1. 1 Review of Important Networking Concepts Introductory material. This module uses the example from the previous module to review important networking concepts: protocol architecture, protocol layers, encapsulation, demultiplexing, network abstractions.

2. 2 Networking Concepts Layered Architecture to reduce complexity –Encapsulation –Abstractions

3. 3 Sending a packet from Argon to Neon

4. 4 DNS: The IP address of “neon.tcpip-lab.edu ” is 128.143.71.21 ARP: What is the MAC address of 128.143.137.1? Sending a packet from Argon to Neon DNS: What is the IP address of “neon.tcpip-lab.edu ” ? ARP: The MAC address of 128.143.137.1 is 00:e0:f9:23:a8:20 128.143.71.21 is not on my local network. Therefore, I need to send the packet to my default gateway with address 128.143.137.1 frame 128.143.71.21 is on my local network. Therefore, I can send the packet directly. ARP: The MAC address of 128.143.137.1 is 00:20:af:03:98:28 ARP: What is the MAC address of 128.143.71.21? frame

5. 5 What’s a protocol? human protocols: “what’s the time?” “I have a question” introductions … specific msgs sent … specific actions taken when msgs received, or other events network protocols: machines rather than humans all communication activity in Internet governed by protocols protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt

6. 6 What’s a protocol? a human protocol and a computer network protocol: Q: Other human protocols? Hi Got the time? 2:00 TCP connection req TCP connection response Get http://www.awl.com/kurose-ross time

7. 7 Communications Architecture The complexity of the communication task is reduced by using multiple protocol layers: Each protocol is implemented independently Each protocol is responsible for a specific subtask Protocols are grouped in a hierarchy A structured set of protocols is called a communications architecture or protocol suite

8. 8 TCP/IP Protocol Suite The TCP/IP protocol suite is the protocol architecture of the Internet The TCP/IP suite has four layers: Application, Transport, Network, and Data Link Layer End systems (hosts) implement all four layers. Gateways (Routers) only have the bottom two layers.

9. 9 Functions of the Layers Data Link Layer: –Service: Reliable transfer of frames over a link Media Access Control on a LAN –Functions: Framing, media access control, error checking Network Layer: –Service: Move packets from source host to destination host –Functions: Routing, addressing Transport Layer: –Service: Delivery of data between hosts –Functions: Connection establishment/termination, error control, flow control Application Layer: –Service: Application specific (delivery of email, retrieval of HTML documents, reliable transfer of file) –Functions: Application specific

10. 10 TCP/IP Suite and OSI Reference Model The TCP/IP protocol stack does not define the lower layers of a complete protocol stack

11. 11 Assignment of Protocols to Layers

12. 12 Layered Communications An entity of a particular layer can only communicate with: 1. a peer layer entity using a common protocol (Peer Protocol) 2. adjacent layers to provide services and to receive services

13. 13 Service Primitives N+1 Layer Entity N Layer Entity N+1 Layer Peer Protocol Request Delivery Indicate Delivery Communication services are invoked via function calls. The functions are called service primitives

14. 14 Service Primitives Recall: A layer N+1 entity sees the lower layers only as a service provider Service Provider N+1 Layer Entity N+1 Layer Peer Protocol Request Delivery Indicate Delivery

15. 15 Layers in the Example

16. 16 Layers in the Example Send HTTP Request to neon Establish a connection to 128.143.71.21 at port 80 Open TCP connection to 128.143.71.21 port 80 Send a datagram (which contains a connection request) to 128.143.71.21 Send IP datagram to 128.143.71.21 Send the datagram to 128.143.137.1 Send Ethernet frame to 00:e0:f9:23:a8:20 Send Ethernet frame to 00:20:af:03:98:28 Send IP data-gram to 128.143.71.21 Send the datagram to 128.143.7.21 Frame is an IP datagram IP datagram is a TCP segment for port 80

17. 17 Layers and Services Service provided by TCP to HTTP: –reliable transmission of byte streams over a logical connection Service provided by IP to TCP: –unreliable transmission of IP datagrams across an IP network Service provided by Ethernet to IP: –transmission of a frame across an Ethernet segment Other services: –DNS: translation between domain names and IP addresses –ARP: Translation between IP addresses and MAC addresses

18. 18 Encapsulation and Demultiplexing As data is moving down the protocol stack, each protocol is adding layer-specific control information

19. 19 Encapsulation and Demultiplexing in our Example Let us look in detail at the Ethernet frame between Argon and the Router, which contains the TCP connection request to Neon. This is the frame in hexadecimal notation. 00e0 f923 a820 00a0 2471 e444 0800 4500 002c 9d08 4000 8006 8bff 808f 8990 808f 4715 065b 0050 0009 465b 0000 0000 6002 2000 598e 0000 0204 05b4

20. 20 Encapsulation and Demultiplexing

21. 21 Encapsulation and Demultiplexing: Ethernet Header

22. 22 Encapsulation and Demultiplexing: IP Header

23. 23 Encapsulation and Demultiplexing: IP Header

24. 24 Encapsulation and Demultiplexing: TCP Header Option: maximum segment size

25. 25 Encapsulation and Demultiplexing: TCP Header

26. 26 Encapsulation and Demultiplexing: Application data

27. 27 Different Views of Networking Different Layers of the protocol stack have a different view of the network. This is HTTP’s and TCP’s view of the network.

28. 28 Network View of IP Protocol

29. 29 Network View of Ethernet Ethernet’s view of the network

30. 30 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.

31. 31 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 i t s 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.

32. 32 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

33. 33 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

34. 34 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

35. 35 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

36. 36 Growth of the Internet Source: Internet Software Consortium

37. 37 Internet Infrastructure

38. 38 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)

39. 39 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.

40. 40 Tier-1 ISP: e.g., Sprint Sprint US backbone network

41. 41 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.

42. 42 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)

43. 43 Assigning Identifiers for the Internet Who gives University the domain name “tcpip-lab.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.

44. 44 Summary Layered Internet architecture –Reduce complexity –Higher layer views lower layer as service provider –Application layer, transport layer, network layer, and link layer