CSC461-CN-Lecture-8-Jan-30-2013

7/28/2019 CSC461-CN-Lecture-8-Jan-30-2013

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BITS PilaniPilani | Dubai | Goa | Hyderabad

Programming for the

Networked EnvironmentsLecture-8, January 30, 2013Rahul Banerjee, PhD (CSE)

Professor, Department of Computer Science & Information Systems

E-mail: [email protected]


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BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

Simple basics that go into programming for thenetwork-based applications: Generic and Socket

APIs

Briefly revisiting the TCP/IP Architecture Current State-of-the-art and Evolving Research

Directions From Clusters and Grids to Clouds Wearable Computing Ubiquitous or Pervasive Computing

Select References to the literature Summary

Interaction Points


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Simplest way to understand this is to look at theway applications are expected to communicate

over the network. Lets assume that we need to write a simple application that

could work for getting some data over the network!

Example-1: A rudimentary short data transfer application andinvolved logic

Example-2: An elementary large data transfer application andinvolved logic

Lets next see the way things get done in realsystems!

How do we write simpleprograms for the networks?


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The application-processes of the simplest kind mightinvolve a client-server relationship.

APIs help! All network-capable Operating Systems have some

application programming interface (API) that makesapplication-to-application communication possible over

networks without necessarily knowing intricate details of

the underlying mechanisms.

University of California at Berkeleys BSD Socket API isone of the most common APIs in use for writing such

applications

Lets us see how things work in this case, fromprogrammers point of view!

Simple Basics of Programmingfor Network-based Applications


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Server-side operations Client-side operations In each case, in the world of the Internet, we have,

often, two basic choices to make: Octet-stream-oriented reliable communication Datagram-oriented so-called unreliable communication

Lets see the first type first! Create a socket or an end-point on the server side Associate a transport port or a local address at which the application

shall listen to incoming requests

Enable and announce that server is ready to listen at this port withqueue-size

Accept any incoming (passive) connection request

Basic Operations Involved


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At client-side: Create a socket or an end-point Send (passive) connection request to serverOverall:

Connect

Send

Receive

.

Close

Basic Operations Involved


7/96BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

Lets take a closer look at theentire matter!


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Network Architecture of the Internet

Wednesday, 30 January 13 8(c)Dr.RahulBanerjee,BITS-Pilani,INDIA

LLC Sub-layer

MAC Sub-layer

Physical layer

TheInternetLayer

TCP(Transport)Layer

ApplicaonLayer

TheHost-to-Network

Interface Link-Layerasper

OSIReference

Model

Physical-Layeras

perOSIReference

Model


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9

A Simplified Network Reference

Model

Host-1 Host-2

Application Layer Application Layer

UpperLayer-to-LowerLayerInterface UpperLayer-to-LowerLayerInterface

UpperLayer-to-LowerLayerInterfaceUpperLayer-to-LowerLayerInterface

UpperLayer-to-LowerLayerInterfaceUpperLayer-to-LowerLayerInterface

Same Layer -to- Same Layer

Virtual Communication Interface

Same Layer -to- Same LayerVirtual Communication Interface

Same Layer -to- Same LayerVirtual Communication Interface

Same Layer -to- Same Layer

Virtual Communication Interface

Same Layer -to- Same LayerPhysical Communication Interface

(c)Dr.RahulBanerjee,BITS-Pilani,INDIA


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Copyright: Dr. Rahul BanerjeeBITS, Pilani (India)

10

IPv4: The Header Structure

0 31

Identification16-bit Flags 3-bit Fragment Offset 13-bit

Ver. 4-bit IHL 4-bit Type of Service 8-bit Total Length 16-bit

Source Address 32-bit

Destination Address 32-bit

TTL 8-bit Protocol Type 8-bit Header Checksum 16-bit

Options + Padding


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Copyright: Dr. Rahul BanerjeeBITS, Pilani (India)

11

IPv6: The Header Structure

0 4 16 31

Payload Length Next Header Hop Limit(16-bit) (8-bit) (8-bit)

Source Address (128-bit)

Destination Address (128-bit)

Ver. TClass Flow Label

(4-bit) (8-bit) (20-bit)


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Intheworldofsockets:Telephony

Analogy

Socket()Endpointforcommunicaon Bind()-Assignauniquetelephonenumber. Listen()Waitforacaller. Connect()-Dialanumber. Accept()Receiveacall. Send(),Recv()Talk. Close()Hangup.


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ATCPServerClientInteracon


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DataStructuresInvolved

ThedatastructuresusedtoholdalltheaddressInformaon:

Structsockaddr{unsignedshortsa_family;charsa_data[14];}

Structsockaddr_in{shortsin_family;unsignedshortsin_port;//PortNumberstructin_addrsin_addr;//IPAddresscharsin_zero[8];

}

Structin_addr{unsignedlongs_addr;//4byteslong}


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ByteOrdering,asdiscussedinthe

morningsession! Byteorderingisthea^ributeofasystemwhichindicateswhetherintegers

arestored/representedletorightorrighttole.

Example1:shortintx=0xAABB(hex)Thiscanbestoredinmemoryas2adjacentbytesaseither(0xaa,0xbb)or

as(0xbb,0xaa).BigEndian:ByteValue:[0xAA][0xBB]Memory:[0][1]

Li^leEndian:ByteValue:[0xBB][0xAA]Memory:[0][1]


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ByteOrdering

Example2:intx=0xAABBCCDDThis4bytelongintegercanberepresentedinthesame2orderings:BigEndian:

ByteValue:[0xAA][0xBB][0xCC][0xDD]Memory:[0][1][2][3]Li^leEndian:ByteValue:[0xDD][0xCC][0xBB][0xAA]Memory:[0][1][2][3]

AllNetworkdataissentinBigEndianformat. InthenetworkingworldwecallthisrepresentaonasNetworkByteOrder

andnaverepresentaononthehostasHostByteOrder.

Whereneeded,weconvertalldataintoNetworkByteOrderbeforetransmission.


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CommonSixoftheManyUlityFuncons

ByteOrdering:HostByteOrdertoNetworkByteOrder: htons(),htonl()

NetworkByteOrdertoHostByteOrder: ntohs(),ntohl()

IPAddressformat:

Asciido^edtoBinary:inet_aton()BinarytoAsciido^ed:inet_ntoa()


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InvolvedSystemCalls:Summary

Socket() Bind() Listen()Accept() Connect()

Read()/Send()/Sendto() Write()/Recv()/Recvfrom() Close()


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Socket()forCreangaConneconEndpoint

Thiscreatesanendpointforanetworkconnecon.IntSocket(intdoman,inttype,intprotocol)domain=PF_INET(IPv4communicaon)

type=SOCK_STREAM(TCP),SOCK_DGRAM(UDP)protocol=0(arandomchoicehereforthisclass!)

Example:socket(PF_INET,SOCK_STREAM,0);

ThiscreatesaTCPsocket.

ThecallreturnsasocketdescriptoronsuccessOR-1onanerror.


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Bind()forA^achingtoanIPandPortAserverprocesscallsbindtoa^achitselftoaspecificportandIPaddress.

IntBind(intsockfd,structsockaddr*my_addr,socklen_taddrlen)sockfd=socketdescriptorreturnedbysocket()my_addr=pointertoavalidsockaddr_instructurecastasasockaddr*pointeraddrlen=lengthofthesockaddr_instructure

Example:

structsockaddr_inmy;

my.sin_family=PF_INET;my.sin_port=htons(80);my.sin_addr.s_addr=INADDR_ANY;bzero(&my,8)bind(sock,(structsockaddr*)&my,sizeof(my));


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Listen()formakingServerWaitfora

connecon

Theserverprocesscallslistentotellthekerneltoinializeawaitqueueofconneconsforthissocket.IntListen(intsock,intbacklog)

sock=socketreturnedbysocket()backlog=Maximumlengthofthependingconneconsqueue

Example:Listen(sock,10);Thiswillallowamaximumof10conneconstobeinpendingstate.


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Accept()foranewconnecon!

AcceptiscalledbyaServerprocesstoacceptnewconneconsfromnewclientstryingtoconnecttotheserver.IntAccept(intsocket,(structsockaddr*)&client,socklen_t*client_len)socket=thesocketinlistenstate

client=willholdthenewclientsinformaonwhenacceptreturns

client_len=pointertosizeoftheclientstructure

Example:structsockaddr_inclient;

intlen=sizeof(client);Accept(sock,(structsockaddr*)&client,&len);


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Connect()forconnecngtoaservice

Connectiscalledbyaclienttoconnecttoaserverport.IntConnect(intsock,(structsockaddr*)&server_addr,socklen_tlen)sock:asocketreturnedbysocket()server_addr:asockaddr_instructpointerfilledwithalltheremoteserver

detailsandcastasasockaddrstructpointerlen:sizeoftheserver_addrstruct

Example:

connect(sock,(structsockaddr*)server_addr,len);


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Send/RecvforDataTransfer Send(),Recv(),Read(),Write()etccallsareusedtosendandreceive

data.

Intsend(intsock,void*mesg,size_tlen,intflags)Intrecv(intsock,void*mesg,size_tlen,intflags)sock=Aconnectedsocketmesg=Pointertoabuffertosend/receivedatafrom/in.

len=Sizeofthemessagebufferflags=0(forourpurpose)Thereturnvalueisthenumberofbytesactuallysent/received.

Example:charsend_buffer[1024];charrecv_buffer[1024];intsent_bytes;intrecvd_bytes;sent_bytes=send(sock,send_buffer,1024,0);

recvd_bytes=recv(sock,recv_buffer,1024,0);


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Close()forClosingtheConnecon

Closesignalstheendofcommunicaonbetweenaserver-clientpair.Thiseffecvelyclosesthesocket.Intclose(intsock)sock=thesockettoclose

Example:

close(sock);


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SummarizingNetworkingin

LinuxEnvironment SupportMechanismmaybeof

Network-orientedcommunicaonInter-ProcessCommunicaon

Mayinvolve:ASpecialKindofPipeSupportforrequiredAddress FamilySupportforrequiredProtocolFamily&Socket

Type


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AddressFamily

Description

UNIX Unix domain sockets

INET Internet address family support TCP(UDP)/IP

AX25 Amateur radio X25

IPX Novell IPX

APPLETALK Appletalk DDP

INET6Internet address family support TCP(UDP)/

IPv6


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Socket Type Description

Stream Reliable, Sequenced, LikeTCP

Datagram Unreliable, Not sequenced,Like UDP

Reliable DeliveredMessages

Like datagram but reliable

Sequenced Packet Like Stream but fixed sizepacket


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BSD Sockets

INET Sockets

TCP UDP

IP

PPP SLIP Ethernet

ARP

User

Kernel

Network

Applications

Socket Interface

Protocol Layers

Network Devices


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TheINETLayer

BSDSocketApartofVFSinodeAsocketcanbeoperatedjustthesameasafileby

systemcallread(),write(),lseek()

INETLayerusesockdatastructuretohandleBSDsocket


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LetslookatsomeCcodethatwas

usedforcreaonofaTCP-basedEcho

Serverprogram!


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ATCP-basedEchoServer,wri^eninC


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ATCP-basedEchoServer.


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ATCP-basedEchoServer.


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LetslookatsomemoreCcode

thatwasusedforcreaonofaTCP-basedEchoClientprogram!


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ThisishowaCprogramforNSlookup

maylooklike!


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ATCP-basedEchoClient,wri^eninC


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ATCP-basedEchoClient


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Wheretofindmorehelp?

AgoodintroducontosocketsprogramminginCisTCP/IPSocketsinC,byMichaelJ.DonahooandKennethL.Calvert(Morgan-Kaufmann,2001).

TheUNIXSystemsSupportGroupdocumentNetworkLayersexplainsthefunconsofthelowernetworklayers.

TheTransmissionControlProtocol(TCP)iscoveredinRFC793.

TheUserDatagramProtocol(UDP)isthesubjectofRFC768.

YoucanfindalistofwidelyusedportassignmentsattheIANA(InternetAssignedNumbersAuthority)Website. And,then,youhavebooksbyW.RichardStevensandDoug

Comerasdiscussedinthemorningsession!


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AUDPServerClientInteracon


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Briefly revisiting the TCP/IP Architecture Current State-of-the-art and Evolving Research

Directions From Clusters and Grids to Clouds Wearable Computing Ubiquitous or Pervasive Computing


Interaction Points


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Current State-of-the-art and Evolving ResearchDirections

From Clusters and Grids to Clouds Wearable Computing Ubiquitous or Pervasive Computing


Interaction Points

Of Cl G id d Cl d A


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OfClusters,GridsandCloudsA

briefintroducon Networks: Asetofautonomouscompute/communicaonnodesinterconnectedforthe

purposeofmeaningfulresourcesharing,requiresupporngprotocolstacks,not

transparenttotheusers

Clusters Homogeneous(plaorm/OS),allinvolvednodesoenbelongtoasingleenty

andfrequentlydesignedforhigh-performancecompung,maybelimitedtoone

ormorerackswithinthesameroom(example:HPCclusters),easiesttodeploy

andmanage

Grids Oenheterogeneous(plaorm/OS),Frequentlyspreadovermulplenetworks

andnetworktypes,mayinvolvesingleormulpleorganizaons,requiregreatereffortindeploymentandadministraon

Clouds Maybepublic,privateandhybrid,supportmulplelevelsofabstracons/

virtualizaon,typicallyspreadoverwideareas,expectedtobetransparenttothe

user,offerthehighestlevelsofredundancy/availability,

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,BITSPilan

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Afewpointsofsignificance

Virtualizaonistheunderlyingcommontechnologyinvolvedinallthethreeparadigms

Networkingisthekeyenableringredientineachofthesecases

Cost-effecveness,robustnessandscalabilityimproveaswemovefromclustertocloudbut

overheadsandinternalcomplexityaddup

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Types of Clouds & Associated


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TypesofClouds&Associated

Virtualizaon

TypesofClouds:Classificaon-1 PublicClouds(mul-tenancy,widevariaons,mul-

service,on-demandcapacityaddionacommonfeature)

PrivateClouds(singletenancy,limitedvariaons,highercapitalinvestments,greatercontrol,moresecure)

HybridClouds(near-opmalbestofbothworlds,ifconfiguredwell)

TypesofClouds:Classificaon-2 InfrastructureCloud,ComputaonalCloudetc.

TypesofClouds:Classificaon-3 Plaormasaservice,Sowareasaservice,Storageasa

service,Collaboraon&SharingServicesetc.

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,BITSPi

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INDIA


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Case-StudyofofaNetwork-BasedMul-siteCollaboraonSystemDesign


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Project BITS-Connect 2.0


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WearableCompungElements

January30,2013 (c)Dr.RahulBanerjee,BITSPilani,INDIA


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Paradiso&StarnersShoesfor

ElectricalEnergyGeneraon



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PervasiveCompungwithAR



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References

Larry L. Peterson & Bruce S. Davie: Computer Networks: A Systems Approach,Fifth Edition, Morgan Kaufmann / Elsevier, New Delhi, 2011.

S. Keshav: Computer Networking: An Engineering Approach, PearsonEducation, New Delhi, 1997.

A. S. Tanenbaum: Computer Networks, Fifth Edition, Pearson Education, NewDelhi, 2012.

Y. Zheng and S. Akhtar: Networks for Computer Scientists and Engineers,Oxford University Press, New York, 2002.

A. Leon Garcia and I. Widjaja: Communication Networks: FundamentalConcepts and Key Architectures, Second Edition, Tata McGraw-Hill, New Delhi,2004.

Mohammed G. Gouda: Elements of Network Protocol Design, Wiley StudentEdition, John Wiley & Sons (Pte.) Ltd., Singapore, 2004. Thomas G. Robertazzi: Computer Networks and Systems: Queuing Theory andPerformance Evaluation, Third Edition, Springer-Verlag, New York, 2000.

30/01/13 (c)Dr.RahulBanerjee,BITSPilani,INDIA 52


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What is next?

Subsequentlecturesshallintroduceyoutothefollowingtopics:

Topologiesinvolved Performance

QualityofService Reliability Security

ProtocolsandMechanismsinvolvedMethodsofSimulaonSengupaphysicalsystemandconfiguringitNetworkAnalysis



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References

Larry L. Peterson & Bruce S. Davie: Computer Networks: A Systems Approach,Fifth Edition, Morgan Kaufmann / Elsevier, New Delhi, 2011.

S. Keshav: Computer Networking: An Engineering Approach, PearsonEducation, New Delhi, 1997.

A. S. Tanenbaum: Computer Networks, Fifth Edition, Pearson Education, NewDelhi, 2012.

Y. Zheng and S. Akhtar: Networks for Computer Scientists and Engineers,Oxford University Press, New York, 2002.

A. Leon Garcia and I. Widjaja: Communication Networks: FundamentalConcepts and Key Architectures, Second Edition, Tata McGraw-Hill, New Delhi,2004.

Mohammed G. Gouda: Elements of Network Protocol Design, Wiley StudentEdition, John Wiley & Sons (Pte.) Ltd., Singapore, 2004.

Thomas G. Robertazzi: Computer Networks and Systems: Queuing Theory andPerformance Evaluation, Third Edition, Springer-Verlag, New York, 2000.

Dr. Rahul Banerjee, BITS, Pilani (India)30/01/13 (c)Dr.RahulBanerjee,BITSPilani,INDIA 54


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BITS PilaniPilani | Dubai | Goa | Hyderabad

Rahul Banerjee

Thank you for your kind attention!


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CreangaBSDSocket

Forbothclientandserver:

Syntaxtakestheform:intsocket(intfamily,inttype,intprotocol)

e.g.

fd=Socket(AF_INET,SOCK_STREAM,0);

files struct


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files_structcount

close_on_exec

open_fs

fd[0]

fd[1]

fd[255]

filef_mode

f_pos

f_flags

f_count

f_owner

f_op

f_inode

f_version

inode

sock

socket

type

protocol

data (sk)

typeprotocol

socket

SOCK_STREAM

SOCK_STREAM

Address Family

socket operations

BSD Socket

File Operationslseekreadwriteselectioctlclosefasync

Linux BSD Socket Data Structure


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BindinganAddress

OnlyforServer:

Intbind(intsockfd,conststructsockaddr*address,size_tadd_len)

PortNumberisoponalforbinding socket.socket_state=TCP_CLOSE;Theboundsocketcantbeusedforothercommunicaon


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BindinganAddress(cont.)

Theboundaddrwassavedinsock.rcv_saddr UDPmaintainsahashtableudp_hashtoallocateUDPport

TCPdoesntaddthebindingsocktohashtableduringbindingoperaon


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Listening

Onlyforserver:

intlisten(intsockfd,intqueue_size) socket.socket_state=TCP_LISTEN;

Addsthesocktotcp_bound_hashandtcp_listening_hash

Aerreceivingclientsrequest:

ServerbuildsanewsockServerclonestheincomingsk_buffandqueuesittothelisteningsock.receive_queue


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Connecng

Onlyforclient:

Beforeconnecng,socket.socket_state=SS_UNCONNECTED;

Intconnect(intcsockfd,conststructsockaddr*address,size_tadd_len)

Addsthesocktotcp_listening_hashwaingforserversresponse


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Accepng

Onlyforserver: intaccept(intsockfd,structsockaddr*address,size_t*add_len)

Anewsocketgetsclonedfromthelisteningsocket

IftherearenoincomingconnecontoacceptNon-Blockingacceptoperaonfailedandthrow

awaythenewsocketBlockingacceptoperaonwasaddedtothewait

queue


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next

prev

dev

head

data

tailend

Packet to be

transmitted

sk_bufferstructure

truesizelen

PushPullPutTrim

How does a WAN Look Like?


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HowdoesaWANLookLike?

Architecture of the Internet 1 f 2


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ArchitectureoftheInternet1of2

Brief Historical Notes: Initiated by the US Department of Defense (DoD) through its

Advanced Research Project Agency (ARPA) and was hence calledARPANet.

Originally, it was a point-to-point WAN involving only four nodesacross the USA.

Original architecture that led to ARPANET has evolved over the yearsthat have passed by.

In later years, ARPA / DARPA dissociated with it and allowed to this tobe blossomed into the Global Public Internet as we see it now.

Current Status: It is loosely hierarchical.

Has no single body that owns it or rigidly controls it. ---Mostly run through volunteer efforts and by consensus.

Runs several services, in a distributed manner, includingthe immensely popular World-Wide Web.

Is helped by global cooperation including those fromgovernments and corporates apart from academia

A hit t f th I t t


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ArchitectureoftheInternet2of2

Currently, Internet architecture is designed for the best-effort delivery and is largely governed by the IAB of theInternet Society (ISoc). ISoc has many sub-organs which facilitate evolution and

coordinated maintenance of the Internet. IESG steers the ISoc in a general way the engineering issues

are resolved. IETF workgroups do the ground work and by a democratic

process helps community in building up engineering solutionsthrough IETF drafts and standards (RFCs) etc.

Currently, the TCP/IP stack is the dominant protocolstack over which the Internet runs.

Keeping the needs of expansion and improvement, thisprotocol family has continually evolved over last 30+years. Current version of IP is IPv6, although IPv4 is still dominant in

use.

Wh t i th I t t t d ?


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WhatistheInternettoday?

Wide Area Network of variety of networks Global Public Not transparent, as yet Hybrid topology but largely hierarchical No single controller Internet Society (ISoc) oversees, assists ---

does not control QoS, Security continue to have issues partly at

least Web, mail, commerce, education, entertainment,

sharing continue to dominate its applicationspace

Project BITS-Connect 2 0


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Project BITS-Connect 2.0

The Immersive Tele-presence Rooms

This is how an18-seater

immersive tele-

presence room

looks like at all

the Indiancampuses.

Chancellorsofficeisequippedwith

onetwo-seatersystem

A F M N ki T


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(c)Dr.RahulBanerjee,BITS,

Pilani,India 69

A Few More Networking Terms

Repeaters / Repeater Hubs / Shared Hubs: where usually Physicallayer / level exist with L1-protocol data unit (raw bits) regeneration andonward transmission

Managed Hubs / Layer-2 Switching Hubs: where Physical and Data Linklayers / levels exist with ability to handle and deliver Layer-2-protocoldata unit (frame)

Bridges: where Physical and Data Link layers / levels exist with L2-protocol data unit (frame) processing and forwarding Switches: where Physical and Data Link and / or Network (sometimeseven higher) layers / levels exist with Layer-2 and / or Layer-3-protocoldata unit (frame / packet) processing, switched routing / forwarding

Routers: where Physical and Data Link and Network layers / levels existwith L3-protocol data unit (packet) processing, routing and forwarding

Gateways: where two or more different networks meet and may requireprotocol / message translation capabilities Clouds: abstraction of node connectivity in the networking context

A Bus Topology based Computer


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ABusTopologybasedComputer

Network

SHAREDBUS

(c) Dr. Rahul Banerjee, BITS-Pilani,INDIA

N1 N2 N3 N4


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Robert Metcafes Ethernet The original Ethernet protocol proposed and

implemented by Robert Metcafe was actually basedon 1-p CSMA/CD protocol

It did have a scheme that allowed greedy access tothe channel by a station which led to lower efficiency

Schemes like Random Back-off / Exponential Back-off were devised to improve the efficiency to a certainextent

30/01/13(c) Dr. Rahul Banerjee, SDET Unit,

BITS-Pilani, INDIA 71

An Ethernet LAN


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AnEthernetLAN

72(c) Dr. Rahul Banerjee,

BITS, Pilani, India

PersonalComputer

Workstaon

WorkstaonWorkstation

A Star Topology based Computer


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AStarTopologybasedComputer

Network

C

C

C

Switch


S

N1

N2

N3

N4

An Example of a Hybrid Switching Fabric


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Fixed

Lasers

Electronic

SwitchesGxG

MEMS

Group1

LxM

Crossbar

Linecard 1

Linecard 2

LinecardL

Group 2

LxM

Crossbar

Linecard 1

Linecard 2

LinecardL

LxM

Crossbar

Linecard 1

Linecard 2

LinecardL

Group G

MxL

Crossbar

Linecard 1

Linecard 2

LinecardL

Electronic

Switches

Optical

Receivers

Group 1

MxL

Crossbar

Linecard1

Linecard2

LinecardL

Group 2

MxL

Crossbar

Linecard1

Linecard 2

LinecardL

Group G

GxG

MEMS

GxG

MEMS

GxG

MEMS

1

2

3

M

Static

MEMS

1

2

3

M

1

2

3

M

1

2

3

M

1

2

3

M

1

2

3

M

1

2

3

M

AnExampleofaHybridSwitchingFabric

Dr. Nick McKeown, Stanford University

Another Form of Ethernet LAN


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AnotherFormofEthernetLAN

75(c) Dr. Rahul Banerjee,

BITS, Pilani, India

TheEthernetSwitch

PersonalComputer

NetworkPrinter

Workstaon

Workstaon

LaptopComputer

Workstaon

TabletPC

A Tree Topology based Computer


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ATreeTopologybasedComputer

Network

NC1 NC2

NC11

NR

NC21

NC22

NC12


A Ring Topology based Computer


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77

ARingTopologybasedComputer

Network

C

C

C

C

C


A Ring Topology based Computer


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78

ARingTopologybasedComputer

Network

C

C

C

C

C


S f N t k T l i


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(c) Dr. Rahul Banerjee, BITS, Pilani, India 79

SummaryofNetworkTopologies

Bus Topology Shared Switched

Tree Topology Ring Topology

Single Double

Star Topology Irregular Topology Complete Topology

Frames: Link Layer (L 2) Data Units


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Frames:LinkLayer(L-2)DataUnits

Frame TheunitofDataasexpressedattheDataLinkLayer(Layer-2oftheHypothecalmodelusedforinstrucon)isconvenonallycalledaFrame.

Framescantakedifferentformatsandsizesdependingupontheprotocolinqueson

Framesdoincludefieldslikesynchronizaon,addressing,payload,control-informaonetc.

FrameForwarding Theprocessofmovingframesfromoneporttoanotherinabridgeorswitch.

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(c) Dr. Rahul Banerjee,

BITS, Pilani, India

Frames: Factors that ma^er!


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Frames:Factorsthatma^er!

Synchronization: Transmitter & Receiver need tobe in sync

Start Delimiter: Required to mark starting bit End Delimiter: Required to mark the end bit Control Information: Information suggesting datahandling and interpretation Error Detection / Correction / Retransmission Flow Control: Required for avoiding data loss

due to overflow at receiving end Data Length: Needed if data-field is not of fixed

size

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BITS, Pilani, India

A S l F F t


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ASampleFrameFormat

n-BytePreambleStart-of-FrameDelimiterDesnaonAdd.SourceAddress

LengthofData

DataField PadField

Checksum

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BITS, Pilani, India

Logical View of a 10-Gbps Unit


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LogicalViewofa10 GbpsUnit

h^p://www.ovislinkcorp.co.uk/linkd.GIF

7 1 6 6 246=


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SummaryofDifferencesBetweenL 2Switches,

Routers(L-3)andL-3Switches

BridgesandLayer-2switchesdividethenetworkintosegmentsormicro-segments

(apartfromhelpinginLayer-2protocol

translaon,management,securityetc.) Ineffect,wecansaythat

Layer-2Switches/Bridgesseparatecollisiondomains

Layer-2Switches/Bridgescancarryoutprotocoltranslaons

30/01/13

(c)Dr.RahulBanerjee,SDETUnit,BITS-

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Summary of Differences Between L-2 Switches,


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RoutersareLayer-3deviceswhohandleLayer-3packetroungwithinandoutsidethelocalnetwork/internetworkandthereforeeffecvely

separatebroadcastdomainswhichendatitsdifferentnetworkinterfaces

eachofwhichcarriesaseparateSubnet-idenfier/Subnet-address(apart

fromLayer-3protocoltranslaon,monitoring,securityandmanagement)

Thus,ineffect,wecansaythat: RoutersSeparatebroadcastdomains(eachofsuchbroadcastdomainswhich

endatitsdifferentnetworkinterfaceseachofwhichcarriesaseparate

Subnet-idenfier/Subnet-address)

Routerscancarryoutinteriorroungand/orexteriorroung,dependingupontheirlocaoninthenetwork

Routerscancarryoutprotocoltranslaons(intermsofprotocol-specificpacketformatsaswellasintermsofallowingappropriatelyforma^ed

selecvedataspecifictoroungprotocolstheymaysupport).

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Layer-3switchesaredeviceswhichcanhandleallfunconaliesofLayer-2Switchesaswellasfast(oenbasedonheader/tag/labelswitching)Layer-3packetroungwithinbutnotoutsidethelocalnetwork/internetwork;and

therefore,effecvelyseparatebroadcastdomainswhichendatitsdifferent

LANinterfaceseachofwhichcarriesaseparateSubnet-idenfier/Subnet-

address(apartfromoponalLayer-3protocoltranslaon,monitoring,securityandmanagement)

Thus,ineffect,wecansaythat: L-3SwitchesSeparatebroadcastdomains(eachofsuchbroadcastdomainswhich

endatitsdifferentLANinterfaceseachofwhichcarriesaseparateSubnet-

idenfier/Subnet-address)

L-3Switchescancarryoutfastinteriorroung/packet-switchingoenbasedonheader/tag/labelswitching

Layer-3Switches,oponally,cancarryoutprotocoltranslaons(intermsofprotocol-specificpacketformats).

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Inside a Layer-2 Switch


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InsideaLayer-2Switch

ElementsofaLayer-2Switch Processors(Front-endProcessorsonLineCards)for

FrameRoung

MulpleBuffersforMulpleQueues SharedI/OBusorRing(1st/2ndGen.)/Switching

Fabric(3rdGen.)

I/PLineControllers(ILC)

O/PLineControllers(OLC)

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Some More Terms of Relevance


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SomeMoreTermsofRelevance Collision Domain

The set of all stations connected to a networkwhere faithful detection of a collision can occur.

A collision domain terminates at a switch port. Late Collision

A failure of the network in which the collisionindication arrives too late in the frametransmission to be automatically dealt with by themedium access control (MAC) Protocol.

The defective frame may not be detected by allstations requiring that the application layer detectand retransmit the lost frame, resulting in greatlyreduced throughput.

CRCCyclic Redundancy Check is an error-checking

technique used to ensure the fidelity of receiveddata.

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E F b i f W bl G t


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E-FabricofaWearableGarment


Wi l C i i W bl


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WirelessCommunicaoninWearables


U I t f & S


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UserInterface&Sensors



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TCP/IP M d l


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TCP/IPModel

OSI TCP/IP

Application

Presentation

Session

Transport

Network

Data Link

Physical

Application

Transport

Internet

Host-to-Network

7

6

5

4

3

2

1

TCP

IP

TCP O i


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TCPOverview

TCP(TransmissionControlProtocol)Connecon-OrientedReliableProtocol

UDP(UserDatagramProtocol)ConneconlessUnreliableProtocol

IP Overview


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IPOverview

32-bitUniqueIPAddressNetworkAddressSubnetAddressHostAddress

140.112.28.XX 140.112.30.XX

Gateway

(Router)

CSC461-CN-Lecture-8-Jan-30-2013

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