Mat 17 C — Luis Rademacher Midterm 2 — May 22 — 50 Minutes ✓ Solved

Mat 17 C — Luis Rademacher Midterm 2 — May 22nd — 50 minutes Open book and open notes but every student must write his or her own solution

Solve the following system of differential equations, analyze stability of equilibria, and address network IP subnetting and topology design.

This assignment includes six mathematical and six networking tasks. You are required to provide detailed solutions, including justifications, proofs, and diagrams where applicable. The mathematical problems involve solving systems of ordinary differential equations (ODEs), analyzing their equilibria and stability via linearization, and plotting isoclines. The networking tasks require subnetting of specified IP address ranges, assigning network addresses to VLANs, loopback interfaces, and WAN links, and designing network topology diagrams using Microsoft Visio.

Sample Paper For Above instruction

Solving System of ODEs and Stability Analysis

1. Solving the System of ODEs:

The given system is:

\[

\frac{dx_1}{dt} = 3x_1 - 2x_2, \quad \frac{dx_2}{dt} = x_1 + 4x_2, \quad \text{with initial conditions } x_1(0)=1, x_2(0)=1.

\]

Expressed in matrix form:

\[

\frac{d}{dt}

\begin{bmatrix}

x_1 \\

x_2

\end{bmatrix}

=

\begin{bmatrix}

3 & -2 \\

1 & 4

\end{bmatrix}

\begin{bmatrix}

x_1 \\

x_2

\end{bmatrix}.

\]

The coefficient matrix

\[

A = \begin{bmatrix} 3 & -2 \\ 1 & 4 \end{bmatrix}

\]

has characteristic equation:

\[

\det(A - \lambda I) = (3-\lambda)(4-\lambda) - (-2)(1) = (\lambda^2 - 7\lambda + 14) = 0.

\]

Discriminant \( D = (-7)^2 - 4 \times 1 \times 14 = 49 - 56 = -7

\[

\lambda_{1,2} = \frac{7 \pm i \sqrt{7}}{2}.

\]

Since the real part \(\frac{7}{2} > 0\), solutions exhibit exponential growth with oscillation, indicating an unstable focus at the origin.

2. Compartment Diagram:

The system can be interpreted as a flow between compartments \(x_1\) and \(x_2\). For the general form:

\[

\frac{dx_1}{dt} = a x_1 + b x_2, \quad \frac{dx_2}{dt} = c x_1 + d x_2,

\]

the corresponding diagram has arrows from \(x_1\) to \(x_1\) and \(x_2\) with rates \(a\) and \(b\), respectively, and likewise for \(x_2\). Determining \(a, b, c, d\) directly from the coefficients yields the compartment flow structure; here, for the given matrix, the diagram shows flow from \(x_1\) to itself and \(x_2\), and vice versa, with respective rates.

3. Stability of the equilibrium at (0,0):

The Jacobian matrix at equilibrium is the coefficient matrix \(A\). Eigenvalues analysis shows positive real parts, indicating the equilibrium is an unstable focus.

Analyzing System 2:

\[

\frac{dx_1}{dt} = x_1, \quad \frac{dx_2}{dt} = 0.5 x_2.

\]

The equilibrium is at (0,0), which is unstable as both eigenvalues are positive. The phase portrait consists of trajectories diverging away from the origin along axes.

Analyzing System 3:

\[

\frac{dx_1}{dt} = x_1 x_2, \quad \frac{dx_2}{dt} = x_1 + x_2.

\]

Set derivatives to zero for equilibria:

\[

x_1 x_2 = 0 \Rightarrow x_1=0 \text{ or } x_2=0,

\]

and

\[

x_1 + x_2 = 0.

\]

From these, equilibrium points are at (0,0) and at points where \(x_1=0, x_2=0\). For \(x_1 \neq 0, x_2=0\):

\[

x_1 + 0= 0 \Rightarrow x_1=0,

\]

so only equilibrium at origin. From linearization, eigenvalues indicate the nature of stability: at (0,0), eigenvalues suggest a saddle point, hence unstable.

Graphing zero isoclines, stability of (1,1):

Zero isoclines are the curves where derivatives are zero. For \(\frac{dx_1}{dt} = x_1(2 - x_1)\), zero isoclines are at \(x_1=0\) and \(x_1=2\). For \(\frac{dx_2}{dt} = x_1 x_2 - x_2\), zero isoclines are at \(x_2=0\) or when \(x_1=1\). Plotting these curves shows regions of growth/decay, and analyzing derivatives around (1,1) via Jacobian confirms stability or instability. For (1,1), the Jacobian eigenvalues with negative real parts show it is a stable node.

Network IP Addressing and Topology Design:

- Subnet the NY network (10.150.0.0/16):

The VLANs require specific subnets with respective host requirements. For example, VLAN 35 (Services) with 115 hosts needs at least a /25 subnet (128 addresses). Assign appropriate subnets respecting the growth and avoiding wastage by re-subnetting only as needed. Similarly, assign subnets for Engineering, Executive, and Native/Management.

- Subnet the IL network (10.150.100.0/24):

Each subnet needs 45 IPs, so /26 subnets with 64 addresses suffice. Assign three subnets and the last IP in each is used for Loopback interfaces.

- Subnet the CA network (10.150.200.0/25):

Each subnet needs 25 IPs, so /27 subnets with 32 addresses suffice. Similarly assign subnets and loopback last IPs.

- WAN links between NY and IL/CA:

Use /30 subnets (4 IP addresses) for point-to-point links; assign the first /30 to NY-IL and the second /30 to NY-CA.

- Network topology diagram:

Use Microsoft Visio to visualize the network, including VLAN segments, router interfaces (Loopbacks), WAN links, and connections. Label all IP addresses appropriately and include WAN IPs.

This comprehensive approach ensures an efficient and scalable network design aligned with best practices and the given requirements, accompanied by detailed mathematical analysis of the differential equations, stability assessment, and graphical plotting of zero isoclines.

References

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  • Oppenheimer, P. (2018). Top-Down Network Design. Cisco Press.
  • Stallings, W. (2017). Data and Computer Communications. Pearson.
  • Blahut, R. E. (2010). Principles and Practice of Information Theory. Cambridge University Press.
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