Knowledge Base

Titlesort descending Authors Last Update Category
A General-Purpose API for iWARP and InfiniBand Dr. Robert Russell

Remote Direct Memory Access (RDMA) allows data to be transferred over a network directly from the memory of one computer to the memory of another computer without CPU intervention. There are two major types of RDMA hardware on the market today: InfiniBand, and RDMA over IP, also known as iWARP. This hardware is supported by open software that was developed by the OpenFabrics Alliance (OFA) and that is known as
the OpenFabrics Enterprise Distribution (OFED) stack. This stack provides a common interface to both types of RDMA hardware, but does not itself provide a general-purpose API that would be convenient to most network programmers. Rather, it supplies the tools by which such APIs can be constructed.
The Extended Sockets API (ES-API) is a specification published by the Open Group that defines extensions to the traditional socket API which include two major new features necessary to exploit the advantages of RDMA hardware and the OFED stack: asynchronous I/O and memory registration.

The UNH-EXS interface is a multi-threaded implementation of the ES-API plus additional extensions, which enables programmers to utilize RDMA hardware via the OFED stack in a convenient, relatively familiar manner. The UNH-EXS interface is implemented entirely in user space on the Linux operating system. This provides easy porting, modification and adoption of UNH-EXS, since it requires no changes to existing Linux kernels. We present results on the performance of some benchmark applications using the UNH-EXS interface on both iWARP and InfiniBand hardware.

December 13, 2012 White Papers
A Performance Study to Guide RDMA Programming Decisions Patrick MacArthur and Dr. Robert Russell

This paper describes a performance study of Remote Direct Memory Access (RDMA) programming techniques. Its goal is to use these results as a guide for making "best practice" RDMA programming decisions. Infiniband RDMA is widely used in scientific high performance computing (HPC) clusters as a low-latency, high-bandwidth, reliable interconnect accessed via MPI. Recently it is gaining adherents outside scientific HPC as high-speed clusters appear in other application areas for which MPI is not suitable. RDMA enables user applications to move data
directly between virtual memory on different nodes without operating system intervention, so there is a need to know how to incorporate RDMA access into high-level programs. But RDMA offers more options to a programmer than traditional sockets programming, and it is not always obvious what the performance tradeoffs of these options might be. This study is intended to provide some answers.

January 18, 2013 White Papers
Advanced Digital Signal Processing and Noise Reduction Saeed V. Vaseghi

From the back cover: "Signal processing and noise reduction are at the core of telecommunications and information processing systems. With the increasing use of digital cellular mobile systems in a variety of adverse environments, noise reduction is becoming a particularly important aspect of communication system design. This second edition provides a thoroughly revised and expanded introduction to the fundamentals of random processes, Bayesian modelling, and noise reduction. The subject is covered in a graphical and mathematically accessible manner with the emphasis on Bayesian inference and its application to noise reduction."

June 26, 2012 Recommended Textbooks
Advantages and Testing Considerations of a Converged DCB Network Presentation Peter J. Scruton

Peter participated in the 2012 Ethernet Technology Summit in San Jose, California as a panelist in one of the Sessions. The Session focus was on the Continuing Role of Ethernet in Storage.

December 4, 2012 External Links
An Efficient Method for Stream Semantics over RDMA P. MacArthur and R. Russell

Most network applications today are written to use TCP/IP via sockets. Remote Direct Memory Access (RDMA) is gaining popularity because its zero-copy, kernel-bypass features provide a high throughput, low latency reliable transport. Unlike TCP, which is a stream-oriented protocol, RDMA is a message-oriented protocol, and the OFA verbs library for writing RDMA application programs is more complex than the TCP sockets interface. UNH EXS is one of several libraries designed to give applications more convenient, high-level access to RDMA features. Recent work has shown that RDMA is viable both in the data center and over distance.

One potential bottleneck in libraries that use RDMA is the requirement to wait for message advertisements in order to send large zero-copy messages. By sending messages first to an internal, hidden buffer and copying the message later, latency can be reduced at the expense of higher CPU usage at the receiver. This paper presents a communication algorithm that has been implemented in the UNH EXS stream-oriented mode to allow dynamic switching between sending transfers directly to user memory and sending transfers indirectly via an internal, hidden buffer depending on the state of the sender and receiver. Based on preliminary results, we see that this algorithm performs well under a variety of application requirements.

May 21, 2014 White Papers
An ITU-T G.994.1 Protocol Analysis Tool For ADSL Matthew Langlois (UNH-IOL), Dr. Michael Carter, Dr. William Lenharth, and Scott Valcourt

One of the most commonly deployed DSL variants is ADSL. Despite this fact, deployment of new robust and reliable ADSL services is increasingly difficult due, in part, to the physical limitations of the copper telephone system infrastructure, and also in part to the lack of useful ADSL network debugging tools. ADSL service providers and technicians currently lack a device capable of decoding physical layer signaling and displaying actual physical layer parameters and statistics associated with a live ADSL connection, independent of the end stations. Similar devices used in other network technologies are often referred to as protocol analyzers. The intent of this paper is to illustrate how Matlab [1], in conjunction with a DSP or a PC, can be used to create an effective ADSL handshaking protocol analyzer based on ITU-T G.994.1 (G.hs) [2]. G.hs conformance is critical in establishing a successful ITU-T G.992.1 (G.dmt) [3] based ADSL connection.

November 4, 2002 White Papers
Basics of DSL Bonded Physical Layer Testing Lincoln Lavoie (UNH-IOL)

An overview to DSL Bonded Physical Layer Testing.

February 24, 2012 Tutorials
BER Testing: How Many Bits Are Enough? Andy Baldman

The purpose of this article is to discuss the concept of Bit Error Ratio testing, and will explain, using a minimum amount of math, the answer to the fairly common question: "How many bits do I need to send in order to verify that a devices exceeds a given BER?"

June 29, 2012 Theses
Broadband Forum Kieffer Quitayen

Broadband Forum is an international industry consortium of nearly 200 leading service providers, equipment manufacturers and other interested parties, focused on developing the full potential of broadband DSL to meet the needs of the mass market.

June 26, 2012 External Links
CERN - High Speed Interconnect Server

Browse through some of the technologies and functions used in high-performance data acquisition systems for high-energy physics experiments.

April 13, 2005 External Links