A plurality of computer nodes communicate using seemingly random Internet Protocol source and destination addresses. Data packets matching criteria defined by a moving window of valid addresses are accepted for further processing, while those that do not meet the criteria are quickly rejected. Improvements to the basic design include (1) a load balancer that distributes packets across different transmission paths according to transmission path quality; (2) a DNS proxy server that transparently creates a virtual private network in response to a domain name inquiry; (3) a large-to-small link bandwidth management feature that prevents denial-of-service attacks at system chokepoints; (4) a traffic limiter that regulates incoming packets by limiting the rate at which a transmitter can be synchronized with a receiver; and (5) a signaling synchronizer that allows a large number of nodes to communicate with a central node by partitioning the communication function between two separate entities.

Agile network protocol for secure communications with assured system availability

A secure domain name service for a computer network is disclosed that includes a portal connected to a computer network, such as the Internet, and a domain name database connected to the computer network through the portal. The portal authenticates a query for a secure computer network address, and the domain name database stores secure computer network addresses for the computer network. Each secure computer network address is based on a non-standard top-level domain name, such as .scom, .sorg, .snet, .snet, .sedu, .smil and .sint.

Agile network protocol for secure communications using secure domain names

A technique is disclosed for establishing a secure communication link between a first computer and a second computer over a computer network. Initially, a secure communication mode of communication is enabled at a first computer without a user entering any cryptographic information for establishing the secure communication mode of communication. Then, a secure communication link is established between the first computer and a second computer over a computer network based on the enabled secure communication mode of communication. The secure communication link is a virtual private network communication link over the computer network in which one or more data values that vary according to a pseudo-random sequence are inserted into each data packet.

Method for establishing secure communication link between computers of virtual private network

White Rabbit (WR) is the project name for a ambiguous project that uses Ethernet as both, deterministic (synchronous) data transfer and timing network. The presented design aims for a general purpose, fieldbus like transmission system, which provides deterministic data and timing to approximately 1000 timing stations. The main advantage over conventional systems is the highly accurate timing (sub-nanosecond range) without restrictions on the traffic schedule and an upper bound for the delivery time of high priority messages. In addition, WR also automatically compensates for transmission delays in the fibre links, which are in the range of 10 km length. It takes advantage of the latest developments on synchronous Ethernet and IEEE 1588 to enable the distribution of accurate timing information to the nodes saving noticeable amounts of bandwidth.

White rabbit: Sub-nanosecond timing distribution over ethernet

Clock synchronization is a prerequisite for the realization of emerging applications in various domains such as industrial automation and the intelligent power grid. This paper surveys the standardized protocols and technologies for providing synchronization of devices connected by packet-switched networks. A review of synchronization impairments and the state-of-the-art mechanisms to improve the synchronization accuracy is then presented. Providing microsecond to sub-microsecond synchronization accuracy under the presence of asymmetric delays in a cost-effective manner is a challenging problem, and still an open issue in many application scenarios. Further, security is of significant importance for systems where timing is critical. The security threats and solutions to protect exchanged synchronization messages are also discussed.

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A Survey of Clock Synchronization Over Packet-Switched Networks

This paper analyzes the factors that affect the synchronization performance in peer-to-peer precision time protocol (PTP). We first study the influence of frequency drift in the absence of jitter and compare the gravity of the master drift with that of the slave drift. Then, we study the influence of jitter under the assumption of constant frequencies and the effect of averaging. The analytic formulas provide a theoretical ground for understanding the simulation results, some of which are presented, as well as the guidelines for choosing both system and control parameters.

Synchronization Performance of the Precision Time Protocol in Industrial Automation Networks

This paper analyzes the factors that affect the synchronization performance in using the precision time protocol (FTP). We first study the influence of jitter under the assumption of no frequency drifts. Then we study the influence of frequency drift in the absence of jitter. The analytic formulas provide a theoretical ground for the understanding of simulation results as well as guidelines for choosing both system and control parameters when applying FTP.

Synchronization Performance of the Precision Time Protocol

A method for time synchronization in a communications network having multiple nodes, wherein the nodes comprise a first node and at least one second node, where the first node generates first cycle counter states according to a reference clock frequency and the second node or nodes each generate second cycle counter states according to an internal clock frequency, where a time synchronization is carried out in sequential synchronization cycles, in which synchronization messages originating from the first node are sequentially transmitted from one node to another node, and a synchronization message transmitted by a node contains information used for time synchronization in the at least one second node receiving the synchronization message such that a time synchronization is performed in a given second node based on an estimation of a first cycle counter state and a compensation factor in combination with a linear quadratic regulator.

Method for Time Synchronization in a Communications Network

The invention relates to a communication station (S32-S34), which as a passive station in a communication system which is not authorized to transmit but listens in on all communication processes and can receive only data (D) actually intended for it, which fact can be conclusively verified by means of a destination point code (T) assigned to the data (D). According to the invention, said communication station is additionally upgraded to receive data (D), the destination (T) and originating point code (S) of which matches an entry (FT, FS) in a filter table (F) provided for in a communication station (S32-S34) which has been upgraded in accordance with the invention.

Audio-active communication stations, communication method and communication system with audio-active communication stations

In accordance to one aspect, a method for optimizing the effective data transmission rate in a bus system, in particular in automation technology is provided. A data telegram used in higher-order data networks based on the Internet protocol, with at least one data telegram, at least one data segment and/or at least one data section being generated and/or modified and/or deleted by at least one slave. The topology of the bus system can hereby be selected according to the application and is taken into account in the configuration of the data contained in the data telegrams, without infringing the protocol characteristics of the higher-order data network. The number of data telegrams required is hereby significantly reduced, in particular on communication links with maximum loading.

Günter Steindl

Papers

Synchronization Performance of the Precision Time Protocol in Industrial Automation Networks

Synchronization Performance of the Precision Time Protocol

Method for Time Synchronization in a Communications Network

Audio-active communication stations, communication method and communication system with audio-active communication stations

Method for optimizing bandwidth utilization in bus systems