With the huge increase in the data traffic passing through telco networks, it is no longer feasible for service providers to steer all the traffic through all the value added services (VAS). A service provider should be able to optimize usage of VAS and intelligently steer traffic to improve the user experience. For example, video optimization is not required for traffic that does not include a video. Moreover, if a subscriber is connected to a 4G network, content can be streamed in high definition (HD), and video optimization might not be needed. However, video optimization improves the experience for a user in a 3G network. Similarly, caching provides a faster and better user experience and can be enabled depending on the subscriber plan. Another example of VAS is parental control. If parents provide a mobile handset to a minor child, they would like some kind of control over the websites that their child visits.

To do the above and more, service providers must be able to provide value-added services on a per-subscriber basis. In other words, entities in the service provider network must be capable of extracting the subscriber information and intelligently steering the packet on the basis of this information.

Service chaining determines the set of services through which the traffic from a subscriber must pass before going to the Internet. Instead of sending all the traffic to all the services, the NetScaler intelligently routes all requests from a subscriber to a specific set of services on the basis of the policy defined for that subscriber.

The following figure shows the entities involved in service chaining. The values shown are configured in the procedure that follows the figure. A content switching virtual server on the NetScaler appliance directs requests to the value added services or skips them, depending on the defined rule, and then sends the packet out to the Internet after performing LSN.

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