Technical white paper HPN SDN Controller Link Discovery
HPN SDN Controller Link Discovery
This document is intended for sales support and networking professionals who wish to configure their networks for successful HPN SDN Controller link discovery. This document will give a deeper understanding of how link discovery is performed and some recommended configurations.
How OpenFlow Link Discovery works
The HPN SDN Controller injects and observes packets in the controlled network to discover links between OpenFlow instances, Discovered links may be either one of the following types:
•Direct
Links which span from one OpenFlow instance port to another, with no intermediate switches.
•Multi-hop
Links which span from one OpenFlow instance port to another, traversing intermediate uncontrolled switches. An uncontrolled switch is a switch which does not have OpenFlow instances defined or connected to the controller (or team) which is attempting to discover the link.
The HPN SDN Controller discovers links and distinguishes link type by injecting two packets to each port in an OpenFlow instance. These packets have the same Ethernet type (0x8999), but are sent to different destination MAC addresses. The content of these packets is proprietary, but generally includes identification of the OpenFlow instance and port where the packet originated. The packets are injected immediately after the switch connects to the controller and periodically thereafter.
The HPN SDN Controller does not have access to information regarding vlan or port configuration of the switches that are hosting the OpenFlow instances it controls. Therefore, these generated packets do not contain an 802.1Q header, since port and OpenFlow instance vlan configuration would be required to construct the correct vlan tag.
The following are sample packets injected for link discovery:
Direct discovery packet sample:
The controller OpenFlow Link Discovery application listens for these packets from the destination datapaths.
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