E&CE 418: Tutorial 1E&CE 418: Tutorial 1

Instructor: Prof. Xuemin (Sherman) ShenTA Ni ZhTA: Ning Zhang

Email: n35zhang@uwaterloo.caOffice Hours: Tue 1:00pm-3:00pm or by appointmentOffice Hours: Tue 1:00pm 3:00pm or by appointment

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RoadmapRoadmap

OSI Model TCP/IP protocol suiteTCP/IP protocol suite Data encapsulation and transmission Communication at each layer Network protocol analyzer Network protocol analyzer

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OSI Model

Layers Description

7 Application Allows user access to network provide services to users7 Application Allows useraccesstonetwork,provideservicestousers.

6 Presentation Datarepresentation,encryptionanddecryption, etc

5 Session Setupconnection,login,etc(startand endconversation)

4 Transport Reliable transmissionofpacketsfromsourcetodestination(endtoend).

3 Network Routing:guidesthepacket fromsourcetodestination

2 Data Link Reliable transmissionfromnodetonode

1 Physical Transmits raw bit stream over channel1 Physical Transmitsrawbitstreamoverchannel

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OSI ModelLayers Dataunit

Application Datapp ca o a a

Presentation Data

Session Data

Transport Segments

Network Packet/Datagramg

Data Link Frame

Physical Bit

Data encapsulation and decapsulationp pa) Header and trailer attached at each layer aim to perform certain functions at each layer.b) Headers are added while a packet is going down the stack at each layer. c) Each protocol on the different layer has its own format

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c) Each protocol on the different layer has its own format.

TCP/IP Model

Application7

Presentation6

S i5

Application5

Session5

Transport4 Transport4

Network3

Data Link2

Internet3

Data Link2 DataLink2

Physical1

Data Link2

Physical1Host to network

OSI Model Layers TCP/IP Protocol Suite

The application layer in TCP/IP is equivalent to the combined session

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The application layer in TCP/IP is equivalent to the combined session, presentation, and application layers in the OSI model.

TCP/IP Protocol SuiteApplication layer : responsible for providing services to the user.

e.g., FTP, SMTP, Http, etcg , , , p,Transport layer : responsible for the delivery of application data from

source to destination. e.g., TCP(reliable delivery), UDP.I t t l ibl f th d li f i di id l k t fInternet layer : responsible for the delivery of individual packets from

the source host to the destination host. Main functions: forwarding and routing. e.g., IP, etcforwarding and routing. e.g., IP, etc

Data link layer: responsible for hop-to-hop (node-to-node) deliveryMajor duties: framing, flow control, error control, access control . e.g., Ethernet, 802.11(Wireless lan), etc

Physical layer : responsible for movements of individual bits from one hop (node) to the next over a physical medium(node) to the next over a physical medium. It maps incoming bits from the data link layer into signals appropriate to the channel.

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Data encapsulation and transmissionsource

applicationdata datatransportinternet

linkTCPHn data

segment Htpacket

TCPIPMAC data

TCP data

IP

framephysical

linkphysical

TCPIPMAC data

p y

switch

destinationapplication

internetlink HtH Mdata data

TCPHn data

TCPIPMAC dataIP

applicationtransportinternet

link

linkphysical

HtHn M

routerTCPHn data

segment Htpacket

TCPIPMAC data

data dataTCP data

IP

frame

TCPM

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linkphysical

routerTCPIPMAC dataframe

Communication at each layerCommunication at each layer

Application Application Application protocol

TCP

IP

TCP

IP

TCP protocol

IP protocol IP protocolIP IP IP protocol

Data LinkNetwork Access

DataLink

Data Link

Data Link

Data Link

Data Link

DataLink

DataLink

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Communication at application layerA B

Transport Transport

ApplicationApplication Source Destination DataD HeaderHLegend

Data linkData link

R1 R3 R4

NetworkNetwork

Transport Transport

Physical Physical

Data linkData link

MessageD5 D5

g

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D5 D5MessageThe unit of communication at the application layer is a message.

Communication at transport layerThe port number is used in the transport layer header to indicate to which application that piece of data is associated.Sequence numbers are assigned in the header of each packet to reassemble th t i t th i i l dthe segments into the original order.

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Communication at transport layerA

R1 R3 R4

B

NetworkNetwork

Transport TransportSource Destination DataD HeaderHLegend

Ph i l Ph i l

Data linkData link

NetworkNetwork

Physical Physical

SegmentD4 H4

D4 H4

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SegmentD4 H4

The unit of communication at the transport layer is a segment.

Communication at the internet layer Networklayerreceivethedatafromthetransportlayer,ie.,thesegment,andaddIPheadertocreatethepacket/datagram.Network layer provides services to guide/direct the packet to the destination host.Networklayerprovidesservicestoguide/directthepackettothedestinationhost.

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Communication at the internet layer

A R1 R3 R4 BNetworkNetwork

Source Destination DataD HeaderHLegend

Physical Physical

Data linkData link

Physical Physical

DatagramD3 H3

DatagramD3 H3

Th i f i i h i l i d / k13

gThe unit of communication at the internet layer is a datagram/packet.The IP address of source and destination never change in transmission.

Communication at the data link layer

DataLinklayerprotocolsgovernshowtoformataframeforuseondifferentmedia(e.g.,copper,fiber,andwirelessnetworkmedia.).Differentprotocolsmaybeinusefordifferentmedia.(ethernet frame,802.11wirelessframe,etc)

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Communication at the data link layer

AData linkData link

R1 R3 R4 BSource Destination DataD HeaderHLegend

Physical Physical

Link 1 Link 3 Link 5 Link 6

D2 H2Frame

FrameD2

H2

Th i f i i

FrameD2 H2

FrameD2 H2

At each hop along the path an intermediary device accepts frames from one

The unit of communication at the data link layer is a frame.

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At each hop along the path, an intermediary device accepts frames from one medium, decapsulates the frame and then forwards the packets in a new frame.

Communication at the physical layer

The Physical layer controls how data is transmitted on the communication mediamedia.

The role of the Physical layer is to encode the binary digits that represent Data Li k l f i t i l d t t it d i th i lLink layer frames into signals and to transmit and receive these signals across the physical media - copper wires, optical fiber, and wireless - that connect network devices.

It is also the job of the Physical layer to retrieve these individual signals from the media, restore them to their bit representations, and pass the bits up to the Data Link layer as a complete frame.

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Communication at the physical layer

A R1 R3 R4 B

Source DestinationLegend

APhysical

layerPhysical

layer

R1 R3 R4 B

Link 3 Link 5 Link 6Link 1

011 ... 101

011 ... 101

011 ... 101 011 ... 101

Th i f i i h h i l l i bi

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The unit of communication at the physical layer is a bit.

Network protocol analyzerNetwork protocol analyzer

Wireshark is the world's foremost network protocol analyzer. It p ylets you capture and interactively browse the traffic running on a computer network.p

Lets use Wireshark to analyze the frames and understand how the layers work in real life.y

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SummarySummary

LayeringLayering TCP/IP protocol suite Data encapsulation (head, trailer) Communication at each layery

hop by hop: physical layer, data link layer end to end: application layer transport layerend to end: application layer, transport layer

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