Transcript Chapter 7 Intro WAN

Chapter 7
Wide Area Network (WAN)
Outline
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Overview
WAN Overview
Wan Connection Types
WAN Cabling
Layer 2 Encapsulation Protocols
Summary
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WAN Overview
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WANs connect remote sites.
Connection requirements vary depending on user
requirements, cost, and availability.
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Interfacing Between
WAN Service Providers
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Provider assigns connection parameters
to subscriber
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WAN Connection Types: Layer 1
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Circuit Switching
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Packet Switching
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Modem Transmission
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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)
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Time-Division Multiplexing
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WAN Encapsulation
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WAN Link Options
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WAN Data-Link Protocols
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Typical WAN Encapsulation Protocols:
Layer 2
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Analog Dialup
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ISDN
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ISDN
Router with
standard serial
interface,
connected to a
terminal adapter
Router with native
ISDN BRI U or S/T
interface or PRI
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Leased Line
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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.
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WAN with X.25
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X.25 provides a low bit rate,
shared-variable capacity that
may either be switched or
permanent
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Frame Relay
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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.
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ATM
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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.
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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
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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)
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Cable Modem
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Enhanced Cable Modems enable two-way.
High speed data transmissions using the
same coaxial lines that transmit cable
television.
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Modern WAN
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WANs Operate at the Lower Three
Levels of the OSI Model
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Comparing WAN Traffic Types
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Establishing Serial Point-toPoint Connections
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© 2004 Cisco Systems, Inc. All rights reserved.
ICND v2.2—5-35
HDLC Frame Format
• Uses a proprietary data field to support
multiprotocol environments
• Supports only single-protocol environments
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An Overview of PPP
 PPP
can carry packets from several protocol suites
using NCP.
 PPP controls the setup of several link options using LCP.
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PPP Layered Architecture
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PPP and the Data Link Layer
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PPP and the Network Layer
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PPP Operation
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Link Control Protocol Options
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PPP LCP Configuration Options
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Completing ISDN Calls
ISDN BRI and PRI
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© 2004 Cisco Systems, Inc. All rights reserved.
ICND v2.2—7-54
What Is ISDN?
• Voice, data, video, and special services
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ISDN Standards
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Standards from the ITU-T
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ISDN Access Options
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ISDN 3-Layer Model
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BRI and PRI Call Processing
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ISDN Functions and Reference Points
Functions are devices or
hardware.
 Reference points are
demarcations or interfaces.
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ISDN Functions and Reference Points
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Cisco ISDN BRI Interfaces
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Cisco ISDN PRI Interfaces
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Establishing Frame Relay
Connections
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© 2004 Cisco Systems, Inc. All rights reserved.
ICND v2.2—6-67
Frame Relay Overview
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Connections made by virtual circuits
Connection-oriented service
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Frame Relay Stack
OSI Reference Model
Frame Relay
Application
Presentation
Session
Transport
Network
IP/IPX/AppleTalk, etc.
Data-Link
Frame Relay
Physical
EIA/TIA-232,
EIA/TIA-449, V.35,
X.21, EIA/TIA-530
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Frame Relay Stack Layered Support
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Local Significance of DLCIs
The data-link connection identifier (DLCI) is stored
in the Address field of every frame transmitted.
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Frame Relay Terminology
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Data Link Control Identifier
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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
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Local Management Interface (LMI)
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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
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Selecting a Frame Relay Topology
• Frame Relay default: nonbroadcast multiaccess (NBMA)
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Frame Relay Address Mapping
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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.
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Frame Relay Signaling
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Cisco supports three LMI standards:
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Cisco
ANSI T1.617 Annex D
ITU-T Q.933 Annex A
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Frame Relay Inverse ARP
and LMI Signaling
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Stages of Inverse ARP
and LMI Operation
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Q&A
Good luck everybody.