3: connecting to the network

3: Connecting to the NetworkNetworking for Home & Small Business

What’s a Network?• Make a phone call, watching TV, radio,

Internet, Gaming– All depend on a reliable network

• Group of connected devices able to communicate with each other

Networks

Basic Network Components• 4 categories of components

– Hosts– Shared peripherals– Networking devices– Networking media

Hosts– They send & receive data– Have an IP Address

Shared Peripherals– Shared devices that ARE connected to a host

• Rely on their connected hosts to communicate– Print Sharing

Networking devices• Connect hosts

– Hubs, switches, routers• Move & control traffic

Networking media• Connects Devices

Activity

Handout• Complete Handout 1

Client-Server• Hosts have an IP Address

• Hosts can act as a client or server– Depends on software installed

• Server provides services to other hosts– Like providing email or web services

• Clients request & display info from servers

Clients & Servers

Clients & One Server

Popular Client-Server Network• World of Warcraft• Players from all over the world connect &

play

Activity

Peer-to-Peer Networks• One computer can sometimes act as the

server & the client• Simplest: 2 connected devices

– Uses a crossover cable• Multiple PC’s connect with a hub

Peer-to-Peer Networks

• Large businesses have lots of traffic– Dedicated servers to handle requests

Famous Peer-to-Peer• LimeWire

– Exchanging MP3’s with another device

Client, Server, or Both

Physical Topology• Layout/Map of network• Shows where each host is located, wiring,

network devices

Logical Topology• Groups hosts by how they use the network

– Not physical location• Host names, addresses, group info &

applications can be recorded

Lab 3.1.5• Building a Peer-to-Peer Network

End of Part 1

Review• What does SOHO stand for?

– Small office home office• What interconnects hosts & controls traffic?

– Network devices• Which cable connects 2 PC’s together?

– Crossover cable• Hosts are devices that have what?

– IP Addresses• Describe client-server.

Principles of Communication• The Message• Source or

Sender• Destination or

Receiver• Channel or

Pathway• Protocol or

Rules

Human Communication• What are our rules of communication?

Protocols• Rules of Communication over a medium• Protocols define the details of how the

message is transmitted, and delivered. • This includes issues of:

Message Encoding• Encoding

• Converting thoughts into words• Describing the sunset

• Bits are encoded for that medium• Light, electricity, or radio waves

• Destination will decode the message

Message Format Delivery

Encapsulation of Data• Computer messages packed in a FRAME

– Acts like an envelope– Provides the addresses– Must be properly addresses or won’t be

delivered

Handout• Complete Handout 2 & 3• Message Format Ordering

Review• What 4 things do you need for

communication?– Source, destination, channel, protocol

• Describe encoding.– Bits into electricity, light, or radio waves

• A message is encapsulated in what?– Frame

• Which 2 address are in the frame?– Source & destination MAC address

What We Talked About So Far

Message Size• You talk in sentences.

– Length will vary depending on what can be processed or understood by the listener

• Messages sent across networks are broken into smaller pieces– Size of a frame

Message Timing• People use timing to determine when to

speak, how fast or slow to talk, and how long to wait for a response. These are the rules of engagement.

• Access Method• Flow Control• Response Timeout

Message Timing• Access Method

– When to begin sending & how to respond to errors

– Collision if two talk at same time• Flow Control

– Sender can transmit messages faster than the destination can receive & process

– Use flow control to negotiate correct timing for successful communication

• Response Timeout– How long to wait for responses & what to do

Unicast Message Pattern• Unicast

– 1 to 1 single message

Multicast Message Pattern• Multicast

– 1 to a group message

Broadcast Message Pattern• Broadcast

– 1 to all

Activity

Review• What is it called when one message format

is placed in another message format?– Encapsulation

• Bob is talking to Sally. Which type of message pattern is this?– Unicast

• Which address is used in a frame?– MAC address (source & destination)

Review• Which message is one to all?

– Broadcast

Importance of Protocols• Computers need rules to communicate• Local network devices MUST speak same

language• Most common wired protocol is

ETHERNET

Early Days of Computing• Each vendor had their own rules• Standards had to be created

Standardizing• IEEE maintains standards approvals

– Assigned a #– 802.3 is Ethernet– 100Base-T

• 100 megabit Ethernet• Baseband Transmission• Twisted Pair Cabling

Physical Addressing• Remember encapsulating frames?

– Source & destination address needed• Each host on Ethernet has a physical

address (MAC Address)– Burned into NIC

• NIC encapsulates source & dest. MAC• Host that receives frame reads dest. MAC

– If it contains its own MAC, it will process it– If not, it ignores it

Example

Lab 3.3.3• Determine the Mac Address• Ipconfig /all

Ethernet Frame Structure• Frames are also called PDU’s

– Protocol Data Units– 64-1518 bytes each frame

– Preamble for timing– SFD is end of timing, begin frame– FCS- helps check for damaged frames

Activity

MAC & IP- Happy Together!IP MAC

MAC

Hierarchical Design Structure• MAC Address is like your name

– Doesn’t tell where you are on the network– Not efficient by itself– Imagine if all hosts on Internet could only be

identified by a MAC address• Ethernet is a broadcast technology

– Sent to all in a network– Too much traffic & collisions, slows network

• Separate into smaller networks

Hierarchical in Life

Hierarchical Design in Networks• Dividing your network into smaller groups or

layers– Keeps local traffic local– Only data intended for other networks will move on to

other layers• Access Layer

– Provides connections to hosts in a local Ethernet network.

• Distribution Layer– Interconnects the smaller local networks.

• Core Layer– A high-speed connection between distribution layer

devices.

3 Layer Model

Access Layer• Hosts/Clients connect to hubs/switches• Local segmented networks

Distribution Layer• Routers• Routing occurs• Traffic delivered to other local networks• Security (ACL)

Core Layer• High-speed backbone• Redundant paths• Powerful routers/switches

– Just sends the data– No changes here

Goals of 3 Layer Model• Think how you can limit traffic from going to

where it doesn’t need to be– Less collisions– More efficient data paths– Better placement of devices

Radio File Storage Server

Teacher File Server- GCIT

PowerSchool Server

IP Addressing• Your name doesn’t change but where you

live might– MAC stays on NIC– Doesn’t change no matter where you move

• IP Address is like your address– It is logical, not physical

• Needed to go beyond your network– Stay local or go elsewhere???

IP Addressing• 2 parts

– Identify the network– Identify the host

• Network portion is same for all devices on a local network

• 209.120.5.72

IP Network Example

Lab 3.3.6• Determine the IP Address of the Computer• Let’s do this together

• How do we find the IP Address through the command prompt?– Ipconfig /all

• Why is an IP address important?

Handout• 3 Layer Model & Addressing Activity

Review1. What is the process of placing one format

into another (like a letter into an envelope to be sent in the mail)?

– Encapsulation2. Which device is typically at the

Distribution Layer?– Router

3. When a PC receives a message, which address is used to determine if it for that PC?

– Destination MAC

Review1. Which organization creates & maintains

the standards?– IEEE– Why?

2. A frame contains which 2 addresses?– Source & Destination MAC

3. What does FCS stand for & what does it do?

– Frame Check Sequence, checks for errors

Hubs• At Access Layer• Simple Device (DUMB)

– Message in one port, out all others– Does not send to specific device– Sends one message at a time

• Collisions can occur• They wait for silence, & then resend randomly• Too many collisions slow the network• Keep these collision domains SMALL

Pictures of Hubs

Hub Example

Hub & Collision Domain

Handout• Hubs

Switches• Access Layer• Connects multiple hosts like a hub

– Forwards a message to a specific host!– Reads the destination MAC

• Has a MAC address table– Ports & MAC addresses on them

• Creates a virtual circuit to destination• No bandwidth sharing between hosts• No collisions!

How a switch works

More about Switches…• What if destination MAC is NOT in the

table?– Floods message out all ports, except one it

came in on– Compare the destination MAC in frame– Correct one processes the message

Switch Table• How does the switch add the MAC address

to its table?– It examines the source MAC & port it came in

on– When it responds to a message, it adds it

• Updates table for every message

Example• Go to Slide 3.4.3-2

• Look at example

What else about Switches?• Hub attached to switch port scenario • Separate collision domains for each switch port

Switch Handout

Review1. Hubs & Switches are at which design

layer?– Access Layer

2. Which device creates a virtual circuit from the source to destination?

– Switch3. Which device sends data in one port &

out all ports regardless of the destination?– Hub

Review1. Which address does a NIC read when

deciding if the message is for itself?– Destination MAC

2. In 100Base-T, what does the 100 mean?– 100Mbps– How about the T?

• Twisted Pair Cabling

3. If a switch receives a frame & doesn’t have the dest. MAC in its table, what happens?

– Floods it out all ports, except one it came in on

Broadcasts• One host can send messages to all other

LOCAL hosts– Find info from others– Tell others something

• One destination MAC in a frame only– There’s a special MAC address that all hosts

will receive & process– 48 bits, all binary 1’s– In hexadecimal, FF:FF:FF:FF:FF:FF

• Look at 3.4.4

Broadcast Domain• Too many hosts in a domain, causes traffic

backup– This is why you divide into smaller LAN’s

Let’s Practice Together• Slide 3.4.5

MAC & IP• What if you want to send data, but only know their

IP address and not their MAC?– ARP (Address Resolution Protocol)

ARP• Host sends out a broadcast frame w/ the IP

address of the destination host– FF:FF:FF:FF:FF:FF

• Each host receives & compares the IP address to see if it is their own

• Matching host sends its MAC address back to source

• Source then adds it to its ARP table• Then it can send the message

ARP Example

ARP Example

Review1. A broadcast frame contains which MAC

address?– All F’s

2. How many bits is a MAC address?– 48

3. Describe a broadcast4. What separates broadcasts?

Distribution Layer• Separates & connects your small networks

– Connects your Access Layer networks– Can filter traffic & provide security

Routers• Distribution Layer• Connects different local networks• Reads the packet encaps. in frame

– Destination IP Address (network portion)– Subnet Mask

• Finds best path to that destination network

Routers- The Path…• Each port connects a different local

network• Rips open to find destination IP• Looks in Routing Table

– In the table:• Encapsulates in new frame• Sends it out port towards or connected to that

destination• Routers DO NOT forward broadcasts!

Path Example- H1 to H4

Default Gateway• When sending a message on your local

network you use ARP to find dest. MAC• When sending a message on another

network– You encapsulate:

• Source IP • Source MAC• Destination IP• You don’t know the destination MAC!• So you include the MAC of the router port!• Router will receive & process this MAC, BUT NOT

THE ARP MAC broadcast!

Default Gateway• This IP is set in TCP/IP settings• Router port that your host connects to- same local

network– If the host knows the IP, it will use ARP to find out the

MAC address on router port

– Example on next slide

Default Gateway

Default Gateway

Lab• Complete 3.5.3-2

Routing Tables• Networks & best path to reach them• Knows this info by:

– Dynamically learned from other routers– Manually entered by admin

• No route in table?– Drop it OR– Default Route is set by admin

Routing Tables

Where does data go?• Directly to the network destined for• To another router

• When router forwards the frame, it MUST include a destination MAC– If it is connected, it will use the dest MAC from

its ARP table– If not, it will sub MAC address of connected

router’s port• ARP table for each port/local network

Look at…• 3.5.4.2• 3.5.4.3 activity

LAN• Network over a small area

– Under one administration– Router will separate

How many local networks?

Adding hosts to a LAN• Advantages/Disadvantages?

Adding hosts to a LAN• Advantages/Disadvantages?

Planning a Network• Ethernet is most popular• Planning is key!• First, gather this info:

– The number & type of hosts to be connected– The applications to be used– Sharing & Internet connectivity requirements– Security & privacy considerations– Reliability & uptime expectations– Connectivity requirements including, wired and

wireless

Plan & Document• Maps of topology• Physical environment

– Temperature– Power

• Physical configuration– Location of network devices– Length of cables– Hardware config

• Logical Configuration– Broadcast & collision domains– IP & Naming Scheme

Physical Topology• How many broadcast, collision & networks?

Review1. Describe a default gateway.2. Each router port has an _______ table

that hold the MAC addresses of devices connected to each port.

– ARP3. Which one device will separate or

segment a network?– Router

4. Describe a routing table.

Multifunction Devices• Integrated Routers

– Usually for SOHO– Switch/router/access point in one– Single point of failure

• Cisco ISR– Separate components to add/replace

Linksys

Linksys

Connecting the Linksys• All connected to switch ports MUST be in

same IP network to communicate

• Display IP configuration settings– Ipconfig– Ipconfig /all

Lab• 3.6.4

Sharing Resources• XP has simple file sharing

– You can set more specific– Full Control– Modify– Read & Execute– List Folder Contents– Read– Write

• Look at 3.6.5

3: Connecting to the NetworkNetworking for Home & Small Business