Product Documentation

Configuring the Metrics Exchange Protocol (MEP)

Aug 31, 2016

The data centers in a GSLB setup exchange metrics with each other through the metrics exchange protocol (MEP), which is a proprietary protocol for the Citrix NetScaler. The exchange of the metric information begins when you create a GSLB site. These metrics comprise load, network, and persistence information.

MEP is required for health checking of data centers to ensure their availability. A connection for exchanging network metrics can be initiated by either of the data centers involved in the exchange, but a connection for exchanging site metrics is always initiated by the data center with the lower IP address. By default, the data center uses a subnet IP address (SNIP) or a mapped IP address (MIP) to establish a connection to the IP address of a different data center. However, you can configure a specific SNIP, MIP, the NetScaler IP address (NSIP), or a virtual IP address (VIP) as the source IP address for metrics exchange. The communication process between GSLB sites uses TCP port 3011 or 3009, so this port must be open on firewalls that are between the NetScaler appliances.
Note: You cannot configure a GSLB site IP address as the source IP address for site metrics exchange.

If the source and target sites for a MEP connection (the site that initiates a MEP connection and the site that receives the connection request, respectively) have both private and public IP addresses configured, the sites exchange MEP information by using the public IP addresses.

You can also bind monitors to check the health of remote services. When monitors are bound, metric exchange does not control the state of the remote service. If a monitor is bound to a remote service and metrics exchange is enabled, the monitor controls the health status. Binding the monitors to the remote service allows the NetScaler to interact with a non-NetScaler load balancing device. The NetScaler can monitor non-NetScaler devices but cannot perform load balancing on them. The NetScaler can monitor non-NetScaler devices, and can perform load balancing on them if monitors are bound to all GSLB services and only static load balancing methods (such as the round robin, static proximity, or hash-based methods) are used.

Configuring Site Metric Exchange

Updated: 2014-11-24

Site metrics exchanged between the GSLB sites include the status of each load balancing and content switching virtual server, the current number of connections, the current packet rate, and current bandwidth usage information.

The NetScaler appliance needs this information to perform load balancing between the sites. The site metric exchange interval is 1 second. A remote GSLB service must be bound to a local GSLB virtual server to enable the exchange of site metrics with the remote service.

To enable or disable site metric exchange by using the command line interface

At a command prompt, type the following commands to enable or disable site metric exchange and verify the configuration:

  • set gslb site <siteName> -metricExchange(ENABLED|DISABLED)
  • show gslb site <siteName>

Example

 
set gslb site Site-GSLB-East-Coast -metricExchange ENABLED 
set gslb site Site-GSLB-East-Coast -metricExchange DISABLED 
show gslb site Site-GSLB-East-Coast 

To enable or disable site metric exchange by using the configuration utility

  1. Navigate to Traffic Management > GSLB > Sites, select the site.
  2. In the Configure GSLB Site dialog box, select the Metric Exchange option.

Configuring Network Metric Information Exchange

Updated: 2014-11-24

You can enable or disable the exchange of round trip time (RTT) information about the client's local DNS when the GSLB dynamic method (RTT) is enabled. This information is exchanged every 5 seconds.

For details about changing the GSLB method to a method based on RTT, see Changing the GSLB Method.

To enable or disable network metric information exchange by using the command line interface

At the command prompt, type the following commands to enable or disable network metric information exchange and verify the configuration:

  • set gslb site <siteName> -nwmetricExchange (ENABLED|DISABLED)
  • show gslb site <<siteName>

Example

 
set gslb site Site-GSLB-East-Coast -nwmetricExchange ENABLED 
set gslb site Site-GSLB-East-Coast -nwmetricExchange DISABLED 
show gslb site Site-GSLB-East-Coast 

To enable or disable network metric information exchange by using the configuration utility

  1. Navigate to Traffic Management > GSLB > Sites.
  2. In the Configure GSLB Site dialog box, select the Network Metric Exchange option.

Configuring Persistence Information Exchange

Updated: 2014-11-24

You can enable or disable the exchange of persistence information at each site. This information is exchanged every 5 seconds between NetScaler appliances participating in GSLB.

For details about configuring persistence, see "Configuring Persistent Connections".

To enable/disable persistence information exchange by using the command line interface

At the command prompt, type the following commands to enable or disable persistence information exchange and verify the configuration:

  • set gslb site <siteName> -sessionExchange (ENABLED|DISABLED)
  • show gslb site <siteName>

Example

 
set gslb site Site-GSLB-East-Coast -sessionExchange  ENABLED 
set gslb site Site-GSLB-East-Coast -sessionExchange  DISABLED 
show gslb site Site-GSLB-East-Coast 

To enable/disable persistence information exchange by using the configuration utility

  1. Navigate to Traffic Management > GSLB > Sites, double-click the site.
  2. In the Configure GSLB Site dialog box, select the Persistence Session Entry Exchange option.