Transcript internet infrastructure - e

INTERNET INFRASTRUCTURE
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LANS
WANS
INTRANETS AND EXTRANETS
WIRELESS NETWORKS
WIRELESS NETWORKS
• It uses radio waves to connect computers equipped
with wireless NICs. While there are a number of
different wireless standards in use, most wireless
hardware available today supports one or more of the
IEEE 802.11 series of specifications. IEEE 803.11
networks are often referred to as wireless fidelity (wi-fi)
• Wireless networking can be used to connect computers
directly to each other in a peer-to-peer network, or to
connect computers to an access point that can be used
to connect to a wireless LAN or even the internet.
• Wireless networks use radio waves to network
computers
What are the advantages?
• Older buildings may make it impossible or
very expensive to set up network connections
using cable.
• Wireless technology can penetrate walls and
make such networking straightforward and
affordable
• Computers and other equipment in a network
can be rearranged without the need to move
or change cable connections.
Internet Backbone
• Internet backbone consists of high-speed lines
that form the core network of the internet.
• The first Internet backbones were supported
by ARPANET and later NSFnet.
• A number of different companies currently
support the links that make up the internet
backbone.
• Internet backbone high-speed lines include
T1,T3,OC-1, and OC-3 cables.
Internet Backbone
• T1 cables contain two twisted-pair wires with
a bandwidth of 1.544 megabits per second. T3
lines contain 28T1 lines and have a bandwidth
of 44.736Mbps.
• OC-1 and OC-3 are fibre optic cables (optical
carrier or OC) and support capacities of
51.84Mbps and 155.52Mbps
Bandwidth, Throughput, and Latency
• Bandwidth expresses the theoretical
maximum amount of data that an internet
connection can transmit in one second.
• Internet bandwidth is measured in bits per
second
• E.gs. Of Bandwidths
Bandwidth
• Bandwidth can be symmetrical (even) or
asymmetrical (uneven) depending on the
technology used to connect to the internet
• Technologies offering the same bandwidth
speeds whether uploading or downloading
data are symmetrical
• Technologies with differing bandwidths for
uploading and downloading are referred to as
asymmetrical
Bandwidth
• Asymmetrical technologies almost always make
more bandwidth available for downloading
compared to uploading.
• This uneven division is a compromise that meets
the needs of most internet users because most
people download data far more frequently than
they upload it.
• It is important to realize that bandwidth measures
the capacity of an internet connection, stating only
the maximum theoretical data transmission
capacity of the connecting medium
Bandwidth
• Network overhead typically prevents a
connection from achieving its theoretical
maximum.
• Network over head means that the network
itself uses a certain percentage of available
bandwidth to support data transmission.
• E.g. TCP/IP protocol requires some bandwidth
when packaging and addressing data.
Throughput
• It provides a better measure of internet connection
speed than bandwidth.
• Throughput rates the actual amount of user data
the network can transmit per second, rather than
the theoretical rate of data transmission capacity
measured by bandwidth.
• Throughput measures only useable data
transmitted and does not include data used for
network overhead.
Latency
• Even an internet connection with high
bandwidth and/or high throughput could be
slow due to latency.
• Latency refers to the time between the
transmission and reception of data across a
network.
• It is expressed as milliseconds (ms)
Latency
• A number of factors contribute to the delays
caused by latency, including device delays and
network congestion
• Although the bandwidth and throughput for a
Satellite internet connections may be high, the
long route that the satellite signals must travel
between earth and outer space can cause
delays (latency) of more than 750 ms.
• A user can check latency using a utility
program called ping.
Latency
• Ping sends a small data packet to a host and
then measures the time it takes for the packet
to go to the host and return.
Connection Type
Latency Rate
Dial-up modem
100-200ms
ISDN
15-30ms
DSL/Cable
10-20ms
Satellite
500-750ms
T1
2-5ms
Exercise
• Ping
ISPs
• How to choose an ISP
– Needs assessment: how you use the internet
whether is for checking of mails or beyond that. If
you use the internet to check mails and browse
the internet, you don’t need an ISP who offers
large amount of bandwidth but if you view
streaming video, upload or download large files,
or play online games, then you need an ISP who
offers large amount of bandwidth
ISP
• Analyze how many hours per week or per
month you use or plan to use the internet.
Many ISPs and IAPs offer flat monthly or
annual rates, but some offer packages that
charge for an initial hourly package and bill for
any hours that exceed that amount.
• If you want your ISP to host your web site, you
will need to assess how much disk storage, if
any, your ISP offers with an account, as well as
the price for additional MB of storage.
Shared resources
• Workgroup computing and groupware: workgroup
computing also called collaborative computing, enables
teams of co-workers to use networks of
microcomputers to share information and to cooperate
on projects. It is not only possible by networks and
microcomputers but also by groupware. Groupware is
software that allows two or more people on a network
to work on the same information at the same time.
Shared resources
• Electronic data interchange: is the direct
electronic exchange between organizations
computer systems of standard business
documents such as purchase orders, invoices,
and shipping documents. Business to business
transactions conducted via a computer
network. In order to use EDI, organizations
must have compatible computer systems, or
else go though an intermediary.
Shared resources
• Intranets and Firewalls: Intranets are internal corporate
networks that use the infrastructure ad standards of
the internet and the world wide web. One of the
greatest considerations of an intranet is security.
Firewall as a security system is employed in intranets. A
firewall is a system of hardware and software that
connects the intranet to external networks, such as the
internet. It blocks unauthorized traffic from entering
the intranet and cal also prevent unauthorized
employees from access the intranet
Shared resources
• Two components of firewalls are a proxy server and
caching.
• Proxy server is a server, or remote computer, that may
exist outside of the organization’s network, ad all
communications to the organization are routed
through it. The proxy server decides which messages or
files are safe to pass through to the organization’s
network. It can also provide document caching
Shared resources
• Caching is to store copies of web pages for
quick access; the purpose is to speed up the
web for their users. The only difficulty with
this practice is that the original web page may
have been updated, but this is not reflected
on the copy in the cache in the proxy
computer.
Shared resources
• Extranets: are extended intranets connecting
not only internal personnel but also selected
customers, suppliers, and other strategic
offices