chapter 1 - ccna4

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2006 Cisco Systems, Inc. All rights reserved. Cisco Public 1Version 4.0

Services in a Converged

WAN

Accessing the WAN

Chapter 1


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2006 Cisco Systems, Inc. All rights reserved. Cisco Public 3

Describe How ECNM Provides IntegratedServices over an Enterprise Network

A WAN is a data communications network thatoperates beyond the geographic scope of a LAN.


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Three major characteristics of WANs:

WANs generally connect devices that are separated by a broadergeographical area than can be served by a LAN.

WANs use the services of carriers, such as telephone companies,cable companies, satellite systems, and network providers.

WANs use serial connections of various types to provide access tobandwidth over large geographic areas.

People in the regional or branch offices of an organization need tobe able to communicate and share data with the central site.

Organizations often want to share information with otherorganizations across large distances.

Employees who travel on company business frequently need toaccess information that resides on their corporate networks.


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networks become complex and expensive to manage.

Because the network is a mixture of newer and older technologies,it can be difficult to support and maintain.

Outages and poor performance

Cisco Enterprise Architecture that has relevance to the differentstages of growth of a business.

designed to provide network plannerswith a roadmap for network growth asthe business moves through different

stages




Enterprise Campus Architecture

A campus network is a building or group of buildingsconnected into one enterprise network that consists ofmany LANs. A campus is generally limited to a fixed

geographic area, but it can span several neighboringbuildings

methods to create a scalable network, while addressingthe needs of campus-style business operations.

The architecture is modular and can easily expand toinclude additional campus buildings or floors as theenterprise grows.




Enterprise Edge Architecture

voice, video, and data services outside the enterprise.

use Internet and partner resources, and provide

resources for its customers. This module often functions as a liaison between the

campus module and the other modules in the EnterpriseArchitecture.

Enterprise Branch Architecture

extend the applications and services to remote locationsand users

focuses on the technologies that are often implemented


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Describe the Key WAN TechnologyConcepts




Customer Premises Equipment (CPE)-The devices and inside wiring locatedat the premises of the subscriber and connected with a telecommunicationchannel of a carrier.

Data Communications Equipment (DCE)- primarily provides an interface toconnect subscribers to a communication link on the WAN cloud.

Data Terminal Equipment (DTE)-The customer devices that pass the datafrom a customer network for transmission over the WAN.

Demarcation Point- separate customer equipment from service providerequipment. Physically, the demarcation point is the cabling junction box,located on the customer premises, that connects the CPE wiring to the local

loop. Local Loop- cable that connects the CPE at the subscriber site to the CO of

the service provider.

Central Office (CO)-A local service provider facility or building where localtelephone cables link to long-haul, all-digital, fiber-optic communicationslines through a system of switches and other equipment.




Modem-Modulates and demodulates the carrier signal

CSU/DSU- The CSU provides termination for the digital signal andensures connection integrity through error correction and linemonitoring. The DSU converts the T-carrier line frames into framesthat the LAN can interpret and vice versa.

Access server- Concentrates dial-in and dial-out usercommunications.

WAN switch- switch traffic such as Frame Relay, ATM, or X.25.PSTN switches used for circuit-switched connections, Integrated

Services Digital Network (ISDN) or analog dialup. Router-Provides internetworking and WAN access interface ports.

Core router- backbone of the WAN. able to support multipletelecommunications interfaces of the highest speed in use in theWAN core


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A circuit-switchednetwork is one thatestablishes a dedicatedcircuit (or channel)between nodes and

terminals before theusers may communicate.

PSTN and ISDN are twotypes of circuit-switchingtechnology that may be

used to implement aWAN in an enterprisesetting.



Describe the Key WAN TechnologyConcepts

packet switching splitstraffic data into packetsthat are routed over ashared network

Connectionless Connection-oriented

Frame RelayDataLink Connection

Identifiers (DLCIs).

Lower costs

More delay and jitter


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Select the Appropriate WAN Technology to meetECNM Requirements


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permanent dedicated connections, leased from a carrier and arecalled leased lines.

provide a pre-established WAN communications path from thecustomer premises to a remote destination.

More expensive based on bandwidth and distance Advantages: removes latency or jitter

between the endpoints, Constantavailability

Disadvantages: capacity unused,

increases equipment costs,Any changes require a site visit bythe carrier.


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Integrated Services Digital Network (ISDN) is a circuit-switching technology

64 kb/s bearer channels (B) for carrying voice or data

signaling, delta channel (D) for call setup and other purposes.

Basic Rate Interface (BRI)- provides two 64 kb/s B channels and a 16 kb/s Dchannel.

Primary Rate Interface (PRI)- 23 B channels with 64 kb/s and one D channelwith 64 kb/s in North America, 1.544 Mb/s. In Europe, Australia, and otherparts 30 B channels and one D channel, 2.048 Mb/s


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Select the Appropriate WAN Technology to meetECNM Requirements

Frame Relay

simpler protocol that works at the DataLink

no error or flow control, reducedlatency,

data rates up to 4 Mb/s Frame Relay VCs are identified by a

DLCI, which ensures bidirectionalcommunication from one DTE device toanother.

provides permanent, shared, medium-bandwidth connectivity that carries bothvoice and data traffic.

cost-effective connections betweenwidely scattered LANs.


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Asynchronous Transfer Mode (ATM)

technology is capable of transferringvoice, video, and data throughprivate and public networks.

ATM cells fixed length of 53 bytes : 5byte ATM header followed by 48

bytes of ATM payload. voice and video traffic because of

less delay.

support link speeds of T1/E1 to OC-12 (622 Mb/s) and higher.

ATM offers both PVCs and SVCs,although PVCs are more commonwith WANs.

multiple VCs on a single leased-lineconnection to the network edge.


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DSL technology usesexisting twisted-pairtelephone lines totransport high-bandwidth data, and

provides IP servicesto subscribers.

Multiple DSLsubscriber lines aremultiplexed into a

single, high-capacitylink using a DSLaccess multiplexer(DSLAM) at theprovider location.

data rates of up to8.192 Mb/s.


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A VPN is an encrypted connection between privatenetworks over a public network such as the Internet.

uses virtual connections called VPN tunnels, which arerouted through the Internet from the private network of

the company to the remote site

VPN Benefits

Cost savings

Security

Scalability

Compatibility with broadband technology


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Site-to-site VPNs

connect entire networksto each other

Each site is equippedwith a VPN gateway,such as a router,firewall, VPNconcentrator, orsecurity appliance.


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Remote-access VPNs

enable individual hoststo access a companynetwork securely overthe Internet.

VPN client softwareloaded or uses a web-based client.


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Reducedexpenses andadministration

Easy integrationwith existingnetworks

Enhanced

businessproductivity


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Summary

A WAN is defined as

A data communications network that operates beyond thegeographic 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 furtherdivides the enterprise network into

Physical areas

Logical areas

Functional areas

Selecting the appropriate WAN technology requiresconsidering some of the following:

WANs purpose

Geographic scope of WANTraffic requirements

If WAN uses a public or private infrastructure


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