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CloudPlatform supports Global Server Load Balancing (GSLB) functionalities to provide business continuity by load balancing traffic to an instance on active zones only in case of zone failures. CloudPlatform achieves this by extending its functionality of integrating with NetScaler Application Delivery Controller (ADC), which also provides various GSLB capabilities, such as disaster recovery and load balancing. The DNS redirection technique is used to achieve GSLB in CloudPlatform.

In order to support this functionality, region level services and service provider are introduced. A new service 'GSLB' is introduced as a region level service. The GSLB service provider is introduced that will provider the GSLB service. Currently, NetScaler is the supported GSLB provider in CloudPlatform. GSLB functionality works in an Active-Active data center environment.

9.7.1. Configuring GSLB

A GSLB deployment is the logical collection of GSLB virtual server, GSLB service, LB virtual server, service, domain, and ADNS service. To create a GSLB site, you must configure load balancing in the zone. You must create GSLB servers and GSLB services for each site. You must bind GSLB services to GSLB servers. You must then create an ADNS service that provides the IP address of the best performing site to the client's request. A GSLB server is an entity that performs load balancing for the domains bound to it by returning the IP address of the best GSLB service. A GSLB service is a representation of the load balancing/content switching server. An LB server load balances incoming traffic by identifying the best server, then directs traffic to the corresponding service. It can also load- balance external DNS name servers. Services are entities that represent the servers. The domain is the domain name for which the system is the authoritative DNS server. By creating an ADNS service, the system can be configured as an authoritative DNS server.

To configure GSLB in your cloud environment, as a cloud administrator you must first configure a standard load balancing setup for each zone. This enables to balance load across different servers in each zone in the region. Then, configure both the NetScaler appliances that you plan to add to each zone as authoritative DNS (ADNS) servers.

Next, as a domain administrator or user, create a GSLB site for each zone, configure GSLB virtual servers for each site, create GLSB services, and bind the GSLB services to the GSLB virtual servers. Finally, bind the domain to the GSLB virtual servers. The GSLB configurations on the two appliances at the two different sites are identical, although each sites load-balancing configuration is specific to that site.

As per the example given above, the administrator of xyztelco is the one who sets up GSLB. Perform steps 1 through b as a cloud administrator. As a domain administrator or user when you create a GSLB rule and assign load balancer rules on the CloudPlatform side, CloudPlatform orchestrates what is given in c through g.

1. For the cloud.dns.name parameter in Global Settings, specify the DNS name of your cloud that tenants will use when creating GSLB rules. For example, xyztelco.com.

2. On the NetScaler side, configure GSLB as given in Configuring Global Server Load Balancing (GSLB)1:

a. Configure a standard load balancing setup.

b. Configure Authoritative DNS, as explained in Configuring an Authoritative DNS Service2.

c. Configure a GSLB site with site name formed from the domain name details.

Configure a GSLB site with the site name formed from the domain name.

As per the example given above, the site names are A.xyztelco.com and B.xyztelco.com.

For more information, see Configuring a Basic GSLB Site3.

d. Configure a GSLB virtual server.

For more information, see Configuring a GSLB Virtual Server4.

e. Configure a GSLB service for each virtual server.

For more information, see Configuring a GSLB Service5.

f. Bind the GSLB services to the GSLB virtual server.

For more information, see Binding GSLB Services to a GSLB Virtual Server6.

g. Bind domain name to GSLB virtual server. Domain name is obtained from the domain details.

For more information, see Binding a Domain to a GSLB Virtual Server7.

3. In each zone that are participating in GSLB, add GSLB-enabled NetScaler device.

For more information, see Section 9.7.1.2, “Enabling GSLB in NetScaler”.

On CloudPlatform side, perform the following as a domain administrator or user:

1. Add a GSLB rule on both the sites.

See Section 9.7.1.3, “Adding a GSLB Rule”.

2. Assign load balancer rules.

See Section 9.7.1.4, “Assigning Load Balancing Rules to GSLB”.

9.7.1.1. Prerequisites and Guidelines

• The GSLB functionality is supported both Basic and Advanced zones.

1 http://support.citrix.com/proddocs/topic/netscaler-traffic-management-10-map/ns-gslb-config-con.html 2 http://support.citrix.com/proddocs/topic/netscaler-traffic-management-10-map/ns-gslb-config-adns-svc-tsk.html 3 http://support.citrix.com/proddocs/topic/netscaler-traffic-management-10-map/ns-gslb-config-basic-site-tsk.html 4 http://support.citrix.com/proddocs/topic/netscaler-traffic-management-10-map/ns-gslb-config-vsvr-tsk.html 5 http://support.citrix.com/proddocs/topic/netscaler-traffic-management-10-map/ns-gslb-config-svc-tsk.html 6 http://support.citrix.com/proddocs/topic/netscaler-traffic-management-10-map/ns-gslb-bind-svc-vsvr-tsk.html 7 http://support.citrix.com/proddocs/topic/netscaler-traffic-management-10-map/ns-gslb-bind-dom-vsvr-tsk.html

Configuring GSLB

• GSLB is added as a new network service.

• GSLB service provider can be added to a physical network in a zone.

• When users have VMs deployed in multiple availability zones which are GSLB enabled, they can use the GSLB functionality to load balance traffic across the VMs in multiple zones.

• The users can use GSLB to load balance across the VMs across zones in a region only if the admin has enabled GSLB in that region.

• The users can load balance traffic across the availability zones in the same region or different regions.

• The admin can configure DNS name for the entire cloud.

• The users can specify an unique name across the cloud for a globally load balanced service. The provided name is used as the domain name under the DNS name associated with the cloud.

The user-provided name along with the admin-provided DNS name is used to produce a globally resolvable FQDN for the globally load balanced service of the user. For example, if the admin has configured xyztelco.com as the DNS name for the cloud, and user specifies 'foo' for the GSLB virtual service, then the FQDN name of the GSLB virtual service is foo.xyztelco.com.

• While setting up GSLB, users can select a load balancing method, such as round robin, for using across the zones that are part of GSLB.

• The user shall be able to set weight to zone-level virtual server. Weight shall be considered by the load balancing method for distributing the traffic.

• The GSLB functionality shall support session persistence, where series of client requests for particular domain name is sent to a virtual server on the same zone.

Statistics is collected from each GSLB virtual server.

9.7.1.2. Enabling GSLB in NetScaler

In each zone, add GSLB-enabled NetScaler device for load balancing.

1. Log in as administrator to the CloudPlatform UI.

2. In the left navigation bar, click Infrastructure.

3. In Zones, click View More.

4. Choose the zone you want to work with.

5. Click the Physical Network tab, then click the name of the physical network.

6. In the Network Service Providers node of the diagram, click Configure.

You might have to scroll down to see this.

7. Click NetScaler.

8. Click Add NetScaler device and provide the following:

For NetScaler:

• Username/Password: The authentication credentials to access the device. CloudPlatform uses these credentials to access the device.

• Type: The type of device that is being added. It could be F5 Big IP Load Balancer, NetScaler VPX, NetScaler MPX, or NetScaler SDX. For a comparison of the NetScaler types, see the CloudPlatform Administration Guide.

• Public interface: Interface of device that is configured to be part of the public network.

• Private interface: Interface of device that is configured to be part of the private network.

• GSLB service: Select this option.

• GSLB service Public IP: The public IP address of the NAT translator for a GSLB service that is on a private network.

• GSLB service Private IP: The private IP of the GSLB service.

• Number of Retries. Number of times to attempt a command on the device before considering the operation failed. Default is 2.

• Capacity: The number of networks the device can handle.

• Dedicated: When marked as dedicated, this device will be dedicated to a single account. When Dedicated is checked, the value in the Capacity field has no significance implicitly, its value is 1.

9. Click OK.

9.7.1.3. Adding a GSLB Rule

1. Log in to the CloudPlatform UI as a domain administrator or user.

2. In the left navigation pane, click Region.

3. Select the region for which you want to create a GSLB rule.

4. In the Details tab, click View GSLB.

5. Click Add GSLB.

Configuring GSLB

6. Specify the following:

• Name: Name for the GSLB rule.

• Description: (Optional) A short description of the GSLB rule that can be displayed to users.

• GSLB Domain Name: A preferred domain name for the service.

• Algorithm: (Optional) The algorithm to use to load balance the traffic across the zones. The options are Round Robin, Least Connection, and Proximity.

• Service Type: The transport protocol to use for GSLB. The options are TCP and UDP.

• Domain: (Optional) The domain for which you want to create the GSLB rule.

• Account: (Optional) The account on which you want to apply the GSLB rule.

7. Click OK to confirm.

9.7.1.4. Assigning Load Balancing Rules to GSLB

1. Log in to the CloudPlatform UI as a domain administrator or user.

2. In the left navigation pane, click Region.

3. Select the region for which you want to create a GSLB rule.

4. In the Details tab, click View GSLB.

5. Select the desired GSLB.

7. Click assign more load balancing.

8. Select the load balancing rule you have created for the zone.

9. Click OK to confirm.