Transcript Layering and the TCP/IP protocol Suite

Layering and the TCP/IP
protocol Suite
 The TCP/IP Protocol only contains 5
Layers in its networking Model
 The Layers Are
1.
2.
3.
4.
5.
Physical -> 1 in OSI
Network Interface -> 2 in OSI
Internet -> 3 in OSI (loosely)
Transport -> 4 in OSI
Application -> 5, 6, 7 in the OSI Model
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 Sender’s IP address and the
Receivers IP address are sent in each
packet over the internet.
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.
1. Each computer can have a Unique ID
2. Each suffix can be granted locally without global
coordination.
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 ID’s
 Choosing small prefixes provided a small
number of network numbers but a large
number of Host IDs
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.
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)
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.
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
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.
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
Classes and Dotted Notation
(Continued)
As you can see, each network class can be divided according
To the value of the first octet
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
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 ID’s.
 Network administrators of the clients will
determine the assignment of Host IDs on
each network.
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.
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.
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.
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.
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.
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.
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.