Internet Protocols And Infra
Structure Essay, Research Paper
Anything reticulated or decussated at equal distances, with
interstices between the intersections.
- A Dictionary
of the English
SECTION : 1
1.1 WHAT IS A
A) What is a
A network is
simply a collection of machines connected in some way that allows
them to communicate with each other and share information. To do this
the machines have to be connected in some way that allows
communication, and have an agreed upon a language to talk when they
Components of a
network might include individual hosts, some form of communications
hardware, a network protocol and a collection of network services.
A network is a
collection of individual machines sometimes referred to as hosts.
Each host (computer) must have some unique identifier that allows
other hosts to talk to it.
OF A NETWORK
In order to
communicate the parties must speak the same language. Languages on
computer networks are referred to as network protocols. A network
protocol is simply a set of rules and formats that govern how
information is sent and in what format it is sent. Some of the
different network protocols used today include TCP/IP (Internet and
UNIX favourite), IPX (Novell), Appletalk (MAC), DECnet and various
quickly becoming the networking protocol and is the one I concentrate
on in this subject.
To be of use to
users the network will provide various services including file, print
and device sharing, electronic mail etc.
1.3 TYPES OF
? LAN (local
All the hosts in
the network are directly linked to each other. For example most of
the computers on the ground floor of the IT building at CQU are part
of a LAN.
? WAN (wide area
Much larger than
a LAN and all machines are not directly connected. WANs will
generally have a lower throughput than a LAN. All of the LANs on the
CQU campus connect and form a WAN.
1.4 SOME MORE
Like any field
of computing, networking has its own terminology. This section
provides definitions for some of the terms you’ll come across.
? Packets and
protocols transmit information as packets. Information being sent
across the network is divided into small (hundreds of bytes usually)
chunks of data, called packets. The networking software at the
sending end will break the outgoing data into packets. When the
packets arrive at their destination the networking software on the
receiving machine will put them all back together.
In some cases
not all the packets will arrive at the destination using the same
route. The packets may also arrive out of order, packet 50 might
arrive before packet 49. The networking software handles all of this.
packets are often referred to as datagrams. Ethernet, on type of
networking hardware, refers to packets as frames
The art of
deciding which route data from one machine takes to get to another.
In many cases their are multiple different possible routes that can
be taken and the routing software must decide which to take.
performing the routing for a network, a router is typically a device
that connects multiple networks together. (The terms router, gateway
and bridge are sometimes used interchangeably).
A device that
connects two totally different types of network. For example you
might have a gateway machine sitting between an IPX network and a
TCP/IP network. The gateway allows the two different networks to talk
to each other by converting the protocols they are using.
and connection oriented
transport protocols will often be described as being connection
oriented or connectionless. A connection oriented protocol acts like
a telephone connection. The sender contacts the receiver and asks are
you ready to talk? If the receiver is ready a connection is formed
and communication can take place. If the receiver isn’t ready or
isn’t there, no communication. Once the connection is made all the
information sent down the connection will arrive at the other end.
protocol is like the postal service in that all information is sent
in individual messages (called packets or datagrams). The individual
datagrams have no knowledge or interconnection. Often they are
delivered using totally different routes.
? Unreliable and
When a protocol
is called unreliable this does not imply that a large percentage of
the information it sends is not arriving at the other end. Instead it
means that the protocol does not check whether or not the information
it just sent actually arrives at the other end.
On the other
hand a reliable network protocol will send a piece of information and
will wait to make sure that the information arrived at the other end
(this is achieved by the receiver sending an acknowledgment back to
the sender saying “yep received that piece, send me another”).
1.5 TYPES OF
There is a wide
range of different networking hardware that can be used. It’s
beyond the scope of this subject to examine each of these. However
the following readings from the Internet have been located.
Control Protocol works with IP to provide reliable delivery. It
provides a means to ensure that the various datagrams making up a
message are reassembled in the correct order at their final
destination and that any missing datagrams are re-sent until they are
purpose of TCP is to avoid the loss, damage, duplication, delay, or
misordering of packets that can occur under IP. When IP forwards
datagrams, individual datagrams may or may not arrive, and they
probably will not arrive in the order in which they were sent. TCP
adds the reliability that IP lacks. Also, security provisions such as
limiting user access to certain machines can be implemented through
reliability by using checksums (error detection codes) on the data,
sequence numbers in the TCP header, positive acknowledgment of data
received, and retransmission of unacknowledged data.
Most versions of
the UNIX operating system comes with in-built support for networking.
The default network protocol that UNIX systems are typically designed
to talk is TCP/IP. TCP/IP is also known as the Internet Protocol
TCP/IP is the
protocol used by the Internet, a network of networks spread
throughout the world connecting over two million machines with over
twenty million users. It is not necessary to be connected to the
Internet to use TCP/IP. However being able to connect to the Internet
is one of the advantages of using TCP/IP.
2.2 ISOC AND
of Internet standards is not controlled by any one commercial
organisation, even though it can be influenced by them. Instead the
development of the Internet is performed by a number of different
non-profit organisations including :
? The Internet
non-governmental International organisation for global cooperation
and coordination for the Internet and its internetworking
technologies and applications.
? The Internet
Architecture Board (IAB) is a body of the Internet Society
responsible for overall architectural considerations in the Internet.
It also serves to adjudicate disputes in the standards process.
? The Internet
Engineering Task Force
Engineering Task Force (IETF) is the protocol engineering and
development arm of the Internet. The IETF is a large open
international community of network designers, operators, vendors, and
researchers concerned with the evolution of the Internet architecture
and the smooth operation of the Internet. It is open to any
interested individual. (taken from http://www.ietf.org/)
? The Internet
Engineering And Planning Group
readings are included to provide more information on these
Internet organisations :
? ISOC The
Internet Society SLOW SITE : http://www.isoc.org/
? IEPG the
Internet engineering and planning group : http://www.iepg.org/
A) Request for
used on the Internet are specified in documents called Request for
Comments (RFCs). (Not all RFCs are standards). Someone proposing a
new Internet standard will write and submit an RFC. The RFC will be
distributed to the Internet community who will comment on it and may
suggest changes. The standard proposed by the RFC will be adopted as
a standard if the community is happy with it.
assigned numbers, Figure 1 includes RFC numbers that correspond to
the different protocols. If you have access to the Internet you can
anonymously ftp RFCs from a number of well-known sites (including
RFCs can and
often are very technical and hard to understand unless you are
familiar with the area (the RFC for ftp is about 80 pages long).
links might prove useful:
? Australian FTP
archive of RFCs : ftp://archie.au/rfc/
? Ohio State
University’s RFC archive :
? a UK based RFC
archive with a search engine :
A) The protocols
TCP/IP is an
example of a layered communications suite. The advantage of this
layered approach is that the protocols at higher levels can safely
assume that the lower level protocols will carry out their
For example TCP
does not need to know anything about the hardware being used because
it is hidden by the layers below it. Figure 1 displays the four
different layers of TCP/IP and where some of the many protocols that
make up the Internet protocol suite fit within those layers.
TCP and IP are
two of the many protocols that make up the suite of Internet
protocols. Figure 1 lists some of the others. Some of these protocols
will be discussed in detail in the next chapter.
The inclusion of
these pages is intended to provide you with other readings on TCP/IP
if you are interested.
B) IPv6 and Ipng
IPv6 is the
formal name of a protocol developed by the IETF’s IPng (Next
Generation Internet Protocol) working group. IPng is designed to be
an evolutionary step from IPv4, the current version of IP being
In this subject
we will not be examining IPv6 in any great detail but you should be
aware of its existence. The following readings are included for
? The Official
IPng Page SLOW SITE :
? Another IPv6
? An Overview of
IPng : http://playground.sun.com/pub/ipng/html/INET-IPng-Paper.html
= FIGURE 1 =
The four layers
3.1 MOVING DOWN
A) Moving Down
Each of the four
layers of TCP/IP perform a different role. In order to perform this
role each layer adds a small piece of control information, called a
header, onto the front of each packet of information sent.
When a packet is
sent it moves down the four layers. As it passes through each layer
that layer appends its header information onto the front. The
information is then sent. When it is received at the other end it
moves up through the layers. As it moves up each layer strips off its
header information and uses it to perform some task.
provides a representation of this.
= FIGURE 2 =
access layer is the bottom layer of the TCP/IP protocol stack. This
layer provides the ability to transmit an IP datagram from one host
to another host on the same physical network. To do this the network
access layer must be aware of the details of the network hardware on
which it is running. This also means that for each different type of
networking hardware there must be a different network access layer.
This is the
layer that is responsible for translating an Internet address into a
hardware address. The process will be discussed further in a later
3.3 THE INTERNET
layer consists of two protocols IP, the Internet protocol and ICMP,
the Internet control message protocol. IP is central to the TCP/IP
protocol suite. All information being sent via TCP/IP must use IP. IP
performs the following tasks
? defines the
size and the format of the datagram to be transmitted,
The size of the
datagram depends on the type of network hardware being used.
Different types of hardware can handle different size datagrams. IP
will create datagrams using the MTU, maximum transmission unit for
? defines the
Internet addressing scheme,
The header for
every IP datagram will contain two IP addresses. The source IP
address and the destination.
? moves data
between the network access layer and the transport layer
datagrams for remote machine,
? fragments and
ICMP performs a
number of control, error reporting and information functions .
* example of
network access layer packet being given to IP
layer’s two major protocols are ;
Control Protocol, TCP
connection oriented protocol.
? User Datagram
Both UDP and TCP
support the concept of ports. On any networked computer it is likely
that there will be many different programs all using the network at
the same time. This means the computer is receiving multiple
datagrams for a number of different programs.
How does it know
which datagram belongs to which program?
When a program
wishes to send or receive information over a TCP/IP network it must
connect to a port. Any information that is destined for the program
must be labeled with its port number. If a program wishes to send any
information it must know the port number of the receiver.
implemented by the transport protocol layer. The header for both TCP
and UDP contain two 16 bit numbers that are used for the source port
and the destination port. The transport layer will examine the port
numbers and deliver the information to the correct program.
3.5 UDP and TCP
A) UDP and TCP
information with a minimum of protocol overhead and is generally used
when the amount of data being transmitted is small. TCP uses
considerably more overhead (a TCP header consists of 6 32-bit words
while a UDP header has 2).
overhead is used to ensure its reliability. Each packet of
information that is sent using TCP contains a checksum. The receiver
of the information will examine the checksum to determine whether or
not the data has arrived unchanged. If the data is unchanged the
receiver will then send an acknowledgment back to the sender (”it’s
okay I received that information”). If the sender does not the
acknowledgment back within a certain time the sender will resend the
The most common
alternative is UDP (”user datagram protocol”) which is designed
for applications where you don’t need to put sequences of datagrams
together. It fits into the system much like TCP. There is a UDP
header. The network software puts the UDP header on the front of your
data, just as it would put a TCP header on the front of your data.
Then UDP sends the data to IP, which adds the IP header, putting
UDP’s protocol number in the protocol field instead of TCP’s
protocol number. However UDP doesn’t do as much as TCP does. It
doesn’t split data into multiple datagrams. It doesn’t keep track
of what it has sent so it can resend if necessary. About all that UDP
provides is port numbers, so that several programs can use UDP at
once. UDP port numbers are used just like TCP port numbers. There are
well-known port numbers for servers that use UDP. Note that the UDP
header is shorter than a TCP header. It still has source and
destination port numbers, and a checksum, but that’s about it. No
sequence number, since it is not needed. UDP is used by the protocols
that handle name lookups (see IEN 116, RFC 882, and RFC 883), and a
number of similar protocols.
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