Layering and the TCP/IP protocol Suite

1
Layering and the TCP/IP protocol Suite

• The TCP/IP Protocol only contains 5 Layers in its
  networking Model
• The Layers Are
• Physical -gt 1 in OSI
• Network Interface -gt 2 in OSI
• Internet -gt 3 in OSI (loosely)
• Transport -gt 4 in OSI
• Application -gt 5, 6, 7 in the OSI Model

2
Internet Protocol Addresses (IP)

• The IP standard (IPV4) states that each host on a
  network will contain a unique 32 bit number.
• This number is known as the IP address of the
  host.
• Both the Senders IP address and the Receivers IP
  address are sent in each packet over the internet.

3
IP Address Hierarchy

• Each IP is divided into two parts
• Network Number (prefix)
• Host ID (suffix)
• Prefix or network numbers are granted globally
• The hierarchy guarantees two important
  properties.
• Each computer can have a Unique ID
• Each suffix can be granted locally without global
  coordination.

4
IP address Classes

• Network numbers can be further divided into
  different classes.
• Choosing large prefixes provided large number of
  network numbers but small number of host IDs
• Choosing small prefixes provided a small number
  of network numbers but a large number of Host IDs

5
IP address Classes (Continued)

• Designers compromised with providing different
  classes of numbers for each network.
• Depending on the class, determines the size of
  the network number (ID)
• The first four bits of an address determine the
  class.
• This determines how the address is divided into
  prefixes and suffixes.

6
IP address Classes (Continued)

• IP Classes are
• A, B and C (primary classes)
• D (used for multicasting)
• E (used for future use)
• Classes use octet boundaries
• A (the network number is the first octet of the
  address and the host ID is the last three octets)
• B (the network number is the first two octets and
  the host ID is the last two)
• C (the network number is the first three octets
  and the host ID is the last octet of the address)

7
IP address Classes (Continued)

• Classes can be determined from the address itself
  and there for are considered to be self
  identifying
• Most computer hardware can examine bits faster
  than comparing integers.
• The first four bits are extracted and compared to
  determine the class or network the address
  belongs.
• Speeds up routing of IP addresses by sorting
  traffic according to their intended network.

8
IP address Classes (Continued)
Although difficult for us to understand,
computers can distinguish the class of a network
by examining the first four bits of an address
9
Dotted Notation

• Dotted notation is used to display the IP address
  for people.
• Binary numbers are translated into four numbers
  separated by a decimal point.
• Each number is called an octet and each number
  can range from 0 to 255.

10
Classes and Dotted Notation

• Determining the Network Class by examining the
  first octet of an IP Address
• Class A network ID, the first octet will range
  between 0 and 127
• Class B network ID, the first octet will range
  between 128 to 191
• Class C network ID, the first octet will range
  between 192 through 223

11
Classes and Dotted Notation (Continued)
As you can see, each network class can be divided
according To the value of the first octet
12
The Division of IP Addresses

• Class A
• Max number of Network IDs 128
• Max Number of Hosts IDs per network 16777216
• Class B
• Max number of Network IDs 16384
• Max number of Hosts IDs per network 65536
• Class C
• Max number of Network IDs 2097152
• Max number of Host IDs per network 256

13
Authority for IP Addresses

• Internet Assigned Number Authority governs the
  issuing of Network Addresses to ISPs.
• ISPs (Internet Service Providers) provide clients
  with available network IDs.
• Network administrators of the clients will
  determine the assignment of Host IDs on each
  network.

14
Subnets

• Network numbers can be logically divided into sub
  networks.
• This divides the host numbers among different
  subnets and network traffic is routed on each sub
  net.
• This benefits the network by
• Dividing network traffic of IP addresses in a
  particular part of a network according to traffic
  patterns
• Unused Host IDs from a network can be reclaimed
  and redistributed to other clients.

15
Address Masks

• Are used to mask the traffic intended for a
  particular subnet.
• This is accomplished by applying the AND
  function to the Mask and the IP address.
• This will provide the means of abstracting the
  network ID, and the host ID from the IP address.
  
• EXAMPLE subnet mask 255.255.255.0 will pull out
  the network ID for a Class C network
• 255.255.0.0 will pull out the network ID for a
  Class B network.
• Routers can then just compare the network numbers
  in their tables and route them accordingly.

16
CIDR Notation

• Used by people to denote the prefix (network
  number) and the subnet mask.
• Uses the network number followed by the mask
  (denoting the number of bits).
• For example for the class B network
• 130.14.0.0/16
• This shows the network number is 130.14 and the
  mask for this network is 255.255.0.0 (16 bits or
  2 Bytes)
• Makes it easier for people to understand the
  networks and their corresponding masks
• Increasing the number of bits on a network can
  divide classes into many subnets providing
  additional addresses for more clients.

17
Special IP Addresses

• Network Addresses Host 0 is reserved to denote
  the number of the network and is never assigned
  to a computer.
• Broadcast Addresses A host address (ID) that
  contains all 1s is reserved for broadcasts only.
• Limited Broadcasts Used only on the local
  network 255.255.255.255 is reserved when
  computers boot up on a network.

18
Special IP Addresses (Continued)

• This Computer 0.0.0.0 when booting a computer
  may request IP and network information. In this
  case the address of 0.0.0.0 refers to the
  computer booting up.
• Local Loop back
• 127.0.0.1 is used by programmers to test
  client/server applications.
• Both client and server software are run on one
  machine and communicate with each other without
  sending out a packet on the network.

19
Routers and the IP Addressing Principle

• Routers are assigned IP addresses as well
• Routers usually have host ID of 1 for each
  network it is attached.
• This is not the case all of the time.
• In all the router IPs are reserved by the system
  Administrator and are never given to other hosts
  on a network.
• The IP address of a router is often defined as
  the networks Gateway.

20
Multi-Homed Hosts

• A computer that connects to multiple networks is
  called a Multi-Homed computer.
• Often used to increase reliability
• Can also improve performance by avoiding routers
  when sending messages onto a network.