Network Classification and Standards Organizational Communications and Technologies Prithvi N. Rao Carnegie Mellon University Web:

Reading Data Communication Fundamentals (Stallings and van Slyke) Chapter 5 TCP/IP and Other Protocol Architectures (Stallings and van Slyke) Chapter 12

Objectives Describe the methods for classifying computer networks List the different size classification of networks List the two major types of transmission media List two types of switching service Define the layered approach to communication architectures

Objectives Describe the seven layers of the Open Systems Interconnection (OSI) model Compare TCP/IP and SNA architectures to the OSI model

Network Topologies and Components Computer networks classified in the following ways Size Ownership Type of transmission media Type of switching service Logical access method

Classification Size refers includes number of users and geographic location Local Area Network (LAN) spans less than 1 km Campus Area Network span 5 to 100 km and are privately owned Metropolitan Area Network (MAN) span 2 to 100 km and found within campuses or within and office complex

Classification Wide Area Network (WAN) spans more than 100 km WAN is the “long haul” network of choice and spans the nation or entire world

Ownership Determines who is ultimately responsible for the maintenance of the network components and the addition of new equipment Private Private businesses, universities or individuals Includes all cables, and intermediate equipment Includes most LAN and MAN Provide the greatest flexibility of service Restrict who can connect to them and distance of communication

Ownership Public owned by public utility companies Owned predominantly by the phone companies Some MAN and nearly all WAN networks are in this category Offer tremendous connectivity Provider determines connectivity and flexibility of service

Transmission Media Type of transmission media identifies network by physical media used to communicate between locations Bounded Cable, wire or fiber optic media in which signal is contained Various types of cables and are closely related to various network topologies

Transmission Media Type of transmission media identifies network by physical media used to communicate between locations Bounded Cable, wire or fiber optic media in which signal is contained Various types of cables and are closely related to various network topologies

Transmission Media Unbounded Microwave, satellite, radio wave or infrared media WAN service providers use “long-haul” unbounded media Typically there is a combination of media types used in providing services to users

Switching Service Circuit Switching Analogous to a telephone call Line is maintained throughout duration of conversation Transmission resources are dedicated and reserved for duration of connection Service is optimal for continuous or time sensitive information flow Bulk file transfer (not necessarily time sensitive) Voice Video

Switching Service Packet Switching Analogous to the postal service; package can take several possible routes to reach destination Network information is broken into packets Transmission resources are shared by many connections. More than one path to destination Each transmission unit must contain addressing information More efficient because they share resources Provide best to non-time sensitive data Logging sessions Transaction processing Query and response systems

Logical Access Method Connection Oriented logical access requires user to establish connection with the receiver before communication can take place Sender and receiver must both terminate connection Applies to most voice and wide area packet networks Public switched voice network X.25, T1 and T3 high speed communication channels ISDN frame relay and ATM (Asynchronous Transfer Mode) Transmission Control Protocol (TCP)

Logical Access Method Connectionless logical assumes communication channel is always available Senders and receivers transmit without establishing a communications channel PC-LAN provide connectionless access Broadcast LAN (ethernet) Broadcast satellite transmission Cable TV and FM radio User Datagram Protocol (UDP)

Protocol Defined Agreed upon set of rules defining how devices communicate Define which language is used and the grammar and syntax Define message format

Standard Protocol Defined Set of specifications defining a specific method or technology for use in a fixed set of applications Hardware Software Access methods Message handling formats

Standard Setting Bodies Institute of Electrical and Electronic Engineers (IEEE) American National Institute of Standards and Technology (NIST) International Standards Organization (ISO) Internet Activities Board (JAB) Consultative Committee for International Telegraphy and Telephony (CCITT)

Open Systems Products and technologies designed and implemented in accordance with vendor-independent standards Distributed multi-vendor environment open systems enable users to achieve portability among applications, data and people

Goals of the Open Systems Movement Portability Ability to move applications and data from one system to another without re-programming and data conversion Scalability Ability to grow applications from one computer platform to larger more platforms in the future Interoperability Ability for a network of heterogeneous computers to operate with the same data and applications independently of one another and to use those applications in the native machine interface

The OSI Model International Standards Organization (ISO) developed layered model for supporting communications architecture Modularity was motivation Each layer is independent of another layer Protocol of one layer does not rely on the protocol of any specific protocol of any other layer for information Function duplication should be avoided Resulting OSI model not widely implemented although the US Government is pushing for acceptance of this architecture

Layer Purpose Application Provides interface between end-user services , file transfer All lower layers support this layer Presentation Performs protocol conversion, data encryption and decryption Performs data compression Concerned mainly with representation of data rather than content Interfaces to application layer above it and to lower level services

Layer Purpose Session Establishes and terminates data streams between network nodes Manages and synchronizes direction of data flow NetBIOS is one of the first session layer protocols Transport (TCP, SPX, XNS) Provides an additional layer of connection below session layer Ensures that session connections are transparent and handles details of data transfer Assembles packets for routing by the network layer

Layer Purpose Network (IP and IPX) Provides routing mechanisms between nodes on a network Concerned with addressing and identification of nodes Datalink Defines the access method for connection with network Error detection and connection are important functions here Physical Determines the electrical mechanical aspects of network Responsible for bit stream transmission and error checking

OSI Summary Simplify model and use it as basis for discussion Application, Presentation and Session layers deal with how computers on each end handle information internally Network, Data Link and Physical layers handle data once it has entered the network Transport layer interfaces between upper and lower

OSI Summary Simplify model and use it as basis for discussion Application, Presentation and Session layers deal with how computers on each end handle information internally Network, Data Link and Physical layers handle data once it has entered the network Transport layer interfaces between upper and lower

OSI Model 7 Application Layer 6 Presentation Layer 5 Session Layer 4 Transport Layer 3 Network Layer 2 Data Link Layer 1 Physical Layer End User Interface Data Translation Time Management Messages Packets Frames Data Bits drivers hardware NOS NetBIOS

Comparison of OSI, TCP/IP and SNA Application Presentation Session Transport Network Data Link Physical OSITCP/IPIBM SNA Process or application FTP, Telnet, or SMTP TCP/UDP Internet Network Access Or Local Network End User Applications Presentation Services Data Flow Transmission Control Path Control Data Link Physical

Network Compatibility Network Operating System Hardware Network Application Driver Version & Specs System Board BIOS NIC Card Configuration NOS Version and Manufacturer

Summary Classification of networks based on Size Ownership Type of media Switching method Logical Access Method TCP and SNA are examples of layered approaches