Transcript Wide Area Network

Chapter 15
Wide Area Network
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Chapter Objectives
At the end of this Chapter you will be able to:
Describe different methods for connecting to a WAN
Configure and verify a basic WAN serial connection
Describe VPN technology (including: importance, benefits, role,
impact, components)
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Introduction to Wide Area Networks

Typically, LAN connections are within a company and WAN connections
allow you to connect to remote sites. Typically, you don’t own the
infrastructure for WAN connections—another company, such as a telephone
company, provides the infrastructure.

WAN connections are usually slower than LAN connections.

One of the major factors when choosing a WAN or MAN provider is cost.
These connections are billed in multiple ways: flat monthly lease cost,
per-packet cost, per-minute cost, and many other methods.
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Equipment and Components
Equipments and Components of a WAN
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Defining WAN Terms

Customer premises equipment (CPE)
Customer premises equipment (CPE) is equipment that’s owned by the
subscriber and located on the subscriber’s premises.

Demarcation point

The demarcation point is the precise spot where the service provider’s
responsibility ends and the CPE begins. It’s generally a device in a
telecommunications closet owned and installed by the
telecommunications company (telco). It’s your responsibility to cable
(extended demarc) from this box to the CPE, which is usually a connection
to a CSU/DSU or ISDN interface.
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
Local loop
The local loop connects the demarc to the closest switching office, which
is called a central office.

Central office (CO)
This point connects the customer’s network to the provider’s switching
network. Good to know is that a central office (CO) is sometimes referred
to as a point of presence (POP)

Toll network
The toll network is a trunk line inside a WAN provider’s network. This
network is a collection of switches and facilities owned by the ISP.
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WAN Connection Types
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Different type of WAN Connections
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
Leased Lines
These are usually referred to as a point-to-point or dedicated connection.
A leased line is a pre-established WAN communications path that goes
from the CPE through the DCE switch, then over to the CPE of the remote
site. The CPE enables DTE networks to communicate at any time with no
cumbersome setup procedures to muddle through before transmitting
data. When you’ve got plenty of cash, this is really the way to go because
it uses synchronous serial lines up to 45Mbps.
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
Circuit Switching
When you hear the term circuit switching, think phone call. The big
advantage is cost—you only pay for the time you actually use. No data can
transfer before an end-to-end connection is established. Circuit switching
uses dial-up modems or ISDN and is used for low-bandwidth data transfers.

Packet Switching
This is a WAN switching method that allows you to share bandwidth with
other companies to save money.
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Introduction to WAN Protocols
most prominently known WAN protocols used today: Frame Relay, ISDN,
LAPB, LAPD, HDLC, PPP, PPPoE, Cable, DSL, MPLS, and ATM.

Frame Relay

A packet-switched technology that made its debut in the early 1990s,
Frame Relay is a high-performance Data Link and Physical layer
specification.

Another Frame Relay benefit is that it provides features for dynamic
bandwidth allocation and congestion control.
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
ISDN
Integrated Services Digital Network (ISDN) is a set of digital services that
transmit voice and data over existing phone lines. ISDN offers a cost
effective solution for remote users
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LAPB
Link Access Procedure, Balanced (LAPB) was created to be a connectionoriented protocol at the Data Link layer for use with X.25, but it can also
be used as a simple data link transport.

LAPD
Link Access Procedure, D-Channel (LAPD) is used with ISDN at the Data
Link layer (layer 2) as a protocol for the D (signaling) channel.
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
HDLC
High-Level Data-Link Control (HDLC) was derived from Synchronous Data
Link Control (SDLC), which was created by IBM as a Data Link connection
protocol. HDLC works at the Data Link layer and creates very little overhead
compared to LAPB.

PPP
Point-to-Point Protocol (PPP) uses a Network Control Protocol field in the
Data Link header to identify the Network layer protocol and allows
authentication and multilink connections to be run over asynchronous and
synchronous links.
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
PPPoE
Point-to-Point Protocol over Ethernet encapsulates PPP frames in Ethernet
frames and is usually used in conjunction with ADSL services. It gives you a
lot of the familiar PPP features like authentication, encryption, and
compression.

Cable
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DSL
Digital subscriber line is a technology used by traditional telephone
companies to deliver advanced services (high-speed data and sometimes
video) over twisted-pair copper telephone wires.
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
MPLS
MultiProtocol Label Switching (MPLS) is a data-carrying mechanism that
emulates some properties of a circuit-switched network over a packetswitched network. MPLS is a switching mechanism that imposes labels
(numbers) to packets and then uses those labels to forward packets.

ATM
Asynchronous Transfer Mode (ATM) was created for time-sensitive traffic,
providing simultaneous transmission of voice, video, and data. ATM uses
cells that are a fixed 53 bytes long instead of packets.
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Data Terminal Equipment and Data Communication
Equipment

By default, router interfaces are data terminal equipment (DTE), and they
connect into data communication equipment (DCE) like a channel service
unit/data service unit (CSU/DSU).

The CSU/DSU then plugs into a demarcation location (demarc) and is the
service provider’s last responsibility. Most of the time, the demarc is a
jack that has an RJ-45 (8-pin modular) female connector located in a
telecommunications closet.
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Figure below shows a typical DTE-DCE-DTE connection and the devices
used in the network
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DTE-DCE-DTE WAN Connection
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Virtual Private Networks

Introduction
A virtual private network (VPN) allows the creation of private networks
across the Internet, enabling privacy and tunneling of non-TCP/IP
protocols.
Types of VPNs are named based upon the role they play in a business.
There are three different categories of VPNs:

Remote access VPNs Remote access VPNs allow remote users like
telecommuters to securely access the corporate network wherever and
whenever they need to.
.
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
Site-to-site VPNs Site-to-site VPNs, or intranet VPNs, allow a company to
connect its remote sites to the corporate backbone securely over a public
medium like the Internet instead of requiring more expensive WAN
connections like Frame Relay.

Extranet VPNs Extranet VPNs allow an organization’s suppliers, partners,
and customers to be connected to the corporate network in a limited way
for business-to-business (B2B) communications
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Configuring VPNs/IPSec Using
the SDM
I powered
selected
Create a Site to Site VPN and then clicked Launch the Selected
Task to get
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the Site to Site VPN screen.
I clicked View Defaults and took a peek at what the router was going
to configure:
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After clicking Close, I clicked Next to receive the VPN Connection
21 Information screen:
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I added the static IP address of my peer router (R3), added a pre-shared key, chose my source address
ofpowered
the by
Corp
router, and the destination address, which happens to be the 22
same address as my peer
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router (R3). I then clicked Next.
I received a summary of the VPN configuration running IPSec23
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Test VPN confirmation
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VPN Debugging in action
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Congratulation Message
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THANK YOU
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