Download A. LAN models can be configured as either “client / server (domain)”

COMMUNICATIONS / NETWORK TECHNOLOGY
(pages 36-38 Basic Computer Concepts , pages 313-349, 361-373
Technology in Action)
- Part 2III.
PC communication environments.
A.
Local Area Network (LAN) – In this environment the user has access to other PCs or a
server from where other resources (nodes) can be shared. A PC in a LAN is typically
referred to as a “workstation”. LANs are short distance networks encompassing areas
usually within a building and no greater than a mile.
1.
LANs use “packet switching” technology which basically breaks down a message
into a series of data packets sent out at different intervals and reassembled at
their destination location. Packet switching results in faster transmission.
2.
Bob Metcalfe in 1976 devised a networking standard called “Ethernet” which has
become a model for most LANs today. The IEEE sanctioned the Ethernet
standard. Ethernet networks are identified as follows:
a. 802.3 – Ethernet wired – to conform to this standard specific equipment and
software is required
b. 802.11 – Ethernet wireless standard - to conform to this standard specific
equipment and software is required
IV.
B.
Inter-network – An inter-network is a series of LANs connected to each other. The
benefit is obvious, joining LANs together provides access to a broader range of
resources. Routers establish a connection between LANs
C.
Wide Area Network (WAN) – PCs accessing network nodes over remote distances.
(telecommunications) Phone lines, satellites, or leased lines such as T1 & T3 establish
the communication link
LANs.
A.
LAN models can be configured as either “client / server (domain)” or “peer-to-peer
(P2P)”.
1.
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“Client / Server” or “Domain”. A domain is a group of computers sharing
resources through a “dedicated” or central server. The server authenticates the
user login to the network and manages network resources. A domain account
must exist on the server for all domain users. All sharing of resources occurs
through the server. A domain establishes a group of users sharing common
resources. Advantages: Better resource security, centralized location of
resources, ideal for large networks. Disadvantages: Cost for NOS software
license and the server itself.
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a. The Login process. Before a user can access network resources, an
authentication process called “logging in” must first occur. An unsuccessful
login will deny access to network resources.
More sophisticated networks use a method of authentication called
“biometrics” whereby distinct human characteristics (fingerprint, retina
pattern) are used to identify a user to the network. Login information typically
involves a user name, password, or PIN.
2.
V.
Peer-to-Peer (P2P). A LAN that doesn’t use a central server but instead shares
resources from other workstations is called “peer-to-peer”. Peer-to-peer login is
performed at the local workstation. In a peer-to-peer network, all workstations
perform a dual role of “client” and “server”. The local PC designates what
resources (files, printers, etc.) are to be shared and then makes them available to
the other PC peers in the network. Because the workstations in this environment
are not just dedicated to sharing resources but are also involved in processing,
they are referred to as “non-dedicated” servers. Advantages: low cost to
implement, ideal for small network (10 nodes or less). Disadvantages: Little
security, decentralized shared resources. A standard O.S. such as Windows XP
or Windows 2000 professional can provide the communications instructions
required.
LAN topologies – the physical architecture or layout of a LAN is referred to as a “topology”.
Workstations in a given topology must follow similar network protocols. The following are
examples of popular LAN topologies.
A.
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Star – one central computer called the Host provides the shared resources for the users
in the network. If the Host fails, the entire network fails.
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VI.
B.
Ring – all computers are connected in a circular manner, no one central Host controls
the network. Because data travels in a circle or ring throughout the network, if the ring is
broken the network fails.
C.
Bus – all systems are connected linearly via cable, the cable serves as the
communications link. If one system fails within the network, the network is able to
survive. If the cable fails, all communications are broken.
Other.
A.
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Viewing network components. The Windows Vista start menu displays an option for
“Network” which in essence replaces the “Network neighborhood” option from prior
Windows versions. Selecting the “Network” icon opens the “Network & Sharing Center”
window. From this window you can identify network components and perform network
functions.
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B.
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Special Equipment. Depending on your network configuration you may or may not need
additional hardware. The following devices are common but not always necessary.
1.
Hubs or concentrators provide a link to the server where multiple workstations
are involved. Workstations do not connect directly to the server, they connect to
a hub which in turn is connected to the server. The hub provides the ports for the
cables originating from the workstations.
2.
Modems – for dialup connections or telecommunications (explained earlier)
3.
Routers – establish a connection point for nodes in differing networks –
extremely common
4.
Switch – establish a communication link for nodes within the same network
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