table ......................................169
6.3.1.1 Packet Forwarding in the Traditional
CPU-Based Forwarding Architectures
Using the IP Routing Table .......................171
6.3.1.2 Limitations of the Traditional CPU-
Based Forwarding Architectures ...............175
6.3.1.3 Types of Centralized Forwarding
Architectures Using the IP Routing
Table ..........................................................176
6.3.2 Forwarding Architectures Using Route Caches .......192
6.3.2.1 Temporal and Spatial Locality of IP
Traffic Flows ............................................194
6.3.2.2 Handling Exception Packets .....................196
6.3.2.3 Route Cache Performance ........................196
6.3.2.4 Implementing Architectures with
Route Caches ............................................197
6.3.2.5 Route Cache Maintenance and Timers .....206
6.3.2.6 Exact Matching in IP Route Caches .........207
6.3.3 Architectures Using Topology-Based
Forwarding Tables ....................................................208
6.3.3.1 Implementing Architectures with
Topology-Derived Forwarding Tables ......210
6.4 Routing between VLANs ......................................................225
6.4.1 What Is a VLAN? .....................................................225
6.4.2 IEEE 801.1Q ............................................................226
6.4.3 Inter-VLAN Routing ................................................229
6.4.4 Implementing Inter-VLAN Routing .........................230
6.4.4.1 Using an External Router ..........................230
6.4.4.2 Using a One-Armed Router ......................230
6.4.4.3 Using a Switch/Router ..............................233
Review Questions .............................................................................237
References ........................................................................................238
Contents ix
Chapter 7 Review of Multilayer Switching Methods:
Switch/Router Internals ....................................................................241
7.1 Introduction ...........................................................................241
7.2 Multilayer Switching Methods ..............................................241
7.3 Understanding the Front-End Processor Approach with
Flow-Based Multilayer Switching .........................................243
7.3.1 Basic Architecture ....................................................243
7.3.2 Flow-Based Multilayer Switching Packet
Processing Steps .......................................................246
7.3.3 Multilayer Switching Using a Route Cache and
Access Control Lists .................................................249
7.3.4 Multilayer Switching Cache Timers .........................251
7.3.5 MLS-RP to MLS-SE Communications ....................252
7.4 IP Multicast Multilayer Switching ........................................253
7.4.1 Unicast Multilayer Switching in Cisco Catalyst
5000, 6000, and 6500 Series Switches .....................254
7.4.2 Understanding IP Multicast Multilayer
Switching ..................................................................256
7.4.2.1 IP Multicast Multilayer Switching
Network Topology ....................................256
7.4.2.2 Cisco IP Multicast MLS Components ......257
7.4.2.3 Layer 3 Multicast Multilayer Switching
Cache ........................................................258
7.4.2.4 Layer 3-Switched Multicast Packet
Rewrite ......................................................259
7.5 The FIB, Fast-Path Forwarding, and Distributed
Forwarding Architectures ......................................................261
7.5.1 Benefits of Distributed Forwarding ..........................262
7.5.2 Distributed Forwarding Architecture ........................262
7.5.3 Distributed Forwarding with Integrated
Hardware Processing ................................................265
7.5.4 Benefits of Multilayer Switching
with Integrated Hardware Processing .......................267
Review Questions .............................................................................267
References ........................................................................................268
Chapter 8 Quality of Service in Switch/Routers ...............................................269
8.1 Introduction ...........................................................................269
8.2 Network Requirements for Real-Time Traffic Transport ......270
8.2.1 Adequate Bandwidth ................................................270
8.2.2 Network Elements with Non-blocking and
Improved Switching and Forwarding
Performance..............................................................270
8.2.3 End-to-End QoS .......................................................271