chapter3 Flashcards
dns stands for
domain name system
why do we need dns
When we type in http://www.msn.com/home.aspx, the browser needs to look up the IP address of the web servers name (host name) www.msn.com
If we do a ping to www.google.com we first need to convert the hostname to an ip address
alternative to dns + explanation
WINS
store netbios computer names (max 5 char) in a non hierarchical database
how can we do name resolution + requirements for this
DNS servers in your own network, or via the internet
WINS servers (for windows 2000)
Broadcast (as last option and least efficient way)
Requirements -> web servers or servers in your own network must be registrered with the DNS server (auto or manually)
give an overview of DNS
DNS is a hierarchical distributed system
Dns is the foundation of the internet naming scheme
Dns supports accessing resources by using alphanumeric names
interNIC is responsible for managing the domain namespace
dns was created to support the internet’s growing number of hosts
rules of dns naming and fqdn names
a through z
A through Z
0 through 9
Hyphen (-)
Underscore (_) is a reserved character
what is a FQDN or fully qualified domain name
behind these names is one or more IP address in the DNS database
components in a dns query + explanation
Dns client = dns client is a device that has a host name query, this can be a server or a client Pc or any device
Dns server = dns server is a device that has a dns service (linux, unix, windows based) and this device maintains a database of hostnames, this database is called a zone file
Dns servers on the internet
what is a dns query
Queries are recursive or iterative
Dns clients and dns servers both initiate queries
Dns servers are authoritative or non authoritative for a namespace
Authoritative dns server for the namespace will either:
Return the requested IP address
Return an authoritative “No”
Nonauthoritative dns server for the namespace will either:
Check its chache
Use forwarders
Use root hints
A query is a request for name resolution and is directed to a dns server
what is a recursive query
A recursive query is sent to dns server and requires a complete answer
what is a iterative query
A iterative query is sent to a dns server and may be answered with a referral to another dns server
what is a forwarder and explain
A forwarder is a dns server designated to resolve external or offsite dns domain names, advantage is that the answer is stored in the forwarder’s chache. Every other dns server that uses the forwarder will be able to use this cache to get an answer faster
what is conditional forwarding
Conditional forwarding forwards requests using a domain name condition
what are root hints
Root hints contain the IP addresses for dns root servers
explain cache
Everything that is chached in the cache will remain for a certain ttl or time to live, after that it automatically disappears from the cache. When restarting the dns client or server device this cache will also be cleared