Technical white paper HPN SDN Controller Link Discovery

When the controller is configured for hybrid.mode=true, the controller installs a flow rule on every OpenFlow instance to steal these packets:

Packets which match this flow rule are forwarded to the controller from the OpenFlow instance and port where they were received. Using the origin information contained within the received packet, the controller derives the source and destination of the link that this packet traversed and records a link between the OpenFlow instances. The link type is derived from the destination MAC address of the packet (direct or multi-hop). If a link is direct, it will be discovered as both “direct” and “multi- hop” from the reporting OpenFlow instance, but the type of “direct” has precedence over the type of “multi-hop”, so the link is recorded as “direct”.

Keys to Correct Link Discovery

In order to ensure that the desired link topology is correctly discovered, configure the switches such that all OpenFlow instances are configured for the same vlan mapping throughout the topology AND one of the following conditions are met:

•The link discovery packet is correctly tagged by the OpenFlow instance when it egresses the port to which it is injected.

•The untagged link discovery packet is stolen to the controller by the correct OpenFlow instance agent on a switch when it is received.

Though the HPN SDN Controller link discovery method works well in many network configurations, there are some situations where links are not discovered as intended. This may include missing links, links with an incorrect type, or discovering a link where one should not exist. If the untagged discovery packets can’t be associated with the correct OpenFlow instance on the destination switch, then the discovery packet will be dropped or associated with the wrong OpenFlow instance. This can occur for reasons explained in the following sections, including ambiguous vlan association across all OpenFlow instances in the topology.

The consequences of link discovery problems will be observed as impacts to other functionality, such as node discovery or topology calculation. For instance, a missing link in the middle of the network may cause a node’s location to bounce from the edge of the network to the middle of the network.

Known issues

All known link discovery problems relate to one of the following situations:

•The received link discovery packet is dropped by a switch in the network, because the packet is untagged and received on a tagged-only port.

•The received link discovery packet is associated with the wrong OpenFlow instance, because the packet is untagged and received on a port which associates untagged packets with a vlan not in the OpenFlow instance. Another manifestation of this situation occurs when the OpenFlow instance configurations across all switches are not configured with the same vlan set and a discovery packet gets associated with only one OpenFlow instance (see switch C in the example below).

Vendors follow various interpretations in their association of vlans to OpenFlow instances. Various implementations allow a single vlan per OpenFlow instance, multiple vlans per OpenFlow instance, or all vlans in a single OpenFlow instance. Thus when the controller injects an untagged packet into an OpenFlow instance, the vlan association for the packet is sometime ambiguous in the OpenFlow instance.

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HP VAN SDN Controller Software Products manual Keys to Correct Link Discovery, Known issues
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VAN SDN Controller Software Products specifications

HP VAN SDN Controller Software Products represent a significant advancement in network management by leveraging software-defined networking (SDN) principles. These products aim to centralize control of network resources, provide enhanced automation, and simplify network management, which can dramatically improve the overall performance and agility of data centers.

One of the main features of HP VAN SDN Controller is its ability to enable an application-centric network environment. By separating the control plane from the data plane, network administrators can gain a holistic view of the entire network. This separation allows for dynamic reconfiguration of network devices and sets the stage for the development of innovative applications that can respond to real-time network conditions.

The controller supports OpenFlow as its primary protocol, ensuring interoperability with a wide range of network devices from different vendors. This compatibility facilitates a heterogeneous network environment, allowing organizations to transition to SDN at their own pace without needing to replace all existing hardware. It also promotes vendor diversity, reducing the risk of vendor lock-in.

HP VAN SDN Controller features robust security capabilities, including support for micro-segmentation, which helps in isolating critical components within the network. This layer of security can safeguard sensitive data and protect against threats, ensuring that only authorized traffic is allowed within designated network segments.

Another key characteristic is the controller's emphasis on automation and orchestration. Through APIs and built-in tools, network policies can be defined and applied consistently across the entire network. This intelligent automation reduces the potential for human error and accelerates the implementation of networking changes, enabling organizations to adapt quickly to evolving business needs.

The HP VAN SDN Controller also incorporates advanced analytics capabilities that provide real-time visibility into network performance. These analytics can help in troubleshooting, forecasting capacity needs, and optimizing resource utilization, contributing to improved operational efficiency and reduced downtime.

Furthermore, the scalable architecture of the HP VAN SDN Controller makes it suitable for various environments, from small enterprises to large-scale data centers. The product supports multi-tenancy, allowing multiple virtual networks to coexist on the same infrastructure, which can be ideal for service providers and organizations operating within cloud environments.

In summary, HP VAN SDN Controller Software Products deliver a powerful suite of features and technologies that enhance network control, security, automation, and scalability, positioning organizations to leverage the full potential of software-defined networking.
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