guide to networking essentials, 6 th edition chapter 2: network hardware essentials

Guide to Networking Essentials, 6th Edition

Chapter 2: Network Hardware Essentials

Copyright © 2012 Cengage Learning. All rights reserved. 2

Objectives

2

• In this chapter, students will learn:

– Basic operation of network repeaters and hubs

– The purpose of network switches

– The operation of wireless access points

– the basic operation of network interface cards

– The function of routers

Section 1.1

Intro; Repeaters; HubsPP. 61-66



Network Repeaters and Hubs

• Early networks didn’t use interconnecting devices

• Severely limited network size– Total cable length and number of computers



• Repeats signal

• Used to extend networks– A repeater receives bit signals generated by NICs and other

devices, strengthens them, and then “repeats” them to other parts of the network

• Enables you to connect computers whose distance from one another would make communication impossible

• Two ports



A repeater extends the length of a network


Hub (Multiport Repeater)

• Hub – a multi-port repeater

• Signaling Process:

1. Receives signal from one port

2. Cleans the signal - Filters out electrical noise

3. Regenerates the signal to full strength

4. Transmits the signal to all other ports


Hubs (Multiport Repeaters)

A multiport repeater or hub


Hubs and Network Bandwidth

• Network Bandwidth – The amount of data that can be transferred in an interval.

• Usually measured in bits per second (bps)

• Speeds range from 10 Mbps up to 10 Gbps

• Bandwidth sharing – when all computers connected to the hub must share the amount of bandwidth the hub provides

– Causes collisions


Hub Indicator Lights

• Power, link status, network activity, collisionsPower, link status, network activity, collisions

• Uplink port – port used to connect two hubs together or hub to a switch

• Simulation 3: Basic operation of a hub

Comprehension Check

• Enables you to connect computers whose distance from one another would make communication impossible.

• Repeater

• Networking device that sends data out all ports

• Hub

• Two things that hubs do to improve data quality

• Cleans and regenerates signal going out all ports


Comprehension Check

• Name the four lights found on a network hub

• Power, link status, network activity, collisions

• Network Bandwidth

• The amount of data that can be transferred in an interval

• How is network bandwidth measured?

• bps (Mbps or Gbps)


Section 1.2

Switches and WAPsPP. 66-79



Network Switches

• Looks like a hub

• Inside a LAN

1. Reads data a frame at a time

2. Gets MAC address from each frame

3. Forwards the message to only the port tied to that MAC address.


Network Switches

Switches maintain a switching table


Network Switches

Steps of switch operation:1. Receives a frame.

2. Reads the source and destination MAC addresses.

3. Looks up the destination MAC address in its switching table.

4. Forwards the frame to the port where the computer owning the MAC address is found.

5. The switching table is updated with the source MAC The switching table is updated with the source MAC address and port informationaddress and port information.

• Simulation 4: Basic operation of a switch


Switches and Network Bandwidth

• Each port gets dedicated bandwidth

• Can operate in full-duplex mode– Can send and receive data simultaneously– Hubs only half-duplex

• Switches are the preferred device because of these advantages


Switch Indicator Lights

• Link status indicators

• Activity indicators

• May have full-duplex or half-duplex mode indicators

• Uplink Port – Used to connect switches

– Expand network

– Some switches have a dedicated uplink


Wireless Access Points

• Wireless Access Point - Operate similarly to a hub without wires.

• Wireless Router - combines the functions of an AP, a switch, and a router

– Small businesses and home networks

• Wireless LANs usually attached to wired networks


Wireless Access Points

A wireless router


Basic AP Operation

• All stations hear all data being transmitted

• Receiving device sends an acknowledgment back to the sending device to indicate successful reception

• Request to send (RTS) - optional– Workstation requesting permission to transmit to AP

• Clear to Send (CTS) - optional– AP response saying it OK to transmit


Wireless APs and Network Bandwidth

• All the extra chatter required to send data in a wireless network slows communication

• The effective bandwidth is about half of effective bandwidth found on physical networks

• Most APs operate from 11Mbps to several hundred Mbps– 11 Mbps is 802.11b which is outdated

Comprehension Check

• Which networking appliance reads frames and sends each frame out only one port

• Switch

• How do switches (typically) know what port to send out a message.

• Switching table

• Can send and receive data simultaneously (term)

• Full-duplex


Comprehension Check

• A special port used to connect switches• Uplink Port

• A wireless device that is similar to a hub• Wireless Access Point (WAP)

• Message sent to the AP when a workstation wants to transmit.

• Request to send (RTS)

• Message sent to workstation from AP indicating it is OK to send the message

• Clear to Send (CTS)


Lab 1.2

• Setup a Basic Network:– One computer per team

– Use a single switch to put them on the same LAN

• To put on same LAN:1. Use Windows search feature to access the “networking and sharing center”

2. Select “Change adapter settings” in the upper left corner.

3. right-click - “Local area connection” and select “properties”

4. Enter password

5. From the Networking tab select

6. “Internet Protocol Version 4 (TCP/IPv4)”

7. Press the “properties” button

8. Set your own IP address by pressing the “use the follo

• Try • IP Address - 192.168.0.1

• Subnet Mask - 255.255.255.0


Section 1.3

NICsPP. 79-88



Network Interface Cards

• Connect computer to medium

• Incoming messages: Receives bit signals and assembles them into frames

• Outgoing messages: receive packets from network protocol– Creates frames by adding MAC addresses and error check

– Converts frame into bit signals and transmits them



A NIC handles incoming data from the network medium



• NIC required to attach to networking medium– Networking medium might be copper wire, fiber-optic cable, or

airwaves

• Most NICs are built into a computer’s motherboard– May use more than one NIC (especially servers)– It is important to know how to install a new NIC



A NIC handles outgoing data to be sent to the network medium


NICs and MAC addresses

All NICs have a unique MAC address

MAC address is stored in read-only memory (ROM) on the NIC

MAC Address = Two 24-bit hexadecimal numbers

– 24-bit manufacturer ID called OUI

– 24-bit serial number assigned by the manufacturer

48-bit address expressed in 12 hexadecimal digits:04-40-31-5B-1A-C4


The NIC as a Gatekeeper

• NIC validates the MAC addresses of incoming frames• Three ways a frame may be accepted by a NIC:

1. Match the MAC address of the NIC

2. Broadcast frame (ff-ff-ff-ff-ff-ff)

3. If NIC is in permiscuous mode

• Unicast Frame – A frame addressed to only one computer on the LAN– When the destination MAC address matches the NICs MAC

address, it’s a unicast frame


The NIC as a Gatekeeper

• Broadcast Frame – A frame designed to be sent to all computers on a network.– Typically: ff-ff-ff-ff-ff-ff

• Promiscuous mode – turns off the gatekeeper functions and enables the NIC to process all frames it sees

• Simulation 5: How a NIC works


NIC Indicator Lights• NICs have indicator lights to show status information

– Usually a link status indicator and an activity indicator

• The link light is usually green when connected to a network

• Some NICs support multiple speeds– Usually a separate light for each speed so that you can determine

at what speed the NIC is connected to the hub or switch– In other cases the light is a different color for each speed, such

as amber for 100 Mbps and green for 1000 Mbps


Selecting a NIC• NICs commonly built into motherboard

• An additional NIC or a faster NIC may need to be installed

• When selecting a NIC you need to select correct bus interface

– PCI-Express is most common

• The NIC driver (software) must be available for your OS

• For servers, consider a NIC with onboard memory and multiple ports that performs faster


NIC Drivers

• Most OSs ship with NIC drivers

• NICs ship with drivers for the most common OSs

– If the OS has a suitable driver available, it is installed automatically

• After installation, Windows 7 shows your installed NIC as a “Network Connection”

• In Windows, each connection is assigned a name as in “Local Area Connection”, “Local Area Connection 2”

– You can rename these

NIC Drivers



Wireless NICs

• Choose Wireless NICs based on the type of wireless AP

• Typical Wireless Standards: 802.11n; 802.11ac

– Older standards: 802.11a, 802.11b, and 802.11g

• Service Set ID (SSID) - the name assigned to the wireless network

• NICS use SSID to join the network.

• Typically need to enter a security key or UID and PSWD

Comprehension Check• What is required to attach a computer to a network• Network Interface Card (NIC)

• What does the NIC do with bit signals coming from network?

• Assembles them into frames

• What identification code is tied to a NIC• MAC address• Three ways a frame may be accepted by a NIC:• Match the MAC address of the NIC

• Broadcast frame (ff-ff-ff-ff-ff-ff)

• If NIC is in permiscuous mode


Comprehension Check

• NIC setting that the gatekeeper functions and enables the NIC to process all frames it sees

• Promiscuous mode

• What color is the link light when successfully connected to a network

• Green

• Consider a NIC with onboard memory and multiple ports that performs faster if the computer is a

• Server

• The name assigned to the wireless network• Service Set ID (SSID)


Lab 1.3

• To Do– Disable integrated NIC and add a new one to a junker– Work with two of the servers in promiscuous mode– Start using Wireshark now– Evaluate “Packet tracer”– Lookup networking symbols

• Should we just use Cisco standards?• Are there other standards we could use?


Section 1.4

RoutersPP. 88-100



Routers

• Most complex networking device

• Connect LANs together to create an internetwork


Routers

• Routers - devices that enable multiple LANs to communicate with one another by forwarding packets from one LAN to another

Routers vs SwitchesRouters Switches

Connect LANS Connect computers within a LAN

IP addresses (Logical) MAC addresses (Physical)

Work with packets Work with frames

Do not forward broadcasts Do forward broadcasts

Use routing tables Use switching tables



Routers Connect LANs

• It is possible to overload a LAN with computers– Broadcast traffic can really affect this

• The next slide shows 3 different groups of users and 3 different servers all connected by switches


Routers Connect LANsSince they are connected by switches, they are all part of the same LAN and all broadcast traffic will be heard by all devices


Routers Connect LANs

• The picture on the next slide shows a better solution for the previous network

• The administrator groups users and servers together based on their department or function


Routers Connect LANsThe router is used to create 3 separate LANs in order to contain broadcast traffic and facilitate more effective communication in each department LAN


Routers Create Broadcast Domains

• The scope of devices to which broadcast frames are forwarded is called a broadcast domain– Each router interface in a network creates another broadcast domain


Routers Work with IP Addresses and Routing Tables

• Routers maintain routing tables composed of IP network addresses and interface pairs to determine where to forward packets on an internetwork



• What happens when a router isn’t connected to the network the packet is addressed to?

• The following slide shows what the routing table would look like on each router between the source and destination networks



• Default route — where to send a packet when the router doesn’t have an entry in its routing table

• Network unreachable — Message sent when the network can’t be found and there is no default route

• Default gateway — the IP address of the computer’s router

• Simulation 6: Router operation in a simple internetwork


Chapter Comprehension Check

• Network repeaters and hubs take incoming bit signals and • repeat those signals out all connected ports

• Switches use _______ ______ to determine which MAC address can be found on which port

• switching tables

• A central device in a wireless network and perform a similar function to hubs

• Access points

• Create and mediate the connection between the computer and network medium

• Network interface cards


Chapter Comprehension Check

• Connect LANs to one another and forward packets from one LAN to another

• Router

• Routers use what address type to route messages between networks

• IP Address

• Unlike hubs and switches, routers do not forward • broadcast frames

• The IP address of the computer’s router• Default Gateway

Comprehension Check

• Used by the router to determine to which network to route packets

• Routing Table

• Where to send a packet when the router doesn’t have an entry in its routing table

• Default route


Lab

• As a class brainstorm labs that may make sense to do here.


guide to networking essentials, 6 th edition chapter 2: network hardware essentials

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