White Paper
Basic Networking
Introduction
As multi-computer households become more common, many home users are discovering the benefits of
networking their computers. For these households, and for small offices and home offices, being able to
share resources becomes a real need. Unless you employ an IT professional, you may be wondering how
you can best share files, printers, and an Internet connection. The solution is a basic network that you can
easily and affordably implement.
A network, or local area network (LAN), is an assortment of interconnected computing devices that allows a
community of people to share information and resources. Networks can range in size from two computers
sharing a printer to thousands of computers worldwide that are exchanging information (these are wide area
networks, or WANs).
With your computers networked, you’ll be able to do the following:
•
•
•
•
•
Share an Internet connection
Access E-mail
Share a single printer
Share files, such as music, pictures, or documents
Play games with multiple users at different computers, or play online games without monopolizing
the Internet
This paper aims to explain the basics of networking. A network is made up of a physical topology, cables
(media), hardware (components), a media access method (i.e., Ethernet, LocalTalk, or FDDI), and network
services (i.e., file or print sharing).
Network Topologies
A topology is the physical layout of a network. The topology of your network will depend on the media
access method it uses and the type of cables that are installed. Large networks that involve a wide physical
area may use a combination of topologies. However, a small network need only employ one topology. There
are three common types of network topologies: star, bus, and ring (or star-wired ring).
Star Topology
In this topology, each device (computer, printer, server, peripheral, etc.) has a dedicated set of wires
connecting it to a central network hub or switch. (See Figure 1) The failure of one connection usually will not
affect the other connections in the network. Also, all network traffic passes through the hub, so the hub may
act as a central point for gathering statistics and isolating problems in the network. This topology is common
for Ethernet, FDDI, and ATM networks.
Bus Topology
In a bus topology, each device is connected directly to a common cable, and most often serves as a
backbone for a network. (See Figure 2) This wiring scheme is unstructured, without a central point, and can
be difficult to troubleshoot. No hub is required for this topology, which can help to keep the network costs
lower.
1
5/21/03
Asanté Technologies, Inc.
White Paper
Ring Topology and Star-Wired Ring Topology
A ring topology is made up of a logically closed loop of cable. Data packets travel around the ring from one
network device to the next. (See Figure 3 below.) Each device acts a repeater (it regenerates the signal) to
send the packets to the next device. If one device fails, the whole network is affected, making this topology
difficult to implement and maintain. Because of this disadvantage, another topology was created: the starwired ring topology. (See Figure 4 below.) It has essentially replaced the ring topology. Networks using the
star-wired ring topology have devices radiating from a hub, which acts as a logical ring with data packets
traveling port to port in sequence. The benefit is that, like a star topology, if one device fails, the network can
continue to operate.
Cabling
Cable is what connects all your network devices together, transmitting data between them. Larger networks
that use multiple topologies may also use more than one type of cabling, whereas a small home network
requires just a single type of cable. The type of cable you use depends on the network’s topology, size, and
network technology (i.e., Ethernet, FDDI, or LocalTalk).
Twisted-Pair Cable
This cable consists of two insulated wires that are twisted around each other and covered with a plastic
casing. Shielded Twisted Pair (STP) cable includes a layer of shielding that is placed between the wire and
the casing. STP is less affected by noise interference than Unshielded Twisted Pair (UTP) and can transmit
data farther, but is more difficult to install, and more expensive as well. UTP cabling is a popular choice for
most LANs. UTP cable is grouped into categories, numbered 1 through 6. The higher the category rating,
the tighter the wires are twisted together, allowing for faster data transmission with less interference on the
wire.
2
5/21/03
Asanté Technologies, Inc.
White Paper
Fiber-Optic Cable
Fiber-optic cable is made of flexible glass and plastic. Data is transmitted via photons, or light. Fiber-optic
cable is more resistant to electronic interference than other media types, and is therefore able to transmit
data signals farther than coaxial or twisted pair cabling. It is often installed as a backbone in large facilities
and between buildings. However, the cost of installing and maintaining fiber-optic cable makes it a poor
choice for small home networks.
Coaxial Cable
This type of cable has a copper conductor surrounded by insulation, a secondary conductor (the two
conductors on the same axis explains the name coaxial), and a plastic outside covering. Because of the two
layers of shielding, it is very resistant to interference, and can be used to transmit data long distances.
Coaxial cable is a good choice for running the lengths of buildings as a bus topology on the network
backbone. LANs use two sizes of coaxial cable, commonly referred to as thick and thin coaxial cable. Thick
coaxial, or thicknet, cable adheres to the 10Base5 Ethernet specification, with a maximum segment length of
500 meters. Thin coaxial, or thinnet, cable uses the 10Base2 specification, with a maximum segment length
of 200 meters. Thick coaxial cable can extend farther than thin, but thin coaxial cable is more flexible, less
expensive, and easier to install, making it the more popular of the two.
Network Components
The components of your network include both the hardware and the software. Whether your network uses
some or all of the following components will depend on its size and the needs of the users.
Computers: The most obvious part of a network is the computer. It is what connects people to the network,
allowing users to share resources and information.
Network Adapters: The network adapter is the physical link between the computer and the network cable.
Typically, an adapter is a card that slides into an expansion slot, an external device, or is built into the
device, and provides a connector for attaching network cable.
File Server: A file server is a high-speed, large memory computer that acts as storage for data and
application programs for the network. A small home network is not likely to require file servers. A file server
can also act as a print server or mail server. A print server spools print jobs and stores them until the printer
is available, thereby freeing the user’s computer to continue with other tasks. A mail server stores e-mails
until the user retrieves the messages.
Network Operating System (NOS): A NOS is a software program that resides on the server. It supervises
how the network operates by defining who can use the network, and how information and resources are
shared among users. A small home network is not likely to require a NOS. The NOS depends on, and runs
on top of, the server’s operating system. Common NOSs include Microsoft Windows NT, Novell NetWare,
AppleShare, and Unix.
3
5/21/03
Asanté Technologies, Inc.
White Paper
Ethernet/Fast Ethernet Switches: Sometimes called routers, or Internet routers. Essentially, an Ethernet
switch is a multi-port bridge that provides a dedicated 10 or 100 Mbps Ethernet connection between ports.
With switches, multiple 10/100Mbps connections can be simultaneously established, increasing the
aggregate bandwidth of the network. Switches also allow for a high bandwidth Fast Ethernet or Gigabit
Ethernet link to servers or the network backbone. In most small home networks, a switch provides a link to
your modem, thereby allowing you to share your Internet connection. Note: a 100Mbps switch will increase
your bandwidth within your LAN, but does not increase the speed of your Internet connection.
Bridges: When the number of devices on a network increase, so does the network traffic increase, slowing
data transfer. A bridge divides the network into smaller segments and can filter traffic between segments to
create better traffic control. The segments remain part of a logical network.
Routers: Routers are similar to bridges, but are able to logically separate multiple network segments,
allowing them to function as independent networks. Also, routers can perform advanced functions such as
calculating the shortest path between the source and destination.
Gateways: A gateway is a more complex device used to link two or more networks with different network
architectures, e.g., from Ethernet to Token Ring. The term gateway can also refer to the point of access
between a network and the Internet. For example, in your home you may have two or three computers, a
printer, a modem and an Internet router. The router becomes the gateway to the Internet, and the computers
attached are secured “behind” the router.
The OSI Model
The Open Systems Interconnection (OSI) Model is a set of seven layers that describes how data travels
from one computer to another over a network. It is worth outlining here, since network switches and routers
will come with different capabilities and features, depending on which OSI layer they can function. The OSI
Model was developed by the International Standards Organization (ISO) to define a standard for designing
data communication protocols in order for interoperability between equipment from different manufacturers.
Communication between computers begins at the Application Layer, where data is sent through the layers,
across the cable to its destination, and back up the layers to the receiving computer’s application.
The top three levels represent the Application Set:
•
•
•
Layer 7: The Application Layer—interacts with the software (operating system) running on the
computer
Layer 6: The Presentation Layer—translates data from the user to a standard format that other
layers will understand
Layer 5: The Session Layer—synchronizes communication between computers, controlling when
users may send and receive data
The remaining layers represent the Transport Set:
•
•
•
•
4
Layer 4: The Transport Layer—ensures that data makes it intact to its destination, and can
request retransmission if data is not intact. This layer maintains flow control, integrating data from
multiple applications into one data stream for the physical network
Layer 3: The Network Layer—handles logical protocols, translates addresses and routes data
from one device, or node, to another
Layer 2: The Data Layer—assigns the appropriate physical protocol to the data. It defines how
data is transferred over the cable, provides data link service to the higher layers, and defines who
can use the network when multiple computers are trying to access it simultaneously
Layer 1: The Physical Layer—the level of the actual hardware, and deals with the properties of
the cable and connectors
5/21/03
Asanté Technologies, Inc.
White Paper
Network Technologies
Network technologies are used for connection of peripherals to computers, computers to computers,
computers to network devices, and network devices to other network devices or backbones. Different
network technologies use different media access control methods (Carrier Sense Multiple Access, with
Collision Detection—CSMA/CD—or token passing). Local Area Network (LAN) technologies connect
multiple devices that are physically close together, as in an office or home office. Wide Area Network (WAN)
technologies connect devices that are physically separated—across a city, or across countries.
The following list describes several of the most popular network technologies:
•
•
•
•
•
Ethernet, Fast Ethernet, and Gigabit Ethernet
Token Ring
LocalTalk
FDDI
Wireless
Ethernet
The first specifications for Ethernet were established in the 1970s by Digital Equipment Corporation, Intel,
and Xerox (and was known as DIX Ethernet). Later, in the 1980s, the Institute of Electrical and Electronics
Engineers (IEEE) published Project 802. IEEE 802.3 is the Ethernet Working Group standard that continues
to be used today.
Ethernet is the networking technology used by the Internet. It has become a well-understood technology,
and with its speed and reliability, has become one of the most popular network technologies. As a nonproprietary industry standard, Ethernet network components from multiple manufacturers will work together
and be able to communicate effortlessly. It can be implemented in both small and large network
environments, in bus and/or star configurations. Ethernet networks transmit data over UTP, thin coaxial,
thick coaxial, and fiber-optic cables at rates of 10Mbps (Ethernet), 100Mbps (Fast Ethernet), and 1000Mbps
(Gigabit Ethernet). Gigabit Ethernet and Fast Ethernet both have backward compatibility to 10Mbps
Ethernet, making it simple and affordable for growing networks.
All types of Ethernet use a media access control mechanism called Carrier Sense Multiple Access, with
Collision Detection (CSMA/CD). This means that on an Ethernet network, each computer “listens” to the
cable before sending a data packet. If the cable is clear, the computer will transmit; otherwise, the computer
waits and tries again. If two or more computers transmit simultaneously, a collision occurs (the signals from
the two devices run into each other). Each device then attempts to resend its data when the cable is silent. It
is normal to have collisions, as long as the number remains low compared to the number of signals that
transmit successfully.
Token Ring
The Token Ring media access method was developed in the mid 1980s by IBM Corporation, and
subsequently defined by the IEEE in Project 802. Since Token Ring has been IBM's preferred method for
networking, it is found primarily in large IBM mini and mainframe installations. Due to the increasing
popularity of Fast Ethernet and Ethernet, the number of Token Ring networks has significantly decreased.
Token Ring networks use a star-wired ring topology over shielded and unshielded twisted-pair wiring. A type
of hub called a Multi-station Access Unit, or MAU, is at the center of the ring. Two versions of Token Ring
are available: 4Mbps and 16Mbps.
Token Ring networks use a token passing media access control mechanism to circulate packets around the
ring. An electronic token travels from station to station in a single, logical direction. If the token is free, a
station can attach data to the token, change the token's status to busy, and then send the token on to the
next station. Each consecutive station then checks the destination address of the data to see if it should
process the data. It then passes the token on. When the station that originated the token receives it back, it
removes the data from the token and changes the token status back to free.
5
5/21/03
Asanté Technologies, Inc.
White Paper
LocalTalk
LocalTalk is a proprietary media access method built into Apple Macintosh computers and LaserWriter
printers. LocalTalk networks are best suited for small networks of Macs (e.g., a home office or an
independently networked classroom). With LocalTalk, computers are set up in a bus configuration using
both shielded and unshielded twisted-pair wiring. Data transmits at only 230.4Kbps, or about 1/40 the rate of
Ethernet. For this reason, many schools and universities are upgrading their LocalTalk Macintosh
installations to Ethernet and Fast Ethernet in order to better handle large file transfers.
LocalTalk uses the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) media access control
mechanism for transmitting data. CSMA/CA is similar to CSMA/CD in that a computer listens to the cable
before transmitting data. If the computer does not detect a signal, it will send its own signal to try to avoid
collisions—in effect saying, "I'm about to transmit, so stay off the line."
FDDI
The Fiber Distributed Data Interface (FDDI) media access method transfers data at very high speeds
(100Mbps) over fiber-optic cable. Like Token Ring, this access method employs a token passing media
access control mechanism to transmit data. FDDI, however, uses a dual counter-rotating ring topology,
meaning there are two rings of cable with two tokens circulating in opposite directions. This set-up
creates a relatively fault-tolerant network and is commonly used in networks working with mission-critical
data. If a link fails, the network continues to operate. Each station contains relays that bypass a station if it is
having problems. Before Fast Ethernet and Gigabit Ethernet came along, FDDI was commonly used in the
LAN and campus environment, as well as in the backbone to tie together devices on service provider
networks and at exchange points on the Internet. FDDI can support up to 500 devices or nodes, over a
maximum distance of 100 kilometers (60 miles). It can also support copper cable over shorter distances.
The dual counter-rotating rings offer redundancy (fault tolerance). If a link fails or the cable is cut, the
network continues operating. Each station contains relays that join the rings in case of a break or bypass the
station in case it is having problems.
Wireless
Wireless LANs (or WLANs) are the equivalent of wired LANs (usually Ethernet) without the wires. WLANs
send high-frequency radio signals between computers to share data. WLAN technology has advanced
rapidly, and is now a convenient and affordable alternative for home and office environments. The wireless
data rate can reach speeds of 11 Mbps, which is comparable to Ethernet. The convenience of wireless is
attractive to many home network users, by giving freedom to move about with a laptop or by eliminating the
need to run cable through the house.
A typical WLAN consists of a fixed-position wireless access point, which is a wired transceiver
(transmitter/receiver) that broadcasts data to the wireless adapters that are installed in each computer. The
access point can be connected to the network backbone in larger networks. In a home or small office
network, the access point can act as the Internet gateway.
Network Protocols
A network protocol is the format for sending and receiving data. In order for any devices on a network to
communicate, the devices must understand the same format (like a language). Your computer and devices
must support the right protocols for your network to work. Some common protocols are NetBEUI, AppleTalk,
and TCP/IP.
NetBEUI
NetBEUI stands for NetBIOS Extended User Interface. NetBEUI is an updated, extended version of the
NetBIOS protocol that was developed by IBM. Microsoft adopted it for use in its network operating systems,
such as Windows NT and LAN Manager. NetBEUI is useful for communication within a local area network,
but it does not support routing messages to other networks. Your network will require another protocol, such
as TCP/IP, for communication beyond your LAN.
6
5/21/03
Asanté Technologies, Inc.
White Paper
AppleTalk
AppleTalk is the proprietary set of LAN communication protocols created specifically for Apple computers. It
provides inter-network routing, transaction and data stream service, naming service, and file and print
sharing services. The AppleTalk protocol suite is an inexpensive and easy networking protocol that uses the
LocalTalk interface built into Apple computers. AppleTalk is capable of porting to Ethernet, and can be used
together in an Ethernet network.
TCP/IP
Transmission Control Protocol/Internet Protocol (TCP/IP) is the standard for transmission on the Internet,
and has become the dominant networking protocol in the world today. The suite actually uses several
protocols, with TCP and IP as the two main ones. They act as a two-layer system. The higher layer is
Transmission Control Protocol (TCP). It ensures that packets are delivered to the intended destination, in the
same order that they are sent. The lower layer is Internet Protocol (IP). It specifies the format of the data
packets and addresses those packets in order that the message can reach its destination.
Network Services
So far we have described what networks look like physically, as well as how they transmit data. Now we will
look at some of the benefits of networking. Refer to your computers’ operating system (OS) manual for
information on configuring the following services.
File Sharing
An important task of any computer network is the ability to share files. Many versions of popular operating
systems make file sharing fairly easy to set up, and once done, any computer on the network can share files with
any other computer. Sharing your entire hard drive is not recommended, so check with your OS documentation
on how to secure private files.
Print Sharing
Print services allow users to send print jobs to a shared printer. Some networks are set up so that computers
print to a print queue on a server. The server then handles the printing, allowing the user to continue his or
her work even if the print job hasn't finished. A small home network, however, may simply need to share
one printer without the hassle of moving it between computers. Please refer to your OS documentation
for more information.
Some Ethernet switches, or Internet routers, come equipped with a serial port that allows several users
to all reach one printer without enabling print sharing on the OS. See your switch’s documentation for
more information.
Sharing the Internet Connection
One of the more attractive benefits to networking your computers is the ability to share your Internet
connection. There is software available to enable you to share a connection (e.g., Microsoft’s ICS), as well
as hardware devices (e.g., Asanté FriendlyNET cable/DSL routers). You’ll have to select and install the
software or hardware that allows sharing the connection, and you’ll need to configure each computer to
access the Internet via the shared connection. Please refer to your product’s documentation for more
information.
7
5/21/03
Asanté Technologies, Inc.
White Paper
Glossary
Access Method: The method that a computer uses to put a signal onto the networking media is called the
access method. Media access methods include token passing and CSMA/CD.
AppleTalk: A networking protocol developed by Apple for communication between Apple computer products
and other computers that is independent of the network layer on which it is run. Implementations exist for
LocalTalk, a 230.4Kbps local area network; and EtherTalk, a 10Mbps Ethernet local area network.
Backbone: The line or set of lines that local area networks connect to for a wide area network connection,
or, within a LAN, to span larger distances (e.g., between buildings). On the Internet or other WAN, a
backbone is a set of paths that local networks connect to for long distance connection.
Bandwidth: Typically, this means the amount of data that can be sent through a given communications
circuit. For example, Ethernet has a bandwidth of 10Mbps (megabits per second). Technically, it is the
difference, in Hertz (Hz), between the highest and lowest frequencies of a transmission channel.
Bits Per Second (bps): A measure of the rate of data transmission.
Bridge: A device that connects two or more networks and forwards packets between them. The segments
must use the same networking technology, such as Ethernet, but may use different cable types. It is used to
relieve network congestion by separating traffic on the two networks. Bridges differ from repeaters in that
repeaters simply forward electrical signals from one cable to another. Bridges can usually be configured to
filter packets; that is, to forward only certain traffic. See repeater.
Coaxial Cable: A cable with an inner and outer conductor sharing the same axis or center point. Ethernet
can use coaxial cable; cable TV also uses it.
CSMA/CA (Carrier Sense, Multiple Access with Collision Avoidance): A media access method used by
the local area networking technology LocalTalk. Similar to CSMA/CD (see below).
CSMA/CD (Carrier Sense Multiple Access with Collision Detection): A media access method used by
local area networking technologies such as Ethernet. Multiple stations contend for access to a transmission
medium by listening to see if it is idle. A mechanism is provided to detect when two stations simultaneously
attempt to transmit data.
E-mail (Electronic mail): A system enabling a computer user to exchange messages with other computer
users (or groups of users) via a communications network. E-mail is one of the most popular uses of
internets.
Ethernet: The most common LAN networking system in the world today. Ethernet is a best-effort delivery
system that uses CSMA/CD technology. It runs at 10Mbps, 100Mbps (Fast Ethernet), or 1000Mbps (Gigabit
Ethernet). Ethernet can be run over thin-wire coaxial cable (10BASE2), thick-wire coaxial cable (10BASE5),
twisted pair cable (10/100/1000BASET), or fiber optic cable.
FDDI (Fiber Distributed Data Interface): A high-speed (100Mbps) fiber optic LAN standard based on token
ring.
Fiber Optic: A data transmission medium consisting of glass or plastic fiber(s).
Gateway: The original Internet term for what is now called a router—or more precisely, an IP router. In
modern usage, the terms gateway and application gateway refer to systems that connect LANs with different
protocols or data format.
Internet: A worldwide network of interconnected computers and computer networks.
IP (Internet Protocol): The network layer protocol for the TCP/IP protocol suite.
ISO (International Organization for Standardization): The organization responsible for establishing
worldwide computer network standards, it developed the seven-layer OSI (Open Systems Interconnection)
suite of network protocols.
8
5/21/03
Asanté Technologies, Inc.
White Paper
LAN (Local Area Network): A LAN connects a group of computers, printers, and other devices together,
usually a network in one office or building.
Layer: Communication networks for computers may be organized as a set of more or less independent
protocols, each in a different layer (or level). The lowest layer governs direct host-to-host communication
between the hardware on different hosts; the highest layer consists of user applications. Each layer builds
on the layer beneath it. For each layer, programs on different hosts use protocols appropriate to the layer to
communicate with each other. TCP/IP has five layers of protocols; OSI has seven.
MAU: 1. Media Access Unit (transceiver). 2. In a Token Ring network, Multi-station Access Unit (properly
abbreviated MSAU).
Media: The physical wiring of a network; for example, coaxial cable, twisted-pair wire, or fiber optic cable.
NetBEUI (NetBIOS Extended User Interface): Provides data transport services for NetBIOS.
NetBIOS (Network Basic Input/Output System): An interface used by application programs in a PC to
access networks. Defined by IBM and extended by Microsoft. Used in Windows NT, Windows for
Workgroups, and OS/2.
Network: A computer network is a data communications system that interconnects computer systems at
different sites. A network may be composed of any combination of LANs or WANs.
NIC (Network Interface Card): Circuit board installed in a personal computer to allow connection to a local
area network.
Operating System (OS): An organized collection of programs that control the operation of a computer
system (e.g., MS-DOS, Windows, or Macintosh OS X).
OSI (Open Systems Interconnection) Reference Model: A suite of protocols, specifically ISO standards,
that uses a seven-layer model as the international standard computer network architecture. See ISO.
7 - Application (managing communications between applications)
6 - Presentation (identifying data syntax)
5 - Session (establish and control dialog between users and machines)
4 - Transport (end-to-end reliability)
3 - Network (routing of end-to-end data packets)
2 - Data Link (error-free transmission of bits on the interface)
1 - Physical (hardware interface)
Protocol: A formal description of message formats and the rules two computers must follow to exchange
those messages. Protocols can describe low-level details of machine-to-machine interfaces or high-level
exchanges between application programs.
Repeater: A device that propagates electrical signals from one cable to another without making routing
decisions or providing packet filtering. See bridge and router.
Router: A device that interconnects LANS and dynamically routes data depending on parameters such as
destination and available routes (at the OSI network layer 3). See gateway, bridge, and repeater.
Server: A computer that provides the services for all nodes on a LAN. Examples of servers are file servers,
print servers, and database servers.
Switch: A switch is a multi-port bridge. It routes packets out one of its ports based on the destination
address of the packet.
TCP (Transmission Control Protocol): The TCP/IP standard transport layer protocol in the Internet suite of
protocols, providing reliable, connection-oriented, full-duplex streams. It uses IP for delivery.
TCP/IP Protocol Suite (Transmission Control Protocol over Internet Protocol): This is a common
shorthand that refers to the suite of transport and application protocols that runs over IP.
9
5/21/03
Asanté Technologies, Inc.
White Paper
Token: A combination of bits that a workstation uses as permission to transmit on a token ring network.
There is only one token on a token ring network. FDDI uses token passing—in which case, more than one
token may be present at a time.
Token Ring: A token ring is a type of LAN with nodes wired into a ring. Each node constantly passes a
control message (token) on to the next; whichever node has the token can send a message.
Topology: A description of the physical cabling and connections on a network.
Transceiver: A device used to convert from one media type to another.
Twisted Pair: Cable used in a network where the wires in cable pairs are twisted around each other. Wire
types are STP (shielded) or UTP (unshielded) twisted pair.
WAN (Wide Area Network): A network connecting devices over longer distances.
10
5/21/03
Asanté Technologies, Inc.