Understanding Networks
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Transcript of Understanding Networks
![Page 1: Understanding Networks](https://reader035.fdocuments.net/reader035/viewer/2022062408/56813424550346895d9b1126/html5/thumbnails/1.jpg)
Understanding Networks
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Objectives• Compare client and network operating
systems
• Learn about local area network technologies, including Ethernet, Token Ring, FDDI, and wireless
• Use the OSI model to understand networking
• Learn how network computers and servers are addressed
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TCP/IP Protocols at Each Layer
• TCP/IP covers the first five layers of the
OSI model, and is included in an operating
system as a group of utilities called the
TCP/IP stack.
• Figure 5-41 shows the four major
groupings of the OSI model as applied to
TCP/IP networks.
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Protocols at the Application, Presentation, and Session Layers
• The first three layers of the OSI model are handled by the protocol specific to the application using it and are best treated as a single group rather than unique layers.
• Web browsers, e-mail, chat rooms, and FTP software are examples of the applications that use the Internet.
• The language or protocol each of these applications uses is listed at the Application, Presentation, and Session layers.
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Protocols at the Transport Layer
• A TCP/IP network has two protocols that work at the Transport layer; one protocol guarantees delivery and the other does not.
• With TCP/IP, the protocol that guarantees delivery is TCP and the protocol that does not is UDP (User Datagram Protocol).
• TCP is used for client and server requests and responses.
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Protocols at the Transport Layer (Continued)
• Because TCP establishes a connection, it is called a connection-oriented protocol.
• UDP is a protocol that sends data without caring about whether the data is received.
• It does not establish a connection first; thus, it is called a connectionless protocol.
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Protocols at the Network Layer• TCP and UDP communicate with the Network
layer, which is sometimes called the Internet layer.
• Some of the other supporting protocols include ARP (Address Resolution Protocol), responsible for locating a host on a LAN; RARP (Reverse Address Resolution Protocol), responsible for discovering the Internet address of a host on a LAN; and ICMP (Internet Control Message Protocol), responsible for communicating problems with transmission to devices that need to know about these problems.
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Protocols at the Data Link and Physical Layers
• PPP (Point-to-Point Protocol) is used
over telephone lines, and allows a
computer to connect to a network using a
modem.
• PPP is the most popular protocol for
managing network transmission from one
modem to another.
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MAC Addresses
• MAC addresses function at the lowest
(Data Link) networking level.
• If a host does not know the MAC address
of another host on a local area network, it
uses the operating system to discover the
MAC address.
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IP Addresses
• All the protocols of the TCP/IP suite identify a device on the Internet or an intranet by its IP address.
• An IP address is 32 bits long, made up of 4 bytes separated by periods.
• Within an IP address, each of the four numbers separated by periods is called an octet.
• The first part of an IP address identifies the network, and the last part identifies the host.
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Classes of IP Addresses• IP addresses that can be used by companies
and individuals are divided into three classes: Class A, Class B, and Class C, based on the number of possible IP addresses in each network within each class.
• The group of IP addresses assigned to an organization are unique to all other IP addresses on the Internet and are available for use on the Internet.
• The IP addresses available to the Internet are called public IP addresses.
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Private IP Addresses• Private IP addresses are IP addresses
that are assigned by a network administrator for use on private intranets that are isolated from the Internet.
• The RFC 1918 recommends that the following IP addresses be used for private networks:– 10.0.0.0 through 10.255.255.255
– 172.16.0.0 through 172.31.255.255
– 192.168.0.0 through 192. 168. 255.255
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Dynamically Assigned IP Addresses
• Instead of IP addresses permanently being assigned to computers (called static IP addresses), an IP address is assigned for the current session only (called a dynamic IP address).
• Internet service providers (ISPs) are organizations through which individuals and businesses connect to the Internet.
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Network Address Translation
• If the hosts on a network using private IP addresses need to access the Internet, a problem arises because the private IP addresses are not allowed on the Internet.
• The solution is to use NAT (Network Address Translation), which uses a single public IP address to access the Internet on behalf of all hosts on the network using other IP addresses.
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Plans for New IP Addresses
• Because of an impending shortage of IP addresses, as well as some limitations in the current standards for IP, a new scheme of IP addresses called the IPv6 (IP version 6) standard is currently being developed and implemented.
• Current IP addresses using the current IPv4 (IP version 4) have 32 bits with eight bits in each of four octets.
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Plans for New IP Addresses (Continued)
• With the new system, each address segment can have 32 bits, for a total of 128 bits for the entire address.
• A disadvantage of IPv6 is the fact that so much software used on the Internet would become outdated because current software is designed to hold 32-bit IP addresses and, with the new system, this number would no longer be sufficient.
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Ports• A port is a number used to address
software or services running on a computer.
• A host computer might have several services running on it.
• Each server running on the host is assigned a port.
• The port is written at the end of the IP address, separated from the IP address with a colon—like this: 169.49.209.19.80.
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Tying It All Together: How Data Travels on the Network
• The Web browser wants to make a request to a Web server, and processes the request using an API call.
• The API process packages the data using HTTP format, which includes an HTTP header, and addresses it to an IP address and port 80, which is the default port for a Web server.
• HTTP delivers the package to TCP, giving the destination IP address and port.
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Tying It All Together: How Data Travels on the Network (Continued)• TCP guarantees delivery, and attempts to make
a connection to the destination IP address and port using the three-way handshake.
• With the first attempt that TCP makes to communicate with the remote host, the first packet reaches the Network layer and IP uses ARP to resolve the IP address to a MAC address.
• When a packet reaches a hub on the Ethernet LAN, the hub replicates the packet and sends it to every device to which it is connected.
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Tying It All Together: How Data Travels on the Network (Continued)• When the IP layer receives a broadcast
packet, it decides if it is appropriate to respond.
• After it knows the MAC address, it can send the first packet to make the connection.
• It prepares the data by attaching a TCP header in front of the data.
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Summary
• The two approaches to managing network resources are peer-to-peer and client/server.
• Windows 2000 Server and Windows Server 2003 support multiple domain controllers.
• Windows XP has three operating systems: Windows XP Professional, Windows XP Home Edition, and Windows XP 64-Bit Edition.
• The most popular network technology used today is Ethernet; it can be configured either as a star or bus.
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Summary (Continued)
• An IP address can be permanently assigned to a device (static IP addressing) or a different IP address can be assigned each time the device logs on to the network (dynamic IP addressing).
• When a host is configured to used TCP/IP, and IP address is bound to the MAC address.
• A proxy server uses NAT to substitute its own public IP address for the private IP address of a computer on the network that is requesting Internet access.