CSC 600 Internetworking with TCP/IP Unit 1: Introduction (Ch. 1, 11) Dr. Cheer-Sun Yang Spring 2001

What is communication and networking ? Communication: Different machines, (which are also referred to as hosts, communication entities, or stations), running different operating systems transferring text, voice, image data between them. Networking: the communication entities being “connected” together indirectly via another communication entity or entities. This results in a communication network.

Motivation for Networking Different machines, (which are also referred to as hosts, communication entities, or stations), running different operating systems need to communicate. Computer users need to exchange data. Users need to access information stored remotely.

What is internetworking? The technology, called internetworking, accommodates multiple, diverse underlying hardware technologies by providing a way to interconnect heterogeneous networks and a set of communication conventions that makes them interoperate. Internetworking provides hardware and software techniques and protocols for interconnecting heterogeneous networks.

Communication Protocols Communication is achieved through the cooperation of hardware and software. Two parties engaged in communication must comply with a set of rules which governing the timing of exchanging messages, the message format, the meaning of each message content. Protocol – a set of rules which governs the exchange of information. For example, TCP is a protocol, IP is another.

Types of Computer Networking Systems Intranetworking—a communication system for connecting homogeneous networks together. Internetworking—a communication system for connecting heterogeneous networks together.

Internetworking—the communication of heterogeneous computers. Internet—a specific kind of network system. Internetworking vs. the Internet

The Internet  U.S Government agencies realized the importance and potential of internetworking technology many years ago, and have funded research that has made possible a global Internet.  An example of Open System Interconnection.

Open vs. Proprietary Open Systems – the specifications are publicly available; supported by almost all venders Proprietary Systems –only supported by specific venders. For example, IBM’s SNA, APPLE’s AppleTalk, Datapoint’s ARCNet.

Internet Services Application-Level Internet Services –World Wide Web –Electronic mail –File transfer –Remote login (telnet) –Voice on IP: Internet Telephony –Videoconferencing: using Internet to transmit text, image, and voice data. –Mobile IP: accessing Internet from within a car

Internet Services(cont’d) Network-Level Internet Services –Connectionless Packet Delivery Service –Reliable Stream Transport Service

Summary of Internet Services Each layer provides services to the layer above it. Each layer uses the services provided by the layer below it. This resulting protocol architecture is called a protocol stack.

Application Layer Services Virtual Terminal File Transfer Remote Login or Telnet World Wide Web

Transport-Level Services Connectionless Packet Delivery Services Reliable Connection-oriented Stream Transport Service Provided by TCP and UDP, respectively

Network-Level Services Connectionless Packet Delivery Services Fragmentation and Assemble Provided by Internetworking Protocol(IP) software

Media Access-Level Services Framing of data bit streams Error detection and recovery Could be implemented in the NIC. The driver implements some device accessing functions for IP software to use.

Why is so special about the Internet? Network technology independence: Although TCP/IP is based on conventional packet switching technology, it is independent of any particular vender’s hardware. In contrast, SNA only runs on IBM hardware. Universal Interconnection: IP address identifies a host from another.

Why is so special about Internet?(cont’d) End-to-end acknowledgements: The TCP/IP protocols only provide acknowledgements between the source and the destination instead of between successive machines along the path. In contrast, X.25 provides acknowledgements between any two nodes. Application Protocol Standards.

History of the Internet Late 60s—The government-funded Advanced Research Projects Agency(DARPA) created ARPANET in Mid 1970’s – ARPA began to work on connecting computers in all associated agencies. The early Internet had emerged.

History of the Internet(cont’d) Mid 1980’ – the Internet split into ARPANET and MILNET – NSFNET began to work; the National Science Foundation funded a new wide area network that connected all of its supercomputing centers.

Other Names of the Internet ARPANET : the U.S. Department of Defense Advanced Research Projects (ARPA) The TCP/IP Internet The (Global) Internet

Who run the Internet? No one person, group or organization owns. The backbone of it is funded by the National Science Foundation in the U.S. In addition, a reorg of the Internet Advisory Board (IAB) occurred in Now, there is an Internet Engineering Task Force (IETF) and Internet Research Task Force (IRTF) who help to set standards (TCP/IP) for those who wish to connect to, and use, the Internet. The IAB makes its standard available via documents called RFC (Request for Comment).

Standards Required to allow for interoperability between equipment Advantages –Ensures a large market for equipment and software –Allows products from different vendors to communicate Disadvantages –Freeze technology –May be multiple standards for the same thing

Standards Organizations ISO (International Organization for Standardization) Internet Architecture Board (IAB) ITU-T (formally CCITT) ATM forum

Internet Standards Organizations Internet Activities Board (IAB): 1983 Internet Research Task Force (IRTF) Internet Engineering Task Force (IETF) Internet Society: replaced IAB around 1992.

Request For Comments(RFCs) Documentation of work on the Internet, proposals for new or revised protocols, and TCP/IP protocol standards all appear in a series of technical reports called Internet Request For Comments(RFCs). Please check my Web Page for accessing RFCs. TCP: RFC 793 UDP: RFC 768 IP: 791, 760

The Internet Now In 1992, as the Internet moved away from the U.S. government roots, a society was formed to encourage participation in the Internet. A new organization called Internet Society (ISOC) becomes the host \for the IAB. Explosive growth – –Now, it spans 82 countries and has millions of nodes. –It has been growing exponentially since its inception. Used in all Venues-government, education, private companies (END OF CHAPTER 1)

Chapter 11 Protocol Layering Open Systems vs. closed systems SNA vs. TCP/IP

The Need of Multiple Protocols Open Systems vs. closed systems SNA vs. TCP/IP

What is TCP/IP? TCP/IP stands for Transmission Control Protocol/Internet Protocol and is actually a set of standards that describe how data is to be transferred between computers. TCP/IP is the common tongue that all computers must speak to communicate via Internet. There are implementations for UNIX, Windows, Macintosh, and just about any computer operating systems you can think of. TCP/IP is implemented as part of an Operating System.

Connecting Two PCs Applications run on top of OS with communication software implemented in it. Operating system communicates with network driver that is another software. Network driver talks to communication hardware including Network Interface Card (NIC) and modem.

Connecting Two PCs(cont’d) Both parties must agree on the format of the data unit being exchanged. Both parties must agree on how to initiate the connection and when the send and receive operations can be conducted. When to disconnect and how.

Keys Both parties must use the same data format. Both parties must see eye to eye on the meaning of the content. Both must agree on the timing for exchanging information. The three factors constitute the core of a set of rules which is called a communication protocol.

Communication Protocol Definition – all parties involved involved in the communication must comply with a set of rules when exchanging messages. Thus, the set of rules which both the sender and the receiver all comply with is called protocol. A protocol specifies the message format, meanings, and the procedures

Key Elements of a Protocol Syntax –Data formats –Signal levels Semantics –Control information –Error handling Timing –Speed matching –Sequencing

Comm. software device driver TCP IP Network Driver Network interface card applications TCP IP Network Driver Network interface card applications

Communication Reference Models In summary, we need a communication reference model to describe the relationship between various software and hardware. There are two well-known reference models: TCP/IP and OSI. A reference model describes the layering relationship of software and hardware involved in the communication. Let’s take a look at TCP/IP model.

The Need for Layered Protocols Complex data communication systems do not use a single protocol to handle all transmission tasks. The require a set of cooperative protocols, sometimes called a protocol family or protocol suite..

TCP/IP Protocol Architecture Developed by the US Defense Advanced Research Project Agency (DARPA) for its packet switched network (ARPANET) Used by the global Internet No official model but a working one. –Application layer –Transport layer: host-to-host (application to application) –Internet layer: network routing and congestion control –Network access layer: access transmission medium –Physical layer

Physical Layer Physical interface between data transmission device (e.g. computer) and transmission medium or network Characteristics of transmission medium Signal levels Data rates etc.

Network Access Layer Exchange of data between end system and network Destination address provision Invoking services like priority

Internet Layer (IP) Systems may be attached to different networks Routing functions across multiple networks Implemented in end systems and routers

Transport Layer (TCP) Reliable delivery of data Ordering of delivery

Application Layer Support for user applications e.g. http, SMPT

TCP/IP Protocol Architecture Model

Protocol Data Unit (PDU) An OSI term for the smallest data unit each layer handles. TCP/IP terms are: –Data link layer: data frame –IP Layer: IP datagram –TCP: segment (p. 223) or TCP packet(p 184) –UDP: datagram Usually, datagram is used with connectionless service; packet is used with connection-oriented service.

Layering Principle Layered protocols are designed so that layer n at the destination receives exactly the same object sent by layer n at the source.

Layering in a Point-to- Point Network

Layering in a TCP/IP Internet Environment

Layering in the Presence of Network Substructure

Two Important Boundaries in the TCP/IP Model

OSI Model Open Systems Interconnection (OSI) Developed by the International Organization for Standardization (ISO) Seven layers A theoretical system delivered too late! TCP/IP is the de facto standard

OSI Layers Application Presentation Session Transport Network Data Link Physical

Physical Layer Corresponds to basic hardware. Example: NIC, modem, cable Topics include transmission media, error detection, correction.

Data Link Layer Specifies how to organize data into frames and how to transmit frames over a network. Detail topics include the format of a data frame, flow control.

Network Layer Specifies how to assign addresses and how to forward packets to its destination. Detail topics include the format of a data frame, flow control.

Transport Layer The basic function of the transport layer is to accept data from the session layer, split it up into smaller units, if needed, pass them to the network layer, and ensure that the pieces all arrive correctly at the other end. The transport layer also determines the type of services, connection-oriented or connectionless.

Session Layer Allows users on different machines to establish sessions between them. Major functions include managing dialog. Session layer determines whether traffic can only go in one direction or both directions at the same time.

Presentation Layer Controls the encoding and decoding of data.

Application Layer Controls the interface with users. Application, presentation, session layers are usually implemented together instead of using laying architecture.

Nested Protocol Headers

Disadvantage of Layering The software that results from strict layering can be extremely inefficient. The TCP layer will not understand the format of the IP datagram. The TCP layer will not know how the network will route the datagram. The packet size cannot be optimized.

WHAT IS THIS? Comm. software device driver TCP IP Network Driver Network interface card applications TCP IP Network Driver Network interface card applications

What’s Next? – TCP/IP Over What? Two issues— –Medium and connection –Hardware addressing But…..

When is he going to stop? Do I really need CSC600?

Reading Assignment Chapters 1, 2, 3, 11 (ignore 2.5, 2.6, 2.10, 2.11)