Chapter 8 : TCP/IP

1. Chapter 8 : TCP/IP Business Data Communications, 7e

2. Objectives • Definition of Protocol architecture • Need for Communication architecture • Simplified 3 layer protocol • TCP/IP protocol • OSI • Motivation for the development of standards • Protocol architecture standard vs proprietary architecture • Need for Internetworking • Operation of a router within the context of TCP/IP to provide connectivity.

3. Introduction • Examines the underlying Communication Software required to support Distributed applications. • Use of a modular structure known as a protocol architecture to make the implementation of the communication software manageable. • Initially a simple protocol architecture consisting of 3 modules or layers is reviewed then TCP/IP (Transmission Control Protocol/Internet Protocol) followed by OSI (Open Systems Interconnections) will be discussed.

4. Standard architectures • TransmissionControlProtocol/InternetProtocol is an Internet-based standard and is the framework for developing a complete range of computer communications standards. • OpenSystemsInterconnection is another standard architecture used to describe communication functions (rarely used now). • SystemNetworkArchitecture is the proprietary used by IBM

5. Concepts of: Computer “Communications” & “Network” • Computer Communications: Referred to the exchange of information between computers • Computer Network: Set of 2 or more computers interconnected via a communication network.

6. Important Concepts in Computer “Communication” & “Networks” • Protocols • Protocol architecture (or computer communications architecture)

7. What is a Protocol? • Two entities can communicate successfully if they “speak the same language”. • What is communicated? How it is communicated? When it is communicated? • Must conform to mutually agreed conventions between the entities involved. • The Conventions are referred to as a protocol, which may be defined as: • “a set of rules governing the exchange of data between two entities”.

8. What is a Protocol? • Allows entities(i.e. application programs, FT Packages, DB Management Systems, e-mail facilities, terminals) from different systems (e.g. Computers, terminals, remote sensors) to communicate. • Definition: Shared conventions for communicating information are called protocols • Key elements of a Protocol are: • Syntax: includes data format & signal levels • Semantics: includes control information for coordination & handling • Timing: includes speed matching & sequencing

9. Why Use Protocol Architecture? • Data communications requires complex procedures: • Sender identifies data path/receiver • Systems negotiate preparedness • Applications negotiate preparedness • Translation of file formats • For all tasks to occur, high level of cooperation is required

10. The Need for a Protocol Architecture

11. Modular Approach • Breaks complex tasks into subtasks • Each module handles specific subset of tasks • Communication occurs: • between different modules on the same system • between similar modules on different systems

12. Advantages of Modularity • Easier application development • Network can change without all programs being modified

13. Protocols in a Simplified ArchitectureThree-Layer Model A Simplified Architecture for File Transfer

14. Three-Layer Model • Distributed data communications involves three primary components • Networks • Computers • Applications (e.g. File transfer or email) Computers are connected to the networks and the data to be exchanged are transferred by the network from one computer to another. Thus, the transfer of data from one application to another application in a different computer involves first getting data to the computer in which the application resides and then getting it to the intended application within the computer. • Three corresponding layers • Network access layer • Transport layer • Application layer

15. 1. Network Access Layer • Concerned with exchange of data between computer and network to which it is attached • Includes addressing, routing, prioritizing, etc • Different network types (e.g. Circuit Switching, packet Switching, LANs, etc.) require different software at this layer • The specific software used at this layer depends on the type of network to be used • Different standards have been developed for circuit switching, packet switching and LANs • Examples: • X.25 standard for network access procedures on packet-switching networks • IEEE 802 is a standard that specifies the access to a LAN

16. 2. Transport Layer • Concerned with reliable transfer of information between applications • Mechanisms for providing reliability are essentially independent of the nature of the applications • Includes aspects like flow control and error checking • Assurance that all of the data arrive at the destination application and that the data arrive in the same order in which they were sent • The transport layer is a common layer shared by all applications where these mechanisms can be collected

17. 3. Application Layer • Contains the Logic needed to support various applications • Each type of application (e.g. file transfer, remote access) requires different software on this layer which is suitable for that application.

18. Addressing • Each computer on a network requires a unique address on that network • Each application requires a unique address within the computer to allow support for multiple applications (service access points, or SAP)

19. Protocols Architectures and Networks Application Address, Unique in each Computer Destination Computer Address

20. Protocols in Simplified Architecture Example: An Application associated with Port 1 in Computer A wants to send a message to an Application associated with Port 2 in Compute B.

21. Protocols in a Simplified Architecture

22. Data Transmission(Fig5.5) • Application layer creates data block • Transport layer may break application layer data block into smaller pieces for convenience. • Transport appends a header to create PDU (Protocol Data Unit) referred to as transport PDU (also called Transport segments). • (Data block + Header) = Transport PDU = Segment • Items stored in the Header contains protocol control information which includes: • Destination SAP(Service Access Point)or port • Sequence Number • Error-Detection Code(also known as checksum or frame check sequence). • Network Access Layer appends another header to create Network Access PDU (also called a packet or Frame). • (Segment + Header) = Network Access PDU = Packet = Frame • Items stored in this header include: • Destination computer address • Facilities requests (e.g. “priority”)

23. Transport PDU or segment Transport PDU or segment Network PDU or Packet Network PDU or Packet PDU (Protocol Data Units)

24. PDU := Protocol Data Unit DSAP :=Destination Service Access Point DHost :=Destination Host Operation of a Protocol Structure

25. Standardized Protocol Architectures • (Problem) Why Standardize Protocol Architecture for Communication among different computers: • Special purpose communications software too costly • In Communication between computers from different vendors, software development might be a problem • Different vendors use different data formats and data exchange protocols • Within one vendor’s product line, different model computers may communicate in unique way. • Customers need to use equipment from different vendors without being concern of incompatibility.

26. Standardized Protocol Architectures (cont.) • Solution: • Computer vendors can adapt and implement a set of conventions • Therefore STANDARDS are needed

27. Standardized Protocol Architectures (cont.) • Benefits of Standards • For Vendors. Otherwise their products would be less marketable. • Customers could require from vendors to implement standards which provides them with more options in selecting equipment • Vendors like standards because they make their products more marketable • Customers like standards because they enable products from different vendors to interoperate • Two protocol standards are well-known: • TCP/IP: widely implemented • OSI: well-known, less used, still useful for modeling/conceptualizing, never lived up to its promises • SNA (System Network Architecture) as proprietary scheme from IBM

28. Standardized Protocol Architectures

29. Transmission Control Protocol/Internet Protocol is the result of experimental work on ARPANET Funded by DARPA (DefenseAdvancedResearchProjectAgency) Unlike OSI, No official protocol model Can be organized in five layers Five Layers: Application Host-to-Host (transport) Internet Network Access Physical TCP/IP TCP/IP consists of a large number of protocols that have been issued as Internet standards by the Internet Activities Board (IAB).

30. TCP/IP Physical Layer • Physical interface between a Data Transmission Equipment or Device (e.g. computer or terminal) and a transmission medium • This Layer Specifies: • Characteristics of the transmission medium • Nature of signals • Data rate, etc.

31. TCP/IP Network Access Layer • Exchange of data between the sending computer (end system) and network: • Address of host and destination • Invoke special services like Prioritization of transmission • Specific Software at this layer depends on the type of network in use e.g. circuit switching, packet switching, LAN, e.g.: • X.25 or frame relay for packet-switching • Ethernet for LAN • Segregation means that no other software needs to be concerned about net specifics

32. TCP/IP Internet Layer • An Internet is an interconnection of two or more networks • Internet layer handles tasks similar to network access layer, but between networks rather than between nodes on a network • Uses Internet Protocol (IP) for addressing and routing across networks • Implemented in end systems (eg computers & workstations) as well as in routers

33. Note: Network Access vs Internet • The Network Access Layer is concerned with access to and routing data across a network for two end systems attached to the same network. In those cases where two devices are attached to different networks, procedures are needed to allow data to traverse multiple interconnected networks which is the function of Internet Layer.

34. Note: Router • A Router is a processor that connects two networks and its primary function is to relay data from one network to the other on its route from the source to the destination end system.

35. TCP/IP Transport (or Host-to host) Layer • Reliable exchange of data between applications • i.e. ALL the Data arrive at the destination and in the same ORDER they were sent • Transmission Control Protocol (TCP) is the most commonly used protocol for this functionality

36. TCP/IP Application Layer • Contains the Logic needed to support various types of applications • Separate module supports each type of application (e.g. file transfer)

37. Types of Transport Protocols • There are 2 popular types of Transport Protocol: • TCP (Transmission Control Protocol), Fig 5-6-a • UDP (User Datagram Protocol), Fig 5-6-b

38. TCP • Most applications based on TCP/IP protocol use TCP as transport layer protocol. • TCP provides a reliable connection (i.e. logical association) between two entities to regulate flow check errors

39. UDP (User Datagram Protocol)Fig6-b • Is another transport Level Protocol in use as part of TCP/IP suite • Does not maintain a connection. It only adds a port capability to IP. Therefore it does not guaranteedelivery, preservation of sequence, or protection against duplication • Enables a process to send messages to other processes with a minimum of protocol mechanism • Is used by some transaction-oriented applications. (e.g. by SNMP Simple Network Management Protocol, the standard network management protocol for TCP/IP networks)

40. TCP and UDP

41. TCP Header UDP Header

42. IP and IPv6 • IP provides for 32-bit source and destination addresses • IPv6 (1996 standard) provides for 128-bit addresses • Migration to IPv6 will be a very slow process

44. TCP/IPLayers

45. Operation of TCP/IP • Network Access Protocol (e.g. Ethernet Logic) is used to connect a computer to a network • This Protocol enables the host to send data across the network to another host. Or, in the case of a host on another network, to a Router. • IP is implemented in all end systems and routers and acts as a relay to move a block of data from one host, through one or more routers, to another host. • TCP is implemented only in the end systems and keeps track of the blocks of data to assure reliable delivery (all & in order)

46. Operation of TCP/IP (cont’d) • Every entity in the overall system must have a unique address; • Two level of addressing • Each host have a unique global internet address, which is used by IP for routing and delivery • Each application within a host must have a unique address within the host known as Port (SAP in UDP)

48. Protocol data units (PDUs) in the TCP/IP Architecture.

49. TCP/IP Applications SMTP, FTP & Telnet are the most common applications that have been standardized to operate on top of TCP: • SMTP (Simple Mail Transfer Protocol) • Basic e-mail facility, transferring messages among hosts • FTP (File Transfer Protocol) • Sends files from one system to another on user command. (sets up a control connection TCP and data transfer connection TCP) • Telnet • Remote login capability, allowing a user to emulate a terminal on the remote system

50. Protocols in the TCP/IP Protocol Suite