End-to-end synchronization in packet switched networks

The provision of real time services through a Packet Switched Network, requires the adoption of end-to-end synchronization methods. Several of these methods, are compared and a specific hardware solution is discussed. Results obtained through a specially designed Simulation Programme are included, for several network time delay jitter distributions and synchronization methods. These results are used to evaluate systems and design parameters

Võrguaja protokolli serveri arenduse ja toimivuse analüüs

Käesolev magistritöö kirjeldab lihtsa võrguaja protokolli (NTP) serveri ehitamist monoplaatarvutisse Tartu Observatooriumi aatomikella tarbeks. See selgitab NTP-protokolli terminoloogiat ja on loodud NTP-serveri ja kliendi jaoks. Mõõtmise eesmärgil kirjeldatakse ka seda, kuidas ehitatatakse NTP-klienti, mis genereerib impulssi sekundis, mis põhineb NTP-kellaajale. Selle kasutamise tulemusi võrreldakse NTP plotteri testitulemustega. Seejärel hinnatakse NTP-serveri eksperimentaalset konfiguratsiooni, millele järgneb arutelu võimalike paranduste ja tulevaste projektide üle.This Master thesis describes the process of building a simple network time protocol (NTP) server on a single-board computer for the Atomic clock at Tartu Observatory. It explains the terminology of NTP protocol and set up for the NTP server. It also describes how to build a NTP client which generates pulse per second by its own script for the measurement purposes. This new pulse is synchronized with the NTP timestamp. Results of its use are compared against the test results from NTP plotter. The experimental configuration of the NTP server is then evaluated which is followed by a discussion regarding possible improvements and future projects

Trigger and Timing Distributions using the TTC-PON and GBT Bridge Connection in ALICE for the LHC Run 3 Upgrade

The ALICE experiment at CERN is preparing for a major upgrade for the third phase of data taking run (Run 3), when the high luminosity phase of the Large Hadron Collider (LHC) starts. The increase in the beam luminosity will result in high interaction rate causing the data acquisition rate to exceed 3 TB/sec. In order to acquire data for all the events and to handle the increased data rate, a transition in the readout electronics architecture from the triggered to the trigger-less acquisition mode is required. In this new architecture, a dedicated electronics block called the Common Readout Unit (CRU) is defined to act as a nodal communication point for detector data aggregation and as a distribution point for timing, trigger and control (TTC) information. TTC information in the upgraded triggerless readout architecture uses two asynchronous high-speed serial links connections: the TTC-PON and the GBT. We have carried out a study to evaluate the quality of the embedded timing signals forwarded by the CRU to the connected electronics using the TTC-PON and GBT bridge connection. We have used four performance metrics to characterize the communication bridge: (a)the latency added by the firmware logic, (b)the jitter cleaning effect of the PLL on the timing signal, (c)BER analysis for quantitative measurement of signal quality, and (d)the effect of optical transceivers parameter settings on the signal strength. Reliability study of the bridge connection in maintaining the phase consistency of timing signals is conducted by performing multiple iterations of power on/off cycle, firmware upgrade and reset assertion/de-assertion cycle (PFR cycle). The test results are presented and discussed concerning the performance of the TTC-PON and GBT bridge communication chain using the CRU prototype and its compliance with the ALICE timing requirements

Recent Trends in Communication Networks

In recent years there has been many developments in communication technology. This has greatly enhanced the computing power of small handheld resource-constrained mobile devices. Different generations of communication technology have evolved. This had led to new research for communication of large volumes of data in different transmission media and the design of different communication protocols. Another direction of research concerns the secure and error-free communication between the sender and receiver despite the risk of the presence of an eavesdropper. For the communication requirement of a huge amount of multimedia streaming data, a lot of research has been carried out in the design of proper overlay networks. The book addresses new research techniques that have evolved to handle these challenges

Theories and Models for Internet Quality of Service

We survey recent advances in theories and models for Internet Quality of Service (QoS). We start with the theory of network calculus, which lays the foundation for support of deterministic performance guarantees in networks, and illustrate its applications to integrated services, differentiated services, and streaming media playback delays. We also present mechanisms and architecture for scalable support of guaranteed services in the Internet, based on the concept of a stateless core. Methods for scalable control operations are also briefly discussed. We then turn our attention to statistical performance guarantees, and describe several new probabilistic results that can be used for a statistical dimensioning of differentiated services. Lastly, we review recent proposals and results in supporting performance guarantees in a best effort context. These include models for elastic throughput guarantees based on TCP performance modeling, techniques for some quality of service differentiation without access control, and methods that allow an application to control the performance it receives, in the absence of network support