Applies To:

Show Versions Show Versions

Manual Chapter: Defining the Logical Network
Manual Chapter
Table of Contents   |   << Previous Chapter   |   Next Chapter >>

After you define the physical components of your network, such as data centers, servers, and links, you can configure the Global Traffic Manager with the logical components. Logical components are abstractions of network resources, such as a virtual servers. Unlike physical components, logical networks can often span multiple physical devices, or encompass a subsection of a single device.
Just as a virtual server is a collection of IP addresses and port numbers, a pool is a collection of virtual servers. Pools represent virtual servers that share a common role on the network. A virtual server, in the context of the Global Traffic Manager, is a combination of IP address and port number that points to a specific resource on the network.
A wide IP is a mapping of a fully-qualified domain name (FQDN) to a set of virtual servers that host the domains content, such as a web site, an e-commerce site, or a content-delivery network (CDN). Wide IPs use pools to organize virtual servers, which creates a tiered load balancing effect: the Global Traffic Manager first load balances requests to a wide IP to the appropriate pool, then load balances within the pool to the appropriate virtual server.
The broadest collection of logical network components is distributed applications. A distributed application is a group of wide IPs that serves as a single application to a site visitor. The Global Traffic Manager does not load balance on wide IPs in a distributed application; however, using distributed applications within the Global Traffic Manager provides better visibility into the applications users access.
To better understand the interactions between pools, wide IPs, and data centers, consider the fictional company of SiteRequest. SiteRequest is an online application repository. Currently, its Web presence consists of a main site, www.siterequest.com, a download area, downloads.siterequest.com, and a search area, search.siterequest.com.
These three fully-qualified domain names (FQDNs), www.siterequest.com, downloads.siterequest.com, and search.siterequest.com, are wide IPs. Each of these wide IPs contain several pools of virtual servers. For example, www.siterequest.com contains two pools of virtual servers: poolMain, and poolBackup. When the Global Traffic Manager receives a connection request for www.siterequest.com, it applies its load balancing logic to select an appropriate pool to handle the request.
Once the Global Traffic Manager selects a pool, it then load balances the request to the appropriate virtual server. For example, mainPool contains three virtual servers: 192.168.3.10:80, 192.168.4.20:80, and 192.168.5.30:80. The Global Traffic Manager responds to the system that made the connection request with the selected virtual server. From then on, the Global Traffic Manager steps out of the communication, and the system requesting the resource communicates directly with the virtual server.
Note: If one of these virtual servers was managed by a load balancing server, the IP address and port number would likely point to a proxy on which the load balancing server listened for connection requests. In that case, the load balancing server would manage the connection to the appropriate resource.
For administration purposes, the wide IPs downloads.siterequest.com and search.siterequest.com are added to a single distributed application, siterequest_download_store. This configuration provides the IT staff the ability to track the performance of the distributed application, as that has an immediate impact on users visiting their web sites.
A pool represents one or more virtual servers that share a common role on the network. A virtual server, in the context of the Global Traffic Manager, is a combination of IP address and port number that points to a specific resource on the network.
The Global Traffic Manager considers any virtual servers that you add to a pool to be pool members. A pool member is a virtual server that has specific attributes that pertain to the virtual server only in the context of that pool. Through this differentiation, you can customize settings, such as thresholds, dependencies, and health monitors, for a given virtual server on a per-pool basis.
As an example of the difference between pool members and virtual servers, consider the fictional company SiteRequest. In the London data center, the IT team has a virtual server that acts as a proxy for a Local Traffic Manager. This virtual server provides the main resources for name resolution requests for the companys main Web page that originate from Europe. This same virtual server provides backup resources for name resolution requests that originate from the United States. Because these are two distinctly different roles, the virtual server is a pool member in two different pools. This configuration allows the IT team to customize the virtual server for each pool to which it belongs, without modifying the actual virtual server itself.
As described in Chapter 5, Defining the Physical Network, you can add virtual servers to the Global Traffic Manager only by first defining a server that represents a physical component of your network. Once you add these virtual servers, however, you can divide them into as many or as few pools as needed.
The first step in working with pools is defining them. The basic definition of a pool is a name and at least one virtual server. You can expand on this definition by assigning specific load balancing methods, a fallback IP address (in the event that the load balancing methods fail to return a valid virtual server), and one or more health monitors, which use various methods to determine if the virtual servers within the pool are available.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Pools.
The main pools screen opens.
2.
Click the Create button.
3.
In the Name box, type a name for the pool.
4.
In the Members area, for Member List, add the virtual servers that belong to this pool.
Note that a virtual server can belong to more than one pool.
5.
Configure the remaining pool settings.
For additional assistance with these settings, please see the online help.
6.
Click the Finished button to save the new pool.
A pool is defined as one or more virtual servers that share a common role on the network. When you first defined a pool, you added at least one virtual server to it. This virtual server becomes a pool member and, as a pool member, can be customized as it pertains to its specific role within the pool. As your network changes, you might find that you need to add new virtual servers to a pool.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Pools.
The main pools screen opens.
2.
3.
On the menu bar at the top of the screen, click Members.
The pool members screen opens. This screen lists the virtual servers currently assigned to the pool, and allows you to modify how the Global Traffic Manager load balances requests across these virtual servers.
4.
In the Members area, click the Manage button.
The manage members screen opens.
5.
In Members List, use the options provided to add a virtual server to the pool.
You can repeat this step to add more than one virtual server at a time. For more information on these options, see the online help.
6.
Click the Finished button to update the pool with the new virtual server.
Your network likely changes over time. As a result, you might find that you need to remove virtual servers from a pool. For example, the virtual server underlying this pool member might be obsolete due to an upgrade, or you might reconfigure the pool to perform a different role and certain virtual servers no longer apply.
You can remove a virtual server from a pool at any time. Removing a virtual server does not delete it completely from the Global Traffic Manager; it is still exists and remains associated with its physical server. However, it ceases to be a pool member for the given pool, so any customizations that pertain to that pool member are deleted.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Pools.
The main pools screen opens.
2.
Click the name of the pool to which you want to remove a virtual server.
The properties screen of that pool opens.
3.
On the menu bar at the top of the screen, click Members.
The pool members screen opens. This screen lists the virtual servers currently assigned to the pool and allows you to modify how the Global Traffic Manager load balances requests across these virtual servers.
4.
Click the Manage button.
The Manage Members screen opens.
5.
In Members List, select the virtual server you want to remove and click Remove.
You can repeat this step to remove more than one virtual server at a time.
6.
Click the Finished button to update the pool without the virtual server.
Certain load balancing methods within the Global Traffic Manager select virtual servers based on the order in which they are listed in the pool. For example, the load balancing method, Global Availability, instructs the Global Traffic Manager to select the first virtual server in the pool until it reaches capacity or goes offline, at which point it selects the next virtual server until the first pool becomes available again.
See Chapter 7, Load Balancing with the Global Traffic Manager for more information on load balancing methods that the Global Traffic Manager supports.
If you use one of these load balancing methods, you may want to arrange the order in which virtual servers are listed in a pool at any time. When you organize your virtual servers in conjunction with these load balancing methods, you can ensure that your most robust virtual server always receives resolution requests, while the other virtual servers act as backups in case the primary virtual server becomes unavailable.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Pools.
The main pools screen opens.
2.
Click the name of the pool to which you want to organize virtual servers.
The properties screen of that pool opens.
3.
From the menu bar at the top of the screen, click Members.
The pool members screen opens. This screen lists the virtual servers currently assigned to the pool and allows you to modify how the Global Traffic Manager load balances requests across these virtual servers.
4.
Click the Manage button.
The Manage Members screen opens.
5.
In Members List, select a virtual server and click either the Up or Down buttons to arrange it.
You can repeat this step to organize more than one virtual server at a time.
6.
Click the Finished button to update the pool with the organized virtual servers.
One of the load balancing methods that the Global Traffic Manager supports is the Ratio mode. This mode instructs the system to load balance network requests based on the weights assigned a specific resource. If you use the Ratio mode to load balance across virtual servers in a pool, you must assign weights to those virtual servers. A weight is a value assigned to a resource, such as a pool, that the Global Traffic Manager uses to determine the frequency at which the resource receives connection requests. The Global Traffic Manager selects a resource based on the weight of that resource as a percentage of the total of all weights in that resource group.
To illustrate the use of weights in connection load balancing, consider the fictional company SiteRequest. One of SiteRequests wide IPs, www.siterequest.com, contains a pool labeled poolMain. This pool uses the Ratio load balancing mode and contains three virtual servers, with the following weight assignments:
Notice that the total of all the weights in this pool is 100. Each time the Global Traffic Manager selects this pool, it load balances across all three virtual servers. Over time, the load balancing statistics for this pool will appear as follows:
This pattern exists because the weight value, 50, is 50 percent of the total weight for all virtual servers (100), while the weight value, 25, is 25 percent of the total.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Pools.
The main pools screen opens.
2.
Click the name of the pool to which you want to organize virtual servers.
The properties screen of that pool opens.
3.
On the menu bar at the top of the screen, click Members.
The pool members screen opens. This screen lists the virtual servers currently assigned to the pool and allows you to modify how the Global Traffic Manager load balances requests across these virtual servers.
4.
Click the Manage button.
The manage members screen opens.
5.
From the Virtual Server list, select the virtual server to which you want to assign a ratio value.
If the virtual server already belongs to the pool, you must first remove the virtual server from the pool and then add it back in again. For more information, see Removing virtual servers from pools.
6.
In the Ratio box, type a numerical value that represents the weight of the virtual server as compared to other virtual servers within the same pool. The higher the value in this setting, the greater the frequency at which the Global Traffic Manager selects the virtual server.
7.
Click the Add button to add the virtual server, with ratio value, to the pool.
8.
Click the Finished button to save your changes.
By default, any pool that you create in the Global Traffic Manager is enabled. This state means that the pool is accessible to the Global Traffic Manager as it balances connection requests. If you need to temporarily disable a pool, such as for a maintenance period, you can do so at any time and re-enable it when it is ready to receive name resolution requests.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Pools.
The main pools screen opens.
3.
Click the Disable button.
After a few seconds, the pool becomes disabled. You can verify that the pool is disabled by looking at its status icon, located in the Status column in the table of pools. The status of a disabled pool is a black square.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Pools.
The main pools screen opens.
3.
Click the Enable button.
After a few seconds, the pool becomes enabled. The status icon of the pool, located in the Status column in the table of pools, changes to reflect the current availability of the pool. For example, a pool that is enabled and verified as available by the Global Traffic Manager has a status icon of a green circle.
A wide IP is a mapping of a fully-qualified domain name (FQDN) to a set of virtual servers that host the domains content, such as a web site, an e-commerce site, or a CDN. Wide IPs use pools to organize virtual servers, which creates a tiered load balancing effect: the Global Traffic Manager first load balances requests to a wide IP to the appropriate pool, then load balances within the pool to the appropriate virtual server.
The first step in working with wide IPs is defining them. The basic definition of a wide IP is a name and at least one pool. You can expand on this definition by assigning specific load balancing methods, adding iRules, which are scripts that programmatically control how the Global Traffic Manager handles name resolution requests.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Wide IPs.
The wide IP screen opens.
2.
Click the Create button.
The New Wide IP screen opens.
3.
In the Name box, type the fully-qualified domain name for the wide IP.
4.
In the Pools section, use the Pool List option to add the pools that belong to this wide IP.
Note that a pool can belong to more than one wide IP.
5.
Configure the remaining wide IP settings.
For additional assistance with these settings, please see the online help.
6.
Click the Finish button to save the new wide IP.
The Global Traffic Manager supports wildcard characters in both wide IP names and wide IP aliases. You can use the wildcard characters to simplify your maintenance tasks if you have a large quantity of wide IP names and/or wide IP aliases. The wildcard characters you can use are: the question mark ( ? ), and the asterisk ( * ). The guidelines for using the wildcard characters are as follows:
The question mark ( ? )
You can use the question mark to replace a single character, with the exception of dots ( . ).
You can use more than one question mark in a wide IP name or alias.
You can use both the question mark and the asterisk in the same wide IP name or alias.
The asterisk ( * )
You can use the asterisk to replace multiple consecutive characters, with the exception of dots ( . ).
You can use more than one asterisk in a wide IP name or alias.
You can use both the question mark and the asterisk in the same wide IP name or alias.
???.mydomain.net
www.??domain.net
www.my*.net
www.??*.net
www.my*.*
???.my*.*
*.*.net
www.*.???
A wide IP must contain at least one pool, which then must contain at least one pool member. This hierarchal configuration allows the Global Traffic Manager to load balance connection requests for a wide IP at two levels: first, the connection is load balanced across the pools assigned to the wide IP; second, the connection is load balanced across the pool members within the given pool.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Wide IPs.
The Wide IPs screen opens.
2.
Click the name of the wide IP to which you want to add a pool.
The properties screen of that wide IP opens.
3.
On the menu bar at the top of the screen, click Pools.
The pools screen opens. This screen contains a list of the pools currently assigned to the wide IP.
4.
Click the Manage button.
The manage pools screen opens.
5.
Use the Pool List settings to add a pool to the wide IP.
For more information, see the online help.
6.
Click the Finished button to save your changes to the wide IP.
When you remove a pool from a wide IP, the Global Traffic Manager ceases to use that pool when load balancing name resolution requests. Removing a pool does not delete it from the Global Traffic Manager; it remains available so you can add it to another wide IP.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Wide IPs.
The Wide IPs screen opens.
2.
Click the name of the wide IP from which you want to remove a pool.
The properties screen of that wide IP opens.
3.
On the menu bar at the top of the screen, click Pools.
The Pools screen opens. This screen contains a list of the pools currently assigned to the wide IP.
4.
Click the Manage button.
The manage pools screen opens.
5.
Use the Pools List option to select the pool that you want to remove and click Remove.
6.
Click the Update button to save your changes to the wide IP.
Certain load balancing methods within the Global Traffic Manager select pools based on the order in which they are listed in the wide IP. For example, the load balancing method, Global Availability, instructs the Global Traffic Manager to select the first pool in the wide IP until it becomes unavailable, at which point it selects the next pool until the first pool becomes available again.
See Chapter 7, Load Balancing with the Global Traffic Manager for more information on load balancing methods that the Global Traffic Manager supports.
If you use one of these load balancing methods, you may want to arrange the order in which pools are listed in a wide IP. When you organize your pools in conjunction with these load balancing methods, you can ensure that your most robust pool always receives resolution requests, while the other pools act as backups in case the primary pool becomes unavailable.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Wide IPs.
The Wide IPs screen opens.
2.
3.
On the menu bar at the top of the screen, click Pools.
The Pools screen opens. This screen contains a list of the pools currently assigned to the wide IP.
4.
Click the Manage button.
The manage pools screen opens.
5.
Use the Pools List settings to select the pool and click either the Up or Down buttons to change its sequence.
For more information, see the online help.
6.
Click the Update button to save your changes to the wide IP.
One of the load balancing methods that the Global Traffic Manager supports is the Ratio mode. This mode instructs the system to load balance network requests based on the weights assigned a specific resource. If you use the Ratio mode to load balance across pools in a wide IP, you must assign weights to those pools. A weight is a value assigned to a resource, such as a pool, that the Global Traffic Manager uses to determine the frequency at which the resource receives connection requests. The Global Traffic Manager selects a resource based on the weight of that resource as a percentage of the total of all weights in that resource group.
To illustrate the use of weights in connection load balancing, consider the fictional company SiteRequest. One of SiteRequests wide IPs, www.siterequest.com, uses the Ratio load balancing mode and contains three pools, with the following weight assignments:
Notice that the total of all the weights in this wide IP is 100. Each time the Global Traffic Manager selects this wide IP, it load balances across all three pools. Over time, the load balancing statistics for this wide IP will appear as follows:
This pattern exists because the weight value, 50, is 50 percent of the total weight for all pools, while the weight value, 25, is 25 percent of the total.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Wide IPs.
The Wide IPs screen opens.
2.
3.
On the menu bar, click Pools.
The Pools screen opens. This screen contains a list of the pools currently assigned to the wide IP.
4.
Click the Manage button.
The Manage Pools screen opens.
5.
Use the Pool List to select the pool to which you want to assign a ratio value.
If the pool already belongs to the wide IP, you must first remove the pool from the wide IP and then add it back in again.
6.
In the Ratio box, type a numerical value that represents the weight of the pool as compared to other pools within the same pool. The higher the value in this box, the greater the frequency at which the Global Traffic Manager selects the pool.
7.
Click the Add button to add the pool, with ratio value, to the pool.
8.
Click the Finished button to save your changes.
By default, any wide IP that you create in the Global Traffic Manager is enabled. This state means that the wide IP is accessible to the Global Traffic Manager as it balances connection requests. If you need to temporarily disable a wide IP, such as for a maintenance period, you can do so at any time and re-enable it later.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Wide IPs.
The Wide IPs screen opens.
3.
Click the Disable button.
After a few seconds, the wide IP becomes disabled. You can verify that the wide IP is disabled by looking at its status icon, located in the Status column in the table of wide IPs. The status of a disabled wide IP is a black square.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Wide IPs.
The wide IP screen opens.
3.
Click the Enable button.
After a few seconds, the wide IP becomes enabled. The status icon of the pool, located in the Status column in the table of wide IP, will change to reflect the current availability of the wide IP. For example, a wide IP that is enabled and verified as available by the Global Traffic Manager will have a status icon of a green circle.
Wide IPs also support iRules for further managing and directing network traffic. An iRule is a set of one or more Tcl-based expressions that direct network traffic beyond load balancing operations.
A wide IP does not require iRules to operate effectively. However, iRules are a powerful mechanism for customizing how the Global Traffic Manager handles network connection requests.
You can add an iRule to a wide IP at any time. When you add an iRule to a wide IP, the Global Traffic Manager starts to use the iRule to determine how to load balance name resolution requests.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Wide IPs.
The Wide IPs screen opens.
2.
3.
On the menu bar, click iRules.
The iRules screen opens. This screen contains a list of the iRules currently assigned to the wide IP.
4.
Click the Manage button.
The manage iRules screen opens.
5.
Use the iRules List option to use the options provided to add an iRule to the wide IP.
6.
Click the Finished button to save your iRule to the wide IP.
When you remove an iRule from a wide IP, the Global Traffic Manager no longer uses the iRule when determining how to load balance a name resolution request. Removing an iRule does not delete it from the Global Traffic Manager; you can still access the iRule by clicking iRules in the Global Traffic section of the Main tab.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Wide IPs.
The Wide IPs screen opens.
2.
Click the name of the wide IP in which you want to remove an iRule.
The properties page of that wide IP opens.
3.
On the menu bar at the top of the screen, click iRules.
The iRules screen opens. This screen contains a list of the iRules currently assigned to the wide IP.
4.
Click the Manage button.
The manage iRules screen opens.
5.
Use the iRules List option to select the iRule that you want to remove and click Remove.
6.
Click the Update button to save your changes to the wide IP.
Often, you might find that a wide IP can benefit from more than one iRule. For example, a wide IP might have an iRule that focuses on the geographical source of the name resolution request, and another that focuses on redirecting specific requests to a different wide IP. If you assign more than one iRule to a wide IP, the Global Traffic Manager applies iRules in the order in which they are listed in the iRules List for the wide IP.
You can change the order in which the Global Traffic Manager applies iRules to network connection requests at any time.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Wide IPs.
The Wide IPs screen opens.
2.
3.
On the menu bar at the top of the screen, click iRules.
The iRules screen opens. This screen contains a list of the iRules currently assigned to the wide IP.
4.
Click the Manage button.
The manage iRules screen opens.
5.
Use the iRules List to select the iRule and click either the Up or Down buttons to arrange it.
6.
Click the Finished button to save your changes.
In networks that use IPv6 addresses, you can configure the Global Traffic Manager to send a NoError response when it receives a DNS request for a record for which there is no corresponding AAAA record.
In IPv6 environments, a system receiving a DNS request for a zone is required to send a specific response, called a NoError response, any time it receives an IPv6 request for a zone that does not contain a corresponding AAAA record. After receiving this response, the client making the request can re-send the request for the equivalent IPv4 A record instead. Using the NoError response allows the client to send this request sooner and receive the name resolution faster.
By default, the Global Traffic Manager does not send a NoError response when it does not have a AAAA record for a given zone. However, you can enable this response on a per-wide IP basis.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Wide IPs.
The Wide IPs screen opens.
2.
Click the name of the wide IP to which you want to implement the noerror response.
The properties screen of that wide IP opens.
4.
From the IPv6 NoError Response list, select Enabled.
5.
Click Update to save your changes.
A distributed application is a collection of wide IPs that serve as a single application to a site visitor. Within the Global Traffic Manager, you have several advantages when creating a distributed application:
You can organize logical network components into groups that represent the business environment for which these components were designed.
You can configure a distributed application so that it is dependent on a physical component of your network, such as a data center, server, or link. If this physical component becomes unavailable, the Global Traffic Manager flags the distributed application as unavailable as well. These dependencies ensure that a user cannot access a distributed application that does not have all of its resources available.
You can define persistence for a distributed application, ensuring that a user accessing the distributed application uses the same network resources until they end their session.
The first step in working with distributed applications is defining them. The basic definition of a distributed application is a name and at least one wide IP. You can expand on this definition by determining that the availability of application depends on virtual servers, servers, or data centers and determining if requests coming from the same source during a specific period of time should go to the same pool, or to a different one.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Distributed Applications.
The distributed applications screen opens.
2.
Click the Create button.
The New Distributed Application screen opens.
3.
In the Name box, type a name for the distributed application.
4.
Use the Member List settings to add the wide IPs that belong to this distributed application.
Note that a wide IP can belong to only one distributed application. For more information on wide IPs, see Setting up wide IPs.
5.
Configure the remaining distributed application settings.
For additional assistance with these settings, please see the online help.
6.
Click the Finish button to create the distributed application.
A distributed application typically consists of multiple wide IPs that, collectively, provide a common set of functions for end-users. Through the Global Traffic Manager, you can add wide IPs to a distributed application at any time.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Distributed Applications.
The distributed applications screen opens.
3.
On the menu bar, click Members.
The members screen opens. This screen contains a list of the wide IPs currently assigned to the distributed application.
4.
Click the Manage button.
The manage wide IPs screen opens.
5.
Use the Member List settings to add a wide IP to the distributed application.
6.
Click the Finished button to save the distributed application.
You can remove a wide IP from a distributed application at any time. For example, the role of the distributed application might change, resulting in one of its original wide IPs being unnecessary. Alternatively, a wide IP might be removed because it has been replaced with a newer one. Removing a wide IP does not delete it from the Global Traffic Manager; it remains available to the Global Traffic Manager when load balancing connection requests.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Distributed Applications.
The distributed applications screen opens.
3.
On the menu bar at the top of the screen, click Members.
The members screen opens. This screen contains a list of the wide IPs currently assigned to the distributed application.
4.
Click the Manage button.
The Manage Wide IPs screen opens.
5.
Use the Members List settings to select the wide IP that you want to remove and click Remove.
6.
Click the Finished button to save the distributed application.
When you create a distributed application in the Global Traffic Manager, the system acquires information about the data centers, servers, and links that make up the application. You have the option of setting the distributed application to be dependent on any one type of these physical components. With dependency, when a resource such as a virtual server becomes unavailable, the Global Traffic Manager considers all other resources that share the same physical component of that resource to be unavailable as well.
The following examples illustrate how dependencies can affect the availability of a given distributed application. These examples involve the fictional company SiteRequest.com. This company has a distributed application that consists of two wide IPs: www.siterequest.com and downloads.siterequest.com. They also have data centers in New York, Paris, and Tokyo, each of which provides resources that the distributed application can access. In each example, a lightning storm caused the New York data center to lose power. Although the emergency power starts immediately, one of the virtual servers and one of the Internet links used by the application has gone offline.
Example 1: Data Center Dependency
If the application uses data center dependency, the Global Traffic Manager considers the entire data center to be unavailable to the application, even if other virtual servers for the application remain available at the data center. Other connection requests, independent of the application, can still be sent to the data center.
Example 2: Server Dependency
If the application uses server dependency, the Global Traffic Manager treats the server hosting the virtual server to be unavailable to the application, even if other virtual servers on that server are online. Other connection requests, independent of the application, can still be sent to the server.
Example 3: Link Dependency
If the application uses link dependency, the Global Traffic Manager treats all resources for the application that use that link to be unavailable to the application. Other connection requests, independent of the application, can still be sent to these resources through other links.
Note: Dependencies are not required for a given distributed application. If you do not define a dependency, then the Global Traffic Manager considers the application available as long as there is at least one resource to which it can load balance a name resolution request.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Distributed Applications.
The distributed applications screen opens.
3.
On the menu bar, click Members.
The members screen opens. This screen contains a list of the wide IPs currently assigned to the distributed application.
4.
In the General Properties area, select a dependency level from the Dependency Level list. This is the physical component on which you want the distributed application to depend.
If one of these components becomes unavailable, the Global Traffic Manager considers the distributed application to be unavailable as well.
5.
Click the Update button to save the changes to the application.
Distributed applications often consist of many data centers, servers, and links. Consequently, you might find that you need to remove a given physical component without interrupting access to the application. For example, you might want to take a server down to update it, yet do not want its absence to affect the application. To accommodate this and similar situations, the Global Traffic Manager provides options so you can enable and disable distributed application traffic for a specific physical component on the network.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Distributed Applications.
The distributed applications screen opens.
2.
Click the name of distributed application for which you want to disable traffic.
The properties screen for that application opens.
3.
On the menu bar at the top of the Distributed Applications list screen, click Data Centers, Links, or Servers.
A screen listing the available physical components opens.
4.
Check the appropriate Select box for each physical component for which you want to disable application traffic.
5.
Click Disable Distributed Application Traffic.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Distributed Applications.
The distributed applications screen opens.
2.
Click the name of distributed application for which you want to enable traffic.
The properties screen for that application opens.
3.
On the menu bar at the top of the Distributed Applications list screen, click either Data Centers, Links, or Servers.
A screen listing the available physical components opens.
4.
Check the appropriate Select box for each physical component for which you want to enable application traffic.
5.
Click Enable Distributed Application Traffic.
Many distributed applications require that users access a single set of resources until they complete their transaction. For example, customers purchasing a product online might need to remain with the same data center until they finish their order. In the context of the Global Traffic Manager, this requirement is called persistence. Persistence is the state in which a user of the system remains with the same set of resources until the customer closes the connection.
1.
On the Main tab of the navigation pane, expand Global Traffic and then click Distributed Applications.
The distributed applications screen opens.
2.
Click the name of distributed application for which you want to enable persistent connections.
The properties screen for that application opens.
3.
On the menu bar at the top of the Distributed Applications list screen, click Members.
The Members screen appears.
5.
Click the Update button to save your changes to the application.
Table of Contents   |   << Previous Chapter   |   Next Chapter >>

Was this resource helpful in solving your issue?




NOTE: Please do not provide personal information.



Incorrect answer. Please try again: Please enter the words to the right: Please enter the numbers you hear:

Additional Comments (optional)