Fundamentals of NetworkingDiscovery 1, Chapter 3Connecting to the Network

Objectives•Explain the concept of networking and the benefits

of networks.•Explain the concept of communication protocols.•Explain how communication occurs across a local

Ethernet network.•Describe Access Layer devices and communication

methods on a local Ethernet network.•Describe Distribution Layer devices and

communication methods across networks.

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

Communication Now•OLD: ▫Separate, dedicated networks for voice, data, vide

•NOW: ▫Converged into one over a single channel▫Can you name examples?

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 ARE connected to a host▫Rely on their connected hosts to share▫Software allows the sharing

•Print sharing with a USB connected printer

Networking devices•Connect hosts & other devices▫Hubs, switches, routers

•Move & control network traffic

Networking media•Connects Devices▫Can be wired or wireless

Activity

Handout•Complete Handout 1

Computer Roles in a Network• Host sends & receives data on a network▫Computer is a host▫Can act as a client and/or a server

• Server▫Provide info to other hosts on a network▫Simultaneously ▫Email, web pages, file access

Separate server software for each• Client▫Requests & displays info from the server▫Can check email & view web at same time

Web browser/IE, Outlook

Activity

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

Popular Client-Server Network

•World of Warcraft•Players from all over the world connect & play

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

as the server & the client• Simplest: 2 connected devices▫Uses a crossover cable or wireless

•Multiple PC’s connect with a hub• Disadvantage▫Host can slow down if doing both

• Not for large networks▫Dedicated servers to handle

requests

Peer-to-Peer Networks

Famous Peer-to-Peer• LimeWire▫Exchanging MP3’s with

another user▫Only connected with

that ONE user

Client, Server, or Both

Lab 3.1.5•Building a Peer-to-Peer Network

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

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

Rules of Human Communication•What are some of our rules of communication?▫What if there were no rules?

Protocols•Rules of Communication over a medium▫May be different depending on the medium

•Protocols define the details of how the message is transmitted and delivered

•This includes issues of:

Message Encoding• Encoding

• Converting thoughts into words• Bits are encoded for that

medium Light, electricity, or radio waves

• Destination will decode the message

Message Format for 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)?▫ Encapsulation

2. 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 Layer2. Which device creates a virtual circuit from the

source to destination?▫ Switch

3. 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 Cabling3. 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’s2. How many bits is a MAC address?

▫ 483. 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.▫ ARP

3. 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