1 emerging internet technologies harish sethu department of electrical and computer engineering...

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Emerging Internet Emerging Internet TechnologiesTechnologies

Harish SethuHarish SethuDepartment of Electrical and Computer Department of Electrical and Computer

EngineeringEngineeringDrexel UniversityDrexel University

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Introduction and HistoryIntroduction and History

More rapid growth than any medium in More rapid growth than any medium in historyhistory

New applications in education, business and New applications in education, business and medicine medicine

Impact on entertainment, politics and the Impact on entertainment, politics and the day-to-day lives of peopleday-to-day lives of people

Internet still very young, and rapidly Internet still very young, and rapidly evolving.evolving.

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Introduction and History Introduction and History (Cont’d)(Cont’d)

The OriginThe Origin

Began as ARPANET in 1969 for the purpose of sharing Began as ARPANET in 1969 for the purpose of sharing computing resourcescomputing resources

ARPANET was funded by the Department of DefenseARPANET was funded by the Department of Defense Met with resistance even by university research groups Met with resistance even by university research groups

who did not wish to be linked to the ARPANETwho did not wish to be linked to the ARPANET Used packet switching as opposed to circuit switchingUsed packet switching as opposed to circuit switching

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Circuit SwitchingCircuit Switching

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Circuit SwitchingCircuit Switching

Physical connection established between Physical connection established between communicating end-points.communicating end-points.

Requires setting up the connection before Requires setting up the connection before communicationcommunication

Guaranteed bandwidthGuaranteed bandwidth Predictable and bounded delayPredictable and bounded delay

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Packet SwitchingPacket Switching

No physical connection established between No physical connection established between communicating end-points.communicating end-points.

Data is sent in blocks called packetsData is sent in blocks called packets Each packet is routed independentlyEach packet is routed independently

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Packet SwitchingPacket Switching

Packet 1Packet 2

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Packet Switching vs. Circuit SwitchingPacket Switching vs. Circuit Switching

Packets may arrive out-of-orderPackets may arrive out-of-order Packets may be dropped, since network does not Packets may be dropped, since network does not

guarantee bandwidthguarantee bandwidth Packet switching analogous to how we share road Packet switching analogous to how we share road

spacespace

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The origins of packet switchingThe origins of packet switching

The roles of Leonard Kleinrock, Paul Baran and The roles of Leonard Kleinrock, Paul Baran and Donald DaviesDonald Davies

BBN’s proposal to use packet switching for BBN’s proposal to use packet switching for ARPANETARPANET

The travails of packet switchingThe travails of packet switching

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MilestonesMilestones

EthernetEthernet TCP/IPTCP/IP E-mailE-mail Commercialization of the InternetCommercialization of the Internet World Wide WebWorld Wide Web

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Internet OrganizationsInternet Organizations

The Internet SocietyThe Internet Society The Internet Architecture BoardThe Internet Architecture Board The Internet Engineering Task ForceThe Internet Engineering Task Force The Internet Engineering Steering GroupThe Internet Engineering Steering Group ICANNICANN

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Protocol LayeringProtocol Layering

What is a protocol?What is a protocol? What is protocol layering?What is protocol layering? The analogy to postal service.The analogy to postal service. Why use protocol layering?Why use protocol layering?

Simplicity in designSimplicity in design Flexibility in accommodating new technologiesFlexibility in accommodating new technologies Compatibility of applications to systemsCompatibility of applications to systems

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Protocol Layering (Cont’d)Protocol Layering (Cont’d)

A common implementationA common implementation

Application Layer

Transport Layer

Network Layer

Access Layer

Physical Layer

Application Layer

Transport Layer

Network Layer

Access Layer

Physical Layer

Application protocol, e.g., HTTP

Transport protocol, e.g., TCP

Network protocol, e.g., IP

Network access protocol, e.g., Ethernet

Physical medium, e.g. copper

System 1 System 2

Application Layer

Transport Layer

Network Layer

Access Layer

Physical Layer

Application Layer

Transport Layer

Network Layer

Access Layer

Physical Layer

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Switches and RoutersSwitches and Routers

What is a switch and what is a router?What is a switch and what is a router? The problem with achieving performanceThe problem with achieving performance The need for buffersThe need for buffers

0

1

0

1

0

1

0

1

Before After

Packet headed to output 0Packet headed to output 1

0

1

0

1

0

1

0

1

Before After

(a)

(b)

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Switches and Routers Switches and Routers (Cont’d)(Cont’d)

Input queueing and output queueingInput queueing and output queueing

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Head-of-line blocking with input queueingHead-of-line blocking with input queueing

Packet headed to output 0


0

1

End of Cycle 1

0

1

End of Cycle 2

0

1

0

1

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Output queueing and head-of-line blockingOutput queueing and head-of-line blocking

0

1

End of Cycle 2

0

1

0

1

End of Cycle 1

0

1



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Commercial switches and routersCommercial switches and routers

Use both input and output queueingUse both input and output queueing Use shared buffer for output queueingUse shared buffer for output queueing Use complex buffer organizations and queue Use complex buffer organizations and queue

management strategiesmanagement strategies

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Virtual Circuit SwitchingVirtual Circuit Switching

Establishes a virtual circuitEstablishes a virtual circuit Routes using a virtual circuit identifier on Routes using a virtual circuit identifier on

each packeteach packet Packets with same identifier routed Packets with same identifier routed

identically by a switchidentically by a switch Facilitates easy management of flows of Facilitates easy management of flows of

traffictraffic

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Virtual Circuit Switching Virtual Circuit Switching (Cont’d)(Cont’d)

Asynchronous Transfer Mode (ATM)Asynchronous Transfer Mode (ATM)

Uses virtual circuitsUses virtual circuits Proposed for providing performance guarantees as Proposed for providing performance guarantees as

in circuit switching using the packet switching in circuit switching using the packet switching technologytechnology

Largely used today in the Internet backboneLargely used today in the Internet backbone

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RoutingRouting

What is routing?What is routing? What is a route table?What is a route table? What is a “best” route?What is a “best” route?

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Routing (Cont’d)Routing (Cont’d)

Link State RoutingLink State Routing

Periodically measure cost to each neighborPeriodically measure cost to each neighbor Distribute measurements to all routers in the Distribute measurements to all routers in the

networknetwork Each router has complete and current information Each router has complete and current information

on the topologyon the topology Each router independently computes the “best” pathEach router independently computes the “best” path

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Distance-Vector RoutingDistance-Vector Routing

Each router maintains a distance-vector, the cost to Each router maintains a distance-vector, the cost to reach each destination from itself.reach each destination from itself.

Exchanges distance-vectors with neighborsExchanges distance-vectors with neighbors Determines the “best” path neighbor to reach Determines the “best” path neighbor to reach

destinationdestination

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Routing in the InternetRouting in the Internet

Distance-vector routing used in the Internet core Distance-vector routing used in the Internet core (BGP)(BGP)

Link-state routing used within domains (OSPF)Link-state routing used within domains (OSPF) Border routers use bothBorder routers use both

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Flow Control and Congestion Flow Control and Congestion AvoidanceAvoidance

What is flow control?What is flow control? What is congestion avoidance?What is congestion avoidance? Design goals: Design goals:

responsivenessresponsiveness performanceperformance scalabilityscalability simplicitysimplicity fairnessfairness

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Flow Control and Congestion Flow Control and Congestion Avoidance (Cont’d)Avoidance (Cont’d)

Flow control strategiesFlow control strategies

Open loop flow controlOpen loop flow control No feedbackNo feedback Pre-arranged self-regulation at the sourcePre-arranged self-regulation at the source

Closed loop flow controlClosed loop flow control Self-regulation based on feedbackSelf-regulation based on feedback

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Open loop flow controlOpen loop flow control

Traffic descriptorsTraffic descriptors Token bucket regulatorToken bucket regulator

token generationtoken generation bucket capacitybucket capacity

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Token bucket regulatorToken bucket regulator

Before

Network Network

After

Packets

Tokens

TokenBucket

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Closed loop flow controlClosed loop flow control

TCP uses closed loop flow controlTCP uses closed loop flow control slow-start phase in TCP (exponential rate increase)slow-start phase in TCP (exponential rate increase) congestion-avoidance phase in TCP (linear rate congestion-avoidance phase in TCP (linear rate

increase)increase) time-outs and back-offtime-outs and back-off

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A typical saw-tooth graph of TCP sending rateA typical saw-tooth graph of TCP sending rate

Time

Threshold

Time-out occursdue to congestion

Exponential increase

LinearIncrease

TCP

Send

ing

rate

New threshold

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Problems with TCPProblems with TCP

Does not avoid congestion, reacts only after Does not avoid congestion, reacts only after congestion congestion

Assumes time-outs are always due to congestionAssumes time-outs are always due to congestion Always keeps pushing the network into congestionAlways keeps pushing the network into congestion

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Random Early Detection (RED)Random Early Detection (RED)

Defines router actions designed to work with TCPDefines router actions designed to work with TCP Goal is congestion avoidance, at good performanceGoal is congestion avoidance, at good performance Detects impending congestion based on queue lengthDetects impending congestion based on queue length Drops packets before congestion occursDrops packets before congestion occurs Triggers TCP to cut down its rate before it causes Triggers TCP to cut down its rate before it causes

congestioncongestion Used in most Internet routers todayUsed in most Internet routers today

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Emerging Architectures and Emerging Architectures and ServicesServices

Onslaught of multimedia trafficOnslaught of multimedia traffic Need for service beyond best effortNeed for service beyond best effort What is Quality of Service?What is Quality of Service?

throughput guaranteethroughput guarantee delay bound delay bound delay-jitter bounddelay-jitter bound

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Fairness in Traffic ManagementFairness in Traffic Management

The most basic guarantee: fairness.The most basic guarantee: fairness. Why not just first-come-first-serve?Why not just first-come-first-serve? Why not just packet-by-packet round-robin Why not just packet-by-packet round-robin

scheduling?scheduling?

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Fairness in Traffic Fairness in Traffic Management (Cont’d)Management (Cont’d)

What is fair and how to be fair?What is fair and how to be fair?

All flows with unsatisfied demands should get an equal All flows with unsatisfied demands should get an equal share of the resourceshare of the resource

No flow should be allocated more resources than its No flow should be allocated more resources than its demanddemand

Fair queueing is a technique that achieves the above two Fair queueing is a technique that achieves the above two conditions for fairness to a satisfactory extent.conditions for fairness to a satisfactory extent.

Most Internet routers now implement some version of a Most Internet routers now implement some version of a fair queueing discipline.fair queueing discipline.

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The Integrated Services The Integrated Services ModelModel

A new architectural framework to facilitate QoS in A new architectural framework to facilitate QoS in the Internet.the Internet.

Applications describe their traffic to the network, Applications describe their traffic to the network, and their demand for QoSand their demand for QoS

Network decides if the demand can be satisfied Network decides if the demand can be satisfied before admitting the application trafficbefore admitting the application traffic

Routers reserve bandwidths and buffers necessary to Routers reserve bandwidths and buffers necessary to satisfy demandsatisfy demand

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The Integrated Services The Integrated Services Model (Cont’d)Model (Cont’d)

Flow specificationsFlow specificationsTSpecTSpec

burst sizeburst size long-term average ratelong-term average rate maximum packet sizemaximum packet size peak ratepeak rate

RSpecRSpec service rateservice rate delay bounddelay bound packet loss probabilitypacket loss probability

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Service ClassesService Classes Guaranteed serviceGuaranteed service

Provides hard guaranteesProvides hard guarantees Requires per-flow management in the routersRequires per-flow management in the routers Suffers from scalability problemsSuffers from scalability problems

Controlled Load ServiceControlled Load Service Service similar to best-effort in a lightly loaded networkService similar to best-effort in a lightly loaded network Meant for applications that can tolerate some loss or delayMeant for applications that can tolerate some loss or delay Requires application to specify traffic descriptionRequires application to specify traffic description Network decides whether or not to admit a new flow for controlled Network decides whether or not to admit a new flow for controlled

load serviceload service

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Signaling (RSVP)Signaling (RSVP)

RSVP is an IP signaling protocolRSVP is an IP signaling protocol Uses two messages: Path and ResvUses two messages: Path and Resv Path messages go from the sender to the receiver, Path messages go from the sender to the receiver,

containing traffic descriptioncontaining traffic description Resv messages go from receiver to the sender, Resv messages go from receiver to the sender,

containing QoS requirementscontaining QoS requirements

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Flow of Path and Resv messagesFlow of Path and Resv messages

Sender

Receiver 1

Receiver 3

Path

Path

Path

Path

Path

Path

Path

Path Resv

Resv

Resv

Resv

ResvResv

Resv

Resv

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Multicasting with RSVPMulticasting with RSVP

RSVP explicitly designed for multicastRSVP explicitly designed for multicast Multicast method based on data replication in the Multicast method based on data replication in the

networknetwork Allows merging of Resv requestsAllows merging of Resv requests RSVP is a soft-state protocolRSVP is a soft-state protocol

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The Differentiated Services The Differentiated Services ModelModel

Differentiated Serevices model is more scalable.Differentiated Serevices model is more scalable. Traffic is divided into classesTraffic is divided into classes Resources allocated on a per-class basis instead of a Resources allocated on a per-class basis instead of a

per-flow basisper-flow basis Defines a set of Per-Hop Behaviors (PHBs)Defines a set of Per-Hop Behaviors (PHBs) Service by the network based on the PHB carried in Service by the network based on the PHB carried in

the packetthe packet Standard PHBsStandard PHBs

Expedited ForwardingExpedited Forwarding Assured ForwardingAssured Forwarding

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The Differentiated Services The Differentiated Services Model (Cont’d)Model (Cont’d)

Expedited Forwarding (EF-PHB)Expedited Forwarding (EF-PHB)

A request to forward the packet as quickly as A request to forward the packet as quickly as possiblepossible

Meant for applications with stringent delay Meant for applications with stringent delay requirementsrequirements

Requires strict regulation at sourceRequires strict regulation at source Requires careful capacity planningRequires careful capacity planning

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Assured Forwarding (AF-PHB)Assured Forwarding (AF-PHB)

Delivers with high assurance (a weaker guarantee)Delivers with high assurance (a weaker guarantee) Consists of 4 classes and 3 drop precedence levelsConsists of 4 classes and 3 drop precedence levels In-order delivery within each classIn-order delivery within each class Drop precedence defined at the source endDrop precedence defined at the source end

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A potential DiffServ scenarioA potential DiffServ scenario

Internet backbone network

Hosts

Drexel University DS Domain

Border router

Hosts

Service Level Agreement madeon aggregated rate

ISP router

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Multi-Protocol Label Multi-Protocol Label SwitchingSwitching

Uses the concept similar to that of virtual circuits in IPUses the concept similar to that of virtual circuits in IP Uses fixed-size labelsUses fixed-size labels Originally designed to facilitate sending IP packets over ATMOriginally designed to facilitate sending IP packets over ATM Packets are routed based on the label, instead of destination Packets are routed based on the label, instead of destination

address.address. Supported by high-end routers todaySupported by high-end routers today Achieves lower header overheadAchieves lower header overhead

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Multi-Protocol Label Multi-Protocol Label Switching (Cont’d)Switching (Cont’d)

Achieves separation of control and forwarding Achieves separation of control and forwarding components:components:

Routing Protocols

Routing Tables

Updates to/from other routers

Updates to/from other routers

Forwarding Tables

Forwarding Fabric

Packets with labels

Packets with labels

Control Component

Forwarding Component

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A limitation of traditional routing:A limitation of traditional routing:

1

2

3

4

5

6

B

AA & B A & B

Point ofCongestion

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MPLS extends routing functionality:MPLS extends routing functionality:

1

2

3

4

5

6

B

A A A

BB

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Concluding RemarksConcluding Remarks

Internet is still evolving, and very rapidly.Internet is still evolving, and very rapidly. Service requirements of applications may Service requirements of applications may

change; new solutions such as active change; new solutions such as active networking are emerging.networking are emerging.

Engineering the Internet continues to be both Engineering the Internet continues to be both challenging and rewarding.challenging and rewarding.

1 emerging internet technologies harish sethu department of electrical and computer engineering...

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