ADC

Traffic distribution in a cluster setup

August 20, 2024

Contributed by:

C C S

In a cluster setup, external networks view the collection of Citrix ADC appliances as a single entity. So, the cluster must select a single node that must receive the traffic. The cluster does this selection by using Equal Cost Multiple Path (ECMP) or cluster link aggregation traffic distribution mechanism. The selected node is called the flow receiver.

Note

For an L3 cluster (nodes across different networks), only ECMP traffic distribution can be used.

The flow receiver gets the traffic and then, using internal cluster logic determines the node that must process the traffic. This node is called the flow processor. The flow receiver steers the traffic to the flow processor over the backplane (if the flow receiver and the flow processor are on the same network) or through the tunnel (if the flow receiver and the flow processor are on different networks).

Note

The flow receiver and flow processor must be nodes capable of serving traffic.

From NetScaler 11 onwards, you can disable steering on the cluster backplane. For more information, see “Disabling Steering on the Cluster Backplane”.

Figure 1. Traffic distribution in a cluster

localized image

The above figure shows a client request flowing through the cluster. The client sends a request to a virtual IP (VIP) address. A traffic distribution mechanism configured on the client data plane selects one of the cluster nodes as the flow receiver. The flow receiver receives the traffic, determines the node that must process the traffic, and steers the request to that node (unless the flow receiver selects itself as the flow processor).

The flow processor establishes a connection with the server. The server processes the request and sends the response to the subnet IP (SNIP) address that sent the request to the server.

If the SNIP address is a striped or partially striped IP address, the traffic distribution mechanism configured on the server data plane selects one of the cluster nodes as the flow receiver. The flow receiver receives the traffic, determines the flow processor, and steers the request to the flow processor through the cluster backplane.
If the SNIP address is a spotted IP address, the node that owns the SNIP address receives the response from the server.

In an asymmetric cluster topology (all cluster nodes are not connected to the external switch), you must use linksets either exclusively or combined with ECMP or cluster link aggregation. For more information, see “Using Linksets”.

The official version of this content is in English. Some of the Cloud Software Group documentation content is machine translated for your convenience only. Cloud Software Group has no control over machine-translated content, which may contain errors, inaccuracies or unsuitable language. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, suitability, or correctness of any translations made from the English original into any other language, or that your Cloud Software Group product or service conforms to any machine translated content, and any warranty provided under the applicable end user license agreement or terms of service, or any other agreement with Cloud Software Group, that the product or service conforms with any documentation shall not apply to the extent that such documentation has been machine translated. Cloud Software Group will not be held responsible for any damage or issues that may arise from using machine-translated content.

Traffic distribution in a cluster setup

August 20, 2024

Contributed by:

C C S

August 20, 2024

Contributed by:

C C S

Traffic distribution in a cluster setup

In this article