[Autogenerated] who is the dean's name?
Space One Giant database. In the beginning
of the internet, there were text files
called host files that contained the name
to address combination. Easy. When there
were only four networks attached. As the
number of hosts grew, it was just
unmanageable. And in 1983 DNS was born as
a hierarchical distributed database just a
few terms to talk about so that we're all
using the same words for the same thing.
Sometimes people use them interchangeably
when you're not supposed to, and then
don't when they are interchangeable. The
DNS name, space or database is a
distributed database. All a distributed
database means is that there are parts of
that database hosted on different servers
throughout the name Space for the name
space is for all of drones, and there's no
way a single entity could be in charge of
the whole thing. Administration time cost
of providing the bandwidth and servers
being a single point of failure. The
logistics would be mind boggling DNA or
the DNS name space is just a database. The
records it contains map the nodes name to
the info about it. At the minimum, there
will be the name of the Node.js record
Type an I P address. There will be other
kinds of record types and additional data
in the records, but name, record type and
IP address is a good start. For now, ID
item in the database is the name of the
node. That first word in the name could be
a host, but it could be many other things,
so we're going to call it a node for now.
That's the term used in RFC 10 35 which is
the beginning. RFC for DNA. CSS. All of
the labels for a node is scribe its domain
name. When you hear the term label, it
means which nodemon you're referring to
all the way towards the root of the DNA S3
structure. A fully qualified domain name
or F Q. D n lists all of the labels for a
note in the database. Be aware there might
not be a sub domain and there might not be
a node. Think of Google. Com Seriously,
When was the last time you typed W W W.
But a domain name will always be a domain,
a top level domain or T L. D and the
route, the database was broken into zones.
A zone is just part of the name space that
one entity, organization or company is in
charge of. Then what's a domain when
you're speaking of a zone? Each contains
information for one or more neighboring
domains, or sub domains, so it could be
multiple domains in a single zone. When
you're talking about a domain, it's always
a single domain, even if it has sub
domains. Each of those sub domains is a
single domain zones and domains are
similar in concept, but very different
when you start talking about database
files. The domain the domain represents
the records, but the zone has has the
records. The zone has a plain text zone
file on the zones authoritative servers,
which start with a special record called
start of Authority or SAP for short. Then
the rest of the records for that zone are
also in that text file. This is the file
of I P addresses and record types for the
zone, but goes from root zone down to the
sub domain of global Ticket that we're
talking about in this course how the
clients query for records in his own well,
a client would ask for a recursive jQuery.
It's just a request to a specific DNA
server who will give the answer or an
error message. Those queries start between
the client and their DCP configured nested
server or servers. Now, if the server
doesn't have the answer, it morphs into
the client role and then makes iterative
queries to the other servers. Those
replies will contain either an answer, a
referral or an error. That's the big
difference between the query types.
Whether or not you'll accept a referral to
another server. Those referrals makeup,
recur version. But they're not recursive
queries. That's often a sticking point for
people, and iterative query is a one to
many relationship. After the DNA server
receives the clients recursive query, the
server will answer it. If the information
is in its cache and if not, try to find
the answer on the client's behalf. It
becomes a client to the next server. Real
clients send recursive queries, servers
acting as clients send inter TIFF queries.
Gabriella wants to document the Rikers in
process when she opens her browser and
goes to global ticket dot Globomantics dot
com. What really happens if her DNS
server, sometimes called a caching server
or DNS, resolve ER has that record in its
database because it's the authoritative
server for the domain. Or it has it in its
cache from a previous client query. Well,
then, hooray! It will reply. If not, it
must send iterative queries to find it.
That's recur version. It has to look at
the name from right to left, so that
little blue dot at the end of dot com is
there on purpose. That's how you reference
the root of the database, and S one has to
work its way from the route to the host.
He'll look in his cache to see if he has a
top level domain server or T L d for dot
com, and if he does and he probably will,
he'll go to that server. But if not, he'll
start at the root. Now in Jaden, he's the
dean is admin. You'll meet him later.
Configured Ennis one as Adina Server. The
list of root servers was part of the
install, so and it's one has that in cache
all the time, and this one will send a
query to the root server for the address
of a top level domain server for dot com
____, cache the reply and ask the T. L D
server for an i P address of the
authoritative server for Globomantics dot
com. We'll talk more about the
authoritative server in a later module for
right now. Just know that they hold the
original copy of the database for their
part of DNS. Now Ennis one will cache the
reply and ask the authoritative server and
IP address for the host or sub domain. We
don't know which it is yet for global
tickets dot Globomantics dot com. ____
cache, The reply and her Ray respond to
Gabriella. Now you know why. Sometimes it
takes DNA's longer than other times. Cash
is king. See what I did there? I promise you, it's the only time I'll do it