WANs

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30 Οκτ 2013 (πριν από 3 χρόνια και 10 μήνες)

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© 2004, Cisco Sy stems, Inc. All rights reserv ed.


WAN Technologies


Based on

CCNA 4 v3.1 Slides

Compiled & modified by C. Pham

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Wide
-
area Networks (WANs)

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Metropolitan
-
Area Network (MANs)

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Path Determination

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Internetworking


Any internetwork must include the following:

Consistent end
-
to
-
end addressing

Addresses that represent network topologies

Best path selection

Dynamic or static routing

Switching

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Router: core of WAN technologies


Routers send packets from one
interface/network to another

©cisco

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WAN Topology

Star Topology

Full
-
Mesh Topology

Partial
-
Mesh Topology

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Router Internal Components

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Router Internal Components

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Internal Components of a 2600 Router

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External Connections on a 2600 Router

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Router External Connections

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Computer or Terminal Console
Connection

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Modem Connection to Console or
Auxiliary Port

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WAN Technology

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WAN Service Providers

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Physical Layer: WANs

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WAN Types

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Router Serial WAN Connectors

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DCE Serial Connections

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WAN Line Types and Bandwidth

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CSU/DSU

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Modem Transmission

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WAN Standards

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WAN Encapsulation

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WAN Data
-
Link Protocols

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Circuit Switching

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Packet Switching

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WAN Link Options

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WAN Link Options

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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


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


X.25 provides a low bit rate,
shared
-
variable capacity that
may either be switched or
permanent

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Frame Relay


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


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


Enhanced Cable Modems enable two
-
way. High speed data transmissions
using the same coaxial lines that
transmit cable television.

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Cable Data Network Architecture

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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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Steps In WAN Design

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Three
-
Layer Design Model


The links connecting the various sites in an
area that provide access to the enterprise
network are called the access links or
access layer of the WAN.


Traffic between areas is distributed by the
distribution links, and is moved onto the
core links for transfer to other regions,
when necessary.

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Advantages of the Hierarchical Approach


Scalability: networks can grow without sacrificing
control or manageability


Ease of Implementation: clear functionality at each
layer


Ease of troubleshooting: Isolation of problems in the
network is easier


Predicatability network modelling and caapacity
plannng easier


Protocol Support: mixing current and future
applications and protocols is easier


Manageability: all the above improve the
manageability of the network

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Internet for WAN Connectivity

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One
-
Layer Hierarchy

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Using the Internet as an Enterprise WAN


E
nterprise WANs will have

connections to the Internet.


This poses security problems but also provides an
alternative for inter
-
branch traffic.


VPN technologies can solve security issues

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TCP/IP Model

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Encapsulation

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Summary