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

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 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 3 Describe the Features and Benefits of Common WAN Connectivity Options  Serial transmissions  Match WAN technology to type of devices required

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 21 Describe Frame Relay  Nonbroadcast multiaccess network  Packet switching with variable length packets  STDM  Virtual circuit between two DTE devices

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 22 Describe Frame Relay  Data link connection identifier (DLCI)  Inverse ARP  LMI

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 23 Describe Frame Relay Service parameters:  Committed information rate (CIR)  Excess information rate (EIR)  Discard eligible (DE) frames

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