Transcript Elements of a Small PC Network

Elements of a Small PC Network
• LAN Standards
– We will focus on LANs that follow the Ethernet
standard (80% do)
• Small Ethernet PC networks use only
inexpensive UTP wiring (or Coax)
• Speeds for NICs and Hubs or Switches
– 10Base-T (10 Mbps, baseband, UTP)
– 100Base-TX (100 Mbps, baseband, UTP)
– 1000Base-T (Gigabit Ethernet) (1 Gbps)
Elements of a Small PC Network
• Need a hub or switch to connect the PCs
– Connector box with multiple plug-in jacks
– Hubs and switches are described later
• Each PC needs a network interface card (NIC)
– Implements physical and
data link layer connection
to the LAN
• Wire
– Business-grade UTP telephone wiring
Elements of a Simple PC
Network
• Ethernet UTP Wiring
– 4-pair bundle (8 wires)
– Each pair is twisted
– Terminates in RJ-45
connector
• Quality Level
– Category 5
– Older categories (3 and 4) exist but are now fairly rare
Elements of a Simple PC
Network
• Ethernet UTP Wiring
– Come pre-cut in many useful lengths (1 m, 2 m,
25 m, etc.) with connectors already added to
both ends
– Can also cut to precise lengths needed and then
attach connectors
• Must test the wire after cutting it and attaching
connectors!
Elements of a Simple PC
Network
• Plenum Wiring
– For wiring run through airways; covering does
not give off toxic fumes if it burns
• Required if wires are run through air conditioning
ducts
• Not needed in false ceilings
– More expensive but required by law and
concern for employee safety
Elements of a Small PC Network
• Ethernet Hub Operation
– One station transmits a single bit to a hub (physical
layer operation)
– Hub broadcasts bit to all attached stations
– All but the destination PC should ignore the message
Hub
Hub
Bit
Bit
Elements of a Small PC Network
• Ethernet Hubs
– Broadcasting is simple, so
– Hubs are inexpensive
Elements of a Small PC Network
• Ethernet Hubs Can Create Latency
– Only one station may transmit at a time
or the signals will collide and be
unreadable
– Other stations must wait (latency)
Must Wait
Elements of a Small PC Network
• Ethernet Hubs Can Create Latency
– Becomes a problem with 100+ PCs and
10 Mbps hub
– 200 PCs is upper limit for tolerable
service with a 10 Mbps hub
Must Wait
Elements of a Small PC Network
• Ethernet Switches
– One station transmits a frame to a switch (data
link layer operation)
– Switch only transmits frame out port of
destination PC
Switch
– No broadcasting out all ports
Switch
Frame
Frame
Elements of a Small PC Network
• Ethernet Switches
– Multiple conversations can take place
simultaneously because there is no
broadcasting, which ties up all ports
– No wait to transmit; no Latency
Switch
Elements of a Simple PC
Network
• Client PCs
– End user’s desktop or notebook PC
– Add network interface card (NIC)
– With Win95, Win98, Win NT, or Win 2000, no
extra software is needed
– Networks have many client PCs
Elements of a Simple PC
Network
• Servers
– Provide services to client PCs
– Usually PCs themselves
– Most PC nets have multiple servers
– Require a NIC
– Require a server operating
system (SOS)
– Require application software
Elements of a Simple PC
Network
• Server Operating System (SOS)
– Servers need operating systems more reliable
than client PC operating systems
– Windows NT/2000 Server, Novell NetWare,
UNIX, LINUX
• Application Software
– Provides the services offered by the servers
– E-mail, word processing, file sharing, etc.
– More expensive than the SOS
Elements of a Simple PC
Network
• Novell NetWare SOS
– Once dominant, but market share has shrunk
– Excellent file and print service
– Excellent directory service (later)
– Until recently, was not sufficiently robust and
scalable for servers other than file servers
Elements of a Small PC Network
• Microsoft Windows Server Operating System
– More robust than desktop Windows (Win 95, Win 98,
etc.)
– All 32-bit code
– Microsoft Windows NT Server before 2000
– Newer Microsoft Windows 2000 Server
New
• Versions in order of increasing functionality: Windows 2000
Server, Advanced Server, DataCenter Server
Elements of a Small PC Network
• Microsoft Windows Server Operating System
– Easy to install, learn, and use because resembles
desktop Windows
– Becoming dominant for small business and small
department servers
– NT Server has had serious reliability and scalability
problems
– Windows 2000 Server versions promise to improve
reliability and scalability
Elements of a Small PC Network
• UNIX
– Workstation servers run UNIX
– Extremely reliable
– Dominate for large enterprise servers
Elements of a Small PC Network
• UNIX
– Expensive to buy
– Must retrain staff or hire UNIX staff
– Many versions of UNIX exist
• Most run the same application software
• However, have different management utilities, etc.,
requiring training for each version used
– Not for Small PC Networks
Elements of a Small PC Network
• LINUX
– Version of UNIX
– Runs on PCs for low cost
– Available free
• But usually pay around $50 for packaged version
– Reliable like other UNIX versions
– Open Source: Many people are developing
tools to add to the LINUX core
Elements of a Small PC Network
• LINUX
– Available in Distributions
New
• A distribution has the LINUX kernel plus other
programs
• Available on CD-ROM or by downloading
• Distributions from different LINUX vendors differ
in the specific programs included
• Differences make selection, implementation difficult
Elements of a Small PC Network
• LINUX
– Requires Extensive Labor to Set Up, Maintain
– Device driver software often is lacking for
printers, disk drives, and other devices
– Requires more training because it is UNIX
– Better distributions and support coming?