Beacons

A beacon is an intentionally conspicuous device designed to attract attention to a specific location.

 

Beacons can also be combined with semaphoric or other indicators to provide important information, such as the status of an airport, by the colour and rotational pattern of its airport beacon or of pending weather as indicated on a weather beacon mounted at the top of a tall building or similar site. When used in such fashion, beacons can be considered a form of optical telegraphy.

 

Usage

· For Navigation – Beacons help guide navigators to their destinations. Types of navigational beacons include radar reflectors, radio beacons, sonic and visual signals.

· For defensive communications – Classically, beacons were fires lit at well-known locations on hills or high places, used either as lighthouses for navigation at sea, or for signalling over land that enemy troops were approaching, in order to alert defenses. As signals, beacons are an ancient form of optical telegraphy, and were part of a relay league.

· On vehicles – Vehicular beacons are rotating or flashing lights affixed to the top of a vehicle to attract the attention of surrounding vehicles and pedestrians. Emergency vehicles such as fire engines, ambulances, police cars, tow trucks, construction vehicles, and snow-removal vehicles carry beacon lights.

 

In wireless networks, a beacon is a type of frame which is sent by the access point (or wifi router), to indicate that is on.

 

Beaconing is the process that allows a network to self-repair network problems. The stations on the network notify the other stations on the ring when they are not receiving the transmissions. Beaconing is used in Token ring and FDDI networks.

Telnet

Telnet is a network protocol used on the Internet or local area networks to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. User data is interspersed in-band with Telnet control information in an 8-bit byte oriented data connection over the Transmission Control Protocol (TCP).

 

Telnet was developed in 1969 beginning with RFC 15, extended in RFC 854, and standardized as Internet Engineering Task Force (IETF) Internet Standard STD 8, one of the first Internet standards.

 

Historically, Telnet provided access to a command-line interface (usually, of an operating system) on a remote host. Most network equipment and operating systems with a TCP/IP stack support a Telnet service for remote configuration (including systems based on Windows NT).

 

The term telnet also refers to the software that implements the client part of the protocol. Telnet client applications are available for virtually all computer platforms.

 

Security

Experts in computer security, such as SANS Institute, recommend that the use of Telnet for remote logins should be discontinued under all normal circumstances, for the following reasons:

 

· Telnet, by default, does not encrypt any data sent over the connection (including passwords), and so it is often practical to eavesdrop on the communications and use the password later for malicious purposes; anybody who has access to a router, switch, hub or gateway located on the network between the two hosts where Telnet is being used can intercept the packets passing by and obtain login, password and whatever else is typed with a packet analyzer.

· Most implementations of Telnet have no authentication that would ensure communication is carried out between the two desired hosts and not intercepted in the middle.

· Several vulnerabilities have been discovered over the years in commonly used Telnet daemons.

 

It is of note that there are a large number of industrial and scientific devices which have only Telnet available as a communication option. Some are built with only a standard RS-232 port and use a serial server hardware appliance to provide the translation between the TCP/Telnet data and the RS-232 serial data. In such cases, SSH is not an option unless the interface appliance can be configured for SSH.

Jini

Jini, also called as Apache River, is network architecture for the construction of distributed systems in the form of modular co-operating services.

Jini technology is a service-oriented architecture that defines a programming model which exploits and extends Java technology to enable the construction of secure, distributed systems consisting of federations of well-behaved network services and clients. Jini technology can be used to build adaptive network systems that are scalable, evolvable and flexible as typically required in dynamic computing environments. Jini offers a number of powerful capabilities such as service discovery and mobile code. Jini is similar to Java Remote Method Invocation but more advanced.

The term Jini refers to a set of specifications and an implementation; the latter is referred to as the Jini Starter Kit. Both the specifications and the Starter Kit have been released under the Apache 2.0 license and have been offered to the Apache Software Foundation's Incubator.

Jini provides facilities for dealing with some of the fallacies of distributed computing, problems of system evolution, resilience, security and the dynamic assembly of service components. Code mobility is a core concept of the platform and provides many benefits including non-protocol dependence.

One of the goals of Jini is to shift the emphasis of computing away from the traditional file-system–oriented approach to a more network-oriented approach. Thus resources can often be used across a network as if they were available locally. Jini allows for advanced searching for services through a process of discovery of published services (making Jini akin to the service-oriented architecture concept).

There are three main parts to a Jini scenario. These are the client, the server, and the lookup service.

The service is the resource which is to be made available in the distributed environment. This can include physical devices (such as printers or disk drives) and software services (for example a database query or messaging service). The client is the entity which uses the service. Jini provides a mechanism for locating services on the network that conform to a particular (Java) interface. Once a service is located, the client can download an implementation of that interface, which it then uses to communicate with the service.

The three major components that make up a running Jini system are

1.  The Jini Client—Anything that would like to make use of the Jini service

2. The Service Locator—Anything that acts as a Locator/Trader/Broker between the service and the client, and is used to find services in a distributed Jini system.

The Jini Service—Any entity that can be used by a client program or another service (for example, a printer, a DVR (this used to say "VCR" - that's how old this software is), or a software entity like an EJB service)