|
SOA Record
A start of authority record (abbreviated as SOA record) is a type of resource record in the Domain Name System (DNS) containing administrative information about the zone, especially regarding zone transfers. The SOA record format is specified in RFC 1035. Background Normally DNS name servers are set up in clusters. The database within each cluster is synchronized through zone transfers. The SOA record for a zone contains data to control the zone transfer. This is the serial number and different timespans. It also contains the email address of the responsible person for this zone, as well as the name of the primary master name server. Usually the SOA record is located at the top of the zone. A zone without a SOA record does not conform to the standard required by RFC1035. Structure ; NAME: Name of the zone ; TYPE: SOA, abbreviation for ''start of authority'' ; CLASS: Zone class (all but universally IN for internet) ; TTL: Time-to-live ; MNAME: Primary master name server for t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resource Record
The Domain Name System (DNS) is a hierarchical and distributed naming system for computers, services, and other resources in the Internet or other Internet Protocol (IP) networks. It associates various information with domain names assigned to each of the associated entities. Most prominently, it translates readily memorized domain names to the numerical IP addresses needed for locating and identifying computer services and devices with the underlying network protocols. The Domain Name System has been an essential component of the functionality of the Internet since 1985. The Domain Name System delegates the responsibility of assigning domain names and mapping those names to Internet resources by designating authoritative name servers for each domain. Network administrators may delegate authority over sub-domains of their allocated name space to other name servers. This mechanism provides distributed and fault-tolerant service and was designed to avoid a single large central da ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Domain Name System
The Domain Name System (DNS) is a hierarchical and distributed naming system for computers, services, and other resources in the Internet or other Internet Protocol (IP) networks. It associates various information with domain names assigned to each of the associated entities. Most prominently, it translates readily memorized domain names to the numerical IP addresses needed for locating and identifying computer services and devices with the underlying network protocols. The Domain Name System has been an essential component of the functionality of the Internet since 1985. The Domain Name System delegates the responsibility of assigning domain names and mapping those names to Internet resources by designating authoritative name servers for each domain. Network administrators may delegate authority over sub-domains of their allocated name space to other name servers. This mechanism provides distributed and fault tolerance, fault-tolerant service and was designed to avoid a single ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNS Zone Transfer
DNS zone transfer, also sometimes known by the inducing DNS query type AXFR, is a type of DNS transaction. It is one of the many mechanisms available for administrators to replicate DNS databases across a set of DNS servers. A zone transfer uses the Transmission Control Protocol (TCP) for transport, and takes the form of a client–server transaction. The client requesting a zone transfer may be a secondary server requesting data from a primary server. The portion of the database that is replicated is a zone. Operation Zone transfer consists of a preamble, followed by the actual data transfer. The preamble comprises a lookup of the Start of Authority (SOA) resource record for the "zone apex", the node of the DNS namespace that is at the top of the "zone". The fields of this SOA resource record, in particular the "serial number", determine whether the actual data transfer need to occur at all. The client compares the serial number of the SOA resource record with the serial num ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Email Address
An email address identifies an email box to which messages are delivered. While early messaging systems used a variety of formats for addressing, today, email addresses follow a set of specific rules originally standardized by the Internet Engineering Task Force (IETF) in the 1980s, and updated by . The term email address in this article refers to just the ''addr-spec'' in Section 3.4 of RFC 5322. The RFC defines ''address'' more broadly as either a ''mailbox'' or ''group''. A ''mailbox'' value can be either a ''name-addr'', which contains a ''display-name'' and ''addr-spec'', or the more common ''addr-spec'' alone. An email address, such as ''john.smith@example.com'', is made up from a local-part, the symbol @, and a ''domain'', which may be a domain name or an IP address enclosed in brackets. Although the standard requires the local part to be case-sensitive, it also urges that receiving hosts deliver messages in a case-independent manner, e.g., that the mail system in the domain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic DNS
Dynamic DNS (DDNS) is a method of automatically updating a name server in the Domain Name System (DNS), often in real time, with the active DDNS configuration of its configured hostnames, addresses or other information. The term is used to describe two different concepts. The first is "dynamic DNS updating" which refers to systems that are used to update traditional DNS records without manual editing. These mechanisms use TSIG to provide security. The second kind of dynamic DNS permits lightweight and immediate updates often using an update client, which do not use the RFC2136 standard for updating DNS records. These clients provide a persistent addressing method for devices that change their location, configuration or IP address frequently. Background In the initial stages of the Internet (ARPANET), addressing of hosts on the network was achieved by static translation tables that mapped hostnames to IP addresses. The tables were maintained manually in form of the host file. ... [...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 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 caching of data. Description The original DARPA Internet Protocol's RFC document describes TTL as: IP packets Under the Internet Protocol, TTL is an 8-bit field. In the IPv4 header, TTL is the 9th 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 can exist in an Internet system. The TTL field is set by the sender ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Negative Caching
In computer programming, negative cache is a cache that also stores "negative" responses, i.e. failures. This means that a program remembers the result indicating a failure even after the cause has been corrected. Usually negative cache is a design choice, but it can also be a software bug. Examples Consider a web browser which attempts to load a page while the network is unavailable. The browser will receive an error code indicating the problem, and may display this error message to the user in place of the requested page. However, it is incorrect for the browser to place the error message in the page cache, as this would lead it to display the error again when the user tries to load the same page - even after the network is back up. The error message must not be cached under the page's URL; until the browser is able to successfully load the page, whenever the user tries to load the page, the browser must make a new attempt. A frustrating aspect of negative caches is that the u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BIND
BIND () is a suite of software for interacting with the Domain Name System (DNS). Its most prominent component, named (pronounced ''name-dee'': , short for ''name daemon''), performs both of the main DNS server roles, acting as an authoritative name server for DNS zones and as a recursive resolver in the network. As of 2015, it is the most widely used domain name server software, and is the ''de facto'' standard on Unix-like operating systems. Also contained in the suite are various administration tools such as nsupdate and dig, and a DNS resolver interface library. The software was originally designed at the University of California, Berkeley (UCB) in the early 1980s. The name originates as an acronym of ''Berkeley Internet Name Domain'', reflecting the application's use within UCB. The latest version is BIND 9, first released in 2000 and still actively maintained by the Internet Systems Consortium (ISC) with new releases issued several times a year. Key features BIND 9 is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ISO 8601
ISO 8601 is an international standard covering the worldwide exchange and communication of date and time-related data. It is maintained by the Geneva-based International Organization for Standardization (ISO) and was first published in 1988, with updates in 1991, 2000, 2004, and 2019, and an amendment in 2022. The standard provides a well-defined, unambiguous method of representing calendar dates and times in worldwide communications, especially to avoid misinterpreting numeric dates and times when such data is transferred between countries with different conventions for writing numeric dates and times. ISO 8601 applies to these representations and formats: ''dates,'' in the Gregorian calendar (including the proleptic Gregorian calendar); ''times,'' based on the 24-hour timekeeping system, with optional UTC offset; ''time intervals''; and combinations thereof.ISO 8601:2004 section 1 Scope The standard does not assign specific meaning to any element of the dates/times r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unix Time
Current Unix time () Unix time is a date and time representation widely used in computing. It measures time by the number of seconds that have elapsed since 00:00:00 UTC on 1 January 1970, the beginning of the Unix epoch, less adjustments made due to leap seconds. Unix time originated as the system time of Unix operating systems. It has come to be widely used in other computer operating systems, file systems, programming languages, and databases. Definition Two layers of encoding make up Unix time. The first layer encodes a point in time as a scalar real number which represents the number of seconds that have passed since 00:00:00UTC on Thursday, 1 January 1970. The second layer encodes that number as a sequence of bits or decimal digits. Unix time differs from both Coordinated Universal Time (UTC) and International Atomic Time (TAI) in its handling of leap seconds. UTC includes leap seconds that adjust for the discrepancy between precise time, as measured by atomic clock ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Djbdns
The djbdns software package is a DNS implementation. It was created by Daniel J. Bernstein in response to his frustrations with repeated security holes in the widely used BIND DNS software. As a challenge, Bernstein offered a $1000 prize for the first person to find a security hole in djbdns, which was awarded in March 2009 to Matthew Dempsky. , djbdns's tinydns component was the second most popular DNS server in terms of the number of domains for which it was the authoritative server, and third most popular in terms of the number of DNS hosts running it. djbdns has never been vulnerable to the widespread cache poisoning vulnerability reported in July 2008, but it has been discovered that it is vulnerable to a related attack. The source code has not been centrally managed since its release in 2001, and was released into the public domain in 2007. As of March 2009, there are a number of forks, one of which is dbndns (part of the Debian Project), and more than a dozen patches to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Year 2038 Problem
The year 2038 problem (also known as Y2038, Y2K38, or the Epochalypse) is a time formatting bug in computer systems with representing times after 03:14:07 UTC on 19 January 2038. The problem exists in systems which measure Unix time – the number of seconds elapsed since the ''Unix epoch'' (00:00:00 UTC on 1 January 1970) – and store it in a signed 32-bit integer. The data type is only capable of representing integers between −(2) and 231 − 1, meaning the latest time that can be properly encoded is 2 − 1 seconds after epoch (03:14:07 UTC on 19 January 2038). Attempting to increment to the following second (03:14:08) will cause the integer to overflow, setting its value to −(2) which systems will interpret as 2 seconds ''before'' epoch (20:45:52 UTC on 13 December 1901). The problem is similar in nature to the year 2000 problem. Computer systems that use time for critical computations may encounter fatal errors if the Y2038 pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
