IT Essentials II Network Operating Systems

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IT Essentials IINetwork Operating Systems

• Chapter 4TCP/IP Networking

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Birth of the Internet

• U.S. Defence Department's Advanced Research
  Projects Agency (DARPA), produced the designs and
  experimental networks that evolved into the
  public Internet
• DARPA also accelerated the spread of Transmission
  Control Protocol /Internet Protocol (TCP/IP) by
  including it in distributions of the UNIX
  operating system
• Based on TCP/IP open standards, the Internet has
  been enormously successful

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TCP/IP Network Model

• The TCP/IP network model is based on the OSI
  reference model and is the predominant protocol
  suite used in networking today
• Application layer
• Defines the applications
• Transport layer
• Defines TCP UDP only
• Internet layer
• Defines addressing path selection
• Network Access layer
• Defines specific functions for preparation of
  data for transmission, also what type of media
  can be used

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TCP/IP Protocols
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IPv4 Addressing Overview

• For any two systems to communicate, they must be
  able to identify and locate each other
• Uses binary (1s and 0s)
• 32 bit address broken into 4 Octets
• Hierarchical address system
• Broken into two parts
• Network identifier
• Machine/Host identifier
• Must be a unique number

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IPv4 Addressing Classes

• Class A addresses
• 0 127 although 127.x.x.x range is reserved as
  a loopback address
• Class B addresses
• 128 - 191
• Class C addresses
• 192 - 223
• Class D (Multicast) addresses
• 224-239
• Class E (Experimental) addresses
• 240-254

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IPv4 Addressing Classes
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IP Addressing Example

• If given an unsubnetted Class C address of
• 192.168.4.0
• Network address is
• 192.168.4.0
• Broadcast address is
• 192.168.4.255
• Subnet mask is
• 255.255.255.0
• Host addresses are in the range
• 192.168.4.1 to 192.168.4.254

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IPv4 Address Crisis

• Problem - exhausted Internet address space
• Solutions
• Subnetting of Networks
• Private IP Addresses
• NAT (Network Address Translation)
• IPv6 Addressing

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Subnetting of Networks

• Dividing of a network into smaller parts using
  the same network number
• IP address now divided into
• Network Subnet Host
• Also now makes use of Subnet Mask
• Binary, 32 bit, broken into 4 Octets
• 1s indicate Network/Subnet portion
• 0s indicate Host portion

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Private IP Addresses

• Can be used in corporate or home networks
• Cannot be used over the Internet
• Private Address Ranges
• Class A 10.0.0.0 to 10.255.255.255
• Class B 172.16.0.0 to 172.31.255.255
• Class C 192.168.0.0 to 192.168.255.255
• Must be used with NAT

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Network Address Translation (NAT)

• Translates public IP addresses to private IP
  addresses
• Provides some security as IP addresses of
  internal hosts are not known to external devices

Source 10.0.0.25
Source 19.0.0.64
10.0.0.25
19.0.0.64
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Internet Protocol Version 6 (IPv6)

• 128-bit addressing
• Expected to gradually replace IPv4
• Written in hexadecimal
• 108000000000000000080800200C417A
• Leading zeros in each 16-bit value can be omitted
• 10800008800200C417A
• Consecutive 16-bit values of zero can be omitted
• 10808800200C417A

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Name Resolution

• Easier to remember names than IP addresses
• Hostnames
• Unique names for hosts
• Host tables
• Associate names with IP addresses on each host
• The domain name system (DNS)
• Relieves hosts needing host tables as now stored
  on a DNS server
• Name services and the NOS
• Network Basic Input/Output System (NETBIOS) IBM
• Windows Internet Naming Service (WINS)
• Not a built-in part of DNS service
• Translates NETBIOS names into IP addresses

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TCP/IP Protocols

• What is a protocol?
• a set of messages that is exchanged between
  systems in a defined sequence in order to
  accomplish a specific networking task
• Address Resolution Protocol (ARP)
• Maps known IP to MAC address
• Internet Control Message Protocol (ICMP)
• A set of error and control messages to help track
  and resolve network problems
• Transmission Control Protocol (TCP)
• Reliable delivery method

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TCP/IP Protocols

• Internet Protocol (IP)
• Forward message to next network by best effort
• User Datagram Protocol (UDP)
• Unreliable delivery method
• DHCP services
• Provides hosts with IP configuration information
• Hypertext Transport Protocol (HTTP)
• Rules for transporting web pages
• Hypertext Mark-up Language (HTML)
• How the content of a web page is organised

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TCP/IP Protocols

• File Transfer Protocol (FTP)
• Used to transfer any file from A to B
• Telnet
• Allows users to connect to remote systems through
  terminal emulation
• SMTP
• Used to send e-mails to/between servers
• POP3
• Used to retrieve e-mails from servers
• IMAP
• Used to access electronic mail and bulletin
  boards
• Replacing POP3 in some ISPs

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Questions?