Bridge

Bridge – connecting devices between separate local area networks. Client/Server Systems – A computing system composed of two logical parts: a server, which provides information or services, and a client, which requests them. Codec – A codec is a device or computer program capable of encoding and/or decoding a digital data stream or signal. Computer Network – an interconnection of computers over a small or large geographic areas. Data Communications – is a process that involves data transfer from one computer to another through a communication medium such as telephone, a microwave relay, a satellite link as a physical cable. Data link layer – responsible for taking the raw data and transforming it into a cohesive unit called frame. Data Network – are networks designed to transmit computer data. Domain Name System - is the way that Internet domain names are located and translated into Internet Protocol addresses. Encapsulation - The transmission of one network protocol within another. File Transfer Protocol - is a standard network protocol used to transfer files from one host to another over a TCPbased network, such as the Internet. Frame – a data-link layer protocol data unit that contains frame serial number and frame information. Hub – collection points for the wires that interconnect the workstations. Hypertext Transfer Protocol – is a networking protocol for distributed, collaborative, hypermedia information systems. Interface layer – defines both physical medium that transmits the signal and the frame that incorporates flow and error control.

Internet application layer – provides services for an application program to ensure that effective communication with another application program in a network is possible. Internet model – The protocol architecture for TCP/IP currently is defined by the IETF, which is responsible for establishing the protocols and architecture for the Internet. Internet Protocol - is the principal communications protocol used for relaying datagrams(packets) across an internetwork using the Internet Protocol Suite. Internet Transport Layer - provides endto-end communication services for applications within a layered architecture of network components and protocols. Local Area Network – are networks within a small radius, such as room or building. Logical connection – is a flow of ideas; without a direct physical connection between sender and receiver at a particular layer. Metropolitan Area Network – are networks that service a metropolitan area. Modem – is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. Multiplexing - is a method by which multiple analog message signals or digital data streams are combined into one signal over a shared medium. Logical connection – is a flow of ideas; without a direct physical connection between sender and receiver at a particular layer. Metropolitan Area Network – are networks that service a metropolitan area. Modem – is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information.

Multiplexing - is a method by which multiple analog message signals or digital data streams are combined into one signal over a shared medium. Logical connection – is a flow of ideas; without a direct physical connection between sender and receiver at a particular layer. Metropolitan Area Network – are networks that service a metropolitan area. Modem – is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. Multiplexing - is a method by which multiple analog message signals or digital data streams are combined into one signal over a shared medium. Logical connection – is a flow of ideas; without a direct physical connection between sender and receiver at a particular layer. Metropolitan Area Network – are networks that service a metropolitan area. Modem – is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. Multiplexing - is a method by which multiple analog message signals or digital data streams are combined into one signal over a shared medium. Logical connection – is a flow of ideas; without a direct physical connection between sender and receiver at a particular layer. Metropolitan Area Network – are networks that service a metropolitan area. Modem – is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. Multiplexing - is a method by which multiple analog message signals or digital

data streams are combined into one signal over a shared medium. Logical connection – is a flow of ideas; without a direct physical connection between sender and receiver at a particular layer. Metropolitan Area Network – are networks that service a metropolitan area. Modem – is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. Multiplexing - is a method by which multiple analog message signals or digital data streams are combined into one signal over a shared medium. Logical connection – is a flow of ideas; without a direct physical connection between sender and receiver at a particular layer. Metropolitan Area Network – are networks that service a metropolitan area. Modem – is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. Multiplexing - is a method by which multiple analog message signals or digital data streams are combined into one signal over a shared medium. Network Architecture Model - is the design of a communications network and a framework for the specification of a network's physical components and their functional organization and configuration, its operational principles and procedures, as well as data formats used in its operation. Network layer – is a responsive for creating , maintaining, and ending network connections. Network Management - refers to the activities, methods, procedures, and tools that pertain to the operation, administration,

maintenance, and provisioning of networked systems. Node – are the computing devices that allow workstations to connect to the network and that makes the decisions as to which route a piece of data will follow next. Open Systems Interconnection - is a standard description or "reference model" for how messages should be transmitted between any two points in a telecommunication network. Physical layer – handles the transmission of bits over a communications channel. Presentation layer – performs a series of miscellaneous functions necessary for presenting the data package properly to the sender or receiver. Router – are the connecting devices between local area network and wide area network. Server – are the computers that store the network software and shared or private user files. Session layer – is responsible for establishing sessions between users. Simple Mail Transport Protocol - is an Internet standard for electronic mail (email) transmission across Internet Protocol (IP) networks. Simple Network Management Protocol - is an "Internet-standard protocol for managing devices on IP networks. Subnet – the collection of nodes and telephone lines into a cohesive unit. Synchronization point - is the application of particular mechanisms to ensure that two concurrently-executing threads or processes do not execute specific portions of a program at the same time. Telecommunications – study of telephones and the systems that transmit telephone signals. Telnet - is a network protocol used on the Internet or local area networks to provide a bidirectional interactive textoriented communications facility using a virtual terminal connection.

Token Management - is a complete framework for managing all aspects of token assignment, deployment and personalization within an organization. Transport layer – is concerned with an error-free, end-to-end flow of data. Wide Area Network – are networks that cover areas such as states and countries. Wireless – are networks use radio waves for communications or is the transfer information between two or more points that are physically not connected. The Language of Computer Networks Computer network – an interconnection of computers and computing equipment using either wires or radio waves over small or large geographic areas Local area network – networks that are small in geographic size spanning a room, floor, building, or campus • Metropolitan area network – networks that serve an area of 1 to 30 miles, approximately the size of a typical city • Wide area network – a large network that encompasses parts of states, multiple states, countries, and the world • Personal area network – a network of a few meters, between wireless devices such as PDAs, laptops, and similar devices • Voice network – a network that transmits telephone signals • Data network – a network that transmits computer data • Data communications – the transfer of digital or analog data using digital or analog signals • Telecommunications – the study of telephones and the systems that transmit telephone signals • Network management – the design, installation, and support of a network, including its hardware and software The Big Picture

Networks are composed of many devices, including: • Workstations (computers, telephones) • Servers • Network hubs and switches (bridges) • Routers (LAN to WAN and WAN to WAN) • Telephone switching gear •

Computer Networks – Basic Connections • Computer terminal / microcomputer to mainframe • Microcomputer to local area network • Microcomputer to Internet • Local area network to local area network • Personal area network to workstation • Local area network to metropolitan area network

Local area network to wide area network • Sensor to local area network • Satellite and microwave • Wireless telephone and wired telephone to network Basic Connections – Computer Terminal / Microcomputer to Mainframe Computer • Predominant form in the 1960s and 1970s • Still used in many types of businesses for data entry and data retrieval • Usually involves a low-speed connection •

Basic Connections – Microcomputer to Local Area Network •

Highly common throughout business and academic environments, and now homes

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Typically a medium- to high-speed connection Computer (device) requires a NIC (network interface card) NIC connects to a hub-like device

Basic Connections – Microcomputer to Internet • •

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Popular with home users and small businesses Often a dial-up modem is used to connect user’s microcomputer to an Internet service provider Technologies such as DSL and cable modems are replacing modems

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Basic Connections – Loal Area Network to Local Area Network •

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Found in systems that have two or more LANs and a need for them to intercommunicate A bridge-like device (such as a switch) is typically used to interconnect LANs Switch can filter frames

Basic Connections – Local Area Network to Metropolitan Area Network Basic Connections – Personal Area Network to Workstation •

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Interconnects wireless devices such as PDAs, laptops and notebooks, and music playback devices Used over short distances such as a few meters

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Used to interconnect companies (usually their local area networks) to networks that encompass a city High-speed networks with redundant circuits Metro Ethernet is latest form of metropolitan LAN

Basic Connections – Local Area Network to Wide Area Network •

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One of the most common ways to interconnect a user on a LAN workstation to the Internet (a wide area network) A router is the typical device that performs LAN to WAN connections Routers are more complex devices than switches

Basic Connections – Wide Area Network to Wide Area Network High-speed routers and switches are used to connect one wide area network to another • Thousands of wide area networks across North America, many interconnected via these routers and switches Basic Connections – Sensor to Local Area Network •

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-Not all local area networks deal with microcomputer workstations -Often found in industrial and laboratory environments -Assembly lines and robotic controls depend heavily on sensorbased local area networks

Basic Connections – Satellite and Microwave • •

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-Typically long distance wireless connections -Many types of applications including long distance telephone, television, radio, long-haul data transfers, and wireless data services -Typically expensive services but many companies offer competitive services and rates -Newer shorter-distance services such as Wi-Max

Basic Connections – Wireless or Cellular Telephones • •

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-Constantly expanding market across the U.S. and world -Third generation services available in many areas and under many types of plans -Newest generation includes higher speed data transfers (100s of kilobits per second)

An Additional Basic Connection – Telephone to Network -Telephone systems are ubiquitous and now carry more data than voice -Common configuration – telephone connected to POTS -Newer configuration (VoIP) – telephone to LAN via gateway or telephone to gateway via DSL/cable Network Architectures -A reference model that describes the layers of hardware and software necessary to transmit data between two points or for multiple devices / applications to interoperate -Reference models are necessary to increase likelihood that different components from different manufacturers will converse -Two models to learn: OSI model and TCP/IP protocol suite •

The OSI model’s seven layers:

Network Architectures - OSI -Application layer – where the application using the network resides. Common network applications include web browsing, e-mail, file transfers, and remote logins -Presentation layer – performs a series of miscellaneous functions necessary for presenting the data package properly to the sender or receiver Session layer – responsible for establishing sessions between users Transport layer – provides an end-toend error-free network connection. Makes sure the data arrives at the destination exactly as it left the source. Network layer – responsible for creating, maintaining and ending network connections. Transfers a data packet from node to node within the network.

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Transport layer – equivalent to OSI’s transport layer Network (Internet or internetwork) layer – equivalent to OSI’s network layer Network access (data link/physical) layer – equivalent to OSI’s data link and physical layers Logical and physical connections – A logical connection is one that exists only in the software, while a physical connection is one that exists in the hardware Note that in a network architecture, only the lowest layer contains the physical connection, while are higher layers contain logical connections Logical and physical connections

Network Architectures The TCP/IP protocol suite (DoD protocol suite, Internet model):

Network Architectures – TCP/IP •

Application layer – equivalent to OSI’s application and presentation layers

Example of data flow through layers

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Network connections in action

The TCP/IP protocol suite in action • •

Note the flow of data from user to web browser and back At each layer, information is either added or removed, depending on whether the data is leaving or arriving at a workstation

The adding of information over preexisting information is termed encapsulation