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ICMP Time Exceeded
The Internet Control Message Protocol (ICMP) is a supporting protocol in the Internet protocol suite. It is used by network devices, including routers, to send error messages and operational information indicating success or failure when communicating with another IP address. For example, an error is indicated when a requested service is not available or that a host or router could not be reached. ICMP differs from transport protocols such as TCP and UDP in that it is not typically used to exchange data between systems, nor is it regularly employed by end-user network applications (with the exception of some diagnostic tools like ping and traceroute). A separate Internet Control Message Protocol (called ICMPv6) is used with IPv6. Technical details ICMP is part of the Internet protocol suite as defined in RFC 792. ICMP messages are typically used for diagnostic or control purposes or generated in response to errors in IP operations (as specified in RFC 1122). ICMP ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DARPA
The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Advanced Research Projects Agency (ARPA), the agency was created on February 7, 1958, by President Dwight D. Eisenhower in response to the Soviet Union, Soviet launching of Sputnik 1 in 1957. By collaborating with academia, industry, and government partners, DARPA formulates and executes research and development projects to expand the frontiers of technology and science, often beyond immediate U.S. military requirements.Dwight D. Eisenhower and Science & Technology, (2008). Dwight D. Eisenhower Memorial CommissionSource The name of the organization first changed from its founding name, ARPA, to DARPA, in March 1972, changing back to ARPA in February 1993, then reverted to DARPA in March 1996. ''The Economist'' has called DARPA "the agency that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time To Live
Time to live (TTL) or hop limit is a mechanism which limits the lifespan or lifetime of data in a computer or network. TTL may be implemented as a counter (digital), counter or timestamp attached to or embedded in the data. Once the prescribed event count or timespan has elapsed, data is discarded or revalidated. In computer networking, TTL prevents a data packet from circulating indefinitely. In computing applications, TTL is commonly used to improve the performance and manage the cache (computing), caching of data. Description The original DARPA Internet Protocol's Request for Comment, RFC describes TTL as: IP packets Under the Internet Protocol, TTL is an 8-bit field. In the IPv4 header, TTL is the 9th octet (computing), octet of 20. In the IPv6 header, it is the 8th octet of 40. The maximum TTL value is 255, the maximum value of a single octet. A recommended initial value is 64. The time-to-live value can be thought of as an upper bound on the time that an IP datagram c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Covert Channels
In computer security, a covert channel is a type of attack that creates a capability to transfer information objects between processes that are not supposed to be allowed to communicate by the computer security policy. The term, originated in 1973 by Butler Lampson, is defined as channels "not intended for information transfer at all, such as the service program's effect on system load," to distinguish it from ''legitimate'' channels that are subjected to access controls by COMPUSEC. Characteristics A covert channel is so called because it is hidden from the access control mechanisms of secure operating systems since it does not use the legitimate data transfer mechanisms of the computer system (typically, read and write), and therefore cannot be detected or controlled by the security mechanisms that underlie secure operating systems. Covert channels are exceedingly hard to install in real systems, and can often be detected by monitoring system performance. In addition, they ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Denial-of-service Attacks
In computing, a denial-of-service attack (DoS attack) is a cyberattack in which the perpetrator seeks to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host connected to a network. Denial of service is typically accomplished by flooding the targeted machine or resource with superfluous requests in an attempt to overload systems and prevent some or all legitimate requests from being fulfilled. The range of attacks varies widely, spanning from inundating a server with millions of requests to slow its performance, overwhelming a server with a substantial amount of invalid data, to submitting requests with an illegitimate IP address. In a distributed denial-of-service attack (DDoS attack), the incoming traffic flooding the victim originates from many different sources. More sophisticated strategies are required to mitigate this type of attack; simply attempting to block a single source is insuffic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ping Of Death
A ping of death is a type of attack on a computer system that involves sending a malformed or otherwise malicious ping to a computer. In this attack, a host sends hundreds of ping requests with a packet size that is large or illegal to another host to try to take it offline or to keep it preoccupied responding with ICMP Echo replies. A correctly formed ping packet is typically 56 bytes in size, or 64 bytes when the Internet Control Message Protocol (ICMP) header is considered, and 84 bytes including Internet Protocol (IP) version 4 header. However, any IPv4 packet (including pings) may be as large as 65,535 bytes. Some computer systems were never designed to properly handle a ping packet larger than the maximum packet size because it violates the Internet Protocol. Like other large but well-formed packets, a ping of death is fragmented into groups of 8 octets before transmission. However, when the target computer reassembles the malformed packet, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exploit (computer Security)
An exploit is a method or piece of code that takes advantage of Vulnerability (computer security), vulnerabilities in software, Application software, applications, Computer network, networks, operating systems, or Computer hardware, hardware, typically for malicious purposes. The term "exploit" derives from the English verb "to exploit," meaning "to use something to one’s own advantage." Exploits are designed to identify flaws, bypass security measures, gain unauthorized access to systems, take control of systems, install malware, or data breach, steal sensitive data. While an exploit by itself may not be a malware, it serves as a vehicle for delivering malicious software by breaching security controls. Researchers estimate that malicious exploits cost the global economy over US$450 billion annually. In response to this threat, organizations are increasingly utilizing cyber threat intelligence to identify vulnerabilities and prevent hacks before they occur. Description Expl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internet Checksum
The Internet checksum, also called the IPv4 header checksum is a checksum used in version 4 of the Internet Protocol (IPv4) to detect corruption in the header of IPv4 packets. It is carried in the IPv4 packet header, and represents the 16-bit result of the summation of the header words. The IPv6 protocol does not use header checksums. Its designers considered that the whole-packet link layer checksumming provided in protocols, such as PPP and Ethernet, combined with the use of checksums in upper layer protocols such as TCP and UDP, are sufficient. Thus, IPv6 routers are relieved of the task of recomputing the checksum whenever the packet changes, for instance by the lowering of the hop limit counter on every hop. The Internet checksum is mandatory to detect errors in IPv6 UDP packets (including data payload). The Internet checksum is used to detect errors in ICMP packets (including data payload). Computation The checksum calculation is defined as follows: The checksu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of IP Protocol Numbers
This is a list of the IP protocol numbers found in the 8-bit ''Protocol'' field of the IPv4 header and the 8-bit ''Next Header'' field of the IPv6 header. It is an identifier for the encapsulated protocol and determines the layout of the data that immediately follows the header. Because both fields are eight bits wide, the possible values are limited to the 256 values from 0 (0x00) to 255 (0xFF), of which just over half had been allocated Protocol numbers are maintained and published by the Internet Assigned Numbers Authority (IANA). {, class="wikitable" , - ! class="nomobile" , Hex ! Protocol Number !! Keyword !! Protocol !! References/ RFC , - , style="text-align:right" class="nomobile" , 0x00 , style="text-align:right" , 0 , HOPOPT , IPv6 Hop-by-Hop Option , , - , style="text-align:right" class="nomobile" , 0x01 , style="text-align:right" , 1 , ICMP , Internet Control Message Protocol , , - , style="text-align:right" class="nomobile" , 0x02 , style="te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IPv4 Header
Internet Protocol version 4 (IPv4) is the first version of the Internet Protocol (IP) as a standalone specification. It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. IPv4 was the first version deployed for production on SATNET in 1982 and on the ARPANET in January 1983. It is still used to route most Internet traffic today, even with the ongoing deployment of Internet Protocol version 6 (IPv6), its successor. IPv4 uses a 32-bit address space which provides 4,294,967,296 (232) unique addresses, but large blocks are reserved for special networking purposes. Purpose The Internet Protocol ("IP") is the protocol that defines and enables internetworking at the internet layer of the Internet Protocol Suite. It gives the Internet a global-scale logical addressing system which allows the routing of IP data packets from a source host to the next router that is one hop closer to the intended destination h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transport Layer
In computer networking, the transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the Internet protocol suite and the OSI model. The protocols of this layer provide end-to-end communication services for applications. It provides services such as connection-oriented communication, reliability, flow control, and multiplexing. The details of implementation and semantics of the transport layer of the Internet protocol suite, which is the foundation of the Internet, and the OSI model of general networking are different. The protocols in use today in this layer for the Internet all originated in the development of TCP/IP. In the OSI model the transport layer is often referred to as Layer 4, or L4, while numbered layers are not used in TCP/IP. The best-known transport protocol of the Internet protocol suite is the Transmission Control Protocol (TCP). It is used for connection-oriented transmissions, whereas the con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internet-layer
The internet layer is a group of internetworking methods, protocols, and specifications in the Internet protocol suite that are used to transport network packets from the originating host across network boundaries; if necessary, to the destination host specified by an IP address. The internet layer derives its name from its function facilitating internetworking, which is the concept of connecting multiple networks with each other through gateways. The internet layer does not include the protocols that fulfill the purpose of maintaining link states between the local nodes and that usually use protocols that are based on the framing of packets specific to the link types. Such protocols belong to the link layer. Internet-layer protocols use IP-based packets. A common design aspect in the internet layer is the robustness principle: "Be liberal in what you accept, and conservative in what you send" as a misbehaving host can deny Internet service to many other users. Purpose Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OSI Model
The Open Systems Interconnection (OSI) model is a reference model developed by the International Organization for Standardization (ISO) that "provides a common basis for the coordination of standards development for the purpose of systems interconnection." In the OSI reference model, the components of a communication system are distinguished in seven abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application. The model describes communications from the physical implementation of transmitting bits across a transmission medium to the highest-level representation of data of a distributed application. Each layer has well-defined functions and semantics and serves a class of functionality to the layer above it and is served by the layer below it. Established, well-known communication protocols are decomposed in software development into the model's hierarchy of function calls. The Internet protocol suite as defined in and is a model of net ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
