Ferdy Hanssen

RTnet: a distributed real-time protocol for broadcast-capable networks

RTnet is a distributed real-time network protocol, to be used on fully-connected local area networks with a broadcast capability. It supports on-the-fly addition and removal of network nodes, resource-lavish and resource-lean devices, streaming real-time and regular non-realtime traffic. It allows the use of standard real-time scheduling paradigms to control network traffic, allows dynamic scheduling and is flexible in stream handling. The design is presented, together with measurement results of an experiment with an implementation on top of Ethernet

Multimedia QoS in low-cost home networks

This paper describes a new mechanism to guarantee quality of service for multimedia streams in low-cost home networks. Quality of service is based on a token, of which the route in the network is determined by a distributed scheduler. The network node that has the token-the active node-can send its data during a predetermined period. The length of this period and which the node gets the token next is calculated by the scheduler in the active node. Every node has a scheduler on-board and schedules streams according to stream information from other nodes-contained in the token-and its own streams. Although other types of scheduler could be used, the token scheduler deploys a preemptive earliest deadline first strategy. This guarantees a theoretical maximum bandwidth utilization of 100 percent. The network is simulated and a prototype is built, based on low-cost ethernet hardware. Results show a high throughput with a small overhead of less than one percent per stream.

Scheduling of early quantum tasks

An Early Quantum Task (EQT) is a Quantum EDF task that has shrunk its first period into one quantum time slot. Its purpose is to be executed as soon as possible, without causing deadline overflow of other tasks. We derive the conditions under which an EQT can be admitted and can have an immediate start. The advantage of scheduling EQTs is shown by its use in a buffered multimedia server. The EQT is associated with a multimedia stream and it will use its first invocation to fill the buffer, such that a client can start receiving data immediately.

Verifying the Distributed Real-Time Network Protocol RTnet Using Uppaal

RTnet is a distributed real-time network protocol for fully-connected local area networks with a broadcast capability. It supports streaming real-time and non-realtime traffic and on-the-fly addition and removal of network nodes. This paper presents a formal analysis of RTnet using the model checker Uppaal. Besides normal protocol behaviour, the analysis focuses on the fault-handling properties of RTnet, in particular recovery after packet loss. Both qualitative and quantitative properties are presented, together with the verification results and conclusions about the robustness of RTnet.

An in-home digital network architecture for real-time and non-real-time communication

This paper describes an in-home digital network architecture that supports both real-time and non-real-time communication. The architecture deploys a distributed token mechanism to schedule communication streams and to offer guaranteed quality-of-service. Essentially, the token mechanism prevents collisions to occur in the network, thus making the network deterministic. The distributed token scheduler uses a preemptive earliest deadline first strategy, which guarantees a possible bandwidth utilization of 100 percent. To allow non-realtime communication however, only part of the available bandwidth is allocated by the scheduler to real-time traffic, typically 80 percent. The paper describes protocols to counter token loss and token duplication. The network is simulated and the paper shows some results from this simulation. Based on low-cost Ethernet hardware, a prototype of the network is built and tested. Lastly, the paper describes future directions.