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The term “service chaining” is defined as a series of service functions, which a packet must flow through. The reason for its gaining popularity is due to advancements in technologies such as SDN and NFV, which allow for dynamic service chaining. Dynamic service chaining refers to software controlled service chains, where the traffic for a given flow is intelligently steered towards the appropriate network functions based on a number of labels, such as customer profile, service type and traffic patterns.
Traditional Service Chaining. Today, network services, also called “enablers”, are typically deployed as hardware appliances, which are physically connected. These devices play a pivotal role in network operators achieving the security and performance they desire. Examples of such devices include the following:
In the static service chain model, all traffic will have to flow through each of the enablers, even though only a subset of these services may be required.
There are several limitations to this approach:
In the example scenario illustrated in Figure below (“Example service function chain implemented by network operators today”), Subscriber 1 wishes to access video content on their mobile device. The user would simply need the video optimisation service, as well as basic firewalling. However, the user’s traffic will have to traverse the entire chain. Adding to this, services must often be applied in a specific order, which implies the need for complex routing techniques and VLANs to ensure that this performed correctly. This example highlights the sub-optimal use of network and compute resources, as the entire service chain has to be traversed, regardless of whether this is required or not.
Dynamic Service Chaining. With SDN and NFV however, physical devices are replaced by virtual machines, which accelerate an operator's time to market for a new service. The reason for this is that, in SDN, the centralised controller has a global view of the network, which allows for new service chains to be created by a simple change in policy associated with a flow.
As illustrated in Figure above (“Example of dynamic service chain using SDN & NFV”), when traffic arrives at the network gateways, it is now labelled by a dedicated classification device with the use of deep packet inspection (DPI). The traffic is then intelligently forwarded to the required services, based on the service identifier. The identifier itself can be derived from a field in the traffic such as: network service header (NSH), virtual local area network (VLAN), Source MAC Address (SMAC), or it can be directly programmed in the switch flow-tables. This allows for network and compute resources to be used more efficiently, as traffic only flows through the required services. The provider is thereby relieved from continuously having to over-provision the network.
An SDN based service chaining solution allowed provider to reduce capital expenditures for a service by 80%.
The following are benefits that operators can realise by leveraging dynamic service chaining in their organisation:
With the help of innovative implementations brought in by SDN and NFV, dynamic service chaining is set to change the way in which network operators deliver services to their subscribers, giving them an unprecedented agility to design, deploy, manage and upgrade each service specifically tailored to their individual customers’ needs.
This will in turn result in a better user experience for the customers, as providers will be able to work closer to their needs. In addition, maximising the potential of the service delivery infrastructure will help operators in making every service profitable and valuable, thus enabling faster ROI and a whole new set of revenue opportunities.
Through its distinct competencies, Sytel Reply assists clients in realising the benefits and dealing with the impacts of the disrupting technologies on their environments. Sytel Reply leverages real-world experience in SDN & NFV consulting for the TMT market, having worked with global Telco providers and established strong relationships with all major SDN vendors.