Page 132 of the DSE Networks & Infrastructure knowledge center, with source-backed guidance and practical next steps.
Guidance for resilient networks, Wi-Fi, firewalls, cabling, power, exposure reduction, and connected-device planning.
A DHCP updater associates an FQDN with one client’s identity by adding a DHCID record alongside the client’s A, AAAA, or PTR records. If the FQDN exists, the updater requires a matching DHCID record before replacing address records for the same client.
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Before claiming a unique link-local record, an mDNS responder sends three probes and treats any live answer with that name as a conflict. Simultaneous probes compare proposed records, and the lexicographically later record wins the tiebreak.
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Punycode is a Bootstring encoding that represents a sequence from a large code-point set using only a smaller basic code-point set. The encoder and decoder must detect arithmetic overflow or enforce equivalent input limits; invalid input is not assumed to fit IDNA label bounds.
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DNS-SD enumeration queries a service-type name for PTR records whose targets are the available service-instance names. After choosing an instance, a client queries that instance name for SRV and TXT records; SRV supplies target host and port, while TXT supplies service metadata.
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Unless configured otherwise, a resolver serves the designated reverse zones locally and returns authoritative name errors for names below each zone. Implementations must allow local serving to be disabled and should support enabling or disabling it one zone at a time.
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After an expired DNS record cannot be refreshed authoritatively, a recursive resolver may temporarily use the record as though it were unexpired. A stale response must assign each expired record a positive TTL; the recommended response TTL is 30 seconds.
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IDNA-aware applications recognize three valid label categories: A-labels, U-labels, and non-reserved LDH labels. An A-label is the ASCII-compatible form of a complete IDNA label, begins with xn--, and must decode to a valid U-label.
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A DNS client should base retries on server round-trip estimates, cycle among servers, and increase retry timeouts exponentially. Resolvers should cap the referral and CNAME chains they follow and avoid self-referring servers so malformed data cannot create recursion loops.
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By default, DNS64 must not synthesize AAAA records when usable, non-excluded AAAA records already exist. After an empty AAAA answer, DNS64 queries for A records and synthesizes AAAA records only when one or more A records are returned.
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Wildcard synthesis is considered only after label matching finds neither an exact name nor a delegation referral. The sole synthesis source is the wildcard name immediately below the closest existing encloser; the closest encloser itself is not the source.
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