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The Internet Protocol Suite

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The Internet Protocol Suite What is the Internet? Commercial worth of Internet G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk The 1969 Start of Internet project Time to get a market of 50 Million People: Internet 1983 ! 214 hosts (50 in Arpanet ; 164 in MilNet) 1990! 200,000 hosts (start of “Internet”) Radio took 38 years Protocol 1995! 7 M hosts (30 M users) 1997 22.5 M hosts (50 M users) TV took 13 years Suite 2004 250 M hosts (798 M users ; 1/6 world population) 2008 ??? The Internet took 4 years The Network Layer (IP) – Once opened to the general public One current estimate: The Interface Layers (e.g. Ethernet) ! 2,300 M Telephones ! 1,340 M Mobile phones Routing between networks ! 600 M PCs Statistics from the IITF Report released on April 15, 1998 Transport (TCP, UDP, and applications) The Emerging Digital Economy http://www.ecommerce.gov/emerging.htm Internet Protocol Stack IP Protocol Stack The Power of IP G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk Layering of Protocols Applications End-to-End Principle Middleware IP under everything email ftp web ! decouple transmission from application Transport chat ! networks (IS) do not care what they carry irc VoIP ! hosts (ES) do not care how it gets there TVoIP IP-hosts can control how they use the network Internet Protocol IP Profound impact on regulation client server Middleware FTP FTP TransportLinks Ethernet IP on everything Fibre 3G Physical IP Ethernet Enet Enet Ethernet Layer driver driver Some Internet Players People expect Internet connectivity Video/Multimedia is Important! G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk 40000 Applications Middleware 30000 Transport 20000 Internet “above the wire Protocol 10000 and below the application” “By the year 2016, no one under the age of forty will remember a world without personal computer. The Ambient Video (webcams) 0 TransportLinks average twenty year old will find it hard to imagine a Internet Video to TV 2008 2009 2010 2011 2012 2013 time when there wasn't any email to check or Web Internet Video to PC Physical Internet Voice sites to visit.” Internet Gaming Layer – George Christian, 2006. File Sharing Web/Email IP Appliances IP Packets G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk Messages (large blocks of data) Internet are split into smaller pieces, called “Packets” Protocol Each packet (PDU) has: A header (known as the PCI) The Connection-Less Network Service ! Well-defined format ! Destination address , source address, type, ... The 20 byte IP Packet Header A payload (known as the SDU) IP Network Layer Addresses ! A piece of the data to be communicated Name Resolution (name to IP Address) Internet Addresses IP Header Internet Architecture G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk 0 15 16 31 Arranged in four levels: 129.23.5.9 Addresses of End Systems ! Core Routers (No user networks connected) 4 IHL ToS/DSCP 16-bit total length ! Distribution Routers (Regional networks) 16-bit identification flags 13-bit fragment offset ! Access Routers (Internet Service Providers) 139.133.204.18 ! Home / Corporate networks TTL protocol 16-bit header checksum 32-bit source IP address 32-bit destination IP address options (if any) 20 bytes data 139.133.1.2 139.133.1.3 139.133.10.7 RFC 791 Internet Addresses OrganisationOrganisation of names of Names and and addresses Addresses G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst I need to send to: abdn.ac.uk There are two ways of identifying a computer, using: Name Resolution ! A name 139.133.204.18 ! A network address Name and Addresses Mail to: [email protected] Flat v. Hierarchical Structures Names and addresses may be organised using: The DNS ! A flat structure ! A hierarchical structure 139.133.1.2 139.133.1.3 139.133.10.7 Flat Structure The Telephone Numbering System The Domain name Service Tree Flat Structure ITU Telephone Numbering System G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst G Fairhurst root National Insurance Number us uk edu org com NZ 341865 B Country Albania UK Uganda USA Zim 355 44 256 1 263 Lon Man Area Abdn co ac ieee Batch of numbers 171 1224 1212 allocated to Serialan office number Exchange 27 49 Number indicates issuing bbc abdn ed office and nothing about individual Subscriber Line 2201 2497 www erg cs ITU E.164 geographic domains generic domains Flat v Hierarchical Structure Internet Email Evolution of the DNS Flat v Hierarchical Structure G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst Hierarchical! ! ! ! ! ! Flat I need to send to: A single file abdn.ac.uk ! /etc/hosts (in unix) 139.133.204.18 Easy to remember! ! ! ! Difficult to remember ! entered by person setting-up computer Abbreviated name possible! No unique abbreviations Mail to: A central file (at internic.arpa) Easy to find location of name! Only uniquely identifies [email protected] ! downloaded to /etc/hosts (using ftp) Difficult to change location!! Easy to change location Locally administer names! ! Names allocated centrally A distributed database ! clients send a request (query) e.g. telephone no. e.g. 139.133.1.2 139.133.1.3 139.133.10.7 Postcode social security no. ! a dns sends a response (resolution) IP name (DNS) IP address Most systems still also have a “/etc/hosts” and some also use a LAN name server DNS Stack Internet Email: dns query Internet Email: dns response G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk DNS Stub DNS dns stub resolver dns stub resolver Resolver Server 139.133.204.18 139.133.204.18 Mail to: I need to send to: [email protected] abdn.ac.uk I need to send to: abdn.ac.uk local dns server local dns server 139.133.1.2 139.133.1.2 client needs to resolve a “name” to an “address” “abdn.ac.uk” “abdn.ac.uk” to communicate to destination is 139.133.204.18 is 139.133.204.18 Sending the Email Recursive Lookup DNSDNS Client Client Cache Cache G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk Recursion asks server to do what is needed to resolve dns stub resolver dns stub resolver DNS Client Request Mail to:139.133.204.18 139.133.204.18 (recursion-bit set) 139.133.204.18 In Local Cache? No Yes Mail to: I need to send to: [email protected] abdn.ac.uk Cache entry Yes out of date? Fetch value from DNS server No local dns server Use cached local dns server (referrals without recursion-bit set) value Store in Cache 139.133.1.2 “uk” is W “uk.ac” “abdn. “abdn.ac.uk” is X ac.uk” is 139.133.204.18 is Y DNS Cache DNS Records DNS Resolution G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk DNS Records have various types: Browser/Application sends name to resolver (DNS client) dns cache MX records used for Mail Exchange “abdn.ac.uk” Resolver checks own cache (local files, etc) is 139.133.204.18 mail.abdn.ac.uk 3600 IN MX 500 backup.abdn.ac.uk mail.abdn.ac.uk 3600 IN MX 5 mailserver.abdn.ac.uk If not resolved, contacts DNS Server dns stub resolver mail.abdn.ac.uk 3600 IN MX 10 mailserver1.abdn.ac.uk (resolver knows this IP address) 139.133.204.18 Email uses the lowest numbered reachable mail server If not resolved, contacts root DNS server (.) May redirect to other server(s) Other formats also use the DNS: I need to send to: http://www.abdn.ac.uk Resolver given 1 or more addresses abdn.ac.uk ftp://ftp.abdn.ac.uk (resolver caches the answer for some time) sip://[email protected] local dns server Browser/Application given lowest numbered server dns cache “abdn.ac.uk” is 139.133.204.18 NamingNaming & Addressing: & Addressing Summary - Summary IP LANs G Fairhurst G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk A name is a symbol - designed for human reading An address is a data structure understood by a network Organisation may be hierarchical or flat Interface Layers (L1 & L2) A name server provides a service to change between network addresses and network names To know who's who on the Internet a computer must Encapsulation for Ethernet Addresses allocated to network as an address block know the address of a name server ! e.g. Aberdeen University allocated 139.133.x.x Address Resolution Protocol (arp) Each System (ES or IS): ! One (or more) unique IP address per NIC ! All addresses start with the same address prefix ! e.g. 139.133.1.5, 139.133.208.1 IP Interfaces Dynamic Host Configuration Protocol IP Address Allocation G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk G Fairhurst, http://www.erg.abdn.ac.uk Network Layer Sometimes a host doesn"t know its IP address Operating Quite common for dial-up, ADSL, etc ...
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