Chapter 1: Introduction to WANs
CCNA Exploration 4.0
2
Objectives
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Describe how the Cisco enterprise architecture provides
integrated services over an enterprise network.
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Describe key WAN technology concepts.
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Select the appropriate WAN technology to meet different
enterprise business requirements.
3
Providing Integrated Services
to the Enterprise
4
Introducing Wide Area Networks
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WAN is a data communications network that operates
beyond the geographic scope of a LAN.
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An enterprise must subscribe to a WAN service provider to
use WAN carrier network services.
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WANs generally carry a variety of traffic types, such as
voice, data, and video.
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Introducing Wide Area Networks
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Three major characteristics of WANs:
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As companies grow, they hire more employees, open branch
offices, and expand into global markets.
Small Office (Single LAN)
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The Evolving Enterprise
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Campus (Multiple LANs)
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Branch (WAN)
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The Evolving Enterprise
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Distributed (Global)
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The Evolving Network Model
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Hierarchical Design Model
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Access layer
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Distribution layer
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Core layer (backbone)
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The Evolving Network Model
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The Hierarchical Network Model provides a modular framework
that allows flexibility in network design, and facilitates ease of
implementation and troubleshooting in the infrastructure.

internal users.
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The Enterprise Architecture Modules
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Enterprise Edge: Aggregates the connectivity from the
various functional areas at the enterprise edge and routes
the traffic into the campus core submodule:
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E-Commerce
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Internet Connectivity
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WAN and MAN Site-to-site VPN
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Remote Access and VPN
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WAN and Internet: Service Provider Environment
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Enterprise Branch: Extends the applications and services
found at the campus to remote locations
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Enterprise Data Center: Manages and maintains centralized
data systems for the entire enterprise.
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Enterprise Teleworker: Connects individual employees to
network resource remotely, typically from their homes.
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The Enterprise Architecture Modules
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Activity: 1.1.3.4

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V.35 -The ITU-T standard for synchronous communications between a
network access device and a packet network. Originally specified to
support data rates of 48 kb/s, it now supports speeds of up to 2.048 Mb/s
using a 34-pin rectangular connector.
•
X.21 -An ITU-T standard for synchronous digital communications. It uses
a 15-pin D-connector.
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WAN Data Link Layer Concepts
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WANs require data link layer protocols to establish the link
across the communication line from the sending to the
receiving device.
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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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The most common WAN data-link protocols are:
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HDLC
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PPP
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Frame Relay
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ATM
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ISDN and X.25 are older data-link protocols that are less