A Closer Look at TCPIP, IP Address, DNS

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A Closer Look at TCP/IP,IP Address, DNS
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Outline

• Basic TCP/IP
• Internet Address
• Domain Name System (DNS)
• Network Commands and Software

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TCP/IP the Communication Standard of the
Internet
Transmission control protocol/Internet protocol
Layers
TCP/IP
Application
Application
Transport (TCP)
Network Communication
Internet (IP)
Data Link
Subnet
Physical
Physical
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Making Sense of TCP/IP Layers
What we usually deal with Applications (HTTP,
FTP, Telnet, etc.)
Ever wondered how data move around? Communication
protocols (TCP and IP)
The lowest level Physical Infrastructure (network
s such as copper wire or optical fiber.)
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Protocol Data Units (PDUs)

• PDUs are structured messages through which
  different network layers communicate.
• PDUs are nested
• PDUs at the Internet layer are called packets.

Application TCP IP Data link
HTTP-PDU
HTTP-PDU
TCP Header
TCP-PDU
IP Header
IP Packet
H
T
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Transport (TCP) Layer

• Applications (e.g. HTTP) uses the transport layer
  for the end-to-end delivery of packets
• Where does TCP run?
• TCP (Transmission control protocol) performs
  following tasks
• fragmenting messages into packets and
  reassembling packets into messages
• controlling errors by arranging for erroneous
  packets to be retransmitted
• TCP will slow down when the traffic is busy

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Network (IP) Layer

• IP (The Internet Protocol) does the job of
  routing data between senders receivers
• IP host computer encapsulate TCP-PDU into IP
  headers
• IP header includes information such as
  destination network address and source network
  address
• IP layer sees network links as simple links that
  will pass packets between routers

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TCP/IP Partnership

• TCP checks for errors at the destination host
• IP is used in many hops between source host and
  destination host
• Current version IPv4
• Not checking for errors at each step greatly
  reduces the work the routers must do
• Does its best to get packets through
• No guarantees of delivery
• QoS is needed in the future

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Internet Addresses

• Also called IP addresses
• Example 128.83.40.16
• Really 32-bit strings of 1s and 0s
• Fit into source and destination address field of
  IP headers

IP Packet
32-bit Destination and Source Addresses
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Internet Address Rules

• Hierarchical Addressing
• An IP address has two parts
• A network address, same for all hosts on a given
  network (organization on the Internet)
• A node or station address which is unique for
  each machine on a given network (host on the
  network)
• For example

Network Part
128.83.40.16
Local Part
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Internet Address Classes

• Each has a different number of bits in the
  network part (and therefore local part)
• Class A 8 bits in network part (so 24 bits in
  local part)
• Class B 16 bits (16 bits in local part)
• Class C 24 bits (8 bits in local part)

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Class A IP Addresses

• First byte (8 bits) identifies the network
• First bit set to 0 (class identifier)
• Maximum number of class A networks is only 128.
  Why?
• The remaining three bytes (24 bits) are in local
  part and are used for station addresses
• Can have over 16 million hosts per Class A
  network!
• All Class A network parts are assigned or
  reserved
• Assigned to some universities involved in ARPANET
  project. What a waste !

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Class B Addresses

• First two bytes are used to identify the network
• First two bits set to 10
• 14 remaining bits in network part
• Over 16,000 possible Class B networks, why?
• 16 bits in local part
• Over 65,000 possible hosts, why?
• A good trade-off between number of networks and
  hosts per network
• Most have been assigned

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Class C Addresses

• First three bytes for the network address and 1
  byte for station address
• First three bits set to 110
• 21 more bits in network part
• Over 2 million possible Class C networks!
• 8 bits in local part
• Only 256 possible hosts per Class C network!
• Unpopular, because large firms must have big
  enterprise network and need several class C
  addresses.
• If you have more than 256 computer, you have to
  get several C class networks.

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Domain Name System (DNS)

• Users typically only know host names
• e.g., www.nd.edu
• Preferred more easily remembered
• But only internet addresses are parts of the IP
  header. Host name will not fit into the address
  fields of an IP packet.

IP Packet
www.nd.edu
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Finding IP Address

• Client sends DNS Server the destination host name
  in the DNS-Request-PDU
• DNS Server returns the destination hosts
  internet address in the DNS-Response-PDU
• Organizations or ISPs have local DNS Servers
• These servers only know local host names and
  corresponding internet addresses
• For other host names, local DNS server passes
  request to a DNS root server

www.nd.edu
Internet Layer Process
Local DNS Server
Root DNS Server
129.74.226.69
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Domain Names

• Internet uses hierarchical naming
• A domain is a collection of resources managed by
  an organization
• A domain name is simply a name for a computer
• Top level domains by type of organization
• .com for commercial organizations
• .edu for educational institutions
• .net originally for ISPs and NSPs
• .org originally for non-profit org.
• .gov for government
• .com, .net, .org are mostly free to choose

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How to Register a Domain Name

• Get an IP from ISP
• Come up with a great name and check at
  www.networksolutions.com
• Register at www.networksolutions.com
• Needs at least two IP address for Domain Name
  Server

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Some Useful Network Commands

• Using at MS DOS prompt
• tracert ltmachine_addressgt
• trace route to the machine
• nslookup ltdomain namegt
• to query IP address
• ping ltmachine_addressgt
• check alive or not
• VisualRoute http//www.visualroute.com/

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Recap