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W4140 Network Laboratory Lecture 3 Sept 18 - Fall 2006 Shlomo Hershkop Columbia University

W4140 Network Laboratory Lecture 3 Sept 18 - Fall 2006 Shlomo Hershkop Columbia University. Announcements. Lab division I will be updating the webpage with lab groups, if everyone in the room would like to move the lab around a little, that is ok Labs reports

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W4140 Network Laboratory Lecture 3 Sept 18 - Fall 2006 Shlomo Hershkop Columbia University

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  1. W4140 Network LaboratoryLecture 3Sept 18 - Fall 2006Shlomo HershkopColumbia University

  2. Announcements • Lab division • I will be updating the webpage with lab groups, if everyone in the room would like to move the lab around a little, that is ok • Labs reports • are due generally when the next lab starts…contact me if you need more time. Single report per group, zipped and uploaded to TA through courseworks….include relevant information and name the files using some logical system. README should include everyone’s names and cunix ID • Lab pre-work/post • courseworks will have the prelabs, which need to be completed BEFORE your lab starts…individual work….post labs are to be submitted online (courseworks) by beginning of next lab (or earlier please)…. • Lab 1 pre work was not collected, practice one…. • reading list: • lab 2 • chapter 2 (see resources)

  3. The Evolution of Internet Introductory material. An overview lecture that covers Internet related topics, including a definition of the Internet, an overview of its history and growth, and standardization and naming.

  4. A Definition • On October 24, 1995, the FNC unanimously passed a resolution defining the term Internet. • RESOLUTION: The Federal Networking Council (FNC) agrees that the following language reflects our definition of the term "Internet"."Internet" refers to the global information system that -- • (i) is logically linked together by a globally unique address space based on the Internet Protocol (IP) or its subsequent extensions/follow-ons; • (ii) is able to support communications using the Transmission Control Protocol/Internet Protocol (TCP/IP) suite or its subsequent extensions/follow-ons, and/or other IP-compatible protocols; and • (iii) provides, uses or makes accessible, either publicly or privately, high level services layered on the communications and related infrastructure described herein.

  5. 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

  6. Internet History 1970: ALOHAnet satellite network in Hawaii 1973: Metcalfe’s PhD thesis proposes Ethernet 1974: Cerf and Kahn - architecture for interconnecting networks 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 1972-1980: Internetworking, new and proprietary nets

  7. Internet History Early 1990’s: ARPAnet decommissioned 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) 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, P2P file sharing network security to forefront est. 50 million host, 100 million+ users backbone links running at Gbps 1990, 2000’s: commercialization, the Web, new apps

  8. Applications of the Internet • Traditional core applications:Email News Remote Login File Transfer • The killer application:World-Wide Web (WWW), P2P • Future applications:Videoconferencing and Telephony Multimedia Services Internet Broadcast

  9. Growth of the Internet Source: Internet Software Consortium

  10. Internet Infrastructure

  11. Internet Infrastructure • The infrastructure of the Internet consists of a federation of connected networks that are each independently managed (“autonomous system”) • Note: Each “autononmous system may consist of multiple IP networks • Hierarchy of network service providers • Tier-1: nation or worldwide network (US: less than 20) • Tier-2: regional networks (in US: less than 100) • Tier-3: local Internet service provider (in US: several thousand)

  12. Internet Infrastructure • Location where a network (ISP, corporate network, or regional network) gets access to the Internet is called a Point-of-Presence (POP). • Locations (Tier-1 or Tier-2) networks are connected for the purpose of exchanging traffic are called peering points. • Public peering: Traffic is swapped in a specific location, called Internet exchange points (IXPs) • Private peering: Two networks establish a direct link to each other.

  13. Tier-1 ISP: e.g., Sprint Sprint US backbone network

  14. Who is Who on the Internet ? • Internet Society (ISOC):Founded in 1992, an international nonprofit professional organization that provides administrative support for the Internet. Founded in 1992, ISOC is the organizational home for the standardization bodies of the Internet. • Internet Engineering Task Force (IETF): Forum that coordinates the development of new protocols and standards. Organized into working groups that are each devoted to a specific topic or protocol. Working groups document their work in reports, called Request For Comments (RFCs). • IRTF (Internet Research Task Force):The Internet Research Task Force is a composed of a number of focused, long-term and small Research Groups. • Internet Architecture Board (IAB): a technical advisory group of the Internet Society, provides oversight of the architecture for the protocols and the standardization process • The Internet Engineering Steering Group (IESG): The IESG is responsible for technical management of IETF activities and the Internet standards process. Standards. Composed of the Area Directors of the IETF working groups.

  15. Internet Standardization Process • Working groups present their work i of the Internet are published as RFC (Request for Comments). • RFCs are the basis for Internet standards. • Not all RFCs become Internet Standards ! (There are >3000 RFCs and less than 70 Internet standards • A typical (but not only) way of standardization is: • Internet Drafts • RFC • Proposed Standard • Draft Standard (requires 2 working implementation) • Internet Standard (declared by IAB)

  16. Assigning Identifiers for the Internet • Who gives University the domain name “netlab.edu” and who assigns it the network prefix “128.143.0.0/16”? Who assigns port 80 as the default port for web servers? • The functions associated with the assignment of numbers is referred to as Internet Assigned Number Authority (IANA). • Early days of the Internet: IANA functions are administered by a single person (Jon Postel). Today: • Internet Corporation for Assigned Names and Numbers (ICANN) assumes the responsibility for the assignment of technical protocol parameters, allocation of the IP address space, management of the domain name system, and others. • Management of IP address done by Regional Internet Registries (RIRs): • APNIC (Asia Pacific Network Information Centre) • RIPE NCC (Réseaux IP Européens Network Coordination Centre) • ARIN (American Registry for Internet Numbers) Domain names are administered by a large number of private organizations that are accredited by ICANN.

  17. Summary • Layered Internet architecture • Reduce complexity • Higher layer views lower layer as service provider • Application layer, transport layer, network layer, and link layer

  18. IP Addressing Next: • IP addressing • Data link protocols and ARP • Notes about lab

  19. IP Addressing • Addressing defines how addresses are allocated and the structure of addresses • IPv4 • Classful IP addresses (obsolete) • Classless inter-domain routing (CIDR) (RFC 854, current standard) • IP Version 6 addresses

  20. What is an IP Address? • Why Addresses? • End-to-end argument (principle) • Reading: http://web.mit.edu/Saltzer/www/publications/endtoend/endtoend.pdf • Keep it Simple, Stupid

  21. What is an IP Address? • An IP address is a unique global address for a network interface. • An IP address uniquely identifies a network location. • http://www.arin.net/whois • http://www.iana.org/ipaddress/ip-addresses.htm • Routers forwards a packet based on the destination address of the packet.

  22. IPv4 Addresses

  23. IP v.4 Addresses 32 bits 0x4 0x5 0x00 44 10 9d08 010 0000000000000 2 2 128 0x06 8bff 10 128.143.137.144 128.143.71.21

  24. IP v.4 Addressing • An IP address is often written in dotted decimal notation • Each byte is identified by a decimal number in the range [0..255]: 10000000 10001111 10001001 10010000 1st Byte = 128 2nd Byte = 143 3rd Byte = 137 4th Byte = 144 128.143.137.144

  25. Structure of an IP address • An IP address encodes both a network number (network prefix) and an interface number (host number). • network prefix identifies a network • the host number identifies a specific host (actually, interface on the network). 31 0 network prefix host number

  26. How long the network prefix is? • Before 1993: The network prefix is implicitly defined (class-based addressing) • After 1993: The network prefix is indicated by a netmask.

  27. Before 1993: Class-based addressing • The Internet address space was divided up into classes: • Class A:Network prefix is 8 bits long • Class B:Network prefix is 16 bits long • Class C:Network prefix is 24 bits long • Class D is multicast address • Class E is reserved

  28. Classful IP Adresses (Until 1993) • Each IP address contained a key which identifies the class: • Class A:IP address starts with “0” • Class B:IP address starts with “10” • Class C:IP address starts with “110” • Class D:IP address starts with “1110” • Class E:IP address starts wit “11110”

  29. The old way: Internet Address Classes

  30. The old way: Internet Address Classes

  31. The old way: Internet Address Classes

  32. Problems with Classful IP Addresses • Fast growing routing table size • Each router must have an entry for every network prefix • ~ 221 = 2,097,152 class C networks • In 1993, the size of routing tables started to outgrow the capacity of routers

  33. Other problems with classful addresses • Address depletion for large networks • Class A and Class B addresses were gone • How many class A/B network prefixes can there be? • Limited flexibility for network addresses: • Class A and B addresses are overkill (>64,000 addresses) • Class C address is insufficient (256 addresses)

  34. Classless Inter-domain routing (CIDR) 1993 • Full description RFC 1518 & 1519 • Network prefix is of variable length • Addresses are allocated hierarchically • Routers aggregate multiple address prefixes into one routing entry to minimize routing table size

  35. CIDR network prefix is variable length • A network mask specifies the number of bits used to identify a network in an IP address. • How? 144 16 128 59 Addr 10000000 10001111 10001001 10010000 255 255 0 255 Mask 11111111 11111111 1111111 00000000

  36. CIDR notation • CIDR notation of an IP address: • 128.143.137.144/24 • /24 is the prefix length. It states that the first 24 bits are the network prefix of the address (and the remaining 8 bits are available for specific host addresses) • CIDR notation can nicely express blocks of addresses • An address block [128.195.0.0, 128.195.255.255] can be represented by an address prefix 128.195.0.0/16 • How many addresses are there in a /x address block? • 2 (32-x)

  37. CIDR hierarchical address allocation 128.0.0.0/8 ISP • IP addresses are hierarchically allocated. • An ISP obtains an address block from a Regional Internet Registry • An ISP allocates a subdivision of the address block to an organization • An organization recursively allocates subdivision of its address block to its networks • A host in a network obtains an address within the address block assigned to the network 128.59.0.0/16 128.1.0.0/16 128.2.0.0/16 University 128.59.16.150 Foo.com Bar.com CS Library 128.59.16.0/24 128.59.44.0/24

  38. Hierarchical address allocation 128.59.16.[0 – 255] • ISP obtains an address block 128.0.0.0/8  [128.0.0.0, 128.255.255.255] • ISP allocates 128.59.0.0/16 ([128.59.0.0, 128.59.255.255]) to the university. • University allocates 128.59.16.0/24 ([128.59.16.0, 128.59.16.255]) to the CS department’s network • A host on the CS department’s network gets one IP address 128.59.16.150 128.59.16.150 128.59.0.0 – 128.59.255.255 128.0.0.0 - 128.255.255.255

  39. CIDR allows route aggregation I 128.0.0.0/8 ISP1 • ISP1 announces one address prefix 128.0.0.0./8 to ISP2 • ISP2 can use one routing entry to reach all networks connected to ISP1 You can reach 128.0.0.0/8 via ISP1 128.0.0.0/8 ISP3 ISP1 128.1.0.0/16 128.2.0.0/16 128.59.0.0/16 University Foo.com Bar.com CS Library

  40. CIDR summary • A network prefix is of variable length: a.b.c.d/x • Addresses are hierarchical allocated • Routers aggregate multiple address prefixes into one routing entry to minimize routing table size. • Security is still an issue • Secure Routing & Path validation

  41. What problems CIDR does not solve (I) 204.1.0.0/16 ISP1 128.0.0.0/8 ISP1 You can reach 128.0.0.0/8 And 204.1.0.0/16 via ISP1 • An multi-homing site still adds one entry into global routing tables ISP3 ISP1 ISP2 128.0.0.0/8 204.0.0.0/8 204.1.0.0/16 Mutil-home.com 204.1.0.0/16

  42. What problems CIDR does not solve (II) 204.1.0.0/16 ISP1 You can reach 128.0.0.0/8 And 204.1.0.0/16 via ISP1 • A site switches provider without renumbering still adds one entry into global routing tables ISP3 ISP1 ISP2 128.0.0.0/8 204.0.0.0/8 128.0.0.0/8 ISP1 204.1.0.0/16 Switched.com 204.1.0.0/16

  43. Global routing tables continue to grow Source: http://bgp.potaroo.net/as4637/

  44. Special IPv4 Addresses • Reserved or (by convention) special addresses: Loopback interfaces • all addresses 127.0.0.1-127.255.255.255 are reserved for loopback interfaces • Most systems use 127.0.0.1 as loopback address • loopback interface is associated with name “localhost” Broadcast address • Host number is all ones, e.g., 128.143.255.255 • Broadcast goes to all hosts on the network • Often ignored due to security concerns • Test / Experimental addresses • 10.0.0.0 - 10.255.255.255 • 172.16.0.0 - 172.31.255.255 • 192.168.0.0 - 192.168.255.255 • Convention (but not a reserved address) Default gateway has host number set to ‘1’, e.g., 128.195.4.1

  45. Special IPv4 Addresses (RFC 3330)

  46. IP Addressing (Summary) • Addressing defines how addresses are allocated and the structure of addresses • IPv4 • Classful IP addresses (obsolete) • Classless inter-domain routing (CIDR) (current standard) • IP Version 6 addresses

  47. IPv6 - IP Version 6 • IP Version 6 • Designed to be the successor to the currently used IPv4 • Specification completed in 1994 • Makes improvements to IPv4 (no revolutionary changes) • One (not the only !) feature of IPv6 is a significant increase in of the IP address to 128 bits (16 bytes) • IPv6 will solve – for the foreseeable future – the problems with IP addressing • 1024 addresses per square inch on the surface of the Earth.

  48. IPv6 Header

  49. Notation of IPv6 addresses • Convention: The 128-bit IPv6 address is written as eight 16-bit integers (using hexadecimal digits for each integer) CEDF:BP76:3245:4464:FACE:2E50:3025:DF12 • Short notation: Abbreviations of leading zeroes: CEDF:BP76:0000:0000:009E:0000:3025:DF12  CEDF:BP76:0:0:9E :0:3025:DF12 “:0000:0000:0000” can be written as “::” CEDF:BP76:0:0:FACE:0:3025:DF12  CEDF:BP76::FACE:0:3025:DF12

  50. IPv4 address in IPv6 • IPv6 addresses derived from IPv4 addresses have 96 leading zero bits. • Convention allows to use IPv4 notation for the last 32 bits. ::80:8F:89:90  ::128.143.137.144

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