Introduction

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TOC: IntroductionNetwork ExamplesNetwork Components EthernetInterconnected LANsInternetworkTypes of NetworksInternetPacketsTransport

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Introduction: Network Examples

UCBBackbone: Teleglobe Global Crossing Williams

Regional: Palo AltoTypes of NetworksInternetPacketsTransport

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Network Examples: UCB

E1E2

E3

REGIONAL1st Floor Cory

2nd FloorCory

SODA

EVANS

BACKBONE

CAMPUS

LOCAL

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Network Examples: BackboneTeleglobe Communications Corporation – Fiber + Satellite

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Network Examples: BackboneGlobal Crossing Corporation

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Network Examples: BackboneWilliams Communications

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Network Examples: RegionalPalo Alto Network

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Introduction: Network Components

Links: carry bits from one place to another (or maybe to many other places)Interface: attaches device to linkSwitch/router: interconnect linksHost: communication endpoint (workstation, PDA, cell phone, toaster, tank) – connected to links

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Network Components: Links

Fibers

Cat5 UnshieldedTwisted Pairs

Coaxial Cable

Wireless

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Network Components: NIC

Ethernet Network Interface Card

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Network ComponentsTelephone Switch Large Router

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Introduction: EthernetEthernet is a Local Area Network (LAN)

• Architecture: Switch and/or Hub

• System View: Services

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Ethernet: ArchitectureSwitch and/or Hub:

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Ethernet: System ViewEthernet is a broadcast-capable, multi-access LANProvides a “Link” service between nodes

Abstract view:

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Introduction: Interconnected LANsLANs interconnected by routers

LAN1

LAN2

LAN3Internet

R1R2

R3 R4

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Introduction: InternetworkProvides message delivery between multiple networks that may belong to different organizations:

Subnet 1Subnet 2

ISP 2ISP 1

Example: Subnet 1 = network of LANs of previous slideISP 1 = Sprint, ISP 2 = MCISubnet 2 = UCB network

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Introduction: Types of Network

Classification 1: Size, Information, Application

Classification 2: Use, Protocols, Technologies

Switching Broadcast vs. Switched Characteristics How to switch Taxonomy

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Types of Network: Classification 1

Geographical distance Local Area Networks (LAN): Ethernet, Token ring,

FDDI Metropolitan Area Networks (MAN): DQDB, SMDS Wide Area Networks (WAN): X.25, ATM, frame relay Caveat: LAN, MAN, WAN may mean different

things: Service, network technology, networks

Information type Data networks vs. telecommunication networks

Application type Special purpose networks: airline reservation

network, banking network, credit card network, telephony, CATV

General purpose network: Internet

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Types of Network: Classification 2

Right to usePrivate: enterprise networksPublic: telephony network, Internet

Protocols:Proprietary: SNA, AppleTalkOpen: IP

TechnologiesTerrestrial vs. satelliteWired vs. wireless

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Broadcast Network:

Types of Network: Broadcast vs. Switched

Switched Network:

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Broadcast One to all Examples: some LANs (Hub-Ethernet, 802.11) Problem: coordinate the access of all nodes to

the shared communication medium (Multiple Access Problem)

Switched One to subset Examples: WANs (Telephony Network, Internet) Problem: how to forward information to

intended node(s) This is done by special nodes (e.g., routers,

switches) running routing protocols

Types of Network: Characteristics

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Circuit-Switched: 1. Set up circuit between two devices2. Exchange information3. Release circuitPacket-Switched:

Send packets with source and destination addresses

Vircuit-Circuit Switched: Select path from source to destination (Virtual

Circuit) Assign a “label” to that path Send packets with that label Release Virtual Circuit

{Note: Some VCs are permanent.}

Types of Network: How to Switch?

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Based on the way in which the nodes exchange information:

Types of Network: Taxonomy

Switched Broadcast

Circuit PacketVirtualCircuit

Telephone MPLSATMFrame Relay

Sw.-EthernetInternet

Hub-EthernetCATV

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Introduction: The Internet Overview Scale

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Internet: Overview A global network of networks all using a common protocol (IP, the Internet Protocol) Focus of this class A challenge to understand: large scale (10’s of millions of users, 10’s

of thousands of networks) heterogeneity, irregular topology,

decentralized management

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Internet: Scale

• Data from www.nw.com

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Introduction: PacketsIllustrationMain Ideas

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Packets: Illustration

A

B

B → port 2

12

3A | B | ...

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Packets: Main IdeasThe switches have no memory of packets: scalabilityThe network is independent of the applications: flexibilityThe packet formats and addresses are independent of the technology: extensibility

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Introduction: Transport

Acknowledgments Link Sharing

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Transport: Acknowledgments

The destination sends back an acknowledgment for every correct packet it gets.The source uses these ACKs to- Retransmit unacknowledged packets- Adjust the rate of its transmissions.

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Transport: Link SharingShared links

The sources base theirtransmissions on when they get acknowledgments.The scheme regulates the sharing of common links