Tip of the Day: Demystifying Software Defined Networking Terms - The Cloud Compass: SDN Data Flows

Today’s Tip…

Today’s tip continues the series, Demystifying Software Defined Networking Terms with part three, The Cloud Compass.  In this tip we will explore a common theme as we introduce terms used to describe traffic flows in a Windows Server 2016 Software Defined Network datacenter.  Both management and workload data traffic will be considered, as well as a few related terms.

Part 3: The Cloud Compass

Terms in this tip include:

  • East-West Traffic Flow
  • North-South Traffic Flow
  • Southbound Interface/API
  • Northbound Interface/API
  • Traffic Shaping
  • Representational State Transfer (REST)
  • Open Management Infrastructure (OMI)

The Cloud Compass – Management and Data Flows

East-West – East-West refers to traffic flows that occur between devices within a datacenter.  During convergence for example, routers exchange table information to ensure they have the same information about the internetwork in which they operate.  Another example are switches, which can exchange spanning-tree information to prevent network loops.

Network virtualization itself has led to a modest increase in the amount of East-West traffic found in the datacenter.  For example, the traffic generated by a network controller communicating with physical or virtual network devices; routers, switches, appliances, and so on.

North | South – North- South refers to traffic flows into and out of the datacenter.  Traffic entering the datacenter through perimeter network devices is said to be southbound.  Traffic exiting via the perimeter network devices is said to be northbound.

Northbound Interface/API – In SDN, a northbound interface allows a particular component on a network, such as a network controller, to communicate with a higher-level component.  The Network Controllers Northbound Interface is implemented as a Representational State Transfer (REST) API, often referred to as the REST API, or just the Northbound API.   

The Network Controller Northbound API provides you with the ability to gather network information from Network Controller and use it to monitor and configure the network.  The Network Controller Northbound API can be used to configure, monitor, troubleshoot, and deploy new devices on the network by using Windows PowerShell, (programmatically using) the Representational State Transfer (REST) API, or a management application with a graphical user interface, such as System Center Virtual Machine Manager.

Southbound API – In SDN, the main function of the Southbound Interface is to enable communication between the SDN controller and the network nodes (both physical and virtual switches and routers) so that the router can discover network topology, define network flows and implement requests relayed to it via northbound APIs

Windows Server 2016’s Network Controller communicates with network devices, services, and components by using the Southbound API.   With the Southbound API, Network Controller can discover network devices, detect service configurations, and gather all of the information needed about the network.  In addition, the Southbound API gives Network Controller a pathway to send information to the network infrastructure, such as configuration changes that have been made. 

Multiple protocols can be implemented to support southbound operation including Open Management Infrastructure stack (OMI), Desired State Configuration (DSC), and Simple Network Management Protocol (SNMP), among others.


Figure: SDN Fabric/Device Discovery, Configuration, Management, and Monitoring

Related Technologies

Now that we’ve mapped out datacenter traffic flows, let’s take a moment to define two of the standards introduced above.

Representational State Transfer (REST) - Representational State Transfer (REST) is a programming architectural implementation intended to increase the efficiency of communication in computing systems.  It embodies the idea that the best way to share large amounts of data between multiple parties is to make that data available on-demand by sharing references to that data rather than a complete copy of the data itself.   Systems which implement REST are called 'RESTful' systems.

The Network Controller Northbound API is implemented as a REST interface.

Open Management Infrastructure (OMI) - Open Management Infrastructure or OMI (formerly known as NanoWBEM) is a standards-based open source management technology seeing a growing adoption rate due to its potential to solve the problems associated with datacenters having a large number of heterogeneous devices supplied by different hardware and platform vendors, each requiring different tools and management processes.

For more information, see Jeffrey Snover’s informative blog, Open Management Infrastructure at https://blogs.technet.microsoft.com/windowsserver/2012/06/28/open-management-infrastructure/

In tomorrow’s tip, Demystifying Software Defined Networking Terms – Part 4: The Technologies