Transmission Control Protocol / Internet Protocol and Network Utilities

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Transmission Control Protocol / Internet Protocol
and Network Utilities

• Colin Jamison
• University of Ulster

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Network Protocols

• Protocol - used by computers to exchange
  information over a network
• The most common is TCP/IP originated by the U.S
  department of Defence
• If IP is the native language of the Internet
• then
• TCP represents one of many specialised dialects

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Sockets

• De facto portable standard for portable
  applications on TCP/IP
• Sockets available on most PC OSs and Mainframes
• Internet Address(IP) and Port Address
• netid . hostid . portid

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Allocation of IP addresses

• Network Information Centre (NIC)
• NIC handles the administration of IP address
  allocation to an organisation
• 5-types of IPv4 IP addresses can be allocated
• Class A, Class B, Class C, Class D, Class E
• These allow the internet address to be broken
  into blocks of small, medium and large networks

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IP Address Format
Represented by a string of 4-bytes separated by
full-stops
Each byte contains 8 bits - so each byte ranges
from 0 to 255 decimal
or 0000 0000 to 1111 1111 binary
From 000.000.000.000
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Breakdown of the IP Address

• The IP address consists of 2 parts which are, a
  netid and a hostid

1 7 24
32
2 14 16
32
3 21 8
32
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IP Address Classes

• Class A for extremely large networks (up 16
  million hosts) - no longer issued
• Class B for medium sized networks (65534 hosts)
• Class C for small networks (254 hosts)
• Class D reserved for multicast
• Class E reserved

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Breakdown of IP Address Classes

• Class A 1.0.0.0 - 126.0.0.0
• Class B 129.0.0.0 - 191.255.0.0
• Class C 192.0.0.0 - 223.255.255.0
• Class D 224.0.0.0 - 239.255.255.0
• Class E 240.0.0.0 - 255.255.255.0

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Host Addresses (1)

• Each computer network interface is identified by
  a unique IP address
• If a computer has more than one interface then it
  uses multiple IP addresses - one for each
  interface

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Host Addresses (2)

• Each packet has a destination address
• All hosts on the network examine each broadcast
  packet
• If addressed to them then the host processes it -
  otherwise it is ignored

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Limit to the Number of Hosts

• 2 IP addresses are reserved in each type of
  class,and these are 0
• e.g. 194.23.12.0 which is the address of the
  network itself
• and
• 255 which is the broadcast address
• e.g. 194.23.12.255

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Subnets

• Each host must determine if a broadcast packet is
  for it
• For a large number of hosts each host must
  process many packets
• To maintain efficiency in a network the network
  is split into sub-networks (subnets)
• The network is divided by sub-netting to create
  self-contained broadcast domains

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Subnet Masks

• A subnet mask is a bit mask that allows you to
  determine which parts of an IP address correspond
  to the -
• 1) network address, and
• 2) subnet
• When you AND an IP address and a subnet mask the
  result is an address that contains everything but
  the hostid

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Resolving IP Addresses
Binary Class B
Class B netid hostid 1000
1100 . 1100 1100 . 0001 1011 . 0001 1011
Decimal
Class B Class B netid hostid IP Address
131 .204 .27 .27
Subnet Mask 255 .255 .255 .0
1111 1111 . 1111 1111 . 1111 1111 . 0000 0000
1000 1100 . 1100 1100 . 0001 1011 . 0000 0000
Subnet Number 131 .204
.27 .0
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Network Utilities

• netstat
• route
• arp
• ifconfig
• ping
• traceroute

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netstat

• Netstat prints information about the Linux
  networking subsystem
• The type of information printed is controlled by
  the option given
• -a displays both listening and non-listening
  sockets
• -r displays the routing table
• /bin/netstat

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route

• Used to add or delete to the kernels IP routing
  table.
• Its primary use is to setup static routes to
  specific hosts or networks
• Without options it displays the current contents
  of the routing table
• /sbin/route

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arp

• Manipulates the kernels address resolution
  protocol (ARP) cache in various ways
• The main use is to setup and clear an address
  mapping entry
• /sbin/arp -a

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ifconfig

• ifconfig is used to configure the kernels
  resident network interfaces
• it is used at boot time to set up the computers
  interfaces
• If no arguments are specified it displays the
  status of the given interface only
• If -a is specified it displays the status of all
  interfaces
• /sbin/ifconfig

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ping

• Used to send packets to a destination hostname or
  IP address and display the response from the
  destination
• Useful to detect intermittent or non-existent
  network connectivity
• ping destination

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traceroute

• Traces the path of packets through the local
  network or Internet to the specified destination
• The destination can either be a hostname or IP
  address
• Useful as a network debugging aid
• /usr/sbin/traceroute destination

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• Questions?