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76-697: Once the DMARC DNS entry is published, any receiving email server can authenticate the incoming email based on the instructions published by the domain owner within the DNS entry. If the email passes the authentication, it will be delivered and can be trusted. If the email fails the check, depending on the instructions held within the DMARC record the email could be delivered, quarantined or rejected. DMARC extends two existing email authentication mechanisms, Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM). It allows

152-446: A label and zero or more resource records (RR), which hold information associated with the domain name. The domain name itself consists of the label, concatenated with the name of its parent node on the right, separated by a dot. The tree sub-divides into zones beginning at the root zone . A DNS zone may consist of as many domains and subdomains as the zone manager chooses. DNS can also be partitioned according to class where

228-480: A "com" server, and finally an "example.com" server. Name servers in delegations are identified by name, rather than by IP address. This means that a resolving name server must issue another DNS request to find out the IP address of the server to which it has been referred. If the name given in the delegation is a subdomain of the domain for which the delegation is being provided, there is a circular dependency . In this case,

304-450: A "message/rfc822" or a "text/rfc822-headers". Forensic Reports also contain the following: There are several different types of email forwarding , some of which may break SPF. This is one of the reasons why email forwarding can affect DMARC authentication results. Mailing lists are a frequent cause of legitimate breakage of the original author's domain DKIM signature, for example by adding

380-408: A cache of data. An authoritative name server can either be a primary server or a secondary server. Historically the terms master/slave and primary/secondary were sometimes used interchangeably but the current practice is to use the latter form. A primary server is a server that stores the original copies of all zone records. A secondary server uses a special automatic updating mechanism in

456-416: A combination of these methods. In a non-recursive query , a DNS resolver queries a DNS server that provides a record either for which the server is authoritative, or it provides a partial result without querying other servers. In case of a caching DNS resolver , the non-recursive query of its local DNS cache delivers a result and reduces the load on upstream DNS servers by caching DNS resource records for

532-426: A comma. Target email addresses can belong to external domains. In that case, the target domain has to set up a DMARC record to say it agrees to receive them, otherwise it would be possible to exploit reporting for spam amplification . For example, say receiver.example receives a mail message From: someone@sender.example and wishes to report it. If it finds ruf=mailto:some-id@thirdparty.example , it looks for

608-728: A compromise between five competing proposals of solutions to Paul Mockapetris . Mockapetris instead created the Domain Name System in 1983 while at the University of Southern California . The Internet Engineering Task Force published the original specifications in RFC 882 and RFC 883 in November 1983. These were updated in RFC 973 in January 1986. In 1984, four UC Berkeley students, Douglas Terry, Mark Painter, David Riggle, and Songnian Zhou, wrote

684-426: A confirming DNS record in the namespace administered by the target, like this: Aggregate Reports are sent as XML files, typically once per day. The subject mentions the "Report Domain", which indicates the DNS domain name about which the report was generated, and the "Submitter", which is the entity issuing the report. The payload is in an attachment with a long filename consisting of bang-separated elements such as

760-399: A dataset from a reliable source. Assuming the resolver has no cached records to accelerate the process, the resolution process starts with a query to one of the root servers. In typical operation, the root servers do not answer directly, but respond with a referral to more authoritative servers, e.g., a query for "www.wikipedia.org" is referred to the org servers. The resolver now queries

836-402: A forwarder and a mailing list, respectively. DMARC authentication failed for the last row only; it could have affected the message disposition if example.org had specified a strict policy. The disposition reflects the policy published actually applied to the messages, none , quarantine , or reject . Along with it, not shown in the table, DMARC provides for a policy override. Some reasons why

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912-534: A general purpose database, the DNS has also been used in combating unsolicited email (spam) by storing a real-time blackhole list (RBL). The DNS database is traditionally stored in a structured text file, the zone file , but other database systems are common. The Domain Name System originally used the User Datagram Protocol (UDP) as transport over IP. Reliability, security, and privacy concerns spawned

988-419: A list of public DNS suffixes. The upcoming spec instead specifies a Tree Walk through the parent domains. So, for example, "a.b.c.d.example.com.au" and "example.com.au" have the same Organizational Domain, because _dmarc.example.com.au is the only defined DMARC record among all the subdomains involved, including _dmarc.au. As this allows domain owners to define domain roles, it is deemed to be more accurate than

1064-499: A mailing list, and then the list operator is forced to reject it or do From: rewriting. One of the most popular and least intrusive workarounds consists of rewriting the From: header field. The original author's address can then be added to the Reply-To: field. Rewriting can range from just appending .INVALID to the domain name, to allocating a temporary user ID where a modified version of

1140-548: A number of records. Records can be put in a database as a relation and viewed in a tabular form. The XML schema is defined in Appendix C of specifications and a raw record is exemplified in dmarc.org. Here we stick with a relational example, which better conveys the nature of the data. DMARC records can also be directly transformed in HTML by applying an XSL stylesheet . Rows are grouped by source IP and authentication results, passing just

1216-425: A percentage of the messages that fail DMARC check. Receivers are asked to select the given percentage of messages by a simple Bernoulli sampling algorithm. The rest of the messages should undergo the lower policy; that is, none if p=quarantine , quarantine if p=reject . If not specified, pct defaults to 100% of messages. The case p=quarantine; pct=0; is being used to force mailing list managers to rewrite

1292-407: A period of time after an initial response from upstream DNS servers. In a recursive query , a DNS resolver queries a single DNS server, which may in turn query other DNS servers on behalf of the requester. For example, a simple stub resolver running on a home router typically makes a recursive query to the DNS server run by the user's ISP . A recursive query is one for which the DNS server answers

1368-498: A prefix to the subject header. A number of workarounds are possible, and mailing list software packages are working on solutions. This workaround keeps the standard mailing list workflow, and is adopted by several large mailing list operators, but precludes the list adding footers and subject prefixes. This requires careful configuration of mailing software to make sure signed headers are not reordered or modified. A misconfigured email server may put List-id in its DKIM of messages sent to

1444-443: A receiver can apply a policy different from the one requested are already provided for by the specification: Forensic Reports, also known as Failure Reports, are generated in real time and consist of redacted copies of individual messages that failed SPF, DKIM or both based upon what value is specified in the fo tag. Their format, an extension of Abuse Reporting Format , resembles that of regular bounces in that they contain either

1520-501: A sender's domain to indicate that their email messages are protected by SPF and/or DKIM, and tells a receiver what to do if neither of those authentication methods passes – such as to reject the message or quarantine it. The policy can also specify how an email receiver can report back to the sender's domain about messages that pass and/or fail. These policies are published in the public Domain Name System (DNS) as text TXT records . DMARC does not directly address whether or not an email

1596-469: A service's location on the network to change without affecting the end users, who continue to use the same hostname. Users take advantage of this when they use meaningful Uniform Resource Locators ( URLs ) and e-mail addresses without having to know how the computer actually locates the services. An important and ubiquitous function of the DNS is its central role in distributed Internet services such as cloud services and content delivery networks . When

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1672-499: A significant amount of disruption, and those mailbox providers have been accused of forcing the costs of their own security failures onto third parties. As of 2020, the FAQ in the official DMARC wiki contains several suggestions for mailing lists to handle messages from a domain with a strict DMARC policy, of which the most widely implemented is the mailing list changing the “From” header to an address in its own domain. An IETF working group

1748-477: A type of error called a "lame delegation" or "lame response". Domain name resolvers determine the domain name servers responsible for the domain name in question by a sequence of queries starting with the right-most (top-level) domain label. For proper operation of its domain name resolver, a network host is configured with an initial cache ( hints ) of the known addresses of the root name servers. The hints are updated periodically by an administrator by retrieving

1824-455: A user accesses a distributed Internet service using a URL, the domain name of the URL is translated to the IP address of a server that is proximal to the user. The key functionality of the DNS exploited here is that different users can simultaneously receive different translations for the same domain name, a key point of divergence from a traditional phone-book view of the DNS. This process of using

1900-441: Is "aligned" with other authenticated domain names. If either SPF (specified using the aspf field) or DKIM (specified using the adkim ) alignment checks pass, then the DMARC alignment test passes. Alignment may be specified as strict or relaxed. For strict alignment, the domain names must be identical. For relaxed alignment, the top-level "Organizational Domain" must match. The Organizational Domain used to be found by checking

1976-463: Is covered by the preceding change in the From: header field. That way, the original meaning of those fields is reversed. Altering the author is not fair in general, and can break the expected relationship between meaning and appearance of that datum. It also breaks automated use of it. There are communities which use mailing lists to coordinate their work, and deploy tools which use the From: field to attribute authorship to attachments. Wrapping

2052-489: Is known as the LDH rule (letters, digits, hyphen). Domain names are interpreted in a case-independent manner. Labels may not start or end with a hyphen. An additional rule requires that top-level domain names should not be all-numeric. The limited set of ASCII characters permitted in the DNS prevented the representation of names and words of many languages in their native alphabets or scripts. To make this possible, ICANN approved

2128-484: Is only achieved with at least 6 labels (counting the last null label). Although no technical limitation exists to prevent domain name labels from using any character that is representable by an octet, hostnames use a preferred format and character set. The characters allowed in labels are a subset of the ASCII character set, consisting of characters a through z , A through Z , digits 0 through 9 , and hyphen. This rule

2204-399: Is served by the root name servers , the servers to query when looking up ( resolving ) a TLD . An authoritative name server is a name server that only gives answers to DNS queries from data that have been configured by an original source, for example, the domain administrator or by dynamic DNS methods, in contrast to answers obtained via a query to another name server that only maintains

2280-430: Is spam or otherwise fraudulent. Instead, DMARC can require that a message not only pass DKIM or SPF validation, but that it also pass § Alignment . Under DMARC a message can fail even if it passes SPF or DKIM but fails alignment. Setting up DMARC may improve the deliverability of messages from legitimate senders. DMARC operates by checking that the domain in the message's From: field (also called "RFC5322.From")

2356-669: The Federal Trade Commission published a study on DMARC usage by businesses. Out of 569 businesses, the study found about a third implemented any DMARC configuration, fewer than 10% used DMARC to instruct servers to reject unauthenticated messages, and a majority had implemented SPF. The contributors of the DMARC specification include: Popular services that perform DMARC analysis and/or record validation include Valimail, Dmarcian and EasyDmarc. Domain Name Service Early research and development: Merging

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2432-532: The Internationalizing Domain Names in Applications (IDNA) system, by which user applications, such as web browsers, map Unicode strings into the valid DNS character set using Punycode . In 2009, ICANN approved the installation of internationalized domain name country code top-level domains ( ccTLD s) . In addition, many registries of the existing top-level domain names ( TLD s ) have adopted

2508-618: The Public Suffix List . Like SPF and DKIM, DMARC uses the concept of a domain owner, the entity or entities that are authorized to make changes to a given DNS domain. SPF checks that the IP address of the sending server is authorized by the owner of the domain that appears in the SMTP MAIL FROM command. (The email address in MAIL FROM is also called the bounce address , envelope-from or RFC5321.MailFrom.) In addition to requiring that

2584-478: The top-level domain ; for example, the domain name www.example.com belongs to the top-level domain com . The hierarchy of domains descends from right to left; each label to the left specifies a subdivision, or subdomain of the domain to the right. For example, the label example specifies a subdomain of the com domain, and www is a subdomain of example.com. This tree of subdivisions may have up to 127 levels. A label may contain zero to 63 characters, because

2660-404: The " Authoritative Answer " ( AA ) bit in its responses. This flag is usually reproduced prominently in the output of DNS administration query tools, such as dig , to indicate that the responding name server is an authority for the domain name in question. When a name server is designated as the authoritative server for a domain name for which it does not have authoritative data, it presents

2736-526: The ARPANET. Elizabeth Feinler developed and maintained the first ARPANET directory. Maintenance of numerical addresses, called the Assigned Numbers List, was handled by Jon Postel at the University of Southern California 's Information Sciences Institute (ISI), whose team worked closely with SRI. Addresses were assigned manually. Computers, including their hostnames and addresses, were added to

2812-462: The DNS database are for start of authority ( SOA ), IP addresses ( A and AAAA ), SMTP mail exchangers (MX), name servers (NS), pointers for reverse DNS lookups (PTR), and domain name aliases (CNAME). Although not intended to be a general purpose database, DNS has been expanded over time to store records for other types of data for either automatic lookups, such as DNSSEC records, or for human queries such as responsible person (RP) records. As

2888-401: The DNS protocol in communication with its primary to maintain an identical copy of the primary records. Every DNS zone must be assigned a set of authoritative name servers. This set of servers is stored in the parent domain zone with name server (NS) records. An authoritative server indicates its status of supplying definitive answers, deemed authoritative , by setting a protocol flag, called

2964-468: The DNS to assign proximal servers to users is key to providing faster and more reliable responses on the Internet and is widely used by most major Internet services. The DNS reflects the structure of administrative responsibility on the Internet. Each subdomain is a zone of administrative autonomy delegated to a manager. For zones operated by a registry , administrative information is often complemented by

3040-527: The From field hasn't been modified since the signature was applied. There may be several DKIM signatures on an email message; DMARC requires one valid signature where the domain in the d= tag aligns with the sender's domain stated in the From: header field. DMARC records are published in DNS with a subdomain label _dmarc , for example _dmarc.example.com . Compare this to SPF at example.com , and DKIM at selector._domainkey.example.com . The content of

3116-680: The From: field, as some don't do so when p=none . Finally, the subdomain policy, sp= and the newly added no-domain policy, np= allow tweaking the policy for specific subdomains. DMARC is capable of producing two separate types of reports. Aggregate reports are sent to the address specified following the rua . Forensic reports are emailed to the address following the ruf tag. These mail addresses must be specified in URI mailto format (e.g. mailto:worker@example.net ). Multiple reporting addresses are valid and must each be in full URI format, separated by

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3192-456: The IDNA system, guided by RFC 5890, RFC 5891, RFC 5892, RFC 5893. The Domain Name System is maintained by a distributed database system, which uses the client–server model . The nodes of this database are the name servers . Each domain has at least one authoritative DNS server that publishes information about that domain and the name servers of any domains subordinate to it. The top of the hierarchy

3268-430: The IP address spaces . The Domain Name System maintains the domain name hierarchy and provides translation services between it and the address spaces. Internet name servers and a communication protocol implement the Domain Name System. A DNS name server is a server that stores the DNS records for a domain; a DNS name server responds with answers to queries against its database. The most common types of records stored in

3344-402: The Internet, and increase performance in end-user applications, the Domain Name System supports DNS cache servers which store DNS query results for a period of time determined in the configuration ( time-to-live ) of the domain name record in question. Typically, such caching DNS servers also implement the recursive algorithm necessary to resolve a given name starting with the DNS root through to

3420-521: The SPF check passes, DMARC checks that RFC5321.MailFrom aligns with 5322.From. DKIM allows parts of an email message to be cryptographically signed, and the signature must cover the From field. Within the DKIM-Signature mail header, the d= (domain) and s= (selector) tags specify where in DNS to retrieve the public key for the signature. A valid signature proves that the signer is a domain owner, and that

3496-487: The TXT resource record consists of name=value tags, separated by semicolons, similar to SPF and DKIM. The available tags are: For example: In this example, the entity controlling the example.com DNS domain intends to monitor SPF and/or DKIM failure rates and doesn't expect email to be sent from subdomains of example.com. Note that a subdomain can publish its own DMARC record; receivers must check it out before falling back to

3572-499: The administrative owner of a domain to publish a policy in their DNS records to specify how to check the From: field presented to end users; how the receiver should deal with failures – and provides a reporting mechanism for actions performed under those policies. DMARC is defined in the Internet Engineering Task Force 's published document RFC 7489 , dated March 2015, as "Informational". A DMARC policy allows

3648-704: 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 subdomains of their allocated name space to other name servers. This mechanism provides distributed and fault-tolerant service and

3724-460: The author(s) of the message, that is, the mailbox(es) of the person(s) or system(s) responsible for the writing of the message." Mailbox refers to the author's email address. The Sender: header is available to indicate that an email was sent on behalf of another party, but DMARC only checks policy for the From domain and ignores the Sender domain. Both ADSP and DMARC reject using the Sender field on

3800-543: The authoritative name servers of the queried domain. With this function implemented in the name server, user applications gain efficiency in design and operation. The combination of DNS caching and recursive functions in a name server is not mandatory; the functions can be implemented independently in servers for special purposes. Internet service providers typically provide recursive and caching name servers for their customers. In addition, many home networking routers implement DNS caches and recursion to improve efficiency in

3876-466: The computer. Computers at educational institutions would have the domain edu , for example. She and her team managed the Host Naming Registry from 1972 to 1989. By the early 1980s, maintaining a single, centralized host table had become slow and unwieldy and the emerging network required an automated naming system to address technical and personnel issues. Postel directed the task of forging

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3952-432: The count of each group. The leftmost result columns, labelled SPF and DKIM show DMARC-wise results, either pass or fail, taking alignment into account. The rightmost ones, with similar labels, show the name of the domain which claims to participate in the sending of the message and (in parentheses) the authentication status of that claim according to the original protocol, SPF or DKIM, regardless of Identifier Alignment. On

4028-438: The delegation for example.org. The glue records are address records that provide IP addresses for ns1.example.org. The resolver uses one or more of these IP addresses to query one of the domain's authoritative servers, which allows it to complete the DNS query. A common approach to reduce the burden on DNS servers is to cache the results of name resolution locally or on intermediary resolver hosts. Each DNS query result comes with

4104-738: The first Unix name server implementation for the Berkeley Internet Name Domain, commonly referred to as BIND . In 1985, Kevin Dunlap of DEC substantially revised the DNS implementation. Mike Karels , Phil Almquist, and Paul Vixie then took over BIND maintenance. Internet Systems Consortium was founded in 1994 by Rick Adams , Paul Vixie , and Carl Malamud , expressly to provide a home for BIND development and maintenance. BIND versions from 4.9.3 onward were developed and maintained by ISC, with support provided by ISC's sponsors. As co-architects/programmers, Bob Halley and Paul Vixie released

4180-453: The first production-ready version of BIND version 8 in May 1997. Since 2000, over 43 different core developers have worked on BIND. In November 1987, RFC 1034 and RFC 1035 superseded the 1983 DNS specifications. Several additional Request for Comments have proposed extensions to the core DNS protocols. The domain name space consists of a tree data structure . Each node or leaf in the tree has

4256-433: The length is only allowed to take 6 bits. The null label of length zero is reserved for the root zone. The full domain name may not exceed the length of 253 characters in its textual representation (or 254 with the trailing dot). In the internal binary representation of the DNS this maximum length of 253 requires 255 octets of storage, as it also stores the length of the first of many labels and adds last null byte. 255 length

4332-422: The local network. The client side of the DNS is called a DNS resolver. A resolver is responsible for initiating and sequencing the queries that ultimately lead to a full resolution (translation) of the resource sought, e.g., translation of a domain name into an IP address. DNS resolvers are classified by a variety of query methods, such as recursive , non-recursive , and iterative . A resolution process may use

4408-481: The message works nicely, for those who use an email client which understands wrapped messages. Not doing any change is perhaps the most obvious solution, except that they seem to be legally required in some countries, and that routinely losing SPF authentication may render overall authentication more fragile. Making changes to the From: header field to pass DKIM alignment may bring the message out of compliance with RFC 5322 section 3.6.2: "The 'From:' field specifies

4484-408: The name server and IP address. For example, if the authoritative name server for example.org is ns1.example.org, a computer trying to resolve www.example.org first resolves ns1.example.org. As ns1 is contained in example.org, this requires resolving example.org first, which presents a circular dependency. To break the dependency, the name server for the top level domain org includes glue along with

4560-409: The name server providing the delegation must also provide one or more IP addresses for the authoritative name server mentioned in the delegation. This information is called glue . The delegating name server provides this glue in the form of records in the additional section of the DNS response, and provides the delegation in the authority section of the response. A glue record is a combination of

4636-559: The networks and creating the Internet: Commercialization, privatization, broader access leads to the modern Internet: Examples of Internet services: The Domain Name System ( DNS ) is a hierarchical and distributed name service that provides a naming system for computers , services, and other resources on the Internet or other Internet Protocol (IP) networks. It associates various information with domain names ( identification strings ) assigned to each of

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4712-698: The non-technical basis that many user agents do not display this to the recipient. A draft DMARC specification has been maintained since 30 January 2012. In October 2013, GNU Mailman 2.1.16 was released with options to handle posters from a domain with the DMARC policy of p=reject . The change tried to anticipate the interoperability issues expected in case restrictive policies were applied to domains with human users (as opposed to purely transactional mail domains). In April 2014, Yahoo changed its DMARC policy to p=reject , thereby causing misbehavior in several mailing lists. A few days later, AOL also changed its DMARC policy to p=reject . Those moves resulted in

4788-534: The organizational domain record. The protocol provides for various ratchets, or transitional states, to allow mail admins to gradually transition from not implementing DMARC at all the way through to an unyielding setup. The concept of stepwise adoption assumes that the goal of DMARC is the strongest setting, which is not the case for all domains. Regardless of intent, these mechanisms allow for greater flexibility. First and foremost, there are three policies: The policy published can be mitigated by applying it to only

4864-532: The primary file by contacting the SRI Network Information Center (NIC), directed by Feinler, via telephone during business hours. Later, Feinler set up a WHOIS directory on a server in the NIC for retrieval of information about resources, contacts, and entities. She and her team developed the concept of domains. Feinler suggested that domains should be based on the location of the physical address of

4940-402: The query completely by querying other name servers as needed. In typical operation, a client issues a recursive query to a caching recursive DNS server, which subsequently issues non-recursive queries to determine the answer and send a single answer back to the client. The resolver, or another DNS server acting recursively on behalf of the resolver, negotiates use of recursive service using bits in

5016-404: The query headers. DNS servers are not required to support recursive queries. The iterative query procedure is a process in which a DNS resolver queries a chain of one or more DNS servers. Each server refers the client to the next server in the chain, until the current server can fully resolve the request. For example, a possible resolution of www.example.com would query a global root server, then

5092-472: The registry's RDAP and WHOIS services. That data can be used to gain insight on, and track responsibility for, a given host on the Internet. Using a simpler, more memorable name in place of a host's numerical address dates back to the ARPANET era. The Stanford Research Institute (now SRI International ) maintained a text file named HOSTS.TXT that mapped host names to the numerical addresses of computers on

5168-413: The report-issuing receiver, the begin and end epochs of the reported period as Unix-style time stamps, an optional unique identifier and an extension which depends on the possible compression (used to be .zip ). For example: example.com!example.org!1475712000!1475798400.xml.gz . The XML content consists of a header, containing the policy on which the report is based and report metadata, followed by

5244-508: The right side, SPF can appear at most twice, once for the Return-Path: test and once for the HELO test; DKIM can appear once for each signature present in the message. In the example, the first row represents the main mail flow from example.org, and the second row is a DKIM glitch, such as signature breakage due to a minor alteration in transit. The third and fourth rows show typical failures modes of

5320-516: The root servers, and as a result, root name servers actually are involved in only a relatively small fraction of all requests. In theory, authoritative name servers are sufficient for the operation of the Internet. However, with only authoritative name servers operating, every DNS query must start with recursive queries at the root zone of the Domain Name System and each user system would have to implement resolver software capable of recursive operation. To improve efficiency, reduce DNS traffic across

5396-629: The separate classes can be thought of as an array of parallel namespace trees. Administrative responsibility for any zone may be divided by creating additional zones. Authority over the new zone is said to be delegated to a designated name server. The parent zone ceases to be authoritative for the new zone. The definitive descriptions of the rules for forming domain names appear in RFC 1035, RFC 1123, RFC 2181, and RFC 5892. A domain name consists of one or more parts, technically called labels , that are conventionally concatenated , and delimited by dots, such as example.com. The right-most label conveys

5472-423: The servers referred to, and iteratively repeats this process until it receives an authoritative answer. The diagram illustrates this process for the host that is named by the fully qualified domain name "www.wikipedia.org". This mechanism would place a large traffic burden on the root servers, if every resolution on the Internet required starting at the root. In practice caching is used in DNS servers to off-load

5548-592: The use of the Transmission Control Protocol (TCP) as well as numerous other protocol developments. An often-used analogy to explain the DNS is that it serves as the phone book for the Internet by translating human-friendly computer hostnames into IP addresses. For example, the hostname www.example.com within the domain name example.com translates to the addresses 93.184.216.34 ( IPv4 ) and 2606:2800:220:1:248:1893:25c8:1946 ( IPv6 ). The DNS can be quickly and transparently updated, allowing

5624-443: The user's address is used, or an opaque ID is used, which keeps the user's "real" email address private from the list. In addition, the display name can be changed so as to show both the author and the list (or list operator). Those examples would result, respectively, in one of the following: The last line, Reply-To: , has to be designed in order to accommodate reply-to-author functionality, in which case reply-to-list functionality

5700-462: Was designed to avoid a single large central database. In addition, the DNS specifies the technical functionality of the database service that is at its core. It defines the DNS protocol, a detailed specification of the data structures and data communication exchanges used in the DNS, as part of the Internet protocol suite . The Internet maintains two principal namespaces , the domain name hierarchy and

5776-601: Was formed in August 2014 in order to address DMARC issues, starting from interoperability concerns and possibly continuing with a revised standard specification and documentation. Meanwhile, the existing DMARC specification had reached an editorial state agreed upon and implemented by many. It was published in March 2015 on the Independent Submission stream in the "Informational" (non-standard) category as RFC 7489 . In March 2017,

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