Challenges and design choices to network FPGAs and servers for high-speed data acquisition or retrieval. We discuss TCP/IP as a very fast transport when using TCP/IP full accelerators, in the sensor-side FPGA and in the server.
Distributed Systems-of-Systems which, for example, connect smart sensor hubs with centralized processing via Ethernet, require very low transport latencies in order to deliver short response times. This makes it difficult for system designers to evaluate. And, things get worse if the measurement setup and methodology is not clearly explained, neither can be reproduced. Therefore, in this Technical Brief we describe how we use the Questa Advanced Simulator from Siemens EDA to measure network latency and analyze latency in a network protocol processing system. And, we also provide the most recent latency values for NPAP, the TCP/IP Stack from Fraunhofer HHI which is, as it turns out, very competitive with other solutions. Being integrators ourselves, we believe we owe this to the FPGA ecosystem!
We all observe a growing need to connect computers with each other with shorter delays (i.e. lower latencies) and higher bandwidth, in particular for High-Performance Computing (HPC) in the data center and in embedded systems such as advanced industrial robotics or autonomous vehicles, requiring the so-called deterministic networking. Processing of TCP/IP based network protocols at speeds of 10 Gbps and beyond demand kernel bypass solutions (such as Intel’s DPDK or Solarflare’s/Xilinx’ Onload or Mellanox/NVida VMA) and/or so-called TOEs (TCP Offload Engines).
Domain-Specific Architectures (DSA) use so-called heterogeneous computing elements, also known as Cores with the objective to put the compute burden where it belongs. This is a well established approach going back to the early days when an x86 CPU was partnered with an x87 for better floating-point processing. Today, it is common to deploy various flavors of Cores, for example:
This is because such (special purpose) fixed-function or programmable function accelerator Cores are optimized for a particular domain and, when properly used, not only take processing load off the (general purpose) CPU but also deliver better overall performance (which is data processed per time) and better efficiency (which is performance per Watt).
Over the following pages we will make a case for processing TCP/IP over TSN over 10/25/50/100 Gigabit Ethernet on dedicated Cores which has significant advantages in particular for real-time Ethernet and Deterministic Networking. These so-called TCP-TSN-Cores can be integrated either in FPGAs or in SoCs (ASIC and ASSP). As we will show, TCP-TSN-Cores are more than just a TOE – the commonly used approach for network protocol acceleration. By running the entire network protocol stack from OSI Layer 2 to at least Layer 4 in a dedicated integrated circuit – a so-called Full Accelerator – we can remove (general purpose) CPUs entirely from the datapath.
Hence, TCP-TSN-Cores can deliver very low bounded and deterministic latency with predictable scalability needed for 10/25/50/100 Gigabit Deterministic Networking.
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