48,028 research outputs found
A Basic Result on the Superposition of Arrival Processes in Deterministic Networks
Time-Sensitive Networking (TSN) and Deterministic Networking (DetNet) are
emerging standards to enable deterministic, delay-critical communication in
such networks. This naturally (re-)calls attention to the network calculus
theory (NC), since a rich set of results for delay guarantee analysis have
already been developed there. One could anticipate an immediate adoption of
those existing network calculus results to TSN and DetNet. However, the
fundamental difference between the traffic specification adopted in TSN and
DetNet and those traffic models in NC makes this difficult, let alone that
there is a long-standing open challenge in NC. To address them, this paper
considers an arrival time function based max-plus NC traffic model. In
particular, for the former, the mapping between the TSN / DetNet and the NC
traffic model is proved. For the latter, the superposition property of the
arrival time function based NC traffic model is found and proved. Appealingly,
the proved superposition property shows a clear analogy with that of a
well-known counterpart traffic model in NC. These results help make an
important step towards the development of a system theory for delay guarantee
analysis of TSN / DetNet networks
NaNet: a Low-Latency, Real-Time, Multi-Standard Network Interface Card with GPUDirect Features
While the GPGPU paradigm is widely recognized as an effective approach to
high performance computing, its adoption in low-latency, real-time systems is
still in its early stages.
Although GPUs typically show deterministic behaviour in terms of latency in
executing computational kernels as soon as data is available in their internal
memories, assessment of real-time features of a standard GPGPU system needs
careful characterization of all subsystems along data stream path.
The networking subsystem results in being the most critical one in terms of
absolute value and fluctuations of its response latency.
Our envisioned solution to this issue is NaNet, a FPGA-based PCIe Network
Interface Card (NIC) design featuring a configurable and extensible set of
network channels with direct access through GPUDirect to NVIDIA Fermi/Kepler
GPU memories.
NaNet design currently supports both standard - GbE (1000BASE-T) and 10GbE
(10Base-R) - and custom - 34~Gbps APElink and 2.5~Gbps deterministic latency
KM3link - channels, but its modularity allows for a straightforward inclusion
of other link technologies.
To avoid host OS intervention on data stream and remove a possible source of
jitter, the design includes a network/transport layer offload module with
cycle-accurate, upper-bound latency, supporting UDP, KM3link Time Division
Multiplexing and APElink protocols.
After NaNet architecture description and its latency/bandwidth
characterization for all supported links, two real world use cases will be
presented: the GPU-based low level trigger for the RICH detector in the NA62
experiment at CERN and the on-/off-shore data link for KM3 underwater neutrino
telescope
Isolating SDN Control Traffic with Layer-2 Slicing in 6TiSCH Industrial IoT Networks
Recent standardization efforts in IEEE 802.15.4-2015 Time Scheduled Channel
Hopping (TSCH) and the IETF 6TiSCH Working Group (WG), aim to provide
deterministic communications and efficient allocation of resources across
constrained Internet of Things (IoT) networks, particularly in Industrial IoT
(IIoT) scenarios. Within 6TiSCH, Software Defined Networking (SDN) has been
identified as means of providing centralized control in a number of key
situations. However, implementing a centralized SDN architecture in a Low Power
and Lossy Network (LLN) faces considerable challenges: not only is controller
traffic subject to jitter due to unreliable links and network contention, but
the overhead generated by SDN can severely affect the performance of other
traffic. This paper proposes using 6TiSCH tracks, a Layer-2 slicing mechanism
for creating dedicated forwarding paths across TSCH networks, in order to
isolate the SDN control overhead. Not only does this prevent control traffic
from affecting the performance of other data flows, but the properties of
6TiSCH tracks allows deterministic, low-latency SDN controller communication.
Using our own lightweight SDN implementation for Contiki OS, we firstly
demonstrate the effect of SDN control traffic on application data flows across
a 6TiSCH network. We then show that by slicing the network through the
allocation of dedicated resources along a SDN control path, tracks provide an
effective means of mitigating the cost of SDN control overhead in IEEE
802.15.4-2015 TSCH networks
Improved Delay Bound for a Service Curve Element with Known Transmission Rate
Network calculus is often used to prove delay bounds in deterministic
networks, using arrival and service curves. We consider a FIFO system that
offers a rate-latency service curve and where packet transmission occurs at
line rate without pre-emption. The existing network calculus delay bounds take
advantage of the service curve guarantee but not of the fact that transmission
occurs at full line rate. In this letter, we provide a novel, improved delay
bound which takes advantage of these two features. Contrary to existing bounds,
ours is per-packet and depends on the packet length. We prove that it is tight.Comment: 4 pages, 2 figure
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