Module 2 notes: Network needs 3 things, sender receiver and medium. Messages broken down into smaller pieces so large transmitions don't monopolize the network. this is called segmentation, message broken into smaller pieces. 2 advantages, multiple conversations and multiple paths for redundancies. segmentation imposes overhead on network communications. Services are programs that respond to network requests. processes are method of getting things to happen on network. End devices: • Computers (work stations, laptops, file servers, web servers) • Network printers • VoIP phones • Security cameras • Mobile handheld devices (such as wireless barcode scanners, PDAs) end devices are called hosts. Hosts are identified by an address. Servers are hosts that have software installed that enables them to provide information and services, like e-mail or web pages, to other hosts on the network. Clients are hosts that have software installed that enables them to request and display the information obtained from the server. Intermediate devices: • Network Access Devices (Hubs, switches, and wireless access points) • Internetworking Devices (routers) • Communication Servers and Modems • Security Devices (firewalls) These devices: • Regenerate and retransmit data signals • Maintain information about what pathways exist through the network and internetwork • Notify other devices of errors and communication failures • Direct data along alternate pathways when there is a link failure • Classify and direct messages according to QoS priorities • Permit or deny the flow of data, based on security settings 3 types of media: copper cables, fibre and wireless. When you choose media you consider: • The distance the media can successfully carry a signal. • The environment in which the media is to be installed. • The amount of data and the speed at which it must be transmitted. • The cost of the media and installation Lans are usually administered by single organization and cover small geographic area. Wans are when you have multiple locations separated by distance often connected by tsps. Internet is global network of networks. *** ISP networks connect to provide access to millions of users. Terms to know: NIC: connects end device to network, media connects to NIC. Physical port: this is where the cable plugs in. interface: a specialized port that connects a device to the network. Interfaces can be physical or virtual. Note that network diagrams have specialized symbols to show devices. 2.2.4 lab is not accessible. 2.2.5: this is doable but neotrace is a bit tricky. 2.3: protocols: These govern rules for communication, give examples such as face to face. Protocols depend on what factors govern communication. A set of protocols that interoperate is called a protocol stack. protocol suites describe: • The format or structure of the message • The method by which networking devices share information about pathways with other networks • How and when error and system messages are passed between devices • The setup and termination of data transfer sessions Individual protocols in a protocol suite may be vendor-specific and proprietary. Proprietary, in this context, means that one company or vendor controls access to the protocol. A protocol can be technology independant if it specifies what needs to be done or not how it should be done. bennitifts to layered models: • Assists in protocol design, because protocols that operate at a specific layer have defined information that they act upon and a defined interface to the layers above and below. • Fosters competition because products from different vendors can work together. • Prevents technology or capability changes in one layer from affecting other layers above and below. • Provides a common language to describe networking functions and capabilities. difference between protocol model and reference model is that protocol model only shows stuff necessary to get a protocol to work. reference model is used to show how protocol works. TCP/IP standards set by rfcs in public forum. steps for protocols: 1. Creation of data at the Application layer of the originating source end device 2. Segmentation and encapsulation of data as it passes down the protocol stack in the source end device 3. Generation of the data onto the media at the Network Access layer of the stack 4. Transportation of the data through the internetwork, which consists of media and any intermediary devices 5. Reception of the data at the Network Access layer of the destination end device 6. Decapsulation and reassembly of the data as it passes up the stack in the destination device 7. Passing this data to the destination application at the Application layer of the destination end device. types of pdus: • Data - The general term for the PDU used at the Application layer • Segment - Transport Layer PDU • Packet - Internetwork Layer PDU • Frame - Network Access Layer PDU • Bits - A PDU used when physically transmitting data over the medium Cover how data starts at top of model and is sent down layers across media and back up to application layer on receiving host. Layers of OSI reference model do the following: Layer 7. Application - The Application Layer provides the means for end-to-end connectivity between individuals using data networks. Layer 6. Presentation - The Presentation Layer provides for common representation of the data transferred between Application Layer services. Layer 5. Session - The Session Layer provides services to the Presentation Layer to organize its dialogue and to manage data exchange. Layer 4. Transport - The Transport Layer defines services to segment, transfer, and reassemble the data for individual communications between the end devices. Layer 3. Network - The Network Layer provides services to exchange the individual pieces of data over the network between identified end devices. Layer 2. Data Link - The Data Link Layer protocols describe methods for exchanging data frames between devices over a common media. Layer 1. Physical - The Physical Layer protocols describe the mechanical, electrical, functional, and procedural means to activate, maintain, and de-activate physical connections for bit transmission to and from a network device. TCP/OSI comparison: O S I Layer 7. Application relates to TCP/IP Layer 4 Application. O S I Layer 6. Presentation relates to TCP/IP Layer 4 Application. O S I Layer 5. Session relates to TCP/IP Layer 4 Application. O S I Layer 4. Transport relates to TCP/IP Layer 3 Transport. O S I Layer 3. Network relates to TCP/IP Layer 2 Internet. O S I Layer 2. Data Link relates to TCP/IP Layer 1 Network Access. O S I Layer 1. Physical relates to TCP/IP Layer 1 Network Access. Discuss network addressing. different addresses for layers. Layer 2 addresses are only unique for a specific network, layer 3 addresses need to contain info on what network a machine is connected to. Port number specifies the application that is using a connection.