Διαχείριση Δικτύων Ευφυή Δίκτυα

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Εργαστήριο Διαχείρισης και Βέλτιστου Σχεδιασμού Δικτύων ( NETMODE). Διαχείριση Δικτύων Ευφυή Δίκτυα. Άσκηση 3 DOMAIN NAME SYSTEM (DNS). ΓΙΑΤΙ ΧΡΕΙΑΖΟΜΑΣΤΕ ΥΠΗΡΕΣΙΑ ΟΝΟΜΑΤΟΔΟΣΙΑΣ ;. 2 < # κόμβων < 1 000 000 000 000 2 < # χρηστών < 1 000 000 000 000 - PowerPoint PPT Presentation

Transcript of Διαχείριση Δικτύων Ευφυή Δίκτυα

  • 3DOMAIN NAME SYSTEM (DNS) (NETMODE)

  • ;

    2 < # < 1 000 000 000 0002 < # < 1 000 000 000 000 : IPv4 address (32 bit) IPv6 (128 bit)

    Domain Name System IP & (nameservers)

    ; (caching)

    ;

  • (FQDN)Fully Qualified Domain Name (FQDN)WWW.NTUA.GR. labels dots

    DNS -> FQDNs (resources)

    (key)

    dot

  • (Domain names) .

    dots

    .

    grcomntuawwwwwwedumitecedblabnetmodeftpibmgoogleapplecnn

  • :

    . :

    ( , .. , ) A (.. )

  • DomainsDomains -> namespaces .com com domain. ntua.gr ntua.gr domain gr domain.ntua.gr domaingrcomntuawwwwwwedumitcnnecenetmodedblabftpibmapplegoogle

  • * DOMAIN NAMES (Registrars) & IP - ASN ADDRESS SPACES (Host Masters) : ICAN (Internet Corporation for Assigned Names & Numbers) http://www.icann.org/ TLD (Top Level Domain) DatabaseGeneric Domain Names (.edu, .com, .net, .org, .gov, .mil, ) (Domain Name Registrars): VeriSign ( .com, .net, ), Educause (.edu), PIR (.org)

    Country Code (cc) Domain Names (.gr, .fr, .uk, .de, .jp, ) (Domain Name Registrars )

    Host Masters: IP & Autonomous System Numbers (ASN) Regional Internet Registries (RIR) (Local Internet Registries) ARIN (American Registry for Internet Numbers) RIPE NCC (Resaux IP Eurepeens Network Coordination Center) APNIC (Asia Pacific Network Information Center) AFRINIC (African Network Information Center) LATNIC (Latin American & Caribbean Network Information Center)

  • Root DNS Serverscom DNS serversorg DNS serversgr DNS serversntua.grDNS serversupatras.grDNS serversgoogle.comDNS serversibm.comDNS serversfreebsd.orgDNS servers & domain www.ece.ntua.gr (without cached entries/iterated):O nameserver (NS) L NS ISP O NS ISP root server .gr NSO NS ISP .gr NS .ntua.gr NSO NS ISP .ntua.gr NS ece.ntua.gr NSO NS ISP ece.ntua.gr NS www.ece.ntua.grece.ntua.grDNS servers

  • Name ServersName servers DNS.

    name servers Authoritative serversmaster (primary)slave (secondary)(Caching) recursive serverscaching forwardersMixture of functionality

  • Authoritative name server (authoritative) .

    master server (.. txt ( zone file)

    slave server (zone transfer) mastermasterslaveslave

  • Recursive name server recursive servers (lookups) DNS clients.

    authoritative servers clients not authoritative

    (cached)

  • DNS name resolution examplerequesting hostHome client PCroot DNS serverQuery: www.ibm.com123456authoritative DNS serverns.ibm.com78.com DNS serverlocal DNS server(recursive)iterative

  • A- query for IPv4 addressNS - query for the name servers responsible for a domainCNAME - check if the looked up hostname is an aliasMX - check for the mail exchanger of a domainPTR - query for the hostname of a given IP addressAAAA - query for IPv6 addressSOA - query for information about a specific zone - primary nameserver, contact email, defaul TTL, etc.

    AXFR - full zone transfer

    DNS Query Types

  • DNS recordsDNS: -resource records (RR)DNS caching: nameservers ttl (sec)

    The name field defines what domain name applies to the givenRR It specifies how long a domain resolver should cache the RR before it throws it out and asks a domain server again Defines the protocol family or an instance of the protocolThe type field specifies what type of data is in the RRData content of each record is defined by the type and class values

  • DNS protocol, messagesDNS protocol : , (format)Headeridentification: 16 bit # for query, reply to query uses same #flags:query or replyrecursion desired recursion availablereply is authoritative

  • DNS protocol, messagesName, type fields for a queryRRs in responseto queryrecords forauthoritative serversadditional helpfulinfo that may be used

  • Dig outpout1:10pm ~ # dig @147.102.13.10 -t A sofo.netmode.ntua.gr

    ; DiG 9.6.2-P2 @147.102.13.10 -t A sofo.netmode.ntua.gr; (1 server found);; global options: +cmd;; Got answer:;; ->>HEADER