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Introduction to LANIntroduction to LANTDC 363TDC 363

Week 4Week 4

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Connecting LAN to WANConnecting LAN to WANBook: Chapter 7Book: Chapter 7

OutlineOutlineWide Area Network (WAN): definitionWide Area Network (WAN): definitionWAN TopologiesWAN TopologiesChoices of WAN technologiesChoices of WAN technologies

DialDial--upupISDNISDN

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T1T1Frame RelayFrame RelayDSLDSL

Remote network connectionsRemote network connectionsMidtermMidterm

What is WAN?What is WAN?Internet and IntranetInternet and Intranet

Private

PublicNetwork

HomeBranchOffice

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Network

Headquarters BranchOffice

BranchOffice

Remote

1. Relatively long physical distance 2. Requiring a service provider (carrier)

Remote

2

WAN InterfaceWAN Interface

CPE

E t i N t k

Customerrouter

D ti

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Internet/ Internet

Carrier Network

Enterprise Network

CentralOfficeISP

Demarcationpoint

WAN TopologiesWAN Topologies

Wide area network (WAN) topologiesWide area network (WAN) topologiesPeerPeer--toto--peerpeerRingRingSt rSt r

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StarStarMeshMeshTiered (Hierarchy)Tiered (Hierarchy)

Wide Area Network (WAN) Wide Area Network (WAN) Topologies (bus)Topologies (bus)

T1

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Note: You cannot use DSL for interoffice communications.

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Ring Topology on WANRing Topology on WANEach site is connected to two other sites so that Each site is connected to two other sites so that entire WAN forms a ring patternentire WAN forms a ring pattern

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ISDN

Star Topology on WANStar Topology on WAN

Single site acts as the central connection point for Single site acts as the central connection point for several other pointsseveral other points

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Meshed Topology on WANMeshed Topology on WANMany directly interconnected locations forming a complex Many directly interconnected locations forming a complex meshmesh

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Tiered Topology on WANTiered Topology on WANSites connected in star or ring formations are interconnected at Sites connected in star or ring formations are interconnected at different levels, with interconnection points organized into different levels, with interconnection points organized into layerslayers

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WAN TechnologyWAN Technology

DialDial--up (PSTN)up (PSTN)

ISDN (BRI)ISDN (BRI)ISDN (PRI) ISDN (PRI) –– voice onlyvoice onlyX 25X 25 out of dateout of date

xDSLxDSL

Cable ModemCable ModemSONET SONET –– not for not for

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X.25 X.25 –– out of dateout of dateFrame RelayFrame Relay

Leased Line (TLeased Line (T--carrier)carrier)

Leased Line (OCLeased Line (OC--x)x)ATM ATM –– too expensivetoo expensive

enterpriseenterprise

EthernetEthernetWirelessWireless

Technology ClassificationTechnology Classification

Leased Line

Circuit Switching

PacketSwitching

FT1 PSTN X.25

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T1/E1

DS3/T3

OC-3c

OC-x

ISDN Frame Relay

ATM

Ethernet

xDSLQ: where is IP?

5

PSTN PSTN (Public Switched Telephone Network(Public Switched Telephone Network

Designed for voice traffic (not for data traffic)Designed for voice traffic (not for data traffic)Also called Also called plain old telephone service plain old telephone service (POTS)(POTS)

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PSTN for WAN connection:PSTN for WAN connection:Modem (V.92)Modem (V.92)

Downlink: 53 kbps, uplink: 48 kbpsDownlink: 53 kbps, uplink: 48 kbps

ISDNISDN

PSTN to InternetPSTN to InternetTandem Switch

Local Switch

PSTN

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modem

Internet

Local Switch

ISDN-PRI/T1

RemoteAccess Server(modem pool)

T1

ISP

router server

ISDN BRI (Basic Rate Interface)ISDN BRI (Basic Rate Interface)International standard for transmitting data over International standard for transmitting data over digital linesdigital linesBRI: Basic Rate Interface (2B+D)BRI: Basic Rate Interface (2B+D)A variety of ISDN using two 64A variety of ISDN using two 64--kbps bearer (B) kbps bearer (B) channels and one 16channels and one 16--kbps data (D) channel, as kbps data (D) channel, as

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p ( ) ,p ( ) ,indicated by the following notation:indicated by the following notation:Through Through bondingbonding, the two 64, the two 64--kbps channels can kbps channels can be combined to achieve an effective throughput be combined to achieve an effective throughput of 128of 128--kbpskbpsISDN PRI (23B+D) over T1ISDN PRI (23B+D) over T1

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ISDN Network Connections ISDN Network Connections

BRI2B+D

PRI

Service Provider

Customer A

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PSTNCentral Office

BRI2B+D

BRI2B+D

23B+D

Customer B

Customer CCf. Fig.7-10, 7-11

TT--CarriersCarriersThe most common TThe most common T--carrier implementations are carrier implementations are T1T1and and T3T3Signal level (DS0, DS1, etc.)Signal level (DS0, DS1, etc.)

ANSI standard for TANSI standard for T--carrier technology that refers to its carrier technology that refers to its Ph i l l l t i l i li h t i tiPh i l l l t i l i li h t i ti

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Physical layer electrical signaling characteristicsPhysical layer electrical signaling characteristics

DSO (digital signal, level 0)DSO (digital signal, level 0)Equivalent of one voice channel (64K)Equivalent of one voice channel (64K)

Fractional T1 (FT1, n Fractional T1 (FT1, n ××64K)64K)Arrangement allowing an organization to use only some Arrangement allowing an organization to use only some channels on a T1 line, paying for what they usechannels on a T1 line, paying for what they use

Types of TTypes of T--CarriersCarriers

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T1: 64K×24 = 1.536 vs. (24×8+1) × 8K = 1.544M

channels: telephone calls

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TT--Carrier ConnectivityCarrier ConnectivityWiringWiring

Can use unshielded or shielded twistedCan use unshielded or shielded twisted--pair copper wiringpair copper wiringCSU/DSU (Channel Service Unit/Data Service Unit)CSU/DSU (Channel Service Unit/Data Service Unit)

CSUCSU provides termination for the digital signal and ensures connection provides termination for the digital signal and ensures connection integrity through error correction and line monitoringintegrity through error correction and line monitoringDSUDSU converts the digital signal used by CPE into the digital signal sent via converts the digital signal used by CPE into the digital signal sent via the outside cabling to the carrier.the outside cabling to the carrier.

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T1: DataT1: Data--only Serviceonly Service

CSU/DSU

T1Enterprise Network

Customerrouter

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Internet

multiplexer

T1

channelizedDS3

Carrier Network

Enterprise Network

core router(built-in CSU/DSU)

DS3 DeploymentDS3 DeploymentTypically, fiber (often deployed as STS1/STS3) is used to transport the signals from the central office to the premise wiring closet where the STS1/STS3 fiber line is segmented into single or multiple DS3 coaxial lines for further deployment to individual offices or floors.

fiberCentral

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coax

Office

NetworkDevice(router)

8

Need Higher Data RateNeed Higher Data RateT1: 1.544M bpsT1: 1.544M bpsN N ×× T1 where N = 1, 2, 4, 6, 8T1 where N = 1, 2, 4, 6, 8DS3 = 28 DS3 = 28 ×× T1 = 45M bpsT1 = 45M bpsOCOC 3 ≈ 33 ≈ 3 ×× DS3 = 155M bDS3 = 155M b

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OCOC--3 ≈ 3 3 ≈ 3 ×× DS3 = 155M bpsDS3 = 155M bpsOCOC--12 = 4 12 = 4 ×× OCOC--3 = 622M bps3 = 622M bpsOCOC--48 = 4 48 = 4 ×× OCOC--12 = 2.4G bps12 = 2.4G bpsOCOC--192 = 4 192 = 4 ×× OCOC--48 = 10G bps48 = 10G bpsOCOC--768 = 4 768 = 4 ×× OCOC--192 = 40G bps 192 = 40G bps

Packet Switching ServicePacket Switching ServiceX.25X.25

Analog, packetAnalog, packet--switched LAN technology optimized for longswitched LAN technology optimized for long--distance data distance data transmissiontransmission

Frame RelayFrame RelayUpdated (and simplified) digital version of X.25 Updated (and simplified) digital version of X.25 Variable rates: from 56K bps to 1.544M bps (new standards to 45M bps)Variable rates: from 56K bps to 1.544M bps (new standards to 45M bps)

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Frame Relay OverviewFrame Relay Overview

Frame RelayRouter CSU/DSU

DCE or FrameRelay Switch

Ethernet

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Virtual circuit connectionsVirtual circuit connectionsOne physical circuitOne physical circuitMultiple virtual circuitsMultiple virtual circuits

ConnectionConnection--oriented serviceoriented servicePermanent Virtual Circuit (PVC) Permanent Virtual Circuit (PVC)

Ethernet

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Frame Relay (cont.)Frame Relay (cont.)

Address: Data Link Connection Identifier Address: Data Link Connection Identifier (DLCI), 10(DLCI), 10--bit, local significance.bit, local significance.CIR (committed information rate)CIR (committed information rate)

Guaranteed minimum amount of bandwidth Guaranteed minimum amount of bandwidth selected when leasing a frame relay circuitselected when leasing a frame relay circuit b t

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selected when leasing a frame relay circuitselected when leasing a frame relay circuitCan burst higher than CIRCan burst higher than CIRUsers get more than they pay for.Users get more than they pay for.

CIR(768k)

burst(512k)

Why Frame Relay?Why Frame Relay?(compared with T1)(compared with T1)

X.25 too much overhead, ATM too expensiveX.25 too much overhead, ATM too expensiveA popular service for WANA popular service for WAN

The paragraph in the book is incorrect. (p. 355)The paragraph in the book is incorrect. (p. 355)Switched technology: Switched technology:

not sensitive to distance in pricingnot sensitive to distance in pricing

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ot se s t ve to d sta ce p c got se s t ve to d sta ce p c gCheaper than T1 for long distanceCheaper than T1 for long distance

Physical Connection: point to multiPhysical Connection: point to multi--pointspointsSignificant cost saving for a mesh topologySignificant cost saving for a mesh topology

Logical Connection: point to pointLogical Connection: point to pointAs secured as T1 As secured as T1

Security: as good as PSTN (which is very secure)Security: as good as PSTN (which is very secure)

Digital Subscriber Lines (DSL)Digital Subscriber Lines (DSL)

Uses advanced data modulation techniques to Uses advanced data modulation techniques to achieve extraordinary throughput over regular achieve extraordinary throughput over regular phone lines (2phone lines (2--wire or 4wire or 4--wire)wire)DSL can span only limited distancesDSL can span only limited distances

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DSL can span only limited distances.DSL can span only limited distances.DSL types can be divided into two categories:DSL types can be divided into two categories:

Asymmetrical (download ≠ upload)Asymmetrical (download ≠ upload)Symmetrical (download = upload)Symmetrical (download = upload)

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Types of DSLTypes of DSL

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ADSL: Asymmetric DSLHDSL: High Bit Rate DSL (4-wire)SDSL: Symmetric (or Single line [one pair]) DSLVDSL: Very High Bit Rate DSL (not for WAN)

New standards: HDSL2 (2-wire)g.shdsl, symmetric

New: ADSL2 and ADSL2+

DSL ConnectivityDSL ConnectivityOnce inside the customer’s home or office, the DSL line must pass through a Once inside the customer’s home or office, the DSL line must pass through a DSL modemDSL modemOne RJOne RJ--11 port to PSTN11 port to PSTNOne RJOne RJ--45 port to home/office LAN45 port to home/office LAN

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ADSL ADSL ConnectivityConnectivity

Note: ADSL requires a splitter at customer premise

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DSLAM: DSL Access Multiplexer

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DSL ConnectivityDSL Connectivity(G.lite)(G.lite)

splittervoice

switch

DSLmodemrouter

core router +

localloop

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Internet

DSLAM

(ATM Switch)

filter

Note: G.lite does not need a splitter at customer premise

Cable ModemCable ModemCable connections require that the customer use a special Cable connections require that the customer use a special cable cable modemmodem, a device that transmits and receives digital signals for , a device that transmits and receives digital signals for transmission and reception via cable wiringtransmission and reception via cable wiring

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Cable Modem Network InfrastructureCable Modem Network Infrastructure

fiber

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HFC: Hybrid Fiber Coax

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Notes on Cable ModemNotes on Cable ModemShared MediumShared Medium

Performance degradation if everyone is surfing.Performance degradation if everyone is surfing.Security ConcernSecurity Concern

InfrastructureInfrastructureNot available to the business communityNot available to the business community

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Not available to the business communityNot available to the business communityComparison and Competing with xDSLComparison and Competing with xDSL

There is no right answer.There is no right answer.

Note: Any packet switching technology allow multiple users to share the media. The goal is to improve the utilization of the media. Wherever there is resource sharing, there is potential bottleneck. The question is where the media is being shared.

SONET in Metro NetworkSONET in Metro Network

Metro SONET Ring

ADMADMADMADM

Core Router

CarrierCentral

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Metro SONET Ring

Access RingAccess Ring

Access Ring

ADMADM

ADMADMADMADM

ADMADMADMADM

T1

c.f. Fig. 7-18 CPE

Office

AddAdd--Drop Multiplexer (ADM)Drop Multiplexer (ADM)

SONET Ring ADMADM

ADMADM

ADMADM

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ADMADMPass through

drop add

c.f. Fig. 7-19

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Notes on SONETNotes on SONET

SONET is a popular technology (and widely deployed) SONET is a popular technology (and widely deployed) for a carrier to build its metro backbone.for a carrier to build its metro backbone.It may also used by an enterprise in a campus network.It may also used by an enterprise in a campus network.G l b ild i S T b kbG l b ild i S T b kb

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Government also builds its own SONET backbone.Government also builds its own SONET backbone.SONET is not the technology to access the Internet. SONET is not the technology to access the Internet. An enterprise may connect its SONET to a carrier An enterprise may connect its SONET to a carrier SONET via a leased trunk (OCSONET via a leased trunk (OC--3 or higher).3 or higher).

SONET for Enterprise and SONET for Enterprise and Residential UsersResidential Users

SONET Ring(owned by carrier)

ADMADM

ADMADM

ADMADM

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ADMADM

The ADM is owned and maintained by a carrier, but it could be physically located at a company premise, or it could be at a multi-tenant environment (MTE).Example of MTE: office building, apartment complex.

Remote ConnectivityRemote ConnectivityNeed: access private resources on the corporate networkNeed: access private resources on the corporate networkRemote access methods:Remote access methods:

Direct dial to the LANDirect dial to the LANThe computer dialing into the LAN becomes a The computer dialing into the LAN becomes a remote noderemote node on the on the network (see the slide on RAS/modem pool)network (see the slide on RAS/modem pool)

Terminal Services (p. 386)Terminal Services (p. 386)

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Software running on both remote user’s computer and LAN computer Software running on both remote user’s computer and LAN computer allows remote user to “take over” the LAN workstation.allows remote user to “take over” the LAN workstation.

Web Portals (p. 387)Web Portals (p. 387)Through a browser, a user at home or on the road connects to a LAN Through a browser, a user at home or on the road connects to a LAN whose files are made visible to the Web through Web server softwarewhose files are made visible to the Web through Web server software

Virtual Private Network (VPN)Virtual Private Network (VPN)a private data network over the public Interneta private data network over the public Internet

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Virtual Private Networks (VPNs)Virtual Private Networks (VPNs)

VPN is a private network over a public network VPN is a private network over a public network (internet). A VPN may or may not be IP(internet). A VPN may or may not be IP--based.based.

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Remote AccessRemote Access

PSTN

Remote Access Server

Security Server

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InternetVPN Gateway

Intranet

Terminalserver

Review QuestionsReview QuestionsWhat are the characteristics distinguishing WAN What are the characteristics distinguishing WAN from LAN?from LAN?Speed of TSpeed of T--carrier and OCcarrier and OC--xxComparison of T1 and Frame Relay. Give a Comparison of T1 and Frame Relay. Give a scenario that you will use T1 and another scenario to scenario that you will use T1 and another scenario to use Frame Relayuse Frame Relay

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use Frame Relay.use Frame Relay.Draw a network diagram to show the T1 connection Draw a network diagram to show the T1 connection to the Internet. (CSU/DSU + router + …)to the Internet. (CSU/DSU + router + …)What is CSU/DSU? What is CSU/DSU? What is the addressing scheme of frame relay? Is What is the addressing scheme of frame relay? Is there an addressing scheme for T1?there an addressing scheme for T1?Comparison of different DSL and their speeds.Comparison of different DSL and their speeds.

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Review QuestionsReview Questions

Describe the differences between ADSL and ADSL.lite Describe the differences between ADSL and ADSL.lite (or G.lite).(or G.lite).What is the network device to distribute traffic to/from What is the network device to distribute traffic to/from SONET?SONET?

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SONET?SONET?Given a network diagram of three locations connected Given a network diagram of three locations connected via Frame Relay, design the IP subnet scheme.via Frame Relay, design the IP subnet scheme.What are the choices of remote access?What are the choices of remote access?What is VPN?What is VPN?

Midterm ExamMidterm Exam

02/05 (Tuesday), 01:30pm02/05 (Tuesday), 01:30pmExam time: 90 minutesExam time: 90 minutesExam seating will be given by the instructor.Exam seating will be given by the instructor.Exams are closed book, closed notes.Exams are closed book, closed notes.

C l l i ll d b lC l l i ll d b l

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Calculator is allowed but no palm computer.Calculator is allowed but no palm computer.You are allowed to bring a 2You are allowed to bring a 2--page note (double sides)page note (double sides)

No makeNo make--up examup examStudy Guide:Study Guide:

Review questionsReview questionsHomeworkHomework