Chapter 7 Wide Area Network (WAN)

Introducing Wide-Area Networks (Part I)

3 Outline  Overview  WAN Overview  Wan Connection Types  WAN Cabling  Layer 2 Encapsulation Protocols  Summary

4 WAN Overview WANs connect remote sites. Connection requirements vary depending on user requirements, cost, and availability.

5 Provider assigns connection parameters to subscriber Interfacing Between WAN Service Providers

6 WAN Connection Types: Layer 1

7 Circuit Switching

8 Packet Switching

9 Serial Point-to-Point Connections

10 WAN Line Types and Bandwidth Mbps

11 Modem Transmission

12 Introduction to Serial Communication Transmission system encodes bits into electrical voltage using methods like NRZ-L or AMI Some of the many serial communications standards include the following: RS-232-E V.35 High-Speed Serial Interface (HSSI)

13 Time-Division Multiplexing

14 DTE-DCE

15 WAN Encapsulation

16 WAN Link Options

17 WAN Link Options

18 WAN Data-Link Protocols

19 Typical WAN Encapsulation Protocols: Layer 2

20 Analog Dialup

21 ISDN

22 ISDN Router with standard serial interface, connected to a terminal adapter Router with native ISDN BRI U or S/T interface or PRI

23 Leased Line Leased lines are not only used to provide direct point-to-point connections between Enterprise LANS, they can also be used to connect individual branches to a packet switched network.

24 WAN with X.25 X.25 provides a low bit rate, shared-variable capacity that may either be switched or permanent

25 Frame Relay Most Frame Relay connections are based on PVCs rather than SVCs. It implements no error or flow control. This leads to reduced latency. Frame Relay provides permanent shared medium bandwidth connectivity that carries both voice and data traffic.

26 ATM Asynchronous Transfer Mode (ATM) is a technology capable of transferring voice, video, and data through private and public networks. It is built on a cell based architecture rather than on a frame-based architecture.

27 DSL DSL uses existing twisted-pair telephone lines to transport high-bandwidth data DSL service is considered broadband, as it uses multiple frequencies within the same physical medium to transmit data

28 ADSL Technology Splitter The local loop connects the splitter to the DSLAM DSLAM connected to ISP using ATM technology Voice and data use separate frequency ranges (voice 0-4Khz, data 20Khx – 1Mhz)

29 Cable Modem Enhanced Cable Modems enable two-way. High speed data transmissions using the same coaxial lines that transmit cable television.

30 Modern WAN

31 WANs Operate at the Lower Three Levels of the OSI Model

32 Comparing WAN Traffic Types

33 Summary  A WAN makes data connections across a broad geographic area so that information can be exchanged between distant sites.  WAN connection types include leased line, circuit-switched, and packet-switched.  WAN components that the provider assigns to your organization include CPE, demarcation, local loop, CO switch, and toll network.  Cisco routers support the EIA/TIA-232, EIA/TIA-449, V.35, X.21, and EIA/TIA-530 standards for serial connections.  To encapsulate data for crossing a WAN link, a variety of Layer 2 protocols can be used, including HDLC, PPP, SLIP, X.25/LAPB, Frame Relay, and ATM.

Q & A 34

35 © 2004 Cisco Systems, Inc. All rights reserved. ICND v2.2—5-35 Establishing Serial Point-to- Point Connections

36 Outline  Overview  HDLC Encapsulation Configuration  PPP Layered Architecture  PPP Configuration  PPP Session Establishment  PPP Authentication Protocols  Summary

37 Demarcation Point The point in the network where the responsibility of the service provider or "telco" ends.

38 Supports only single-protocol environments HDLC Frame Format Uses a proprietary data field to support multiprotocol environments

39 PPP can carry packets from several protocol suites using NCP. PPP controls the setup of several link options using LCP. An Overview of PPP

40 PPP Layered Architecture

41 PPP and the Data Link Layer

42 PPP and the Network Layer

43 PPP Operation

44 Link Control Protocol Options

45 PPP LCP Configuration Options

46 PPP Session Establishment Two PPP authentication protocols: PAP and CHAP

47 Password Authentication Protocol (PAP)

48 Challenge Handshake Authentication Protocol (CHAP) CHAP provides protection against playback attack through the use of a variable challenge value that is unique and unpredictable.

49 CHAP Authentication Process

50 Summary  The encapsulation hdlc interface configuration command can be used to specify HDLC encapsulation on the interface.  PPP’s lower-level functions use synchronous and asynchronous physical media and ISDN. PPP’s higher-level functions carry packets from several network layer protocols using its NCPs.  Configurable aspects of PPP include methods of authentication, compression, and error detection and whether multilink is supported.  PPP session establishment progresses through three phases: link establishment, authentication, and network layer protocol.

51 Summary (Cont.)  When configuring PPP authentication, you can select PAP or CHAP. CHAP provides protection from playback and repeated trial-and-error attacks.

Part II

53 WAN Link Options

54 © 2004 Cisco Systems, Inc. All rights reserved. ICND v2.2—7-54 Completing ISDN Calls ISDN BRI and PRI

55 Outline  Overview  ISDN Overview  ISDN Standards  ISDN Access Methods  ISDN BRI or PRI Call Establishment  ISDN Functions and Reference Points  Router ISDN Interface Determination  ISDN Switch Types  ISDN BRI Configuration  ISDN PRI Configuration  ISDN Configuration Verification  ISDN Configuration Troubleshooting  Summary

56 What Is ISDN? Voice, data, video, and special services

57  Standards from the ITU-T ISDN Standards

58 ISDN Access Options

59 ISDN 3-Layer Model

60 BRI and PRI Call Processing

61 ISDN Functions and Reference Points Functions are devices or hardware. Reference points are demarcations or interfaces.

62 ISDN Functions and Reference Points

63 Cisco ISDN BRI Interfaces

64 Cisco ISDN PRI Interfaces

65 Summary  ISDN defines a digital architecture that provides integrated voice and data capability through the public switched network.  ISDN specifies three standard protocols: E-series, I-series, and Q-series.  ISDN specifies two standard access methods, BRI and PRI.  To establish an ISDN call, the D channel is used between the routers and the switches. SS7 signaling is used between the switches.  ISDN functions are hardware devices, whereas reference points are interfaces between devices.  Cisco devices can be physically configured with different ISDN options, which dictate what additional equipment, if any, is needed to run ISDN.

66 Summary (Cont.)  You must configure your router to identify the type of switch it will be communicating with, and the type of switch depends in part on the country in which the switch is located.  The isdn switch-type and isdn spid commands can be used to enable ISDN BRI.  The pri-group command can be used to enable ISDN PRI.  The show commands can be used to verify that your ISDN configuration is functioning properly.  The debug commands can be used to troubleshoot your ISDN configuration.

67 © 2004 Cisco Systems, Inc. All rights reserved. ICND v2.2—6-67 Establishing Frame Relay Connections

68 Outline  Overview  Frame Relay Overview  Frame Relay Stack Layered Support  Frame Relay Terminology  Frame Relay Topologies  Reachability Issues in Frame Relay  Reachability Issue Resolution  Frame Relay Address Mapping  Frame Relay Signaling  How service Providers Map Frame Relay DLCIs  Service Provider Frame Relay-to-ATM Interworking  Summary

69 Frame Relay Overview  Connections made by virtual circuits  Connection-oriented service

70 Frame Relay Stack OSI Reference Model Frame Relay Physical Presentation Session Transport Network Data-Link Application EIA/TIA-232, EIA/TIA-449, V.35, X.21, EIA/TIA-530 Frame Relay IP/IPX/AppleTalk, etc.

71 Frame Relay Stack Layered Support

72 Local Significance of DLCIs The data-link connection identifier (DLCI) is stored in the Address field of every frame transmitted.

73 Frame Relay Terminology

74 Data Link Control Identifier The 10-bit DLCI associates the frame with its virtual circuit It is of local significance only - a frame will not generally be delivered with the same DLCI with which it started Some DLCI’s are reserved

75 Local Management Interface (LMI) Three types of LMIs are supported by Cisco routers:  Cisco — The original LMI extensions  Ansi — Corresponding to the ANSI standard T1.617 Annex D  q933a — Corresponding to the ITU standard Q933 Annex A

76 Frame Relay default: nonbroadcast multiaccess (NBMA) Selecting a Frame Relay Topology

77 Reachability Issues with Routing Updates Problem:  Broadcast traffic must be replicated for each active connection.  Split-horizon rule prevents routing updates received on an interface from being forwarded out the same interface.

78 Resolving Reachability Issues Split horizon can cause problems in NBMA environments. Subinterfaces can resolve split-horizon issues. Solution: A single physical interface simulates multiple logical interfaces.

79 Frame Relay Address Mapping  Use LMI to get locally significant DLCI from the Frame Relay switch.  Use Inverse ARP to map the local DLCI to the remote router network layer address.

80 Frame Relay Signaling  Cisco supports three LMI standards: Cisco ANSI T1.617 Annex D ITU-T Q.933 Annex A

81 Frame Relay Inverse ARP and LMI Signaling

82 Stages of Inverse ARP and LMI Operation

83 How Service Providers Map Frame Relay DLCIs: Service Provider View

84 How Service Providers Map Frame Relay DLCIs: Enterprise View

85 Service Provider Frame Relay-to-ATM Internetworking

86 Summary  Frame Relay is a connection-oriented data-link technology that is streamlined to provide high performance and efficiency.  The core aspects of Frame Relay function at the lower two layers of the OSI reference model.  Knowing the terms that are used frequently when discussing Frame Relay is important to understanding the operation and configuration of Frame Relay services.  Frame Relay allows you to interconnect your remote sites in a variety of topologies including star, full mesh, and partial mesh.  Two problems that Frame Relay NBMA topology may cause include reachability issues regarding routing updates and the need to replicate broadcasts onto each PVC when a physical interface contains more than one PVC.  Two methods to resolve the reachability issue brought on by split horizon are turning off split horizon and using a fully meshed topology.

87 Summary (Cont.)  A Frame Relay connection requires that on a VC, the local DLCI be mapped to a destination network layer address, such as an IP address.  Cisco routers try to autosense which LMI type the Frame Relay switch is using by sending one or more full LMI status requests to the Frame Relay switch. The Frame Relay switch responds with one or more LMI types, and the router configures itself with the last LMI type received.  Service providers map Frame Relay DLCIs so that DLCIs with local significance appear at each end of a Frame Relay connection.  FRF.5 provides internetworking functionality that allows Frame Relay end users to communicate over an intermediate ATM network that supports FRF.5. FRF.8 provides service internetworking functionality that allows a Frame Relay end user to communicate with an ATM end user.

Q&A Good luck everybody.