1.
Implementing
Enterprise WAN
Links
Introducing Routing and Switching in the Enterprise –
Chapter 7
Version 4.0 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 1

2.
Objectives
 Describe the features and benefits of common WAN
connectivity options.
 Compare and configure common WAN
encapsulations.
 Describe Frame Relay
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 2

3.
Describe the Features and Benefits of
Common WAN Connectivity Options
 Serial transmissions
 Match WAN technology to type of devices required
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4.
Describe the Features and Benefits of
Common WAN Connectivity Options
 Translation device: modem
 Preparing the data: CSU/DSU
 Central Office (CO) and Customer Premises Equipment
(CPE)
 Demarc
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 4

5.
Describe the Features and Benefits of
Common WAN Connectivity Options
Physical Layer standards:
 HSSI, V.35
 Link speed:
North America:T1, T3
Europe: E1, E3
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 5

6.
Describe the Features and Benefits of
Common WAN Connectivity Options
Data link Layer standards:
 LAPF
 HDLC
 PPP
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 6

7.
Describe the Features and Benefits of
Common WAN Connectivity Options
 Modems enable POTS to be used for WAN connections
 Analog signals modulate a carrier wave in the speech band
 The modulated carrier wave carries information to destination
across the telephone network
 Destination demodulates the carrier and extracts information
 Modems are also used for DSL and cable connections to ISP
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 7

8.
Describe the Features and Benefits of
Common WAN Connectivity Options
 DSO channel = time slice
 Fractional connections
 Time Division Multiplexing (TDM)
 Statistical Time Division Multiplexing (STDM)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 8

9.
Describe the Features and Benefits of
Common WAN Connectivity Options
 Circuit switching:
Dedicated bandwidth
Higher cost
Higher level of security
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 9

10.
Describe the Features and Benefits of
Common WAN Connectivity Options
 Packet switching:
Bandwidth efficiency
Identifier on each packet
Preconfigured, but non-exclusive, link
 Cell switching: high-speed packet switching
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 10

11.
Describe the Features and Benefits of
Common WAN Connectivity Options
 Virtual circuits
Switched virtual circuits
Permanent virtual circuits
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 11

12.
Describe the Features and Benefits of
Common WAN Connectivity Options
 Last mile and long range WAN technologies
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 12

13.
Compare and Configure Common WAN
Encapsulations
 Elements of Layer 2 encapsulations
Flag
Address
Control
Protocol
Data
FCS
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 13

14.
Compare and Configure Common WAN
Encapsulations
 Standard bit-oriented Layer 2 encapsulation: HDLC
 Cisco HDLC: additional Type field
Default WAN encapsulation on Cisco devices
Allows multiple Network Layer protocols to share a link
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 14

15.
Compare and Configure Common WAN
Encapsulations
Point-to-Point Protocol) PPP:
 Multi-protocol datagrams
 Sub-protocols: LCP, NCP
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 15

16.
Compare and Configure Common WAN
Encapsulations
 Link Control Protocol options:
authentication
compression
error detection
multilink
PPP callback
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 16

17.
Compare and Configure Common WAN
Encapsulations
 Phases of PPP sessions:
Link-establishment
Authentication (optional)
NCP negotiation
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 17

18.
Compare and Configure Common WAN
Encapsulations
 Change encapsulation from HDLC to PPP on both ends
of link
 Configure desired optional features
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 18

19.
Compare and Configure Common WAN
Encapsulations
Verification and troubleshooting commands:
 show interfaces serial
 show controllers
 debug serial interface
 debug ppp
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 19

20.
Compare and Configure Common WAN
Encapsulations
 Password Authentication Protocol (PAP)
 Challenge Handshake Authentication Protocol (CHAP)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 20

21.
Describe Frame Relay
 Nonbroadcast multiaccess network
 Packet switching with variable length packets
 STDM
 Virtual circuit between two DTE devices
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22.
Describe Frame Relay
 Data link connection identifier (DLCI)
 Inverse ARP
 LMI
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23.
Describe Frame Relay
Service parameters:
 Committed information rate (CIR)
 Excess information rate (EIR)
 Discard eligible (DE) frames
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24.
Describe Frame Relay
Traffic management:
 Forward explicit congestion notification (FECN)
 Backward explicit congestion notification (BECN)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 24

25.
Summary
 Circuit switching WAN technologies create a physical
circuit between end devices before sending data
 Packet and cell switching WAN technologies use virtual
circuits to send data across the network
 Layer 2 encapsulation changes as frames move across
a WAN
 PPP permits many advanced features including
authentication, compression, and load balancing
 Frame Relay is a packet switched technology using
switched or permanent virtual circuits
 Frame Relay uses parameters such as CIR to establish
the bandwidth used on each VC
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 25

26.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 26