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Manual Chapter: Load Balancing Connection Requests Using Topologies
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You can configure the BIG-IP® Global Traffic Manager to load balance incoming connection requests to a resource based on the physical proximity of the resource to the client making the request. You can also configure the system to deliver region specific content such as news and weather to a client making a request from a specific location.
This can be accomplished by configuring the Global Traffic Manager to perform Topology load balancing. The Topology load balancing mode helps ensure that connection requests are answered and managed in the fastest possible time.
A topology record is a set of characteristics that maps the origin of a connection request to a specific destination. You create topology records in the Global Traffic Manager that instruct the system where to route connection requests when Topology load balancing is enabled.
Each topology record contains the following elements:
A request source statement that defines the origin of a connection request.
A destination statement that defines the resource to which the Global Traffic Manager directs the connection request.
A weight (topology score) that the system assigns to a server object during the load balancing process.
By default, each time the system configuration is loaded, the Global Traffic Manager automatically sorts the topology records into an ordered list based on the topology longest match sorting algorithm. Before you create topology records, it is essential that you understand how the system sorts the topology record list, and then uses the ordered list to load balance connection requests.
By default, the Global Traffic Manager automatically sorts topology records using the longest match sorting algorithm. The system sorts the records in the following manner:
If the LDNS match priority is the same in multiple topology records, the system sorts these records by the server match priority (server object or left-side of the record).
IP subnet in CIDR format (most specific IP subnet placed at top of list)
Region (customized collection of topologies)
Server negation (record excludes server object)
LDNS negation (record excludes LDNS)
Wildcard records (least specific record placed at bottom of list)
When Topology load balancing is enabled, by default the Global Traffic Manager load balances connection requests using the longest match sorting algorithm. When a connection request comes into the system the load balancing decision is based on the following process:
For each server object that the Global Traffic Manager load balances connection requests to, the system iterates through an ordered list of topology records from first to last and assigns a weight to every server object.
The system locates the first topology record that most specifically matches both the LDNS and the server object and assigns the topology score in the record to the server object.
If the iteration through the list does not find a topology record that matches both the LDNS and the server object, then that server object is assigned a zero score.
When server objects have equal scores, the Global Traffic Manager distributes connection requests among those server objects in a round robin fashion.
To understand the default behavior when Topology load balancing is configured, consider the following scenario. The company Site Request has internal and external customers. The IT department wants to route all connection requests from internal customers on the 10.15.0.0/16 IP subnet to the internal_customer_pool, and all connection requests from external customers on the 10.0.0.0/8 IP subnet to the external_customer_pool.
To do this the system administrator creates two topology records as shown in Figure 9.2. Note that the weights of the topology records are different. This instructs the Global Traffic Man aa ger to route the connection requests correctly.
When a connection request arrives from a source with an IP address of 10.15.65.8, the Global Traffic Manager assigns a weight of 200 to the internal_customer_pool and a weight of 100 to the external_customer_pool. This is because the LDNS 10.15.65.8 matches both request sources 10.15.0.0/16 and 10.0.0.0/8. However, the system load balances the request to the internal_customer_pool, because the weight assigned to that server object is higher.
To further refine the Topology load balancing capabilities of the Global Traffic Manager, you can create regions. A region is a customized collection of topologies that defines a specific geographical location that has meaning for your network. For example, you can create a custom region called Scandinavia that includes Denmark, Iceland, Finland, Norway, and Sweden. After you create a region, you can create a topology record based on that region.
The Global Traffic Manager is much more efficient when using the region topology for load balancing, because when setting load balancing scores for server objects the system iterates through the topology records in order from first to last. Table 9.1 shows how the use of topology regions improves the load balancing performance of the Global Traffic Manager.
The system tests region membership for CIDR-based region members using a (log N) route lookup-based method; for topology record matches, the system uses a linear (N squared) search-based method.
5000 CIDR topology records route requests to data center1
5000 CIDR topology records route requests to data center2
Configuring the Global Traffic Manager to route connection requests to the closest data center
You can configure the Global Traffic Manager to route connection requests to the closest data center using the Topology load balancing mode across pools at the wide IP level and across virtual servers (pool members) at the pool level.
When you configure the Global Traffic Manager for Topology load balancing at the wide IP level, the system load balances connection requests to the pools that are associated with the wide IP. This configuration allows you to route connection requests to the data center that is closest to the requestor, and then to use another load balancing mode to route these connections among the resources in that data center.
Important: Important: To use Topology load balancing at the wide IP level to route connections to a specific data center, you must create pools that have all of their members in the same data center.
Figure 9.3 shows siterequest.net configured for Topology load balancing at the wide IP level. All connection requests from a local domain name server (LDNS) in South America with an IP address of 10.0.0.1 are directed to Pool2 in SouthAmericaDC. All connection requests from an LDNS in North America with an IP address of 11.0.0.1 are directed to Pool1 in NorthAmericaDC. In this example, the Global Traffic Manager selects a pool to which to direct a connection based on topology records that match an LDNS (request source) to a pool (destination). How the system distributes the connections to the members is based on the load balancing mode that you set for each pool.
Figure 9.4 shows the topology records that the Site Request administrator created. Based on these records, when a connection request comes in from the LDNS with an IP address of 10.0.0.1, the Global Traffic Manager assigns a weight of 100 to Pool2 and routes the request to Pool2. When a connection request comes in from the LDNS with an IP address of 11.0.0.1, the Global Traffic Manager assigns a weight of 100 to Pool1 and routes the request to Pool1.
When you configure the Global Traffic Manager for Topology load balancing at the pool level, the system load balances connection requests to the members of a pool. This configuration allows you to set the weight of pool members in different data centers at different levels, and instruct the system to direct traffic to the pool members in a specific data center.
Figure 9.5 shows siterequest.net configured for Topology load balancing at the pool level with all connection requests being directed from an LDNS with an IP address of 10.0.0.1 to pool members that are located in SouthAmericaDC, and all connection requests being directed from an LDNS with an IP address of 10.1.0.1 to pool members that are located in NorthAmericaDC. In this example, the Global Traffic Manager selects a pool member to which to direct a request based on topology records that match a specific LDNS (request source) to a specific virtual server (destination).
Figure 9.6 shows the topology records that the Site Request administrator created. Based on these records, when a connection request comes in from the LDNS with an IP address of 10.0.0.1, the Global Traffic Manager assigns a weight of 100 to SouthAmericaDC and routes the request to SouthAmericaDC. When a connection request comes in from the LDNS with an IP address of 10.1.0.1, the Global Traffic Manager assigns a weight of 100 to NorthAmericaDC and routes the request to NorthAmericaDC.
When you configure the Global Traffic Manager for Topology load balancing at both the wide IP and pool levels, the system first load balances the requests to a pool assigned to the wide IP and then to a member of the pool.
Figure 9.7 shows siterequest.net configured for Topology load balancing at both the wide IP and pool levels with connection requests being directed from an LDNS in Buenos Aires to the SpanishPool in SouthAmericaDC. In this example, the Global Traffic Manager selects a pool to which to direct a connection based on topology records that match an LDNS (request source) to a pool (destination). How the system distributes the connections to the members of SpanishPool is based on topology records that match a specific LDNS (request source) to a specific virtual server (destination).
Figure 9.8 shows the topology records that the Site Request administrator created. Based on these records, when a connection request comes in from an LDNS in Buenos Aires, the Global Traffic Manager assigns a weight of 100 to SpanishPool and SouthAmericaDC. The system routes the request to the SpanishPool pool members that are in SouthAmericaDC.
The Global Traffic Manager uses an IP geolocation database to determine the origin of connection requests. The database that comes with the Global Traffic Manager provides geolocation data for IPv6 addresses at the continent and country levels. It also provides geolocation data for IPv4 addresses at the continent, country, state, ISP, and organization levels. The state-level data is worldwide, and thus includes designations in other countries that correspond to the U.S. state-level in the geolocation hierarchy, such as, provinces in Canada. You can download a monthly update to the IP geolocation database from F5 Networks.
If you require geolocation data at the city-level, contact your F5 Networks sales representative to purchase additional database files.
Note: You can access the ISP and organization-level geolocation data for IPv4 addresses only using the iRules® whereis command.
1.
Log in to the F5 Networks customer web site at https://downloads.f5.com, and click Find a Download.
2.
4.
In the Name column, click Quova-GeolocationUpdates.
5.
Click I Accept to accept the license.
6.
In the Filename column, click the name of the most recent compressed file that you want to download.
9.
Select the directory in which you want to save the compressed file, and then decompress the file to save the RPM files on the system.
10.
Install and load one of the RPM files using the following command, where the path and file name are case-sensitive:
geoip_update_data -f </path to RPM file and file name>
The system installs and loads the specified database file.
1.
On the Main tab of the navigation pane, expand Global Traffic and click Topology.
2.
Click the Create button.
The new record screen opens.
b)
b)
5.
In the Weight box, specify the priority this record has over other topology records.
6.
Click the Create button to save the new topology record.
You can use the Topology load balancing mode to distribute traffic among the pools in a wide IP. To do this, you must have at least two pools configured in the wide IP.
1.
On the Main tab of the navigation pane, expand Global Traffic and click Wide IPs.
2.
Click the name of the wide IP for which you want to assign topology-based load balancing.
The wide IP properties screen opens.
3.
On the menu bar, click Pools.
The pools screen opens displaying a list of the pools currently assigned to the wide IP.
4.
From the Load Balancing Method list, select Topology.
5.
Click the Update button to save your changes.
In addition to setting up the Topology load balancing mode to select a pool within a wide IP, you can also set up the Topology load balancing mode to select a virtual server within a pool.
1.
2.
Click the name of the pool to which you want to assign topology-based load balancing.
The pool properties screen opens.
3.
On the menu bar, click Members.
The Members screen opens displaying a list of the virtual servers currently assigned to the pool.
4.
In the Load Balancing Method option, select Topology from the Preferred list.
5.
Click the Update button to save your changes.
To uninstall an update to the IP geolocation database, reload the default geolocation database files using either the Configuration utility or tmsh.
2.
3.
In the Geolocation area, click the Reload button in the Operations setting.
The system reloads the default geolocation database files that are stored in /usr/share/GeoIP.
1.
2.
Run the command sequence: load / sys geoip
The system reloads the default geolocation database files that are stored in /usr/share/GeoIP.
As your network changes, you might need to refine your existing topology records, or remove outdated topology records. For example, the fictional company SiteRequest has an existing topology statement that routes all traffic originating from the United States to the New York data center. Last week, a new data center in Los Angeles came online. As a result, the topology record that the Global Traffic Manager was using to direct traffic became obsolete, and needed to be removed.
1.
On the Main tab of the navigation pane, expand Global Traffic and click Topology.
2.
Select the topology record that you want to remove from the topology records list by selecting the corresponding Select box.
3.
Click the Delete button.
A confirmation screen appears.
4.
Click the Delete button again to confirm that you want to delete the record.
1.
2.
From the Global Traffic menu, choose Load Balancing.
The load balancing properties screen opens.
3.
Using the Topology Options settings, select or clear the check box to enable or disable the Longest Match option, as needed.
4.
Click the Update button to save your changes.
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