Linux Operations and Administration Chapter Eight Network Communications

Linux Operations and Administration 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 2

Linux Operations and Administration 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 3

Linux Operations and Administration 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 4

Linux Operations and Administration 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 5

Linux Operations and Administration 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 6

Linux Operations and Administration 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 7

Linux Operations and Administration Internet Layer (cont’d.) 8 Figure 8-1 Information traveling through a network ©Cengage Learning 2013

Linux Operations and Administration 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 9

Linux Operations and Administration 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 10

Linux Operations and Administration 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 11

Linux Operations and Administration Transport Layer (cont’d.) 12 Table 8-1 Differences between TCP and UDP

Linux Operations and Administration 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 13

Linux Operations and Administration Application Layer (cont’d.) 14 Table 8-2 Important protocols in the Application layer

Linux Operations and Administration Application Layer (cont’d.) 15 Figure 8-2 Placement of protocols in the TCP/IP model © Cengage Learning 2013

Linux Operations and Administration 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: –ifconfig command Can be used to view a computer’s IP address and the current state of all its active network interfaces 16

Linux Operations and Administration Working with IP Addresses (cont’d.) 17

Linux Operations and Administration 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 18

Linux Operations and Administration 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 19

Linux Operations and Administration Binary and Decimal Numbering Systems (cont’d.) Table 8-3 –Lists the powers of two from 0 to 7 Decimal number 112 converts to binary number Activity 8-2: Converting from Decimal to Binary –Convert a 32-bit IP address into four 8-bit binary octet 20

Linux Operations and Administration Binary and Decimal Numbering Systems (cont’d.) 21 Table 8-3 The powers of two

Linux Operations and Administration 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 22

Linux Operations and Administration 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 23

Linux Operations and Administration 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 , it converts the decimal 255 to the binary

Linux Operations and Administration Subnet Masks (cont’d.) 25 Figure 8-3 A subnet mask © Cengage Learning 2013

Linux Operations and Administration Subnet Masks (cont’d.) 26 Figure 8-4 Network and host IDs in an IP address © Cengage Learning 2013

Linux Operations and Administration 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 27

Linux Operations and Administration IP Address Classes (cont’d.) 28 Table 8-4 IP address classes

Linux Operations and Administration Class A Networks Their subnet mask is 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 29

Linux Operations and Administration Class B Networks Their subnet mask is The first two bits are always 10 Assigned to large organizations –Such as government agencies, universities, and typical companies 30

Linux Operations and Administration Class C Networks Their subnet mask is 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 31

Linux Operations and Administration 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) 32

Linux Operations and Administration 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 33

Linux Operations and Administration Using the ifconfig Command Using the ifconfig command without arguments displays network settings 34

Linux Operations and Administration 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 35

Linux Operations and Administration Using the ifconfig Command (cont’d.) –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 All devices using TCP/IP require the loopback address 36

Linux Operations and Administration Using the ifconfig Command (cont’d.) 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 37

Linux Operations and Administration 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

Linux Operations and Administration The ping Command (cont’d.) 39

Linux Operations and Administration The ping Command (cont’d.) 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 40

Linux Operations and Administration The ping Command (cont’d.) 41 Table 8-5 Options used with the ping command

Linux Operations and Administration 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 42

Linux Operations and Administration 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 43