CSC461-CN-Lecture-6-Jan-23-2013

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BITS PilaniPilani | Dubai | Goa | Hyderabad

Computer NetworksLecture-6, January 23, 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

How to discover what route your data is actuallytaking during its travel across the globe? Simple basics that go into programming for the

network-based applications 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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There do exist several techniques, commands andtools for discovering the actual route a unit of data(say a packet) has taken during its travel from your

computer to the remote computer situatedanywhere else in the world.

A very common way to discover it at the user levelis through the Traceroute command / utility.

It may be known by slightly different names acrossoperating systems like traceroute, tracert etc.

Lets, now, see how does it work!

How to Discover theRoute Your Data TakesDuring Its Travel?


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On MS-Windows, itlooks like:


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On MacOS, it looks like:


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On Linux OS, it lookslike:


7/58BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

The application-processes of the simplest kindmight involve a client-server relationship.

APIs help! All network-capable Operating Systems have some application

programming interface (API) that makes application-to-applicationcommunication possible over networks without necessarily knowingintricate details of the underlying mechanisms.

University of California at Berkeleys BSD Socket API is one of themost common APIs in use for writing such applications Lets us see how things work in this case, from programmers point

of view!

Simple Basics of Programming for Network-based Applications



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 with

queue-size

Accept any incoming (passive) connection request

Basic Operations Involved



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

Overall:

Connect SendReceive .Close

Basic Operations Involved



How to discover what route your data is actuallytaking during its travel across the globe? Simple basics that go into programming for the

network-based applications 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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BITS PilaniPilani | Dubai | Goa | Hyderabad

Rahul Banerjee

Thank you for your kind attention!


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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 Student

Edition, John Wiley & Sons (Pte.) Ltd., Singapore, 2004. Thomas G. Robertazzi: Computer Networks and Systems: Queuing Theory and

Performance Evaluation, Third Edition, Springer-Verlag, New York, 2000.

23/01/13 (c) Dr. Rahul Banerjee, BITS Pilani, INDIA 12


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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 Student

Edition, John Wiley & Sons (Pte.) Ltd., Singapore, 2004. Thomas G. Robertazzi: Computer Networks and Systems: Queuing Theory and

Performance Evaluation, Third Edition, Springer-Verlag, New York, 2000.

Dr. Rahul Banerjee, BITS, Pilani (India)23/01/13 (c) Dr. Rahul Banerjee, BITS Pilani, INDIA 15


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Network Architecture &Reference Models

Architecture versus Reference Model: Asimplistic perspective: Architecture: It may be seen as a detailed

generic blueprint with unambiguous definitionsof services , interfaces , organization anddefined protocols that helps in design andimplementation of a set of relevant protocolstack / suite based network / internetwork

Reference Model: It is the same as thearchitecture minus the specifically definedreadily usable protocols.

Wednesday, 23 January 13 16(c) Dr. Rahul Banerjee, BITS-Pilani, INDIA


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The ISO OSI Reference Model

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


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A Simplified Network ReferenceModel

Host-1 Host-2

Application Layer Application Layer

Upper Layer-to- Lower Layer Interface Upper Layer-to- Lower Layer Interface

Upper Layer-to- Lower Layer InterfaceUpper Layer-to- Lower Layer Interface

Upper Layer-to- Lower Layer InterfaceUpper Layer-to- Lower Layer Interface

Same Layer -to- Same Layer Virtual Communication Interface



Same Layer -to- Same Layer

Virtual Communication Interface

Same Layer -to- Same Layer Physical Communication Interface

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


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23/01/13 (c) Dr. Rahul Banerjee, BITS Pilani, INDIA 21

Architecture of the Internet 1 of 2 Brief Historical Notes:

Initiated by the US Department of Defense (DoD) through its Advanced Research Project Agency (ARPA) and was hence called ARPANet.

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

Original architecture that led to ARPANET has evolved over the years

that 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, including

the immensely popular World-Wide Web. Is helped by global cooperation including those from

governments and corporates apart from academia


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A Bus Topology based ComputerNetwork

SHARED BUS

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

N1 N2 N3 N4


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An Ethernet LAN

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

Personal Computer

WorkstaJon

WorkstaJonWorkstation


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A Tree Topology based ComputerNetwork

NC1 NC2

NC11

NR

NC21

NC22

NC12



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A Star Topology based ComputerNetwork

C

C

C

Switch


S

N1

N2

N3

N4


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Another Form of Ethernet LAN


The Ethernet Switch

Personal Computer

Network Printer

WorkstaJon

WorkstaJon

Laptop Computer

WorkstaJon

Tablet PC


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(c) Dr. Rahul Banerjee, BITS, Pilani, India 33

Summary of Network Topologies

Bus Topology Shared Switched

Tree Topology Ring Topology

Single Double

Star Topology Irregular Topology Complete Topology


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Of Clusters, Grids and Clouds Abrief introducJon

Networks: A set of autonomous compute/communicaJon nodes interconnected for the

purpose of meaningful resource sharing, require supporJng protocol stacks, nottransparent to the users

Clusters Homogeneous (pla_orm / OS), all involved nodes o`en belong to a single enJty

and frequently designed for high-performance compuJng, may be limited to oneor more racks within the same room (example: HPC clusters), easiest to deployand manage

Grids O`en heterogeneous (pla_orm / OS), Frequently spread over mulJple networks

and network types, may involve single or mulJple organizaJons, require greatereffort in deployment and administraJon

Clouds May be public, private and hybrid, support mulJple levels of abstracJons /

virtualizaJon, typically spread over wide areas, expected to be transparent to the

user, offer the highest levels of redundancy / availability,

J a n u a r y 2 3

, 2 0 1 3

( c ) D

r . R a h u

l B a n e r j e e

, B I T S P i l a n i

, I N D I A


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A few points of signicance

VirtualizaJon is the underlying commontechnology involved in all the three paradigms

Networking is the key enabler ingredient in eachof these cases

Cost-effecJveness, robustness and scalabilityimprove as we move from cluster to cloud but

overheads and internal complexity add up

J a n u a r y 2 3

, 2 0 1 3

( c ) D

r . R a h u

l B a n e r j e e


, I N D I A

Types of Clouds & Associated


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Types of Clouds & AssociatedVirtualizaJon

Types of Clouds: ClassicaJon-1 Public Clouds (mulJ-tenancy, wide variaJons, mulJ-

service, on-demand capacity addiJon a common feature) Private Clouds (single tenancy, limited variaJons, higher

capital investments, greater control, more secure) Hybrid Clouds (near-opJmal best of both worlds, if

congured well)

Types of Clouds: ClassicaJon-2 Infrastructure Cloud, ComputaJonal Cloud etc.

Types of Clouds: ClassicaJon-3 < basis: service virtualizaJon> Pla_orm as a service, So`ware as a service, Storage as a

service, CollaboraJon & Sharing Services etc.

J a n u a r y 2 3

, 2 0 1 3

( c ) D

r . R a h u

l B a n e r j e e


, I N D I A


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Case-Study of of a Network-BasedMulJ-site CollaboraJon System Design


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Project BITS-Connect 2.0


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Project BITS-Connect 2.0The Immersive Tele-presence Rooms

This is how an18-seater immersive tele-presence roomlooks like at allthe Indiancampuses.

Chancellors officeis equipped with

one two-seatersystem


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(c) Dr. Rahul Banerjee, BITS,Pilani, India 40

A Few More Networking Terms Repeaters / Repeater Hubs / Shared Hubs: where usually Physical

layer / 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


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Copyright: Dr. Rahul BanerjeeBITS, Pilani (India)

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IPv4: The Header Structure0 31

Identification 16-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)

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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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Frames: Link Layer (L-2) Data Units

Frame The unit of Data as expressed at the Data Link Layer(Layer-2 of the Hypothe0cal model used for instruc0on) isconvenJonally called a Frame.

Frames can take different formats and sizesdepending upon the protocol in quesJon Frames do include elds like synchronizaJon,

addressing, payload, control-informaJon etc.

Frame Forwarding The process of moving frames from one port to another in a

bridge or switch.


h


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Frames: Factors that ma 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 data

handling 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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A Sample Frame Format

n-Byte Preamble Start-of -Frame Delimiter DesJnaJon Add . Source Address

Length of Data

Data FieldPad Field

Checksum



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Logical View of a 10-Gbps Unit

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

7 1 6 6 2 46=


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Summary of Differences Between L-2 Switches,Routers (L-3) and L-3 Switches

Bridges and Layer-2 switches divide thenetwork into segments or micro-segments(apart from helping in Layer-2 protocoltranslaJon, management, security etc.)

In effect, we can say that Layer-2 Switches / Bridges separate collision

domains Layer-2 Switches / Bridges can carry out protocol

translaJons

23/01/13 (c) Dr. Rahul Banerjee, SDET Unit, BITS-Pilani, INDIA 47


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Routers are Layer-3 devices who handle Layer-3 packet rouJng within andoutside the local network / internetwork and therefore effecJvelyseparate broadcast domains which end at its different network interfaceseach of which carries a separate Subnet-idenJer / Subnet-address (apartfrom Layer-3 protocol translaJon, monitoring, security and management)

Thus, in effect, we can say that: Routers Separate broadcast domains (each of such broadcast domains which

end at its different network interfaces each of which carries a separateSubnet-idenJer / Subnet-address )

Routers can carry out interior rouJng and / or exterior rouJng, depending

upon their locaJon in the network Routers can carry out protocol translaJons (in terms of protocol-specic

packet formats as well as in terms of allowing appropriately forma edselecJve data specic to rouJng protocols they may support).



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Layer-3 switches are devices which can handle all funcJonaliJes of Layer-2Switches as well as fast (o`en based on header/tag/label switching) Layer-3packet rouJng within but not outside the local network / internetwork; andtherefore, effecJvely separate broadcast domains which end at its differentLAN interfaces each of which carries a separate Subnet-idenJer / Subnet-

address (apart from opJonal Layer-3 protocol translaJon, monitoring, securityand management)

Thus, in effect, we can say that: L-3 Switches Separate broadcast domains (each of such broadcast domains which

end at its different LAN interfaces each of which carries a separate Subnet-

idenJer / Subnet-address ) L-3 Switches can carry out fast interior rouJng / packet-switching o`en based on

header/tag/label switching

Layer-3 Switches, opJonally, can carry out protocol translaJons (in terms ofprotocol-specic packet formats).



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Inside a Layer-2 Switch

Elements of a Layer-2 Switch Processors (Front-end Processors on Line Cards) for

Frame RouJng

MulJple Buffers for MulJple Queues

Shared I/O Bus or Ring (1 st / 2 nd Gen.) / SwitchingFabric (3 rd Gen.)

I/P Line Controllers (ILC)

O/P Line Controllers (OLC)

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


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Fixed

Lasers

Electronic

Switches G xG

MEMS

Group 1

L x M Crossbar

Linecard 1

Linecard 2

Linecard L

Group2

L x M Crossbar

Linecard 1

Linecard 2

Linecard L

L x M Crossbar

Linecard 1

Linecard 2

Linecard L

Group G

M x L Crossbar

Linecard 1

Linecard 2

Linecard L

Electronic

Switches

Optical

Receivers

Group1

M x L Crossbar

Linecard 1

Linecard 2

Linecard L

Group 2

M x L Crossbar

Linecard 1

Linecard 2

Linecard L

Group G

G xG

MEMS

G xG MEMS

G xG MEMS

1

2

3

M

StaticMEMS

12

3

M

1

2

3

M

1

2

3

M

1

2

3

M

1

2

3

M

1

2

3

M

An Example of a Hybrid Switching Fabric

Dr. Nick McKeown , Stanford University


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Some More Terms of Relevance 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.

CRC Cyclic Redundancy Check is an error-checking

technique used to ensure the fidelity of receiveddata.

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


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Pervasive CompuJng with AR

anuary 23, 2013 (c) Dr. Rahul Banerjee, BITS Pilani, INDIA


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Wearable CompuJng Elements



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E-Fabric of a Wearable Garment



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Wireless CommunicaJon in Wearables



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User Interface & Sensors



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Paradiso & Starners Shoes forElectrical Energy GeneraJon

CSC461-CN-Lecture-6-Jan-23-2013

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