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Guide to TCP/IP, Third Edition

Guide to TCP/IP, Third Edition. Chapter 1: Introducing TCP/IP. Objectives. Understand TCP/IP’s origins and history Explain the process by which TCP/IP standards and other documents, called Requests for Comments (RFCs), are created, debated, and formalized (where appropriate)

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Guide to TCP/IP, Third Edition

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  1. Guide to TCP/IP, Third Edition Chapter 1: Introducing TCP/IP

  2. Objectives • Understand TCP/IP’s origins and history • Explain the process by which TCP/IP standards and other documents, called Requests for Comments (RFCs), are created, debated, and formalized (where appropriate) • Understand the Open Systems Interconnection network reference model, often used to characterize network protocols and services, and how it relates to TCP/IP’s own internal networking model Introducing TCP/IP

  3. Objectives • Define the terms involved and explain how TCP/IP protocols, sockets, and ports are identified • Understand data encapsulation and how it relates to the four layers of the TCP/IP protocol stack • Understand and apply the basic practices and principles that underlie network protocol analysis Introducing TCP/IP

  4. What is TCP/IP? • Large collection of networking protocols and services • Two key protocols • Transmission Control Protocol (TCP) • Reliable delivery of messages • Internet Protocol (IP) • Manages the routing of network transmissions Introducing TCP/IP

  5. The Origins and History of TCP/IP • 1969 • Advanced Research Projects Agency (ARPA) funded research for packet-switched networking • ARPANET • Network built as a result of this project • In a packet-switched network • Sender and receiver are identified by unique network addresses Introducing TCP/IP

  6. TCP/IP’s Design Goals • To withstand a potential nuclear strike • To permit different computer systems to communicate easily • To interconnect systems across long distances Introducing TCP/IP

  7. A TCP/IP Chronology • 1978 • Internet Protocol version 4 (IPv4) • 1983 • Defense Communications Agency took over operation of ARPANET • 1986 • NSF launches high-speed network (NSFNET) • 1987 • Number of hosts on the Internet breaks 10,000 Introducing TCP/IP

  8. A TCP/IP Chronology (continued) • 1989 • Number of hosts on the Internet breaks 100,000 • 1990 • Worldwide Web is born at Centre European Researche Nucleaire (CERN) • 1991 • Commercial Internet Exchange (CIX) is formed • 1992 • Internet Society (ISOC) is chartered Introducing TCP/IP

  9. A TCP/IP Chronology (continued) • 1993 • InterNIC is chartered • 1994 • Online junk mail begins to proliferate • 1995 • Netscape launches Netscape Navigator • 1996 • Microsoft launches Internet Explorer Web browser • 1997 • 31 million registered domain names Introducing TCP/IP

  10. A TCP/IP Chronology (continued) • 2000 • Love Letter worm infects over one million PCs • 2001 • Number of hosts on the Internet breaks 150 million • Sircam virus and Code Red worm infect thousands • 2002 • 204 million Internet hosts • 2003 • Public Interest Registry becomes .org registry operator Introducing TCP/IP

  11. Who “Owns” TCP/IP? • TCP/IP • Falls squarely into the public domain • Funded with public monies since its inception • Owned by everybody and nobody Introducing TCP/IP

  12. Meet the Standards Groups that Manage TCP/IP • Internet Society (ISOC) • Internet Architecture Board (IAB) • Internet Engineering Task Force (IETF) • Internet Research Task Force (IRTF) • Internet Societal Discussion Forum (ISDF) • Internet Corporation for Assigned Names and Numbers (ICANN) Introducing TCP/IP

  13. TCP/IP Standards and RFCs • Request For Comments (RFCs) • Provide documentation to understand, implement and use TCP/IP protocols • Index for all RFCs available at • www.faqs.org/rfcs/ • RFC 2026 • Describes how a RFC is created Introducing TCP/IP

  14. OSI Reference Model Overview • OSI reference model • A network reference model • Formally known as ISO/OSI • Designed to replace TCP/IP • Standard way to explain how networks operate • TCP/IP is the open standard protocol suite of choice Introducing TCP/IP

  15. Models Break Networking into Layers • Divide and conquer approach • Separates networking hardware concerns from those related to networking software • Key points about networking • Easier to solve problems when broken into series of smaller problems • Layers operate independently of one another • Changes to one layer need not affect other layers Introducing TCP/IP

  16. Models Break Networking into Layers (continued) • Key points about networking • Individual layers work together on pairs of computers • Different expertise is needed at each layer • Network protocols usually map into one or more layers • TCP/IP is designed around a layered model Introducing TCP/IP

  17. Introducing TCP/IP

  18. How Protocol Layers Behave • Layers • Exist to encapsulate or isolate specific types of functionality • Provide services to the layer above • Deliver data to or accept data from the layer below • Protocol Data Units (PDUs) • Include “envelope information” in the form of specific headers and trailers Introducing TCP/IP

  19. Physical Layer • Includes the physical transmission medium • Job is to activate, maintain, and deactivate network connections • Manages communications with the network medium going down the protocol stack • Handles conversion of outgoing data Introducing TCP/IP

  20. Data Link Layer • Situated between the Physical layer and the Network layer in the reference model • Job is to • Enable reliable transmission of data through the Physical layer at the sending end • Check reliability at the receiving end • Manages point-to-point transmissionacross the networking medium Introducing TCP/IP

  21. Network Layer • Handles logical addresses associated with individual machines on a network • Uses addressinginformation to • Determine how to send a PDU • Embodies notion of multiple simultaneous connections between different IP addresses • Flexible enough to • Recognize and use multiple routes between a sender and a receiver Introducing TCP/IP

  22. Transport Layer • Ensures reliable end-to-end transmission of PDUs • Includes end-to-end error-detection and error-recovery • Segmentation • Involves cutting up a big message into a numbered sequence of chunks, called segments • PDUs used at the Transport layer are called segments, or data segments Introducing TCP/IP

  23. Session Layer • Defines mechanisms to • Permit senders and receivers to request that a conversation start or stop • Keep a conversation going even when traffic may not otherwise flow between the parties involved • Checkpoints • Define the last point up to which successful communications are known to have occurred Introducing TCP/IP

  24. Presentation Layer • Handles transforming data from • Generic, network-oriented forms of expression to more specific, platform-oriented forms of expression • A redirector or network shell • Special computer facility that resides here • Can supply special data-handling functions for applications Introducing TCP/IP

  25. Application Layer • Defines an interface that applications can use to request network services • Defines a set of access controls over the network • PDUs • Generically called Application PDUs Introducing TCP/IP

  26. The TCP/IP Networking Model • Design model that describes TCP/IP differs somewhat from OSI reference model • Transport layers for both models map together quite well as does the • Network layer from the OSI reference model and the Internet layer from the TCP/IP model Introducing TCP/IP

  27. Introducing TCP/IP

  28. TCP/IP Network Access Layer • Includes Ethernet, token ring, and wireless media devices • Includes WAN and connection-management protocols • The IEEE standards for networking apply • Including the IEEE 802 family of standards Introducing TCP/IP

  29. TCP/IP Network Access Layer Protocols • PPP • Most important TCP/IP Network Access layer protocol • PPPoE (“PPP over Ethernet” ) • Widely used on Ethernet networks or those with Ethernet-like characteristics • SLIP • Older, simpler serial line protocol that only supports TCP/IP-based communications Introducing TCP/IP

  30. TCP/IP Internet Layer Functions • Handle routing between machines across multiple networks • Three primary tasks • MTU fragmentation • Addressing • Routing Introducing TCP/IP

  31. TCP/IP Internet Layer Protocols • Internet Protocol (IP) • Internet Control Message Protocol (ICMP) • Packet Internetwork Groper (PING) • Address Resolution Protocol (ARP) • Reverse ARP (RARP) • Bootstrap Protocol (BOOTP) • Routing Information Protocol (RIP) Introducing TCP/IP

  32. TCP/IP Transport Layer Functions • Functions • Reliable delivery of data from sender to receiver • Fragmentation of outgoing messages and their reassembly prior to delivery to the Application layer • Hosts • Devices that operate on the Internet Introducing TCP/IP

  33. TCP/IP Transport Layer Protocols • Two TCP/IP Transport layer protocols • The transmission Control Protocol (TCP) • Connection-oriented • The User Datagram Protocol (UDP) • Connectionless • UDP • Transmits data in a “best-effort delivery” • Does no follow-up checking on its receipt Introducing TCP/IP

  34. TCP/IP Application Layer • Also known as the Process layer • TCP/IP services depend on: • Special “listener process,” called a daemon • Operates on a server to handle incoming user requests for specific services • Each TCP/IP service has an associated port address Introducing TCP/IP

  35. TCP/IP Protocols, Services, Sockets, And Ports • Multiplexing • Combining various sources of outgoing data into a single output data stream • Demultiplexing • Breaking up an incoming data stream so separate portions may be delivered to the correct applications • Well-known protocols • Assign a series of numbers to represent a sizable collection of TCP/IP-based network services Introducing TCP/IP

  36. Introducing TCP/IP

  37. TCP/IP Port Numbers • TCP/IP application processes • Sometimes called network services • Identified by port numbers • Source port number • Identifies the process that sent the data • Destination port number • Identifies the process to receive that data Introducing TCP/IP

  38. TCP/IP Sockets • Well-known or registered ports • Represent pre-assigned port numbers • Socket address (or socket) • The combination of a particular IP address and a dynamically assigned port address Introducing TCP/IP

  39. Data Encapsulation In TCP/IP • At each layer in the TCP/IP protocol stack • Outgoing data is packaged and identified for delivery to the layer underneath • Header • PDU’s own particular opening component • Identifies the protocol in use, the sender and intended recipient • Trailer (or packet trailer) • Provides data integrity checks for the payload Introducing TCP/IP

  40. About Protocol Analysis • Protocol analysis is the process of • Tapping into the network communications system • Capturing packets • Gathering network statistics • Decoding packets • Popular Windows-based protocol analyzers • Ethereal for Windows (Gerald Combs) • Sniffer Network Analyzer (Network Associates) Introducing TCP/IP

  41. Useful Roles for Protocol Analysis • Used to troubleshoot network communications • Used to test networks • Passive • Active • Gather trends on network performance • Analyzers available for variety of platforms Introducing TCP/IP

  42. Protocol Analyzer Elements • Promiscuous mode card and driver • Packet filters • Trace buffer • Decodes • Alarms • Statistics Introducing TCP/IP

  43. Introducing TCP/IP

  44. Introducing TCP/IP

  45. Introducing TCP/IP

  46. Placing a Protocol Analyzer on a Network • Protocol analyzer • Captures packets that it can see on the network • On network connected with hubs • You can place analyzer anywhere on the network • Options for analyzing switched networks • Hubbing out • Port redirection • Remote Monitoring (RMON) Introducing TCP/IP

  47. Introducing TCP/IP

  48. Summary • TCP/IP design goals • To support multiple, packet-switched pathways through the network • To permit dissimilar computer systems to easily exchange data • To offer robust, reliable delivery services for both short- and long-haul communications • To provide comprehensive network access with global scope Introducing TCP/IP

  49. Summary (continued) • Initial implementations of TCP/IP • Funded by Advanced Research Projects Agency • TCP/IP remains in the public domain • As Standard RFCs go through approval process they begin as Proposed Standard documents • Best Current Practice (BCP) • An informational (non-standard) RFC Introducing TCP/IP

  50. Summary (continued) • ISO/OSI network reference model • Breaks networking into seven distinct layers • TCP/IP uses a variety of encapsulation techniques at its various layers to • Label the type of data contained in the contents, or payloads, of its PDUs • Protocol analysis • Network interface inspects all traffic moving across a segment of network medium Introducing TCP/IP

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