To be honest theres a lot...
Answer:
one dependent and on or more independent variables are related.
Answer:The move from hubs (shared networks) to switched networks was a big improvement. Control over collisions, increased throughput, and the additional features offered by switches all provide ample incentive to upgrade infrastructure. But Layer 2 switched topologies are not without their difficulties. Extensive flat topologies can create congested broadcast domains and can involve compromises with security, redundancy, and load balancing. These issues can be mitigated through the use of virtual local area networks, or VLANs. This chapter provides the structure and operation of VLANs as standardized in IEEE 802.1Q. This discussion will include trunking methods used for interconnecting devices on VLANs.
Problem: Big Broadcast Domains
With any single shared media LAN segment, transmissions propagate through the entire segment. As traffic activity increases, more collisions occur and transmitting nodes must back off and wait before attempting the transmission again. While the collision is cleared, other nodes must also wait, further increasing congestion on the LAN segment.
The left side of Figure 4-1 depicts a small network in which PC 2 and PC 4 attempt transmissions at the same time. The frames propagate away from the computers, eventually colliding with each other somewhere in between the two nodes as shown on the right. The increased voltage and power then propagate away from the scene of the collision. Note that the collision does not continue past the switches on either end. These are the boundaries of the collision domain. This is one of the primary reasons for switches replacing hubs. Hubs (and access points) simply do not scale well as network traffic increases.
Explanation:
Consider a fluid of density, ρ moving with a velocity, U over a flat plate of length, L.
Let the Kinematic viscosity of the fluid be ν.
Let the flow over the fluid be laminar for a distance x from the leading edge.
Now this distance is called the critical distance.
Therefore, for a laminar flow, the critical distance can be defined as the distance from the leading edge of the plate where the Reynolds number is equal to 5 x 
And Reynolds number is a dimensionless number which determines whether a flow is laminar or turbulent.
Mathematically, we can write,
Re = 
or 5 x = ( for a laminar flow )
Therefore, critical distance
So x is defined as the critical distance upto which the flow is laminar.
