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Manual Chapter: Implementing Bandwidth Load Balancing
Manual Chapter
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9
The BIG-IP® Link Controller provides a variety of methods for managing the traffic flowing in and out of a network. A common method is bandwidth load balancing. In bandwidth load balancing, the Link Controller uses a specific link until a traffic threshold has been met. After that threshold is met, the Link Controller shifts traffic to another link. When the traffic falls below the threshold, the Link Controller shifts traffic back to the first link.
Inbound, which refers to the amount of traffic flowing into the network
Outbound, which refers to the amount of traffic flowing out of the network
Total, which refers to the cumulative amount of traffic flowing in and out of the network
Note: When implementing cost-based load balancing, it is important that your configuration applies to all of the links that the Link Controller manages. For example, F5 Networks does not recommend applying cost-based load balancing to one set of links and ratio load balancing to another set.
To illustrate how bandwidth load balancing works, consider the fictional company SiteRequest. This company has two links for managing its inbound and outbound traffic:
Link Alpha, which is the primary link for the network. This link uses an ISP to which a flat fee of $45 is paid for up to 50 Mbps of total (both inbound and outbound) traffic. If the limit is exceeded, SiteRequest incurs a $0.50/Mbps charge.
Link Beta, which is a secondary link for the network. This link uses an ISP with which SiteRequest does not have a prepaid amount of bandwidth. Instead, SiteRequest is billed based on a pay-as-you-go basis. The rate charged for using this link is set at $0.45/Mbps.
As these rates illustrate, the most cost-efficient configuration for SiteRequests links is to have Link Alpha handle traffic until it reaches 50 Mbps, then send any traffic over 50 Mbps to Link Beta. When the traffic decreases, the Link Controller must switch back to using only Link Alpha again.
Table 9.1 provides additional information about each link.
Router Address
Uplink Address
The first task in designing a Link Controller configuration that uses bandwidth load balancing to manage outbound traffic is to add and configure the links into the Link Controller. You can configure each link using a variety of options; however, the critical setting for this implementation is the Total Traffic option, with which you set the total bandwidth thresholds for the link.
Note: The following procedure applies to the Link Controller system; however you can also use this procedure if you have a Global Traffic Manager. If you are configuring links on a Global Traffic Manager, you must first create a data center, to which you then assign the configured link.
1.
On the Main tab of the navigation pane, expand Link Controller, and then click Links.
2.
Click Create.
3.
In the Name box, type a name for the link.
4.
In the Router Address box, type the IP address of the router.
For this example, type 192.168.5.5.
5.
In the Uplink Address box, type the IP address that corresponds with the external Internet connection.
In this case, type 192.168.5.6.
6.
In the Service Provider box, type the name of the ISP provider.
For this example, select Global ISP.
7.
From the Configuration list, select Advanced.
8.
In the Traffic Limits area, select Up To from the Total list, and then type 4000.
9.
Click Create.
In the Router Address option, type 192.168.10.5.
In the Uplink Address option, type 192.168.10.6.
In the Service Provider option, type Region ISP.
In the Traffic Limits option, select Up To from the Total list, and then type 3000.
After you have added and configured the links as described in Configuring the links, the next task in implementing bandwidth load balancing is to create the default gateway pool that will load balance the traffic across the links.
1.
On the Main tab of the navigation pane, expand Local Traffic and then click Pools.
2.
Click Create.
3.
In the Name box, type the name of the pool.
For this example, type default_gateway_pool.
4.
For the New Members setting, add the IP addresses associated with each link:
For Link Alpha, type the IP address of the link and click Add.
In this example, type the IP address, 192.168.5.5.
For Link Beta, type the IP address of the link and click Add.
In this example, type the IP address, 192.168.10.5.
5.
Click Finished.
After you create a default gateway pool, you must instruct the Link Controller to use the pool as the default gateway connection between the internal network and the Internet.
1.
2.
Click Add.
3.
From the Type list, select Default Gateway.
4.
From the Resource list, select Use Pool.
5.
From the Pool list, select default_gateway_pool.
6.
Click Finished.
After you create the pools, you configure the virtual servers, one for each link that load balances inbound connections across the servers. You also configure one wildcard virtual server to load balance outbound connections across the routers.
VS for Link Alpha 1, which has an IP address of 10.10.5.5:80 and represents a single host on the network.
VS for Link Alpha 2, which has an IP address of 10.10.5.6:80 and represents a single host on the network.
VS for Link Beta 1, which has an IP address of 10.10.10.5:80 and also represents a single host on the network.
VS for Link Beta 2, which has an IP address of 10.10.10.5:80 and also represents a single host on the network.
1.
On the Main tab of the navigation pane, expand Local Traffic and then click Virtual Servers.
2.
Click Create.
3.
In the Name box, for this case, type VS for Link Alpha 1.
4.
In the Destination area, select Host.
5.
In the Service Port box, type 80.
6.
Click Finished.
Repeat the preceding procedure for the additional virtual servers. Once the remaining virtual servers are in the configuration, you can define the wildcard virtual server.
1.
On the Main tab of the navigation pane, expand Local Traffic and then click Virtual Servers.
2.
Click Create.
3.
In the Name box, type the name of the virtual server.
In this case, type outbound.
4.
In the Destination area, type 0.0.0.0.
5.
In the Service Port box, type 0.
6.
Click Finished.
To complete the link load balancing configuration, you must configure a wide IP for each pair of virtual servers you created for each link. Each wide IP in the configuration has a set of virtual servers to which the Link Controller load balances incoming DNS requests. The wide IP is made up of only virtual servers that the Link Controller manages. When you configure the wide IP, you also specify the load balancing methods that the Link Controller applies to the incoming DNS requests.
For this example, you use the wide IP www.siterequest.com, using the Global Availability as the preferred load balancing method, and None for the Alternate and Fallback methods.
1.
On the Main tab of the navigation pane, expand Link Controller and then click Inbound Wide IPs.
2.
Click Create.
3.
In the Name box, type the URL of the wide IP.
For this example, type www.siterequest.com.
4.
In the Load Balancing Method area:
Select Kilobytes/Second from the Preferred list.
Select Round Robin from the Alternate list.
Select Return to DNS from the Fallback list.
5.
In the Member List area, add the virtual servers that you created in Defining the virtual servers for an additional Internet connection.
6.
Click Finished.
At this point, you now have a Link Controller configured to manage DNS traffic for a wide IP; in this example, www.siterequest.com. As data flows in and out of the network, the Link Controller monitors the total amount of bandwidth for each link. While traffic remains below 4Mbps, the Link Controller uses Link Alpha. If traffic exceeds that amount, the Link Controller sends the overflow traffic to Link Beta. And, should a link go offline for any reason, the Link Controller uses the Alternate and Fallback load balancing modes to route traffic through an available link.
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