# DNS

(is-subclass-of)
subclass: internet-service
superclass: service

internet-service
bn: Internet Service
in: service provided by set of processes using Internet protocols
in (example): e-mail
in (example): WWW
in (example): file-transfer
in (example): newsgroup
in (example): IRC (chat)


dns (internet-service)
bn: DNS, Domain Name Service
oc: http://www.internic.net/faqs/authoritative-dns.html
oc: http://www.auggy.mlnet.com/ibm/3376c45.html#namesrv
oc (reference): ftp://rtfm.mit.edu/pub/usenet/news.answers/internet/tcp-ip/domains-faq/
oc (introduction): http://www.dns.net/dnsrd/docs/whatis.html
oc (introduction): http://www.freesoft.org/CIE/Topics/75.htm
in: is a hierarchical, tree structured system -- domain name space and IP address space
in: distributed Internet directory service -- used to map between domain names and IP addresses -- mapping stored in a world-wide database -- distributed over millions of machines
in: most Internet services rely on DNS to work




(translates)
translator : dns
from : domain-name
to   : ip-address

(translates)
translator : dns
to : domain-name
from   : ip-address

(is-subclass-of)
subclass: domain-name
superclass: name

domain-name
bn: Domain Name
oc: http://computer.howstuffworks.com/dns3.htm
oc: http://searchwebservices.techtarget.com/sDefinition/0,,sid26_gci211988,00.html
in: locates an organisation or other entity on the Internet
in: domain names are for human convenience, instead of machine-readable IP-addresses
in: each domain name is made up of a series of character strings (labels) separated by dots: bond.edu.au.

(is-subclass-of)
subclass: full-qualified-domain-name
superclass: domain-name

full-qualified-domain-name
bn: FQDN, Fully Qualified Domain Name
in: to determine a unique Internet address for any host on the Internet
in (example): www.bond.edu.au. ( hostname + domain-name, incl. top-level domain)



(is-subclass-of)
superclass : domain-name
subclass   : top-level-domain

(is-subclass-of)
superclass : domain-name
subclass   : second-level-domain

top-level-domain
bn: Top Level Domain (TLDs)
oc: http://www.icann.org/tlds/
oc: http://searchwebservices.techtarget.com/sDefinition/0,,sid26_gci213511,00.html
in: identifies the most general part of the domain name in an Internet address
in: TLD is either a generic top-level domain (gTLD), such as "com", or a country code top-level domain (ccTLD), such as "fr" 
in: within every top-level domain there is a list of second-level domains
in: responsibility for operating each TLD is delegated

second-level-domain
bn: Second Level Domain 
oc: http://searchwebservices.techtarget.com/sDefinition/0,,sid26_gci213548,00.html
in: second-level domain name includes the top-level domain, e.g. cnn.com.
in: must be unique and registered with accredited companies
in: there can be duplication across domains; e.g. howstuffworks.com and howstuffworks.org are completely different domains
in: can be divided into further domain levels 


(is-registered-by)
registrar : icann
registered: top-level-domain

icann (organisation)
bn: ICANN
oc (homepage): http://www.icann.org/
in: global, non-profit corporation, responsible for managing and coordinating DNS to ensure universal resolvability -- responsible for naming, removing and introducing top-level domain names (.com, .museum, .....)
in: accredits companies to run service of allocating domain names to end customers
in: coordinates root-dns-servers
in (history): in earlier times IANA did registration and administration
oc (article): http://www.theregister.co.uk/content/6/36226.html

(coordinate)
coordinator : icann
activity    : operation-of-root-dns-server

(is-operated-by)
operation : operation-of-root-dns-server
operator  : verisign
system    : root-dns-server

root-dns-server (server)
bn: Root DNS Server
in: 13 special servers distributed around the world and coordinated by ICANN
in: only handle what is in the 'root zone' . -- top-level domains --\
   master list of top-level domain (TLD) names is kept on server A -- list is replicated to the others
oc: http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212922,00.html
oc (homepage): http://www.root-servers.org/
oc (operational-report): http://d.root-servers.org/october21.txt
oc (monitoring): http://dnsmon.ripe.net/


(is-subclass-of)
subclass   : generic-top-level-domain
superclass : top-level-domain

generic-top-level-domain
bn: gTLD, generic TLD
oc: http://www.icann.org/tlds/
in: best known ones are .org, .com, .net, .edu, .mil, .gov
in: new generic TLDs: .info, . biz, .museum, ....
in: domain names in these TLDs can only be registered through ICANN-accredited registrars 




(is-subclass-of)
subclass   : country-code-top-level-domain
superclass : top-level-domain

country-code-top-level-domain
bn: ccTLD, country-code TLD
oc: http://thewhir.com/find/domain-names/guides/cc-tld.cfm
in: TLDs with two letters (such as .de, .mx, and .jp) -- established for over 240 countries and external territories -- ISO 3166
in: can provides regional-specific branding that a typical generic TLD does not
in (comment): common misconception is that ccTLDs can only be assigned to Web sites physically located in the suffix country --\
  some countries have specific rules for who can register domains using their suffix and for what purposes




(service-is-provided-by)
provider : dns-server
service  : dns

(is-subclass-of)
subclass: dns-server
superclass: server

dns-server
bn: DNS Server
oc: http://computer.howstuffworks.com/dns.htm
oc (setup): http://www.linux.org/docs/ldp/howto/DNS-HOWTO.html
in: accepts requests from programs or from other name servers to convert domain names into IP addresses, or back
in: uses the world-wide largest and most active distributed databases
in: each database contains records (A, MX, NS, SOA, CNAME, PTR)
in: every name server has a list of all of the known root servers
in (procedure): when request arrives it can do one of four things: answer the request with an IP address by looking in its cache --\
  contact another name server (recursive) --\
  return IP address from another name server to client (iterative) --\
  return an error message because the requested domain name is invalid or does not exist


(is-subclass-of)
subclass: dns-zone
superclass: namespace

dns-zone
bn: DNS Zone
oc: http://www.menandmice.com/online_docs_and_faq/glossary/zone.htm
in: all information about a domain name and names within it

# is-reified-by dns-zone-transfer
(is-transferred)
from : primary-dns-server
to   : secondary-dns-server
what : dns-zone

# is-reified-by dns-zone-transfer
(is-transferred)
from : dns-server
to   : dns-client
what : dns-zone

(performs-function)
performer: dns-server
function : dns-zone-transfer iterative-dns-query recursive-dns-query


dns-zone-transfer (information-exchange)
bn: Zone Transfer
oc: http://www.microsoft.com/windows2000/en/server/help/default.asp?url=/windows2000/en/server/help/sag_DNS_und_ZoneTransfers.htm
in: special type of query that asks a name server for the entire contents of a zone
in: "trusted" DNSs exchange complete zones, using TTL for caching (how long it is valid)
in: zone transfers are usually used by secondary servers to update its own zone data from its primary server
in: ISPs exchange zones

(is-subclass-of)
subclass: iterative-dns-query
superclass: dns-query

iterative-dns-query
bn: Iterative DNS Query
oc: http://techrepublic.com.com/5100-6262-1058014.html
in: DNS server answers either directly to client or gives reference to other DNS server --\
   client itself has now to query the recommanded DNS server
in: references are first to servers 'higher up the DNS hierarchy' (includes root servers) -- then down the hierarchy

(is-subclass-of)
subclass: recursive-dns-query
superclass: dns-query

recursive-dns-query
bn: Recursive DNS Query
oc: http://techrepublic.com.com/5100-6262-1058014.html
in: DNS server answers directly or may contact other DNS servers for assistance (using iterative queries) --\
   then passes on the information back to the client that originated the name resolution request
in: more costly for DNS server

(exposes)
exposer: dns-server
exposed: dns-database

dns-database
bn: DNS Database
oc: http://www.tldp.org/LDP/nag/node39.html
in: large distributed database -- handling billions of requests every day through a network of millions of name servers
in: different types of entries the DNS database called records (A, MX, NS, SOA, CNAME, PTR, ...)
in: content is organized in zones

(contains)
container : dns-database
content   : a-record ns-record mx-record soa-record cname-record ptr-record



a-record (information)
bn: A-Record
oc: http://www.zytrax.com/books/dns/ch8/a.html
oc: http://www.jhsoft.com/help/rec_a.htm
in: assigns an IP address to a given domain name -- "forward lookup"
in: domain name can be mapped to more than one IP-address (load-balancing, back-up)
in (example): www.bond.edu.au -> A  131.244.5.50
in (example): www.ibm.com -> A 129.42.18.99 A 129.42.19.99 A 129.42.16.99 A 129.42.17.99


mx-record (information)
bn: MX record
oc: http://www.jhsoft.com/help/rec_MX.htm
oc: http://www.rscott.org/dns/mx.html
in: identifies the mail server (mail exchanger, MX) that is responsible for handling emails (incoming SMTP) for a given domain name
in: can get more than one entry -- preference numbers indicate the order in which mail servers should be used --\
  if best (lowest number) preference cannot be reached, then client will try next higher number
in (example): @microsoft.com ->  MX  10 maila.microsoft.com.  --  MX  100 mailb.microsoft.com. -- MX 10 mailc.microsoft.com.

ns-record (information)
bn: NS record
oc: http://www.zytrax.com/books/dns/ch8/ns.html
in: lists the DNS servers which hold the databases for a given zone - not the IP-address
in: records list the primary and secondary servers for the zone
in: only one name server is defined in the SOA record but any number of NS records may be defined
in (example): bond.edu.au -> NS  kirk.bond.edu.au. -- NS diablo.onthenet.com.au. -- NS minerva.its.bond.edu.au.

soa-record (information)
bn: SOA record
oc: http://www.jhsoft.com/help/rec_SOA.htm
in: SOA-record lists primary DNS server -- email address of the person responsible for the zone --\
  serial number used by secondary DNS servers to check if the zone has been modified --\
  details about caching used by secondary DNS servers
in (example): bond.edu.au. -> SOA minerva.its.bond.edu.au. hostmaster.bond.edu.au. 2003093001 10800 1800 3600000 86400

(refers-to)
referrer: soa-record
referral: primary-dns-server secondary-dns-server

cname-record (information)
bn: CNAME record
oc: http://www.jhsoft.com/help/rec_CNAME.htm
in: lists canonical (real) name
in: host may have more than one name -- one name for the machine itself -- other names for different services on one machine
in: canonical host name is the one with an A record associated -- others are simply aliases referring to the canonical host name
in: CNAMEs are useful when a service needs to be migrated from between hosts
in (example): www.bond.edu.au. ->  CNAME huntsman.bond.edu.au.


ptr-record (information)
bn: PTR record
oc: http://www.jhsoft.com/help/rec_PTR.htm
in: PTR-records are used to map IP addresses to domain names (reverse of forward lookup) -- "reverse look-up"
in: query is done by reversing the IP-address followed by IN-ADDR.ARPA. domain
in (example):  1.1.244.131.in-addr.arpa ->  PTR  kirk.Bond.edu.au.



(has-features)
object  : dns-server
feature : dns-caching dns-redundancy

dns-redundancy
bn: DNS redundancy
oc: http://www.dummies.com/WileyCDA/DummiesArticle/id-1699.html
in: multiple name servers exist for every zone -- so if one fails, there are others to handle the requests --\
 one of the key aspects to make DNS work globally
in: minimum of two DNS servers is needed for each domain for fault tolerance -- usually handled by the ISP or the customer


(is-achieved-through)
achievement: dns-redundancy
measure    : secondary-dns-server


dns-caching
bn: DNS Caching
oc: http://www.vicomsoft.com/glossary/dnscaching.html
in: once a name server resolves a request, it caches all of the IP addresses it receives --\
 e.g. after a request for something.com to a root server, it memorizes the IP address for that name server handling this domain --\
  dramatic speed up of overall operation -- only works if the number of changes is small compared to the number of read requests
in: every information has a due date -- Time To Live (TTL) -- controls how long a server will cache a piece of information

(is-achieved-through)
achievement: performance
measure    : dns-caching


(is-using-protocol)
user: dns-client dns-server
protocol: dns-protocol


dns-protocol (protocol)
bn: DNS Protocol
oc: http://www.freesoft.org/CIE/Course/Section2/11.htm
in: application protocol used to request resource records from name server
in: normal resource records lookups are done with UDP
in: zone transfers -- TCP must be used -- transfer entire content of a zone between (usually between primary and secondary DNS server)

dns-client
bn: DNS Client, Resolver
oc: http://www.menandmice.com/online_docs_and_faq/glossary/glossarytoc.htm?resolver.htm
in: software within an application that formats requests to be sent to the Domain Name Server for hostname to Internet address conversion
in: user program can be: e-mail, FTP client, http-client, ...
in: resolver  must know the name server it should use for converting URLs to IP addresses
in: nearest name server is either at ISP (for individuals) or in company


(is-subclass-of)
subclass: primary-dns-server
superclass: dns-server

primary-dns-server
bn: Primary DNS Server
oc: http://www.menandmice.com/online_docs_and_faq/glossary/primary.server.htm
in: also called 'master' (of a zone)
in: holds authoritative information about a zone -- there can only be one
in: this is encoded in the SOA (start of authority) record -- hostmaster, serial number, caching information




(is-subclass-of)
subclass: secondary-dns-server
superclass: dns-server

secondary-dns-server
bn: Secondary DNS Server
in: keeps copies of a zone -- updated on a regular basis using zone transfer
in: "slave" server

#-- DNSreporter -----------------------------------

(can-be-analyzed-with)
tool: dns-report
object: dns-database

dns-report (online-service)
bn: www.DNSreport.com
in: debugging and testing DNS entries
oc (homepage): http://www.dnsreport.com/


#%cancel