Connecting to the Network

© 2007 Cisco Systems, Inc. All rights reserved. Cisco PublicITE PC v4.0Chapter 1 1

Connecting to the Network

Networking for Home and Small Businesses – Chapter 3

ITE PC v4.0Chapter 1 2© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public

What is a network?

The ability to connect people and equipment no matter where they are in the world.

– telephone

– computers

– television

How does your body work as a network??


Networking and Its BenefitsA CONVERGED NETWORK!!!


Networking and Its Benefits

SOHO Network– Small Office/Home Office

– sharing of resources

• Internet

• Printer


Networking and Its Benefits

Schools, Corporations

Internet


Networking and Its Benefits Define the components of an Information network

Hosts– PCs

– send and receive information across the network

–connected to a network device

Peripherals– not directly connected to the network, but connected to hosts

Network devices– hub, switch, router

Network media– used to connect hosts/devices


Networking and Its Benefits Clients and servers

– software installed determines the role of a client or a server

Server software– enables the server to provide information to other hosts

Client software– enables the client to request and display information from the server

– Example: Internet Explorer


Networking and Its Benefits Build computer peer-to-peer network and verify

The ability to act as both a client and server


Network Topologies Physical topology

– created to record where each host is on the network

– shows how each host is connected (media, devices, etc)


Network Topologies Logical topology

– how the host uses the network

– host names, addresses, groups, applications


Communication Protocols Primary purpose of a network – to communicate

Elements of communication– Sender (source)

• has a need to communicate

– Receiver (destination)

• receives message and interprets it

– Channel

• pathway for information to travel


Successful delivery of the message

Rules (protocols) must be followed:– Identification of the sender and/or receiver

– Channel in which to communicate (face-to-face)

– Mode of communication (written or spoken)

– Language

– Grammar

– Speed or timing


Communication Protocols Encoding vs. Decoding

Encoding – Humans

• converting thoughts into language, symbols, or sounds

– Computers

• messages converted into bits by sending host

• each bit encoded into sound, light, or electrical impulses

• destination host then decodes the signal

Decoding– reverse of encoding


Communication Protocols Message formatting and encapsulation

Message needs a specific format

Compare to parts of a letter– Identifier (recipient)

– Salutation

– Message

– Closing

– Identifier (sender)

Encapsulation– placing the letter into the envelope

De encapsulation– letter removed from the envelope


Communication Protocols Messages have size restrictions depending on the

channel used

If the message is broken into smaller pieces, it is easier to understand

If the message is too long or too short, will be considered undeliverable.


Communication Protocols Timing

– when to speak; how fast or how slow

– how long to wait for a response

Access Method– determines when someone is able to send a message

– can speak when no one else is talking, otherwise a COLLISON occurs

Flow Control– timing for negotiations

– sender might transmit messages faster than the user can handle

Response Timeout– how long should you wait for a response and what action to take

Acknowledgment– may be required to ensure message was delivered


Communication Protocols Message Patterns

Unicast – single destination

Multicast – same message to a group

Broadcast – all hosts need to receive the message


Communication Protocols

PROTOCOLS = RULES TO FOLLOW


Communication Across a Local Ethernet Network Computers must speak the same language in order to

communicate!!


Standards in technology

Standards – rules by which equipment from different vendors operate

Benefits of standards:– Facilitate design

– Simplify product development

– Promote competition

– Provide consistency

– Facilitate training

– More vendor choices for customers


Communication Across a Local Ethernet Network IEEE (Institute of Electrical and Electronic Engineers)

– maintains networking standards

– 802.3 – Ethernet standard

A breakdown of terminology– 100 Base-T

– 100 = Speed in Mbps

– Base = Baseband transmission

– T = Twisted Pair


Communication Across a Local Ethernet Network Physical addressing

MAC address (Media Access Control)

Ethernet communication– each interface has a MAC address

– each device may look at the data, but only the interface that matches the destination MAC will respond


The Ethernet Frame Preamble – beginning of the timing

SFD (Start Frame Delimiter) – marks the end of the timing, but beginning of the frame

Destination MAC

Source MAC

Length/Type– Length – tells which protocol receives the data

– Type – number of bytes of data

Encapsulation – packet of information

FCS (Frame Check Sequence) – checks for damaged frames


The Hierarchical Design Structure Smaller, more manageable groups allow traffic to

remain local on the networks

Divided into three layers– Access Layer

• connection to the hosts

– Distribution Layer

• interconnects smaller networks

– Core Layer

• high speed connection between

distribution devices


Logical Addressing MAC vs. IP

IP Address (Logical Address)

– assigned based on where the host is located

– assigned by the administrator

Parts of an IP address

– Network – same for all hosts connected to the LAN

– Host – unique to each host on the network


Access Layer Devices Most basic level

Made up of:– host devices

– first line of networking devices

– hub, switch, workstations


Access Layer Device – A HUB

Accepts data signal from one port and sends it (regenerates) out all ports

– multiport repeater

Collisions– results in message being garbled and unreadable

– occur when two or more hosts send a message at the same time (undesirable in a network)

NOT VERY SMART– a hub will not recognize there is a collision and send it all ports


Hubs And Collision Domains Collision domain – area where the collision has

occurred.

More collision domains = better performance

How many collision domains exist in the graphic shown?


Access Layer Device – A SWITCH

SMARTER THAN A HUB dedicated bandwidth out each port

no need to share with other ports (unlike a hub)

Can forward messages to a specific host by looking in its MAC table

If destination MAC is not in its MAC table, floods the network out all ports looking for a response

Only the host with the correct MAC address will respond


More Stuff on Switches

How does the MAC table get built?– keeps track of frames being sent between hosts

– records the information when there is a response

Collision Domains– each port on a switch is its own collision domain

– 8 port switch = 8 collision domains

Online Activity 3.4.3


Broadcasts If there is only one destination MAC in a message, how

can you contact everyone else?– send a broadcast MAC

– hexidecimal digits

– FFFF.FFFF.FFFF

Useful when hosts need to send information but don’t know what hosts are to receive it

Switches and hubs send the broadcast out to everyone on their network. (Broadcast Domain)

ONLINE ACTIVITY 3.4.5


ARP Request

Sent when the sending host knows the destination IP, but not the MAC

Will discover the MAC address of any local host on the network


Distribution Layer Devices and Communication Methods

Responsible for making sure local traffic stays local on the network

Traffic destined for other networks will be passed on.


Distribution Layer Devices—The Router Routers – directs traffic based on the destination IP

address

Routers build routing tables; switches build MAC tables

Routers decode packets, switches decode frames

Look only the network portion of the IP address– finds the best path to take to get to the destination

Routers do not forward broadcasts!!!


Default Gateway Used when a host wants to send data to a host on a

different network.

Must be set on the workstation connected to the routing device – the router interface connected to the PC

Activity 3.5.3


Routing Tables and ARP tables Used by routers to store information


Types of Routing

Dynamic – information is obtained from neighboring routers

Static– manually entered by the network administrator

What happen to a message that is not in the routing table?– It is dropped unless . . .

A default route is set– “last resort” type of router

– will send it to the router it thinks may be have the destination IP

ONLINE ACTIVITY 3.5.4


Distribution Layer Devices and Communication Methods LAN – Local Area Network

Under the same administrative control


Distribution Layer Devices and Communication Methods Packet Tracer


Plan, Implement and Verify a Local Network Consider the following before beginning:

– Number and type of hosts

– Applications to be run on the network

– Data and devices to be shared

– Speed requirements (bandwidth)

– Level of security

– Reliability of the network

– Connectivity requirements


Building the Network Physical environment

– temperature control

– availability/placement of outlets

Physical configuration– location of devices

– how are devices connected

– location/length of cable runs

– hardware configurations (hosts, servers)

Logical configuration– size of broadcast & collision domains

– IP addressing scheme

–Naming

–Permissions

–Sharing


Multifunction Devices Integrated routers

– Linksys wireless router

– problem = single point of failure

Cisco Integrated Services Router (ISR)– performs services of three different devices

• router

• switch

• wireless access point


Implement and Document the Network Develop a prototype

– tests network design

PACKET TRACER – ACTIVITY 3.6.2


Sharing Resources Main reason for networking – sharing resources

– File sharing

– Print sharing

Consider this before sharing:– security issues

– permissions granted

Windows XP users– use Simple File Sharing


Documents

Connecting to the Network