8/2/2019 Internet Protocol & IP address
1/14
Internet Protocol & IPaddressComputer Networking Research Project
2012
Batch 03
Java Robotics and Intelligent Systems Research Center
3/19/2012
8/2/2019 Internet Protocol & IP address
2/14
ACKNOWLEDGEMENT
We owe a great many thanks to a great many people who helped and
Supported us during the completing of this project.
My deepest thanks to
MR. Nirodha Rupasingha
for guiding and correcting our work
with attention and care.
We express my thanks to MR. Bhathiya Thisera
Managing Director of Java Robotics and Intelligent Systems
Research Center
for extending his support.
Our deep sense of gratitude to MR. R.K. Bandara (Lecturer of Network
Engineering)
For his support and guidance.
We would also thank our Institution, without whom this project would
have been a distant reality. We also extend our heartfelt thanks to our families
and well wishers.
*****************
8/2/2019 Internet Protocol & IP address
3/14
What is an IP address?
Every machine on a network has a unique identifier. Just as you would address a letterto send in the mail, computers use the unique identifier to send data to specific
computers on a network. Most networks today, including all computers on the Internet,
use the TCP/IP protocol as the standard for how to communicate on the network. In the
TCP/IP protocol, the unique
identifier for a computer is called its
IP address.
There are two standards for IP
addresses: IP Version 4 (IPv4) and
IP Version 6 (IPv6). All computers
with IP addresses have an IPv4
address, and many are starting to
use the new IPv6 address system
as well. Here's what these two address types mean:
IPv4 uses 32 binary bits to create a single unique address on the network. An IPv4address is expressed by four numbers separated by dots. Each number is the decimal
(base-10) representation for an eight-digit binary (base-2) number, also called an octet.
For example: 216.27.61.137
IPv6 uses 128 binary bits to create a single unique address on the network. An IPv6
address is expressed by eight groups of hexadecimal (base-16) numbers separated by
colons, as in 2001:cdba:0000:0000:0000:0000:3257:9652. Groups of numbers that
contain all zeros are often omitted to save space, leaving a colon separator to mark thegap (as in 2001:cdba::3257:9652).
At the dawn of IPv4 addressing, the Internet was not the large commercial sensation it
is today, and most networks were private and closed off from other networks around the
world. When the Internet exploded, having only 32 bits to identify a unique Internet
8/2/2019 Internet Protocol & IP address
4/14
address caused people to panic that we'd run out of IP addresses. Under IPv4, there
are 232 possible combinations, which offers just under 4.3 billion unique addresses.
IPv6 raised that to a panic-relieving 2128 possible addresses. Later, we'll take a closer
look at how to understand your computer's IPv4 or IPv6 addresses.
How does your computer get its IP address? An IP address can be either dynamic or
static. A static address is one that you configure yourself by editing your computer's
network settings. This type of address is rare, and it can create network issues if you
use it without a good understanding of TCP/IP. Dynamic addresses are the most
common. They're assigned by the Dynamic Host Configuration Protocol (DHCP), a
service running on the network. DHCP typically runs on network hardware such
as routers or dedicated DHCP servers.
Dynamic IP addresses are issued using a leasing system, meaning that the IP address
is only active for a limited time. If the lease expires, the computer will automatically
request a new lease. Sometimes, this means the computer will get a new IP address,
too, especially if the computer was unplugged from the network between leases. This
process is usually transparent to the user unless the computer warns about an IP
address conflict on the network (two computers with the same IP address). An address
conflict is rare, and today's technology typically fixes the problem automatically.
Next, let's take a closer look at the important parts of an IP address and the special
roles of certain addresses.
8/2/2019 Internet Protocol & IP address
5/14
IP Classes
Earlier, you read that IPv4 addresses represent four eight-digit binary numbers. That
means that each number could be 00000000 to 11111111 in binary, or 0 to 255 in
decimal (base-10). In other words, 0.0.0.0 to 255.255.255.255. However, somenumbers in that range are reserved for specific purposes on TCP/IP networks. These
reservations are recognized by the authority on TCP/IP addressing, the Internet
Assigned Numbers Authority (IANA). Four specific reservations include the following:
0.0.0.0 -- This represents the default
network, which is the abstract concept of
just being connected to a TCP/IP
network. 255.255.255.255 -- This address is
reserved for network broadcasts, or
messages that should go to all
computers on the network.
127.0.0.1 -- This is called the loopback
address, meaning your computer's way
of identifying itself, whether or not it has
an assigned IP address.
169.254.0.1 to 169.254.255.254 -- This
is the Automatic Private IP Addressing
(APIPA) range of addresses assigned
automatically when a computer's
unsuccessful getting an address from a
DHCP server.
The other IP address reservations are for
subnet classes. A subnet is a smaller network of computers connected to a larger
network through a router. The subnet can have its own address system so computerson the same subnet can communicate quickly without sending data across the larger
network. A router on a TCP/IP network, including the Internet, is configured to recognize
one or more subnets and route network traffic appropriately. The following are the IP
addresses reserved for subnets:
HOW DHCP ASSIGNS ADDRESSES
When you add a computer to a network, thatcomputer uses a four-step process to get an
IP address from DHCP:
Discover -- The computer sends out abroadcast message on the network,hoping to discover a DHCP serviceprovider.
Offer -- Each DHCP provider hears themessage, recognizes the uniquehardware address of the computer, andsends a message back offering itsservices to that computer.
Request -- The computer selects a DHCPprovider from its offerings and then sendsa request to that provider asking for an IPaddress assignment.
Acknowledge -- The targeted DHCPprovider acknowledges the request andissues an IP address to the computer thatdoesn't match any other IP addressescurrently active on the network.
8/2/2019 Internet Protocol & IP address
6/14
10.0.0.0 to 10.255.255.255 -- This falls within the Class A address range of 1.0.0.0 to
127.0.0.0, in which the first bit is 0.
172.16.0.0 to 172.31.255.255 -- This falls within the Class B address range of 128.0.0.0
to 191.255.0.0, in which the first two bits are 10.
192.168.0.0 to 192.168.255.255 -- This falls within the Class C range of 192.0.0.0
through 223.255.255.0, in which the first three bits are 110.
Multicast (formerly called Class D) -- The first four bits in the address are 1110, with
addresses ranging from 224.0.0.0 to 239.255.255.255.
Reserved for future/experimental use (formerly called Class E) -- addresses 240.0.0.0
to 254.255.255.254.
The first three (within Classes A, B and C) are those most used in creating subnets.
Later, we'll see how a subnet uses these addresses. The IANA has outlined specific
uses for multicast addresses within Internet Engineering Task Force (IETF)
documentRFC 5771. However, it hasn't designated a purpose or future plan for Class E
addresses since it reserved the block in its 1989 document RFC 1112. Before IPv6, the
Internet was filled with debate about whether the IANA should release Class E for
general use.
Next, let's see how subnets work and find out who has those non-reserved IP
addresses out on the Internet.
http://tools.ietf.org/html/rfc5771http://tools.ietf.org/html/rfc5771http://tools.ietf.org/html/rfc5771http://tools.ietf.org/html/rfc57718/2/2019 Internet Protocol & IP address
7/14
Internet Addresses and Subnets
The following is an example of a subnet IP address you might have on your computer at home if
you're using a router (wireless or wired) between your ISP connection and your computer:
IP address: 192.168.1.102
Subnet mask: 255.255.255.0
Twenty-four bits (three octets) reserved for network identity
Eight bits (one octet) reserved for nodes
Subnet identity based on subnet mask (first address): 192.168.1.0
The reserved broadcast address for the subnet (last address): 192.168.1.255
Example addresses on the same network: 192.168.1.1, 192.168.1.103
Example addresses not on the same network: 192.168.2.1, 192.168.2.103
Besides reserving IP addresses, the IANA is also responsible for assigning blocks of IP
addresses to certain entities, usually commercial or government organizations. Your Internet
service provider (ISP) may be one of these entities, or it may be part of a larger block under the
control of one of those entities. In order for you to connect to the Internet, your ISP will assign
you one of these addresses.
8/2/2019 Internet Protocol & IP address
8/14
IANA-reserved private IPv4 network ranges
Start EndNo. of
addresses
24-bit block (/8 prefix, 1 A) 10.0.0.0 10.255.255.255 16777216
20-bit block (/12 prefix, 16 B) 172.16.0.0 172.31.255.255 1048576
16-bit block (/16 prefix, 256 C) 192.168.0.0 192.168.255.255 65536
If you only connect one computer to the Internet, that computer can use the address from your
ISP. Many homes today, though, use routers to share a single Internet connection between
multiple computers. Wireless routers have become especially popular in recent years, avoiding
the need to run network cables between rooms.
If you use a router to share an Internet connection, the router gets the IP address issued directly
from the ISP. Then, it creates and manages a subnet for all the computers connected to that
router. If your computer's address falls into one of the reserved subnet ranges listed earlier,
you're going through a router rather than connecting directly to the Internet.
IP addresses on a subnet have two parts: network and node. The network part identifies the
subnet itself. The node, also called the host, is an individual piece of computer equipment
connected to the network and requiring a unique address. Each computer knows how to
separate the two parts of the IP address by using a subnet mask. A subnet mask looks
somewhat like an IP address, but it's actually just a filter used to determine which part of an IPaddress designates the network and node.
A subnet mask consists of a series of 1 bits followed by a series of 0 bits. The 1 bits indicate
those that should mask the network bits in the IP address, revealing only those that identify a
unique node on that network. In the IPv4 standard, the most commonly used subnet masks
have complete octets of 1s and 0s as follows:
8/2/2019 Internet Protocol & IP address
9/14
255.0.0.0.0 = 11111111.00000000.00000000.00000000 = eight bits for networks, 24 bits for
nodes
255.255.0.0 = 11111111.11111111.00000000.00000000 = 16 bits for networks, 16 bits for
nodes
255.255.255.0 = 11111111. 11111111.11111111.00000000 = 24 bits for networks, eight bits for
nodes
People who set up large networks determine what subnet mask works best based on the
number of desired subnets or nodes. For more subnets, use more bits for the network; for more
nodes per subnet, use more bits for the nodes. This may mean using non-standard mask
values. For instance, if you want to use 10 bits for networks and 22 for nodes, your subnet mask
value would require using 11000000 in the second octet, resulting in a subnet mask value of
255.192.0.0.
Another important thing to note about IP addresses in a subnet is that the first and last
addresses are reserved. The first address identifies the subnet itself, and the last address
identifies the broadcast address for systems on that subnet.
IPv4 address exhaustion
IPv4 address exhaustion is the decreasing supply of unallocated Internet Protocol Version
4 (IPv4) addresses available at the Internet Assigned Numbers Authority (IANA) and
the regional Internet registries (RIRs) for assignment to end users and local Internet registries,
such as Internet service providers. IANA's primary address pool was exhausted on February 3,
2011 when the last 5 blocks were allocated to the 5 RIRs. APNIC was the first RIR to exhaust
its regional pool on 15 April 2011, except for a small amount of address space reserved for the
transition to IPv6, intended to be allocated in a restricted process
8/2/2019 Internet Protocol & IP address
10/14
IPv6 addresses
Decomposition of an IPv6 address from hexadecimal representation to its binary value.
The rapid exhaustion of IPv4 address space, despite conservation techniques, prompted
the Internet Engineering Task Force (IETF) to explore new technologies to expand the Internet's
addressing capability. The permanent solution was deemed to be a redesign of the Internet
Protocol itself. This next generation of the Internet Protocol, intended to replace IPv4 on the
Internet, was eventually named Internet Protocol Version 6(IPv6) in 1995 The address size was
increased from 32 to 128 bits or 16 octets. This, even with a generous assignment of network
blocks, is deemed sufficient for the foreseeable future. Mathematically, the new address space
provides the potential for a maximum of 2128, or about3.4031038 unique addresses.
The new design is not intended to provide a sufficient quantity of addresses on its own, but
rather to allow efficient aggregation of subnet routing prefixes to occur at routing nodes. As a
result, routing table sizes are smaller, and the smallest possible individual allocation is a subnet
for 264hosts, which is the square of the size of the entire IPv4 Internet. At these levels, actual
address utilization rates will be small on any IPv6 network segment. The new design also
provides the opportunity to separate the addressing infrastructure of a network segment that
is the local administration of the segment's available space from the addressing prefix used
to route external traffic for a network. IPv6 has facilities that automatically change the routing
prefix of entire networks, should the global connectivity or the routing policy change, without
requiring internal redesign or renumbering.
The large number of IPv6 addresses allows large blocks to be assigned for specific purposes
and, where appropriate, to be aggregated for efficient routing. With a large address space, there
is not the need to have complex address conservation methods as used in Classless Inter-
Domain Routing (CIDR).
http://en.wikipedia.org/wiki/File:Ipv6_address.svghttp://en.wikipedia.org/wiki/File:Ipv6_address.svghttp://en.wikipedia.org/wiki/File:Ipv6_address.svghttp://en.wikipedia.org/wiki/File:Ipv6_address.svg8/2/2019 Internet Protocol & IP address
11/14
Many modern desktop and enterprise server operating systems include native support for the
IPv6 protocol, but it is not yet widely deployed in other devices, such as home networking
routers, voice over IP (VoIP) and multimedia equipment, and network peripherals.
IPv6 private addresses
Just as IPv4 reserves addresses for private or internal networks, blocks of addresses are set
aside in IPv6 for private addresses. In IPv6, these are referred to as unique local
addresses (ULA). RFC 4193 sets aside the routing prefix fc00::/7 for this block which is divided
into two /8 blocks with different implied policies The addresses include a 40-bit pseudorandom
number that minimizes the risk of address collisions if sites merge or packets are misrouted.
Early designs used a different block for this purpose (fec0::), dubbed site-local
addresses. However, the definition of what constituted sitesremained unclear and the poorly
defined addressing policy created ambiguities for routing. This address range specification was
abandoned and must not be used in new systems.
Addresses starting with fe80:, called link-local addresses, are assigned to interfaces for
communication on the link only. The addresses are automatically generated by the operating
system for each network interface. This provides instant and automatic network connectivity for
any IPv6 host and means that if several hosts connect to a common hub or switch, they have a
communication path via their link-local IPv6 address. This feature is used in the lower layers of
IPv6 network administration (e.g. Neighbor Discovery Protocol).
None of the private address prefixes may be routed on the public Internet.
IP Subnetworks
IP networks may be divided into subnetworks in both IPv4 and IPv6. For this purpose, an IP
address is logically recognized as consisting of two parts: the network prefixand the host
identifier, orinterface identifier(IPv6). The subnet mask or the CIDR prefix determines how the
IP address is divided into network and host parts.
The term subnet maskis only used within IPv4. Both IP versions however use the Classless
Inter-Domain Routing (CIDR) concept and notation. In this, the IP address is followed by a slash
and the number (in decimal) of bits used for the network part, also called the routing prefix. For
example, an IPv4 address and its subnet mask may be 192.0.2.1 and 255.255.255.0,
respectively. The CIDR notation for the same IP address and subnet is 192.0.2.1/24, because
the first 24 bits of the IP address indicate the network and subnet.
8/2/2019 Internet Protocol & IP address
12/14
IP address assignment
Internet Protocol addresses are assigned to a host either anew at the time of booting, or
permanently by fixed configuration of its hardware or software. Persistent configuration is alsoknown as using astatic IP address. In contrast, in situations when the computer's IP address is
assigned newly each time, this is known as using a dynamic IP address.
Methods
Static IP addresses are manually assigned to a computer by an administrator. The exact
procedure varies according to platform. This contrasts with dynamic IP addresses, which are
assigned either by the computer interface or host software itself, as in Zeroconf, or assigned by
a server using Dynamic Host Configuration Protocol (DHCP). Even though IP addresses
assigned using DHCP may stay the same for long periods of time, they can generally change. In
some cases, a network administrator may implement dynamically assigned static IP addresses.
In this case, a DHCP server is used, but it is specifically configured to always assign the same
IP address to a particular computer. This allows static IP addresses to be configured centrally,
without having to specifically configure each computer on the network in a manual procedure.
In the absence or failure of static or stateful (DHCP) address configurations, an operating
system may assign an IP address to a network interface using state-less auto-configuration
methods, such asZeroconf.
Uses of dynamic addressing
Dynamic IP addresses are most frequently assigned on LANs and broadband networksby Dynamic Host Configuration Protocol (DHCP) servers. They are used because it avoids the
administrative burden of assigning specific static addresses to each device on a network. It also
allows many devices to share limited address space on a network if only some of them will be
online at a particular time. In most current desktop operating systems, dynamic IP configuration
is enabled by default so that a user does not need to manually enter any settings to connect to a
network with a DHCP server. DHCP is not the only technology used to assign dynamic IP
addresses. Dialup and some broadband networks use dynamic address features of the Point-to-
Point Protocol.
Sticky dynamic IP address
A sticky dynamic IP addressis an informal term used by cable and DSL Internet access
subscribers to describe a dynamically assigned IP address which seldom changes. The
addresses are usually assigned with DHCP. Since the modems are usually powered on for
extended periods of time, the address leases are usually set to long periods and simply
renewed. If a modem is turned off and powered up again before the next expiration of the
address lease, it will most likely receive the same IP address.
8/2/2019 Internet Protocol & IP address
13/14
Address autoconfiguration
RFC 3330 defines an address block, 169.254.0.0/16, for the special use in link-local addressing
for IPv4 networks. In IPv6, every interface, whether using static or dynamic addressassignments, also receives a local-link address automatically in the block fe80::/10.
These addresses are only valid on the link, such as a local network segment or point-to-point
connection, that a host is connected to. These addresses are not routable and like private
addresses cannot be the source or destination of packets traversing the Internet.
When the link-local IPv4 address block was reserved, no standards existed for mechanisms of
address autoconfiguration. Filling the void, Microsoft created an implementation that is called
Automatic Private IP Addressing (APIPA). Due to Microsoft's market power, APIPA has been
deployed on millions of machines and has, thus, become a de facto standard in the industry.
Many years later, the IETF defined a formal standard for this functionality, RFC 3927,entitled Dynamic Configuration of IPv4 Link-Local Addresses.
Uses of static addressing
Some infrastructure situations have to use static addressing, such as when finding the Domain
Name System (DNS) host that will translate domain names to IP addresses. Static addresses
are also convenient, but not absolutely necessary, to locate servers inside an enterprise. An
address obtained from a DNS server comes with a time to live, or caching time, after which it
should be looked up to confirm that it has not changed. Even static IP addresses do change as
a result of network administration (RFC 2072)
Public addresses
A public IP addressin common parlance is synonymous with a, globally routable unicast IP
address.
Both IPv4 and IPv6 define address ranges that are reserved for private networks and link-local
addressing. The term public IP address often used excludes these types of addresses.
8/2/2019 Internet Protocol & IP address
14/14
Modifications to IP addressing
IP blocking and firewalls
Firewalls perform Internet Protocol blocking to protect networks from unauthorized access. Theyare common on today's Internet. They control access to networks based on the IP address of a
client computer. Whether using a blacklist or a whitelist, the IP address that is blocked is the
perceived IP address of the client, meaning that if the client is using a proxy server or network
address translation, blocking one IP address may block many individual computers.
IP address translation
Multiple client devices can appear to share IP addresses: either because they are part of
a shared hosting web server environment or because an IPv4 network address translator (NAT)
or proxy serveracts as an intermediary agent on behalf of its customers, in which case the real
originating IP addresses might be hidden from the server receiving a request. A common
practice is to have a NAT hide a large number of IP addresses in a private network. Only the
"outside" interface(s) of the NAT need to have Internet-routable addresses.[11]
Most commonly, the NAT device maps TCP or UDP port numbers on the outside to individual
private addresses on the inside. Just as a telephone number may have site-specific extensions,
the port numbers are site-specific extensions to an IP address.
In small home networks, NAT functions usually take place in a residential gateway device,
typically one marketed as a "router". In this scenario, the computers connected to the router
would have 'private' IP addresses and the router would have a 'public' address to communicate
with the Internet. This type of router allows several computers to share one public IP address.
Diagnostic toolsComputer operating systems provide various diagnostic tools to examine their network interface
and address configuration. Windows provides the command-line
interface tools ipconfig and netsh and users of Unix-like systems can
use ifconfig, netstat, route, lanstat, ifstat, or iproute2 utilities to accomplish the task.
http://en.wikipedia.org/wiki/IP_address#cite_note-10http://en.wikipedia.org/wiki/IP_address#cite_note-10http://en.wikipedia.org/wiki/IP_address#cite_note-10http://en.wikipedia.org/wiki/IP_address#cite_note-10