Before we start i should mention that all these

Info icon This preview shows pages 63–64. Sign up to view the full content.

View Full Document Right Arrow Icon
Before we start, I should mention that all these utilities are called command line utilities. This means they are run from within the command line and not the graphical interface of the operating system. Ping 0:32-2:15 The first utility that we're going to look at is ping. Ping is used to test whether or not a particular host on a TCPIP network is reachable. If the ping succeeds then you know two things. First the other host is up and running and second, that the network connection between the two hosts is functioning properly. Ping works by sending out what's called an ICMP echo request packet to the target host. When the host receives the echo request it replies with an echo response. The nice thing about ping, is it can also be used to test the latency between two hosts. This is because the sending host tracks the time it takes in milliseconds to receive the echo response from the target host. Ping also tracks packet loss.This is useful for several reasons. Let's say you ping a host on a network and the time it takes to receive the echo response is really long. Not only that, but only half of the ping requests make it to the other host, the rest are lost. What this tells you is that there is a problem on the network between the two hosts. Which might be a bad cable or a faulty network card. Ping does have some limitations however. For example, a failed ping request doesn't always mean the target host is down. Some host based firewalls such as the one included with the Windows operating system are designed to ignore ICMP requests. Some routers also are designed to ignore ICMP requests. The reason for this is to protect againstdenial of service attacks, or DOS attacks. A DOS attack attempts to bring down a target system by flooding it with thousands of ICMP responses in just a few seconds. To prevent this attack firewalls and routers simply ignore all ICMP traffic. If you want to be able to ping these systems on the network, it is possible to configure firewalls and routers to permit ICMP traffic. Tracert/Traceroute 2:16-3:51 The next TCPIP utility we'll look at is called traceroute. On Windows systems this utility uses the tracert command and Linux and Mac OS the traceroute command is used. Traceroute is similar to the ping utility and that it also uses ICMP echo requests and reply packets, to test network connectivity. However, traceroute does this in a way that is a little bit different. What traceroute is track each router that packets pass through in order to reach the destination host.Using traceroute within a network isn't very helpful since the packets probably won't go through any routers. Where traceroute shines, is when using it to test a connection on another network. For example, let's say we use the traceroute utility from a host on the west coast and we are contacting a host on the east coast here. By using traceroute we can see each router that the packet uses to reach the target system. Because of the way TCPIP works, we might not use the same routers each time. We might not even use the same number of routers. It's possible that one traceroute uses four routers and the next traceroute
Image of page 63

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 64
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern