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.

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 connectionto 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-45connector

• 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

BitBit

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

– No broadcasting out all portsSwitch

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 LatencySwitch

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

• Versions in order of increasing functionality: Windows 2000 Server, Advanced Server, DataCenter Server

New

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• 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

New

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?