sub netting - apjohns0 ch01-where we've been
TRANSCRIPT
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
1/50
Application
Presentation
Session
Transport
Network
Data-Link
Physical
THE OSI MODEL
Where Weve Been
Chapter 1Review
By: Allan Johnson
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
2/50
Table of Contents
Enterprise
Review the OSI Model
Encapsulation
LAN Devices & Technologies
Transport Layer
IP Addressing
Go There!Go There!
Go There!Go There!
Go There!Go There!
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
3/50
A New Word!Enterprise
A corporation, agency,
school, or other
organization that worksto tie together its data,
communication,
computing, and file
servers.
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
4/50
Your Job as a Network Guru
Help Enterprises meet their needs by: Interconnecting their LANs so that
geographically remote services can beaccessed
Ensuring users get high bandwidth accessover their LANs (i.e. Replacing hubs withswitches; 10Mbps NICs with 10/100 MbpsNICs or Gigabit per second NICs)
Implementing new technologies as theyemerge like e-commerce, videoconferencing, voice over IP, and distancelearning.
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
5/50
Application
Presentation
Session
Transport
Network
Data-Link
Physical
THE OSI MODEL
Review The Model
Open SystemsInterconnected Reference
Model
Table of Contents
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
6/50
Why A Layered Model?
Reduces complexity Standardizes interfaces
Facilitates modular
engineering Ensures interoperable
technology
Accelerates evolution
Simplifies teaching &learning
Application
Presentation
Session
Transport
Network
Data-Link
Physical
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
7/50
Host Layers vs. Media Layers
Application
Presentation
Session
Transport
Network
Data-Link
Physical
Host LayersProvides accuratedata deliverybetween computers
Application
Presentation
Session
Transport
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
8/50
Host Layers vs. Media Layers
Application
Presentation
Session
Transport
Network
Data-Link
Physical
Media LayersControls physicaldelivery of the messageover the network
Network
Data-Link
Physical
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
9/50
Application Layer
Provides network services(processes) to applications.
For example, a computer ona LAN can save files to aserver using a networkredirector supplied by NOSslike Novell.
Network redirectors allowapplications like Word andExcel to see the network.
Application
Presentation
Session
Transport
Network
Data-Link
Physical
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
10/50
Presentation Layer
Provides data representationand code formatting.
Code formatting includescompression and encryption
Basically, the presentationlayer is responsible forrepresenting data so that the
source and destination cancommunicate at theapplication layer.
Application
Presentation
Session
Transport
Network
Data-Link
Physical
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
11/50
Session Layer
Provides inter-host communicationby establishing, maintaining, andterminating sessions.
Session uses dialog control anddialog separation to manage the
session Some Session protocols:
NFS (Network File System)
SQL (Structured Query Language)
RCP (Remote Call Procedure)
ASP (AppleTalk Session Protocol)
SCP (Session Control Protocol)
X-window
Application
Presentation
Session
Transport
Network
Data-Link
Physical
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
12/50
Transport Layer
Provides reliability, flow control,and error correction through theuse of TCP.
TCP segments the data, adding aheader with control information
for sequencing andacknowledging packets received.
The segment header also includessource and destination ports forupper-layer applications
TCP is connection-oriented anduses windowing.
UDP is connectionless. UDP doesnot acknowledge the receipt of
packets.
Application
Presentation
Session
Transport
Network
Data-Link
Physical
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
13/50
Network Layer
Responsible for logicallyaddressing the packet andpath determination.
Addressing is done through
routed protocols such as IP,IPX, AppleTalk, and DECnet.
Path Selection is done byusing routing protocols such
as RIP, IGRP, EIGRP, OSPF,and BGP.
Routers operate at theNetwork Layer
Application
Presentation
Session
Transport
Network
Data-Link
Physical
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
14/50
Data-Link Layer
Provides access to the media
Handles error notification,network topology issues, andphysically addressing the
frame.
Media Access Control througheither...
Deterministictoken passing Non-deterministicbroadcast
topology (collision domains)
Important concept: CSMA/CD
Application
Presentation
Session
Transport
Network
Data-Link
Physical
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
15/50
Physical Layer
Provides electrical,mechanical, procedural andfunctional means foractivating and maintaining
links between systems. Includes the medium throughwhich bits flow. Media canbe...
CAT 5 cable Coaxial cable
Fiber Optics cable The atmosphere
Application
Presentation
Session
Transport
Network
Data-Link
Physical
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
16/50
Application
Presentation
Session
Transport
Network
Data-Link
Physical
THE OSI MODEL
Encapsulation
Peer-to-PeerCommunications
Table of Contents
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
17/50
Peer-to-Peer Communications
Peers communicate using the PDU of theirlayer. For example, the network layers of thesource and destination are peers and usepackets to communicate with each other.
Application Application
Presentation Presentation
Session Session
Transport TransportNetwork Network
Data-Link Data-Link
Physical Physical
Data
SegmentsPacketsFrames
Bits
DataData
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
18/50
Encapsulation Example
You type an emailmessage. SMTP takes thedata and passes it to thePresentation Layer.
Presentation codes thedata as ASCII.
Session establishes a
connection with thedestination for the purposeof transporting the data.
Application
Presentation
Session
Transport
Network
Data-LinkPhysical
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
19/50
Encapsulation Example
Transport segments thedata using TCP and hands itto the Network Layer foraddressing
Network addresses thepacket using IP.
Data-Link then encaps. thepacket in a frame and
addresses it for localdelivery (MACs)
The Physical layer sends thebits down the wire.
Application
Presentation
Session
Transport
Network
Data-LinkPhysical
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
20/50
Application
Presentation
Session
Transport
Network
Data-LinkPhysical
THE OSI MODEL
LAN Devices &
TechnologiesThe Data-Link &Physical Layers
Table of Contents
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
21/50
Devices
What does it do? Connects LAN
segments;
Filters traffic based
on MAC addresses;and
Separates collisiondomains based upon
MAC addresses.
What layer device?
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
22/50
Devices
What does it do? Since it is a multi-port
bridge, it can also Connect LAN
segments;
Filter traffic based onMAC addresses; and
Separate collisiondomains
However, switches
also offer full-duplex,dedicated bandwidthto segments ordesktops.
What layer device?
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
23/50
Devices
What does it do? Concentrates LAN
connections frommultiple devices into
one location Repeats the signal (a
hub is a multi-portrepeater)
What layer device?
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
24/50
Devices
What does it do? Interconnects networks
and provides broadcastcontrol
Determines the path
using a routing protocolor static route
Re-encapsulates thepacket in the appropriateframe format and
switches it out theinterface
Uses logical addressing(i.e. IP addresses) todetermine the path
What layer device?
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
25/50
Media Types
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
26/50
LAN Technologies
Three MostCommon UsedToday inNetworking
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
27/50
Ethernet/802.3
Cable Specifications: 10Base2
Called Thinnet; uses coax
Max. distance = 185 meters (almost 200)
10Base5 Called Thicknet; uses coax
Max. distance = 500 meters
10BaseT Uses Twisted-pair
Max. distance = 100 meters
10 means 10 Mbps
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
28/50
Ethernet/802.3
Ethernet is broadcast topology. What does that mean?
Every devices on the Ethernet segment seesevery frame.
Frames are addressed with source anddestination ______ addresses.
When a source does not know the destination orwants to communicate with every device, it
encapsulates the frame with a broadcast MACaddress: FFFF.FFFF.FFFF
What is the main network traffic problemcaused by Ethernet broadcast topologies?
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
29/50
Ethernet/802.3
Ethernet topologies are also sharedmedia.
That means media access is controlled
on a first come, first serve basis. This results in collisions between the
data of two simultaneously transmitting
devices. Collisions are resolved using what
method?
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
30/50
Ethernet/802.3
CSMA/CD (Carrier Sense Multiple Access withCollision Detection)
Describe how CSMA/CD works: A node needing to transmit listens for activity on
the media. If there is none, it transmits. The node continue to listen. A collision is detected
by a spike in voltage (a bit can only be a 0 or a 1--itcannot be a 2)
The node generates a jam signal to tell all devices
to stop transmitting for a random amount of time(back-off algorithm).
When media is clear of any transmissions, the nodecan attempt to retransmit.
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
31/50
Address Resolution Protocol
In broadcast topologies, we need a way toresolve unknown destination MAC addresses.
ARP is protocol where the sending devicesends out a broadcast ARP request which
says, Whats you MAC address? If the destination exists on the same LAN
segment as the source, then the destinationreplies with its MAC address.
However, if the destination and source areseparated by a router, the router will notforward the broadcast (an important functionof routers). Instead the router replies with its
own MAC address.
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
32/50
Application
Presentation
Session
Transport
Network
Data-LinkPhysical
THE OSI MODEL
Transport Layer
A Quick Review
Table of Contents
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
33/50
Transport Layer Functions
Synchronization of the connection Three-way handshake
Flow Control
Slow down, youre overloading my memorybuffer!!
Reliability & Error Recovery
Windowing: How much data can I sendbefore getting an acknowledgement?
Retransmission of lost or unacknowledgedsegments
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
34/50
Transports Two Protocols
TCP Transmission Control
Protocol
Connection-oriented
Acknowledgment &Retransmission ofsegments
Windowing
Applications: Email
File Transfer
E-Commerce
UDP User Datagram
Protocol
Connectionless
NoAcknowledgements
Applications: Routing Protocols
Streaming Audio Gaming
Video Conferencing
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
35/50
Application
Presentation
Session
Transport
Network
Data-LinkPhysical
THE OSI MODEL
IP Addressing
Subnetting Review
Table of Contents
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
36/50
Logical Addressing
At the network layer, we use logical,hierarchical addressing.
With Internet Protocol (IP), this address is a32-bit addressing scheme divided into four
octets. Do you remember the classes 1st octets
value? Class A: 1 - 127
Class B: 128 - 191 Class C: 192 - 223
Class D: 224 - 239 (multicasting)
Class E: 240 - 255 (experimental)
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
37/50
Network vs. Host
N H H HClass A:27 = 126 networks; 224 > 16 mill ionhosts
N N H HClass B : 214 = 16,384 networks; 216 > 65,534 hosts
N N N HClass C : 221 > 2 million networks; 28 = 254hosts
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
38/50
Why Subnet?
Remember: we are usually dealing witha broadcast topology.
Can you imagine what the network
traffic overhead would be like on anetwork with 254 hosts trying todiscover each others MAC addresses?
Subnetting allows us to segment LANsinto logical broadcast domains calledsubnets, thereby improving networkperformance.
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
39/50
Stealing /Borrowing Host Bits
In order to subnet, we must steal or borrowbits from the host portion on the IP address.
First, we must to determine how manysubnets we need and how many hosts per
subnet. We do this through the power of 2
For example, I need 8 subnets from a Class C: 24 = 16 - 2 = 14 subnets
Remember: we subtract 2 because these subnets are notused
How many host do we have? Its a Class C, so 4 bits are left: 24 = 16 - 2 = 14 hosts
Remember: we subtract 2 because one address is the
subnet address and one is the broadcast address
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
40/50
Subnet Mask
We determine the subnet mask by adding upthe decimal value of the bits we borrowed.
In the previous Class C example, we borrowed4 bits. Below is the host octet showing the bits
we borrowed and their decimal values.
128 64 32 16 8 4 21
1 1 1 1
We add up the decimal value of these bits and get 240.Thats the last non-zero octet of our subnet mask.
So our subnet mask is 255.255.255.240
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
41/50
Last Non-Zero Octet
Memorize this table. You should be able to: Quickly calculate the last non-zero octet when giventhe number of bits borrowed.
Determine the number of bits borrowed given thelast non-zero octet.
Determine the amount of bits left over for hosts andthe number of host addresses available.
Bits
Borrowed
Non-Zero
Octet Hosts
2 192 623 224 30
4 240 14
5 248 6
6 252 2
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
42/50
CIDR Notation
Classless Interdomain Routing is a method ofrepresenting an IP address and its subnetmask with a prefix.
For example: 192.168.50.0/27
What do you think the 27 tells you? 27 is the number of 1 bits in the subnet mask.
Therefore, 255.255.255.224
Also, you know 192 is a Class C, so we borrowed 3
bits!! Finally, you know the magic number is 256 - 224 =32, so the first useable subnet address is197.168.50.32!!
Lets see the power of CIDR notation.
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
43/50
202.151.37.0/26
Subnet mask? 255.255.255.192
Bits borrowed? Class C so 2 bits borrowed
Magic Number? 256 - 192 = 64
First useable subnet address? 202.151.37.64
Third useable subnet address? 64 + 64 + 64 = 192, so 202.151.37.192
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
44/50
198.53.67.0/30
Subnet mask? 255.255.255.252
Bits borrowed? Class C so 6 bits borrowed
Magic Number? 256 - 252 = 4
Third useable subnet address? 4 + 4 + 4 = 12, so 198.53.67.12
Second subnets broadcast address? 4 + 4 + 4 - 1 = 11, so 198.53.67.11
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
45/50
200.39.89.0/28
What kind of address is 200.39.89.32? Class C, so 4 bits borrowed
Last non-zero octet is 240
Magic number is 256 - 240 = 16
32 is a multiple of 16 so 200.39.89.32 is asubnet address--the second subnetaddress!!
Whats the broadcast address of200.39.89.32? 32 + 16 -1 = 47, so 200.39.89.47
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
46/50
194.53.45.0/29
What kind of address is 194.53.45.26? Class C, so 5 bits borrowed Last non-zero octet is 248 Magic number is 256 - 248 = 8
Subnets are .8, .16, .24, .32, ect.
So 194.53.45.26 belongs to the third subnetaddress (194.53.45.24) and is a host address.
What broadcast address would this host use
to communicate with other devices on thesame subnet? It belongs to .24 and the next is .32, so 1 less is .31
(194.53.45.31)
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
47/50
No Worksheet Needed!
After some practice, you should never need asubnetting worksheet again.
The only information you need is the IPaddress and the CIDR notation.
For example, the address 221.39.50/26
You can quickly determine that the firstsubnet address is 221.39.50.64. How?
Class C, 2 bits borrowed 256 - 192 = 64, so 221.39.50.64
For the rest of the addresses, just do multiplesof 64 (.64, .128, .192).
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
48/50
The Key!!
MEMORIZE THIS TABLE!!! Or Know howto recreate/derive it!!!!
Bits
Borrowed
Non-Zero
Octet Hosts
2 192 62
3 224 30
4 240 14
5 248 66 252 2
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
49/50
Practice On Your Own
Below are some practice problems. Take outa sheet of paper and calculate... Bits borrowed
Last non-zero octet
Second subnet address and broadcast address1. 192.168.15.0/26
2. 220.75.32.0/30
3. 200.39.79.0/29
4. 195.50.120.0/275. 202.139.67.0/28
1. Challenge: 132.59.0.0/19
2. Challenge: 64.0.0.0/16
Answers
-
8/2/2019 Sub Netting - Apjohns0 Ch01-Where We'Ve Been
50/50
Answers
Address ClassBits
BorrowedLast Non-Zero Octet
SubnetJump
2nd Subnet'sAddress
2nd Subnet'sBroadcast
192.168.15.0/26 C 2 192 64 192.168.15.128 192.168.15.191
220.75.32.0/30 C 6 252 4 220.75.32.8 220.75.32.15
200.39.79.0/29 C 5 248 8 200.39.79.16 220.39.79.23195.50.120.0/27 C 3 224 32 195.50.120.64 195.50.120.95
202.139.67.0/28 C 4 240 16 202.139.67.32 202.139.67.47
132.59.0.0/19 B 3 224 32 132.59.64.0 132.59.95.255
64.0.0.0/16 A 8 255 1 64.2.0.0 64.2.255.255
Challenge:
Dont Cheat Yourself!! Work them out before you check your answers. Clickthe back button if youre not done. Otherwise, clickanywhere else in the screen to see the answers.
Back