Networking
Why use a Network?
Quite simply explained we use networks for communication
between computers, sharing of data and peripherals. In the
business world we use networks for ease of administration
and to cut costs.
Sharing data example imagine an office with 5 secretaries
working on 5 different computers, one requires a file from
another computer in a non networked office this file would
have to be written to a portable media then loaded onto the
computer. In a networked office the file could be accessed via
the network from a shared folder.
Sharing peripherals example the same office with 5 secretaries
working on 5 different computers, in order to print their work
each computer would need to have a printer attached. In a
networked office you could have one shared printer, cutting
costs.

What do you need?
A common language or protocol (TCP/IP IPX/SPX, APPLE
TALK) is a convention or standard that controls or enables the
connection, communication, and data transfer between two
computing endpoints.
A common language or protocol (TCP/IP IPX/SPX, APPLE
TALK) is a convention or standard that controls or enables the
connection, communication, and data transfer between two
computing endpoints.
Cabling BNC,Cat5, fibre optic
Hardware NIC(Network Interface Card), router, switch, hub,
modem wireless access point.
Network Service (DNS, WINS, DHCP).

Network Hardware

Network Interface Card
A network card, network adapter, network interface card or
NIC is a piece of computer hardware designed to allow
computers to communicate over a computer network. It has a
MAC address. Every network card has a unique 48-bit serial
number called a MAC address, which is written to ROM
carried on the card. Every computer on a network must have a
card with a unique MAC address. The IEEE is responsible for
assigning MAC addresses to the vendors of network interface
cards. No two cards ever manufactured should share the same
address.

Hubs
An Ethernet hub or concentrator is a device for connecting
multiple twisted pair or fibre optic Ethernet devices together,
making them act as a single segment. It works at the physical
layer of the OSI model, repeating the signal received at one
port out each of the other ports (but not the original one). The
device is thus a form of multiport repeater. Ethernet hubs are
also responsible for forwarding a jam signal to all ports if it
detects a collision. Hubs also often come with a BNC and/or
AUI connector to allow connection to legacy 10BASE2 or
10BASE5 network segments. The availability of low-priced
Ethernet switches has largely rendered hubs obsolete but they
are still seen in older installations and more specialist
applications.

Switches
A network switch or switch for short is a networking device
that performs transparent bridging (connection of multiple
network segments with forwarding based on MAC addresses)
at full wire speed in hardware. As a frame comes into a
switch, the switch saves the originating MAC address and the
originating (hardware) port in the switch’s MAC address
table. This table often uses content-addressable memory, so it
is sometimes called the “CAM table”. The switch then
selectively transmits the frame from specific ports based on the
frame’s destination MAC address and previous entries in the
MAC address table. If the destination MAC address is
unknown, for instance, a broadcast address or (for simpler
switches) a multicast address, the switch simply transmits the
frame out of all of the connected interfaces except the
incoming port. If the destination MAC address is known, the
frame is forwarded only to the corresponding port in the MAC
address table.

Hubs VS Switches
A hub, or repeater, is a fairly unsophisticated broadcast device.
Any packet entering any port is broadcast out on every port
and thus hubs do not manage any of the traffic that comes
through their ports. Since every packet is constantly being sent
out through every port, this results in packet collisions, which
greatly impedes the smooth flow of traffic. A switch isolates
ports, meaning that every received packet is sent out only to
the port on which the target may be found (assuming the
proper port can be found; if it is not, then the switch will
broadcast the packet to all ports except the port the request
originated from). Since the switch intelligently sends packets
only where they need to go the performance of the network
can be greatly increased.

Routers

A router is a computer networking device that forwards data
packets across a network toward their destinations, through a
process known as routing. A router acts as a junction between
two or more networks to transfer data packets among them. A
router is different from a switch. A switch connects devices to
form a Local area network (LAN).
One easy illustration for the different functions of routers and
switches is to think of switches as local streets, and the router
as the junctions with the street signs. Each house on the local
street has an address within a range on the street. In the same
way, a switch connects various devices each with their own IP
address(es) on a LAN. Routers connect networks together the
way that on-ramps or major junctions connect streets to both
main roads and motorways. The street signs at the junctions
the (routing table) show which way the packets need to flow.

Wireless

Wireless Access Point (WAP) A wireless access point (AP)
connects a group of wireless stations to an adjacent wired
local area network (LAN). An access point is similar to an
Ethernet hub, but instead of relaying LAN data only to other
LAN stations, an access point can relay wireless data to all
other compatible wireless devices as well as to a single
(usually) connected LAN device, in most cases an Ethernet
hub or switch, allowing wireless devices to communicate with
any other device on the LAN.
Wireless Routers A wireless router integrates a wireless
access point with an Ethernet switch and an Ethernet router.
The integrated switch connects the integrated access point and
the integrated Ethernet router internally, and allows for
external wired Ethernet LAN devices to be connected as well
as a (usually) single WAN device such as a cable modem or
DSL modem. A wireless router advantageously allows all
three devices (mainly the access point and router) to be
configured through one central configuration utility, usually
through an integrated web server. However one disadvantage
is that one may not decouple the access point so that it may be
used elsewhere.

Cables

Cable Terminology

10BASE2 (also known as cheapernet or thinnet) is a variant of
Ethernet that uses thin coaxial cable. The 10 comes from the
maximum transmission speed of 10 Mbit/s (millions of bits
per second). The BASE stands for baseband signaling, and the
2 represents a rounded up shorthand for the maximum
segment length of 185 metres (607 feet).
10BASE5 (also known as thicknet) is the original “full spec”
variant of Ethernet cable. The 10 refers to its transmission
speed of 10 Mbit/s. The BASE is short for baseband
signalling as opposed to broadband, and the 5 stands for the
maximum segment length of 500 metres.
10BASE-T is an implementation of Ethernet which allows
stations to be attached via twisted pair cable. The name
10BASE-T is derived from several aspects of the physical
medium. The 10 refers to the transmission speed of 10 Mbit/s.
The BASE is short for baseband.The T comes from twisted
pair, which is the type of cable that is used
100BASE-T is any of several Fast Ethernet 100 Mbit/s
CSMA/CD standards for twisted pair cables, including:
100BASE-TX (100 Mbit/s over two-pair Cat5 or better cable).
The segment length for a 100BASE-T cable is limited to 100
metres

Coaxial

Coaxial cable is an electrical cable consisting of a round
conducting wire, surrounded by an insulating spacer,
surrounded by a cylindrical conducting sheath, usually
surrounded by a final insulating layer. It is used as a high-
frequency transmission line to carry a high-frequency or
broadband signal.
BNC connectors were commonly used on 10base2 thin
Ethernet networks, both on cable interconnections and
network cards, though these have largely been replaced by
newer Ethernet devices whose wiring does not use coaxial
cable.

CAT 5

Category 5 cable, commonly known as Cat 5, is an unshielded
twisted pair cable type designed for high signal integrity.
Category 5 has been superseded by the Category 5e
specification. This type of cable is often used in structured
cabling for computer networks such as Gigabit Ethernet,
although they are also used to carry many other signals such
as basic voice services, token ring.
Category 5 cable included four twisted pairs in a single cable
jacket. It was most commonly used for 100 Mbit/s networks,
such as 100BASE-TX Ethernet
Cat5 cable uses an RJ-45 (Registered Jack-45) connector at
each end of the cable with a fixed wiring scheme. The ends are
then crimped on to the cable

Wiring Scheme

Patch or straight through cables have Wiring scheme 1 at both
ends of the cable and are used to connect computers to
network wall sockets or hubs.
Crossover cables have Wiring scheme 1 at one end of the
cable and Wiring scheme 2 at the other. These cables are used
to connect network hardware together e.g. PC to PC, hub to
hub.

Protocols
A protocol (TCP/IP IPX/SPX, APPLE TALK) is a
convention or standard that controls or enables the connection,
communication, and data transfer between two computing
endpoints. Sending and receiving systems need to use the
same protocol unless a gateway service sits between networks
and translates from one to the other.
Most protocols specify one or more of the following
properties:
Detection of the underlying physical connection (wired or
wireless), or the existence of the other endpoint or node
Handshaking
Negotiation of various connection characteristics
How to start and end a message
How to format a message
What to do with corrupted or improperly formatted
messages (error correction)
How to detect unexpected loss of the connection, and what
to do next
Termination of the session or connection.

NetBIOS
NetBIOS is an acronym for Network Basic Input/Output
System. The NetBIOS API allows applications on separate
computers to communicate over a local area network.
NetBIOS must be enabled for Windows File and Print
Sharing to work.
NetBIOS provides three distinct services:
Name service for name registration and resolution
Session service for connection-oriented communication
Datagram distribution service for connectionless
communication.
Name service In order to start Sessions or distribute
Datagrams, an application must register its NetBIOS name
using the Name service. NetBIOS names are 16 bytes in
length
Session service Session mode lets two computers establish a
connection for a “conversation,” allows larger messages to be
handled, and provides error detection and recovery. In NBT,
the session service runs on TCP port 139.
Datagram distribution service Datagram mode is
“connectionless”. Since each message is sent independently,
they must be smaller; the application becomes responsible for
error detection and recovery. In NBT, the datagram service
runs on UDP port 138.

IPX/SPX (NWLINK)
Internetwork Packet Exchange (IPX) is the OSI-model
Network layer protocol in the IPX/SPX protocol stack. The
IPX/SPX protocol stack is supported by Novell’s NetWare
network operating system. Because of Netware’s popularity
through the late 1980s into the mid 1990s, IPX became a
popular internetworking protocol. Novell derived IPX from
Xerox Network Services’ IDP protocol. IPX usage is in
general decline as the boom of the Internet has made TCP/IP
nearly universal. Computers and networks can run multiple
network protocols, so almost all IPX sites will be running
TCP/IP as well to allow for Internet connectivity. It is also
now possible to run Novell products without IPX, as they
have supported both IPX and TCP/IP since NetWare reached
version 5.
Sequenced Packet Exchange (SPX) is a transport layer
protocol (layer 4 of the OSI Model) used in Novell Netware
networks. The SPX layer sits on top of the IPX layer (layer 3
– the network layer) and provides connection-oriented services
between two nodes on the network. SPX is used primarily by
client/server applications.
NWLink is a IPX/SPX-compatible protocol developed by
Microsoft and used in its Windows NT product line.NWLink
is Microsoft’s version of Novell’s IPX/SPX Protocol. The
Microsoft version of NWLink includes the same level of
functionality as the Novell Protocol. NWLink includes a tool
for resolving NetBIOS names.NWLink packages data to be
compatible with client/server services on NetWare Networks.
However, NWLink does not provide access to NetWare File
and Print Services. To access the File and Print Services the
Client Service for NetWare needs to be installed.

AppleTalk
AppleTalk is a suite of protocols developed by Apple
Computer for computer networking. It was included in the
original Macintosh (1984) and is now used less by Apple in
favour of TCP/IP networking.
AppleTalk contains two protocols aimed at making the system
completely self-configuring. The AppleTalk address resolution
protocol (AARP) allowed AppleTalk hosts to automatically
generate their own network addresses, and the Name Binding
Protocol (NBP) was essentially a dynamic DNS system which
mapped network addresses to user-readable names.
For interoperability Microsoft maintains the file services for
Macintosh and the print services for Macintosh.

TCP/IP
The Internet protocol suite is the set of communications
protocols that implement the protocol stack on which the
Internet and most commercial networks run. It is sometimes
called the TCP/IP protocol suite, after the two most important
protocols in it: the Transmission Control Protocol (TCP) and
the Internet Protocol (IP), which were also the first two
defined.The Internet protocol suite like many protocol suites
can be viewed as a set of layers, each layer solves a set of
problems involving the transmission of data, and provides a
well-defined service to the upper layer protocols based on
using services from some lower layers. Upper layers are
logically closer to the user and deal with more abstract data,
relying on lower layer protocols to translate data into forms
that can eventually be physically transmitted.The OSI model
describes a fixed, seven layer stack for networking protocols.
Comparisons between the OSI model and TCP/IP can give
further insight into the significance of the components of the
IP suite, but can also cause confusion, as TCP/IP consists of
only 4 layers.
The four layers in the DoD model, from bottom to top, are:
The Network Access Layer is responsible for delivering
data over the particular hardware media in use. Different
protocols are selected from this layer, depending on the
type of physical network.
The Internet Layer is responsible for delivering data across
a series of different physical networks that interconnect a
source and destination machine. Routing protocols are most
closely associated with this layer, as is the IP Protocol, the
Internet’s fundamental protocol.
The Host-to-Host Layer handles connection rendezvous,
flow control, retransmission of lost data, and other generic
data flow management. The mutually exclusive TCP and
UDP protocols are this layer’s most important members.
The Process Layer contains protocols that implement user-
level functions, such as mail delivery, file transfer and
remote login.

Network Services
DNS (Domain Naming System)
The Domain Name System (DNS) stores and associates many
types of information with domain names, but most
importantly, it translates domain names (computer hostnames)
to IP addresses. It also lists mail exchange servers accepting e-
mail for each domain. In providing a worldwide keyword-
based redirection service, DNS is an essential component of
contemporary Internet use.
The DNS pre-eminently makes it possible to attach easy-to-
remember domain names (such as “es-net.co.uk”) to hard-to-
remember IP addresses (such as 270.146.131.206). People
take advantage of this when they recite URLs and e-mail
addresses.

WINS (Windows Internet Naming
Service)
Windows Internet Naming Service (WINS) is Microsoft’s
implementation of NetBIOS Name Server (NBNS) on
Windows, a name server and service for NetBIOS computer
names. Effectively, it is to NetBIOS names what DNS is to
domain names – a central mapping of host names to network
addresses. However, the mappings have always been
dynamically updated (e.g. at workstation boot) so that when a
client needs to contact another computer on the network it can
get its up-to-date DHCP allocated address. Networks normally
have more than one WINS server and each WINS server
should be in push pull replication; the favoured replication
model is the hub and spoke, thus the WINS design is not
central but distributed. Each WINS server holds a full copy of
every other related WINS system’s records. There is no
hierarchy in WINS (unlike DNS), but like DNS its database
can be queried for the address to contact rather than
broadcasting a request for which address to contact. The
system therefore reduces broadcast traffic on the network,
however replication traffic can add to WAN / LAN traffic.

DHCP (Dynamic Host
Configuration Protocol)
The Dynamic Host Configuration Protocol (DHCP) automates
the assignment of IP addresses, subnet masks, default routers,
and other IP parameters. The assignment usually occurs when
the DHCP configured machine boots up or regains
connectivity to the network. The DHCP client sends out a
query requesting a response from a DHCP server on the
locally attached network. The DHCP server then replies to the
client with its assigned IP address, subnet mask, DNS server
and default gateway information.The assignment of the IP
address usually expires after a predetermined period of time, at
which point the DHCP client and server renegotiate a new IP
address from the server’s predefined pool of addresses.
Configuring firewall rules to accommodate access from
machines who receive their IP addresses via DHCP is
therefore more difficult because the remote IP address will
vary from time to time. Administrators must usually allow
access to the entire remote DHCP subnet for a particular TCP/
UDP port. Most home routers and firewalls are configured in
the factory to be DHCP servers for a home network. ISPs
(Internet Service Providers) generally use DHCP to assign
clients individual IP addresses.DHCP is a broadcast-based
protocol. As with other types of broadcast traffic, it does not
cross a router.

APIPA (Automatic Private IP
Addressing)
If computers are unable to pick an address up from a DHCP
server they use Automatic Private IP Addressing (APIPA).
This means the computer will assign itself a random address
between 169.254.0.1 – 169.254.254.254/16, allowing it to
communicate with other clients who are also using APIPA.
Automatic Private IP Addressing (APIPA), this allows
unknowledgeable users to connect computers, networked
printers, and other items together and expect them to work.
Without Zeroconf or something similar, a knowledgeable user
must either set up special servers, like DHCP and DNS, or set
up each computer by hand.

Networks
A Local Area Network (LAN) is a computer network
covering a small local area, like a home, office, or small group
of buildings such as a home, office, or college. Current LANs
are most likely to be based on switched Ethernet or Wi-Fi
technology running at 10, 100 or 1,000 Mbit/s.The defining
characteristics of LANs in contrast to WANs (wide area
networks) are: their much higher data rates; smaller geographic
range; and that they do not require leased telecommunication
lines.
A Personal Area Network (PAN) is a computer network used
for communication among computer devices (including
telephones and personal digital assistants) close to one person.
The reach of a PAN is typically a few metres and may use
Bluetooth, wireless or USB for connection.
A Wide Area Network (WAN) is a computer network
covering a wide geographical area, involving a vast array of
computers. This is different from personal area networks
(PANs), metropolitan area networks (MANs) or local area
networks (LANs) that are usually limited to a room, building
or campus. The most well-known example of a WAN is the
Internet. WANs are used to connect local area networks
(LANs) together, so that users and computers in one location
can communicate with users and computers in other locations.

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Server Roles
The term server refers to a machine that is providing a service
for other machines, e.g. A computer which shares files on the
network would be classed as a file server. For example, A
Domain Controller is classed as a server because it is
providing a service for the rest of the clients on the network.
Windows 2003 can take several different server roles. These
are as follows:

File Server
A File Server stores files and folders that are used by other
machines on the network. It can hold applications, text
documents, or a user’s My Documents Folder. For security,
many shared folders are housed on file servers. A distributed
file system is housed on more than one file server for the sake
of fault-tolerance and ease of access.
A Windows XP Professional machine may act as a limited
File Server.
A Windows Server 2003 Computer can also act as a file
server for different operating systems, e.g. Apple Macintosh.

Print Server
A Print Server is a computer that has a printer attached to it
and shares the printer for use on the network.
A Windows XP Professional Machine can be a reasonably
capable Print Server.

Application Server
Besides being a Domain Controller, Windows Server 2003
can also be a host to many different services e.g. as a Database
Server and a Terminal Server.

Some Common Microsoft
Servers:
Microsoft Exchange allows you to setup an e-mail server and
also allows you setup a messaging and collaboration system
for your company’s network.
Microsoft SQL Server enables you to setup up powerful
database servers for your company’s network.
Microsoft ISA Server allows you to setup an Internet
Gateway/Proxy Server for your company’s network.
These applications require Windows Server 2003. Their
integration with Active Directory allows for tighter security
and easier administration.
A Database Server holds a database! This is not just a list of
information. It is structured, and dynamic. It needs to be
managed, updated, extended and secure, while at the same time
being accessible to users. A dedicated server is required for
this.
Remote Administration enables an administrator to manage a
server from almost any workstation on the network using
Terminal Services. Terminal Services lets workstations use
powerful applications housed at the server as if they were
installed at that workstation.

Web Servers
A Web Server hosts and manages websites for the Internet or
an intranet. Because of the need to manage heavy and burst-
mode traffic while maintaining security, a dedicated server is
recommended.
Windows 2003 can function as a web server using the Internet
Information Services (IIS) service
Windows XP Professional ships with a limited version of IIS
which allows a workstation to host a single website.

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