Load Balancer Guide

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WebSphere Application Server

Load Balancer Administration Guide

Version 6.1

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WebSphere Application Server

Load Balancer Administration Guide

Version 6.1

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NoteBefore using this information and the product it supports, be sure to read the general information under Appendix E,Notices, on page 457.

First edition (May 2006)

This edition applies to:WebSphere Application Server, Version 6.1

and to all subsequent releases and modifications until otherwise indicated in new editions.

Order publications through your IBM representative or through the IBM branch office serving your locality.

Copyright International Business Machines Corporation 2006.US Government Users Restricted Rights Use, duplication or disclosure restricted by GSA ADP Schedule Contractwith IBM Corp.


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Contents

Tables . . . . . . . . . . . . . . . xi

Figures . . . . . . . . . . . . . . xiii

About this book. . . . . . . . . . . xvWho should read this book . . . . . . . . . xvReference Information . . . . . . . . . . . xvAccessibility . . . . . . . . . . . . . . xvHow to send your comments . . . . . . . . xv

Related documents and Web sites xvii

Part 1. Introduction to Load Balancer 1

Chapter 1. Overview of Load Balancer. . 3What is Load Balancer? . . . . . . . . . . . 3Which components of Load Balancer can I use?. . . 3What are the advantages to using Load Balancer? . . 4How can Load Balancer provide high availability?. . 5

Dispatcher . . . . . . . . . . . . . . 5CBR . . . . . . . . . . . . . . . . 6Cisco CSS Controller or Nortel Alteon Controller 6

New features . . . . . . . . . . . . . . 6

Chapter 2. Overview of the componentsof Load Balancer . . . . . . . . . . . 9What are the components of Load Balancer?. . . . 9Overview of the Dispatcher component . . . . . 9

Managing local servers with Dispatcher . . . . 10Managing servers using Dispatcher and MetricServer . . . . . . . . . . . . . . . 11Managing local and remote servers withDispatcher . . . . . . . . . . . . . . 11

Overview of the Content Based Routing (CBR)component . . . . . . . . . . . . . . 12

Managing local servers with CBR . . . . . . 12Overview of the Site Selector component . . . . 13

Managing local and remote servers with SiteSelector and Metric Server . . . . . . . . 14

Overview of the Cisco CSS Controller component 14Overview of Nortel Alteon Controller component . 16

Chapter 3. Managing your network:Determining which Load Balancerfeatures to use . . . . . . . . . . . 19Manager, Advisors, and Metric Server functions (forDispatcher, CBR, and Site Selector components) . . 19Dispatcher component features . . . . . . . . 19

Remote administration . . . . . . . . . 19Collocation . . . . . . . . . . . . . 19High availability. . . . . . . . . . . . 19Client to server affinity . . . . . . . . . 20Rules-based load balancing . . . . . . . . 20

Content-based routing using Dispatchers cbrforwarding method . . . . . . . . . . . 21

Wide area load balancing . . . . . . . . . 21Port mapping. . . . . . . . . . . . . 22Setting up Dispatcher on a private network . . 22Wildcard cluster and wildcard port . . . . . 22Denial of service attack detection . . . . . 22Binary logging . . . . . . . . . . . . 22Alerts . . . . . . . . . . . . . . . 22

Content Based Routing (CBR) component features 22Comparison between the CBR component andthe Dispatcher components cbr forwardingmethod . . . . . . . . . . . . . . . 23Remote administration . . . . . . . . . 23Collocation . . . . . . . . . . . . . 23CBR with multiple instances of Caching Proxy . 23

Provide content-based routing for SSLconnections . . . . . . . . . . . . . 23Server partitioning . . . . . . . . . . . 23Rules-based load balancing . . . . . . . . 24Client to server affinity . . . . . . . . . 24High availability using Dispatcher and CBR . . 24Binary logging . . . . . . . . . . . . 24Alerts . . . . . . . . . . . . . . . 24

Site Selector component features . . . . . . . 25Remote administration . . . . . . . . . 25Collocation . . . . . . . . . . . . . 25High availability. . . . . . . . . . . . 25Client to server affinity . . . . . . . . . 25Rules-based load balancing . . . . . . . . 25

Wide area load balancing . . . . . . . . . 25Alerts . . . . . . . . . . . . . . . 26

Cisco CSS Controller component features . . . . 26Remote administration . . . . . . . . . 26Collocation . . . . . . . . . . . . . 26High availability. . . . . . . . . . . . 26Binary logging . . . . . . . . . . . . 26Alerts . . . . . . . . . . . . . . . 26

Nortel Alteon Controller component features . . . 27Remote administration . . . . . . . . . 27Collocation . . . . . . . . . . . . . 27High availability. . . . . . . . . . . . 27Binary logging . . . . . . . . . . . . 27Alerts . . . . . . . . . . . . . . . 27

Chapter 4. Installing Load Balancer . . 29AIX system requirements and installation . . . . 29

Requirements for AIX systems . . . . . . . 29Installing for AIX systems . . . . . . . . 29Before you install . . . . . . . . . . . 30Installation steps. . . . . . . . . . . . 31

HP-UX system requirements and installation . . . 33Requirements for HP-UX systems . . . . . . 33Installing for HP-UX systems . . . . . . . 33Before you install . . . . . . . . . . . 33

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Configuring with the graphical user interface(GUI) . . . . . . . . . . . . . . . 93Configuring with the configuration wizard . . . 94

Types of cluster, port, server configurations. . . . 94

Chapter 10. Planning for ContentBased Routing . . . . . . . . . . . 97

Planning considerations . . . . . . . . . . 97Load balancing requests for different types ofcontent . . . . . . . . . . . . . . . 98Dividing your site content for better responsetime . . . . . . . . . . . . . . . . 98Providing backup of Web server content. . . . 98Using multiple Caching Proxy processes toimprove CPU utilization . . . . . . . . . 98Using rules-based load balancing with CBR . . 99Load balancing across fully secure (SSL)connections . . . . . . . . . . . . . 99Load balancing client-to-proxy in SSL andproxy-to-server in HTTP . . . . . . . . . 99

Chapter 11. Configuring ContentBased Routing . . . . . . . . . . . 101Overview of configuration tasks . . . . . . . 101Methods of configuration . . . . . . . . . 101

Command line . . . . . . . . . . . . 102Scripts. . . . . . . . . . . . . . . 103GUI . . . . . . . . . . . . . . . 103Configuration wizard. . . . . . . . . . 104

Setting up the CBR machine . . . . . . . . 105Step 1. Configure Caching Proxy to use CBR 105Step 2. Start the server function . . . . . . 106Step 3. Start the executor function . . . . . 107Step 4. Define a cluster and set cluster options 107Step 5. Alias the network interface card(optional). . . . . . . . . . . . . . 107Step 6. Define ports and set port options . . . 108Step 7. Define load balanced server machines 108Step 8. Add rules to your configuration . . . 108Step 9. Add servers to your rules. . . . . . 109Step 10. Start the manager function (optional) 109Step 11. Start the advisor function (optional) . . 109Step 12. Set cluster proportions as required . . 109Step 13. Start Caching Proxy . . . . . . . 109

CBR configuration example . . . . . . . . . 110

Part 4. Site Selector component 111

Chapter 12. Quick start configuration 113What do you need? . . . . . . . . . . . 113How do you prepare? . . . . . . . . . . 113Configuring the Site Selector component . . . . 114

Configuring with the command line. . . . . 114Testing your configuration . . . . . . . . 115Configuring with the graphical user interface(GUI) . . . . . . . . . . . . . . . 115Configuring with the configuration wizard . . 115

Chapter 13. Planning for Site Selector 117

Planning Considerations . . . . . . . . . . 117TTL considerations . . . . . . . . . . 119Using the Network Proximity feature . . . . 119

Chapter 14. Configuring Site Selector 121Overview of configuration tasks . . . . . . . 121Methods of configuration . . . . . . . . . 121

Command line . . . . . . . . . . . . 121Scripts. . . . . . . . . . . . . . . 122GUI . . . . . . . . . . . . . . . 122Configuration wizard. . . . . . . . . . 123

Setting up the Site Selector machine. . . . . . 124Step 1. Start the server function . . . . . . 124Step 2. Start the Name Server . . . . . . . 124Step 3. Define a site name and set site nameoptions . . . . . . . . . . . . . . 124Step 4. Define load balanced server machines 124Step 5. Start the manager function (optional) 125Step 6. Start the advisor function (optional) . . 125Step 7. Define system metric (optional) . . . . 125Step 8. Set site name proportions as required 125

Setting up server machines for load balancing . . 125

Part 5. Cisco CSS Controllercomponent . . . . . . . . . . . . 127

Chapter 15. Quick start configuration 129What do you need? . . . . . . . . . . . 129How do you prepare? . . . . . . . . . . 129Configuring the Cisco CSS Controller component 130

Configuring with the command line. . . . . 130Testing your configuration . . . . . . . . 130Configuring with the graphical user interface(GUI) . . . . . . . . . . . . . . . 131

Chapter 16. Planning for Cisco CSSController . . . . . . . . . . . . . 133System requirements . . . . . . . . . . . 133Planning considerations . . . . . . . . . . 133

Placement of the consultant in the network . . 134High availability . . . . . . . . . . . 136Calculating weights . . . . . . . . . . 136Problem determination . . . . . . . . . 137

Chapter 17. Configuring Cisco CSSController . . . . . . . . . . . . . 139Overview of configuration tasks . . . . . . . 139

Methods of configuration . . . . . . . . . 139Command line . . . . . . . . . . . . 139XML . . . . . . . . . . . . . . . 140GUI . . . . . . . . . . . . . . . 141

Setting up the Controller for Cisco CSS Switchesmachine . . . . . . . . . . . . . . . 142

Step 1. Start the server function . . . . . . 142Step 2. Start the command line interface . . . 142Step 3. Configure the consultant . . . . . . 142Step 3. Configure an ownercontent . . . . . 142Step 4. Verify that services are correctly defined 142Step 5. Configure metrics . . . . . . . . 142

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Step 6. Start the consultant . . . . . . . . 143Step 7. Start the Metric Server (optional) . . . 143Step 8. Configure high availability (optional) 143

Testing your configuration . . . . . . . . . 143

Part 6. Nortel Alteon Controllercomponent . . . . . . . . . . . . 145

Chapter 18. Quick start configuration 147What do you need? . . . . . . . . . . . 147How do you prepare? . . . . . . . . . . 148Configuring the Nortel Alteon Controllercomponent . . . . . . . . . . . . . . 148

Configuring with the command line. . . . . 148Testing your configuration . . . . . . . . 149Configuring with the graphical user interface(GUI) . . . . . . . . . . . . . . . 149

Chapter 19. Planning for Nortel AlteonController . . . . . . . . . . . . . 151

System requirements . . . . . . . . . . . 151Planning considerations . . . . . . . . . . 151

Placement of the consultant in the network . . 152Server attributes on the switch (set by thecontroller) . . . . . . . . . . . . . 154Configuring backup servers . . . . . . . 154Configuring groups . . . . . . . . . . 155High availability . . . . . . . . . . . 156Tuning . . . . . . . . . . . . . . 157Problem determination . . . . . . . . . 158

Chapter 20. Configuring Nortel AlteonController . . . . . . . . . . . . . 159

Overview of configuration tasks . . . . . . . 159Methods of configuration . . . . . . . . . 159Command line . . . . . . . . . . . . 159XML . . . . . . . . . . . . . . . 160GUI . . . . . . . . . . . . . . . 160

Setting up Nortel Alteon Controller . . . . . . 161Step 1. Start the server function . . . . . . 162Step 2. Start the command line interface . . . 162Step 3. Define a Nortel Alteon Web Switchconsultant . . . . . . . . . . . . . 162Step 4. Add a service to the switch consultant 162Step 5. Configure metrics . . . . . . . . 162Step 6. Start the consultant . . . . . . . . 163Step 7. Configure high availability (optional) 163

Step 8. Start the Metric Server (optional) . . . 163Step 9. Refreshing the Nortel Alteon Controllerconfiguration . . . . . . . . . . . . 163

Testing your configuration . . . . . . . . . 163

Part 7. Functions and advancedfeatures for Load Balancer . . . . 165

Chapter 21. Manager, Advisors, andMetric Server functions forDispatcher, CBR, and Site Selector . . 167

Optimizing the load balancing provided by LoadBalancer . . . . . . . . . . . . . . . 168

Proportion of importance given to statusinformation . . . . . . . . . . . . . 168Weights . . . . . . . . . . . . . . 169Manager intervals . . . . . . . . . . . 170Sensitivity threshold . . . . . . . . . . 171Smoothing index . . . . . . . . . . . 171Using scripts to generate an alert or recordserver failure . . . . . . . . . . . . 171

Advisors . . . . . . . . . . . . . . . 172How advisors work . . . . . . . . . . 173Starting and stopping an advisor . . . . . . 173Advisor intervals . . . . . . . . . . . 174Advisor report timeout . . . . . . . . . 174Advisor connect timeout and receive timeout forservers . . . . . . . . . . . . . . 175Advisor retry . . . . . . . . . . . . 175List of advisors . . . . . . . . . . . . 175Configuring the HTTP or HTTPS advisor usingthe request and response (URL) option . . . . 177Using Self Advisor in a two-tiered WANconfiguration . . . . . . . . . . . . 178

Create custom (customizable) advisors . . . . . 179WAS advisor . . . . . . . . . . . . 180Naming Convention . . . . . . . . . . 180Compilation . . . . . . . . . . . . . 180Run . . . . . . . . . . . . . . . 181Required routines . . . . . . . . . . . 181Search order. . . . . . . . . . . . . 181Naming and path . . . . . . . . . . . 182Sample advisor . . . . . . . . . . . . 182

Metric Server . . . . . . . . . . . . . 182WLM Restriction . . . . . . . . . . . 182Prerequisites. . . . . . . . . . . . . 182

How to Use Metric Server . . . . . . . . 182Workload Manager advisor . . . . . . . . . 184Metric Server Restriction . . . . . . . . 185

Chapter 22. Advanced features forDispatcher, CBR, and Site Selector . . 187Using collocated servers . . . . . . . . . . 188

For the Dispatcher component. . . . . . . 188For the CBR component . . . . . . . . . 190For the Site Selector component . . . . . . 190

High availability . . . . . . . . . . . . 190Configure high availability . . . . . . . . 191Failure detection capability using heartbeat andreach target . . . . . . . . . . . . . 193

Recovery Strategy . . . . . . . . . . . 193Using scripts . . . . . . . . . . . . 194Configure both collocation and high availability(Windows systems) . . . . . . . . . . 196

Configure rules-based load balancing . . . . . 197How are rules evaluated? . . . . . . . . 198Using rules based on the client IP address. . . 198Using rules based on the client port . . . . . 198Using rules based on the time of day . . . . 199Using rules based on type of service (TOS) . . 199Using rules based on the connections persecond . . . . . . . . . . . . . . 199

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Using rules based on the total activeconnections . . . . . . . . . . . . . 200Using rules based on reserved bandwidth andshared bandwidth . . . . . . . . . . . 200Metric all rule . . . . . . . . . . . . 202Metric average rule . . . . . . . . . . 202Using rules that are always true . . . . . . 202Using rules based on the request content . . . 203port affinity override . . . . . . . . . . 203Adding rules to your configuration . . . . . 203Server evaluation option for rules . . . . . 204

How affinity feature for Load Balancer works . . 205Behavior when affinity is disabled . . . . . 205Behavior when affinity is enabled . . . . . 205Cross port affinity . . . . . . . . . . . 206Affinity address mask (stickymask) . . . . . 206Quiesce server connection handling . . . . . 207

Affinity option on the rule based on the content ofthe client request . . . . . . . . . . . . 208

Active cookie affinity . . . . . . . . . . 208Passive cookie affinity . . . . . . . . . 210URI affinity . . . . . . . . . . . . . 211

Configure wide area Dispatcher support . . . . 211Command Syntax . . . . . . . . . . . 212Using remote advisors with Dispatchers widearea support. . . . . . . . . . . . . 213Configuration example . . . . . . . . . 215GRE (Generic Routing Encapsulation) support 217

Using explicit linking. . . . . . . . . . . 218Using a private network configuration . . . . . 218Use wildcard cluster to combine serverconfigurations . . . . . . . . . . . . . 219Use wildcard cluster to load balance firewalls . . 219Use wildcard cluster with Caching Proxy fortransparent proxy . . . . . . . . . . . . 220

Use wildcard port to direct unconfigured porttraffic . . . . . . . . . . . . . . . . 220Wildcard port to handle FTP traffic . . . . . 221

Denial of service attack detection. . . . . . . 221Using binary logging to analyze server statistics 222Using a collocated client . . . . . . . . . . 223

Chapter 23. Advanced features forCisco CSS Controller and NortelAlteon Controller . . . . . . . . . . 225Collocation . . . . . . . . . . . . . . 225High availability . . . . . . . . . . . . 225

Configuration . . . . . . . . . . . . 226Failure detection . . . . . . . . . . . 227

Recovery strategy . . . . . . . . . . . 227Examples. . . . . . . . . . . . . . 227

Optimizing the load balancing provided by LoadBalancer . . . . . . . . . . . . . . . 228

Importance given to metric information . . . 228Weights . . . . . . . . . . . . . . 228Weight calculation sleeptimes . . . . . . . 229Sensitivity threshold . . . . . . . . . . 229

Advisors . . . . . . . . . . . . . . . 229How advisors work . . . . . . . . . . 230Advisor sleeptimes . . . . . . . . . . 230

Advisor connect timeout and receive timeout forservers . . . . . . . . . . . . . . 230Advisor retry . . . . . . . . . . . . 231

Create custom (customizable) advisors . . . . . 231Naming Convention . . . . . . . . . . 232Compilation . . . . . . . . . . . . . 232Run . . . . . . . . . . . . . . . 233Required routines . . . . . . . . . . . 233Search order. . . . . . . . . . . . . 234Naming and path . . . . . . . . . . . 234Sample advisor . . . . . . . . . . . . 234

Metric Server . . . . . . . . . . . . . 234Prerequisites. . . . . . . . . . . . . 234How to Use Metric Server . . . . . . . . 234

Workload manager advisor . . . . . . . . . 236Using binary logging to analyze server statistics 236Using scripts to generate an alert or record serverfailure . . . . . . . . . . . . . . . . 238

Part 8. Administering andtroubleshooting Load Balancer . . 239

Chapter 24. Operating and managingLoad Balancer . . . . . . . . . . . 241Remote administration of Load Balancer . . . . 241

Remote Method Invocation (RMI) . . . . . 242Web-based administration . . . . . . . . 243

Using Load Balancer logs . . . . . . . . . 245For Dispatcher, CBR, and Site Selector . . . . 245For Cisco CSS Controller and Nortel AlteonController . . . . . . . . . . . . . 246

Using the Dispatcher component . . . . . . . 247Starting and Stopping Dispatcher. . . . . . 247Using stale timeout value . . . . . . . . 247

Using fintimeout and staletimeout to controlcleanup of connection records . . . . . . . 248Reporting GUI the Monitor menu option . . 248Using Simple Network Management Protocolwith the Dispatcher component . . . . . . 248Using ipchains or iptables to reject all traffic toharden the Load Balancer machine (Linuxsystems) . . . . . . . . . . . . . . 255

Using the Content Based Routing component. . . 255Starting and Stopping CBR . . . . . . . . 256Controlling CBR . . . . . . . . . . . 256Using CBR logs . . . . . . . . . . . 256

Using the Site Selector component . . . . . . 256Starting and stopping Site Selector . . . . . 256

Controlling Site Selector . . . . . . . . . 256Using Site Selector logs . . . . . . . . . 257

Using the Cisco CSS Controller component . . . 257Starting and stopping Cisco CSS Controller . . 257Controlling Cisco CSS Controller . . . . . . 257Using Cisco CSS Controller logs . . . . . . 257

Using the Nortel Alteon Controller component . . 257Starting and stopping Nortel Alteon Controller 257Controlling Nortel Alteon Controller . . . . 257Using Nortel Alteon Controller logs . . . . . 257

Using the Metric Server component . . . . . . 258Starting and stopping Metric Server . . . . . 258

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Using Metric Server logs . . . . . . . . 258

Chapter 25. Troubleshooting . . . . . 259Gathering troubleshooting information . . . . . 259

General information (always required) . . . . 259High availability (HA) problems . . . . . . 260Advisor problems . . . . . . . . . . . 260

Content Based Routing problems. . . . . . 261Not able to hit the cluster . . . . . . . . 262All else fails . . . . . . . . . . . . . 262Upgrades. . . . . . . . . . . . . . 263

Java code . . . . . . . . . . . . . . 263Helpful links . . . . . . . . . . . . 263

Troubleshooting tables . . . . . . . . . . 263Checking Dispatcher port numbers . . . . . . 274Checking CBR port numbers . . . . . . . . 274Checking Site Selector port numbers . . . . . 275Checking Cisco CSS Controller port numbers. . . 276Checking Nortel Alteon Controller port numbers 277Solving common problemsDispatcher . . . . 277

Problem: Dispatcher will not run . . . . . . 277

Problem: Dispatcher and server will not respond 277Problem: Dispatcher requests are not being

balanced . . . . . . . . . . . . . . 277Problem: Dispatcher high-availability function isnot working . . . . . . . . . . . . . 278Problem: Unable to add heartbeat (Windowsplatform) . . . . . . . . . . . . . . 278Problem: Extra routes (Windows 2000) . . . . 278Problem: Advisors not working correctly . . . 279Problem: Dispatcher, Microsoft IIS, and SSL donot work (Windows platform) . . . . . . . 279Problem: Dispatcher connection to a remotemachine . . . . . . . . . . . . . . 279Problem: dscontrol or lbadmin command fails 279

Problem: Cannot find the file...

error messagewhen trying to view online Help (Windowsplatform) . . . . . . . . . . . . . . 280Problem: Graphical user interface (GUI) doesnot start correctly . . . . . . . . . . . 280Problem: Error running Dispatcher withCaching Proxy installed . . . . . . . . . 280Problem: Graphical user interface (GUI) doesnot display correctly . . . . . . . . . . 281Problem: On Windows platform, help windowssometimes disappear behind other openwindows . . . . . . . . . . . . . . 281Problem: Load Balancer cannot process andforward a frame . . . . . . . . . . . 281

Problem: A blue screen displays when you startthe Load Balancer executor. . . . . . . . 281Problem: Path to Discovery prevents returntraffic with Load Balancer . . . . . . . . 281Problem: High availability in the Wide Areamode of Load Balancer does not work . . . . 282Problem: GUI hangs (or unexpected behavior)when trying to load a large configuration file. . 283Problem: lbadmin disconnects from server afterupdating configuration . . . . . . . . . 283Problem: IP addresses not resolving correctlyover the remote connection . . . . . . . . 283

Problem: Korean Load Balancer interfacedisplays overlapping or undesirable fonts onAIX and Linux systems . . . . . . . . . 284Problem: On Windows systems, alias address isreturned instead of local address when issuingcommands such as hostname . . . . . . . 284Problem: On Windows platform, unexpectedGUI behavior when using Matrox AGP videocards . . . . . . . . . . . . . . . 284Problem: Unexpected behavior when executingrmmod ibmlb (Linux systems) . . . . . . 285Problem: Slow response time runningcommands on Dispatcher machine . . . . . 285Problem: SSL or HTTPS advisor not registeringserver loads (when using mac-forwarding) . . 285Problem: Disconnect from host occurs whenresize Netscape browser window while usingWeb administration . . . . . . . . . . 285Problem: Socket pooling is enabled and the Webserver is binding to 0.0.0.0 . . . . . . . . 286Problem: On Windows systems, corruptedLatin-1 national characters appear in commandprompt window . . . . . . . . . . . 286Problem: On HP-UX, Java out of memory/thread error occurs . . . . . . . . . . 286Problem: On Windows systems, advisors andreach targets mark all servers down . . . . . 287Problem: On Windows platform, resolving IPaddress to host name when more than oneaddress is configured to an adapter . . . . . 287Problem: On Windows systems, after networkoutage, advisors not working in a highavailability setup . . . . . . . . . . . 288Problem: On Linux systems, do not use IPaddress add command when aliasing multiple

clusters on the loopback device . . . . . . 289Problem: Router address not specified or notvalid for port method error message . . . . 289Problem: On Solaris systems, Load Balancerprocesses end when you exit the terminalwindow from which they started. . . . . . 290Problem: Delay occurs while loading a LoadBalancer configuration . . . . . . . . . 290Problem: On Windows systems, an IP addressconflict error message appears. . . . . . . 290Problem: Both primary and backup machinesare active in a high availability configuration. . 290Problem: Client requests fail when attemptingthe return of large page responses . . . . . 291

Problem: On Windows systems,

Server notresponding error occurs when issuing dscontrolor lbadmin . . . . . . . . . . . . . 291Problem: High availability Dispatcher machinesmay fail to synchronize on Linux for S/390systems on qeth drivers . . . . . . . . . 291Problem: Tips on configuring high availability 292Problem: On Linux, Dispatcher configurationlimitations when using zSeries or S/390 serversthat have Open System Adapter (OSA) cards. . 293

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Problem: On some Linux versions, a memoryleak occurs when running Dispatcherconfigured with the manager and advisors . . 295Problem: On SUSE Linux Enterprise Server 9,Dispatcher forwards packets, but the packets donot reach the backend server . . . . . . . 296Problem: On Windows system, IP addressconflict message appears during highavailability takeover . . . . . . . . . . 296Problem: Linux iptables can interfere with therouting of packets . . . . . . . . . . . 297Problem: Unable to add an IPv6 server to theLoad Balancer configuration on Solaris systems . 297

Java warning message appears when installingservice fixes . . . . . . . . . . . . . 298Upgrading the Java file set provided with theLoad Balancer installation . . . . . . . . 298

Solving common problemsCBR. . . . . . . 298Problem: CBR will not run . . . . . . . . 298Problem: cbrcontrol or lbadmin command fails 298Problem: Requests not being load balanced . . 299Problem: On Solaris systems, cbrcontrolexecutor start command fails . . . . . . . 299Problem: Syntactical or configuration error . . 299Problem: On Windows platform, unexpectedGUI behavior when using Matrox AGP videocards . . . . . . . . . . . . . . . 299Problem: Disconnect from host occurs whenresize Netscape browser window while usingWeb administration . . . . . . . . . . 300Problem: On Windows platform, corruptedLatin-1 national characters appear in commandprompt window . . . . . . . . . . . 300Problem: On HP-UX, Java out of memory/thread error occurs . . . . . . . . . . 300

Problem: On Windows systems, advisors andreach targets mark all servers down . . . . . 300Problem: On Windows systems, resolving IPaddress to host name when more than oneaddress is configured to an adapter . . . . . 300

Solving common problemsSite Selector . . . . 301Problem: Site Selector will not run . . . . . 301Problem: Site Selector does not round-robintraffic from Solaris clients . . . . . . . . 301Problem: sscontrol or lbadmin command fails 301Problem: The ssserver is failing to start onWindows platform . . . . . . . . . . 301Problem: Site Selector with duplicate routes notload balancing correctly . . . . . . . . . 302

Problem: On Windows platform, unexpectedGUI behavior when using Matrox AGP videocards . . . . . . . . . . . . . . . 302Problem: Disconnect from host occurs whenresize Netscape browser window while usingWeb administration . . . . . . . . . . 302Problem: On Windows platform, corruptedLatin-1 national characters appear in commandprompt window . . . . . . . . . . . 302Problem: On HP-UX, Java out of memory/thread error occurs . . . . . . . . . . 302

Problem: On Windows systems, advisors andreach targets mark all servers down . . . . . 303

Solving common problemsCisco CSS Controller 303Problem: ccoserver will not start . . . . . . 303Problem: ccocontrol or lbadmin command fails 303Problem: Cannot create registry on port 13099 303Problem: On Windows platform, unexpectedGUI behavior when using Matrox AGP videocards . . . . . . . . . . . . . . . 304Problem: Received a connection error whenadding a consultant . . . . . . . . . . 304Problem: Weights are not being updated on theswitch . . . . . . . . . . . . . . . 304Problem: Refresh command did not update theconsultant configuration . . . . . . . . . 304Problem: Disconnect from host occurs whenresize Netscape browser window while usingWeb administration . . . . . . . . . . 304Problem: On Windows platform, corruptedLatin-1 national characters appear in commandprompt window . . . . . . . . . . . 305Problem: On HP-UX, Java out of memory/thread error occurs . . . . . . . . . . 305

Solving common problemsNortel AlteonController . . . . . . . . . . . . . . 305

Problem: nalserver will not start . . . . . . 305Problem: nalcontrol or lbadmin command fails 305Problem: Cannot create registry on port 14099 306Problem: On Windows platform, unexpectedGUI behavior when using Matrox AGP videocards . . . . . . . . . . . . . . . 306Problem: Disconnect from host occurs whenresize Netscape browser window while usingWeb administration . . . . . . . . . . 306Problem: Received a connection error when

adding a consultant . . . . . . . . . . 306Problem: Weights are not being updated on theswitch . . . . . . . . . . . . . . . 307Problem: Refresh command did not update theconsultant configuration . . . . . . . . . 307Problem: On Windows systems, corruptedLatin-1 national characters appear in commandprompt window . . . . . . . . . . . 307Problem: On HP-UX, Java out of memory/thread error occurs . . . . . . . . . . 307

Solving common problemsMetric Server . . . 307Problem: Metric Server IOException onWindows platform running .bat or .cmd usermetric files . . . . . . . . . . . . . 307

Problem: Metric Server not reporting loads toLoad Balancer machine . . . . . . . . . 308Problem: Metric Server log reports Signature isnecessary for access to agent . . . . . . . 308Problem: On AIX systems, while running MetricServer under heavy stress, ps vg commandoutput may become corrupted. . . . . . . 308Problem: Configuring Metric Server in atwo-tier configuration with Site Selectorload-balancing across high-availabilityDispatchers . . . . . . . . . . . . . 308

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Problem: Scripts, running on multi-CPU Solarismachines, produce unwanted console messages . 310Problem: On Load Balancer for IPv6, unable toretrieve values from Metric Server on Linuxsystems . . . . . . . . . . . . . . 310Problem: After starting Metric Server, metricvalue returns -1. . . . . . . . . . . . 311

Part 9. Command Reference. . . . 313

Chapter 26. How to read a syntaxd i a g r a m . . . . . . . . . . . . . . 315Symbols and punctuation . . . . . . . . . 315Parameters . . . . . . . . . . . . . . 315Syntax examples . . . . . . . . . . . . 315

Chapter 27. Command reference forDispatcher and CBR . . . . . . . . 317Configuration differences between CBR andDispatcher . . . . . . . . . . . . . . 318

dscontrol advisor control the advisor . . . . 319dscontrol binlog control the binary log file . . 324dscontrol cluster configure clusters . . . . . 325dscontrol executor control the executor . . . . 329dscontrol file manage configuration files . . . 334dscontrol help display or print help for thiscommand . . . . . . . . . . . . . . 336dscontrol highavailability control highavailability . . . . . . . . . . . . . . 337dscontrol host configure a remote machine . . 341dscontrol logstatus display server log settings 342dscontrol manager control the manager . . . 343dscontrol metric configure system metrics . . . 348dscontrol port configure ports . . . . . . . 349

dscontrol rule configure rules . . . . . . . 354dscontrol server configure servers . . . . . 360dscontrol set configure server log. . . . . . 366dscontrol status display whether the managerand advisors are running . . . . . . . . . 367dscontrol subagent configure SNMP subagent 368

Chapter 28. Command reference forSite Selector . . . . . . . . . . . . 371sscontrol advisor control the advisor . . . . 372sscontrol file manage configuration files . . . 376sscontrol help display or print help for thiscommand . . . . . . . . . . . . . . 378

sscontrol logstatus display server log settings 379sscontrol manager control the manager . . . . 380sscontrol metric configure system metrics . . . 384sscontrol nameserver control the NameServer 385sscontrol rule configure rules . . . . . . . 386sscontrol server configure servers. . . . . . 389sscontrol set configure server log . . . . . . 391sscontrol sitename configure a sitename . . . 392sscontrol status display whether the managerand advisors are running . . . . . . . . . 395

Chapter 29. Command reference forCisco CSS Controller . . . . . . . . 397ccocontrol consultant configure and control aconsultant . . . . . . . . . . . . . . 398ccocontrol controller manage the controller . . 401ccocontrol file manage configuration files . . . 403ccocontrol help display or print help for this

command . . . . . . . . . . . . . . 404ccocontrol highavailability control highavailability . . . . . . . . . . . . . . 405ccocontrol metriccollector configure metriccollector . . . . . . . . . . . . . . . 408ccocontrol ownercontent control the ownername and content rule . . . . . . . . . . 410ccocontrol service configure a service . . . . 413

Chapter 30. Command reference forNortel Alteon Controller . . . . . . . 415nalcontrol consultant configure and control aconsultant . . . . . . . . . . . . . . 416nalcontrol controller manage the controller . . 419nalcontrol file manage configuration files . . . 421nalcontrol help display or print help for thiscommand . . . . . . . . . . . . . . 422nalcontrol highavailability control highavailability . . . . . . . . . . . . . . 423nalcontrol metriccollector configure metriccollector . . . . . . . . . . . . . . . 426nalcontrol server configure a server . . . . . 428nalcontrol service configure a service . . . . 430

Appendix A. GUI: General instructions 433

Appendix B. Content rule (pattern)

syntax . . . . . . . . . . . . . . 439Content rule (pattern) syntax: . . . . . . . . 439

Reserved keywords . . . . . . . . . . 439

Appendix C. Sample configurationfiles . . . . . . . . . . . . . . . 443Sample Load Balancer configuration files . . . . 443

Dispatcher Configuration file AIX, Linux,and Solaris systems . . . . . . . . . . 443Dispatcher Configuration file Windowssystems . . . . . . . . . . . . . . 446Sample advisor . . . . . . . . . . . . 449

Appendix D. Sample of a 2-tier highavailability configuration usingDispatcher, CBR, and Caching Proxy . 453Server machine set up . . . . . . . . . . 453

Appendix E. Notices . . . . . . . . 457Trademarks . . . . . . . . . . . . . . 458

G l o s s a r y . . . . . . . . . . . . . 461

Index . . . . . . . . . . . . . . . 469

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Tables

1. AIX installp images . . . . . . . . . . 302. AIX install commands . . . . . . . . . 31

3. HP-UX package installation details for LoadBalancer. . . . . . . . . . . . . . 334. Configuration tasks for the Dispatcher function 595. Commands to alias the loopback device (lo0)

for Dispatcher. . . . . . . . . . . . 686. Commands to delete any extra route for

Dispatcher . . . . . . . . . . . . . 717. Configuration tasks for the CBR component 1018. Commands to alias the NIC. . . . . . . 1079. Configuration tasks for the Site Selector

component . . . . . . . . . . . . 12110. Configuration tasks for the Cisco CSS

Controller component . . . . . . . . . 139

11. Configuration tasks for the Nortel AlteonController component . . . . . . . . . 159

12. Advanced configuration tasks for LoadBalancer . . . . . . . . . . . . . 16713. Advanced configuration tasks for the Load

Balancer . . . . . . . . . . . . . 18714. Dispatcher troubleshooting table . . . . . 26315. CBR Troubleshooting table . . . . . . . 26816. Site Selector troubleshooting table. . . . . 27017. Controller for Cisco CSS Switches

troubleshooting table . . . . . . . . . 27118. Nortel Alteon Controller troubleshooting table 27219. Metric Server troubleshooting table . . . . 273

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Figures

1. Example of a physical representation of a siteusing Dispatcher to manage local servers . . 10

2. Example of a site using Dispatcher and MetricServer to manage servers . . . . . . . . 113. Example of a site using Dispatcher to manage

local and remote servers . . . . . . . . 114. Example of a site using CBR to manage local

servers . . . . . . . . . . . . . . 135. Example of a site using Site Selector and

Metric Server to manage local and remoteservers . . . . . . . . . . . . . . 14

6. Example of a site using Cisco CSS Controllerand Metric Server to manage local services . . 16

7. Example of a site using Nortel AlteonController to manage local servers . . . . . 17

8. A simple local Dispatcher configuration 43

9. Example of Dispatcher configured with asingle cluster and 2 ports . . . . . . . . 46

10. Example of Dispatcher configured with twoclusters, each with one port . . . . . . . 47

11. Example of Dispatcher configured with 2clusters, each with 2 ports. . . . . . . . 48

12. Example for using Dispatchers nat or cbrforwarding methods . . . . . . . . . 54

13. Example of a Dispatcher using simple highavailability . . . . . . . . . . . . . 57

14. Example of a Dispatcher using mutual highavailability . . . . . . . . . . . . . 58

15. Example of the IP addresses needed for theDispatcher machine . . . . . . . . . . 63

16. A simple local CBR configuration . . . . . 9117. Example of CBR configured with a single

cluster and 2 ports . . . . . . . . . . 9418. Example of CBR configured with two clusters,

each with one port . . . . . . . . . . 9519. Example of CBR configured with 2 clusters,

each with 2 ports . . . . . . . . . . 9620. CBR configuration file for AIX, Linux, and

Solaris systems . . . . . . . . . . . 10621. CBR configuration file for HP-UX systems 10622. CBR configuration file for Windows systems 10623. A simple Site Selector configuration . . . . 11324. Example of a DNS environment . . . . . 11725. A simple Cisco CSS Controller configuration 129

26. Example of a consultant connected behind theswitches . . . . . . . . . . . . . 135

27. Example of consultant (with optional highavailability partner), configured behindswitch with user interface in front of switch . 136

28. A simple Nortel Alteon Controllerconfiguration . . . . . . . . . . . 147

29. Example of a consultant connected behind theswitch . . . . . . . . . . . . . . 15330. Example of consultant connected through an

intranet in front of switch . . . . . . . 15331. Example of consultant behind switch and

user interface in front of switch . . . . . 15432. Example of consultant configured with

backup servers . . . . . . . . . . . 15533. Example of Nortel Alteon Controller and

Nortel Alteon Web Switch high availability . 15734. Example of a two-tiered WAN configuration

using the self advisor . . . . . . . . . 17835. Example of a configuration consisting of a

single LAN segment . . . . . . . . . 212

36. Example of configuration using local andremote servers . . . . . . . . . . . 212

37. Wide area example configuration with remoteLoad Balancers . . . . . . . . . . . 215

38. Wide area example configuration with serverplatform that supports GRE. . . . . . . 217

39. Example of a private network usingDispatcher . . . . . . . . . . . . 219

40. SNMP commands for Linux and UNIXsystems . . . . . . . . . . . . . 250

41. The graphical user interface (GUI) displayingthe GUI tree structure expansion of theDispatcher component . . . . . . . . 433

42. The graphical user interface (GUI) displaying

the GUI tree structure expansion of the CBRcomponent . . . . . . . . . . . . 434

43. The graphical user interface (GUI) displayingthe GUI tree structure expansion of the SiteSelector component . . . . . . . . . 435

44. The graphical user interface (GUI) displayingthe GUI tree structure expansion of the CiscoCSS Controller component . . . . . . . 436

45. The graphical user interface (GUI) displayingthe GUI tree structure expansion of the NortelAlteon Controller component . . . . . . 437

46. Example of a 2-tier, high availabilityconfiguration using Dispatcher, CBR, andCaching Proxy . . . . . . . . . . . 453

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About this book

This book explains how to plan for, install, configure, use, and troubleshoot IBM

WebSphere Application Server Load Balancer for AIX, HP-UX, Linux, Solaris,

and Windows operating systems. Previously, this product was called Edge ServerNetwork Dispatcher, SecureWay Network Dispatcher, eNetwork Dispatcher, andInteractive Network Dispatcher.

Who should read this book

The Load Balancer Administration Guide is written for experienced network andsystem administrators who are familiar with their operating systems and withproviding Internet services. Prior exposure to Load Balancer is not required.

This book is not intended to support previous releases of Load Balancer.

Reference InformationThe Edge Components Information Center Web site links to the current version ofthis book in HTML and PDF formats.

For the most current updates about Load Balancer, visit the Web site support pageand link to the Technote site.

To access these and related Web pages, go to the URLs listed in Relateddocuments and Web sites on page xvii.

Accessibility

Accessibility features help a user who has a physical disability, such as restrictedmobility or limited vision, to use software products successfully. These are themajor accessibility features in Load Balancer:

v You can use screen-reader software and a digital speech synthesizer to hear whatis displayed on the screen. You can also use voice recognition software, such asIBM ViaVoice, to enter data and to navigate the user interface.

v You can operate features by using the keyboard instead of the mouse.

v You can configure and administer Load Balancer features by using standard texteditors or command-line interfaces, instead of the provided graphical interfaces.For more information about the accessibility of particular features, refer to thedocumentation about those features.

How to send your comments

Your feedback is important in helping to provide the most accurate andhigh-quality information. If you have any comments about this book or any otherEdge components document:

v Send your comments by e-mail to [email protected]. Be sure to include thename of the book, the part number of the book, the version, and if applicablethe specific location of the text you are commenting on (for example, a pagenumber or table number).

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Related documents and Web sitesv Concepts, Planning, and Installation for Edge Components GC31-6918-00

v Programming Guide for Edge Components GC31-6919-00

v

Caching Proxy Administration Guide GC31-6920-00v IBM Web site home: www.ibm.com/

v IBM WebSphere Application Server product: www.ibm.com/software/webservers/appserv/

v IBM WebSphere Application Server library Web site: www.ibm.com/software/webservers/appserv/was/library/

v IBM WebSphere Application Server support Web site: www.ibm.com/software/webservers/appserv/was/support/

v IBM WebSphere Application Server Information Center: www.ibm.com/software/webservers/appserv/infocenter.html

v IBM WebSphere Application Server Edge Components Information Center:www.ibm.com/software/webservers/appserv/ecinfocenter.html

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Part 1. Introduction to Load Balancer

This part provides an overview of Load Balancer and its components, a high-leveldescription of configuration features that are available, a list of hardware and

software requirements, and installation instructions. It contains the followingchapters:

v Chapter 1, Overview of Load Balancer, on page 3

v Chapter 2, Overview of the components of Load Balancer, on page 9

v Chapter 3, Managing your network: Determining which Load Balancer featuresto use, on page 19

v Chapter 4, Installing Load Balancer, on page 29

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Chapter 1. Overview of Load Balancer

This chapter gives an overview of Load Balancer and includes the followingsections:

v What is Load Balancer?

v Which components of Load Balancer can I use?

v What are the advantages to using Load Balancer? on page 4

v How can Load Balancer provide high availability? on page 5

v New features on page 6

For a high-level list of configuration features provided by each of the LoadBalancer components, to assist you in planning which features to use for managingyour network, see Chapter 3, Managing your network: Determining which LoadBalancer features to use, on page 19.

What is Load Balancer?Load Balancer is a software solution for distributing incoming client requestsacross servers. It boosts the performance of servers by directing TCP/IP sessionrequests to different servers within a group of servers; in this way, it balances therequests among all the servers. This load balancing is transparent to users andother applications. Load Balancer is useful for applications such as e-mail servers,World Wide Web servers, distributed parallel database queries, and other TCP/IPapplications.

When used with Web servers, Load Balancer can help maximize the potential ofyour site by providing a powerful, flexible, and scalable solution to peak-demandproblems. If visitors to your site can not get through at times of greatest demand,

use Load Balancer to automatically find the optimal server to handle incomingrequests, thus enhancing your customers satisfaction and your profitability.

Which components of Load Balancer can I use?

IMPORTANT: If you are using Load Balancer for IPv4 and IPv6, only theDispatcher component is available. See Chapter 8, Deploying Dispatcher on LoadBalancer for IPv4 and IPv6, on page 75 for more information.

Load Balancer consists of the following five components that you can useseparately or together to provide superior load-balancing results:

v You can use the Dispatcher component by itself to balance the load on servers

within a local area network or wide area network using a number of weightsand measurements that are dynamically set by Dispatcher. This componentprovides load balancing at a level of specific services, such as HTTP, FTP, SSL,NNTP, IMAP, POP3, SMTP, SIP, and Telnet. It does not use a domain nameserver to map domain names to IP addresses.

For HTTP protocol, you can also use the Dispatchers content-based routingfeature to load balance based on the content of the client request. The chosenserver is the result of matching the URL to a specified rule. Dispatcherscontent-based routing (cbr forwarding method) does not require Caching Proxy.

v For both HTTP and HTTPS (SSL) protocol, you can use the Content BasedRouting (CBR) component to load balance based on the content of the client



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request. A client sends a request to Caching Proxy, and Caching Proxy sends therequest to the appropriate server. The chosen server is the result of matching theURL to a specified rule.

Note: The Content Based Routing (CBR) component is available on allsupported platforms except those running a 64-bit JVM. Alternatively, youcan use the cbr forwarding method of Load Balancers Dispatcher

component to provide content-based routing without the use of CachingProxy. See Dispatchers content-based routing (cbr forwarding method)on page 52 for more information.

v You can use the Site Selector component to balance the load on servers within alocal or wide area network using a DNS round-robin approach or a moreadvanced user-specified approach. Site Selector works in conjunction with aname server to map DNS names to IP addresses.

v You can use the Cisco CSS Controller or the Nortel Alteon Controllercomponent to generate server weights that are then sent to the Cisco CSS Switchor the Nortel Alteon Web Switch respectively for optimal server selection, loadoptimization, and fault tolerance.

For more information on the Dispatcher, CBR, Site Selector, Cisco CSS Controller,and Nortel Alteon Controller components, see What are the components of LoadBalancer? on page 9.

What are the advantages to using Load Balancer?

The number of users and networks connected to the global Internet is growingexponentially. This growth is causing scalability problems that can limit usersaccess to popular sites.

Currently, network administrators are using numerous methods to try to maximizeaccess. With some of these methods, you can choose a different server at random ifan earlier choice is slow or not responding. This approach is cumbersome,

annoying, and inefficient. Another method is standard round-robin, in which thedomain name server selects servers in turn to handle requests. This approach is

better, but still inefficient because it forwards traffic without any consideration ofthe server workload. In addition, even if a server fails, requests continue to be sentto it.

The need for a more powerful solution has resulted in Load Balancer. It offersnumerous benefits over earlier and competing solutions:

Scalability

As the number of client requests increases, you can add serversdynamically, providing support for tens of millions of requests per day, ontens or even hundreds of servers.

Efficient use of equipment

Load balancing ensures that each group of servers makes optimum use ofits hardware by minimizing the hot-spots that frequently occur with astandard round-robin method.

Easy integration

Load Balancer uses standard TCP/IP or UDP/IP protocols. You can add itto your existing network without making any physical changes to thenetwork. It is simple to install and configure.



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Low overhead

Using a simple mac level forwarding method, the Dispatcher componentlooks at the inbound client-to-server flows only. It does not need to see theoutbound server-to-client flows. This significantly reduces its impact on theapplication compared with other approaches and can result in improvednetwork performance.

High availability

The Dispatcher, Cisco CSS Controller, and Nortel Alteon Controllercomponents offer built-in high availability, utilizing a backup machine thatremains ready at all times to take over load balancing if the primary servermachine fail. When one of the servers fails, requests continue to beserviced by the other server. This process eliminates any server as a singlepoint of failure and makes the site highly available.

For more information, see How can Load Balancer provide highavailability?

Content-based routing (using the CBR component or Dispatcher component)

In conjunction with Caching Proxy, the CBR component has the ability toproxy HTTP and HTTPS (SSL) requests to specific servers based on thecontent requested. For example, if a request contains the string /cgi-bin/in the directory portion of the URL, and the server name is a local server,CBR can direct the request to the best server in a set of servers specificallyallocated to handle cgi requests.

Note: The Content Based Routing (CBR) component is available on allsupported platforms except those running a 64-bit JVM.Alternatively, you can use the cbr forwarding method of LoadBalancers Dispatcher component to provide content-based routingwithout the use of Caching Proxy. See Dispatchers content-basedrouting (cbr forwarding method) on page 52 for more information.

The Dispatcher component also provides content-based routing, but it doesnot require the Caching Proxy to be installed. Because the Dispatchercomponents content-based routing is performed in the kernel as packetsare received, it can provide faster content-based routing than the CBRcomponent. The Dispatcher component performs content-based routing forHTTP (using the content type rule) and HTTPS (using SSL session IDaffinity).

Note: Only the CBR component can use the content rule for HTTPS (SSL)when load-balancing traffic based upon the content of the HTTPrequest, which requires decrypting and re-encrypting messages.

How can Load Balancer provide high availability?

DispatcherThe Dispatcher component offers a built-in high availability feature, eliminatingDispatcher as a single point of failure from your network. This feature involves theuse of a second Dispatcher machine that monitors the main, or primary, machineand stands by to take over the task of load balancing should the primary machinefail at any time. The Dispatcher component also offers mutual high availabilitywhich allows two machines to be both primary and secondary (backup) for eachother. See Configure high availability on page 191.

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CBRYou can also achieve a level of high availability using the CBR component whenusing a two-tier configuration with a Dispatcher machine load balancing trafficacross multiple servers that have CBR.

Cisco CSS Controller or Nortel Alteon Controller

The controllers have a high availability feature to eliminate the controller as asingle point of failure. A controller on one machine may be configured as aprimary and a controller on a different machine may be configured as a backup.The backup monitors the primary and stands by to take over the task of providingserver weights to the switches should the primary fail. See High availability onpage 225 for more information.

New features

Load Balancer for IBM WebSphere Application Server Version 6.1 contains anumber of new features. The most significant new features are listed here.

v Support for running load-balancing processes in user space on Linux systems

Support has been added to Load Balancer for IPv4 and IPv6 installations to runload-balancing processes in user space, rather than in kernel space. For Linuxsystems, there is no longer a dependency on the kernel module.

For the most current information on which systems support processing in userspace (kernel free), refer to the following Web site: http://www.ibm.com/support/docview.wss?rs=180&uid=swg27006921.

For more information, see Supported platforms for Load Balancer for IPv4 andIPv6 on page 75.

v Support for HP 11iv2 on PA-RISC (support removed for HP 11iv1)

For information on supported hardware and software requirements, refer to thefollowing Web site: http://www.ibm.com/support/docview.wss?rs=180&uid=swg27006921.

v Support for Linux on zSeries 64-bit systems

Support for Linux on zSeries 64-bit systems is provided only for Load Balancerfor IPv4 and IPv6 installations.

For information about Load Balancer for IPv4 and IPv6 and specialconsiderations for running Linux on zSeries 64-bit systems, see Chapter 8,Deploying Dispatcher on Load Balancer for IPv4 and IPv6, on page 75.

For information on supported hardware and software requirements, refer to thefollowing Web site: http://www.ibm.com/support/docview.wss?rs=180&uid=swg27006921.

v Support for SIP advisor

Support for a Session Initiation Pprotocol (SIP) advisor has been added. The SIP

advisor that is supported runs on TCP protocol only.For more information, see page 175.

v For Linux systems, support of collocated client configurations

This feature applies to all Load Balancer components.

Clients located on the same machine as Load Balancer is supported on Linuxsystems only.

For more information, see Using a collocated client on page 223.

v Support for Firefox browser



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For information on supported versions of Firefox and all supported browsers,refer to the following Web site: http://www.ibm.com/support/docview.wss?rs=180&uid=swg27006921.

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Chapter 2. Overview of the components of Load Balancer

This chapter gives an overview of Load Balancer components and includes thefollowing sections:

v What are the components of Load Balancer?

v Overview of the Dispatcher component

v Overview of the Content Based Routing (CBR) component on page 12

v Overview of the Site Selector component on page 13

v Overview of the Cisco CSS Controller component on page 14

v Overview of Nortel Alteon Controller component on page 16

For a high-level list of configuration features that are provided by each of the LoadBalancer components, and to assist you in planning which features to use formanaging your network, see Chapter 3, Managing your network: Determiningwhich Load Balancer features to use, on page 19.

What are the components of Load Balancer?

The five components of Load Balancer are: Dispatcher, Content Based Routing(CBR), Site Selector, Cisco CSS Controller, and Nortel Alteon Controller. LoadBalancer gives you the flexibility of using the components separately or togetherdepending on your site configuration. This section gives an overview of thesecomponents.


Overview of the Dispatcher component

The Dispatcher component balances traffic among your servers through a uniquecombination of load balancing and management software. Dispatcher can alsodetect a failed server and forward traffic around it. Dispatcher supports HTTP, FTP,SSL, SMTP, NNTP, IMAP, POP3, Telnet, SIP, and any other TCP or stateless UDP

based application.

All client requests sent to the Dispatcher machine are directed to the best serveraccording to weights that are set dynamically. You can use the default values forthose weights or change the values during the configuration process.

Dispatcher offers three forwarding methods (specified on the port):v MAC forwarding method (mac). With this forwarding method, Dispatcher load

balances the incoming request to the server. The server returns the responsedirectly to the client without any involvement of the Dispatcher.

v NAT/NAPT forwarding method (nat). Using Dispatchers Network AddressTranslation (NAT)/ Network Address Port Translation (NAPT) capabilityremoves the limitation for the back-end servers to be located on a locallyattached network. When you want to have servers located at remote locations,you can use the nat technique rather than using a Generic RoutingEncapsulation (GRE)/Wide Area Network (WAN) technique. With the nat



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forwarding method, Dispatcher load balances the incoming request to the server.The server returns the response to Dispatcher. The Dispatcher machine thenreturns the response to the client.

v Content-based routing forwarding method (cbr). Without Caching Proxy, theDispatcher component allows you to perform content-based routing for HTTP(using the content type rule) and HTTPS (using SSL session ID affinity). ForHTTP and HTTPS traffic, the Dispatcher component can provide fastercontent-based routing than the CBR component. With the cbr forwardingmethod, Dispatcher load balances the incoming request to the server. The serverreturns the response to Dispatcher. The Dispatcher machine then returns theresponse to the client.

The Dispatcher component is the key to stable, efficient management of a large,scalable network of servers. With Dispatcher, you can link many individual serversinto what seems to be a single, virtual server. Your site is presented as a single IPaddress to the world. Dispatcher functions independently of a domain nameserver; all requests are sent to the IP address of the Dispatcher machine.

Dispatcher brings distinct advantages in balancing traffic load to clustered servers,

resulting in stable and efficient management of your site.

Managing local servers with Dispatcher

Figure 1 shows a physical representation of the site using an Ethernet network

configuration. The Dispatcher machine can be installed without making anyphysical changes to the network. After a client request is directed to the optimalserver by the Dispatcher, the response is then sent directly from server to clientwith no involvement by the Dispatcher when using MAC forwarding method.

Internet

Client

Client

Client

DispatcherServer 2

Server 3Server 1

Figure 1. Example of a physical representation of a site using Dispatcher to manage local servers



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Managing servers using Dispatcher and Metric Server

Figure 2 illustrates a site in which all servers are on a local network. TheDispatcher component is used to forward requests, and the Metric Server is usedto provide system load information to the Dispatcher machine.

In this example, the Metric Server daemon is installed on each back-end server.You can use Metric Server with the Dispatcher component or any of the other LoadBalancer components.

Managing local and remote servers with Dispatcher

Wide area support in Dispatcher enables you to use both local and remote servers(servers on different subnets). Figure 3 shows a configuration where one local

Figure 2. Example of a site using Dispatcher and Metric Server to manage servers

Figure 3. Example of a site using Dispatcher to manage local and remote servers

Chapter 2. Overview of the components of Load Balancer 11


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Dispatcher (Dispatcher 1) serves as the entry point for all requests. It distributesthese requests among its own local servers (ServerA, ServerB, ServerC) and to theremote Dispatcher (Dispatcher 2), which will load balance to its local servers(ServerG, ServerH, ServerI).

When using Dispatchers NAT forwarding method or using GRE support, widearea support with Dispatcher can also be achieved without using a Dispatcher at

the remote site (where ServerD, ServerE, and ServerF are located). SeeDispatchers NAT/NAPT (nat forwarding method) on page 51 and GRE(Generic Routing Encapsulation) support on page 217 for more information.

Overview of the Content Based Routing (CBR) component

CBR works with Caching Proxy to proxy client requests to specified HTTP orHTTPS (SSL) servers. It allows you to manipulate caching details for faster Webdocument retrieval with low network bandwidth requirements. CBR and CachingProxy examines HTTP requests using specified rule types.

Note: The Content Based Routing (CBR) component is available on all supportedplatforms except those running a 64-bit JVM. Alternatively, you can use thecbr forwarding method of Load Balancers Dispatcher component to providecontent-based routing without the use of Caching Proxy. See Dispatcherscontent-based routing (cbr forwarding method) on page 52 for moreinformation.

CBR gives you the ability to specify a set of servers that handle a request based onregular expression matching of the content of the request. Because CBR allows youto specify multiple servers for each type of request, the requests can be load

balanced for optimal client response. CBR also detects when one server in a set hasfailed, and stops routing requests to that server. The load-balancing algorithm used

by the CBR component is identical to the proven algorithm used by the Dispatchercomponent.

When a request is received by Caching Proxy, it is checked against the rules thathave been defined in the CBR component. If a match is found, then one of theservers associated with that rule is chosen to handle the request. Caching Proxythen performs its normal processing to proxy the request to the chosen server.

CBR has the same functions as Dispatcher with the exception of high availability,SNMP subagent, wide area, and a few other configuration commands.

Caching Proxy must be running before CBR can begin load balancing clientrequests.

Managing local servers with CBR



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Figure 4 shows a logical representation of a site in which CBR is being used toproxy some content from local servers. The CBR component uses Caching Proxy toforward client requests (HTTP or HTTPS) to the servers based on the content ofthe URL.

Overview of the Site Selector componentSite Selector acts as a name server that works in conjunction with other nameservers in a domain name system to load balance among a group of servers usingmeasurements and weights that are gathered. You can create a site configuration tolet you load balance traffic among a group of servers based on the domain nameused for a clients request.

A client submits a request for resolution of a domain name to a name serverwithin its network. Name server forwards the request to the Site Selector machine.Site Selector then resolves the domain name to the IP address of one of the serversthat has been configured under the site name. Site Selector returns the IP addressof the selected server to the name server. The name server returns the IP address to

the client.

Metric Server is a system monitoring component of Load Balancer that must beinstalled in each load-balanced server within your configuration. Using MetricServer, Site Selector can monitor the level of activity on a server, detect when aserver is the least heavily loaded, and detect a failed server. The load is a measureof how hard the server is working. By customizing system metric script files, youcan control the type of measurements used to measure the load. You can configureSite Selector to suit your environment, considering such factors as frequency ofaccess, the total number of users, and types of access (for example, short queries,long-running queries, or CPU-intensive loads).

Figure 4. Example of a site using CBR to manage local servers



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Managing local and remote servers with Site Selector andMetric Server

Figure 5 illustrates a site in which the Site Selector component is used to answerrequests. Server1, Server2, and Server3 are local. Server4, Server5, and Server6 areremote.

A client submits a request for resolution of a domain name to a client name server.The client name server forwards the request through the DNS to the Site Selectormachine (Path 1). Site Selector then resolves the domain name to the IP address ofone of the servers. Site Selector returns the IP address of the selected server to theclient name server. The name server returns the IP address to the client.

After the client receives the IP address of the server, the client routes applicationrequests directly to the selected server (Path 2).

Note: In this example, the Metric Server provides system load information to theSite Selector machine. The Metric Server agent is installed on each back-endserver. Use Metric Server in conjunction with Site Selector; otherwise SiteSelector can only use a round-robin selection method for load balancing.

Overview of the Cisco CSS Controller component

Cisco CSS Controller forms a complementary solution in conjunction with CiscosCSS 11000 series switches. The combined solution blends the CSS 11000 seriesrobust packet forwarding and content routing capabilities with Load Balancerssophisticated awareness algorithms for determining load information andavailability of the service (back-end server application or database). The Cisco CSSController function utilizes Load Balancers weight calculation algorithm, standardand custom advisors, and Metric Server to determine the metrics, health, and load

Internet

Client

name server

Client

Server 1

Metric Server

Server 2

Metric Server

Server 3

Metric Server

Server 4

Metric Server

Server 5

Metric Server

Server 6

Metric Server

SiteSelector

2

1

nameserver

Figure 5. Example of a site using Site Selector and Metric Server to manage local andremote servers



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of the service. With this information Cisco CSS Controller generates serviceweights, which it sends to the Cisco CSS Switch for optimal service selection, loadoptimization, and fault tolerance.

Cisco CSS Controller tracks many criteria, including:

v Active connections and connection rate (the number of new connections within aweight calculation cycle)

v Application and database availability, which is facilitated through the use ofstandard and customized advisors, and service-resident agents tailored to thespecific application

v CPU utilization

v Memory utilization

v User-customizable system metrics

When a Cisco CSS Switch, without Cisco CSS Controller, is determining the healthof a content-providing service, it uses response times for content requests or othernetwork measures. With Cisco CSS Controller in place, these activities areoffloaded from the Cisco CSS Switch to Cisco CSS Controller. Cisco CSS Controller

influences the services weight or ability to serve content, and activates orsuspends a service as appropriate when the service regains or loses availability.

Cisco CSS Controller:

v Uses a published SNMP interface to obtain connection information from theCisco CSS Switch

v Uses advisor input to analyze service availability and response time

v Uses Metric Server information to analyze system load

v Generates weights for each service in the configuration

Weights are applied to all services on a port. For any particular port, the requestsare distributed between services based on their weights relative to each other. Forexample, if one service is set to a weight of 10, and the other to 5 the service set to10 gets twice as many requests as the service set to 5. These weights are providedto the Cisco CSS Switch using SNMP. As the weight of any service is set higher,the Cisco CSS Switch directs more requests to that service.



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Cisco CSS Controller, in conjunction with the Cisco CSS Switch, delivers a best of both worlds solution that combines wire-speed content switching with

sophisticated application awareness, fault tolerance, and service load optimization.Cisco CSS Controller is part of an overall complementary solution between theCisco CSS Switch and IBM WebSphere Application Server Load Balancer.

Overview of Nortel Alteon Controller component

Nortel Alteon Controller in conjunction with the Nortel Alteon family of Webswitches provides a complementary solution that combines the switches packetforwarding speed and capacity with the Load Balancers sophisticated awarenessalgorithms for determining server weights.

Nortel Alteon Controller allows you to develop custom advisors that are capable ofperforming more intelligent, application-aware assessments of the availability and

load of applications used to deploy services.

The Metric Server provides system load information, such as CPU and memoryutilization information, and a framework for you to develop custom system loadmeasurements.

Nortel Alteon Controller collects many types of metric data to determine weightsfor servers being load-balanced by Nortel Alteon Web Switches, including:

v Active and new connections

ClientClient

Internet

CiscoCSS Switch

CiscoCSSSwitch

Consultantfor Cisco

CSS Switch

Consultantfor Cisco

CSSSwitch

Server 1erver 1 Server 2erver 2 Server 3erver 3MetricServer MetricServeretricServer MetricServer

Client

Figure 6. Example of a site using Cisco CSS Controller and Metric Server to manage localservices



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v Application and database availability, which is facilitated through the use ofstandard and customized advisors, and server-resident agents tailored to thespecific application

v CPU utilization

v Memory utilization

v User-customizable server metrics

v Reachability

Nortel Alteon Controller uses SNMP to communicate with the switch.Configuration, state and connection information is retrieved from the switch. Whenserver weights are calculated by the controller, they are set on the switch. Theswitch uses the weights set by the controller to select the best server to handleclient requests for a service.

You can manage the controller using a browser, a remote GUI, or a remotecommand line interface.

Nortel Alteon Controller combined with the Nortel Alteon family of Web switchesdelivers a best of both worlds solution that combines wire-speed packetswitching with sophisticated application awareness, fault tolerance and server loadoptimization. Nortel Alteon Controller is part of a complementary solution

between the Nortel Alteon family of Web switches and IBMs WebSphere.

Internet

intranet

Nortel AlteonSwitch L2

Switch

Nortel AlteonController

server farm

clients

browser, GUI, orcommand line

interface

Figure 7. Example of a site using Nortel Alteon Controller to manage local servers



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Chapter 3. Managing your network: Determining which LoadBalancer features to use

This chapter lists the configuration features of the Load Balancer components soyou can determine which features to use for managing your network:

v Manager, Advisors, and Metric Server functions (for Dispatcher, CBR, and SiteSelector components)

v Dispatcher component features

v Content Based Routing (CBR) component features on page 22

v Site Selector component features on page 25

v Cisco CSS Controller component features on page 26

v Nortel Alteon Controller component features on page 27


Manager, Advisors, and Metric Server functions (for Dispatcher, CBR,

and Site Selector components)

To optimize balancing the load across servers and ensure that the right server ischosen, see:

__ Optimizing the load balancing provided by Load Balancer on page 168

__ Advisors on page 172

__ Metric Server on page 182

Dispatcher component featuresDispatcher supports load balancing across your servers for HTTP, FTP, SSL, SMTP,NNTP, IMAP, POP3, Telnet, SIP, and any other TCP or stateless UDP basedapplication.

Remote administration__ To run Load Balancer configuration from a separate machine from the one

on which the Load Balancer resides, see Remote administration of LoadBalancer on page 241.

(If you are using the Load Balancer for IPv4 and IPv6 installation, thisfeature is not available.)

Collocation__ To run Dispatcher on the same machine as a Web server that you are load

balancing, see Using collocated servers on page 188.

High availability__ To use Dispatcher to remove single point-of-failure limitations in your

network, see Simple high availability on page 57 and Mutual highavailability on page 58.



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(If you are using the Load Balancer for IPv4 and IPv6 installation, the simplehigh availability feature is available, but mutual high availability is not.)

Client to server affinityWhen load balancing SSL (HTTPS) traffic:

__ To ensure that the client uses the same SSL server for multiple connections,

see How affinity feature for Load Balancer works on page 205.__ To ensure that the client uses the same server for HTTP and SSL traffic, see

Cross port affinity on page 206.

(If you are using the Load Balancer for IPv4 and IPv6 installation, the crossport affinity feature is not available.)

__ To ensure that the client uses the same server for multiple connections, seeHow affinity feature for Load Balancer works on page 205.

__ To ensure that a group of clients use the same server for multipleconnections, see Affinity address mask (stickymask) on page 206.

(If you are using the Load Balancer for IPv4 and IPv6 installation, thestickymask feature is not available.)

__ To remove a server from your configuration (for example, for maintenancepurposes) without disrupting client traffic, see Quiesce server connectionhandling on page 207.

Rules-based load balancingIn order to direct clients to different sets of servers for the same Web address, youcan add rules to your Dispatcher configuration. For more information, seeConfigure rules-based load balancing on page 197.

__ To direct clients to different sets of servers based on client source IP address,see Using rules based on the client IP address on page 198.

__ To direct clients to different sets of servers based on client port, see Usingrules based on the client port on page 198.

__ To direct clients to different sets of servers based on time of day, see Usingrules based on the time of day on page 199.

__ To direct clients to servers based on Type of Service (TOS) bits in networkpackets, see Using rules based on type of service (TOS) on page 199.

__ To direct clients to different sets of servers based on site traffic:

__ Using connections per second, see Using rules based on theconnections per second on page 199.

__ Using total active connections, see Using rules based on the totalactive connections on page 200.

__ Reserving and sharing bandwidth for different Web addresses, seeUsing rules based on reserved bandwidth and shared bandwidth on

page 200.__ Ensuring traffic is measured correctly for each of your sets of servers,

see Server evaluation option for rules on page 204.

__ To direct overflow traffic to a default set of servers (for example, servers thatwill respond site busy), see Using rules that are always true on page 202.

__ To override client affinity to ensure that a client does not stick to anoverflow server, see port affinity override on page 203.

If you are using the Load Balancer for IPv4 and IPv6 installation, rules-based loadbalancing is not available.



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Content-based routing using Dispatchers cbr forwardingmethod

To ensure SSL clients return to the same SSL server, based on SSL ID in the clientrequest

__ See page 53.

To direct HTTP clients to different sets of servers using rules based on matchingthe URL content of the client request, see Dispatchers content-based routing (cbrforwarding method) on page 52 and Using rules based on the request contenton page 203 for more information.

__ To distinguish between particular URLs and their service applications, seeServer Partitioning: logical servers configured to one physical server (IPaddress) on page 55.

__ To ensure clients return to the same server when requesting similar contentin multiple connections using cookies created by your Web servers, seePassive cookie affinity on page 210.

__ To load balance Web traffic to caching-proxy servers that allow uniquecontent to be cached on each server (thereby increasing the size of your sites

cache by eliminating redundant caching of content on multiple machines),see URI affinity on page 211.

(If you are using the Load Balancer for IPv4 and IPv6 installation, Dispatchers cbrforwarding method is not available.)

Comparison between the Dispatcher components cbr forwardingmethod and the CBR componentThe

Load Balancer Guide

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