Zero-configuration networking: Difference between revisions

Revision as of 18:01, 6 February 2022

Revision as of 07:30, 7 February 2022

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====DNS-SD with multicast====

mDNS uses packets similar to [[Domain Name System#DNS message format|unicast DNS]] to resolve hostnames except they are sent over a multicast link. Each host listens on the mDNS port, 5353, transmitted to a well-known multicast address and resolves requests for the [[resource record|DNS record]] of its ''.local'' hostname (e.g. the [[List of DNS record types#A|A]], [[List of DNS record types#AAAA|AAAA]], [[CNAME record|CNAME]]) to its IP address. When an mDNS client needs to resolve a local hostname to an IP address, it sends a DNS request for that name to the well-known multicast address; the computer with the corresponding A/AAAA record replies with its IP address. The mDNS multicast address is <code>{{IPaddr|224.0.0.251</code>}} for IPv4 and <code>{{IPaddr|ff02::fb</code>}} for IPv6 link-local addressing.

DNS Service Discovery (DNS-SD) requests can also be sent using mDNS to yield zero-configuration DNS-SD.<ref>{{Cite IETFRef RFC| publisher = IETF | rfc = 6763 |title=DNS-Based Service Discovery}}</ref> This uses DNS [[PTR record|PTR]], SRV, [[TXT record|TXT]] records to advertise instances of service types, ___domain names for those instances, and optional configuration parameters for connecting to those instances. But SRV records can now resolve to ''.local'' ___domain names, which mDNS can resolve to local IP addresses.

====Support====