Introduction
(100-User Wireless LAN-Design & Implementation Analysis)
In this document, I will endeavor to provide a written analysis concerning the design and implementation of a wireless LAN (WLAN) for a firm comprised of one hundred employees. In illustration of the WLAN design, I will make reference to several sources regarding any related content that I’ve found to be pertinent and of practical benefit to this document’s purposes, not least of which is “
Top-Down Network Design ”, by Priscilla Oppenheimer, an instructional text detailing a method of network design that’s based upon what can be readily found evident throughout the overall networking community to be the most logical and efficient sequence of steps necessary in the creation of a network. Having stated this, it is of value for the reader to know that the aforementioned sequence of steps, as examined in Oppenheimer’s work, will correspond closely to the order of WLAN design and management issues that are addressed in this document, and can be followed up by way of documentation found under the same title and author at the end of this article. The major design and management issues found unique to a WLAN involve those pertaining specifically to the transmission and reception of radio frequency (RF) waves. For example, there is the strategic placement of access points (AP), which are devices designed to send and receive radio signals between nodes. This, in turn leads to a consideration of any possibility of physical materials that may be found that could hinder radio signals between APs, which will here be replaced by a ‘worst case’ factoring. Protocols and standards dealing with wireless technology are also unique, as they correlate directly to WLANcharacteristics. In support of wireless communications, physical wiring is also necessary, as the WLAN must at some point connect to a WAN. Obviously, there are more wireless topics than are practical to mention in these few opening lines. The point is, encompassed here within the following pages, presented with thorough detail and explanation, are all of the elements necessary in order for the sufficient insight and understanding of designing, implementing, and managing a WLAN of the specified parameters. Lastly, as with any good LAN design, efforts have been made to acknowledge the critical need for sustaining scalability and expandability

Problem Statement
(Network Design & Management Concentrations)
After careful and prolonged consideration of the prescribed ‘
Terminal Course Objectives (TCOs)
’, which serve to illustrate the primary elements and principal divisions of concentration most suitably related to network design, I’ve had trouble only in choosing which TCOs not to include within the subject matter of central focus. This due largely to the overlapping and complementary nature of networking topics in general. Atlength, the scope of this analysis has been refined within the context of TCO-B, concerning the ideal formulation and configuration of a network that facilitates optimal performance, and TCO-F, regarding the elements of a strategy found sufficient for fostering a maximum state of security within a WLAN. Bear in mind, issues addressed here will necessarily involve topics specific to other TCOs. Consequently, the integrated nature of their contents requires they are at least made mention of, if only in connection to those of central focus, otherwise, they will be given no priority. The intention here, is to present the most plausible method and means by which the specified WLAN may be configured, so as to be conducent to both performance and security, as it could be argued, an optimal state of these combined network attributes might afford management’s efforts with the space necessary from which to iron out and overcome any adjunctive issues that may inevitably arise.

Analysis
(Network Design Methodology, Variability, & Attribution)
As mentioned in the introduction, the concept flow of this document will follow the top-down approach to network design. More specifically, as a form of structured design, the top-down approach is described by Oppenheimer, P., as “focusing on the requirements, applications, and a logical structure before the selection of physical devices and products to implement the design.” Accordingly, having identified the network as wireless has filled a portion of the requirements already. The idea is simple, you can’t know what would be best to use until you know exactly what it is your using it for, and so the rationale behind this paper’s organization follows suit. Unfortunately, the greater part of this WLAN presents the difficult challenge of omitting value from the majority of variables that are present, but thankfully, there’s a simple and effective means of dealing with this, which will be discussed at greater length below. With this in mind, the general sequence of presentation and concept flow isn’t disrupted, and the underlying structural current of thought throughout this document will proceeded naturally, top-down. Serving as a supplemental concept to clearly interpreting the content andmethodology behind the WLAN’s design, the sequence of decisions made throughout the top downapproach utilized here coincides also with a more generalized life-cycle-development process, characterized by the following four steps: of I.)
Analyze the requirements
, II.) Develop the logical design
, III.) Develop the physical design
, and IV.) Test, optimize, and document the design
. (Oppenheimer, P.). While adhering to these structural aids, (
Top-Down Network Design and Life-Cycle-Development-Process
) let us move now within view of the first variables entering into the realm of consideration, as they are found relating to the piecing together of a wireless local area network.

Analyzing the Requirements The top-down method of design begins with an analysis of the business and technical goals that are associated with the network. Here there is ample breathing room as, the only specifications that have been mentioned are the size of the network, (100employees) and the fact that it utilizes wireless technology as a pivotal means of data transmission. A note before moving on; I’ll not be attempting to speculate about the nature of the firm’s operations, which my client desires to implement the WLANfor.However, it may be beneficial to use examples to illustrate certain technical ideas.Having said that, in addition to the established attributes of size and wireless capability, further dimensionality to the network is provided by the chosen TCOs upon which we will focus, i.e., performance and security. With no recourse to the intended use of the network, performance and security will be applied in the most literal sense. For example, in the interest of performance, every provision is made to ensure the best possible performance of the WLAN within the specified parameters. This will present certain challenges in regards to the second priority, security, which will also be given precedence over anything not explicitly pertaining to either itself or performance. In other words, ease of use and budget will be of secondary importance and will only be accommodated insomuch as they relate to either performance or security. So too will follow, in the order of priority, all other issues. Already, we have run into several resultant if not discrete contrasts between the central and decisive variables identified. In response to the first major phase of the top-down design model, researching the client has been cut short by the fact that we don’t know a great deal about what the network will be used for, nor do we have details concerning the organization in general. What we do know however is that despite the unnamed specifics, it can be assumed that the business is either a remote and relatively isolated branch of a larger organization, or a relatively small company being comprised of only one hundred employees. Also, we know that wireless communications are essential, so in the absence of precise details to characterize the nature of those communications, our network must offer the most scalable and proficient solution to the entire range of potential wireless applications and environmental contexts. In my calculations regarding which applications and services will be running over the WLAN, I can do little more than assume in each instance, that the equivalent of a ‘worst case scenario’ is true. Provisions must be madefor a state of exemplary performance to exist under even the most demanding of circumstances, but also with recourse to multiple applications of similar demand.
The above, may induce contrasting and thus difficult criteria, which will in turn end up forcing the pressing trade-off decisions of performance between applications. Though the model of reference here is the ‘worst case scenario’, for determining the priority of decisions which force trade-offs in performance between applications, I will endeavor to lean in the direction of what is most typical or commonly demanded, but only where necessary will the priority of any one characteristic be held above another, as in the anticipated instance of security vs. performance. In this case I must succumb to assigning the TCOs themselves with priority, and will do so according to the order in which I chose them (performance before security). Out of necessity, where a single solution that allows for both optimal performance and security on the WLAN cannot be
Implemented, I will resort to the aforementioned order. In either case, the primaryobjective for design and implementation here is to be prepared for anything, and to provide ideal performance and security in the face of it. At last, in addition to providing a design sufficient for optimal performance and security, due considerations of futurerequirements must be taken into account, which includes those topics pertaining tocontinued optimization through an initial state of scalability.

Developing the Logical Design

The primary difficulty in designing a WLAN for an organization without having reference to the details and dimensions of the physical location’s characteristics, is that there is little that can be done by the way of a site survey. To counter this shortcoming, it must be assumed that there will be significant, if not drastic interference experienced by an intervening wireless signal.

To that extent that, by accounting ahead of time for such obstacles, the degree to which the impact from an actual instance of interference would be felt can be kept at a minimal. By preparing the WLAN, in each scenario, for the worst, most of the impact from indefinable variables will be absorbed before occurring, and if the worst doesn’t occur, than the entire better for the network. To reiterate, this is the general angle of attack for all unforeseeable variable relationships and interactions.

To that extent that, by accounting ahead of time for such obstacles, the degree to which the impact from an actual instance of interference would be felt can be kept at a minimal. By preparing the WLAN, in each scenario, for the worst, most of the impact from indefinable variables will be absorbed before occurring, and if the worst doesn’t occur, than the entire better for the network. To reiterate, this is the general angle of attack for all unforeseeable variable relationships and interactions. The first variable that needs to be addressed is network layer addressing, and along those lines, the WLAN will utilize an internal DHCP server (D-Link DWS-4026), as specified by Cisco.com, to be a viable fit. In order that the highest state of organizational, not to mention network, efficiency is adopted, a high levelimplementation of structured addressing management will be necessary to avoidduplicate or dead addressing space. Addressing will be assigned on the basis of both public and private classifications, as a state promoting the highest degree of scalability, though public addressing only in designated and controlled instances, whereas Network Address Translation is implemented with the private addresses. (Oppenheimer, P.).After having settled matters pertaining to addressing and naming, switching and routing protocols are to be defined, on the basis of what the network’s anticipatedoperations will be characterized by. Here, WLAN characteristics are kept intentionally open-ended; to account not only for a lack of specified network parameters, but also for the highest degree of scalability, while maintaining optimal performance and security.

Among variables factored into consideration here are network trafficcharacteristics, bandwidth, memory, CPU usage, adaptability capacity, and generalfunctionalities as relate to performance and security. To begin, the WLAN will utilize a mesh topology as, in the case of a relatively small network, (about 100-users) costs won’t be an issue, while mesh networking offers the most reliable and scalable configuration, thus providing high resiliency, which in turn factors into performance.Because link-state routing protocols dictate sending and receiving of entirenetwork routing topology maps in addition to the pertinent sections of a routing table, link-state routing is highly conducent to mesh networking. All attributes of the WLAN thus far foster a very open and integrated functionality with all nodes connected, communicating with every other node through link-state routing, OSPF (Webopedia).adoption being amongst the best known routing solutions of this kind, the way is paved for very fast and very reliable routing and addressing, as well as any other matters dealing with performance on a physical basis. Because each node bears the same connection potential in every aspect, very little impact will be felt in the event of an emergency.(Dynamic Routing Protocols). Also, the cost of OSPF is of no consequence here. Due to the small size of this WLAN, as mentioned in “
Top-Down Network design” it will be of benefit here to keep the entirety of all users within the WLANs own subnet. This is said to be conducent to both security and management fluency due to the heightened ease with which traffic filtering may be accomplished. (Oppenheimer, P.).

Utilizing the IEEE 802.11 standard, the WLAN is provided with the capacity to use authentication at access points. By this measure, the degree of unauthorized network traffic is controlled, and the risks to outside threat are minimized. (Oppenheimer, P.).WPA2 is also advisable, being the latest and strongest encryption algorithm, supporting Multiple in Multiple out (MIMO) technology, which is a means for ensuring the potential of significantly stronger signal capacity, than non-MIMO technologies. Bearing the trusted seal in all things ‘network’, Cisco certainly stands out ahead of the pack as a strong consideration. Other Viable Options include Intel and D-Link. While it is difficult to get a definite price on any kind of service agreement without calling in for a quote, Cisco has stood the test of time not only defending its name against competitors, but in customer satisfaction as well.
Implementation Suggestions
(Physical Design Components and Configuration)
To conclude this document, ending comments will pertain to the general physical implementation of the WLAN. Using a wireless mesh configuration that caters to one hundred employees, the Cisco Aironet 1250 Series, though capable of accommodating as many as 800 MAC addresses, would be more practical if place one per twenty five employees. This way, not only is there ample room for expansion, but also the existing traffic requirements, whatever they may be, will be sufficiently accommodated and well within range of 100% signal strength throughout. (Cisco.com).

Having already mentioned the Cisco DHCP server model, DWS-4026, integratedwith the link-state OSPF routing protocol, there should be adequate functionalityaccommodations even for the most demanding traffic loads, as the combination of elements here suggests a perfect interoperability. Adding to this general architecture the security outlay discussed earlier and the way is paved for an optimally functioningwireless LAN, well within means to perform ideally under harsh and/or uncertainconditions. A self-contained WLAN subnet acts as the most efficient means of firewall implementation without sacrificing any notable degree of performance whatsoever. There you have it. Impervious performance, impenetrable security, unmatched interoperability and potential for expandability.

References
Cisco.com. Wireless LAN Controller Configuration. Retrieved Dec 13 th2010 from, http://www.cisco.com/en/US/docs/wireless/controller/4.1/configuration/guide/c41wlan.html#wp1108097 Cisco Aironet 1250 Series. Cisco.com. Retrieved Dec 13 th2010 from, http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps6973/ps8382/product_data_sheet0900aecd806b7c6d.html Clarity-Counseling.com Listing of Service Providers. Retrieved on Dec. 12 th 2010 from,http://www.clarity-consulting.com/wireless_solution_providers.htm#WLAND-Link.com. Network Hardware. Retrieved Dec 12 th 2010 from,http://www.dlink.com/category/productcategories/?cid=17Dynamic Routing Protocols. CS.Virginia.EDU. PDF-File. Retrieved Dec 13 th 2010 from,http://www.cs.virginia.edu/~cs458/slides/module11-ospf.pdf Hughs, A. (2010). Wireless Security Protocols.
Ehow.com.
Retrieved Dec 12, 2010, fromhttp://www.ehow.com/list_6691649_wlan-security-protocols.htmlOppenheimer, P. (2004).
Top-Down Network Design.
Indianapolis, IN: Cisco Press.Mitchell, B. “Wireless Standards”
About.com.
Retrieved Dec. 12 th2010 from,http://compnetworking.about.com/cs/wireless80211/a/aa80211standard.htmWebopedia. (2010). Wireless Mesh Networks. Retrieved Dec 12 th, 2010 from,http://www.webopedia.com/TERM/W/wireless_mesh_network_WMN.htmlWebopedia. (2010). Open Shortest Path First. Retrieved Dec 12 th, 2010 from,http://www.webopedia.com/TERM/O/OSPF.html http://www.webopedia.com/DidYouKnow/Computer_Science/2006/OSPF_Routin g.asp