Accessing the WAN – Chapter 1
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Objectives
 Describe how the Cisco Enterprise Composite
Model (ECNM) provides integrated services over an Enterprise network.
 Describe the key WAN technology concepts.
 Identify the appropriate WAN technologies to use when matching ECNM best practices with typical enterprise requirements for WAN communications.
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Wide Area Networks
WAN
LAN connects computers, peripherals, and other devices in a single building or other small geographic area
An enterprise must subscribe to a WAN service provider to use WAN carrier network services.
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A WAN is a data communications network that operates beyond the geographic scope of a LAN.
WAN allows the transmission of data across greater geographic distances
WANs use facilities provided by a service provider, or carrier.
WANs use serial connections.
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WAN’s – The need
 Sharing of data
 Organization to organization
 Remote users
 Over large distance
 LAN – Falls short
 Company Growth
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Evolving Enterprise
 Stages of business growth.
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The Evolving Network Model
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Describe How ECNM Provides Integrated
Services over an Enterprise Network
 Problems with the Hierarchical Design Model that Cisco's
Enterprise Composite Model has been designed to address
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Describe How ECNM Provides Integrated
Services over an Enterprise Network
 Explain the purpose of Cisco Enterprise Architectures
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Key WAN Technology Concepts
 WAN functions in terms of the OSI Reference Model
The physical layer (OSI Layer 1) protocols describe how to provide electrical, mechanical, operational, and functional connections to the services of a communications service provider.
The data link layer (OSI Layer 2) protocols define how data is encapsulated for transmission toward a remote location and the mechanisms for transferring the resulting frames. A variety of different technologies are used, such as Frame Relay and ATM. Some of these protocols use the same basic framing mechanism,
High-Level Data Link Control (HDLC), an ISO standard, or one of its subsets or variants.
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Key WAN Technology Concepts
 WAN physical layer concepts for network and Internet communications
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Key WAN Technology Concepts
•WAN physical-layer protocols describe how to provide electrical, mechanical, operational, and functional connections for WAN services.
• The WAN physical layer also describes the interface between the DTE and the DCE.
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Key WAN Technology Concepts
 WAN data link layer protocols used in today’s
Enterprise WAN networks
ATM uses small fixed-size cells of 53 bytes (48 bytes for data),
Data link layer protocols define how data is encapsulated for transmission to remote sites and the mechanisms for transferring the resulting frames.
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Key WAN Technology Concepts
 Switching technologies used for WANs in an Enterprise setting
A circuit-switched network is one that establishes a dedicated circuit (or channel) between nodes and terminals before the users may communicate.
Packet switching splits traffic data into packets that are routed over a shared network. Packetswitching networks do not require a circuit to be established, and they allow many pairs of nodes to communicate over the same channel. Packets are divided and sent through available connections.
PSTN and ISDN are two types of circuitswitching technology that may be used to implement a WAN in an enterprise setting.
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There are two approaches to this link determination, connectionless or connectionoriented.
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Select the Appropriate WAN Technology to meet
ECNM Requirements
 List the various options for connecting subscribers to the WAN
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Select the Appropriate WAN Technology to meet
ECNM Requirements
 Enterprises use leased line services to provide a WAN connection
Point-to-point lines are usually leased from a carrier and are called leased lines.
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Select the Appropriate WAN Technology to meet
ECNM Requirements
 Circuit switching options available to provide a WAN connection
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Select the Appropriate WAN Technology to meet
ECNM Requirements
 Packet switching options available to provide a WAN connection
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Select the Appropriate WAN Technology to meet
ECNM Requirements
 List factors to consider when selecting a WAN connection
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Summary
 A WAN is defined as
A data communications network that operates beyond the geographic scope of a LAN
 WAN primarily operate on layer 1 & 2 of the OSI model
 WAN technologies include
–Leased line
–ISDN
–Frame relay
–X.25
–ATM
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Summary
 Cisco Enterprise Architecture
–This is an expansion of the hierarchical model that further divides the enterprise network into
•Physical areas
•Logical areas
•Functional areas
 Selecting the appropriate WAN technology requires considering some of the following:
–WAN’s purpose
–Geographic scope of WAN
–Traffic requirements
–If WAN uses a public or private infrastructure
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