Information about Internetwork Protocol
In networking, a communications protocol or network protocol is the specification of a set of rules for a particular type of communication.
Multiple protocols often describe different aspects of a single communication. A group of protocols designed to work together are known as a protocol suite; when implemented in software they are a protocol stack. The terms are often intermingled; people may use the term "protocol" to refer to a software implementation, or use "protocol stack" to refer to the specification.
Most recent protocols are assigned by the IETF for Internet communications, and the IEEE, or the ISO organizations for other types. The ITU-T handles telecommunications protocols and formats for the PSTN. As the PSTN and Internet converge, the two sets of standards are also being driven towards convergence.
For example, one layer might describe how to encode text (with ASCII, say), while another describes how to inquire for messages (with the Internet's simple mail transfer protocol, for example), while another may detect and retry errors (with the Internet's transmission control protocol), another handles addressing (say with IP, the Internet Protocol), another handles the encapsulation of that data into a stream of bits (for example, with the point-to-point protocol), and another handles the electrical encoding of the bits, (with a V.42 modem, for example).
Layering allows the parts of a protocol to be designed and tested without a combinatorial explosion of cases, keeping each design relatively simple. Layering also permits familiar protocols to be adapted to unusual circumstances. For example, the mail protocol above can be adapted to send messages to aircraft. Just change the V.42 modem protocol to the INMARS LAPD data protocol used by the international marine radio satellites.
The reference model usually used for layering is the OSI seven layer model, which can be applied to any protocol, not just the OSI protocols. In particular, the Internet Protocol can be analysed using the OSI model.
In telephony, failure rates of 10-4 bit per bit are faulty (they interfere with telephone conversations), while 10-5 bit per bit or more should be dealt with by routine maintenance (they can be heard).
Communication systems correct errors by selectively resending bad parts of a message. For example, in TCP (the internet's Transmission Control Protocol), messages are divided into packets, each of which has a checksum. When a checksum is bad (meaning the checksum on the receiver does not match the checksum on the sender), the packet is discarded. When a packet is lost, the receiver acknowledges all of the packets up to, but not including the failed packet. Eventually, the sender sees that too much time has elapsed without an acknowledgement, so it resends all of the packets that have not been acknowledged. At the same time, the sender backs off its rate of sending, in case the packet loss was caused by saturation of the path between sender and receiver. (Note: this is an over-simplification: see TCP and congestion collapse for more detail)
In general, the performance of TCP is severely degraded in conditions of high packet loss (more than 0.1%), due to the need to resend packets repeatedly. For this reason, TCP/IP connections are typically either run on highly reliable fiber networks, or over a lower-level protocol with added error-detection and correction features (such as modem links with ARQ). These connections typically have uncorrected bit error rates of 10-9 to 10-12, ensuring high TCP/IP performance.
In packet switched networks, the equivalent functions are performed using router update messages to detect loss of connectivity.
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Multiple protocols often describe different aspects of a single communication. A group of protocols designed to work together are known as a protocol suite; when implemented in software they are a protocol stack. The terms are often intermingled; people may use the term "protocol" to refer to a software implementation, or use "protocol stack" to refer to the specification.
Most recent protocols are assigned by the IETF for Internet communications, and the IEEE, or the ISO organizations for other types. The ITU-T handles telecommunications protocols and formats for the PSTN. As the PSTN and Internet converge, the two sets of standards are also being driven towards convergence.
Network protocol design principles
Systems engineering principles have been applied to create a set of common network protocol design principles.Protocol layering
In modern protocol design, protocols are "layered". Layering is a design principle which divides the protocol design into a number of smaller parts, each of which accomplishes a particular sub-task, and interacts with the other parts of the protocol only in a small number of well-defined ways.For example, one layer might describe how to encode text (with ASCII, say), while another describes how to inquire for messages (with the Internet's simple mail transfer protocol, for example), while another may detect and retry errors (with the Internet's transmission control protocol), another handles addressing (say with IP, the Internet Protocol), another handles the encapsulation of that data into a stream of bits (for example, with the point-to-point protocol), and another handles the electrical encoding of the bits, (with a V.42 modem, for example).
Layering allows the parts of a protocol to be designed and tested without a combinatorial explosion of cases, keeping each design relatively simple. Layering also permits familiar protocols to be adapted to unusual circumstances. For example, the mail protocol above can be adapted to send messages to aircraft. Just change the V.42 modem protocol to the INMARS LAPD data protocol used by the international marine radio satellites.
The reference model usually used for layering is the OSI seven layer model, which can be applied to any protocol, not just the OSI protocols. In particular, the Internet Protocol can be analysed using the OSI model.
Error detection and correction
It is a truism that communication media are always faulty. The conventional measure of quality is the number of failed bits per bit transmitted. This has the wonderful feature of being a dimensionless figure of merit that can be compared across any speed or type of communication media.In telephony, failure rates of 10-4 bit per bit are faulty (they interfere with telephone conversations), while 10-5 bit per bit or more should be dealt with by routine maintenance (they can be heard).
Communication systems correct errors by selectively resending bad parts of a message. For example, in TCP (the internet's Transmission Control Protocol), messages are divided into packets, each of which has a checksum. When a checksum is bad (meaning the checksum on the receiver does not match the checksum on the sender), the packet is discarded. When a packet is lost, the receiver acknowledges all of the packets up to, but not including the failed packet. Eventually, the sender sees that too much time has elapsed without an acknowledgement, so it resends all of the packets that have not been acknowledged. At the same time, the sender backs off its rate of sending, in case the packet loss was caused by saturation of the path between sender and receiver. (Note: this is an over-simplification: see TCP and congestion collapse for more detail)
In general, the performance of TCP is severely degraded in conditions of high packet loss (more than 0.1%), due to the need to resend packets repeatedly. For this reason, TCP/IP connections are typically either run on highly reliable fiber networks, or over a lower-level protocol with added error-detection and correction features (such as modem links with ARQ). These connections typically have uncorrected bit error rates of 10-9 to 10-12, ensuring high TCP/IP performance.
Resiliency
Another form of network failure is topological failure, in which a communications link is cut, or degrades below usable quality. Most modern communication protocols periodically send messages to test a link. In phones, a framing bit is sent every 24 bits on T1 lines. In phone systems, when "sync is lost", fail-safe mechanisms reroute the signals around the failing equipment.In packet switched networks, the equivalent functions are performed using router update messages to detect loss of connectivity.
Protocol families
Various protocol stacks or families- AppleTalk
- DECnet
- IPX/SPX
- Open Systems Interconnection (OSI)
- Systems Network Architecture (SNA)
- Internet protocol suite
See also
- Protocol (computing)
- List of network protocols
- Network architecture
- Congestion collapse
- Tunneling protocol
Further reading
- Radia Perlman, Interconnections: Bridges, Routers, Switches, and Internetworking Protocols (2nd Edition). Addison-Wesley 1999. ISBN 0-201-63448-1. In particular Ch. 18 on "network design folklore".
- Gerard J. Holzmann, Design and Validation of Computer Protocols. Prentice Hall, 1991. ISBN 0-13-539925-4. Also available online at http://spinroot.com/spin/Doc/Book91.html
External links
as a college campus, industrial complex, or a military base. A CAN, may be considered a type of MAN (metropolitan area network), but is generally limited to an area that is smaller than a typical MAN.
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Communication is a process that allows organisms to exchange information by several methods. Communication requires that all parties understand a common language that is exchanged with each other.
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protocol is a convention or standard that controls or enables the connection, communication, and data transfer between two computing endpoints. In its simplest form, a protocol can be defined as the rules governing the syntax, semantics, and synchronization of communication.
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A protocol stack (sometimes communications stack) is a particular software implementation of a computer networking protocol suite. The terms are often used interchangeably.
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Internet is a worldwide, publicly accessible series of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP). It is a "network of networks" that consists of millions of smaller domestic, academic, business, and government
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Institute of Electrical and Electronics Engineers
Type Professional Organization
Founded January 1, 1963
Origins Merger of the American Institute of Electrical Engineers and the Institute of Radio Engineers
Key people Leah H.
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Type Professional Organization
Founded January 1, 1963
Origins Merger of the American Institute of Electrical Engineers and the Institute of Radio Engineers
Key people Leah H.
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International Organization for Standardization (Organisation internationale de normalisation), widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations.
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The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland.
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The public switched telephone network (PSTN) is the network of the world's public circuit-switched telephone networks, in much the same way that the Internet is the network of the world's public IP-based packet-switched networks.
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Systems Engineering (SE) is an interdisciplinary field of engineering, that focuses on the development and organization of complex artificial systems. Systems Engineering integrates other disciplines and specialty groups into a team effort, forming a structured development
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computing protocols, see Protocol (computing). For protocols on two-way voice communications, see Voice procedure. For other meanings of the word protocol, see Protocol.
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protocol is a convention or standard that controls or enables the connection, communication, and data transfer between two computing endpoints. In its simplest form, a protocol can be defined as the rules governing the syntax, semantics, and synchronization of communication.
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American Standard Code for Information Interchange (ASCII), generally pronounced ask-ee IPA: /ˈæski/ ( [1] ), is a character encoding based on the English alphabet.
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Simple Mail Transfer Protocol (SMTP) is the de facto standard for e-mail transmissions across the Internet. Formally SMTP is defined in RFC 821 (STD 10) as amended by RFC 1123 (STD 3) chapter 5. The protocol used today is also known as ESMTP and defined in RFC 2821.
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The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. TCP provides reliable, in-order delivery of a stream of bytes, making it suitable for applications like file transfer and e-mail.
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Internet protocol may refer to:
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- The Internet Protocol, a data-oriented protocol used for communicating data across a packet-switched internetwork
- The Internet protocol suite, a set of communications protocols that implement the protocol stack on which the Internet runs
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In networking, the Point-to-Point Protocol, or PPP, is a data link protocol commonly used to establish a direct connection between two nodes over serial cable, phone line, trunk line, cellular telephone, specialized radio links, or fiber optic links.
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Modem (from modulate and demodulate) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information.
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In mathematics a combinatorial explosion describes the effect of functions that grow very rapidly as a result of combinatorial considerations.
Examples of such functions include the factorial function and related functions.
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Examples of such functions include the factorial function and related functions.
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This article details the ITU-T V-Series Recommendations for protocols that govern approved modem communication standards and interfaces.
Note: the bis and ter suffixes are ITU-T standard designators of successive iterations of a standard.
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Note: the bis and ter suffixes are ITU-T standard designators of successive iterations of a standard.
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Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model for short) is a layered, abstract description for communications and computer network protocol design, developed as part of the Open Systems Interconnection (OSI) initiative.
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In mathematics, computer science, telecommunication, and information theory, error detection and correction has great practical importance in maintaining data (information) integrity across noisy channels and less-than-reliable storage media.
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In mathematics, computer science, telecommunication, and information theory, error detection and correction has great practical importance in maintaining data (information) integrity across noisy channels and less-than-reliable storage media.
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A truism is a claim that is so obvious or self-evident as to be hardly worth mentioning, except as a reminder or as a rhetorical or literary device.
In logic, a proposition may be a truism even if it is not a tautology, a restatement of a definition, or a theorem derived
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In logic, a proposition may be a truism even if it is not a tautology, a restatement of a definition, or a theorem derived
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In telecommunication, telephony (IPA pronunciation: [tə'lɛfəˌni]) encompasses the general use of equipment to provide voice communication over distances, specifically by connecting telephones to each other.
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The telephone is a telecommunications device which is used to transmit and receive sound (most commonly speech). Most telephones operate through transmission of electric signals over a complex telephone network which allows almost any phone user to communicate with almost anyone.
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Message in its most general meaning is an object of communication. It is something which provides information; it can also be this information itself. Therefore, its meaning is dependent upon the context in which it is used; the term may apply to both the information and its form.
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checksum is a form of redundancy check, a simple way to protect the integrity of data by detecting errors in data that are sent through space (telecommunications) or time (storage).
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The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. TCP provides reliable, in-order delivery of a stream of bytes, making it suitable for applications like file transfer and e-mail.
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