Objectives
ƒ Describe how the Cisco Enterprise Composite
Model (ECNM) provides integrated services
over an Enterprise network.
Services in a Converged
WAN
ƒ Describe the key WAN technology concepts.
ƒ Identify the appropriate WAN technologies to
use when matching ECNM best practices with
typical enterprise requirements for WAN
communications.
Accessing the WAN – Chapter 1
2
ITE I Chapter 6
© 2006 Cisco Systems, Inc. All rights reserved.
Cisco Public
1
The Hierarchical Network Model
What is a WAN?
ƒ Access layer
Grants user access to network devices.
Provide teleworkers or remote sites access to the
corporate network across WAN technology.
ƒ Distribution layer
Aggregates the wiring closets
Aggregates WAN connections at the edge of the
campus
ƒ Core layer
A high-speed backbone
A network that operates beyond the geographic scope of a LAN.
3
4
ECNM Provides Integrated Services over an
Enterprise Network
The Hierarchical Network Model
5
6
1
7
Key WAN Technology Concepts
8
WAN Physical Layer Terminology
ƒ WAN operations focus primarily on Layer 1 and Layer 2
9
WAN Devices
10
WAN Data Link Layer Protocols
11
12
2
WAN Frame Encapsulation Formats
Switching Technologies: Circuit Switching
ƒ Flag – e.g. 8-bit pattern 01111110
ƒ Dialup services - establishes a dedicated circuit between
terminals before the users may communicate.
ƒ Address field is not needed for WAN links, which are almost
always point-to-point.
ƒ Time division multiplexing (TDM) gives each conversation a
share of the connection in turn.
ƒ Control - content of the data is control information or
network layer data
ƒ Protocol – indicates the network layer protocol
13
Switching
SwitchingTechnologies:
TechnologiesPacket Switching
ƒ PSTN and ISDN are circuit-switching technologies that may
be used to implement a WAN in an enterprise setting.
14
WAN Link Connection Options
ƒ Splits data into packets that are routed over shared links
ƒ Two approaches:
Connectionless, e.g. the Internet
Connection-oriented
- Permanent virtual circuits (PVCs) , e.g. Frame relay
- Switched virtual circuits (SVCs)
15
Leased Line Types and Bandwidths
16
Integrated Services Digital Network (ISDN)
ƒ Basic Rate Interface (BRI) (Backup for leased line)
17
ƒ Primary Rate Interface (PRI)
18
3
Internet Connection Options
Packet Switching Technologies
ƒ Broadband Services - connect telecommuting employees to
a corporate site over the Internet.
DSL and Cable Modem
Broadband Wireless
WiMAX – range 10 miles.
Satellite Internet
ƒ X.25, Frame Relay,
ATM
ƒ VPN Technology
encrypted connection between private networks over
public networks such as the Internet.
ƒ For point-to-multipoint,
cheaper than using
multiple leased lines
a VPN uses virtual connections called VPN tunnels,
ƒ Metro Ethernet - broadens Ethernet to MANs
19
Choosing a WAN Service
Option
Lease line
Circuit
switching
Packet
switching
Cell relay
Internet
Desc.
P2P
dedicated
connection
For
Most secure
Against
Expensive
20
Summary
Services
PPP, HDLC
ƒ A WAN is defined as
A data communications network that operates
beyond the geographic scope of a LAN
Dedicated
circuit
between endpoints
Transmission Least
over PVCs or expensive
SVCs
Call setup
PSTN, ISDN
Uses fixed
length cells
Public
network
High b/w
Expensive
Least
expensive
Least secure, VPN, DSL,
variable b/w
Cable,
Wireless
ƒ WAN primarily operate on layer 1 & 2 of the OSI model
ƒ WAN technologies include
–Leased line
Shared
Frame relay,
media across X.25
link
–ISDN
–Frame relay
ATM
–X.25
–ATM
21
22
Summary
ƒ Cisco Enterprise Architecture
–This is an expansion of the hierarchical model that
further divides the enterprise network into
•Physical areas
•Logical areas
•Functional areas
ƒ 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
23
4