What is the MAC architecture, how does it impact wireless networks if it is not configured correctly, and what might occur if a configuration element is missing? What are the different forms of scans and why are they important? What layers are included in the MAC architecture?
The source and destination addresses must always be tracked while sending data across a network. The addressing and defining of protocols and functions necessary for the control and access to a wireless network are dealt with by the 802.11 MAC architecture. Lack of proper configuration will lead to network stations failing to connect to available access points as it gets impossible to authenticate the stations.
The MAC architecture utilizes two layers of the Open Systems Interconnection framework namely the Data-Link (Layer 2) and the Physical (Layer 1) Layers. The Data-Link layer comprises the Logical Link Control sublayer and the Media Access Control sublayer. The role of the Logical Link Control is to receive data directly from the Network layer and transform it into a MAC Service Data Unit (MSDU). In its basic form, an MSDU consists of IP packets and data provided at the LLC sublayer. When MSDU passes to the MAC sublayer, the Media Access Control creates a data frame by appending a MAC header information to form a MAC Protocol Data Unit (MPDU). Data then moves off the MAC sublayer into the Physical Layer which is involved in converting the transferred frames from the Data-Link Layer into bits ready for transmission by appending PHY header information and a preamble (Coleman & Westcott, 2014, p.286 ; CWNP, 2016).
Successful wireless communication begins with client devices scanning for available Access Points. Stations can either perform passive or active scanning to identify Access Points. Passive scanning involves a station listening for beacon frames that have the same SSID as that configured within their software and if successful the station connects to the AP broadcasting the SSID. When multiple APs broadcast the same SSID, a station connects to the AP with the best signal strength.
On the other hand, client stations may send active signals to Access Points. Active signal involves sending either a directed or null probe request. A directed probe request consists of management frames with specific SSID that a client is in search of while a null probe request contains no SSID and implies that the client is looking for any available SSID AP. Any present APs then send probe responses which the client stations can choose to connect to either. Scanning is important as it enables a station to determine available access points and connect to the strongest signal (Westcott & Coleman, 2014, p.295).
What kind of issues did you run into while building your virtual machine? Did you learn something that surprised you, something new, what kind of troubleshooting issues did you run into if any?
By application of virtualization, virtual machines have reshaped how we conduct businesses. It is possible to run an operating system inside another operating system similar to running a program on a local machine. In an attempt to build my own virtual machine using VMware player 5, I learned that even though the installation process was simple, a simple mistake in setting it up could result in a fresh reinstallation. For instance, I specified a disk capacity of 20 GB during installation only to realize later that my virtual drive was filling up yet I needed more space to install the programs and software I needed. This capability was not possible in the virtual machine settings. Additionally, determining the optimum RAM to allocate a specific virtual machine was a problem as it was not possible to know what criteria to use to balance RAM usage by the local Operating system and by the virtual operating system.
Another notable issue was that whenever I tried updating the VMware tools, the update always failed and I had to download them separately from the browser. It was also hard to figure out how to enable file sharing between the virtual and local machines. At some point, the antivirus program was running on the local operating system while I was operating on the virtual machine. The performance of the virtual machine reduced greatly when an antivirus program was running. I found out that the antivirus program was scanning the files in the VM disk thereby reducing its performance (Portnoy, 2012). Even when the antivirus program wasn't running I still witnessed the sluggish performance of the virtual machine. I then learned that I had set the local machine's power plan to power saving mode. Changing the plan to high performance significantly increased my virtual machine's performance. I was happy to note that virtualization enables the running of multiple operating systems in the same physical platform while utilizing the same hardware resources.
References
Coleman, D. D., & Westcott, D. A. (2014). CWNA Certified Wireless Network Administrator official study guide.
CWNP. (2016, August 1). 802.11 MAC Series – Basics of MAC Architecture – Part 1 of 3. Retrieved from https://www.cwnp.com/802.11-mac-series-ndash-basics-mac-architecture-ndash-part-1-3
Portnoy, M. (2012). Virtualization Essentials. John Wiley & Sons.
