ccna routing and switching lesson 05 - wans - eric vanderburg

Networking Essentials – Eric Vanderburg © 2005

WANsWANsChapter 5Chapter 5


DSLDSL DSL is layer 1DSL is layer 1 ATM can be used on top of DSLATM can be used on top of DSL PPPoEPPPoE

CHAP authenticationCHAP authentication IP address assignmentIP address assignment

DSLAM (DSL Access Multiplexer)DSLAM (DSL Access Multiplexer) Connection at ISP for DSL. Separates Connection at ISP for DSL. Separates

voice from data. voice from data. Data is sent over the ISP’s data Data is sent over the ISP’s data

network rather than the PSTN. network rather than the PSTN.


Cable ModemCable Modem Datalink protocol is MCNS Datalink protocol is MCNS

(Multimedia Cable Network (Multimedia Cable Network Systems) – Identifies each modem Systems) – Identifies each modem so shared data is only processed by so shared data is only processed by the designated modem. the designated modem.

Different channels are used for Different channels are used for upstream & downstream data. upstream & downstream data.


Cable ModemCable Modem Downstream dataDownstream data

QAM (Quadrature Amplitude QAM (Quadrature Amplitude Modulation)Modulation) QAM 64 & QAM 256QAM 64 & QAM 256

Upstream dataUpstream data QPSK (Quaternary Phase Shift Keying)QPSK (Quaternary Phase Shift Keying) QAM 16QAM 16 Same frequency range as other uses Same frequency range as other uses

(can collide)(can collide)


DCE & DTEDCE & DTE CSU/DSU is considered DCE (Data CSU/DSU is considered DCE (Data

Communications Equipment) Communications Equipment) because it does clockingbecause it does clocking

Router is considered DTE (Data Router is considered DTE (Data Terminal Equipment)Terminal Equipment)

Connecting 2 routers directlyConnecting 2 routers directly Use DTE to DCE cableUse DTE to DCE cable One router must have clocking One router must have clocking

configuredconfigured


HDLC (High level Data Link HDLC (High level Data Link Control)Control)

Cisco uses a proprietary version Cisco uses a proprietary version with a type field in the header. with a type field in the header.

Default for Serial portsDefault for Serial ports FCS in trailer. Error frames are FCS in trailer. Error frames are

discardeddiscarded Synchronous, sends receiver ready Synchronous, sends receiver ready

frames when there is no data to frames when there is no data to synch the line (keep timing for 1’s synch the line (keep timing for 1’s & 0’s)& 0’s)


PPP (Point to Point PPP (Point to Point Protocol)Protocol)

FCS in trailerFCS in trailer Type fieldType field LCP (Link Control Protocol) - used with LCP (Link Control Protocol) - used with

dialed links to bring the connection updialed links to bring the connection up IPCP (IP Control Protocol) allows IP IPCP (IP Control Protocol) allows IP

addresses to be assigned over PPPaddresses to be assigned over PPP PPP Callback - incoming connections PPP Callback - incoming connections

are disconnected & called back to are disconnected & called back to verify number and stop roaming or verify number and stop roaming or unauthorized accessunauthorized access


PPP (Point to Point PPP (Point to Point Protocol)Protocol)

Magic Number looped link detectionMagic Number looped link detection Supports multilinkSupports multilink PAP & CHAP supportPAP & CHAP support Synchronous or Asynchronous (used Synchronous or Asynchronous (used

mainly for dial-up)mainly for dial-up) LQM (Link Quality Monitoring) – takes LQM (Link Quality Monitoring) – takes

down links with too many errorsdown links with too many errors Supports compression but tasks Supports compression but tasks

router processorrouter processor


ISDNISDN B & D channelsB & D channels LAPD (Link Access Procedure D channel) LAPD (Link Access Procedure D channel)

used to set up and bring down circuits. used to set up and bring down circuits. Q.931 specifies the setup & teardown Q.931 specifies the setup & teardown

messagesmessages Circuit switching. Can connect to many Circuit switching. Can connect to many

sites but circuits are set up by dialing. sites but circuits are set up by dialing. SPID (Service Profile Identifier) – SPID (Service Profile Identifier) –

provided by the ISP for authenticating B provided by the ISP for authenticating B channels. channels.


ISDNISDN B channels are digital so an analog line is B channels are digital so an analog line is

used for the DTMF (Dual Tone Multi-used for the DTMF (Dual Tone Multi-frequency) tones frequency) tones

BRI for residential use (2B+D), D channel BRI for residential use (2B+D), D channel 16k16k

PRI for business use, D channel 64kPRI for business use, D channel 64k T1 (23B+D), uses AMI (Alternate Mark T1 (23B+D), uses AMI (Alternate Mark

Inversion) or B8ZS (Binary 8 with Zero Inversion) or B8ZS (Binary 8 with Zero Substitution) encodingSubstitution) encoding

E1 (30B+D), uses HDB3 (High Density E1 (30B+D), uses HDB3 (High Density Bipolar 3) encodingBipolar 3) encoding


ISDN DDRISDN DDR DDR (Dial on Demand Routing) dials DDR (Dial on Demand Routing) dials

a link if traffic is waiting to go to a a link if traffic is waiting to go to a site that is not currently connectedsite that is not currently connected Interesting & boring traffic (interesting Interesting & boring traffic (interesting

traffic “triggers the dial”)traffic “triggers the dial”) Dial mapping - DDR needs to be Dial mapping - DDR needs to be

configured with the networks on each configured with the networks on each link (static route) & their phone numberslink (static route) & their phone numbers

Idle timeouts allow unused connections Idle timeouts allow unused connections to be taken down. to be taken down.


Frame RelayFrame Relay Frame switching serviceFrame switching service Leased lines from router to FR switchLeased lines from router to FR switch Layer 2 address – DLCI (Datalink Layer 2 address – DLCI (Datalink

connection Identifier), only a place connection Identifier), only a place for one DLCI number in FR frames. for one DLCI number in FR frames. Changed by switches at destination. Changed by switches at destination.

Encapsulation type must be same Encapsulation type must be same between routers (Cisco & IETF). Use between routers (Cisco & IETF). Use IETF if both routers are not Cisco. IETF if both routers are not Cisco.


Frame RelayFrame Relay PVC (Permanent Virtual Circuit) – PVC (Permanent Virtual Circuit) –

link between 2 devices on a FR link between 2 devices on a FR network. PVCs are set up between network. PVCs are set up between the devices you own on the FR the devices you own on the FR network. (Set up by provider)network. (Set up by provider)

CIR (Committed Information Rate) – CIR (Committed Information Rate) – minimum bandwidth specifiedminimum bandwidth specified


Frame RelayFrame Relay LMI (Local Management Interface) – used LMI (Local Management Interface) – used

for messages sent between router & for messages sent between router & switch. Encoding type must be sameswitch. Encoding type must be same Sends keepalive messagesSends keepalive messages Status messages can be used to find DLCI Status messages can be used to find DLCI

numbers of other routersnumbers of other routers Cisco LMI uses DLCI 1023Cisco LMI uses DLCI 1023 ANSI T1.617-D & ITU Q.933-A LMI’s use DLCI 0ANSI T1.617-D & ITU Q.933-A LMI’s use DLCI 0 LMI autosenseLMI autosense Inverse ARP maps IP addresses to DLCI Inverse ARP maps IP addresses to DLCI

numbers. Routers send their IP addressnumbers. Routers send their IP address


ATMATM Layer 2 protocol using fixed length Layer 2 protocol using fixed length

cellscells Usually runs on top of SONET, Usually runs on top of SONET,

sometimes DSLsometimes DSL VPI (Virtual Path Identifier) & VCI VPI (Virtual Path Identifier) & VCI

(Virtual Channel Identifier) – used to (Virtual Channel Identifier) – used to switch cellsswitch cells


X.25X.25 Operates on layers 2 & 3Operates on layers 2 & 3 Reliable with high overheadReliable with high overhead Used in many foreign countriesUsed in many foreign countries

ccna routing and switching lesson 05 - wans - eric vanderburg

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