Write down two problems in 802 11 MAC sub la) er protocol.Discuss in detail about the wireless IAN MAC sub layers.

Subject Computer Network
NU Year Set: 4.(a) Marks: 2+4=6 Year: 2017

In this experiment, we will capture traffic on an 802.11 network and observe the 802.11 MAC frame fields using Wireshark. You will have to download and install Wireshark to run this experiment. You should do this before your reservation on the wireless testbed.
It should take about 60-120 minutes to run this experiment, but you will need to have reserved that time in advance. This experiment uses wireless resources, and you can only use wireless resources on GENI during a reservation.
To reproduce this experiment on GENI, you will need an account on the GENI Portal, and you will need to have joined a project. You should have already uploaded your SSH keys to the portal. The project lead of the project you belong to must have enabled wireless for the project. Finally, you must have reserved time on the WITesttestbed, and you must run this experiment during your reserved time. (Alternatively, you can use the "outdoor" or "sb4" testbeds at ORBIT, with some modifications to the instructions.

This topic provides an introduction to the MAC sublayer of the data link layer (Layer 2).
In Layer 2 of a network, the Media Access Control (MAC) sublayer provides addressing and channel access control mechanisms that enable several terminals or network nodes to communicate in a network.
The MAC sublayer acts as an interface between the logical link control (LLC) Ethernet sublayer and Layer 1 (the physical layer). The MAC sublayer emulates a full-duplex logical communication channel in a multipoint network. This channel may provide unicast, multicast, or broadcast communication service. The MAC sublayer uses MAC protocols to prevent collisions.
In Layer 2, multiple devices on the same physical link can uniquely identify one another at the data link layer, by using the MAC addresses that are assigned to all ports on a switch. A MAC algorithm accepts as input a secret key and an arbitrary-length message to be authenticated, and outputs a MAC address.
A MAC address is a 12-digit hexadecimal number (48 bits in long). MAC addresses are usually written in one of these formats:
MM:MM:MM:SS:SS:SS
MM-MM-MM-SS-SS-SS

The first half of a MAC address contains the ID number of the adapter manufacturer. These IDs are regulated by an Internet standards body. The second half of a MAC address represents the serial number assigned to the adapter by the manufacturer.
Contrast MAC addressing, which works at Layer 2, with IP addressing, which runs at Layer 3 (networking and routing). One way to remember the difference is that the MAC addresses apply to a physical or virtual node, whereas IP addresses apply to the software implementation of that node. MAC addresses are typically fixed on a per-node basis, whereas IP addresses change when the node moves from one part of the network to another.
IP networks maintain a mapping between the IP and MAC addresses of a node using the Address Resolution Protocol (ARP) table. DHCP also typically uses MAC addresses when assigning IP addresses to nodes.

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