Design an IP address scheme
according to organisational
requirements
What is a protocol?
Why protocols are used in networking
2
Examples of different protocols
3
The ISO/OSI reference model
The seven layers explained
4
6
Introduction to TCP/IP
9
How TCP/IP works
9
What is an IP address?
12
Components of an IP address
12
Classes of IP addresses
13
Subnet masks
15
Binary and decimal conversion
17
Subnetting
19
Routing
20
Routing tables
21
IP Version 6 (IPv6)
23
Summary
24
Check your progress
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What is a protocol?
For communication to occur there has to be some form of common
language and some guidelines that are used to manage the communication
process. With respect to computers and information technology, a protocol
is a standard framework, which dictates how two or more computers
communicate with each other and share information over a particular data
link.
Why protocols are used in networking
Protocols define the rules or standards for communication between network
devices. A printer cannot interpret signals sent by other devices, such as a
workstation or file server, unless there is a common protocol. Protocols
enable data to be sent between two devices in sequence and without errors.
Examples of protocols used on networks include:

Transmission Control Protocol/Internet Protocol (TCP/IP)

Internetwork Packet Exchange/Sequenced Packet Exchange
(IPX/SPX)

NetBIOS (Network Basic Input Output System)

NetBIOS Enhanced User Interface (NetBEUI)

AppleTalk.
Protocols need to be installed and configured on both devices before
communication can take place between those devices, eg a workstation and
a file server.
With respect to networking, the term ‘protocol’ actually refers to a group or
suite of individual protocols that work together. Different tasks are assigned
to protocols within a suite, such as data translation, data handling,
addressing or error checking.
There are many factors that determine which protocol (protocol suite) you
may use on a network. Factors include:
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
the error rate on the data link

whether Internet access is required (this is important as some
protocols are not routable)
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
the network operating system being used

how much network security will be required

the speed requirements of the network.
Examples of different protocols
Below you will find some examples of the different protocols with a brief
explanation for each.
Internet Packet Exchange (IPX) and Sequenced
Packet Exchange (SPX)
This is a suite of protocols, made up of many protocols, not just IPX and
SPX. It was originally developed by Xerox and adopted by Novell in the
1980s.
Novell’s NetWare clients and servers use this suite of protocols. It is
routable, meaning that it can cross many LAN segments. IPX works at the
network layer and is connectionless, that is the protocol does not guarantee
delivery of data.
The IPX protocol is responsible for addressing. SPX is responsible for
ensuring that data is received in sequence and error free.
NetBIOS and NetBEUI
The Network Basic Input Output System (NetBIOS) was originally
developed by IBM and later adopted by Microsoft to be used in small local
area networks.
NetBEUI (NetBIOS Enhanced User Interface) is a fast and efficient protocol
that is still used on small networks.
However, this protocol is not routable, that is it cannot span the Internet.
However, many systems still require the presence of the NetBIOS protocol
services to function correctly. The NetBIOS protocol services can be
implemented on routed networks by ‘riding’ on TCP/IP through the routers,
that is TCP/IP encapsulates NetBIOS.
AppleTalk
This protocol was developed to interconnect Apple Macintosh computers.
This is a routable protocol.
To find out more information on these and other protocols, you can follow
the links in the Research section of this Learning Pack.
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The ISO/OSI reference model
In the early 1980s the International Standards Organisation (ISO) developed
a model or theoretical representation of what happens between two
computers on a network. The model known as the Open Systems
Interconnection (OSI) is the blueprint that has helped networking
specialists to understand and develop computer-to-computer
communications.
The goal of establishing the reference model was to allow different
computers from different manufacturers, running different operating
systems to communicate with each other, so long as each system conformed
to the OSI reference model.
The model has seven layers:
1
application
2
presentation
3
session
4
transport
4
network
6
data link
7
physical.
Each layer of the OSI model has its own function and interacts with the
layers directly above and below it.
Figure 1 below shows information going down the seven layers from one
device across intermediate devices, and then up through the seven layers on
the destination device. These devices can be any type of network equipment
such as networked computers, printers and internetworking devices such as
routers and switches.
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Sending device
Receiving device
Application
Application
\
Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Network
Network
Data Link
Data Link
Data Link
Data Link
Physical
Physical
Physical
Physical
Figure 1: The ISO/OSI reference model showing communication between two
devices
Here is a simple mnemonic to help you remember the order of the seven
layers of the OSI model:
All
Application
7
People
Presentation
6
Seem
Session
5
To
Transport
4
Need
Network
3
Data
Data Link
2
Processing
Physical
1
Figure 2: Remembering the seven layers of the OSI model
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The seven layers explained
Physical layer
The physical layer is the bottom layer of the OSI model. Its function is to
simply:

Transmit bits over the network media. This layer contains the physical
networking media such as cabling, connectors and repeaters.

Specify the mechanical, electrical and functional means of
establishing and maintaining the physical connections. That is, how
the electrical signals are amplified and transmitted over the wire. The
layer sets the data transmission rate and monitors data error rates,
although it does not provide for error correction — which is done at
another level.
The physical layer thus activates and deactivates the physical connection. A
severed wire or a NIC (network interface card) not seated deeply enough are
some of the network problems that can be experienced at the physical layer.
Data link layer
The second layer of the OSI model is the data link layer. Its primary purpose
is to provide a reliable method of transmitting data across the physical
media.
The data link layer divides data it receives from the network layer into
frames that can then be transmitted by the physical layer. A header and
trailer are added to the frames. These allow the destination device to see
when a frame begins or ends on the physical media.
The frames are then transmitted sequentially, and the sender’s data link
layer waits for an acknowledgement from the receiver that data was
received correctly. If the sender does not get this acknowledgment, its data
link layer gives instructions to retransmit the information. The data link
layer is divided into two sub-layers — the Media Access Control (MAC)
sub-layer and the Logical Link Control (LLC) sub-layer.
Media Access Control (MAC)
The MAC sub-layer is responsible for the physical addressing of devices on
the network and how these devices gain access to the network media. The
physical addressing at the data link layer is called a physical address,
because this address is hard-coded into the network interface card by the
manufacturer. The address is also known as the MAC layer address. Each
device has a unique address that provides the necessary information to direct
data to and from devices on the local network.
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Logical Link Control (LLC)
The LLC sub-layer is responsible for flow control and error correction at
this layer and provides two service types:
The unacknowledged connectionless service is unreliable as data is
transferred with no error checking. The Connection-oriented service — is
slower than the connectionless service, as data is checked for errors using
Cyclic Redundancy Checks (CRC). CRC is one method of detecting errors
in transmitted data. Before the data is sent, a CRC number is calculated by
running the data through an algorithm, which produces a unique number.
The data is run through the same algorithm again at the receiving end. If the
numbers are the same, the data was then sent error free. The number
generated by the algorithm is called a checksum.
Flow control is important not only at the LLC sub-layer but also at all layers
of the OSI model. It’s important to make sure that the transmitter doesn’t
flood the receiver with data resulting in buffer overflow and lost data.
Network layer
The network layer is responsible for routing information from the sender to
the receiver. It accepts messages from the transport layer, converts them into
packets and ensures that the packets are directed towards their destination.
The network layer determines the best path that the packets should take
from point A on one network to point B on another network. It does this by
checking to see if the destination device is on another network.
Transport layer
The prime responsibility of the transport layer is to ensure that the data
transferred from point A to point B is reliable, in the correct sequence and
without errors. The transport layer accepts the data from the session layer
and splits it up, if required. It then forwards the data to the network layer
and checks that the data has arrived successfully on the destination device
— this is a connection-oriented service. If an acknowledgement is not
received within a specified period of time, the data is re-sent by the sending
device. Acknowledgements are used to control the flow of data.
Session layer
The session layer allows users to establish a connection — a session. Once
the session has been established the session layer maintains and coordinates the communication. For the user to establish a session, they need
to provide a remote address. The address can be a domain name such as
www.tafensw.edu.au or the NetBIOS name of the computer, for example,
Serv007.
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Presentation layer
The presentation layer is responsible for translating data into a format that
can be understood by each computer. The important task at this layer is code
translation. For example an IBM mainframe may transmit a message in
EBCDIC format to a PC that uses ASCII format. Despite the coding
differences, data can still be displayed on the receiving device, the PC.
ASCII, EBCDIC, BMP, WAV and UNICODE are examples of presentation
layer code translations. (Refer to Terms for definitions of these.) The
presentation layer is also responsible for data encryption and foreign
language translations.
Application layer
The application layer is the seventh and last layer of the model. It is the only
level at which the user has direct contact with the model. This layer starts a
network application, such as transferring files, or provides access to the
Internet. Do not confuse the application layer with software such as word
processing or spreadsheet applications. The application layer makes network
services such as file, print, message, application and database services
available to a computer’s local operating system.
The application layer determines the quality of service at the lower layers.
If a problem occurs at a lower layer, the application layer provides a means
of notifying the user that there is a problem. The notification is usually in
the form of an error message, for example, host not reachable, printing
device not connected, etc.
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Introduction to TCP/IP
TCP/IP stands for Transmission Control Protocol/Internet Protocol. It is
the basic protocol of the Internet. It is a scalable protocol, which can be used
on a small private network, such as your home network or a company’s
private Intranet, or it can be used on a large company network like the one at
Forth Management Associates.
TCP/IP has become the de-facto standard for Internet communications.
There are many reasons for this:

TCP/IP has been accepted as the industry standard protocol.

It is a routable protocol suite.

Almost all computer operating systems support the TCP/IP protocol.

It allows computers using different operating systems to connect to
each other (such as a UNIX computer to a Windows XP computer).

It is an open standard — no company has control over the protocol.
Anyone is allowed to use it and develop applications based on it.

It is a well-designed protocol.
How TCP/IP works
TCP/IP is not just two protocols, but a suite of which includes TCP, IP,
UDP, ARP, ICMP and other sub-protocols. The suite of protocols can be
divided into four layers that roughly correspond to the seven layers of the
OSI model, as shown in Figure 3.
Application
Presentation
Application
Session
Transport
Transport
Network
Internet
Data link
Physical
Network interface
Figure 3: Approximate correspondence of four layers of TCP/IP to OSI model
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TCP/IP is a multiple-layer protocol, which provides an application service
as well as a network service, as can be seen in Figure 4 below.
HTTP
FTP
Application
Sockets
Transportation
Internet
Network
Interface
TCP
ICMP
UDP
IP
ARP
Network Device
Figure 4: TCP/IP application and network services
TCP and IP are the core protocols in the suite, and along with UDP, ICMP,
ARP and other sub-protocols provide a network service.
Internet Protocol (IP)
The Internet Protocol belongs to the Internet Layer of the TCP/IP model. It
provides information on how and where data is to be delivered — a key
feature of Internetworking. For this reason the TCP/IP protocol is able to
span more than one LAN segment, usually through a router.
The IP portion of the data frame is called an IP datagram. The datagram
contains information for routers so that data can be transferred between
individual networks.
IP is a connectionless protocol. This means that it does not guarantee
delivery of data. Higher-level protocols use IP information to ensure that
data packets are delivered to the right address.
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Transmission Control Protocol (TCP)
TCP belongs to the transport layer of the TCP/IP suite. It provides a reliable
data delivery service known as a connection-oriented service — this means
that a connection must be established between two devices before TCP will
transmit data. TCP provides checksum, flow control and sequencing
information, which ensures that the data is reassembled in the correct order.
User Datagram Protocol (UDP)
UDP belongs to the transport layer of the TCP/IP suite. It is a connectionless
service — it does not guarantee that the packets will be received in the
correct order and provides no error checking or sequencing. UDP is used
when data needs to be transferred quickly, for example, in live audio or
video transmissions over the Internet.
Internet Control Message Protocol (ICMP)
ICMP belongs to the Internet layer of the TCP/IP suite. It is responsible for
notifying the sending device of a problem with transmission, for example,
when packets are not delivered. It provides a message to the sending device,
such as ‘Host unreachable’ (how many times have you seen this?). ICMP is
used by diagnostic utilities, such as PING.
Address Resolution Protocol (ARP)
ARP also belongs to the Internet layer of the TCP/IP suite. ARP is used to
determine an unknown MAC address of a remote device to which a packet
is to be sent. The header of an IP packet contains the MAC and IP address
of the source and the MAC and IP address of the destination. The resulting
IP/MAC address information is held on the sending machine in an ARP
table.
Application service
The TCP/IP suite also provides an application service with the protocols:
 Hypertext Transfer Protocol (HTTP)
 Telnet
 Hypertext Transfer Protocol security
(HTTPs)
 File Transfer Protocol
(FTP)
 Simple Network Management Protocol
(SNMP)
 Simple Mail Transfer
Protocol (SMTP)
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What is an IP address?
Every device on a network (printer, workstation, server, etc) requires a
unique identifier. If all the devices are on the same local area network, then
only a physical (MAC) address is required. This is the same as saying that
all we need to uniquely identify any house in the same street is to have its
house number. However, if the destination device is on a different network
then a logical address is also required. This is the same as saying that all we
need to uniquely identify any house in NSW is to have its house number, its
street name and its town name. The IP address is the logical address that
allows data to be sent to devices on different networks. Logical addresses
must conform to the standards and rules of the protocol, thus IP addresses
are assigned according to specific rules and standards and are configured by
the network administrator.
Components of an IP address
An IP address is a 32-bit binary number, for example:
11001011 00111100 00000001 00000010
For ease of use, this is normally represented in a dotted decimal format, eg:
203.60.1.2.
Each 8-bit octet is represented by a whole number between 0 and 255. Each
IP address consists of two fields:

a net ID field that is the logical network address of the device

a host ID field, which is the logical device’s address that uniquely
identifies each device on the network.
Together, the net ID and the host ID provide each device on a network with
a unique IP address.
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Classes of IP addresses
There are five classes of IP addresses, however only three classes are
commonly used. Table 1 below shows the commonly used TCP/IP classes.
Table 1: Commonly used TCP/IP classes if IP addresses
Class
First Octet
Number of Networks
Number of addresses per
network
A
1 – 126
126
16, 777, 214
B
128 – 191
16, 384
65, 534
C
192 – 223
2, 097, 154
254
Note: Class D and E are not available for standard network addressing.
You can identify the class of an IP address by examining the first octet.
All nodes in a Class A network share the first octet of their IP address. Class
A addresses range between 1 and 126. An example of a Class A address is
125.10.15.1. The net ID portion of the IP address is 125 and the host ID
portion of the IP address is 10.15.1.
All nodes in a Class B network share the first two octets of their IP address.
Class B addresses range between 128 and 191. An example of a Class B
address is 158.10.15.1. The net ID portion of the IP address is 158.10 and
the host ID portion of the IP address is 15.1.
All nodes in a Class C network share the first three octets of their IP
address. Class C addresses range between 192 and 223. An example of a
Class C address is 200.10.15.1. The net ID portion of the IP address is
200.10.15 and the host ID portion of the IP address is 1.
Class A networks have a
binary address starting with
00 000000 as the first octet:
Class B networks have a
binary address starting with
10 000000 as the first octet;
Binary
Decimal
Binary
Decimal
00 000000
0
10 000000
128
00 000001
1
10 000001
129
00 000010
2
10 000010
130
~~
~~
~~
~~
00 111110
126
10 111110
190
00 111111
127
10 111111
191
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Class C networks have a
binary address starting with
11 000000 as the first octet.
Binary
Decimal
11 000000
192
11 000001
193
11 000010
194
~~
~~
11111110
222
11 111111
223
As there are only 126 Class A
networks available on the Internet,
most Class A networks have been
reserved by large corporations or
governments. Some IP addresses
have been reserved for network
functions such as broadcasts and
cannot be assigned to devices.
As you know, all rules have
exceptions and this also applies to IP
addressing. The following section
discusses special IP addresses.
Special IP addresses
Here are some of the restrictions you should keep in mind — you will need
to remember them!
First octet value of 127
Any address with a first octet value of 127 is a loopback address, which is
used for diagnostics and testing. A message sent to an IP address with the
first octet of 127 is returned to the sender. The IP address 127.0.0.1 is
known as the loopback address and is used for this purpose. Therefore, 127
cannot be used as a net ID, although it is technically a Class A address.
255 in an octet
255 in an octet is designated as a broadcast. A message sent to
255.255.255.255 is broadcast to every host on the local network. For
example, a message sent to 158.8.255.255 is broadcasted to every host on
network 158.8.
Addresses for private Local Area Networks (LANs)
There are three groups of IP addresses to choose from if you wish to create a
private LAN (for example, an Intranet for a company, for use at home and
not on the Internet):
10.0.0.0 to 10.255.255.255
172.16.0.0 to 172.31.255.255
192.168.0.0 to 192.168.255.255
The first octet cannot have a value above 223. Those addresses are reserved
for multicast and experimental purposes.
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Subnet masks
Besides an IP address, every computer on a network must be configured
with a subnet mask. The subnet mask allows routing devices to separate the
IP address into its net ID and host ID portions.
Network management is made easier if a network is broken into smaller
segments. However, a business is allocated a single IP address that covers
its net ID address and a range of host ID addresses. By using some of the
host ID bits as segment addresses, segmentation can occur and network
management made easier.
The subnet mask identifies whether a computer is on the same local network
or on another network that needs to be contacted through a router. Subnet
masks make it easier and faster to identify the net ID portion of the IP
address. It allows TCP/IP to determine if network traffic destined for a
given IP address should be transmitted on the local network, or whether it
should be routed to a remote network.
A subnet mask should be the same for all computers and other network
devices on the same network segment.
The subnet mask is a 32-bit binary number, broken into four 8-bit octets.
A common subnet mask is 255.255.255.0. This particular subnet mask
specifies that TCP/IP will use the first three octets of an IP address as the
network id and the last octet as the host ID.
The subnet mask is dependent on the class of IP addresses in use on the
network. The following subnet masks are used for the following Classes of
IP addresses:
Class A: 255.0.0.0
Class B: 255.255.0.0
Class C 255.255.255.0
Note: If subnet masks are incorrectly configured, routing errors will occur.
How do you obtain an IP address?
IP addresses can be requested from the Internet Corporation for Assigned
Names and Numbers (ICANN) — a non-profit organisation set up to
maintain and assign IP addresses. Here in Australia, various agents such as
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Internet Service Providers (ISPs) can apply to the ICANN for IP addresses
on your behalf or lease some of their ‘reserved’ IP addresses to you.
An organisation does not normally obtain an IP address for each staff
member. The range of IP addresses a company will lease will depend on the
number of servers in the organisation that will require Internet access such
as a web or remote access servers. Most organisations usually lease a small
number of IP addresses. Internally, organisations use addresses from the
private address range to allocate to staff members.
Real IP addresses are allocated to the web and proxy servers, as well as
other devices such as routers that communicate with other devices on the
Internet. These devices have a legitimate IP address, however, the
workstations and other devices on the company’s network use addresses
from the private ranges.
A NAT (Network Address Translation) server can be used to hide the IP
addresses assigned to devices on the network from any public network, such
as the Internet. When a node’s transmission reaches the IP gateway, the
gateway assigns the client’s transmission with a valid IP address. In this
way, the company’s internal IP addresses are protected and network
administrators have more flexibility in assigning addresses.
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Binary and decimal conversion
Computers store information in binary form, that is, in 0s or 1s. Binary uses
the Base2 counting system. To create subnets and work out the decimal
equivalents of the binary bit pattens, it’s useful to learn how to convert
decimal numbers into binary and vice versa (without a calculator!)
To convert a number into binary or decimal it is best to use this table.
0/1
0/1
0/1
0/1
0/1
0/1
0/1
0/1
First row: the 0/1 refers to the value of a bit, that is, zero or one
27
26
25
24
23
22
21
20
Second row: represents the binary system; increases in value to the power of
2 (as opposed to the decimal system, which increases to the power of 10)
128
64
32
16
8
4
2
1
Third row: the decimal values of the second row.
Rules for converting
Using the table above, you will need to apply the following rules:

multiply the bit by its positional decimal equivalent

add the value of the decimal equivalents of all the bits to determine
the total decimal value of the binary number.
For example
1
1
0
0
1
0
1
1
X
X
X
X
X
X
X
X
128
64
32
16
8
4
2
1
128
64
0
0
8
0
2
1
Decimal value = 203
0
0
1
1
1
1
0
0
0
0
0
0
0
1
0
0
0
0
1
0
Decimal value = 60
0
0
Decimal value = 1
0
0
Decimal value = 2
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So, the IP address 203.60.1.2
has the corresponding binary
values:
203
60
1
2
11001011
00111100
00000001
00000010
In binary within a computer, this would be stored as:
11001011001111000000000100000010
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Subnetting
A large network can be divided into smaller or multiple networks by
subdividing a single class of IP addresses. Network Administrators can use
one class of addresses for several network segments. A subnetted address
includes the network, subnet, and host information.
Say your organisation is assigned a Class B network ID of 152.77.0.0. The
standard subnet mask would be 255.255.0.0. The number of valid IP
addresses would range from 152.77.0.1 to 152.77.255.254. To divide this
range of IP addresses into 6 networks you would need to apply the formula:
2n –2 where n = to the number of bits.
In the above example, the standard subnet mask is 255.255.0.0.which when
converted to binary is: 11111111.11111111.00000000.00000000.
By borrowing 3 bits, the new subnet mask becomes:
1111111.11111111.11100000.00000000 — which converts to the decimal
format: 255.255.224.0. In this example, a 3-bit subnet mask is used. There
are 6 (23 –2) subnets available with this subnet mask. Remember that
subnets with all 0s and all 1s are not allowed — these are reserved for
specifying the local network. The valid range of IP addresses for the five
subnets is shown in Table 2.
Table 2: Valid range of IP addresses for five subnets
Subnet bits
Network number
Node Addresses
001
152.77.32.0
152.77.32.1 to 152.77.63.254
010
152.77.64.0
152.77.64.1 to 152.77.95.254
011
152.77.96.0
152.77.96.1 to 152.77.127.254
100
152.77.128.0
152.77.128.1 to 152.77.159.254
101
152.77.160.0
152.77.160.1 to 152.77.192.254
110
152.77.192.0
152.77.192.1 to 152.77.223.254
The combination of an address’s network and subnet information becomes
an extended network prefix. The extended network prefix, enables a device
to determine the subnet to which the address belongs. Subnet masks allow
you to sub-allocate network addresses. Subnetting, is a complex procedure,
which you can learn more about with further reading and after completing
this unit.
Websites providing further exercises and examples of subnetting can be
found in the Research section of this Learning Pack.
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Routing
A router is a device that determines the next network point to which a
packet should be forwarded toward its destination. The router is connected
to at least two networks and decides which way to send each information
packet based on its current understanding of the state of the networks it is
connected to.
Routers create and maintain a table of the available routes and their
conditions and use this information along with the distance to determine the
best route for a given packet. Typically, a packet may travel through a
number of network points with routers, before arriving at its destination.
Routing is a function associated with the network layer (layer 3) in the
standard model of network programming, the OSI model.
In most cases, a router is located at any gateway (where one network meets
another). In Figure 5 below two networks are connected by a router with IP
address 192.168.1.1 and 203.60.1.4, subnet mask 255.255.255.0. The router
acts as a gateway and will handle all the incoming and outgoing network
traffic, and as can be seen in Figure 5, the router will handle the traffic
between these two networks, which will also apply to the way the router
connects to the Internet.
203.60.1.1
203.60.1.2
203.60.1.3
203.60.1.4
192.168.1.1
192.168.1.2
192.168.1.3
192.168.1.4
Figure 5: Two networks connected by a router
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Routing tables
TCP/IP hosts use a routing table to maintain knowledge about other IP
networks and IP hosts. As you now know, using an IP address and a subnet
mask identifies networks and hosts.
In addition, routing tables are important because they give needed
information to each local host regarding how to communicate with remote
networks and hosts.
For each computer on an IP network, you can maintain a routing table with
an entry for every other computer or network that communicates with the
local computer. In general, this is not practical, and a default gateway (IP
router) is used instead.
When a computer prepares to send an IP datagram, it inserts its own source
IP address and the destination IP address of the recipient into the IP header.
The computer then examines the destination IP address, compares it to a
locally maintained IP routing table, and takes appropriate action based on
what it finds. The computer does one of three things, it:

passes the datagram up to a protocol layer above IP on the local host.

forwards the datagram through one of its attached network
interfaces.

discards the datagram.
IP searches the routing table for the route that is the closest match to the
destination IP address. The most specific to the least specific route is
searched for in the following order:

a route that matches the destination IP address (host route)

a route that matches the network ID of the destination IP address
(network route)

the default route.
Figure 6 shows a default routing table that can be accessed through the
command prompt ‘route print’. It shows the current IP address and subnet
mask of the local interface card and where it should forward its network
traffic, in this case 0.0.0.0 of network destination will have to forward to
192.168.0.1. This means that all traffic will be handled by the 192.168.0.1
(which is default gateway/router), and the router will decide where to
forward the traffic.
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Figure 6: A default routing table
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IP Version 6 (IPv6)
For over 20 years now, the IT industry has been using IPv4. As you have
read, with IPv4, IP addresses are unique — each computer or device on the
network is allocated an IP address and a subnet mask. By the late 1980s it
was realised that the world would run out of IP addresses and work began
on the IP Next Generation (IPng) project: IPv6.
IPv4 uses a 32-bit address space, which permits an absolute maximum of 232
(4,294,967,296) hosts to connect to the Internet at any given time. Today,
not only do businesses, government departments and schools have Internet
access, but also most homes have at least one computer that accesses the
Internet.
IPv6 addresses are four times as long as IPv4 addresses and at 128 bits
provide an absolute maximum of 2128 individual hosts. This is roughly 340
billion billion billion different hosts! (Would you like to check this
calculation!)
IPv6 is now included as part of IP support in many products, from 3Com
and Hitachi, and including the major computer operating systems. There are
no plans (at this stage anyway) for a cutover date when IPv6 would be
turned on and IPv4 turned off.
One of the strategies chosen for the upgrade is to deploy the IPv6 protocol
stack in parallel with IPv4. This means that hosts that upgrade to IPv6 will
continue to exist as IPv4 hosts at the same time.
An experimental IPv6 backbone or 6bone, has been set up to handle IPv6
Internet traffic in parallel with the regular Internet. These devices will
continue to have 32-bit IPv4 addresses but will add 128 bit IPv6 addresses.
We suggest you do some follow up reading on IPv6 at:
http://www.ipv6.org/
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Summary
In this topic the term protocol and its definition were introduced with
respect to information technology.
A protocol is a standard or rule that dictates how two or more computers
communicate with each other and share information. There are many
network protocols in use today, such as IPX/SPX, AppleTalk, NetBEUI and
TCP/IP. However, TCP/IP has become the de-facto standard of the Internet.
It is the protocol of choice for most networks, whether they are connected to
the Internet or not. It enables different computers running different
operating systems on different networks to communicate with each other
and share information.
The TCP/IP protocol is a suite of protocols or protocol stack, made up of
core protocols such as TCP, IP and sub-protocols such as UDP, ARP, ICMP
to name a few.
Every device on a network is logically configured with a unique IP address
and subnet mask which determines the network the device is located on.
Each IP address and subnet mask is a 32-bit binary number normally
represented in dotted decimal format.
IP addressing and subnet masks provide useful information to network
devices such as servers, other workstations and routers. This information
enables data to be routed from one network to another.
Transition strategies have been in place since 1999 to migrate from IPv4 to
IPv6 in the near future.
Check your progress
Now you should try and do the Practice activities in this topic. If you’ve
already tried them, have another go and see if you can improve your
responses.
When you feel ready, try the ‘Check your understanding’ activity in the
Preview section of this topic. This will help you decide if you’re ready for
assessment.
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