FIN 4453 – PROJECT 2 Fall 2024

Java Python FIN 4453 – PROJECT 2 (10 Questions)

Fall 2024

1. (15 Points) Use the Excel file Asset Allocation Data to determine the following:

a. Using EXCEL’s Data Table Feature, create a one-way data table that determines the different means and standard deviations for combinations of Portfolio 1 and Portfolio 2 by varying the proportion of Portfolio 1.

b. Graph the combinations of the portfolios from the one-way data table and add the individual asset means and standard deviations to the graph.

c. Using EXCEL’s Text Box feature, explain why the envelope portfolios may or may not be on the efficient frontier?

d. Using Solver or Goal Seek, find an envelope portfolio that would yield an expected return of 4.75%.  What would be the corresponding portfolio standard deviation?

e. Using Solver or Goal Seek, find two envelope portfolios that would yield a standard deviation of 6.25%.  What would be the corresponding expected returns for each of these portfolios?

f. Using Solver, find the envelope portfolio that would yield the smallest (minimum) standard deviation.  What would be the corresponding expected return and standard deviation for this portfolio?

2. (10 Points) Use the Excel file Data for Two Stocks to determine the following:

a. Using EXCEL’s Data Table Feature, create a one-way data table that determines the different means and standard deviations for portfolios consisting of combinations of Stock A and Stock B by varying the correlation coefficient value between Stock A and Stock B through the full range of possible correlation coefficient values.  Use increments of 0.125 for the possible correlation coefficient values.

b. Graph the correlation coefficients, the means, and the standard deviations of the portfolios from the one-way data table.  Be sure to include a title for the graph and label the axes.

c. Use Excel’s Text Box Feature to explain how the portfolio means are affected by changing the correlation coefficient values.

d. Use Excel’s Text Box Feature to explain how the portfolio standard deviations are affected by changing the correlation coefficient values.

3. (10 Points) Use the Variance – Covariance matrix in the Excel file: Efficient Portfolios Data.

Construct a model to determine the following:

a. Calculate an envelope portfolio assuming the risk-free rate is 2%.

b. Calculate an envelope portfolio assuming the risk-free rate is 16%.

c. Using EXCEL’s Data Table Feature, create a one-way data table that determines the different means and standard deviations for combinations of Envelope Portfolio 1 and Envelope Portfolio 2 by varying the proportion of Portfolio 1 from -10 to +10 in increments of 1.00.

d. Graph the combinations of the portfolios from the one-way data table and add the individual asset means and standard deviations to the graph.

e. Provide a title on the graph FIN 4453 – PROJECT 2 Fall 2024 and label the axes of the graph.

f. Using EXCEL’s Text Box feature, explain whether the portfolio combinations could be on the efficient frontier.

4. (15 Points) The Excel file Stock Data contains monthly return data for seven (7) stocks.

a. Use these returns and the Matrix of Excess Returns to compute the Variance-Covariance Matrix for these seven (7) stocks. (Do not use the varcovar VBA function).

b. Use the Variance - Covariance Matrix for these seven (7) stocks to compute the individual stock proportions for the Global Minimum Variance Portfolio (GMVP).

c. Calculate the Expected Return and Risk (Standard Deviation) for the Global Minimum Variance Portfolio (GMVP).

5. (10 Points) The Excel file Stock Data contains monthly return data for seven (7) stocks.

a. Compute the Correlation Matrix for the seven (7) stocks.

b. Using EXCEL’s Text Box feature explain/identify

i. The characteristics of the Correlation Matrix.

ii. What the correlation coefficient measures.

iii. How the correlation coefficient values are used in portfolio theory, i.e., the role of the correlation coefficient in portfolio theory.

6. (8 Points) Provide Benninga’s definitions for the following:

a. Envelope Portfolio

b. Efficient Portfolio

c. Feasible Portfolio

d. Infeasible Portfolio

7. (8 Points) Solve the following system of equations using Matrix Algebra.

3A + 5B – 4D + 6E = 80

6A + 4B + 8C – 3D + 2E = 70

7A – 6C + 2D + 3E = 60

6A – 5B + 4D + 2E = 50

4A + 9B + 3D – 4E = 40

8. (8 Points) The Excel file Portfolio Weights Data contains information about two portfolios.

a. Using Matrix Algebra compute the portfolio asset weights for Portfolio C if Portfolio C has 42% of its funds invested in Portfolio A and 58% of its funds invested in Portfolio B.

b. Using EXCEL’s Data Table Feature, create a one-way data table to compute the Portfolio C asset weights by varying the proportion of funds invested in Portfolio A from 0 to +1.0 in increments of 0.125.  Portfolio C will consist of the appropriate proportion of funds invested in Portfolio A and the remainder of the funds invested in Portfolio B.

9. (8 Points) Describe the characteristics of a variance-covariance matrix.  Also, explain how to read a variance-covariance matrix, what the individual values in a variance-covariance matrix represent, what the individual values in a variance-covariance matrix measure, and how the variance-covariance matrix is used.  Use EXCEL’s Text Box feature when you input your response.

10. (8 Points) The EXCEL file Stock Return Probability Distribution contains the probability distribution for a stock.

a. Compute the Expected Return for this stock.

b. Compute the Risk for this stock         

<think>好的,用户现在问的是关于TCP连接状态中的FIN_WAIT2状态。我需要先回忆一下TCP协议的四次挥手过程,确保自己对FIN_WAIT1和FIN_WAIT2的理解正确。用户可能是在网络问题排查中遇到了这个状态,想了解它的含义以及如何处理相关的问题。 首先,用户可能想知道FIN_WAIT2是什么,属于TCP连接的哪个阶段。根据四次挥手的流程,主动关闭的一方在发送第一个FIN后会进入FIN_WAIT1,当收到对方的ACK后进入FIN_WAIT2。这时候等待对方发送FIN,然后自己回复ACK进入TIME_WAIT。所以FIN_WAIT2是主动关闭方在等待对方关闭连接的状态。 接下来,用户可能关心为什么连接会长时间停留在FIN_WAIT2。常见原因包括对方未发送FIN,或者应用层没有正确处理关闭流程。比如对方可能因为代码问题没有正确关闭连接,或者网络问题导致FIN丢失。 然后,用户可能需要知道如何检测和解决这个问题。需要检查系统上的网络状态,使用netstat或ss命令查看连接状态。如果大量连接卡在FIN_WAIT2,可能需要调整内核参数,比如调整tcp_fin_timeout来缩短等待时间,或者检查应用程序是否正确关闭连接。 另外,用户可能对FIN_WAIT2和TIME_WAIT的区别有疑问,需要解释两者的不同阶段和持续时间。还要提到如果被动关闭方一直不发送FIN,可能导致资源耗尽,所以需要监控和及时处理。 最后,用户可能希望了解如何避免这种情况,比如优化应用代码,确保连接正确关闭,或者调整系统参数。需要给出具体的命令示例,如查看状态的命令和修改内核参数的方法,帮助用户实际操作。 需要确保回答结构清晰,分点说明,结合技术细节和实际例子,让用户能够逐步理解问题并找到解决方法。同时要注意使用中文,避免专业术语过于晦涩,必要时进行解释。</think>--- ### FIN_WAIT2 状态详解 --- #### **一、基本定义** **FIN_WAIT2** 是 TCP 协议连接关闭过程中的一个中间状态,属于**主动关闭方**(主动发送 `FIN` 报文的一端)的状态变迁环节。 其触发条件为: 1. 主动关闭方发送 `FIN` 报文后进入 `FIN_WAIT1` 状态 2. 收到被动关闭方的 `ACK` 响应(非 `FIN`)时,转为 `FIN_WAIT2` 状态 此时 TCP 连接的半关闭特性生效: - 主动关闭方**不再发送数据**,但仍可**接收数据** - 等待被动关闭方发送最终的 `FIN` 报文 --- #### **二、状态流程图解** ```plaintext 主动关闭方 被动关闭方 |-------- FIN (seq=x) -------->| → 进入 CLOSE_WAIT |<------- ACK (x+1) -----------| (发送ACK) (进入 FIN_WAIT1) | |<------- FIN (seq=y) ---------| → 进入 LAST_ACK |-------- ACK (y+1) ---------->| (收到ACK后关闭) (进入 TIME_WAIT) (连接关闭) ``` --- #### **三、关键特性与问题** 1. **持续时间** - 默认由内核参数 `tcp_fin_timeout` 控制(Linux 默认 $60$ 秒) - 超时后主动关闭方强制终止连接 2. **常见异常场景** - **长时间滞留**:被动关闭方未发送 `FIN`(代码未调用 `close()` 或进程崩溃) - **资源占用**:每个 `FIN_WAIT2` 连接占用文件描述符和内存(可通过 `ss -ant | grep FIN-WAIT-2` 监控) 3. **与 TIME_WAIT 的对比** | 状态 | 触发阶段 | 持续时间 | 资源释放优先级 | |--------------|--------------------------|----------------|----------------| | `FIN_WAIT2` | 等待对方 FIN | 60秒(可配置) | 中 | | `TIME_WAIT` | 确保对方收到最终 ACK | 2MSL(约1-4分钟) | 低 | --- #### **四、问题排查与优化** 1. **检测命令** ```bash # Linux 查看 FIN_WAIT2 连接数 netstat -n | awk '/FIN_WAIT2/{count++} END{print "FIN_WAIT2 connections:", count}' # 或使用 ss 命令(更高效) ss -ant state fin-wait-2 ``` 2. **内核参数调优** ```bash # 缩短 FIN_WAIT2 超时时间(例:30秒) echo 30 > /proc/sys/net/ipv4/tcp_fin_timeout # 持久化配置(/etc/sysctl.conf) net.ipv4.tcp_fin_timeout = 30 ``` 3. **应用层修复** - 确保被动关闭方正确处理连接关闭(如 Java 需检查 `Socket.close()` 调用) - 添加连接空闲超时机制(如 Nginx 配置 `keepalive_timeout`) --- #### **五、典型案例分析** **案例**:Web服务器大量 `FIN_WAIT2` 连接 - **现象**:负载均衡器监测到 $800+$ 个 `FIN_WAIT2` 连接 - **根因**:客户端(移动APP)未正确处理 TLS 连接关闭,$60\%$ 请求未发送 `FIN` - **解决方案**: 1. 调整 `tcp_fin_timeout` 至 $20$ 秒 2. 客户端增加心跳包机制 3. 服务端配置 `SO_LINGER` 选项加速关闭 --- ### 注意事项 - **勿盲目调整参数**:过度缩短 `tcp_fin_timeout` 可能导致合法连接异常中断 - **结合日志分析**:需配合 `tcpdump` 抓包(过滤条件 `tcp[tcpflags] & (tcp-fin) != 0`)确认 FIN 交互完整性 - **容器环境差异**:Kubernetes 等容器网络可能修改默认 TCP 行为,需检查 CNI 插件配置
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