Question

The Unix utility ping can be used to find the RTT to various Internet hosts. Read the man page for ping, and use it to find the RTT to www.cs.princeton.edu in New Jersey and www.cisco.com in California. Measure the RTT values at different times of day, and compare the results. What do you think accounts for the differences?

Short answer

Use 'ping' to measure RTT to both hosts at different times. Record, compare values, and consider factors like distance and network congestion.

Step-by-step solution

Understanding the Task

The task involves using the Unix utility 'ping' to measure the Round-Trip Time (RTT) to two different Internet hosts. The hosts are 'www.cs.princeton.edu' and 'www.cisco.com'.

Opening the Terminal

Open the terminal on your Unix-based system. This could be a Linux distribution, macOS, or any other Unix-like operating system.

Using the ping Command for the First Host

In the terminal, type the command `ping www.cs.princeton.edu` and press enter. Observe the RTT values that are displayed. Here’s an example command:```ping www.cs.princeton.edu```

Recording RTT for the First Host

Record the RTT values and the time of day when the ping command was executed. Repeat this at different times to observe any variations.

Using the ping Command for the Second Host

In the terminal, type the command `ping www.cisco.com` and press enter. Observe the RTT values that are displayed. Here’s an example command:```ping www.cisco.com```

Recording RTT for the Second Host

Record the RTT values and the time of day when the ping command was executed. Again, repeat this at different times to observe any variations.

Comparing RTT Values

Compare the RTT values recorded for 'www.cs.princeton.edu' and 'www.cisco.com' at different times of the day. Consider averages and ranges of RTT values.

Analyzing the Differences

Analyze the differences in RTT values. Factors that might account for these differences include geographical distance, network congestion, and varying traffic loads at different times of the day.

Key concepts

Unix utility ping

The Unix utility ping is a simple command-line tool used to test network connections. It helps in determining if a particular host is reachable over the network. When you run the ping command, your computer sends small data packets to the specified host. The host then sends these packets back to your computer. This helps you check the reachability and measure the time taken for the round trip. Ping is useful for diagnosing network issues and evaluating network performance.
Here’s how you can run the ping command on a Unix-based system:

• Open the terminal on your system.
• Type the command `ping` followed by the domain name or IP address of the target host.
• Press enter and observe the output.

For example, to ping `www.google.com`, you would type: `ping www.google.com` in the terminal.

Round-Trip Time (RTT)

Round-Trip Time (RTT) is a key metric in networking that measures the time taken for a signal to travel from the source to the destination and back again. In the context of the ping command, RTT is the time it takes for the ping data packet to go from your computer to the destination host and then return back to your computer.
RTT is important because:

• It helps in measuring the latency between two endpoints.
• It indicates the efficiency and speed of the network connection.
• Low RTT values suggest a faster and more efficient network.
• High RTT values may indicate network issues like congestion or long distance.

RTT is usually measured in milliseconds (ms). For instance, if the RTT for pinging `www.example.com` is 20ms, it means it takes 20 milliseconds for the data to complete the round trip.

Network Performance Analysis

Network performance analysis involves assessing various metrics like RTT to determine the quality and efficiency of a network. By using tools like `ping`, you can understand different aspects of network performance, including:

• Latency: The delay before a transfer of data begins following an instruction.
• Packet Loss: When data packets fail to reach their destination.
• Throughput: The rate at which data is successfully transferred from one place to another.

By regularly pinging different hosts, you can create a profile of your network’s performance. This helps in identifying bottlenecks and making informed decisions to improve the network. For example, high latency might prompt you to investigate network congestion or physical distance between nodes.

Internet Hosts Measurement

Measuring the performance to various Internet hosts, such as servers or websites, is crucial for understanding network reliability and speed. Using `ping`, you can determine how quickly and reliably data is sent and received from different locations. Here’s how to measure performance:

• Choose a few target hosts (e.g., `www.cs.princeton.edu` and `www.cisco.com`).
• Run the `ping` command for each host at different times of the day.
• Record the RTT values and observe any variations.

Comparing these values helps you understand how different factors like geographical distance and network traffic affect performance. For instance, `www.cs.princeton.edu` might have a lower RTT if you are closer to New Jersey, compared to `www.cisco.com` in California.

Network Congestion

Network congestion occurs when a network node is overloaded with data traffic, leading to delays and packet loss. It can significantly impact RTT and overall network performance. Congestion can happen due to several reasons:

• High volume of data traffic at peak times.
• Insufficient bandwidth.
• Inefficient network routing.

When you measure RTT at different times of the day, you may notice higher RTT values during peak hours when the network is congested. To deal with network congestion, you might need to upgrade the network infrastructure, optimize traffic routes, or implement traffic management policies. Understanding congestion helps in maintaining a smooth and efficient network.