WAN SDN Controller

Intro

Right now we don't need to spend much to realize an idea. With Cloud service delivery we don't need to setup server stack just to test an application prototype instead we can use cloud service like AWS lamda.

Cloud service delivery models also impacting the Communication Service Provider (CSP)'s services offering outlook. Enterprise demand CSP to be more agile turning up the service. Previously the service delivery model was CSP providing fixed pipe of bandwidth to enterprise in turn, enterprise will pay fixed price for the service. 

The service model looks simple fixed bandwidth for fixed price, actually it is like that because the  difficulty that CSP face to provide value added services ie: bandwidth calendaring, bandwidth on-demand with the legacy MPLS infrastructure which normally deployed by CSP. The difficulty lies on manual labor to align multiple CSP's organizations from planning, operation and customer service not to mention the IT/OSS departement to provide proper billing for such service.

By allowing applications to consume IT resources on-demand, cloud technologies have fundamentally changed the way datacenters (DCs) are being designed and operated. Software Defined Networking (SDN) extends the cloud model to the network by allowing applications to consume network connections as quickly and as easily as they consume virtualized compute and storage. In an SDN-based DC network, connections are not permanent entities; they are initiated by virtual machines in seconds, and are dismantled when no longer required. 

As the cloud expands to encompass multiple DCs and users across metro and wide area networks (MANs and WANs), applications will expect the carrier network connections that underpin this new, distributed cloud fabric to leverage SDN and be just as easy to set up and consume. 

As mentioned before Cloud service delivery change the way the CSP design and operate its network fundamentally. Software Defined Networking (SDN) initially introduced in Data Center (DC) environment by allowing the applications to quickly consume the resources like networks connections, virtualized compute and storage. Hence, the services can be build in seconds and collapsed in seconds. When the cloud service expanded to multiple DCs across WAN, the application will expect the carrier network connections that underpin this new, distributed cloud fabric to leverage SDN and be just as easy to set up and consume. 

What is WAN SDN Controller?

Achieving SDN in the WAN is no trivial task.  While DCs are simple, homogeneous and can count on essentially limitless bandwidth, carrier networks are complex, multi-vendor, and are subject to many technology and bandwidth constraints. Any attempt to introduce a faster and more automated way of provisioning the WAN must work in concert with provisioning systems for existing services. The dynamic consumption nature of distributed clouds and their users will put significant pressure on operational models designed for static and predictable traffic patterns. SPs will need to augment existing traffic engineering processes with a dynamic resource management capability that can ensure network efficiency, resiliency and availability in the face of rapidly changing cloud connectivity needs.

The industry has already begun the process of evolving SDN for carrier networks with proposals to abstract and open the proprietary packet/optical layer to external control using OpenFlow. While this is a good starting point, little value can be realized without a broader SDN framework that can provision and correlate topology, resource and constraint information across multiple layers – including packet/optical, Ethernet, IP and IP VPNs. Only a multi-layer SDN framework has the global visibility and universal control necessary to deliver on the SDN promise of increased network agility, efficiency and scale. 

Verizon's SDN & NFV Reference Architecture, has realized the vision to provide. it is Published is Published early 2016 by Collaboration between Verizon, Alcatel-Lucent, Nokia, Ericsson, Cisco, HP, Samsung, Intel and Red Hat which capture following Key points:

• Captured NFV MANO and SDN in a single architecture
• Recognized the end-to-end orchestration is more than just NFVO
• Recognized the difference between DC SDN and WAN SDN
• Showed an evolution of traditional EMSs to new management systems

WAN SDN Control entity - in general, a WAN SDN controller must accomplish the following objectives:

• Northbound APIs for network abstraction and programmability to be used by customer facing orchestration systems and third-party applications 
• Model-driven Adaptation Layer that allows network service models to help drive north bound and south bound mappings 
• Multi-layer and multi-vendor control 
• Automated management of end-to-end services
• Resource optimization 
• Topology discovery and rectification
• Statistics collection and processing 
• Provide a control interface to hybrid/classical control mechanisms

The following figure depicts the functional elements of WAN SDN Controller

WAN SDN Controller Use Case

The following are the use cases that is possible by the framework.

Optimal Path-Selection:

• Flow steering
• Egress peer engineering
• Enhanced quality of experience
• Enhanced ECMP

Automated Service Fulfillment:

• Simplified OSS and operation
• Cross layer correlation
• Zero touch configuration

Bandwidth and Link Management:

• Tactical path provisioning
• Tactical bandwidth provisioning
• Run the network hotter, unlock the stranded bandwidth

Assurance:

• Analytics driven optimization
• Telemetry
• Fault and alarm correlation
• Offline traffic engineering tool