networking protocols and the osi model. osi model overview the open systems interconnection (osi)...
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![Page 1: Networking Protocols and the OSI Model. OSI Model Overview The Open Systems Interconnection (OSI) reference model is an industry standard framework that](https://reader035.vdocument.in/reader035/viewer/2022081501/56649d975503460f94a80d21/html5/thumbnails/1.jpg)
Networking Protocols and the OSI Model
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OSI Model Overview• The Open Systems
Interconnection (OSI) reference model is an industry standard framework that is used to divide the functions of networking into seven distinct layers.
• Each layer provides specific services to the layers above and below it in order for the network to work effectively.
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OSI Model Overview• A message begins at the top
application layer and moves down the OSI layers to the bottom physical layer.
• As the message descends, each successive OSI model layer adds a header to it.
• A header is layer-specific information that basically explains what functions the layer carried out.
• Conversely, at the receiving end, headers are striped from the message as it travels up the corresponding layers.
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What is a Protocol?• Protocol is a controlled
sequence of messages that is exchanged between two or more systems to accomplish a given task.
• Protocol specifications define this sequence together with the format or layout of the messages that are exchanged.
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Transmission Control Protocol/Internet Protocol
• The Transmission Control Protocol/Internet Protocol (TCP/IP) suite of protocols has become the dominant standard for inter-networking.
• TCP/IP represents a set of public standards that specify how packets of information are exchanged between computers over one or more networks.
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Transmission Control Protocol/Internet Protocol
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Internetwork Packet Exchange/Sequenced Packet
Exchange• Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) is the protocol suite employed originally by Novell®.
• It delivers functions similar to those included in TCP/IP.
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NetBEUI• NetBIOS Extended User Interface (NetBEUI) is a
protocol used primarily on small Windows NT networks.
• NetBEUI is a simple protocol that lacks many of the features that enable protocol suites such as TCP/IP to be used on networks of almost any size.
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AppleTalk• AppleTalk is comprised of
a e set of protocols that span the seven layers of the OSI reference model.
• AppleTalk protocols were designed to run over the major LAN types, notably Ethernet and Token Ring, and also Apple's own LAN physical topology, LocalTalk.
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TCP/IP Utilities
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Overview• TCP/IP is a complex
collection of protocols.• Most vendors implement
the suite to include a variety of utilities for viewing configuration information and troubleshooting problems.
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Ping• Ping works by sending an ICMP echo request to the
destination computer. • The receiving computer then sends back an ICMP
echo reply message • It is also possible to use Ping to find the IP address of
a host when the name is known.
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ARP, RARP, NSLOOKUP• Address Resolution Protocol
(ARP) is the means by which networked computers map Internet Protocol (IP) addresses to physical hardware (MAC) addresses that are recognized in a local network.
• Machines that do not know their IP addresses use Reverse Address Resolution Protocol (RARP).
• It is used to obtain IP address information based on the physical or MAC address.
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ARP, RARP, NSLOOKUP• Nslookup returns the IP address for a given
hostname.
• It will also do the reverse and find the host name for a specified IP address.
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Netstat/tpcon• The netstat command is used in Windows and UNIX/Linux
to display TCP/IP connection and protocol information.
• The netstat command provides a list of connections that are currently active.
• Netstat statistics can be useful in troubleshooting TCP/IP connectivity problems.
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Nbtstat• The Microsoft TCP/IP
stacks included in Windows operating systems provide the nbtstat utility, which is used to display NetBIOS information.
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Ipconfig, winipcfg, config, and ifconfig
• TCP/IP configuration information can be displayed using different utilities
• Ipconfig – Windows NT and Windows 2000 (command-line)
• Winipcfg –- Windows 95, 98, and ME (graphical interface)
• Ifconfig – UNIX and Linux (command-line
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Tracert, iptrace, and traceroute• It is often useful to trace the
route a packet takes on its journey from source computer to destination host.
• TCP/IP stacks include a route tracing utility that enables users to identify the routers through which the message passes.
• The options depend on the operating system: – Tracert– Iptrace– Traceroute
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Connecting to the Internet
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Synchronous and Asynchronous Serial lines
• Synchronous serial transmission – Data bits are sent together with a synchronizing clock pulse. Built-in timing mechanism coordinates the clocks of the sending and receiving devices.
• Asynchronous serial transmission – Data bits are sent without a synchronizing clock pulse. Uses a start bit at the beginning of each message. When the receiving device gets the start bit, it can synchronize its internal clock with the sender clock.
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Modems• The modem is an electronic
device that is used for computer communications through telephone lines.
• It allows data transfer between one computer and another.
• There are four main types of modems:– Expansion cards – PCMCIA – External modems– Built-in modems
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Dial-Up Networking, Modem Standards, AT Commands
• When computers use the public telephone system or network to communicate, it is called Dial-Up Networking (DUN).
• All modems require software to control the communication session.
• The set of commands that most modem software uses are known as the Hayes-compatible command set. The Hayes command set is based on a group of instructions that always begins with a set of attention characters (AT).
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ISPs and Internet Backbone Providers
• Services of an Internet Service Provider (ISP) are required to surf the Internet.
• An ISP is a company that connects computers to the Internet and World Wide Web.
• The actual connection to the Internet is tiered.
• The ISP may link to a larger regional ISP, which in turn might connect to one of a number of nationwide computer centers.
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ISPs and Internet Backbone Providers
• The current U.S. Internet infrastructure consists of a commercial backbone and a high-speed service known as the Very High-Speed Backbone Network Service (vBNS).
• The vBNS connects five supercomputer networks across the country:– UUNET - a division of WorldCom – Cable & Wireless USA – Sprint – AT&T – BBN Planet
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ISPs and Internet Backbone Providers
• The ISP that cannot connect directly to the national backbone is charged a fee to connect to a regional provider that links to the national backbone through a Network Access Point (NAP).
• Not all the Internet traffic goes through NAPs.
• Some ISPs that are in the same geographic area make their own interconnections and peering agreements.
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Digital Subscriber Line (DSL)• Digital Subscriber Line (DSL) is an always-on
technology. This means there is no need to dial up each time to connect to the Internet.
• DSL comes in several varieties:
– Asymmetric DSL (ADSL)
– High Data Rate DSL (HDSL)
– Symmetric DSL (SDSL)
– Very High Data Rate DSL (VDSL)
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Cable Modems• A cable modem acts like a
LAN interface by connecting a computer to the Internet.
• The cable modem connects a computer to the cable company network through the same coaxial cabling that feeds cable TV (CATV) signals to a television set.
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Cable Modem versus DSL Internet Technologies
• When it comes to comparing cable modem and DSL Internet technologies, both have their pros and cons.
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ISDN
• Another alternative to using analog telephones lines to establish a connection is ISDN.
• Speed is one advantage ISDN has over telephone line connections.
• ISDN uses a pair of 64Kbps digital lines to connect, which provides a total of 128Kbps throughput.
• A telephone line connects at a maximum speed of 56Kbps, and in some areas, doesn’t even reach that.
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Satellite
• Satellite is an option for users in rural areas or with no other access to high speed Internet service.
• Satellite Internet does not require a phone line or cable. Two‑way communication, for upload and download, is achieved with the use of a satellite dish.
• Download speed is up to 500 kbps while the upload speed is one‑tenth of that of that.
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