What does propagate mean?
It means that the DNS has been
communicated to each of the backbones of the Internet and that each backbone has in turn
re-mapped its routes to the domain's new DNS location. (DNS = domain name server.) This
DNS information does not travel to each of the Internet backbones in a straight line.
Each backbone has to re-map the new
DNS and pass it along the routes to be taken through it to the new DNS. This routing
information is necessary in order for anyone's computer connected to the Internet to
traverse the Internet to a particular domain's site.
Each backbone must pass the new DNS
information to all the other backbones to which it is connected, in order that the
connecting backbones can update their mapping and they, in turn, must pass along the new
DNS to the backbones connected to them. This process continues until each and every
backbone in the Internet has received the new DNS and has re-mapped the route to the
domain's new DNS.
Here's an
analogy that might help:
Imagine that the Internet, much
like a human body, is all connected together by a huge central nervous system. The system
transmits signals along its length (backbone and all related connections thereto), through
various routes along the way.
The backbone connections in turn
take the signal and push it along to sequential connecting points, similar to how a
sensation of pain or pleasure travels between the brain and the origination point of the
sensation, perhaps the full length of the body all the way to its toes, should you stub a
toe.
Within each backbone are various
domain hosts. The backbone contains the mapping to those hosts. Without the mapping done
by each backbone, no one could travel along Internet routes or view a particular site.
The actual time it takes a backbone
to update a domain's map location (DNS) depends on various factors, such as where along
the central nervous system (route) a backbone is located, as well as whether another prior
connecting backbone along the route is functioning properly and is able to timely send
along the new mapping to this backbone. (Sometimes backbones go down and there's a major
outage which affects a multitude of hosts, ISP's, and millions of sites.) The actual time
it takes to propagate is impacted by how long it is before each backbone receives the new
DNS mapping from the prior connecting backbone. Other factors which impact the process
are: which week day and time - and its relational traffic patterns, overall Internet
traffic, and the actual response time of the backbone itself to update/re-map. This isn't
an all-inclusive list of variables impacting propagation. There are other factors. But you
get the general idea.)
How long it takes for a site's new
DNS location to propagate across the Internet such that you are able to see a particular
site depends on all the above factors and more. Considering the sheer magnitude of the
Internet's overall size and the relational requirements involved, it's rather miraculous
that it works at all, let alone as rapidly as it normally does.
Understanding
the basic make-up of the Internet
Everyone connects to the Internet
via a communication device (and related software). Generally this requires a computer with
a modem, cable connection, or other form of connection (such as satellite) to the Internet
via an ISP.
Each ISP provides the
transportation of a connection from its location to another Internet location.
Internet locations are made up of
the following:
- The Internet which enables one to
traverse to various locations within it.
- Backbones (servers) within the
Internet route/transport Internet travelers through them and on to various server
locations within the Internet.
- Located within the backbones
(servers) are various hosting communities.
- Hosting communities (servers) within
each of the backbones generally connect a multitude of smaller hosting companies.
- Smaller hosting companies in turn
host domains, which in turn may host even smaller domains (subdomains).
- The servers which host domains
represent a map point on the Internet. The mapping to a domain involves both a primary and
secondary DNS (domain name server). The primary and secondary DNS consists of the main
route and a back-up route to a domain.
