Dns1111111111

Dns1111111111

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  Student name: hazemal maliki DNS Domain Name Systems
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  2 Domain NameSystem  DNS Overview  DNS Zones  Forward  Reverse  Fowarding  DNS Delegation/Parenting  Mail Exchangers
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  3 Overview On the Internet, the Domain Name System (DNS) associates various sorts of information with domain names  Serves as the "phone book" for the Internet  Translates human-readable computer hostnames into IP addresses  Required bynetworking equipment to delivering information  Also stores other information  Such as the list of mail exchange servers that accept email for a given domain.  By providing a worldwide keyword-based redirection service, the Domain Name System is an essential component of the modern Internet
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  4 Uses The most basic use of DNS is to translate hostnames to IP addresses.  Very much like a phone book  For example, what is the internet address of en.wikipedia.org?  The Domain Name System can be used to tell you it is 66.230.200.100
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  5 Uses DNS also has other important uses  DNS makes it possible  Assign Internet destinations to the human organization or concern they represent  Independent of the physical routing hierarchy represented by the numerical
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  6 How DNSworks
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  7 How DNSWorks - Theory  Domain names  Arranged in a tree  Cut into zones  Each served by a nameserver
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  8 How DNSWorks - Theory  The domain name space consists of a tree of domain names.  Each node or leaf in the tree has one or more resource records, which hold information associated with the domain name.  The tree sub-divides into zones.  A zone consists of a collection of connected nodes authoritatively served by an authoritative DNS nameserver.  Note that a single nameserver can host several zones
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  9 How DNSWorks - Theory  When a system administrator wants to let another administrator control a part of the domain name space within his or her zone of authority  Can delegate control to the other administrator.  Splits a part of the old zone off into a new zone  Comes under the authority of the second administrator's nameservers  The old zone becomes no longer authoritative for what goes under the authority of the new zone.
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  10 Types ofDNS records  Important categories of data stored in DNS include the following:  An A record or address record maps a hostname to a 32-bit IPv4 address.  An AAAA record or IPv6 address record maps a hostname to a 128-bit IPv6 address.  A CNAME record or canonical name record is an alias of one name to another  The A record to which the alias points can be either local or remote - on a foreign name server.  This is useful when running multiple services (like an FTP and a webserver) from a single IP address.  Each service can then have its own entry in DNS (like ftp.example.com. and www.example.com.)  An MX record or mail exchange record maps a domain name to a list of mail exchange servers for that domain.  A PTR record or pointer record maps an IPv4 address to the canonical name for that host.  Setting up a PTR record for a hostname in the in-addr.arpa. domain that corresponds to an IP address implements reverse DNS lookup for that address.  For example (at the time of writing), www.icann.net has the IP address 192.0.34.164, but a PTR record maps 164.34.0.192.in-addr.arpa to its canonical name, referrals.icann.org.  An NS record or name server record maps a domain name to a list of DNS servers authoritative for that domain.  Delegations depend on NS records.
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  11 DNS Zones Forward
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  12 DNS ReverseLookup  Overview  Typically, the Domain Name System is used to determine what IP address is associated with a given domain name.  So, to reverse-resolve a known IP address is to look up what the associated domain name is belonging to that IP address.  A reverse lookup is often referred to as reverse resolving, or more specifically reverse DNS lookup, and is accomplished using a "reverse IN-ADDR entry" in the form of a PTR record
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  13  ForwardDNS lookup  Forward DNS lookup is using an Internet domain name to find an IP address.  Reverse DNS lookup  Reverse DNS lookup is using an Internet IP address to find a domain name.
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  14 DNS Zones Forwarding
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  15 DNS Forwarding  In large, well organized, academic or ISP networks you will sometimes find that the network people have set up a forwarder hierarchy of DNS servers  Helps lighten the internal network load and the load on the outside servers  It's not easy to know if you're inside such a network or not  By using the DNS server of your network provider as a ”forwarder”' you can make the responses to queries faster and less of a load on your network  Your nameserver forwards queries to your ISP nameserver  Each time this happens you will dip into the big cache of your ISPs nameserver  Thus speeding your queries up, your nameserver does not have to do all the work itself  If you use a modem this can be quite a win http://tldp.org/HOWTO/DNS-HOWTO-4.html
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  16 Mail Exchangers Covered in previous section: How DNS Works In Practice - Other Applications