See Institute of Electrical and Electronics Engineers.
IEEE 1394, High Performance Serial Bus, is an electronics standard for connecting devices to your personal computer. IEEE 1394 provides a single plug-and-socket connection on which up to 63 devices can be attached with data transfer speeds up to 400 Mbps (megabits per second). The standard describes a serial bus or pathway between one or more peripheral devices and your computer's microprocessor. Many peripheral devices now come equipped to meet IEEE 1394. Two popular implementations of IEEE 1394 are Apple's FireWire and Sony's i.LINK. IEEE 1394 implementations provide:
* A simple common plug-in serial connector on the back of your computer and on many different types of peripheral devices.
* A thin serial cable rather than the thicker parallel cable you now use to your printer, for example
* A very high-speed rate of data transfer that will accommodate multimedia applications (100 and 200 megabits per second today; with much higher rates later).
* Hot-plug and Plug and Play capability without disrupting your computer.
* The ability to chain devices together in a number of different ways without terminators or complicated set-up requirements.
In time, IEEE 1394 implementations are expected to replace and consolidate today's serial and parallel interfaces, including Centronics parallel, RS-232C, and Small Computer System Interface (SCSI). The first products to be introduced with FireWire include digital cameras, digital video disks (DVDs), digital video tapes, digital camcorders, and music systems. Because IEEE 1394 is a peer-to-peer interface, one camcorder can dub to another without being plugged into a computer. With a computer equipped with the socket and bus capability, any device (for example, a video camera) can be plugged in while the computer is running.
Briefly How It Works:
There are two levels of interface in IEEE 1394, one for the backplane bus within the computer and another for the point-to-point interface between device and computer on the serial cable. A simple bridge connects the two environments. The backplane bus supports 12.5, 25, or 50 megabits per second data transfer. The cable interface supports 100, 200, or 400 megabits per second. Each of these interfaces can handle any of the possible data rates and change from one to another as needed.
The serial bus functions as though devices were in slots within the computer sharing a common memory space. A 64-bit device address allows a great deal of flexibility in configuring devices in chains and trees from a single socket.
IEEE 1394 provides two types of data transfer: asynchronous and isochronous . Asynchronous is for traditional load-and-store applications where data transfer can be initiated and an application interrupted as a given length of data arrives in a buffer . Isochronous data transfer ensures that data flows at a pre-set rate so that an application can handle it in a timed way. For multimedia applications, this kind of data transfer reduces the need for buffering and helps ensure a continuous presentation for the viewer.
The 1394 standard requires that a device be within 4.5 meters of the bus socket. Up to 16 devices can be connected in a single chain, each with the 4.5 meter maximum (before signal attenuation begins to occur) so theoretically you could have a device as far away as 72 meters from the computer.
Another new approach to connecting devices, the Universal Serial Bus (USB ), provides the same "hot plug" capability as the 1394 standard. It's a less expensive technology but data transfer is limited to 12 Mbps (million bits per second). Small Computer System Interface offers a high data transfer rate (up to 40 megabytes per second) but requires address preassignment and a device terminator on the last device in a chain. FireWire can work with the latest internal computer bus standard, Peripheral Component Interconnect (PCI ), but higher data transfer rates may require special design considerations to minimize undesired buffering for transfer rate mismatches.
See Internet Information Server.
IMAP - Internet Message Access Protocol:
See Internet Message Access Protocol.
Institute of Electrical and Electronics Engineers - IEEE:
The Institute of Electrical and Electronics Engineers (IEEE) describes itself as "the world's largest technical professional society -- promoting the development and application of electrotechnology and allied sciences for the benefit of humanity, the advancement of the profession, and the well-being of our members."
The IEEE fosters the development of standards that often become national and international standards. The organization publishes a number of journals, has many local chapters, and several large societies in special areas, such as the IEEE Computer Society.
Intel Hub Architecture:
Also see Accelerated Hub Achitecture.
Intellectual Property Core - IP Core:
An Intellectual Property (IP) core is a block of logic or data that is used in making a field programmable gate array (FPGA) or application-specific integrated circuit (ASIC) for a product. As essential elements of design reuse, IP cores are part of the growing electronic design automation (EDA) industry trend towards repeated use of previously designed components. Ideally, an IP core should be entirely portable - that is, able to easily be inserted into any vendor technology or design methodology. Universal Asynchronous Receiver/Transmitter (UARTs), central processing units (CPUs), Ethernet controllers, and PCI interfaces are all examples of IP cores.
IP cores fall into one of three categories: hard cores, firm cores, or soft cores. Hard cores are physical manifestations of the IP design. These are best for plug-and-play applications, and are less portable and flexible than the other two types of cores. Like the hard cores, firm (sometimes called semi-hard) cores also carry placement data but are configurable to various applications. The most flexible of the three, soft cores exist either as a netlist (a list of the logic gates and associated interconnections making up an integrated circuit) or hardware description language (HDL) code.
A number of organizations, such as the Free IP Project and Open Cores, have formed to promote open sharing of IP cores.
Interactive System Productivity Facility - ISPF:
Interactive System Productivity Facility (ISPF) is the user interface and supporting programs that come with IBM's OS/390 operating system and that allow a company to configure and manage its system, add new system or application programs and test them, and access system files (data sets). ISPF consists of the Dialog Manager (DM), the Program Development Facility (PDF), and the Software Configuration and Library Management (SCLM) facility.
IBM also offers an ISPF that will run on an OS/2 system so that developers can work "offline" from the OS/390.
Internet Control Message Protocol - ICMP:
Internet Control Message Protocol (ICMP) is a message control and error-reporting protocol between a host server and a gateway to the Internet. ICMP uses Internet Protocol (IP) datagrams, but the messages are processed by the IP software and are not directly apparent to the application user.
Internet Information Server - ISS:
Internet Information Server (ISS) is a group of Internet servers (including a Web or Hypertext Transfer Protocol server and a File Transfer Protocol server) with additional capabilities for Microsoft's Windows NT and Windows 2000 Server operating systems. IIS is Microsoft's entry to compete in the Internet server market that is also addressed by Apache , Sun Microsystems, O'Reilly, and others. With IIS, Microsoft includes a set of programs for building and administering Web sites, a search engine, and support for writing Web-based applications that access database s. Microsoft points out that IIS is tightly integrated with the Windows NT and 2000 Servers in a number of ways, resulting in faster Web page serving.
A typical company that buys IIS can create pages for Web sites using Microsoft's Front Page product (with its WYSIWYG user interface). Web developers can use Microsoft's Active Server Page (ASP)technology, which means that applications - including ActiveX control s - can be imbedded in Web pages that modify the content sent back to users. Developers can also write programs that filter requests and get the correct Web pages for different users by using Microsoft's Internet Server Application Program Interface (ISAPI) interface. ASPs and ISAPI programs run more efficiently than common gateway interface (CGI) and server-side include (SSI) programs, two current technologies. (However, there are comparable interfaces on other platforms.)
Microsoft includes special capabilities for server administrators designed to appeal to Internet service providers (ISP s). It includes a single window (or "console") from which all services and users can be administered. It's designed to be easy to add components as snap-ins that you didn't initially install. The administrative windows can be customized for access by individual customers. Microsoft has been criticized for IIS's susceptibility to computer virus attacks such as Code Red and Nimda.
Internet Message Access Protocol - IMAP:
Internet Message Access Protocol (IMAP) is a standard protocol for accessing e-mail from your local server. IMAP (the latest version is IMAP4) is a client/server protocol in which e-mail is received and held for you by your Internet server. You (or your e-mail client) can view just the heading and the sender of the letter and then decide whether to download the mail. You can also create and manipulate folders or mailboxes on the server, delete messages, or search for certain parts or an entire note. IMAP requires continual access to the server during the time that you are working with your mail.
A less sophisticated protocol is Post Office Protocol 3 (POP3 ). With POP3, your mail is saved for you in your mail box on the server. When you read your mail, all of it is immediately downloaded to your computer and no longer maintained on the server.
IMAP can be thought of as a remote file server. POP can be thought of as a "store-and-forward" service. POP and IMAP deal with the receiving of e-mail from your local server and are not to be confused with Simple Mail Transfer Protocol (SMTP ), a protocol for transferring e-mail between points on the Internet. You send e-mail with SMTP and a mail handler receives it on your recipient's behalf. Then the mail is read using POP or IMAP.
Internet Protocol - IP:
The Internet Protocol (IP) is the method or protocol by which data is sent from one computer to another on the Internet. Each computer (known as a host) on the Internet has at least one IP address that uniquely identifies it from all other computers on the Internet. When you send or receive data (for example, an e-mail note or a Web page), the message gets divided into little chunks called packets. Each of these packets contains both the sender's Internet address and the receiver's address. Any packet is sent first to a gateway computer that understands a small part of the Internet. The gateway computer reads the destination address and forwards the packet to an adjacent gateway that in turn reads the destination address and so forth across the Internet until one gateway recognizes the packet as belonging to a computer within its immediate neighborhood or domain. That gateway then forwards the packet directly to the computer whose address is specified.
Because a message is divided into a number of packets, each packet can, if necessary, be sent by a different route across the Internet. Packets can arrive in a different order than the order they were sent in. The Internet Protocol just delivers them. It's up to another protocol, the Transmission Control Protocol (TCP) to put them back in the right order.
IP is a connectionless protocol, which means that there is no continuing connection between the end points that are communicating. Each packet that travels through the Internet is treated as an independent unit of data without any relation to any other unit of data. (The reason the packets do get put in the right order is because of TCP, the connection-oriented protocol that keeps track of the packet sequence in a message.) In the Open Systems Interconnection (OSI) communication model, IP is in layer 3, the Networking Layer.
The most widely used version of IP today is Internet Protocol Version 4 (IPv4). However, IP Version 6 (IPv6 ) is also beginning to be supported. IPv6 provides for much longer addresses and therefore for the possibility of many more Internet users. IPv6 includes the capabilities of IPv4 and any server that can support IPv6 packets can also support IPv4 packets.
Internet Protocol Security - IPsec:
Internet Protocol Security (IPsec) is a developing standard for security at the network or packet processing layer of network communication. Earlier security approaches have inserted security at the application layer of the communications model. IPsec will be especially useful for implementing virtual private network s and for remote user access through dial-up connection to private networks. A big advantage of IPsec is that security arrangements can be handled without requiring changes to individual user computers. Cisco has been a leader in proposing IPsec as a standard (or combination of standards and technologies) and has included support for it in its network routers.
IPsec provides two choices of security service: Authentication Header (AH), which essentially allows authentication of the sender of data, and Encapsulating Security Payload (ESP), which supports both authentication of the sender and encryption of data as well. The specific information associated with each of these services is inserted into the packet in a header that follows the IP packet header. Separate key protocols can be selected, such as the ISAKMP/Oakley protocol. Officially spelled IPsec by the IETF, the term often appears as IPSec and IPSEC.
Internet Site Provider - ISP:
An Internet service provider (ISP) is a company that provides individuals and other companies access to the Internet and other related services such as Web site building and virtual hosting. An ISP has the equipment and the telecommunication line access required to have a point-of-presence on the Internet for the geographic area served. The larger ISPs have their own high-speed leased lines so that they are less dependent on the telecommunication providers and can provide better service to their customers. Among the largest national and regional ISPs are AT&T WorldNet, IBM Global Network, MCI, Netcom, UUNet, and PSINet.
ISPs also include regional providers such as New England's NEARNet and the San Francisco Bay area BARNet. They also include thousands of local providers. In addition, Internet users can also get access through online service providers (OSP) such as America Online and Compuserve.
The larger ISPs interconnect with each other through MAE (ISP switching centers run by MCI WorldCom) or similar centers. The arrangements they make to exchange traffic are known as peering agreements. There are several very comprehensive lists of ISPs world-wide available on the Web.
An ISP is also sometimes referred to as an IAP (Internet access provider). ISP is sometimes used as an abbreviation for independent service provider to distinguish a service provider that is an independent, separate company from a telephone company.
Internet Transaction Server - ITS:
An integral component of SAP's mySAP product group, the Internet Transaction Server (ITS) is the interface that enables efficient communication between an R/3 system of applications and the Internet. The ITS links an R/3 application server and a Web server, controlling the flow of data between them and enabling user access to Internet application components (IACs), which are Web-enabled business applications for the R/3 system. transactions are executed within the R/3 system. The ITS adds a presentation layer: it presents an HTML page for each transaction screen, and uses templates to incorporate changes.
The ITS is made up of WGate and AGate. When a user, who may be located anywhere with Internet access, enters or clicks on a URL to request an ITS service (an Internet application based on an IAC), their Web browser passes the request to the Web server. The Web server then passes the request to the WGate, which resides as a server extension on the same computer . The WGate establishes a connection and forwards the requests from the Web server to the AGate, which may or may not be on the same computer. The AGate processes the requests and sends relevant data to the R/3 application. The AGate retrieves data from the application, processes it into an HTML page and sends it back to the WGate. The WGate passes the page to the Web server which, in turn, sends it back to the requesting system.
Another component of the ITS is a Windows NT service called ITS Manager. ITS manager initiates and stops AGate processes and monitors them during runtime. Currently available only for the Windows NT platform, the ITS may in the future be made available for other platforms.
Internetwork Packet Exchange - IPX:
Internetwork Packet Exchange (IPX) is a networking protocol from Novell that interconnects networks that use Novell's NetWare clients and servers. IPX is a datagram or packet protocol. IPX works at the Network layer of communication protocols and is connectionless (that is, it doesn't require that a connection be maintained during an exchange of packets as, for example, a regular voice phone call does).
Packet acknowledgment is managed by another Novell protocol, the Sequenced Packet Exchange (SPX ). Other related Novell NetWare protocols are: the Routing Information Protocol (RIP), the Service Advertising Protocol (SAP), and the NetWare Link Services Protocol (NLSP).
Intrusion Detection - ID:
Intrusion detection (ID) is a type of security management system for computers and networks. An ID system gathers and analyzes information from various areas within a computer or a network to identify possible security breaches, which include both intrusions (attacks from outside the organization) and misuse (attacks from within the organization). ID uses vulnerability assessment (sometimes refered to as scanning), which is a technology developed to assess the security of a computer system or network.
Intrusion detection functions include:
* Monitoring and analyzing both user and system activities
* Analyzing system configurations and vulnerabilities
* Assessing system and file integrity
* Ability to recognize patterns typical of attacks
* Analysis of abnormal activity patterns
* Tracking user policy violations
ID systems are being developed in response to the increasing number of attacks on major sites and networks, including those of the Pentagon, the White House, NATO, and the U.S. Defense Department. The safeguarding of security is becoming increasingly difficult, because the possible technologies of attack are becoming ever more sophisticated; at the same time, less technical ability is required for the novice attacker, because proven past methods are easily accessed through the Web.
Typically, an ID system follows a two-step process. The first procedures are host-based and are considered the passive component, these include: inspection of the system's configuration files to detect inadvisable settings; inspection of the password files to detect inadvisable passwords; and inspection of other system areas to detect policy violations. The second procedures are network-based and are considered the active component: mechanisms are set in place to reenact known methods of attack and to record system responses.
In 1998, ICSA.net, a leading security assurance organization, formed the Intrusion Detection Systems Consortium (IDSC) as an open forum for ID product developers with the aim of disseminating information to the end user and developing industry standards.
I/O - Input/Output:
I/O (input/output), pronounced "eye-oh," describes any operation, program, or device that transfers data to or from a computer. Typical I/O devices are printers, hard disks, keyboards, and mouses. In fact, some devices are basically input-only devices (keyboards and mouses); others are primarily output-only devices (printers); and others provide both input and output of data (hard disks, diskettes, writable CD-ROMs).
IP - Internet Protocol:
See Internet Protocol.
IP Address - Internet Protocol Address:
This definition is based on Internet Protocol Version 4. See Internet Protocol Version 6 (IPv6 ) for a description of the newer 128-bit IP address. Note that the system of IP address classes described here, while forming the basis for IP address assignment, is generally bypassed today by use of Classless Inter-Domain Routing (CIDR) addressing.
In the most widely installed level of the Internet Protocol (IP) today, an IP address is a 32-bit number that identifies each sender or receiver of information that is sent in packets across the Internet. When you request an HTML page or send e-mail, the Internet Protocol part of TCP/IP includes your IP address in the message (actually, in each of the packets if more than one is required) and sends it to the IP address that is obtained by looking up the domain name in the Uniform Resource Locator you requested or in the e-mail address you're sending a note to. At the other end, the recipient can see the IP address of the Web page requestor or the e-mail sender and can respond by sending another message using the IP address it received.
An IP address has two parts: the identifier of a particular network on the Internet and an identifier of the particular device (which can be a server or a workstation) within that network. On the Internet itself - that is, between the router that move packets from one point to another along the route - only the network part of the address is looked at.
The Network Part of the IP Address
The Internet is really the interconnection of many individual networks (it's sometimes referred to as an internetwork). So the Internet Protocol (IP ) is basically the set of rules for one network communicating with any other (or occasionally, for broadcast messages, all other networks). Each network must know its own address on the Internet and that of any other networks with which it communicates. To be part of the Internet, an organization needs an Internet network number, which it can request from the Network Information Center (NIC). This unique network number is included in any packet sent out of the network onto the Internet.
The Local or Host Part of the IP Address
In addition to the network address or number, information is needed about which specific machine or host in a network is sending or receiving a message. So the IP address needs both the unique network number and a host number (which is unique within the network). (The host number is sometimes called a local or machine address.)
Part of the local address can identify a subnetwork or subnet address, which makes it easier for a network that is divided into several physical subnetworks (for examples, several different local area networks or ) to handle many devices.
IP Address Classes and Their Formats
Since networks vary in size, there are four different address formats or classes to consider when applying to NIC for a network number:
* Class A addresses are for large networks with many devices.
* Class B addresses are for medium-sized networks.
* Class C addresses are for small networks (fewer than 256 devices).
* Class D addresses are multicast addresses.
The first few bits of each IP address indicate which of the address class formats it is using. The address structures look like this:
Class A 0 Network (7 bits) Local address (24 bits)
Class B 10 Network (14 bits) Local address (16 bits)
Class C 110 Network (21 bits) Local address (8 bits)
Class D 1110 Multicast address (28 bits)
The IP address is usually expressed as four decimal numbers, each representing eight bits, separated by periods. This is sometimes known as the dot address and, more technically, as dotted quad notation . For Class A IP addresses, the numbers would represent "network.local.local.local"; for a Class C IP address, they would represent "network.network.network.local". The number version of the IP address can (and usually is) represented by a name or series of names called the domain name.
The Internet's explosive growth makes it likely that, without some new architecture, the number of possible network addresses using the scheme above would soon be used up (at least, for Class C network addresses). However, a new IP version, IPv6 , expands the size of the IP address to 128 bits, which will accommodate a large growth in the number of network addresses. For hosts still using IPv4, the use of subnet s in the host or local part of the IP address will help reduce new applications for network numbers. In addition, most sites on today's mostly IPv4 Internet have gotten around the Class C network address limitation by using the Classless Inter-Domain Routing (CIDR) scheme for address notation.
Relationship of the IP Address to the Physical Address
The machine or physical address used within an organization's local area networks may be different than the Internet's IP address. The most typical example is the 48-bit Ethernet address. TCP/IP includes a facility called the Address Resolution Protocol (ARP) that lets the administrator create a table that maps IP addresses to physical addresses. The table is known as the ARP cache.
Static versus Dynamic IP Addresses
The discussion above assumes that IP addresses are assigned on a static basis. In fact, many IP addresses are assigned dynamically from a pool. Many corporate networks and online services economize on the number of IP addresses they use by sharing a pool of IP addresses among a large number of users. If you're an America Online user, for example, your IP address will vary from one logon session to the next because AOL is assigning it to you from a pool that is much smaller than AOL's base of subscribers.
IP Core - Intellectual Property Core:
See Intellectual Property Core.
IPsec - Internet Protocol Security:
See Internet Protocol Security.
IPX Internetwork Packet Exchange:
See Internetwork Packet Exchange.
ISDN (Integrated Services Digital Network) is a set of CCITT/ITU standards for digital transmission over ordinary telephone copper wire as well as over other media. Home and business users who install an ISDN adapter (in place of a modem) can see highly-graphic Web pages arriving very quickly (up to 128 Kbps ). ISDN requires adapters at both ends of the transmission so your access provider also needs an ISDN adapter. ISDN is generally available from your phone company in most urban areas in the United States and Europe.
There are two levels of service: the Basic Rate Interface (BRI), intended for the home and small enterprise, and the Primary Rate Interface (PRI), for larger users. Both rates include a number of B-channels and a D-channels. Each B-channel carries data, voice, and other services. Each D-channel carries control and signaling information.
The Basic Rate Interface consists of two 64 Kbps B-channels and one 16 Kbps D- channel. Thus, a Basic Rate user can have up to 128 Kbps service. The Primary Rate consists of 23 B-channels and one 64 Kpbs D-channel in the United States or 30 B-channels and 1 D-channel in Europe.
Integrated Services Digital Network in concept is the integration of both analog or voice data together with digital data over the same network. Although the ISDN you can install is integrating these on a medium designed for analog transmission, broadband ISDN (BISDN ) will extend the integration of both services throughout the rest of the end-to-end path using fiber optic and radio media. Broadband ISDN will encompass frame relay service for high-speed data that can be sent in large bursts, the Fiber Distributed-Data Interface (FDDI), and the Synchronous Opical Network (SONET). BISDN will support transmission from 2 Mbps up to much higher, but as yet unspecified, rates.
ISP - Internet Site Provider:
See Internet Service Provider
ISPF - Interactive System Productivity Facility:
See Interactive System Productivity Facility.
ISS - Internet Information Server:
See Internet Information Server.
ITS - Internet Transaction Server:
See Internet Transaction Server.
ITU-T - Telecommunication Standardization Sector of the International Telecommunications Union:
See Telecommunication Standardization Sector of the International Telecommunications Union