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by: Myrtis Lowe


Myrtis Lowe
GPA 3.97


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Class Notes
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This 5 page Class Notes was uploaded by Myrtis Lowe on Wednesday September 9, 2015. The Class Notes belongs to IMT 546 at University of Washington taught by Staff in Fall. Since its upload, it has received 14 views. For similar materials see /class/192126/imt-546-university-of-washington in Information Management at University of Washington.


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Date Created: 09/09/15
Cisco Extending Your LAN Wide Area Networks Page 1 of 5 Farmels Tlaining White Papers White Paper Extending Your LAN Wide Area Networks Have you ever had to send an ovemightdelivery package If the answer is quotyesquot you understand the need to move information over long distances rapidly It39s not a new problem In this age of information the need to send data over long distances is a necessity Fortunately technologies have been developed that enable networks and their users to communicate and exchange data quickly and easilyino matter their geographic location This is what makes long distance networking such a valuable tool This article will explain the following about long distance networking Define what a Wide Area Network WAN is Identify and define the various components that make up a WAN Explain what a digital phone service is and how it relates to the WAN Explain how you can use the Internet for assistance when assembling your WAN A WAN is a network that links together two or more geographically dispersed LANs Local Area Networks usually via highspeed phone lines such as T1 lines or 56K frame relay A good example of a very large and complicated WAN is the Internet WANs are helpful in many ways Merchants use WANs to verify the validity of a buyer39s credit card when performing a transaction VPNs Virtual Private Networks employ WANs when creating secure connections between users on different private networks Companies provide traveling employees with access to network resources via private dialup links In the nal analysis a WAN is just a way to extend network resources beyond the local area WANs Require Planning WANs more than LANs require a great deal of planning and purpose in order to function effectively Also because of the variety of applications that can run on networks the creation of a WAN can sometimes require a great deal of knowledge WANs built without a clear purpose can quickly become exercises in futility and monetary waste Before you build a WAN ask yourself the following questions 0 Do users in multiple locations need to have realtime access to a common database 0 Do your remote locations already have LANs or are they mostly home or oneperson offices 0 What services should your WAN offer Databases File services Email Something else 0 Will your remote sites be able to administer their end of a WAN or will an IT staff be needed 0 Are you willing to pay the costs of highspeed digital phone lines If you have users with needs for realtime access to a common database a WAN can offer real value If you re dealing with small offices or home offices some type of system administration will probably be needed WAN Hardware httpwwwciscocomwarppublic779smbizcommunitywan extendhtml 11172004 Cisco Extending Your LAN Wide Area Networks Page 2 of 5 Several pieces of hardware can be used to link LANs Of these bridgesswitches gateways and routers are the most common Brid ges Switches A bridge or switch which is a multiport bridge is a network device that essentially bridges two LANs together at the Open System Interconnection OSI Layer 2 level For all practical purposes when a bridge switch links together multiple networks users see a larger version of their current network Because of this they can access remote resources employing the same methods they use in their local LAN Bridges and or switches are often used for networks that use protocols that cannot be routed for example NetBIOS or NetBEUI Bridges became commercially available in the early 1980s At the time of their introduction bridges enabled packet forwarding between homogeneous networks This changed with the introduction and standardization of Ethernet and Token Ring networks Today switching technology has emerged as the evolutionary heir to bridgebased intemetworking solutions Superior throughput performance higher port density lower perport cost and greater exibility have contributed to the emergence of switches as a replacement technology for bridges and as a complement to routing technology More information on bridges anal switches Bridges Switches Cisco Catalyst 2950 Series Intelligent Ethernet Switch Gateways Protocol Translators A gateway can refer to a variety of different hardware and software devices that enable communication between computer networks using different communications protocols At its basic level a gateway acts as a twoway path between networks For example in an Intemetconnected network a proxy server can be a gateway between the internal network and the external Internet Any device that passes IP packets from one network to another via the Internet is also commonly referred to as a gateway Though routers can be called gateways most gateways have specific purposes other than routing packets between networks Routers Routers pass data between multiple networks and work at the OSI Layer 3 level Network Layer This means that they must be able to understand the data packets so that they can pass them to their destination Routers are essentially computers optimized for handling packets that have to be transferred between separate networks Routers attempt to send packets from their source to their destination in the fastest way possible which is not always the absolute shortest path More information on how routers work Routing Basics 101 Routing Basics A Technical Overview For information on Cisco SMB routers Cisco SOHO Series Cisco 800 Series httpwwwciscocomwarppublic779smbizcommunitywan extendhtml 11172004 Cisco Extending Your LAN Wide Area Networks Page 3 of 5 Cisco 1700 Series Access Routers High Speed Data Access WANs typically link to each other using highspeed digital phone lines Although most digital phone services are slower than the local LAN they provide sufficient bandwidth for users to access resources with reasonable performance Digital phone services are available in a variety of speeds services and prices There are also alternatives to local phone lines such as satellite links and wireless links These alternatives are particularly popular in parts of the world where the telecommunications infrastructure is limited Trunk Lines T1 and T3 Trunk lines are the backbone of longdistance packetswitched networks Speeds range from 128 kilobits per second to 45 megabits per second T1 lines operate at 1544 megabits per second and are often used to interconnect small to medium business WANs together T3 lines with a bandwidth of 44736 megabits per second are usually used by larger corporation and are relatively expensive Leased Lines Trunk links are often called leased lines When you purchase a fractional or full T1 data services from a telephone company you ll receive a pointtopoint line a circuit that carries data only between two specific points Those two points can be two of your independent offices buildings in which case you39d have a WAN Another possibility one end could be your office while the other is the Internet service provider ISP that connects you to the Internet Frame Relay Frame relay is one of the popular methods used to carry data over digital phones lines such as T1s and 56Ks Common uses for frame relay are Internet connections and as links between multiple sites Integrated Services Digital Network ISDN ISDN is comprised of digital telephony and datatransport services offered by regional telephone carriers ISDN involves the digitization of the telephone network which permits voice data text graphics music video and other source material to be transmitted over existing telephone wires The emergence of ISDN represented an effort to standardize subscriber services usernetwork interfaces and network and intemetwork capabilities In the US today ISDN is being replaced by faster and cheaper DSL services Digital Subscriber Lines DSL The telephone company39s latest entry into the digital phone line market is DSL service DSL is at least as fast as a T1 but unlike a T1 it runs over standard twowire telephone wire The cost of DSL is becoming cheaper and cheaper These days it s possible to get DSL service for about 50 a month DSL is available in a variety of configurations o Asymmetric Digital Subscriber Line ADSL ASDL is usually used for Internet access because the download speed data coming into the network is much faster than the upload speed data httpwwwciscocomwarppublic779smbizcommunitywan extendhtml 11172004 Cisco Extending Your LAN Wide Area Networks Page 4 of 5 going out of the network 0 Highspeed Digital Subscriber Lines HDSL are much more useful for business WANs because the download and upload speeds are the same HDSL transmits data at asymmetrical speeds and at T1 data rates 1544mbps over distances of 12000 feet or less 0 Rate Adaptive DSL RADSL is a useful tool for WANs that are more spread out RADSL can change its speed in response to line conditions It can work farther from central offices up to 6 miles 0 Very high bit rate Digital Subscriber Line VDSL is the fastest member of the DSL family This technology is best for campus WANs with distances up to 1000 feet and speeds up to 10 mbps Service Level Agreements and Quality of Service When you order digital phone lines make certain that you write out and contract a Service Level Agreement SLA or a Quality of Service QoS guarantee These are powerful tools to hold WAN downtime to a minimum Can the Internet help you build your WAN Because of the high costs of digital phone service building a WAN network with remote sites linked together with digital lines can be very expensive Part of the expense is inescapable because it is necessary to connect networks together on a reliable ongoing basis with a high degree of security However there may be additional costs to consider when developing a private WAN such as the cost of one or more system administrators and the overhead that comes with the management of a private network As the Internet has grown Internet Service Providers such as ATampT SprintNet Netcom and others have gotten involved in the business of providing WAN services Their business models differ from a consultant39s model in one major fashion They view their connection services instead of their expertise as the service being sold ISPs elect to absorb a large chuck of the cost of integrating digital phone lines and WAN technology choosing instead to make their money on the network service being provided VPNs Because the ISP has a computerbased network it is an easy for them to set up reliable relatively secure WANs for their clients How do they do it The ISPs networking infrastructure is designed solely for the purpose of specifying how data routes from point A to point B and back again If they set up their routers to route packets coming from certain networks only to certain other networks and use the Internet as a transport between ISP service locations they have set up a type of WAN called a Virtual Private Network or VPN For all practical purposes a VPN accomplishes the same tasks as a totally dedicated pointtopoint digital phone linebased WAN but costs less and requires less enduser maintenance The costs will be included in your monthly ISP fee Security Issues with VPNs Although a VPN is a less costly WAN alternative it is not secure If plain text such as your credit card number is transported across the Internet a third party can capture it So if you plan to use VPNs you ll want to encrypt all data that will be transmitted Encryption technology can be set up by the ISP or by httpwwwciscocomwarppublic779smbizcommunitywan extendhtml 11172004 Cisco Extending Your LAN Wide Area Networks Page 5 of 5 the business itself More information on Cisco Systems VPN Solutions Virtual Private Networks Conclusion In this article you have learned what a WAN is and how it is put together You have also learned how WANs use the digital phone service and how the Internet can help you to build a portion of your WAN with the use of encrypted VPN links For more information on Cisco WAN and Remote Access Solutions Cisco SmallMedium Business I Home How to Buy nghl Register Feedback Site Map Help I Posted Thu Jul 18 140414 PST 2002 All contents are Copyright 19922002 Cisco Systems Inc All rights reserved Important Notices and Privacy Statement httpwwwciscocomwarppublic779smbizcommunitywan extendhtml 11172004


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