1. Overview1-1 Lec 1: Internet Overview ECE5650

2. Overview1-2 Intenet  Physical Connectivity  Topology  Access network and physical media  Layered Internet Protocol Stack  History

3. Overview1-3 What’s the Internet: “nuts and bolts” view  millions of connected computing devices: hosts = end systems  running network apps  communication links  fiber, copper, radio, satellite  transmission rate = bandwidth  routers: forward packets (chunks of data) local ISP company network regional ISP router workstation server mobile

4. Overview1-4 What’s the Internet: a service view  Distributed applications:  Web, email, games, e-commerce, file sharing  Network protocols: used by applications to control sending, receiving of msgs:  TCP, IP, HTTP, FTP, PPP  Internet standards RFC: Request for comments IETF: Internet Engineering Task Force  Communication services provided to apps:  Connectionless unreliable  connection-oriented reliable

5. Overview1-5 A closer look at network structure:  network edge: applications and hosts  network core:  routers  network of networks  access networks, physical media: communication links

6. Overview1-6 The network edge:  end systems (hosts):  run application programs  e.g. Web, email  at “edge of network”  Programs in end-systems use the serivce of the Internet to send msgs to each other  client/server model client host requests, receives service from always-on server; e.g. web, email  peer-peer model: minimal (or no) use of dedicated servers e.g. Gnutella, KaZaA, Skype, BitTorrent

7. Overview1-7 The Network Core  Physical connectivity of local area networks  mesh of interconnected routers  Logical connectivity: how is data transferred through net?

8. Overview1-8 Internet structure: network of networks  roughly hierarchical  at center: “tier-1” ISPs or Internet backbone networks (e.g., MCI, Sprint, AT&T, Cable and Wireless), national/international coverage, connect to large tier-2 ISPs and to all tier-1 ISPs and many customer networks. Tier 1 ISP Tier-1 providers interconnect (peer) privately NAP Tier-1 providers also interconnect at public Network Access Points (NAPs).

9. Overview1-9 Commercial Internet ISP Connectivity  Roughly hierarchical  Divided into tiers  Tier-1 ISPs are also called backbone providers, e.g., AT&T, Sprint, UUNet, Level 3, Qwest, Cable & Wireless  An ISP runs (private) Points of Presence (PoP) where its customers and other ISPs connect to it  E.g., MCI has 4,500 PoP  called private peering  ISPs also connect at (public) Network Access Point (NAP)  called public peering

10. Overview1-10 Internet structure: network of networks  “Tier-2” ISPs: smaller (often regional) ISPs  Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs  NAPs (Network Access Points) are complex high-speed switching networks often concentrated at a single building. Operated by 3rd party telecom or Internet backbone ISP-1.  PoPs (Points of Presence) are private group of routers within each ISP and used to connect it (peer it) with other up/down/equal ISPs and is the new trend in connectivity. Tier 1 ISP NAP Tier-2 ISP Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet, tier-2 ISP is customer of tier-1 provider Tier-2 ISPs also peer privately with each other, interconnect at public NAPs or private POPs.

11. Overview1-11 Internet structure: network of networks  “Tier-3” ISPs and local ISPs  last hop (“access”) network (closest to end systems) Tier 1 ISP NAP Tier-2 ISP local ISP local ISP local ISP local ISP local ISP Tier 3 ISP local ISP local ISP local ISP Local and tier- 3 ISPs are customers of higher tier ISPs connecting them to rest of Internet

12. Overview1-12 Internet structure: network of networks  a packet passes through many networks! Tier 1 ISP NAP Tier-2 ISP local ISP local ISP local ISP local ISP local ISP Tier 3 ISP local ISP local ISP local ISP

13. Introduction1-13 Tier-1 ISP: e.g., Sprint

14. Overview1-14 ATT Global Backbone IP Network From http://www.business.att.com

15. Overview1-15 MichNet: Statewide Backbone  Nation’s longest- running regional network  An 2.5 Gigabit (OC48c) backbone, with 24 backbone nodes  Two diverse 2.5 gigabit (2x OC48) to chicago  www.merit.edu/mn

16. Overview1-16

17. Overview1-17 Intenet  Physical Connectivity  Structure  Access network and physical media  Layered Internet Protocol Stack  History

18. Overview1-18 Access networks and physical media Q: How to connect end systems to edge router?  residential access nets  institutional access networks (school, company)  mobile access networks Keep in mind:  bandwidth (bits per second) of access network?  shared or dedicated?

19. Overview1-19 Residential access: point to point access  Dialup via modem  Uses existing telephony infrastructure; Home is connected to central office  up to 56Kbps direct access to router (often less)  Can’t surf and phone at same time: can’t be “always on” telephone network Internet home dial-up modem ISP modem (e.g., AOL) home PC central office

20. Overview1-20  ADSL: asymmetric digital subscriber line  up to 1 Mbps upstream (today typically < 256 kbps)  up to 8 Mbps downstream (today typically < 1 Mbps)  FDM: 50 kHz - 1 MHz for downstream 4 kHz - 50 kHz for upstream 0 kHz - 4 kHz for ordinary telephone telephone network DSL modem home PC home phone Internet DSLAM Existing phone line: 0-4KHz phone; 4-50KHz upstream data; 50KHz-1MHz downstream data splitter central office

21. Overview1-21 Residential access: cable modems  HFC: hybrid fiber coax  asymmetric: up to 30Mbps downstream, 2 Mbps upstream  network of cable and fiber attaches homes to ISP router  homes share access to router so communication activity is visible to each other.  deployment: available via cable TV companies

22. Overview1-22 Residential access: cable modems Diagram: http://www.cabledatacomnews.com/cmic/diagram.html

23. Overview1-23 Cable Network Architecture: Overview home cable headend cable distribution network (simplified) Typically 500 to 5,000 homes

24. Overview1-24 Cable Network Architecture: Overview home cable headend cable distribution network (simplified)

25. Overview1-25 Cable Network Architecture: Overview home cable headend cable distribution network server(s)

26. Overview1-26 Cable Network Architecture: Overview home cable headend cable distribution network Channels VIDEOVIDEO VIDEOVIDEO VIDEOVIDEO VIDEOVIDEO VIDEOVIDEO VIDEOVIDEO DATADATA DATADATA CONTROLCONTROL 1234 56789 FDM:

27. Overview1-27 Company access: local area networks  company/univ local area network (LAN) connects end system to edge router  Ethernet:  shared or dedicated link connects end system and router  10 Mbs, 100Mbps, Gigabit Ethernet  LANs: chapter 5

28. Overview1-28 Wireless access networks  shared wireless access network connects end system to router  via base station aka “access point”  wireless LANs:  802.11a/b/g (WiFi): 11 Mbps ~54Mbps  802.11n: 100~200Mbps (theoretically up to 300Mbps)  wider-area wireless access  provided by telco operator  3G ~ 384 kbps Will it happen??  WAP/GPRS in Europe  WiMAX  ~100Mbps  ~10 miles base station mobile hosts router

29. Introduction1-29 Home networks Typical home network components:  DSL or cable modem  router/firewall/NAT  Ethernet  wireless access point wireless access point wireless laptops router/ firewall cable modem to/from cable headend Ethernet

30. Introduction1-30 Physical Media  Bit: propagates between transmitter/rcvr pairs  physical link: what lies between transmitter & receiver  guided media:  signals propagate in solid media: copper, fiber, coax  unguided media:  signals propagate freely, e.g., radio Twisted Pair (TP)  two insulated copper wires  Category 3: traditional phone wires, 10 Mbps Ethernet  Category 5: 100Mbps Ethernet

31. Introduction1-31 Physical Media: coax, fiber Coaxial cable:  two concentric copper conductors  bidirectional  baseband:  single channel on cable  legacy Ethernet  broadband:  multiple channels on cable  HFC Fiber optic cable:  glass fiber carrying light pulses, each pulse a bit  high-speed operation:  high-speed point-to-point transmission (e.g., 10’s- 100’s Gps)  low error rate: repeaters spaced far apart ; immune to electromagnetic noise

32. Introduction1-32 Physical media: radio  signal carried in electromagnetic spectrum  no physical “wire”  bidirectional  propagation environment effects:  reflection  obstruction by objects  interference Radio link types:  terrestrial microwave  e.g. up to 45 Mbps channels  LAN (e.g., Wifi)  11Mbps, 54 Mbps  wide-area (e.g., cellular)  3G cellular: ~ 1 Mbps  satellite  Kbps to 45Mbps channel (or multiple smaller channels)  270 msec end-end delay  geosynchronous versus low altitude

33. Overview1-33 Intenet  Physical Connectivity  Topology  Access network and physical media  Layered Internet Protocol Stack  History

34. Overview1-34 What’s a protocol? human protocols:  “what’s the time?”  “I have a question”  introductions network protocols:  machines rather than humans  all communication activity in Internet governed by protocols A protocol is a set of rules that govens how two or more communicating parties are to interact. It defines: - msg format - order of msgs sent & received - actions taken on msg transmission & receipt

35. Protocol “Layers” Networks are complex!  many “pieces”:  hosts  routers  links of various media  applications  protocols  hardware, software  Layered Protocol  Modular approach to network functionality  Examples: Taking an airplane trip Mailing service Overview1-35

36. Overview1-36 Internet protocol stack  application: supporting network applications  FTP, SMTP, HTTP  transport: process-process data transfer  TCP, UDP  network: host-host data transfer  IP  link: data transfer between neighboring network elements  PPP, Ethernet  physical: bits “on the wire” application transport network link physical

37. Overview1-37 message segment datagram frame source application transport network link physical HtHt HnHn HlHl M HtHt HnHn M HtHt M M destination application transport network link physical HtHt HnHn HlHl M HtHt HnHn M HtHt M M network link physical link physical HtHt HnHn HlHl M HtHt HnHn M HtHt HnHn HlHl M HtHt HnHn M HtHt HnHn HlHl M HtHt HnHn HlHl M router switch Encapsulation

38. Characteristics of Layering  Layering positives:  Each layer relies on services from layer below and exports services to layer above  Interface defines interaction  Hides implementation - layers can change without disturbing other layers (black box)  Layering negatives: duplicate functionality and inter-dependency. Overview1-38

39. Overview1-39 Internet History  1961: Kleinrock - queueing theory shows effectiveness of packet- switching  1964: Baran - packet- switching in military nets  1967: ARPAnet conceived by Advanced Research Projects Agency  1969: first ARPAnet node operational  1972:  ARPAnet demonstrated publicly  NCP (Network Control Protocol) first host- host protocol  first e-mail program  ARPAnet has 15 nodes 1961-1972: Early packet-switching principles

40. Overview1-40 Initial ARPANET  1965-1968  ARPANET plan, implemented by BBN (Bolt, Beranek, Newman): packet switch to build IMP  1969  ARPANET commissioned: 4 nodes, 50kbps

41. Overview1-41 Initial Expansion of the ARPANET Dec. 1969Mar. 1971July 1970 Apr. 1972 Sept. 1972 RFC 527: ARPAWOCKY; RFC 602: The Stockings Were Hung by the Chimney with Care

42. Overview1-42 Internet History  1970: ALOHAnet satellite network in Hawaii  1973: Metcalfe’s PhD thesis proposes Ethernet  1974: Cerf and Kahn – archi. for interconnecting networks  Initially, named NCP  Later, split to TCP/IP  late70’s: proprietary architectures: DECnet, SNA, XNA  late 70’s: switching fixed length packets (ATM precursor)  1979: ARPAnet has 200 nodes Cerf and Kahn’s internetworking principles:  minimalism, autonomy - no internal changes required to interconnect networks  best effort service model  stateless routers  decentralized control define today’s Internet architecture 2005 ACM Turing Award “A protocol for packet network interconnection”, IEEE Trans. on Communications Technology, vol.22(5), 627-641 1972-1980: Internetworking, new and proprietary nets

43. Overview1-43 Internet History  1983: deployment of TCP/IP  1982: SMTP e-mail protocol defined  1983: DNS defined for name-to-IP- address translation  1985: FTP protocol defined  1988: TCP congestion control  new national networks: Csnet, BITnet, NSFnet, Minitel  100,000 hosts connected to confederation of networks 1980-1990: new protocols, a proliferation of networks

44. Overview1-44 Internet History  Early 1990’s: ARPAnet decommissioned  1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995)  1992, 1 million hosts  early 1990s: Web  hypertext [Bush 1945, Nelson 1960’s]  HTML, HTTP: Berners-Lee  1994: Mosaic, later Netscape  late 1990’s: commercialization of the Web Late 1990’s – 2000’s:  more killer apps: instant messaging, peer2peer file sharing (e.g., BitTorrent, YouTube)  network security to forefront  Today:  400 million users, 150 countries  backbone links running at 10 Gbps 1990, 2000’s: commercialization, the Web, new apps

45. Overview1-45 Number of Hosts on the Internet: Aug. 1981 213 Oct. 1984 1,024 Dec. 1987 28,174 Oct. 1990 313,000 Jul. 1993 1,776,000 Jul. 1996 19,540,000 Jul. 1999 56,218,000 Jul. 2004 285,139,000 Jan. 2005 317,646,000 Jul. 2005 353,284,000 About 2B users out of 6.8B people, from 16M in 1995, 350M in 2000,1B in 2005 Growth of the Internet

46. Overview1-46 Summary  Physical Connectivity  Topology  Access network and physical media  Layered Internet Protocols  History