Download Computer Networks

Computer Networks
Coordonator: Mr. Dr. Z. Pólkowski
Siposs Arnold Konrad
Computer Network standards
• Standards play an important role in networking. Without
standards, manufacturers of networking products have no
common ground on which to build their systems.
Interconnecting products from various vendors would be
difficult, if not impossible.
• It is necessary to have standards because if each company
had its own protocol standards there would be a lack of
communication from different machines and would result in
one company being hugely successful and the other running
out of business due to lack of being able to communicate with
other machines. So this is why its necessary to have network
standards such as: Token ring, Arcnet, Ethernet and FDDI.
Source: http://www.netguru.net/ntc/NTCC6.htm
ARCnet
Source: http://site.the.cz/index.php?id=28
Description
• ARCNET is designated as a high-speed local area
network (LAN) well-suited for real-time control applications
in both the industrial and commercial marketplaces. Its
proven design, robust performance and the availability of
low-cost silicon have made it the network of choice
between embedded microcontrollers.
• Originally developed by Datapoint Corporation in the mid70s and moved to silicon in 1982, ARCNET continues to
find new applications well beyond its original intention as a
network for an Attached Resource Computer (ARCNET).
The ARCNET Resource Center (ARC) is a play on those
original words.
Source: http://www.alrcnet.com/
How ARCnet works
• To start off, ARCnet is not a standardized network. All
information provided here is gathered through the years by
different people and by just making mistakes, so if you
have other experiences don't be surprised, but share them
with us.
• This way we can all learn from it.
• ARCnet (Attached Resource Computer NETwork) was
originally developed by Datapoint Corporation in 1968, way
before OSI and the like. The original purpose was a
harddisk interface, later it became popular as a local area
network.
• All distaces are rough estametes. The actual calculation
should be done like this: an active device provides 24 Volt
output, and needs atleast 5 Volt on the receving pins.
Source: http://ckp.made-it.com/arcnet.html
ARCnet features
• In September 1977, the world's first commercially available local area
network was first put into service at Chase Manhattan Bank, New
York, as a beta-site.
• Short for Attached Resource Computer network, ARCnet was
developed by Datapoint Corporation in San Antonio, Texas. It was
defined as a group of nodes that communicates to one another over a
geographically-limited area usually within one building or a campus of
buildings.
• It was the simplest, and least expensive type of local-area network. It
used a token-ring architecture, supported data rates of 2.5 Mbps, and
connected up to 255 computers. A special advantage of ARCnet is that
it permitted various types of transmission media to be mixed on the
same network: twisted-pair wire (Max. extension 150 meters), coaxial
cable (650 m.) and fibre optic cable (2.000 m.)
• Today, ARCnet is still alive in numerous companies all over the world
and has more than seven million installed nodes.
Source: http://www.old-computers.com/history/detail.asp?n=23&t=3
Token Ring
Source: http://www.pcmag.com/encyclopedia/term/52963/token-ring
Definition
A Token Ring network is a local area network (LAN) in which all computers
are connected in a ring or star topology and a bit or token-passing scheme
is used in order to prevent the collision of data between two computers that
want to send messages at the same time. The Token Ring protocol is the
second most widely-used protocol on local area networks after Ethernet.
The IBM Token Ring protocol led to a standard version, specified as IEEE
802.5. Both protocols are used and are very similar. The most common
local area network alternative to Ethernet is a network technology
developed by IBM, called token ring. Where Ethernet relies on the random
gaps between transmissions to regulate access to the medium, token ring
implements a strict, orderly access method. A token-ring network arranges
nodes in a logical ring, as shown below. The nodes forward frames in one
Direction around the ring, removing a frame when it has circled the ring
once.
Source: http://searchnetworking.techtarget.com/definition/Token-Ring
How Token Ring works
Unlike Ethernet, Token Ring uses a ring topology whereby the data is
sent from one machine to the next and so on around the ring until it ends
up back where it started. It also uses a token passing protocol which
means that a machine can only use the network when it has control of
the Token, this ensures that there are no collisions because only one
machine can use the network at any given time. Token Ring networks are
now very rare because the cost and flexibility of Ethernet came to
dominate the marke. When the first Token Ring computer comes online,
the network generates a token. The token is a predetermined formation
of bits (a stream of data) that permits a computer to put data on the
cables. The token travels around the ring polling each computer until one
of the computers signals that it wants to transmit data and takes control
of the token. A computer cannot transmit unless it has possession of the
token; while the token is in use by a computer, no other computer can
transmit data. After the computer captures the token, it sends a data
frame out on the network.
Source: http://www.datacottage.com/nch/troperation.htm#.VRbaWi7AqOV
Token Ring features
A Token Ring network is an implementation of IEEE standard 802.5. Their
token-passing ring access method, more than their physical cable layout,
distinguishes Token Ring networks from other networks. Architecture
The architecture of a typical Token Ring network begins with a physical
ring. However, in its IBM implementation, a star-wired ring, computers on
the network are connected to a central hub. Figure 3.23 shows a logical
ring and a physical star topology. The logical ring represents the token's
path between computers. The actual physical ring of cable is in the hub.
Users are part of a ring, but they connect to it through a hub.
Monitoring the System
The first computer to come online is assigned by the Token Ring system to
monitor network activity. The monitoring computer makes sure that frames
are being delivered and received correctly. It does this by checking for
frames that have circulated the ring more than once and ensuring that only
one token is on the network at a time.
Source: http://www.techopedia.com/definition/26095/token-ring-network
Ethernet
Source: http://hackd.org/sniffers-detailed-faqs/
INFORMATION
. Ethernet-is a family of computer networking technologies for local area
networks (LANs) and metropolitan area networks (MANs). It was
commercially introduced in 1980 and first standardized in 1983 as IEEE
802.3, and has since been refined to support higher bit rates and longer
link distances. Over time, Ethernet has largely replaced competing
wired LAN technologies such as token ring, FDDI, and ARCNET. The
primary alternative for contemporary LANs is not a wired standard, but
instead a wireless LAN standardized as IEEE 802.11 and also known
as Wi-Fi.
Source: http://en.wikipedia.org/wiki/Ethernet
GENERAL INFORMATION
• The term 'Ethernet' refers specifically to a set of standards for
connecting computers in order they can share information over a
common wire or network. Strictly speaking, ethernet systems should
comply to the International Standard ISO/IEC 8802-3 or IEEE 802.3.
• As in all systems, there are reasons to use an ethernet network, but
also difficulties that must be overcome. The main advantages of
ethernet are:
• The ability to carry several hundred times more information on a
single cable than would be carried on a typical serial cable. Whereas
DMX512 operates at 250kb/s, Ethernet operates at 100 Mb/s - 400
times faster;
• The ability to connect multiple devices in a single network, regardless
of the information interchange relationship between the devices.
Ethernet allows all devices in the network to communicate;
• A reduction in the amount of cable required. Economic factors will
drive the demand for this technology;
Source: http://www.webopedia.com/TERM/E/Ethernet.html
GENERAL INFORMATION (PART 2)
• The ability to add devices to the network at any time, giving a more
flexible installation;
• Required components are readily available and have a relative low
cost.
• Despite these factors, there are also disadvantages associated with
ethernet systems:
• Maximum cable length between two devices is limited to 100metres,
compared with 250metres for DMX512 systems. In larger
installations, where very long cable runs are required, it is necessary
to utilise fibre-optic cabling;
• RJ45 connectors used for ethernet networks are not suitable for
heavy-duty use in industrial situations;
Source: http://www.webopedia.com/TERM/E/Ethernet.html
FDDI
Fiber Distributed Data Interface
Standard specification
Introduction
Fiber Distributed Data Interface (FDDI) is a standard for data
transmission in a local area network. It uses optical fiber as its standard
underlying physical medium, although it was also later specified to use
copper cable, in which case it may be called CDDI (Copper Distributed
Data Interface), standardized as TP-PMD (Twisted-Pair Physical
Medium-Dependent), also referred to as TP-DDI (Twisted-Pair
Distributed Data Interface).
Source: http://www.webopedia.com/TERM/F/FDDI.html
Specification part 1
• FDDI stands for Fiber Distributed Data Interface. The FDDI standard
is ANSI X3T9.5 . The FDDI topology is ring with two counter
rotating rings for reliability with no hubs. Cable type is fiber-optic.
Connectors are specialized. The media access method is token
passing. Multiple tokens may be used by the system. The maximum
length is 100 kilometers. The maximum number of nodes on the
network is 500. Speed is 100 Mbps. FDDI is normally used as a
backbone to link other networks. A typical FDDI network can
include servers, concentrators, and links to other networks.
CDDI is a copper version of FDDI which uses category 5 cable.
Obviously the distance is more limited than FDDI.
• Devices called concentrators provide functions similar to hubs. Most
concentrators use dual attachment station network cards but single
attachment concentrators may be used to attach more workstations to
the network.
Source: http://www.comptechdoc.org/independent/networking/cert/netfddi.html
Specification part 2
Therefore a break in the cable will result in the secondary ring being
used. There are two network cards which are:
1.Dual attachment stations (DAS) used for servers and concentrators are
attached to both rings and a router or switch can link an FDDI network to a
local area network (LAN). Normally FDDI is used to link LANs together
since it covers long distances.
Characteristics Summary:
•Topology - Double ring.
•Cable - Fiber.
•Speed - 100Mbps.
•Maximum segment length - 2000 meters.
•Media access - Token passing.
•Maximum nodes on the network - 500.
Troubleshooting
Plastic fiber is only useful to 50 meters. Multimode glass is good to 2
kilometers. A tool called an Optical time domain reflectometer (OTDR) may
be used to debug this network.
Source: http://www.cisco.com/c/en/us/td/docs/internetworking/technology/handbook/ito_doc/FDDI.html#wp1020549
LAN Network’s
• When talking about LAN Networks, we need to know how they work .
• That is why we can use simulation programs to virtual make connections
between more computers and hubs or switches.
Network devices
• For a network to work, we also need to have network devices, that is why
i will show you some devices i configurated during classes.
• When you configure a router you first need to change username and
password which you will use to login to your router:
Network devices
• After you configure account you need to configure the wireless
connection and IP adress.
Network devices
• By doing this you only need to configure security and your router is ready
to work and transmit wireless internet to all the computer/laptops in the
room .
Network devices
• Other devices that i tested sucesfully are:
• Sitecom wireless micro USB Adapter 150N, which can be tested by
downloading and installing it’s software, than read the microUSB from
my PC after restarting the computer. Downloading and installing was easy
because the package came with the CD that had the instruction manual
and the software as well. I also checked on the security using
the password and mac address.
Source: http://www.wireless-driver.com/sitecom-wl349-windows-drivers-utility/
Network devices
• The last device i have checked was an Sitecom 300N wireless Gigabit
modem router, which was simple to configure you just need to reset the
device, enter the adress and log in to the device and follow the wizard
setup which whill guide you through the configuration, after this is
completed the device should work properly.
Source: http://www.bol.com/nl/p/sitecom-300n-wireless-gigabit-modem-router/1003004012112299/
References
• http://site.the.cz/index.php?id=28
• http://3w.dokisoft.com/why-computer-networks-have-interruptions/
• http://www.pcmag.com/encyclopedia/term/52963/token-ring
• http://hackd.org/sniffers-detailed-faqs/
• http://www.freepik.com/free-photo/ethernet-cables-close-up_605844.htm
• http://www.webclasses.net/3comu/intro/units/unit05/sec03f.html