designing a wireless network phần 6 potx

Designing a Wireless Network • Chapter 5 173 applying their technical expertise during the various stages of the net- work lifecycle. Referred to as the Network Engagement Methodology (NEM), it is a tool developed by the consultants of Lucent ESS and pro- vides best practices, procedures, and tools from their most successful pro- jects.What you will see in this chapter is the basis for what makes up the final network design (the other phases of NEM include business development, initiation and definition, planning, execution and control, and finally, closeout.This section provides information on the execution and control phase, specifically tuned for a service provider network. The execution and control phase has been broken down into five stages: plan, architect, design, implement, and operate.The next several sections provide a high-level description of what makes up the plan, architect, and design stages of NEM. Creating the Network Plan Every good network design begins with a well thought out plan.The network plan is the first step in creating a network design. It is where information regarding desired services, number of users, types of applica- tions, and so forth is gathered.This phase is the brainstorming phase during which the initial ideas are put together.The planning stage can be one of the longest segments of a network design, because it is depen- dent on several factors that can be very time consuming. However, if each planning step is thoroughly completed, the architecture and design stages move along much more quickly. Gathering the Requirements The first and most important step in creating a network plan is to gather the requirements.The requirements will be the basis for formulating the architecture and design. If a requirement is not identified at the begin- ning of the project, the entire design can miss the intended goal of the network.The requirements include: ■ Business Requirements A few examples of possible business requirements are budget, time frame for completion, the impact www.syngress.com 152_wan_05 6/21/01 3:22 PM Page 173 174 Chapter 5 • Designing a Wireless Network of a network outage, and the desired maintenance window to minimize the negative effects of an outage. ■ Regulatory Issues Certain types of wireless networks (such as MMDS) require licenses from the FCC. If the wireless network is going to operate outside of the public RF bands, the regula- tory issues need to be identified. ■ Service Offerings This is the primary justification for the design of a new network or migration of an existing network. Simply, these are services or functionality the network will pro- vide to the end users. ■ Service Levels Committed information rate (CIR) is an example of a service level agreement (SLA).This involves the customer’s expectation of what the service provider guarantees to provide. ■ Customer Base This establishes who the anticipated end users are, and what their anticipated applications and traffic patterns are. ■ Operations, Management, Provisioning, and Administra- tion Requirements This identifies how the new network will impact the individuals performing these job functions, and whether there will be a need to train these individuals. ■ Technical Requirements This can vary from a preferred equipment vendor to management system requirements. ■ Additional Information Any additional information that can affect the outcome of the design. Once all of the requirements have been collected, it is recommended that a meeting be set up with the client to ensure that no key informa- tion is missing.This is important because it not only keeps the client involved, but also allows both the client and network architect to estab- lish and understand the expectations of the other. Once you get client buy-off on the goals and requirements of the network, you can proceed with baselining the existing network. www.syngress.com 152_wan_05 6/21/01 3:22 PM Page 174 Designing a Wireless Network • Chapter 5 175 Baselining the Existing Network The reason you need to baseline the existing network is to provide an accurate picture of the current network environment.This information will be used later on to identify how the new design will incorporate/interface with the existing network.When conducting the baseline, be sure to include the following considerations: ■ Business processes ■ Network architecture ■ IP addressing ■ Network equipment ■ Utilization ■ Bandwidth ■ Growth ■ Performance ■ Traffic patterns ■ Applications ■ Site identification/Surveys ■ Cost analysis With proper identification of these items, you will gain a good understanding of both the existing network and get an idea of any potential issues or design constraints. In the case of utilization—that is, overutilization—unless kept under a watchful eye, it can contribute to a less-than-optimized network.Therefore, by evaluating the health of the existing network, you can either eliminate or compensate for potential risks of the new network. In addition to monitoring network condi- tions, it is also a good idea to perform site surveys in this step, to identify any possible problems that are not identified in either the requirements collection or the baseline monitoring. www.syngress.com 152_wan_05 6/21/01 3:22 PM Page 175 176 Chapter 5 • Designing a Wireless Network Analyzing the Competitive Practices When you compare the client’s business and technology plan to the competitors’ in the same industry, you can learn what has and hasn’t worked and why. Once you have evaluated and understand the industry practices, you can identify what not to do as well.This is a potential opportunity for a network architect to influence the functionality, in terms of services and choice of technology, that will facilitate the desired network.The primary reason the architect is involved is because of his or her knowledge of the technology—not only how it works, but also how it is evolving. Beginning the Operations Planning The operations systems support daily activities of telecommunications infrastructures.The purpose of this step is to identify all of the elements required for the operations system. Depending on the needs of the client, any or all of the following processes need to be identified: ■ Pre-order ■ Order management ■ Provisioning ■ Billing ■ Maintenance ■ Repair ■ Customer care If your client is not planning on offering any services with the new design, then this step can be skipped. Once the operations planning step is complete, you can move on to the gap analysis. Performing a Gap Analysis The gap analysis will be a comparison of the existing network to the future requirements.The information obtained through the gathering of www.syngress.com 152_wan_05 6/21/01 3:22 PM Page 176 Designing a Wireless Network • Chapter 5 177 requirements and baselining of the current network provide the data needed to develop a gap analysis.The gap analysis is a method of devel- oping a plan to improve the existing network, and integrate the new requirements.The documented result should include the following items: ■ Baseline ■ Future requirements ■ Gap analysis ■ Alternative technology options ■ Plan of action Once the client reviews and accepts the requirements’ definition document and gap analysis, the time frame required to complete the project becomes more evident. At this point, the client should have a good understanding of what the current network entails and what it will take to evolve into their future network. Once this step is complete, the next task is to create a technology plan. Creating a Technology Plan This step involves identifying the technology that will enable the busi- ness goals to be accomplished.There can be several different technology plans—a primary plan and any number of alternatives.The alternative plans can be in anticipation of constraints not uncovered yet, such as budget. Being able to provide alternatives allows the client some options; it provides them with a choice regarding the direction of their network and the particular features that are of top priority. Oftentimes, until a plan is devised and on paper, the “big picture” (the process from ideas to a functioning network) can be somewhat difficult to realize fully. The technology plan should identify what types of equipment, trans- port, protocols, and so on will be used in the network. Make sure that the plan has both a short-term focus (usually up to a year), and a long- term outlook (typically a 3 to 5 year plan). Creating a good technology plan requires that you understand the existing technology, migration www.syngress.com 152_wan_05 6/21/01 3:22 PM Page 177 178 Chapter 5 • Designing a Wireless Network paths, and future technology plans.There are several steps you can take when creating a technology plan. Some of the more important steps include: ■ Business assessment ■ Future requirements analysis ■ Current network assessment ■ Identifying technology trends and options ■ Mapping technology to client needs The technology plan will not contain specific details about how the new network will operate—it will identify the technologies that will enable the network. Creating an Integration Plan Whenever a new service, application, network component, or network is added to an existing network, an integration plan needs to be created. The integration plan will specify what systems will be integrated, where, and how.The plan should also include details as to what level of testing will be done prior to the integration. Most importantly, the integration plan must include the steps required to complete the integration.This is where the information from the gap analysis is utilized. As you may recall, the gap analysis provides information on what the network is lacking, and the integration plan provides the information on how the gaps will be resolved. Beginning the Collocation Planning If the network needs to locate some of its equipment off the premises of the client, collocation agreements will need to be made. Specifically with wireless networks, if you plan on connecting buildings together and you lease the buildings, you will need to collocate the equipment on the rooftops. Depending on the amount of collocation required, this step can be skipped or it can be a significantly large portion of the plan phase. www.syngress.com 152_wan_05 6/21/01 3:22 PM Page 178 Designing a Wireless Network • Chapter 5 179 Performing a Risk Analysis It is important to identify any risks that the client could be facing or offering its perspective customers. Once the risks have been identified, you will need to document and present them to the client.The way to identify risks is by relating them to the return they will provide (such as cost savings, increased customer satisfaction, increased revenue, and so on). An easy way to present the various risks is in a matrix form, where you place risk on the horizontal axis and return on the vertical axis. Assign the zero value of the matrix (lower left corner) a low setting for both risk and return, and assign the max value (upper right corner) a high setting.This provides a visual representation of the potential risks. Once the matrix is created, each service can be put in the matrix based on where they fit. An example of this would be providing e-mail ser- vice, which would be put in the lower left corner of the matrix (low risk, low return). This is important because you are empowering the client to make certain decisions based on industry and technological information. For example, if the client is planning on offering a service and is unaware that the service is high risk with low return, the client will need to offset or eliminate the risk. Perhaps the client could offer a service package pairing the high risk, low return with a low risk, high return service. After all, the goal is to help make your client successful. Once the client accepts the risk analysis, the action plan can be created. Creating an Action Plan Once all of the previous planning steps have been completed, an action plan needs to be created.The action plan identifies the recommended “next steps.”The recommended next steps can either identify what needs to be done to prepare for the architecture phase (such as a project plan), or what action needs to be taken to clarify/correct any problems encountered during the planning phase. For example, with a situation as indicated in the risk analysis section previously, the action plan may need to provide a solution to a particular risk. Basically, the action plan func- tions to address any open issues from the information gathering stages. www.syngress.com 152_wan_05 6/21/01 3:22 PM Page 179 180 Chapter 5 • Designing a Wireless Network This step is to ensure all of the required information has been obtained in order to provide the best solution for the client. As soon as the action plan is created and approved, the planning deliverables can be prepared. Preparing the Planning Deliverables The last step in the plan phase is to gather all information and docu- mentation created throughout the plan and put them into a deliverable document.This is somewhat of a sanity checkpoint, in terms of making the client fully aware of the plans you have devised and what to expect for the remainder of the project. Some of the items to include in the document are: ■ Requirements document ■ Current environment analysis ■ Industry practices analysis ■ Operations plan ■ Gap analysis ■ Technology plan ■ Collocation plan ■ Risk analysis ■ Action plan Once the planning deliverable document is complete and has been presented to the client, the next phase of the network design can begin. Developing the Network Architecture The network architecture is also referred to as a high-level design. It is a phase where all of the planning information is used to begin a concep- tual design of the new network. It does not include specific details to the design, nor does it provide enough information to begin implemen- tation. (This will be explained in greater detail in the following sec- tions.) The architecture phase is responsible for marrying the results of www.syngress.com 152_wan_05 6/21/01 3:22 PM Page 180 Designing a Wireless Network • Chapter 5 181 the planning phase with the client’s expectations and requirements for the network. Reviewing and Validating the Planning Phase The first step in developing a network architecture is to review and vali- date the results of the planning phase. Once you have thoroughly gone through the results of the planning phase, and you understand and agree to them, you are finished with this step and can move on to creating a high level topology.The reason that this step is included here is that many times teams on large projects will be assembled but the architec- ture team can consist of people that were not in the plan team.This step is to get everyone familiar with what was completed prior to his or her participation. Creating a High-Level Topology A high-level topology describes the logical architecture of a network.The logical architecture should describe the functions required to implement a network and the relationship between the functions.The logical archi- tecture can be used to describe how different components of the net- work will interoperate, such as how a network verifies the authentication of users.The high-level topology will not include such granularity as specific hardware, for example; rather, it illustrates the desired functionality of the network. Some of the components to include in the high-level topology are: ■ Logical network diagrams ■ Functional network diagrams ■ Radio frequency topology ■ Call/Data flows ■ Functional connectivity to resources ■ Wireless network topology www.syngress.com 152_wan_05 6/21/01 3:22 PM Page 181 182 Chapter 5 • Designing a Wireless Network Creating a Collocation Architecture Once the collocation plan has been complete, a more detailed architecture needs to be created.The architecture should include information that will be used as part of the requirements package that you give to ven- dors for bids on locations. Information to include in the requirements includes: ■ Power requirements in Watts ■ Amperage requirements ■ Voltage (both AC and DC) values ■ BTU dissipated by the equipment ■ Equipment and cabinet quantity and dimensions ■ Equipment weight ■ Equipment drawings (front, side, top, and back views) ■ Environmental requirements The intention of this type of architecture is to provide information to assist in issuing either a request for information (RFI) or a request for proposal (RFP) to a vendor(s). It is in the best interest of the client to include enough information about the network requirements to evoke an adequate response from the vendor, but not give away information that potentially could be used for competitive intelligence. Defining the High-Level Services The services that the client plans on offering their customers will usually help determine what the necessary equipment requirements will be. These services should match up with the services identified in the risk portion of the plan phase. Once the services have been identified, they need to be documented and compared against the risk matrix to deter- mine what services will be offered.The client typically will already have identified the types of services they are interested in providing, but this is an opportunity to double-check the client’s intentions. Any services www.syngress.com 152_wan_05 6/21/01 3:22 PM Page 182 [...]... Page 202 Chapter 5 • Designing a Wireless Network that security practices between a wired network and a wireless network typically traverse down different paths In a typical wired network, where Layers 1 and 2 (the physical and data-link layers) are regulated by supplying cable runs and network interfaces to known clients on the network, whereas wireless network emissions are distributed freely across... www.parksassociates.com.The Continental Automated Buildings Association (CABA) at www.caba.org is another good source for learning about home network technologies from a broad and unbiased perspective Q: I am trying to create a design of a wireless campus network and I keep finding out new information, causing me to change all of my work How can I prevent this? A: If you have done a thorough job in the planning... factor or device Speculation is rampant as to what the ultimate “gadget” will look like Some believe that the ultimate form factor will incorporate data and www.syngress.com 152_wan_05 6/ 21/01 3:22 PM Page 195 Designing a Wireless Network • Chapter 5 voice capabilities, all within a single handheld device.There is movement in the marketplace that suggests corporations and service providers are embracing... contention in that spectrum Because of the spectral and spatial attributes of a wireless LAN, we recommend that no more than 30 users be configured on a supporting radio with a 10BaseT LAN interface However, up to 50 users may be supported comfortably by a single radio with a 100BaseT LAN connection www.syngress.com 199 152_wan_05 200 6/ 21/01 3:22 PM Page 200 Chapter 5 • Designing a Wireless Network Network... wireless clients, whether in whole or in part, most likely will impact the existing network infrastructure Network Security It is frequently said that an individual’s greatest strengths are often their greatest weaknesses.The same can be said when examining the attributes of a wireless network Both mobility and ease of access are touted as some of the greatest characteristics available when using a. .. architecture phase was completed thoroughly and with accurate information) Basically, the detail design is a compilation of the entire planning process.This is absolutely where the rewards of the prior arduous tasks are fully realized Reviewing and Validating the Network Architecture The first step of a detailed design phase is to review and validate the network architecture.The network architecture is the basis... vital that the wireless network designer takes appropriate measures to ensure the security and stability of the wireless network At a minimum, ensure that the logical placement of your wireless access points, if required, are placed appropriately in front of your network firewall Finally, take into account the value of the information being transmitted and secure it accordingly www.syngress.com 152_wan_05... phase of the design Q: I’m very confused by all the different home network standards Is there any way that I can track several of the different home networking standards from a single unbiased source? A: Yes.There are several means of tracking various home network standards and initiatives For comprehensive reports in the home network industry, I would suggest contacting Parks Associates at www.parksassociates.com.The... diagnostic screens in Figures 5.2 (Screen A) and 5.3 (Screen B) show impacts to data when the angle of reception from the emitted signal is changed by less than five degrees Figure 5.2 Diagnostic Screen A From a physical landscape perspective, we can easily see how physical obstructions may affect signal quality and overall throughput As such, placement of antennas, angles of reception, antenna gain and... remember that Lucent Technologies AP1000 access point affords the user with a total of 11 www.syngress.com 152_wan_05 6/ 21/01 3:22 PM Page 197 Designing a Wireless Network • Chapter 5 useable channels to transport data It is imperative that the network design engineer understands the subscriber relationships to be supported and develops a channel plan accordingly Let’s take a closer look Like traditional short-haul . that will enable the busi- ness goals to be accomplished.There can be several different technology plans a primary plan and any number of alternatives.The alternative plans can be in anticipation. the planning phase. For example, with a situation as indicated in the risk analysis section previously, the action plan may need to provide a solution to a particular risk. Basically, the action. will a support person work with an issue before escalating it? ■ How will an escalation take place? ■ Which procedures will be automated? ■ What tools are available to which organization? ■ What