Q

Previous page
Table of content
Next page

jabber

Random, malformed frames of data that are sent continuously by failed circuitry in a networking component.

Overview

A network interface card (NIC) or other device that is jabbering generates a continuous stream of unwanted signals that can disrupt communication between other devices on the network. This is especially common on Ethernet networks, in which each device must compete for use of the line using the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) contention protocol. When a NIC jabbers on an Ethernet network, all network communication might cease until the offending NIC is replaced. Other causes of jabbering on a network include loose cabling or a poorly grounded cable (for shielded cabling).

Jabbering can also occur in Fast Ethernet networks, in which a combination of 100BaseT4 and 100BaseTX cabling schemes are employed in one network. The continuously generated idle stream signal of the TX network can appear to the T4 network as jabber and can bring down the entire network. This should not be a problem if all network devices implement autonegotiation in an IEEE-compliant fashion. In addition, Fast Ethernet repeaters generally implement jabber control by automatically disconnecting any port that transmits information in streams longer than 40 kilobits (Kb).

The term jabber is also used in the Institute of Electrical and Electronic Engineers (IEEE) 802.3 specification for any frame of data that exceeds the maximum frame length for that specification. For Ethernet networks, the maximum frame length is 1518 bytes (18 bytes of overhead and 1500 bytes of payload). A frame longer than 1518 bytes is often called a jabber frame. Another name for jabber is long packet error .

Notes

A frame shorter than 64 bytes on an Ethernet network is called a runt frame.

See Also Carrier Sense Multiple Access with Collision Detection (CSMA/CD) ,Ethernet ,Fast Ethernet ,frame

jack

A receptacle into which you can insert a connector or plug to form a connection.

Overview

The best example of a jack in computer networking is the standard RJ-45 jack in which a connector (plug) on the end of a Category 5 (Cat5) cable can be inserted. RJ-45 jacks are typically built into Ethernet networking devices such as hubs, switches, and routers, but some devices also allow modular jacks to be inserted and removed in order to support other kinds of connectors. Patch panels and wall plates are other examples of items that may either be hardwired with RJ-45 jacks or allow modular jacks to be inserted into them for greater flexibility.

Jack. Example of a modular RJ-45 jack.

Notes

The terms connector, jack, and plug have some overlap and are often used interchangeably. Some vendors use plug to refer to the male connector and jack to refer to the female, but others use the terms male jacks and female jacks .

See Also cabling ,Category 5 (Cat5) cabling ,Ethernet

jacket

The outer covering of cabling that protects it from physical damage.

Overview

A cable's jacket protects the wiring from various kinds of damage, including damage caused by

The jacket is usually made of an insulating material, although its primary purpose is not insulation. (This function is provided by the insulation of individual wires within the jacket.) Common materials used for cable jackets include the following:

See Also cabling

jam signal

A signal sent by a device on an Ethernet network to indicate that a collision has occurred on the network.

Overview

Collisions occur on Ethernet networks because access to media (usually a cable) is based on contention-that is, stations on the network transmit on a first-come, first-served basis. If two stations attempt to take control of the medium at the same time and begin transmitting, both stations will detect each other's signal and realize that a collision has occurred. The two stations then issue a jam signal, which notifies all other stations on the network of the collision. They all must wait a short period of time before attempting to transmit again. The length of time is random for each station so that the retransmissions will not cause more collisions. The jam signal sent by one transmitting station must start with a 62-bit pattern of alternating 0s and 1s, followed by a 32-bit sequence that provides a dummy checksum value for the other transmitting station. This 32-bit sequence cannot be equal to the cyclical redundancy check (CRC) value for the frame preceding the jam.

See Also Carrier Sense Multiple Access with Collision Detection (CSMA/CD) ,collision ,Ethernet ,

Java

An object-oriented programming language developed by Sun Microsystems.

Overview

Java was designed to reduce the amount of time needed to build robust, scalable object-oriented applications. Java is a powerful object-oriented programming (OOP) platform like C and C++, but it has several advantages over these languages, including

History

Version 1 of Sun's Java Developer Kit (JDK) was released in 1995 at the company's SunWorld conference. Although a full-featured programming language, this initial release was especially popular with Web developers, who used Java to build applets that could be embedded in Hypertext Markup Language (HTML) pages to enhance the user experience by providing interactive content. With the release of JDK 1.1 in 1997, Sun added support for database connectivity and other features that made Java a more powerful and attractive programming environment for developing server-side applications.

JDK 1.2 was released in 1999, and incorporated the Java Foundation Classes (JFC) into Java's core run-time libraries. JDK 1.2 also provided a number of other enhancements that made Java a more scalable and secure platform. As a result of these improvements, Sun renamed the platform Java2 with this release of the JDK. Later in 1999, Sun made the Java2 platform available to developers in three versions: Java2 Standard Edition (J2SE), Java2 Enterprise Edition (J2EE), and Java2 Micro Edition (J2ME). These editions are discussed in the Implementation section of this article.

The current release of Java is the JDK 1.3 version of Java2. The Java specification is currently controlled by Sun through its Java Community Process (JCP) initiative.

Uses

Although Java was originally designed for developing full-fledged enterprise applications, much of its initial appeal came from its ability to create applets that could be downloaded from Web sites by browsers. These applets would then run on the browser to provide interactive elements such as advanced user interfaces and exciting display elements such as rotating ad banners and animated stock tickers.

As Java has grown to include more enterprise features such as database connectivity and server-side execution elements, it has evolved into a popular platform for the development of commercial e-business applications that is widely used in today's enterprise and business world.

Architecture

When you write an application (or applet) in Java, the Java compiler takes your source code (which is usually saved with the extension .java) and compiles it into something called bytecode. Bytecode is not true machine code-it is a set of generic instructions that are not specific to any particular hardware platform or operating system. Bytecode files generally have the extension .class and are referred to as class files. Here is a simple example of a Java application called HelloThere.java:

Class HelloThere {   Public static void main (String args[]) {     System.out.println("Hello there");   } }

The HelloThere.java program defines a new class called HelloThere and contains only one method: main(). When this program is compiled into the class file HelloThere.class and then run, it displays the text "Hello there" on the screen (the standard output device).

To run the application (class file), you must have a bytecode interpreter called a Java Virtual Machine (JVM) on the system. The JVM reads your application's bytecode and executes it by converting each bytecode instruction into a machine-native instruction or set of instructions. This translation process takes place regardless of whether the particular piece of bytecode has been previously executed. If the application is an applet, the Web browser that accesses it must have a JVM installed. The use of a bytecode interpreter instead of a "true" compiler, which generates platform-specific machine code, means that applications written in Java are often slower than those written in C or C++, but the ease of development and portability of code offset these disadvantages in most cases. To obtain additional functionality, you can link native code to Java applications.

The JVM has special security features built into it to ensure that any malicious Java applet downloaded from the Internet cannot perform any harmful actions on the user's system. In this sense, you can consider the JVM running in the Web browser a "sandbox" that allows the applet to execute safely while preventing access to certain items, such as the client machine's file system.

Implementation

The Java2 specification is currently available from Sun in three different developer platforms:

Some other key Java terminology includes the following:

Marketplace

Java2 Micro Edition (J2ME) is emerging as a popular platform for developing distributed applications for the next generation of third-generation (3G) cellular communication systems. A consortium of over 20 industry partners, including Sun, Ericsson, Motorola, Nokia, and Siemens, has developed the Mobile Internet Device (MID) profile, a platform for developing interactive mobile services that is based on J2ME. The J2ME platform complements the existing Wireless Application Protocol (WAP) platform and uses WAP as its underlying transport mechanism. Motorola's iDEN handset was the first commercially available mobile device compliant with the J2ME specification. A popular platform for creating J2EE applications is Code Warrior from Metrowerks.

Java in the enterprise has recently been furthered by Sun's new Java Web Start (JWS) platform. JWS simplifies the deployment of applications developed with Java 2 Enterprise Edition (J2EE) to network clients. This is done packaging all the various components of a Java application into a Java Archive (JAR) file, which can be downloaded and installed on client machines through a simple click of a link on a Web page. JWS also automates the process of upgrading Java applications on client machines, lowering the costs of deploying and managing Java desktop applications across an enterprise.

Prospects

Java has established itself in the enterprise market and is widely used for developing server-side applications for e-business. The Java community includes more than 2.5 million developers, a tribute to the platform's ease of use and reliability. On the client side, however, the original expectation of Java transforming the Internet through dynamic interactive content has faded somewhat. The biggest prospect for Java's future is likely to be in the embedded device field, where it competes with platforms such as Wireless Markup Language, QUALCOMM's Binary Runtime Environment for Wireless (BREW), and Microsoft Corporation's Windows CE. In the near future, Java is likely to find its main competition to be Microsoft's new .NET platform with its powerful C# programming language.

For More Information

Visit Sun Microsystems Java site at java.sun.com

See Also C# , .NET platform

Java Database Connectivity (JDBC)

A data access interface developed by Sun Microsystems that allows Java applications to access information stored in databases.

Overview

The Java Database Connectivity (JDBC) application programming interface (API) is a standard component of Java 2 Enterprise Edition (J2EE) development platform. The JDBC API specifies a set of Java classes that represent database connections, Structured Query Language (SQL) queries and their result sets, and other objects associated with accessing databases. Multiple drivers for JDBC exist that allow access to different database formats, and the JDBC drivers themselves can be implemented either within applets or as native methods on the operating system. JDBC also supports drivers that act as a bridge between Open Database Connectivity (ODBC) and JDBC. This type of driver translates JDBC function calls into native ODBC calls, but this bridge cannot be run by distrusted applets within a Web browser environment.

Notes

JDBC is to the Java platform what ODBC is to Microsoft Windows.

See Also application programming interface (API) , open database connectivity (ODBC), Structured Query Language (SQL)

Java Online Analytical Processing (JOLAP)

A Java-based interface for online analytical processing (OLAP) databases.

Overview

Java Online Analytical Processing (JOLAP) provides an interface for accessing, storing, and managing metadata stored in OLAP databases. JOLAP is intended to provide a uniform, platform-independent method for allowing clients to interact with OLAP servers. Just as the Java Database Connectivity (JDBC) specification allows data stored in relational databases to be accessed using Java, JOLAP provides similar functionality for accessing metadata stored in OLAP systems.

The JOLAP specification is an initiative of a company called Hyperion and is backed by an industry consortium that includes IBM, Oracle Corporation, and Sun Microsystems.

Notes

Microsoft Corporation's own specification for accessing OLAP systems is known as OLE DB.

See Also OLE DB ,online analytical processing (OLAP)

JavaScript

A scripting language developed for the Web by Netscape.

Overview

JavaScript is a cross-platform, object-based scripting language that is similar to C but much simpler in syntax. JavaScript was developed by Netscape Communications (now just Netscape) and built into the Netscape Navigator Web browser version 2 and later. JavaScript enables Web developers to produce Web pages with dynamic functionality such as animated graphics, browser detection, cookies, scrolling text, form handlers, and authentication without having to write or invoke Common Gateway Interface (CGI) applications. JavaScript can be used to develop both client and server applications, but it is usually run on the client Web browser.

The European Computer Manufacturers Association (ECMA) based its ECMA-262 standard upon both Netscape's JavaScript 1.1 and Microsoft's JScript 2 scripting languages. This ECMA-standardized scripting language is known as ECMAScript, and JavaScript 1.5 fully complies with the ECMA 262 standard.

Examples

JavaScript scripts are placed in standard Hypertext Markup Language (HTML) files using special tags. Here is a simple example:

<HTML> <HEAD><TITLE>Javascript Test</TITLE></HEAD> <BODY> <H1>Knock Knock</H1> <SCRIPT LANGUAGE="JavaScript"> alert("Who's there?"); </SCRIPT> </BODY> </HTML>

The <SCRIPT> and </SCRIPT> tags identify and contain the actual JavaScript script. When this page is loaded into a Web browser such as Netscape Navigator version 3, the browser reads the script and interprets it, causing an alert dialog box to be displayed with the message "JavaScript Alert: Who's there?" and an OK button that closes the dialog box when clicked.

Notes

JavaScript is not the same as Java, which is an object- oriented programming language. A syntactically similar scripting language called JScript is supported on Microsoft Internet Explorer.

See Also Java ,JScript scripting

Java Server Pages (JSP)

A technology from Sun Microsystems for creating dynamic Web applications.

Overview

Java Server Pages (JSP) is a Java-based technology that is part of the Java 2 Enterprise Edition (J2EE) specification from Sun Microsystems. JSP can be used to write server-side Web applications that dynamically generate Hypertext Markup Language (HTML) pages when accessed through a Web browser. Like the underlying Java programming environment on which it is based, JSP is a platform-independent, vendor-neutral development architecture that provides full access to Java's features, including standard Java APIs, Java servlets, and Java Database Connectivity (JDBC).

JSP also complements another Java server-side Web programming architecture called Java Servlets. Using JSP, you can include portions of Java code within an HTML page to call external Java components from the page. Java supports both tag-based programming similar to that used by Macromedia's Cold Fusion platform and embedded script blocks such as those used by Microsoft Corporation's Active Server Pages (ASP) platform.

Architecture

JSP separates the presentation (display of HTML pages) layer from the business logic layer, simplifying the process of creating portable, scalable Web-based applications. JSP has a simple syntax that can be used to write applications that run on Web servers and dynamically generate Web content in response to requests from Web browsers. An example of a simple "Hello World" application written in JSP might be as follows:

<HTML> <HEAD><TITLE>Sample JSP Application</TITLE> </HEAD> <BODY> <% String guest = request.getParameter("name"); if (guest == null) guest = "World"; %> Hello <%= guest %> </BODY> </HTML>

In this example, a form on a Web page could request the user to input his or her name, which would then be passed as a parameter to the JSP application on the Web server. For example, if the user's name is Mary and the form uses the GET method, the Name parameter would be passed to the JSP application (which might be called Hello.jsp) by appending it to the URL, for example:

http://www.microsoft.com/JSPtest/Hello.jsp?name=Mary

The client-side browser would then display a simple dynamically generated Web page that says "Hello Mary." If the user instead submitted the form without specifying a name, the browser would display simply "Hello World."

Marketplace

JSP has established itself as a popular platform for developing dynamic Web applications. As a server-side development platform, JSP competes in the commercial and enterprise environments with many similar platforms, including Macromedia's Cold Fusion, Personal Home Pages (PHP), the CGI/PERL combination popular in the UNIX world, and Microsoft Corporation's ASP platform.

For developers who want to create JSP applications, a variety of integrated development environments (IDEs) is available, including JRun and DreamWeaver UltraDev from Macromedia, and WebGain Studio from WebGain.

See Also Active Server Pages (ASP) , Hypertext Markup Language (HTML) ,

JBOD

Stands for "just a bunch of disks" and refers to an unstructured high-capacity disk-storage system.

Overview

A JBOD is essentially just an array of disks connected to a common backplane and arranged within an enclosure. The disks within the JBOD are usually controlled by an attached server called the host server, which may manage them as independent volumes or combine them into logical volumes in any way desired. JBODs are used anywhere a large amount of storage capacity is required but do not provide the fault tolerance of redundant array of independent disks (RAID) systems.

JBODs are more difficult to manage than Storage Area Networks (SANs) and Network Attached Storage (NAS) systems. As they rapidly expand their network, companies often implement JBODs without planning, creating storage management headaches for administrators. On the plus side, JBODs are cheaper to implement than SANs and can quickly provide additional network storage when needed.

Architecture

There is no one standard JBOD architecture. In its simplest form, a JBOD can be constructed by chaining together a series of external Small Computer System Interface (SCSI) disk drives, removable Jaz drives, optical drives, or any mixture of drives. In enterprise environments, Fibre Channel JBODs are more common; they generally have dual-loop DB9 copper interfaces and can be connected easily to a Fibre Channel hub or switch to provide additional network storage. Fibre Channel JBODs typically range from small 8-disk enclosures to large rackmount form factors that include several hot-swappable modules, each of which may contain 20 or more disks.

See Also Fibre Channel ,network attached storage (NAS) ,Small Computer System Interface (SCSI) ,storage ,storage area network (SAN)

JDBC

Stands for Java Database Connectivity, a data access interface developed by Sun Microsystems that allows Java applications to access information stored in databases.

See Also Java Database Connectivity (JDBC)

Jet

Stands for Joint Engine Technology, a database engine technology used in various Microsoft products.

See Also Joint Engine Technology (Jet)

Jini

An on-demand networking architecture developed by Sun Microsystems.

Overview

Jini is designed to provide a simple way of spontaneously creating networks without the need to install drivers or configure network parameters. It provides an underlying infrastructure that allows a wide range of devices to connect to one another as needed to perform specific tasks. Jini devices can automatically discover, recognize, and form federations or communities with one another spontaneously without user intervention. Jini devices are always on and establish impromptu networks as needed. Jini can be implemented on a wide range of devices, including not only computing platforms such as PCs, Personal Digital Assistants (PDAs), and cell phones, but also VCRs and DVD players, stereo systems, copiers, thermostats, and security systems.

Jini is based on Java technology from Sun and can be implemented on any device running the Java Virtual Machine (VM). Java is the key enabler of Jini technology, and, like Java, is a fundamental component of the Sun Open Network Environment (Sun ONE) initiative.

Architecture

Jini's basic underlying architecture involves two components:

Jini uses a distributed architecture in which no single central server is needed. Jini devices can federate to form spontaneous communities without the need to have a central PC controlling them. For example, a Jini-enabled PDA and cell phone could communicate with each other when the user accesses the cell phone to dial a phone number. The cell phone could automatically network with the PDA using Jini to look up the phone number.

For More Information

Find out more about Jini at www.sun.com/jini.

See Also Java

jitter

Distortion in transmission that occurs when a signal drifts from its reference position.

Overview

Jitter is inherent in all forms of communication because of the finite response time of electrical circuitry to the rise and fall of signal voltages. An ideal digital signal would have instantaneous rises and falls in voltages and would appear as a square wave on an oscilloscope. The actual output of a digital signaling device has finite rise and fall times and appears rounded when displayed on the oscilloscope, which can result in phase variation that causes loss of synchronization between communicating devices.

Jitter can also be caused by variations in the timing or the phase of the signal in an analog or digital transmission line. In this instance, jitter can be caused by poor connectors, malfunctioning repeaters, transient problems in switches, and variations in transmission characteristics of cabling. Jitter typically results in a loss of data because of synchronization problems between the transmitting stations, especially in high-speed transmissions. The goal in designing a transmission device is to ensure that the jitter remains within a range that is too small to cause appreciable data loss.

Jitter is different from a related concept called delay. Delay is the amount of time for a signal to reach its destination, but jitter represents unevenness in delay. For example, when you download a file from the Internet using File Transfer Protocol (FTP), the delay between transmission of packets from the FTP server to the client is typically several hundred milliseconds, but, due to jitter in the connection, the first half of the file may download much more quickly than the last half.

Jitter is particularly annoying in multimedia communications involving audio or video streaming. Jitter can render a communication unintelligible, and it can cause dropouts unless buffering is used to prevent them. Buffering introduces delay, however, and although this may be acceptable in one-way streaming transmission, it is unacceptable in two-way communications.

See Also noise ,latency ,signal

join

A database operation that allows you to retrieve and modify data from more than one table at a time using a single Structured Query Language (SQL) SELECT statement.

Overview

You can use the Microsoft Query Analyzer tool for Microsoft SQL Server to graphically create joins for transact-SQL queries that join two or more tables or join a table to itself. Joins are a necessity because a single table might not provide all the information you want to retrieve about a specific database entity. By connecting tables using joins, you can retrieve information that resides in more than one table in a single operation.

You can create three kinds of joins:

Notes

There are two kinds of syntax for creating joins, ANSI join syntax and SQL Server join syntax. You can use only one of these types of syntax in a given SELECT statement.

See Also database ,Structured Query Language (SQL)

Joint Engine Technology (Jet)

A database engine technology used in various Microsoft products.

Overview

Jet is an advanced 32-bit multithreaded database engine developed by Microsoft Corporation in 1992. The Jet database engine is employed in several Microsoft products, including Microsoft Exchange, Microsoft Access, Microsoft Visual Basic, and Active Directory directory service for Microsoft Windows 2000. The Jet engine is not available as a separate product.

Architecture

The Jet database engine employs transaction logs to track and maintain information and provide fault tolerance. Native Jet database files usually have the extension .mdb. Jet databases can be accessed using Data Access Objects (DAO) and open database connectivity (ODBC). DAO provides the Component Object Model (COM) interface for accessing indexed sequential access method (ISAM) databases such as Microsoft FoxPro, dBASE, or Paradox through Jet. Jet databases are best accessed through DAO (rather than ODBC) because they expose only a limited amount of functionality to ODBC drivers. Jet cannot use ODBC to build queries that use server-side cursors, and it has limited capability for stored procedures and multiple result sets.

See Also Component Object Model (COM) ,Data Access Objects (DAO) ,Exchange Server ,open database connectivity (ODBC)

JOLAP

Stands for Java Online Analytical Processing or Java OLAP, a Java-based interface for OLAP databases.

See Also Java Online Analytical Processing (JOLAP)

JScript

Microsoft Corporation's implementation of the ECMAScript standard.

Overview

JScript is an interpreted object-based Web scripting language originally developed as Microsoft's counterpart to Netscape's JavaScript scripting language. JScript was designed to allow Web developers to easily add dynamic, interactive content to static Hypertext Markup Language (HTML) pages.

JScript is a superset of the ECMA-262 specification, a standard for cross-platform, vendor-neutral scripting languages developed by the European Computer Manufacturers Association (ECMA). JScript fully complies with the ECMAScript standard and also includes advanced features that make it a powerful scripting tool for the Microsoft Windows platform. In particular, JScript allows Component Object Model (COM) objects such as ActiveX controls to be called from within scripts and executed using the Windows Scripting Host (WSH), enabling the full power of the Windows operating system to be accessed.

Architecture

JScript is an interpreted programming language that is executed at run time. JScript files use the extension .js to identify themselves to WSH for execution. JScript supports standard programming elements such as statements, variables, constants, operators, conditionals, loops, functions, and arrays. It also supports a limited number of objects and methods. JScript supports six different data types including the variant data types. The language is thus loosely typed, meaning you do not have to declare a variable's data type before you use the variable. JScript has limited file input/output (I/O) features.

You can execute scripts written in JScript in several ways:

In the third scenario above, JScript is typically used to add functionality to HTML files stored on a Web server. When a Web browser such as Microsoft Internet Explorer accesses a page containing an embedded block of JScript script, it downloads the block of script and executes it locally on the client machine. Internet Explorer can do this because it has a built-in scripting engine that can understand and interpret scripts written in JScript and Microsoft Visual Basic, Scripting Edition (VBScript).

Examples

The following is a simple example of an embedded script written in JScript. The script is embedded in an HTML page between the <SCRIPT> and </SCRIPT> tags and displays a confirm message box when the user opens the file using Internet Explorer. When the user makes a selection, the remaining portion of the page loads.

<HTML> <BODY> <H1>Welcome to our restaurant!</H1> <HR> <SCRIPT> var testing=window.confirm("Click OK for food, Cancel for drink."); if (testing) {     window.alert("Hot dog"); } else window.alert("Beer"); </SCRIPT> <H1>Thanks for coming!</H1> </BODY> </HTML>

JScript. A dialog box created using JScript.

Notes

Unlike its cousin VBScript, JScript is a case-sensitive language.

For More Information

Visit the Microsoft Windows Script Technologies site at msdn.microsoft.com/scripting.

You can find the ECMA-262 specification at www.ecma.ch/stand/ecma-262.htm.

See Also JavaScript ,scripting ,Windows Script Host (WSH)

JSP

Stands for Java Server Pages, a technology from Sun Microsystems for creating dynamic Web applications.

See Also Java Server Pages (JSP)

jumbo frames

A feature of Gigabit Ethernet (GbE) that allows frames up to 9 kilobytes (KB) in size.

Overview

Standard 10Base5 Ethernet, created in the early 1980s, supports frames up to 1.5 KB in length. This standard has been supported by all subsequent versions of Ethernet, including 10BaseT Ethernet, Fast Ethernet, and GbE. Unfortunately, for the speeds of 1 gigabit per second (Gbps) supported by GbE, these standard frames become inefficient, and better performance can be achieved at these speeds by using larger frames. Consequently, the designers of the 802.3z GbE standard included support for jumbo frames as an option for gigabit networking.

Implementation

Jumbo frames can have payloads up to 9 KB in length and can result in much higher network utilizations for activities such as file transfers, where utilization of over 80 percent is achievable when using jumbo frames compared to typically under 20 percent when using standard Ethernet frames. Unfortunately, using jumbo frames adds issues of interoperability for enterprise networks, as these frames are not supported by slower 10 and 100 megabits per second (Mbps) versions of Ethernet. Since performing Layer-2 fragmentation and reassembly of jumbo frames is not a desirable solution, two standard methods are generally employed to incorporate GbE jumbo frames into typical enterprise networks:

While Internet Protocol (IP) can intrinsically support frames of even larger size up to 64 KB (and IPv6 can support frames up to 4 gigabytes [GB] in length!) and using such monster frames could make gigabit networking even more efficient, there is an inherent obstacle to using such large frames. Ethernet uses a 32-bit cyclical redundancy check (CRC) at the end of each frame, and this error correction method is only efficient for frames up to about 12,000 bytes in length. The reason for choosing 9 KB as the maximum length for jumbo frames is to ensure the efficiency of such error correction while making possible the transmission of 8-KB Network File System (NFS) datagrams without the need of fragmentation.

Marketplace

Use of jumbo frames is increasing in enterprise networking environments. Vendors such as Nortel Networks offer autonegotiating 10/100/1000BaseT network interface cards (NICs) that feature support for jumbo frames to make implementing this feature in the enterprise easier.

See Also 802.3z ,Ethernet ,Fast Ethernet ,frame ,Gigabit Ethernet (GbE)

JXTA

A peer-to-peer (P2P) networking initiative from Sun Microsystems.

Overview

Project JXTA (pronounced "juxta") is an outgrowth of work by Sun to extend and standardize P2P technology in computer networking. The JXTA architecture is designed to support heterogeneous systems and platforms from all levels, from enterprise servers to handheld personal devices. JXTA is designed to simplify P2P networking by providing a set of general, open protocols for communications between different kinds of devices including PCs, Personal Digital Assistants (PDAs), cell phones, and other devices. The aim of Project JXTA is to explore and advance the new paradigm of distributed computing popularized by the P2P movement.

JXTA is part of the Sun Open Network Environment (Sun ONE) initiative that includes the companion technologies Java and Jini. JXTA technology is licensed from Sun under the Sun Project JXTA Software License, which is based on version 1.1 of the open- source Apache Software License.

For More Information

Find out more about JXTA at www.jxta.org

See Also Java ,Jini


Previous page
Table of content
Next page
Microsoft Encyclopedia of Networking
Microsoft Encyclopedia of Networking
ISBN: 0735613788
EAN: 2147483647
Year: 2002
Pages: 36
Authors: Mitch Tulloch, Ingrid Tulloch
BUY ON AMAZON
ERP and Data Warehousing in Organizations: Issues and Challenges
VBScript Programmers Reference
Cisco IP Telephony (CIPT) (Authorized Self-Study) (2nd Edition)
802.11 Wireless Networks: The Definitive Guide, Second Edition
Cultural Imperative: Global Trends in the 21st Century
VBScript in a Nutshell, 2nd Edition
flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net
Privacy policy