to circuit switching. Designed to avoid any failures. ◦ ARPANET -- Advanced Research Projects Agency Network -- the 1st packet switching (or store and foward) network (DARPA work) (split DDD/MILNET in 80's) i. internet precursor a. AlohaNet -- First wireless packet network i. Used packet radios, and led to CSMA leading to ethernet by Robert Metcalf (Xerox Parc-> 3com) ii. precursor to 1G+ mobile channels... for GPRS and SMS, AX.25 (amature X.25 -- packet switched WAN non ISO, non TCP/IP)
TCP/IP (co-inventor) / program manager of DARPA ◦ Moved to MCI (email), key figure in setting up ICANN (Internet Corporation for Assigned Numbers and Names), Internet Society, ... • Bob Kahn ◦ TCP/IP (co-inventor) ◦ BBN and first IMPs (interface Message Processor) , (ran ARAPNET routers), ... • Leonard Klienrock ◦ UCLA prof. -- queiueng theory (packet networks) ◦ Supervized first ARPANET connection at UCLA - '69 ◦ IMP build out and usage
(Request For Commments) editor ▪ intially idea flesh out for ARPANET or any DARPA research ▪ now memoradim of ITEF , sometimes standard ◦ coordinated IANA (Internet Assigned Numbers Authority) ◦ Setup NIC (Network Information Center) with SRI (Standford Research Institute) ▪ 1st DNS authority was the NIC ▪ Requested current DNS -- wrote by Paul Mockepetris in 1983
and Cron -- author of current versions ▪ BIND - from UCB unix, Berkely Internet Name Domain ◦ Founder of ISC -- Internet Systems Consortium (BIND, DHCP, internet survey report (ML), ...) ◦ co-inventor maintainer of MAPS (Mail Abuse Prevention System) ▪ 1st email spam blocking lists built on DNS ◦ ARIN board member ◦ Security/Stability member for ICANN
and Numbers a. Coordination of internet unique identifiers (Domains, IPs, ASNs, ...) b. SRI's NIC-->NSI --> ICANN(IANA) / (NSI-> Verisign) / ARIN c. Approves registries and registrars (EPP,DNS,whois) d. Oversee TLDs, root DNS servers (13), IP assignment, ASN(s) (for BGP between seperate networks) e. gTLD and ccTLD, and ...New generic TLD(s) .... a new era... i. current TLDs http:// www.iana. org/domains/root/db
a. oversee IPs, ASNs, WHOIS, Reverse DNS b. one of 5 RIR (Regional Internet Registries) • IANA - Internet Assigned Numbers Authority a. Ran by ICANN i. manages DNS root servers and .int, .arpa domains TLDs ii. manages global IPs and ASNs to individual RIRs like ARIN iii. Protocol Assignments (which sockets/ports/services)
(forward map), and IPs to Names (reverse mapping) ◦ With Millions of servers(hosts), unreliable networks, servers, no SPOFs -- how do we do it. ▪ Delegation / Authorization • hierarchical sctructure of data (zones) , any zone can be Delegated. This is a Tree structure of data. • Root Level Zones (historically gTLD & ccTLD...)
Domain must have authoritative HOST who is the master in terms of lookups ▪ Any level (or zone) can be delegated to another host. ▪ The top level is called the root level or zone ( each TLD zone is delegated to a registrar (as defined by ICANN for each gTLD, and to a country for each ccTLD) see http:// www.iana. org/domains/root/db
TCP/Ip port failback) • DNS DATA and RecordTypes ◦ SOA - Start of Authority Record name ttl class rr name-server email-addr (sn ref ret ex min) example.com. IN SOA ns.example.com. hostmaster.example.com. ( 2003080800 ; sn = serial number 172800 ; ref = refresh = 2d 900 ; ret = update retry = 15m 1209600 ; ex = expiry = 2w 3600 ; min = minimum = 1h ) ; the following are also valid using @ and blank @ IN SOA ns.example.com. hostmaster.example.com. ( IN SOA ns.example.com. hostmaster.example.com. (
zone file fragment for example.com $TTL 2d ; zone TTL default = 2 days or 172800 seconds $ORIGIN example.com. @ IN SOA ns.example.com. hostmaster.example.com. ( 2003080800 ; serial number 1d12h ; refresh = 1 day 12 hours 15M ; update retry = 15 minutes 3W12h ; expiry = 3 weeks + 12 hours 2h20M ; minimum = 2 hours + 20 minutes ) IN NS ns.example.com. IN NS ns.example.net. ... ; A record for ns.example.com. RR above ns IN A 192.168.2.1 ; the above could have been written as ; ns.example.com. IN A 192.168.2.1 ; ns.example.net is out-of-zone (or out-of-bailiwick) ; an A RRs is not required (and will be rejected if present) ◦ NS - Name Server name ttl class rr name example.com. IN NS ns1.example.com. ; the in-zone name server(s) have an A record ns1 IN A 192.168.0.3 ns2 IN A 192.168.0.3 ; name servers not in zone - no A records required IN NS ns1.example.net. IN NS ns1.example.org.
zone fragment for example.com $TTL 2d ; zone default = 2 days or 172800 seconds joe IN A 192.168.0.3 ; joe & www = same ip www IN A 192.168.0.3 ; functionally the same as the record above www.example.com. A 192.168.0.3 fred 3600 IN A 192.168.0.4 ; ttl overrides $TTL default ftp IN A 192.168.0.24 ; round robin with next • AAA - Address (Ipv60 ; zone fragment for example.com $TTL 2d ; zone default = 2 days or 172800 seconds $ORIGIN example.com. .... joe IN AAAA 2001:db8::3 ; joe & www = same ip www IN AAAA 2001:db8::3 ; functionally the same as the record above www.example.com. AAAA 2001:db8::3 fred 3600 IN AAAA 2001:db8::4 ; ttl =3600 overrides $TTL default ftp IN AAAA 2001:db8::5 ; round robin with next IN AAAA 2001:db8::6 mail IN AAAA 2001:db8::7 ; mail = round robin mail IN AAAA 2001:db8::32 mail IN AAAA 2001:db8::33
ttl class rr pref name example.com. IN MX 10 mail.example.com. IN MX 10 mail ; short form ; the line above is functionally the same as the line below ; example.com. IN MX 10 mail.example.com. ; any number of mail servers may be defined IN MX 20 mail2.example.com. ; use an external back-up IN MX 30 mail.example.net. ◦ PTR - Pointer (reverse -- opposite of A record) name ttl class rr name 15 IN PTR www.example.com. $TTL 2d ; 172800 secs $ORIGIN 23.168.192.IN-ADDR.ARPA. ; 2 below is actually an unqualified name and becomes ; 2.23.168.192.IN-ADDR.ARPA. 2 IN PTR joe.example.com. ; FDQN .... 15 IN PTR www.example.com. .... $ORIGIN 0.0.0.0.8.b.d.0.1.0.0.2.IP6.ARPA. ; the second name servers is ; external to this zone (domain). IN NS ns2.example.net. ; PTR RR maps a IPv6 address to a host name ; hosts in subnet ID 1 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0 IN PTR ns1.example.com.
mapped to Canocial Name $ORIGIN example.com. .... server1 IN A 192.168.0.3 www IN CNAME server1 ftp IN CNAME server1 ◦ TXT - text ◦ other special cases ( ▪ TTL on data, and via client server DNS software ▪ DNS Caching (at client, at hosts, .... recursive in nature) ▪ Recursive lookups ▪ DNS format types
text ◦ other special cases ( ▪ TTL on data, and via client server DNS software ▪ DNS Caching (at client, at hosts, .... recursive in nature) ▪ Recursive lookups ▪ TSEC, notify, txfr, ...
-- system for Domains and IPs ◦ simple telnet TCP/IP for data using authoritative server • examples ◦ whois webhero.com ◦ whois billmiller.tel ◦ whois 204.215.60.0 ▪ whois -h whois.arin.net NET-204-215-60-0-1
-- specify DNS servers ◦ /etc/nsswitch.conf -- order of DNS lookup (files,db, DNS) ◦ /etc/hosts -- flat file of hardcoded DNS lookups • DNS Server S/w ◦ BIND ◦ djbdns / tinydns -- by D. J. Bernstien
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