Institute of Technology, Sligo Dept of Computing Application Presentation Session Transport Network...

Institute of Technology,Sligo Dept of Computing

Application

Presentation

Session

Transport

Network

Data-Link

Physical

THE OSI MODEL

Semester 3 Semester 3 Chapter 1Chapter 1

ReviewReview

Table of ContentsTable of Contents

Review the OSI ModelReview the OSI Model

LAN Devices & LAN Devices & TechnologiesTechnologies

IP AddressingIP Addressing

CIDR NotationCIDR Notation

RoutingRouting

Transport LayerTransport Layer


Application

Presentation

Session

Transport

Network

Data-Link

Physical

THE OSI MODEL

Review The ModelReview The Model

Open Systems Open Systems Interconnected Reference Interconnected Reference

ModelModel

Why A Layered Model?Why A Layered Model?

Reduces complexityReduces complexity Standardizes interfacesStandardizes interfaces Facilitates modular Facilitates modular

engineeringengineering Ensures interoperable Ensures interoperable

technologytechnology Accelerates evolutionAccelerates evolution Simplifies teaching & learningSimplifies teaching & learning

Application

Presentation

Session

Transport

Network

Data-Link

Physical

Application LayerApplication Layer

Provides network services Provides network services (processes) to applications(processes) to applications..

For example, a computer on a For example, a computer on a LAN can save files to a server LAN can save files to a server using a network redirector using a network redirector supplied by NOSs like Novell.supplied by NOSs like Novell.

Network redirectors allow Network redirectors allow applications like Word and applications like Word and Excel to “see” the network.Excel to “see” the network.

Application

Presentation

Session

Transport

Network

Data-Link

Physical

Presentation LayerPresentation Layer

Provides data representation Provides data representation and code formatting.and code formatting.

Code formatting includes Code formatting includes compression and encryptioncompression and encryption

Basically, the presentation Basically, the presentation layer is responsible for layer is responsible for representing data so that the representing data so that the source and destination can source and destination can communicate at the communicate at the application layer.application layer.

Application

Presentation

Session

Transport

Network

Data-Link

Physical

Session LayerSession Layer

Provides inter-host communication by Provides inter-host communication by establishing, maintaining, and establishing, maintaining, and terminating sessionsterminating sessions..

Session uses dialog control and dialog Session uses dialog control and dialog separation to manage the sessionseparation to manage the session

Some Session protocols:Some Session protocols: NFS (Network File System)NFS (Network File System) SQL (Structured Query Language)SQL (Structured Query Language) RCP (Remote Call Procedure)RCP (Remote Call Procedure) ASP (AppleTalk Session Protocol)ASP (AppleTalk Session Protocol) SCP (Session Control Protocol)SCP (Session Control Protocol) X-windowX-window

Application

Presentation

Session

Transport

Network

Data-Link

Physical


Provides reliability, flow control, and Provides reliability, flow control, and error correctionerror correction through the use of TCP. through the use of TCP.

TCP segments the data, adding a TCP segments the data, adding a header with control information for header with control information for sequencing and acknowledging packets sequencing and acknowledging packets received.received.

The segment header also includes The segment header also includes source and destination ports for upper-source and destination ports for upper-layer applicationslayer applications

TCP is connection-oriented and uses TCP is connection-oriented and uses windowing.windowing.

UDP is connectionless. UDP UDP is connectionless. UDP does notdoes not acknowledge the receipt of packets.acknowledge the receipt of packets.

Application

Presentation

Session

Transport

Network

Data-Link

Physical

Network LayerNetwork Layer

Responsible for Responsible for logically logically addressingaddressing the packet and the packet and path path determinationdetermination..

Addressing is done through Addressing is done through routedrouted protocols such as IP, IPX, protocols such as IP, IPX, AppleTalk, and DECnet.AppleTalk, and DECnet.

Path Selection is done by using Path Selection is done by using routingrouting protocols such as RIP, protocols such as RIP, IGRP, EIGRP, OSPF, and BGP.IGRP, EIGRP, OSPF, and BGP.

Routers operate at the Network Routers operate at the Network LayerLayer

Application

Presentation

Session

Transport

Network

Data-Link

Physical

Data-Link LayerData-Link Layer

Provides Provides access to the mediaaccess to the media Handles error notification, Handles error notification,

network topology issues, and network topology issues, and physically addressing the physically addressing the frame.frame.

Media Access Control Media Access Control through either...through either...

Deterministic—token passingDeterministic—token passing Non-deterministic—broadcast Non-deterministic—broadcast

topology (collision domains)topology (collision domains) Important concept: CSMA/CDImportant concept: CSMA/CD

Application

Presentation

Session

Transport

Network

Data-Link

Physical

Physical LayerPhysical Layer Provides electrical, Provides electrical,

mechanical, procedural and mechanical, procedural and functional means for functional means for activating and maintaining activating and maintaining links between systemslinks between systems..

Includes the medium through Includes the medium through which bits flow. Media can which bits flow. Media can be...be...

CAT 5 cableCAT 5 cable Coaxial cableCoaxial cable Fiber Optics cableFiber Optics cable The atmosphereThe atmosphere

Application

Presentation

Session

Transport

Network

Data-Link

Physical

Peer-to-Peer CommunicationsPeer-to-Peer Communications Peers communicate using the PDU of their Peers communicate using the PDU of their

layer. For example, the network layers of the layer. For example, the network layers of the source and destination are peers and use source and destination are peers and use packets to communicate with each other.packets to communicate with each other.

Application Application

Presentation Presentation

Session Session

Transport Transport

Network Network

Data-Link Data-Link

Physical Physical

Data

SegmentsPacketsFramesBits

DataData

Encapsulation ExampleEncapsulation Example

You type an email message. You type an email message. SMTP takes the SMTP takes the datadata and and passes it to the Presentation passes it to the Presentation Layer.Layer.

Presentation codes the Presentation codes the datadata as ASCII.as ASCII.

Session establishes a Session establishes a connection with the connection with the destination for the purpose destination for the purpose of transporting the of transporting the datadata..

Application

Presentation

Session

Transport

Network

Data-Link

Physical

Encapsulation ExampleEncapsulation Example Transport Transport segmentssegments the the

data using TCP and hands data using TCP and hands it to the Network Layer for it to the Network Layer for addressingaddressing

Network addresses the Network addresses the packetpacket using IP. using IP.

Data-Link then encaps. the Data-Link then encaps. the packet in a packet in a frameframe and and addresses it for local addresses it for local delivery (MACs)delivery (MACs)

The Physical layer sends The Physical layer sends the the bitsbits down the wire. down the wire.

Application

Presentation

Session

Transport

Network

Data-Link

Physical


Application

Presentation

Session

Transport

Network

Data-Link

Physical

THE OSI MODEL

LAN Devices & LAN Devices & TechnologiesTechnologies

The Data-Link & Physical The Data-Link & Physical LayersLayersData-Link

Physical

DevicesDevices

What does it do?What does it do? Connects LAN Connects LAN

segments;segments; Filters traffic based on Filters traffic based on

MAC addresses; andMAC addresses; and Separates collision Separates collision

domains based upon domains based upon MAC addresses.MAC addresses.

What layer device?

DevicesDevices

What does it do?What does it do? Since it is a multi-port Since it is a multi-port

bridge, it can alsobridge, it can also Connect LAN segments;Connect LAN segments; Filter traffic based on MAC Filter traffic based on MAC

addresses; andaddresses; and Separate collision Separate collision

domainsdomains However, switches also However, switches also

offer offer full-duplex, dedicated full-duplex, dedicated bandwidthbandwidth to segments or to segments or desktops.desktops.

What layer device?

DevicesDevices

What does it do?What does it do? Concentrates LAN Concentrates LAN

connections from connections from multiple devices into multiple devices into one locationone location

Repeats the signal (a Repeats the signal (a hub is a multi-port hub is a multi-port repeater)repeater)

What layer device?

DevicesDevices

What does it do?What does it do? Interconnects networks Interconnects networks

and provides broadcast and provides broadcast controlcontrol

Determines the path using Determines the path using a routing protocol or static a routing protocol or static routeroute

Re-encapsulates the Re-encapsulates the packet in the appropriate packet in the appropriate frame format and switches frame format and switches it out the interfaceit out the interface

Uses logical addressing Uses logical addressing (i.e. IP addresses) to (i.e. IP addresses) to determine the pathdetermine the path

What layer device?

Media TypesMedia Types

LAN TechnologiesLAN Technologies

Three Most Common

Used Today in

Networking

Ethernet/802.3Ethernet/802.3

Cable Specifications:Cable Specifications: 10Base10Base22

Called Thinnet; uses coaxCalled Thinnet; uses coax Max. distance = 185 meters (almost Max. distance = 185 meters (almost 2200)00)

10Base10Base55 Called Thicknet; uses coaxCalled Thicknet; uses coax Max. distance = Max. distance = 5500 meters00 meters

10Base10BaseTT Uses Uses TTwisted-pairwisted-pair Max. distance = 100 metersMax. distance = 100 meters

10 means 10 Mbps10 means 10 Mbps


Ethernet is broadcast topology.Ethernet is broadcast topology. What does that mean?What does that mean?

Every devices on the Ethernet segment sees every frame.Every devices on the Ethernet segment sees every frame. Frames are addressed with source and destination ______ Frames are addressed with source and destination ______

addresses.addresses. When a source does not know the destination When a source does not know the destination oror wants to wants to

communicate with every device, it encapsulates the frame communicate with every device, it encapsulates the frame with a with a broadcastbroadcast MAC address: MAC address: FFFF.FFFF.FFFFFFFF.FFFF.FFFF

What is the main network traffic problem caused by What is the main network traffic problem caused by Ethernet broadcast topologies?Ethernet broadcast topologies?


Ethernet topologies are also shared Ethernet topologies are also shared media.media.

That means media access is controlled on That means media access is controlled on a “first come, first serve” basis.a “first come, first serve” basis.

This results in collisions between the data This results in collisions between the data of two simultaneously transmitting devices.of two simultaneously transmitting devices.

Collisions are resolved using what Collisions are resolved using what method?method?


CSMA/CD (Carrier Sense Multiple Access with Collision CSMA/CD (Carrier Sense Multiple Access with Collision Detection)Detection)

Describe how CSMA/CD works:Describe how CSMA/CD works: A node needing to transmit listens for activity on the media. If A node needing to transmit listens for activity on the media. If

there is none, it transmits.there is none, it transmits. The node continues to listen. A collision is detected by a The node continues to listen. A collision is detected by a

spike in voltage (a bit can only be a 0 or a 1--it cannot be a 2)spike in voltage (a bit can only be a 0 or a 1--it cannot be a 2) The node generates a jam signal to tell all devices to stop The node generates a jam signal to tell all devices to stop

transmitting for a random amount of time (back-off algorithm).transmitting for a random amount of time (back-off algorithm). When media is clear of any transmissions, the node can When media is clear of any transmissions, the node can

attempt to retransmit.attempt to retransmit.

Address Resolution ProtocolAddress Resolution Protocol

In broadcast topologies, we need a way to resolve In broadcast topologies, we need a way to resolve unknown destination MAC addresses.unknown destination MAC addresses.

ARP is protocol where the sending device sends out a ARP is protocol where the sending device sends out a broadcast ARP request which says, “What’s you MAC broadcast ARP request which says, “What’s you MAC address?”address?”

If the destination exists on the same LAN segment as the If the destination exists on the same LAN segment as the source, then the destination replies with its MAC address.source, then the destination replies with its MAC address.

However, if the destination and source are separated by a However, if the destination and source are separated by a router, the router will not forward the broadcast (an router, the router will not forward the broadcast (an important function of routers). Instead the router replies important function of routers). Instead the router replies with its own MAC address.with its own MAC address.


Application

Presentation

Session

Transport

Network

Data-Link

Physical

THE OSI MODEL

IP AddressingIP Addressing

Subnetting ReviewSubnetting ReviewNetwork

Logical AddressingLogical Addressing

At the network layer, we use logical, hierarchical At the network layer, we use logical, hierarchical addressing.addressing.

With Internet Protocol (IP), this address is a 32-With Internet Protocol (IP), this address is a 32-bit addressing scheme divided into four octets.bit addressing scheme divided into four octets.

Do you remember the classes 1st octet’s value?Do you remember the classes 1st octet’s value? Class A: 1 - 126Class A: 1 - 126 Class B: 128 - 191Class B: 128 - 191 Class C: 192 - 223Class C: 192 - 223 Class D: 224 - 239 (multicasting)Class D: 224 - 239 (multicasting) Class E: 240 - 255 (experimental)Class E: 240 - 255 (experimental)

Network vs. HostNetwork vs. Host

N H H H

Class A: 27 = 126 networks; 224 > 16 million hosts

N N H H

Class B : 214 = 16,384 networks; 216 > 65,534 hosts

N N N H

Class C : 221 > 2 million networks; 28 = 254 hosts

Why Subnet?Why Subnet?

Remember: we are usually dealing with a Remember: we are usually dealing with a broadcast topology.broadcast topology.

Can you imagine what the network traffic Can you imagine what the network traffic overhead would be like on a network with 254 overhead would be like on a network with 254 hosts trying to discover each others MAC hosts trying to discover each others MAC addresses?addresses?

Subnetting allows us to segment LANs into Subnetting allows us to segment LANs into logical broadcast domains called subnets, logical broadcast domains called subnets, thereby improving network performance.thereby improving network performance.

Four Subnetting StepsFour Subnetting Steps

To correctly subnet a given network address into To correctly subnet a given network address into subnet addresses, ask yourself the following subnet addresses, ask yourself the following questions:questions:

1.1. How many bits do I need to borrow?How many bits do I need to borrow?

2.2. What’s the subnet mask?What’s the subnet mask?

3.3. What’s the “magic number” or multiplier?What’s the “magic number” or multiplier?

4.4. What are the first three subnetwork addresses?What are the first three subnetwork addresses? Let’s look at each of these questions in detailLet’s look at each of these questions in detail

1. How many bits to borrow?1. How many bits to borrow?

First, you need to know how many bits you First, you need to know how many bits you have to work with.have to work with.

Second, you must know either how many Second, you must know either how many subnets you need or how many hosts per subnets you need or how many hosts per subnet you need.subnet you need.

Finally, you need to figure out the number Finally, you need to figure out the number of bits to borrow.of bits to borrow.


How many bits do I have to work with?How many bits do I have to work with? Depends on the class of your network address.Depends on the class of your network address.

Class C: 8 host bitsClass C: 8 host bits Class B: 16 host bitsClass B: 16 host bits Class A: 24 host bitsClass A: 24 host bits

Remember: you must borrow at least 2 bits for Remember: you must borrow at least 2 bits for subnets and leave at least 2 bits for host addresses.subnets and leave at least 2 bits for host addresses.

2 bits borrowed allows 22 bits borrowed allows 222 - 2 = 2 subnets- 2 = 2 subnets


How many subnets or hosts do I need?How many subnets or hosts do I need? A simple formula:A simple formula:

Total Bits = Bits Borrowed + Bits LeftTotal Bits = Bits Borrowed + Bits Left TB = BB + BLTB = BB + BL

I need x subnets:I need x subnets: x22BB • I need x hosts: x22BL • Remember: we need to subtract

two to provide for the subnetwork and broadcast addresses.


Class C Example: 210.93.45.0Class C Example: 210.93.45.0 Design goals specify at least 5 subnets so how Design goals specify at least 5 subnets so how

many bits do we borrow?many bits do we borrow? How many bits in the host portion do we have to How many bits in the host portion do we have to

work with (TB)?work with (TB)? What’s the BB in our TB = BB + BL formula? (8 = What’s the BB in our TB = BB + BL formula? (8 =

BB + BL)BB + BL) 2 to the what power will give us at least 5 2 to the what power will give us at least 5

subnets?subnets?

2233 - 2 = 6 subnets - 2 = 6 subnets


How many bits are left for hosts?How many bits are left for hosts?

TB = BB + BLTB = BB + BL

8 = 3 + BL8 = 3 + BL

BL = 5BL = 5 So how many hosts can we assign to each So how many hosts can we assign to each

subnet?subnet?

2255 - 2 = 30 hosts - 2 = 30 hosts


Class B Example: 185.75.0.0Class B Example: 185.75.0.0 Design goals specify no more than 126 hosts per Design goals specify no more than 126 hosts per

subnet, so how many bits do we need to leave (BL)?subnet, so how many bits do we need to leave (BL)? How many bits in the host portion do we have to How many bits in the host portion do we have to

work with (TB)?work with (TB)? What’s the BL in our TB = BB + BL formula? (16 = What’s the BL in our TB = BB + BL formula? (16 =

BB + BL)BB + BL) 2 to the what power will insure no more than 126 2 to the what power will insure no more than 126

hosts per subnet and give us the most subnets?hosts per subnet and give us the most subnets?

2277 - 2 = 126 hosts - 2 = 126 hosts


How many bits are left for subnets?How many bits are left for subnets?

TB = BB + BLTB = BB + BL

16 = BB + 716 = BB + 7

BL = 9BL = 9 So how many subnets can we have?So how many subnets can we have?

2299 - 2 = 510 subnets - 2 = 510 subnets

2. What’s the subnet mask?2. What’s the subnet mask?

We determine the subnet mask by adding up the decimal We determine the subnet mask by adding up the decimal value of the bits we borrowed.value of the bits we borrowed.

In the previous Class C example, we borrowed 3 bits. Below In the previous Class C example, we borrowed 3 bits. Below is the host octet showing the bits we borrowed and their is the host octet showing the bits we borrowed and their decimal values.decimal values.

128 64 32 16 8 4 2 1

1 1 1

We add up the decimal value of these bits and get 224. That’s the last non-zero octet of our subnet mask.So our subnet mask is 255.255.255.224

3. What’s the “magic number?”3. What’s the “magic number?”

To find the “magic number” or the To find the “magic number” or the multiplier we will use to determine the multiplier we will use to determine the subnetwork addresses, we subtract the subnetwork addresses, we subtract the last non-zero octet from 256.last non-zero octet from 256.

In our Class C example, our subnet mask In our Class C example, our subnet mask was 255.255.255.224. 224 is our last non-was 255.255.255.224. 224 is our last non-zero octet.zero octet.

Our magic number is 256 - 224 = 32Our magic number is 256 - 224 = 32

Last Non-Zero OctetLast Non-Zero Octet

Memorize this table. You should be able to:Memorize this table. You should be able to: Quickly calculate the last non-zero octet when given the number of Quickly calculate the last non-zero octet when given the number of

bits borrowed.bits borrowed. Determine the number of bits borrowed given the last non-zero octet.Determine the number of bits borrowed given the last non-zero octet. Determine the amount of bits left over for hosts and the number of Determine the amount of bits left over for hosts and the number of

host addresses available.host addresses available.

Bits Borrowed

Non-Zero Octet Hosts

2 192 623 224 304 240 145 248 66 252 2

4. What are the subnets?4. What are the subnets?

We now take our “magic number” and use it as a We now take our “magic number” and use it as a multiplier.multiplier.

Our Class C address was 210.93.45.0.Our Class C address was 210.93.45.0. We borrowed bits in the fourth octet, so that’s We borrowed bits in the fourth octet, so that’s

where our multiplier occurswhere our multiplier occurs 1st subnet: 210.93.45.321st subnet: 210.93.45.32 2nd subnet: 210.93.45.642nd subnet: 210.93.45.64 3rd subnet: 210.93.45.963rd subnet: 210.93.45.96

We keep adding 32 in the fourth octet to get all We keep adding 32 in the fourth octet to get all six available subnet addresses.six available subnet addresses.

Host & Broadcast AddressesHost & Broadcast Addresses

Now you can see why we subtract 2 when Now you can see why we subtract 2 when determining the number of host address.determining the number of host address.

Let’s look at our 1st subnet: Let’s look at our 1st subnet: 210.93.45.32210.93.45.32 What is the total range of addresses up to our What is the total range of addresses up to our

next subnet, next subnet, 210.93.45.64?210.93.45.64? 210.93.45.32 to 210.93.45.63 or 32 addresses210.93.45.32 to 210.93.45.63 or 32 addresses .32 cannot be assigned to a host. Why?.32 cannot be assigned to a host. Why? .63 cannot be assigned to a host. Why?.63 cannot be assigned to a host. Why? So our host addresses are .33 - .62 or 30 host So our host addresses are .33 - .62 or 30 host

addresses--just like we figured out earlier.addresses--just like we figured out earlier.


Application

Presentation

Session

Transport

Network

Data-Link

Physical

THE OSI MODEL


A Different Way to Represent A Different Way to Represent a Subnet Maska Subnet Mask

Network


CClassless lassless IInternterddomain omain RRouting is a method of outing is a method of representing an IP address and its subnet mask with representing an IP address and its subnet mask with a prefix.a prefix.

For example: 192.168.50.0/27For example: 192.168.50.0/27 What do you think the 27 tells you?What do you think the 27 tells you?

27 is the number of 1 bits in the subnet mask. Therefore, 27 is the number of 1 bits in the subnet mask. Therefore, 255.255.255.224255.255.255.224

Also, you know 192 is a Class C, so we borrowed 3 bits!!Also, you know 192 is a Class C, so we borrowed 3 bits!! Finally, you know the magic number is 256 - 224 = 32, so Finally, you know the magic number is 256 - 224 = 32, so

the first useable subnet address is 197.168.50.32!!the first useable subnet address is 197.168.50.32!! Let’s see the power of CIDR notation.Let’s see the power of CIDR notation.

202.151.37.0/26202.151.37.0/26

Subnet mask?Subnet mask? 255.255.255.255.255.255.192192

Bits borrowed?Bits borrowed? Class C so 2 bits borrowedClass C so 2 bits borrowed

Magic Number?Magic Number? 256 - 256 - 192192 = 64 = 64

First useable subnet address?First useable subnet address? 202.151.37.64202.151.37.64

Third useable subnet address?Third useable subnet address? 64 + 64 + 64 = 192, so 202.151.37.19264 + 64 + 64 = 192, so 202.151.37.192

198.53.67.0/30198.53.67.0/30

Subnet mask?Subnet mask? 255.255.255.255.255.255.252252

Bits borrowed?Bits borrowed? Class C so 6 bits borrowedClass C so 6 bits borrowed

Magic Number?Magic Number? 256 - 256 - 252252 = 4 = 4

Third useable subnet address?Third useable subnet address? 4 + 4 + 4 = 12, so 198.53.67.124 + 4 + 4 = 12, so 198.53.67.12

Second subnet’s broadcast address?Second subnet’s broadcast address? 4 + 4 + 4 - 1 = 11, so 198.53.67.114 + 4 + 4 - 1 = 11, so 198.53.67.11

200.39.89.0/28200.39.89.0/28

What kind of address is 200.39.89.0?What kind of address is 200.39.89.0? Class C, so 4 bits borrowedClass C, so 4 bits borrowed Last non-zero octet is 240Last non-zero octet is 240 Magic number is 256 - 240 = 16Magic number is 256 - 240 = 16 32 is a multiple of 16 so 200.39.89.32 is a subnet 32 is a multiple of 16 so 200.39.89.32 is a subnet

address--the second subnet address!!address--the second subnet address!! What’s the broadcast address of 200.39.89.32?What’s the broadcast address of 200.39.89.32?

32 + 16 -1 = 47, so 200.39.89.4732 + 16 -1 = 47, so 200.39.89.47

194.53.45.0/29194.53.45.0/29

What kind of address is 194.53.45.26?What kind of address is 194.53.45.26? Class C, so 5 bits borrowedClass C, so 5 bits borrowed Last non-zero octet is 248Last non-zero octet is 248 Magic number is 256 - 248 = 8Magic number is 256 - 248 = 8 Subnets are .8, .16, .24, .32, ect.Subnets are .8, .16, .24, .32, ect. So 194.53.45.26 belongs to the third subnet address So 194.53.45.26 belongs to the third subnet address

(194.53.45.24) and is a host address.(194.53.45.24) and is a host address. What broadcast address would this host use to What broadcast address would this host use to

communicate with other devices on the same subnet?communicate with other devices on the same subnet? It belongs to .24 and the next is .32, so 1 less is .31 It belongs to .24 and the next is .32, so 1 less is .31

(194.53.45.31)(194.53.45.31)

No Worksheet Needed!No Worksheet Needed!

After some practice, you should never need a After some practice, you should never need a subnetting worksheet again.subnetting worksheet again.

The only information you need is the IP address and The only information you need is the IP address and the CIDR notation.the CIDR notation.

For example, the address 221.39.50/26For example, the address 221.39.50/26 You can quickly determine that the first subnet You can quickly determine that the first subnet

address is 221.39.50.64. How?address is 221.39.50.64. How? Class C, 2 bits borrowedClass C, 2 bits borrowed 256 - 192 = 256 - 192 = 6464, so 221.39.50.64, so 221.39.50.64

For the rest of the addresses, just do multiples of 64 For the rest of the addresses, just do multiples of 64 (.64, .128, .192).(.64, .128, .192).

The Key!!The Key!!

MEMORIZE THIS TABLE!!!MEMORIZE THIS TABLE!!!

Bits Borrowed

Non-Zero Octet Hosts

2 192 623 224 304 240 145 248 66 252 2

Practice On Your OwnPractice On Your Own

Below are some practice problems. Take out a sheet of paper and calculate...Below are some practice problems. Take out a sheet of paper and calculate... Bits borrowedBits borrowed Last non-zero octetLast non-zero octet Second subnet address and broadcast addressSecond subnet address and broadcast address

1.1. 192.168.15.0/26192.168.15.0/262.2. 220.75.32.0/30220.75.32.0/303.3. 200.39.79.0/29200.39.79.0/294.4. 195.50.120.0/27195.50.120.0/275.5. 202.139.67.0/28202.139.67.0/286.6. Challenge:Challenge: 132.59.0.0/19 132.59.0.0/197.7. Challenge:Challenge: 64.0.0.0/16 64.0.0.0/16

Answers


Application

Presentation

Session

Transport

Network

Data-Link

Physical

THE OSI MODEL

Routing BasicsRouting Basics

Path Determination & Packet Path Determination & Packet SwitchingSwitching

Network

A Router’s FunctionsA Router’s Functions

A router is responsible for determining the A router is responsible for determining the packet’s path and switching the packet out the packet’s path and switching the packet out the correct port.correct port.

A router does this in five steps:A router does this in five steps:1.1. De-encapsulates the packetDe-encapsulates the packet

2.2. Performs the ANDing operationPerforms the ANDing operation

3.3. Looks for entry in routing tableLooks for entry in routing table

4.4. Re-encapsulates packet into a frameRe-encapsulates packet into a frame

5.5. Switches the packet out the correct interfaceSwitches the packet out the correct interface

Routed v. Routing ProtocolsRouted v. Routing Protocols

What is a routed protocol?What is a routed protocol? Routed protocols are protocols that enable data to be Routed protocols are protocols that enable data to be

transmitted across a collection of networks or transmitted across a collection of networks or internetworks using a hierarchical addressing scheme.internetworks using a hierarchical addressing scheme.

Examples include IP, IPX and AppleTalk. Examples include IP, IPX and AppleTalk. A routable protocol provides both a network and node A routable protocol provides both a network and node

number to each device on the network. Routers AND the number to each device on the network. Routers AND the address to discover the network portion of the address.address to discover the network portion of the address.

An example of a protocol that is not routable is NetBEUI An example of a protocol that is not routable is NetBEUI because it does not have a network/node structure.because it does not have a network/node structure.

Routed v. Routing ProtocolsRouted v. Routing Protocols

What is a routing protocol?What is a routing protocol? A routing protocol is a protocol that determines the A routing protocol is a protocol that determines the

path a routed protocol will follow to its destination.path a routed protocol will follow to its destination. Routers use routing protocols to create a map of the Routers use routing protocols to create a map of the

network. These maps allow path determination and network. These maps allow path determination and packet switching. Maps become part of the router’s packet switching. Maps become part of the router’s routing table.routing table.

Examples of routing protocols include: RIP, IGRP, Examples of routing protocols include: RIP, IGRP, EIGRP, & OSPFEIGRP, & OSPF

Multi-protocol RoutingMulti-protocol Routing

Routers are capable of running multiple routing protocols Routers are capable of running multiple routing protocols (RIP, IGRP, OSPF, etc.) as well as running multiple (RIP, IGRP, OSPF, etc.) as well as running multiple routed protocols (IP, IPX, AppleTalk).routed protocols (IP, IPX, AppleTalk).

For a router to be able use different routing and routing For a router to be able use different routing and routing protocols, you must enable the protocols using the protocols, you must enable the protocols using the appropriate commands.appropriate commands.

Dynamic v. Static RoutingDynamic v. Static Routing

Dynamic routing refers to the process of allowing Dynamic routing refers to the process of allowing the router to determine the path to the destination.the router to determine the path to the destination.

Routing protocols enable dynamic routing where Routing protocols enable dynamic routing where multiple paths to the same destination exist.multiple paths to the same destination exist.

Dynamic v. Static RoutingDynamic v. Static Routing

Static routing means that the network administrator Static routing means that the network administrator directly assigns the path router are to take to the directly assigns the path router are to take to the destination.destination.

Static routing is most often used with stub networks Static routing is most often used with stub networks where only one path exists to the destination.where only one path exists to the destination.

Default RoutesDefault Routes

A default route is usually to a border or gateway A default route is usually to a border or gateway router that all routers on a network can send router that all routers on a network can send packets to if they do not know the route for a packets to if they do not know the route for a particular network.particular network.

Routing Protocol ClassesRouting Protocol Classes

Routing protocols can be divided into three Routing protocols can be divided into three classes:classes: Distance–vector: determines the route based Distance–vector: determines the route based

on the direction (vector) and distance to the on the direction (vector) and distance to the destinationdestination

Link-state: opens the shortest path first to the Link-state: opens the shortest path first to the destination by recreating an exact topology of destination by recreating an exact topology of the network in its routing tablethe network in its routing table

Hybrid: combines aspects of both Hybrid: combines aspects of both

ConvergenceConvergence

Convergence means that all routers share the Convergence means that all routers share the same information about the network. In other same information about the network. In other words, each router knows its neighbor routers words, each router knows its neighbor routers routing tablerouting table

Every time there is a topology change, routing Every time there is a topology change, routing protocols update the routers until the network is protocols update the routers until the network is said to have converged again.said to have converged again.

The time of convergence varies depending upon The time of convergence varies depending upon the routing protocol being used.the routing protocol being used.

Distance-vector RoutingDistance-vector Routing

Each router receives a routing table periodically Each router receives a routing table periodically from its directly connected neighboring routers. from its directly connected neighboring routers.

For example, in the graphic, Router B receives For example, in the graphic, Router B receives information from Router A. Router B adds a information from Router A. Router B adds a distance-vector number (such as a number of hops), distance-vector number (such as a number of hops), and then passes this new routing table to its other and then passes this new routing table to its other neighbor, Router C.neighbor, Router C.

Link-state RoutingLink-state Routing

Link-state protocols maintain complex databases that Link-state protocols maintain complex databases that summarize routes to the entire network. summarize routes to the entire network.

Each time a new route is added or a route goes down, Each time a new route is added or a route goes down, each router receives a message and then recalculates a each router receives a message and then recalculates a spanning tree algorithm and updates its topology database.spanning tree algorithm and updates its topology database.

Comparing the TwoComparing the Two

DISTANCE-VECTOR LINK-STATE

Views network topology from neighbor’s perspective

Gets common view of entire network topology

Adds distance vectors from router to router

Calculates the shortest path to other routers

Frequent, periodic updates: slow convergence

Event triggered updates: fast convergence

Passes copies of routing tables to neighbors

Passes link-state routing updates to all routers in the system.

Hybrid RoutingHybrid Routing

Cisco’s proprietary routing protocol, Cisco’s proprietary routing protocol, EIGRP, is considered a hybrid.EIGRP, is considered a hybrid.

EIGRP uses distance-vector metrics. EIGRP uses distance-vector metrics. However, it uses event-triggered topology However, it uses event-triggered topology changes instead of periodic passing of changes instead of periodic passing of routing tables.routing tables.


Application

Presentation

Session

Transport

Network

Data-Link

Physical

THE OSI MODEL


A Quick ReviewA Quick ReviewTransport

Transport Layer FunctionsTransport Layer Functions

Synchronization of the connectionSynchronization of the connection Three-way handshakeThree-way handshake

Flow ControlFlow Control ““Slow down, you’re overloading my memory buffer!!”Slow down, you’re overloading my memory buffer!!”

Reliability & Error RecoveryReliability & Error Recovery Windowing: “How much data can I send before Windowing: “How much data can I send before

getting an acknowledgement?”getting an acknowledgement?” Retransmission of lost or unacknowledged segmentsRetransmission of lost or unacknowledged segments

Transport’s Two ProtocolsTransport’s Two Protocols

TCPTCP Transmission Control Transmission Control

ProtocolProtocol Connection-orientedConnection-oriented Acknowledgment & Acknowledgment &

Retransmission of Retransmission of segmentssegments

WindowingWindowing Applications:Applications:

EmailEmail File TransferFile Transfer E-CommerceE-Commerce

UDPUDP User Datagram User Datagram

ProtocolProtocol ConnectionlessConnectionless No No

AcknowledgementsAcknowledgements Applications: Applications:

Routing ProtocolsRouting Protocols Streaming AudioStreaming Audio GamingGaming Video ConferencingVideo Conferencing

Date post:	19-Dec-2015
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