linux operations and administration chapter eight network communications

Linux Operations and Administration

Chapter EightNetwork Communications


Objectives

• Identify the important protocols at each layer of the TCP/IP model

• Describe IP addresses and the difference between the network and host portions of an IP address

• Convert decimal IP addresses into binary numbers

• Describe the five TCP/IP classes

• Configure your Linux network interface card to work with TCP/IP, using the command line

• Interact with network devices by using the ping command

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Introduction to TCP/IP

• Transmission Control Protocol/Internet Protocol (TCP/IP)– An internationally accepted set of rules for

connecting computers to the Internet and most other networks

• Network– Two or more computers connected with a medium

for the purpose of sharing resources

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Introduction to TCP/IP (cont’d.)

• Two most important protocols in TCP/IP suite:– Transmission Control Protocol– Internet Protocol

• Activity 8-1: Researching the TCP/IP Protocol Suite– Learn about several protocols in the TCP/IP suite

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Working with TCP/IP

• Layers in the TCP/IP model:– Application layer

• Receives packets from Transport layer

• Opens packets to convert the message back to its original form

– Transport layer• Responsible for delivering data from one location to

another on the network

– Internet layer• Receives packets and then routes them to the correct

destination

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Working with TCP/IP (cont’d.)

• Hardware layers:– Not part of the TCP/IP protocol suite– Data Link layer

• Formats data as packets

– Physical layer• Consists of cables or other connection media

• Deals with data as bits traveling across a network medium

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Internet Layer

• Sends packets to their specified destinations

• Adds an IP-specific header to the packet• Header contains information such as:

– Source– Destination– Version– Internet header length– Protocol– Other information about the data

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Internet Layer (cont’d.)

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Figure 8-1 Information traveling through a network©Cengage Learning 2013


Internet Layer (cont’d.)

• Internet Protocol (IP)– Contains addressing information that enables

packets to be routed– Two basic functions of IP are addressing and

fragmentation

• Internet Control Message Protocol (ICMP)– Used to generate IP error messages

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Transport Layer

• Responsible for delivering data from one location to another on the network

• Transmission Control Protocol (TCP)– Connection-oriented protocol– Keeps track of packets and reassembles them into a

single file after they’ve all arrived– Controls the flow of messages

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Transport Layer (cont’d.)

• User Datagram Protocol (UDP)– Connectionless protocol– Doesn’t perform error checking or acknowledge that

messages were sent successfully

• Table 8-1– Summarizes the differences between TCP and UDP

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Transport Layer (cont’d.)

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Table 8-1 Differences between TCP and UDP


Application Layer

• Sits at the top of the TCP/IP model

• Contains the higher-level protocols used for network communication in the Transport layer

• Table 8-2– Describes some important protocols in this layer

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Application Layer (cont’d.)

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Table 8-2 Important protocols in the Application layer


Application Layer (cont’d.)

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Figure 8-2 Placement of protocols in the TCP/IP model© Cengage Learning 2013


Working with IP Addresses

• IP address– A unique number that identifies a computer or device

on a TCP/IP network– Format

• Four numbers separated by periods

• Example: 192.168.75.136

– ifconfig command• Can be used to view a computer’s IP address and the

current state of all its active network interfaces

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Working with IP Addresses (cont’d.)

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Binary and Decimal Numbering Systems

• Decimal numbers– Used in IP addresses– Have 10 possible digits (0 to 9)

• Binary numbering system– Uses only two digits (1 and 0)– Used in computers

• Computers convert decimal IP addresses into binary numbers

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Binary and Decimal Numbering Systems (cont’d.)

• Bit (also known as a binary digit)– Represents a single binary value

• IP addresses– Decimal numbers divided into four octets– Each octet is 8 bits– An IP address has 32 bits

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• Table 8-3– Lists the powers of two from 0 to 7

• Decimal number 112 converts to binary number 01110000

• Activity 8-2: Converting from Decimal to Binary– Convert a 32-bit IP address into four 8-bit binary

octet

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Table 8-3 The powers of two


Network and Host Identifiers

• An IP address is composed of two parts:– Network ID

• Identifies the network where the host is located

– Host ID• Identifies a computer or device on a network

• Computers can communicate only with other computers on the same network– They must have the same network ID to exchange

information

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Network and Host Identifiers (cont’d.)

• Router– Used to connect networks and forward packets to

their destinations– Needed to communicate with computers having

different network IDs

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Subnet Masks

• Subnet mask– Used to determine which part of an IP address is the

network ID and which part is the host ID

• A subnet mask is 32 bits

• Example– When a computer reads the IP address

255.255.255.0, it converts the decimal 255 to the binary 11111111

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Subnet Masks (cont’d.)

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Figure 8-3 A subnet mask© Cengage Learning 2013


Subnet Masks (cont’d.)

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Figure 8-4 Network and host IDs in an IP address© Cengage Learning 2013


IP Address Classes

• IP addresses are divided into five classes to accommodate varying network sizes– Class A, Class B, and Class C: most common

classes– Class D and E networks are for multicasting and

experimentation

• Table 8-4– Describes the different IP address classes

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IP Address Classes (cont’d.)

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Table 8-4 IP address classes


Class A Networks

• Their subnet mask is 255.0.0.0

• The first bit is always 0

• There can be only 127 Class A networks on the entire Internet– Allows 16,777,214 hosts per network

• Assigned to ISPs or very large companies

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Class B Networks


• The first two bits are always 10

• Assigned to large organizations– Such as government agencies, universities, and

typical companies

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Class C Networks


• The first three bits are always 110

• More than 2 million Class C networks are possible– Each network can have only 254 hosts

• Assigned to small organizations

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Configuring Network Interface Cards

• OpenSUSE includes tools and utilities to configure many hardware devices– Such as printers, network cards, modems, etc.

• Linux provides commands such as ifconfig for configuring a network interface card (NIC)

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Using the ifconfig Command

• ifconfig command is used to:– View a computer’s IP address and the current state

of all active network interfaces on it– Configure NICs

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Using the ifconfig Command

• Using the ifconfig command without arguments displays network settings

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Using the ifconfig Command (cont’d.)

• Output description– Link encap—specifies the type of interface– HWaddr—specifies the hardware address (also

known as the MAC address) of a NIC– inet addr—specifies the IP address as well as the

broadcast address (Bcast) and the netmask (Mask)– RX packets—specifies the number of packets

received (RX)• Also shows the number of errors and dropped packets

and how many packets were too long

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– TX packets—displays packets transmitted from the computer over the network

• Shows error information

– Interrupt—displays the computer’s configuration settings

• If you have only one NIC, it’s labeled eth0– All other NICs are labeled eth1, eth2, etc.

• The lo represents the loopback adapter with an IP address of 127.0.0.1

• All devices using TCP/IP require the loopback address

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• ifconfig command can be used to configure NIC with the following syntax:ifconfig interface IP address netmask options

• netmask refers to the subnet mask you want to assign to the interface

• Activity 8-3: Using the ifconfig Command– View and configure TCP/IP settings with the ifconfig command

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The ping Command

• Uses ICMP to send an Echo Request packet to a specified network device on the network and waits for a reply

• Used by administrators in network testing, measurement, and management

• Example: ping 192.168.0.6

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The ping Command (cont’d.)

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• Each ping request produces a result, including:– icmp_seq– Time to live (ttl)– Packet request’s round-trip time

• Table 8-5– Describes the options you can use with the ping

command

• Activity 8-4: Using the ping Command– Test your TCP/IP configuration with the ping

command

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Table 8-5 Options used with the ping command


Summary

• TCP/IP– A suite of networking protocols– Three layers: Application, Transport, and Internet

• IP and ICMP: major protocols at Internet layer– IP contains addressing information– ICMP is used to generate IP error messages

• TCP and UDP: major protocols at Transport layer– TCP is a connection-oriented protocol– UDP is a connectionless protocol

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Summary (cont’d.)

• FTP and HTTP: protocols at Application layer

• IP address– Two-part (network ID and host ID) unique number that

identifies a device on a TCP/IP network– Decimal IP addresses are converted into binary

numbers

– IP addresses are divided into classes

• ifconfig command is used to view and modify TCP/IP configuration settings

• ping command is used in network testing, measurement, and management

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linux operations and administration chapter eight network communications

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