DHD System in Heterogenous Networks

Today, computer networks are used for a great variety of applications. Office printer sharing, access to file servers, streaming of audio and video and also control data for embedded systems (as DHD devices are) run on the same network infrastructure. Because these networks are so diverse in their use of protocols, they are often called heterogenous networks.

Nodes on such a network are often PCs running Windows, but there can also be printers, networked disc drives running Unix or Linux. All these devices use different protocols based on TCP/IP and UDP. In most cases, this works trouble-free. However, if a DHD device is connected to such a mixed network and if the level of UDP traffic becomes too high, this may cause problems for the DHD device. Here is why: Since DHD systems use UDP broadcasts for exchanging control information, each individual network controller must inspect all incoming UDP packets with a broadcast address. This also includes packets from other nodes on the network, for instance Windows PCs announcing their file sharing services. A DHD device will only react to packets from other DSP cores or from DHD software applications. Nevertheless, it has to inspect every incoming UDP packet, even if it was not sent by a DHD device or DHD software. This inspection uses up computing power on the network controller.

Under certain circumstances, a high level of incoming UDP traffic thus can cause buffer overflow within the network controller. This happens even if the data in the UDP packets is not used! In turn, this can cause delays in the processing of the main tasks of the controller. In rare extreme cases, a very high and lasting level of incoming UDP traffic may cause a shutdown of the Ethernet interface on the network controller and instability of the entire module.

Therefore, you should urgently avoid to run a DHD device within a network with foreign UDP traffic.