We appear to be moving into an era where ICT is “software-defined” and typically offered “as a Service.” This is especially true for enterprise networks although the concept can be extended to computing, storage and transmission as well.
The first page of a Google search for “software-defined” includes the following:
- Software-defined Networking (SDN)
- Software-defined Radio (SDR)
- Software-defined Data Center (SDDC)
- Software-defined Storage (SDS)
- Software-defined Cloud Networking (SDCN)
The Open Networking Foundation (ONF) defines SDN as:
“The physical separation of the network control plane from the forwarding plane, and where a control plane controls several devices.”
In fact, this could be generalized to: The physical/virtual separation of the control subsystem from the functional (processing/storage/networking/device) subsystems, and where the control subsystem controls several functional subsystems.
One of the key messages of a recent symposium hosted by the University of Toronto and sponsored by HP is that software has become the facilitator for a new generation of highly flexible, agile networks. This is leading to innovative new products and a more standard, simplified infrastructure.
What makes being software-defined so important? Some of the “-ility” characteristics for SDN (based on the ONF description) are:
- Agility – Network managers can dynamically adjust network-wide traffic flows to meet changing needs without having to separately re-configure routers;
- Programmability – Network control functions are easier to program as a result of both the centralization and the separation of control from processing;
- Manageability – Network intelligence in the (logically) centralized SDN controllers can maintain a global view of the network and can appear to applications and policy engines as a single, logical switch;
- Configurability – Network managers can more easily and more dynamically configure, manage, secure, and optimize network resources;
- Interoperability – An SDN using open standards can simplify network design and operation since forwarding instructions are provided by the SDN controllers instead of multiple, vendor-specific devices and protocols;
- Protectability – Robust security and privacy policies and controls can be applied to SDN network elements in an automated and consistent network-wide fashion.
The essence of the SDN architecture is to divide the network into three subsystems (usually called layers):
- Application Layer – provides user applications with programmatic interfaces to the network services regardless of the underlying resources; OpenStack is one implementation of such an interface;
- Control Layer – provides a separate programmable facility for the control and management of the network infrastructure;
- Infrastructure Layer – provides open standards-based interfaces to the basic IT resources (networks, computing and storage); OpenFlow is an example.
Software-driven networks and management systems are not really new – separation of the control plane has been used in older telco networks and almost all network hardware includes some form of software (e.g., microcode or firmware). SDN’s, however, add a new level of automation that spans vendors and devices and facilitates service automation and dynamic management. This allows managers to re-focus from managing bytes and packets to managing the overall “quality of experience.” It can also support the rapid service delivery and elastic capacity required for cloud environments.
Mobility is also one of the driving forces for software-defined networking. Some of the network requirements for mobility are:
- devices are always connectible regardless of location and network technology (including access to wired services);
- seamless connectivity across different network types (WiFi, Cell, WLAN, LAN and Internet);
- service feature consistency (e.g., user id, geoloation);
- end-to-end security across all networks;
- infrastructure resource integration;
- multi-vendor, multi-device multi-owner, multi-jurisdiction capabilities and support.
The U of T Symposium referred to earlier covered various SDN and mobility topics from both the research and planning viewpoints. Presentations included:
- Software-defined Data Center
- Wireless into the Future
- Multimedia and Security in Wireless Networks
- Wireless apps in the age of IEEE802.11ac and cloud
- New directions in networking research
- SDN – Architecting your Next Gen Network
Some of my personal conclusions from the Symposium, after having listened to the various speakers, were:
- Software-defined Networks provide new opportunities for supplier competition;
- Different technologies are converging and need to provide consistent, integratable services;
- Security and management need to be architected using a holistic approach;
- Many new applications will benefit from the next set of advances in Mobility.