129:
query message that asks the host having that name to identify itself. That target machine then multicasts a message that includes its IP address. All machines in that subnet can then use that information to update their mDNS caches. Any host can relinquish its claim to a name by sending a response
230:
The header is identical to that found in unicast DNS, as are the sub-sections in the data part: queries, answers, authoritative-nameservers, and additional records. The number of records in each sub-section matches the value of the corresponding *COUNT field in the header.
327:
The UNICAST-RESPONSE field is used to minimize unnecessary broadcasts on the network: if the bit is set, responders SHOULD send a directed-unicast response directly to the inquiring node rather than broadcasting the response to the entire network.
147:
includes hosts that do not implement mDNS but that can be found via a conventional unicast DNS server. Resolving such conflicts requires network-configuration changes that mDNS was designed to avoid.
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of the DNS, or by a byte with the two high-order bits set (value 192) to signal an indirect pointer to another location in the message. This is known as name compression in RFC 6762.
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The CACHE-FLUSH bit is used to instruct neighbor nodes that the record should overwrite, rather than be appended onto, any existing cached entries for this RRNAME and RRTYPE.
339:
All records in the answers, authoritative-nameservers, and additional records sections have the same format and are collectively known as
Resource Records (RR).
73:
implementation was limited to discovering networked printers, subsequent releases resolved hostnames as well. mDNS can work in conjunction with
239:
The wire format for records in the query section is slightly modified from that in unicast DNS, adding the single-bit UNICAST-RESPONSE field.
683:
469:
57:(DNS). It was designed to work as either a stand-alone protocol or compatible with standard DNS servers. It uses IP multicast
455:(DNS-SD), the most common use-case for mDNS, specifies slight modifications to some of their formats (notably TXT records).
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service, using essentially the same programming interfaces, packet formats and operating semantics as unicast
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Resource
Records in mDNS also have a slightly modified general format compared to unicast DNS:
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The type of the query, i.e. the type of
Resource Record which should be returned in responses.
193:
626:
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106:
82:
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As in unicast DNS, the QNAME field consists of a series of length/value sub-fields called
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The formats of the RDATA fields are the same as those found in unicast DNS. However,
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155:
An mDNS message is a multicast UDP packet sent using the following addressing:
404:
301:
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320:(FQDN). The list is terminated by either a single null-byte representing the
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182:
42:
392:
Boolean flag indicating whether outdated cached records should be purged
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software packages, included in most Linux distributions. Although the
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571:
512:
139:
17:
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to IP addresses within small networks that do not include a local
316:. Each label represents one of the dot-separated substrings in a
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137:
By default, mDNS exclusively resolves hostnames ending with the
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660:- information site maintained by mDNS designer, Stuart Cheshire
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Integer representing the length (in octets) of the RDATA field
358:
255:
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Boolean flag indicating whether a unicast-response is desired
125:
When an mDNS client needs to resolve a hostname, it sends an
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The QCLASS field is identical to that found in unicast DNS.
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in 2000, and was eventually published as standards-track
536:
mDNS and DNS-SD slowly making their way into
Windows 10
417:
Time interval (in seconds) that the RR should be cached
227:, consisting of two parts—the header and the data.
439:Resource data; internal structure varies by RRTYPE
618:DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION
403:Class code, 1 a.k.a. "IN" for the Internet and
300:Class code, 1 a.k.a. "IN" for the Internet and
61:(UDP) packets and is implemented by the Apple
593:Manning, Bill; Woodcock, Bill (August 2000),
368:Name of the node to which the record pertains
143:top-level domain. This can cause problems if
8:
265:Name of the node to which the query pertains
664:LLMNR, Multicast DNS and names on your LAN
506:. Internet Engineering Task Force (IETF).
630:
570:
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117:and Marc Krochmal thirteen years later.
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223:The payload structure is based on the
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470:Link-Local Multicast Name Resolution
97:Multicast DNS was first proposed by
81:technique specified separately in
25:
194:standard IP multicast MAC address
615:P. Mockapetris (November 1987).
595:"Multicast Domain Name Service"
381:The type of the Resource Record
1:
79:zero-configuration networking
539:, Ctrl blog, 21 October 2015
346:mDNS Resource Record fields
39:computer networking protocol
684:Application layer protocols
318:fully qualified domain name
700:
243:mDNS Query section fields
27:Service discovery protocol
621:. Network Working Group,
225:unicast DNS packet format
101:and Bill Manning in the
77:(DNS-SD), a companion
59:User Datagram Protocol
558:DNS Service Discovery
453:DNS Service Discovery
134:(TTL) equal to zero.
75:DNS Service Discovery
476:Name Service Switch
465:Bonjour Sleep Proxy
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244:
679:Domain Name System
345:
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55:Domain Name System
51:zero-configuration
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211:33:33:00:00:00:FB
199:01:00:5E:00:00:FB
121:Protocol overview
16:(Redirected from
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632:10.17487/RFC1035
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599:Ietf Datatracker
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513:10.17487/RFC6762
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335:Resource Records
286:UNICAST-RESPONSE
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151:Packet structure
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65:and open-source
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190:Ethernet frames
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115:Stuart Cheshire
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71:Windows 10
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652:External links
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130:packet with a
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41:that resolves
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658:Multicast DNS
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503:Multicast DNS
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99:Bill Woodcock
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31:Multicast DNS
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541:, retrieved
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171:IPv6 address
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160:IPv4 address
154:
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132:time to live
127:IP multicast
124:
96:
34:
30:
29:
405:IP networks
389:CACHE-FLUSH
354:Description
302:IP networks
251:Description
188:When using
165:224.0.0.251
47:name server
673:Categories
543:2017-08-30
483:References
49:. It is a
442:Variable
371:Variable
268:Variable
43:hostnames
459:See also
425:RDLENGTH
183:UDP port
176:ff02::fb
472:(LLMNR)
400:RRCLASS
357:Length
254:Length
235:Queries
93:History
63:Bonjour
37:) is a
377:RRTYPE
365:RRNAME
314:labels
297:QCLASS
192:, the
145:.local
140:.local
109:
85:
478:(NSS)
436:RDATA
351:Field
274:QTYPE
262:QNAME
248:Field
215:(for
207:) or
203:(for
67:Avahi
640:1035
623:IETF
603:IETF
580:6763
563:IETF
521:6762
359:bits
322:root
256:bits
217:IPv6
205:IPv4
185:5353
111:6762
103:IETF
87:6763
35:mDNS
18:MDNS
637:RFC
627:doi
577:RFC
567:doi
518:RFC
508:doi
431:16
420:32
414:TTL
409:15
384:16
306:15
281:16
169:or
113:by
107:RFC
83:RFC
675::
635:.
625:.
601:,
597:,
575:.
565:.
561:.
516:.
491:^
395:1
292:1
89:.
644:.
642:.
629::
582:.
569::
523:.
510::
219:)
33:(
20:)
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