Department of Computer Science Institute for System Architecture, Chair for Computer Networks Internet Services & Protocols An Introduction to the Internet Dr.-Ing. Stephan Groß Room: INF 3099 E-Mail: stephan.gross@tu-dresden.de
Overview Course objective Profound introduction to both traditional and new applications of the Internet and their demands Technical and methodical foundations of common Internet services Traditional applications and protocols versus new developments Not in this course How to use services Network Basics (Prof. Schill) Security Basics (Prof. Pfitzmann) 2
What are we talking about? Internet & Services Protocols 3
The Internet Once upon a time 1974 Specification of TCP 1973 First international link installed 1988 1982 1994 First Internet worm TCP/IP First commercial 1958 established as WWW sites Advanced 1986 standard protocol Research Project IETF & IRTF 1991 1972 suite Agency (ARPA) founded WWW Email becomes founded 1966 1979 1995 quick hit 1984 1990 First ARPANET USENET and first WWW becomes ALOHANET DNS ARPANET ceases plan MUD most popular connected introduced to exist Internet service 1957 1970 1978 1983 1989 2000 USSR launches First cross-country TCP split into TCP First name server Germany Massive DoS Sputnik link installed and IP connected to the attacks against NSFNET major web sites 1950 1960 1970 1971 23 hosts connected 1980 1990 1984 1.000 hosts connected 1989 100.000 hosts connected 1987 10.000 hosts connected 2000 1992 1.000.000 hosts connected 2000 100.000.000 hosts connected 4
The Internet A Nuts-and-Bolts description Worldwide system of interconnected computer networks Millions of connected hosts running network apps Connected networks may be based on disparate network technologies, e.g. copper, fibre, radio, satellite (even carrier pigeons ;-) Standardized Internet Protocol (IP) used to unify different low-level protocols Carries various information and services, e.g. Mail, FTP or WWW Internet World Wide Web 5
The Internet A Nuts-and-Bolts description Routers: forward packets (= chunks of data) Protocols control sending and receiving of messages e.g. TCP, IP, HTTP, FTP, PPP router server workstation mobile local ISP Internet=network of networks Loosely hierarchical Public Internet vs. private intranet regional ISP Internet standards RFC: Request for comment IETF: Internet Engineering Task Force company network 6
The Internet Protocol Hourglass email WWW phone... SMTP HTTP RTP... TCP UDP IP ethernet PPP CSMA async sonet... copper fiber radio... (S. Deering) User Application End-to-end Application Protocol Transport Protocol Internet Layer Media Access Protocol Media Format Physical System 7
Why use an IP Adaption Layer? Why an Internet Layer? Different types of networks may be connected Consistent global addressing Implements a virtual network to isolate end-to-end protocols from network's details and changes Why only one Transmission Protocol? Maximizes the interoperability Minimizes the number of service interfaces Why a narrow Internet Protocol? Comprises the smallest set of common network functionality to increase the numbers of connectable networks email WWW phone... SMTP HTTP RTP... TCP UDP IP ethernet PPP CSMA async sonet... copper fiber radio... 8
Key benefits of the IP Adaption Layer Easy to adapt to new media IP Address to MAC address resolution IP packet framing definition And its done! Easy to create composite networks email WWW phone... SMTP HTTP RTP... TCP UDP Ethernet ATM SDH Ethernet wireless Easy to scale IP networks are composite networks No single coordinated effort required Minimal interdependencies between component networks Very simple network-to-network interface Easy to create applications in IP Applications do not need to understand or adapt to varying transport characteristics IP ethernet PPP CSMA async sonet... copper fiber radio... 9
But the world is changing and IP is growing older The increasing commercialization and new applications make different demands on the Internet architecture: Demand Bases different services for multimedia, data transfer QoS (IntServ, DiffServ) new kinds of services P2P (peer to peer) networks, CDNs Lots of Systems and Addresses IPv6 Support for Security IPsec Support for Mobility Mobile IP 10
IP is putting on weight... email WWW phone... SMTP HTTP RTP... TCP UDP... more and more functionality from underlying networks is required IP + mcast + QoS +... ethernet PPP CSMA async sonet... copper fiber radio... 11
Mid-Life Identity Crisis The Introduction of a V6 transition into IP Doubles number of service interfaces Requires changes in layers above and below IP Creates interoperability problems email WWW phone... SMTP HTTP RTP... TCP UDP IP4 IP6 ethernet PPP CSMA async sonet... copper fiber radio... 12
Maltreating IP Network Address Translators (NATs) and Application Level Gateways (ALGs) used to glue together the broken pieces Lots of kinds of new glue being invented ruins predictability and makes applications more complex Some applications remain broken, since the NAT glue does not provide fully transparent connectivity email WWW phone... SMTP HTTP RTP... TCP UDP IP IP ethernet PPP CSMA async sonet... copper fiber radio... 13
Is IP dying? Dependencies between specific link-layers reduce flexibility and further development IP won't be replaced at all, but complicated hybrid architecture and new addressing is needed email WWW phone... SMTP HTTP RTP... TCP UDP IP ATM ethernet CSMA async sonet... copper fiber radio... 14
Internet Protocol Stack Original Internet Protocol stack contains ISO/ OSI layer 1, 2, 3, 4 and 7 Application layer: supports network applications FTP, SMTP, HTTP Transport layer: transporting messages between client and server Application layer Transport layer Network layer TCP, UDP Network layer: routing and delivering of datagrams IP, routing protocols Link layer: data transfer between neighbouring network nodes Link layer Physical layer Ethernet, PPP Physical layer: Bits on the wire 15
Internet Protocol Stack in change Result of newly developed protocols: Getting new layers Add XML as an description language like ASN.1 (OSI) to the presentation layer Add of RTSP and SIP to the session layer Protocol tunneling IP over IP, IPv6 over IP Division of layers Layer 2.5: MPLS email WWW... HTTP RTP... TCP UDP IP ethernet PPP CSMA sonet... copper fiber... IP over IP tunnelling 16
The body shape changes with surprising results!(g. Huston) Email WWW Voice... SMTP HTTP RTP... TCP UDP IP Frame, ATM, Sonet... The addition of MPLS to the protocol model has caused some surprising outcomes in terms of using MPLS and IP as a substrate for emulated wire services It is not obvious that this form of complexity is a reliable foundation for a scalable network architecture MPLS IP Ethernet PPP MultiAccess async sync... copper fiber radio... 17
The body shape changes with surprising results!(g. Huston) Email WWW Voice... SMTP HTTP RTP... TCP UDP IP HTTPS... TCP UDP IP Ethernet PPP MultiAccess async sync... copper fiber radio... IP over HTTPS (RFC3093) is now a popular solution for firewall traversal. Any level of a layered network model can be seen as functionally equivalent to any other layer it all depends on the committee that standardized it. The temptation to solve a problem by adding another layer of indirection is a fine example of computer science However, it does not always create robust networking architectures 18
Survival of the Fittest? Maybe we can trim down from an hourglass to a wineglass First signs: IP-over-SONET IP-over-WDM IPv6 necessary to restore simplicity and functionality email WWW phone... SMTP HTTP RTP... TCP UDP IP6 Time will tell... copper fiber radio... 19
Protocol layers and data Each layer...... takes data from the layer above... prepends protocol information (Header) and creates new PDU (Protocol Data Unit)... passes new PDU to the layer below and vice versa D HT D HN HT D HL HN HT D Source Destination Application Application Transport Transport Network Network Link Link Physical Physical D Message D HT D HT HN Segment D HT HN HL Frame Datagram 20
Internet Model: Datagram Network Network layer does not establish connections Router, thus no end-to-end connection states Packets are routed hop-by-hop based on their destination addresses Packets with same source and destination might be routed differently Packets are transferred using best-effort service Core only contains router and communication links, end systems at the edge 21
A Network of Networks National/international backbone provider (NBPs) e.g. Deutsche Telekom Connected in direct way (peering) or over public Network Access Points (NAPs) NAP Regional ISPs Connections to NBPs Local ISP companies Connected to regional ISPs local ISP regional ISP NBP B NAP NBP A regional ISP local ISP 22
The Traditional Hierarchical View Segmentation of internet providers into a number of 'tiers' Each ISP purchases service from a single provider at the next higher tier Each ISP sells service to multiple customers at the next lower tier End User End User Littler ISP End User Littler ISP Little ISP End User Littler ISP Little ISP Big ISP End User Littler ISP Little ISP Big ISP End User Littler ISP Little ISP Big ISP By Geoff Huston 23
Hierarchical Evolution Tiers and Multi-homing This hierarchy has been evolving due to competitive pressures in the provider market and opportunities for lateral peering May use two or more upstream providers (multi-homing) May use peering within a tier End User End User Littler ISP End User Littler ISP Little ISP Littler ISP Little ISP Big ISP Peering Links End User End User Littler ISP Little ISP Big ISP End User Littler ISP Little ISP Big ISP Multi-homing links By Geoff Huston 24
What are we talking about? Internet & Services Protocols 25
Internet Services Communication infrastructure enables distributed apps Web, Email, games, ecommerce, egovernment, file sharing Communication services provided to apps: Connectionless unreliable (UDP) Connection-oriented reliable (TCP) 26
Some cool Internet appliances Web-enabled toaster + weather forecaster IP picture frame http://www.ceiva.com/ World s smallest web server http://www-ccs.cs.umass.edu/~shri/ipic.html Internet phones 27
What are we talking about? Internet & Services Protocols 28
Human Protocols What's the time? I have a question. May I introduce myself to you? Diplomatic protocols... specific message sent... specific actions taken when messages received, or other events happen 29
Network Protocols Machines rather than humans interacting All communication interactivity in Internet governed by protocols Control sending/receiving messages and actions taken Protocols define format and order of messages sent or received among network entities, and actions taken on message transmission. 30
A simple example Hi TCP connection request Hi TCP connection response Got the time? Get http://www.awl.com/kurose-ross 2:00 <file> time 31
Introduction: Summary First impression of the Internet History of the Internet Key benefits of the Internet Protocol What is a protocol 32
Homework: Why not reinventing the Internet? Economist Technology Quarterly (03/06) Vol. 378, No. 8468, P. 32 33