Search a name or an IPv4 address in order
06A location-aware application can begin with a domain name or an IPv4 address. These are alternative starting points, not a single mandatory pipeline.
If that name has no LOC, the address MAY use network/subnet fallback. A name with neither LOC nor any A record has no accessible location under this procedure; missing data is not a coordinate at zero.
Source for this drawing: RFC 1876 · Read RFC section 5.2.1 ↗
New to this? Start hereA quick picture + helpful background
A message needs an address.
Think of a packet as a small addressed envelope. Devices pass it onward; transport protocols decide what delivery promises an application gets.
Helpful first, if these ideas are unfamiliar
These pictures are analogies to help you learn. The linked RFC explains the actual rules.
Terms in this drawing
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
For a name, the application MUST check for a LOC record at that name; CNAME aliases should be followed as for any other record type. Without LOC, associated A records MAY be checked using network/subnet fallback.
- For a name, the application MUST check for a LOC record at that name; CNAME aliases should be followed as for any other record type. Without LOC, associated A records MAY be checked using network/subnet fallback.
- For an IPv4 address, §5.2.2 says it MUST first map the address to a name through IN-ADDR.ARPA, then check that name for LOC. Network/subnet fallback MAY be used when no LOC is present.
- Fallback is optional. If desired, the §5.2.3 algorithm is the RECOMMENDED default; it SHOULD be followed for that less-specific search, with application-specific qualifications. No IPv6 fallback algorithm is defined here.
Examples are fictional, offline teaching fixtures. RFC1876 is Experimental; its classful IPv4 fallback is historical, not universal current geolocation. Follow the linked official sections for full requirements. Additional sources: §§5.2,5.2.2,5.3.
Read the RFC section ↗