Ping and traceroute

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Ping and traceroute

• Lab/Homework exercise
• Assigned 9/12/2006
• Due 9/19/2006
• CSIT 220 Fall, 2006Based on T. Blum Exercises

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Exercise/Assignment

• Assigned 9/12/2006
• We will be doing parts of this exercise in class.
  
• Some parts will require outside research and
  reference.
• You need to submit the results of this exercise
  in a hardcopy format.
• The lab exercise is due 9/19/2006. It will count
  as a homework grade.

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Pinging

• Ping is short for Packet Internet Groper
• It is a utility that sends a message to a
  computer and waits for a response
• A utility is part of system software that is used
  to help manage the computers resources, as
  opposed to application software
• If the response is received, information about
  the times required and so on are reported
• If the response is not received in a certain
  amount of time, the request is said to have
  timed out

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Pinging (Cont.)

• It works by sending special packets ICMP
  (Internet Control Message Protocol) echo request
  and echo reply packets to a destination, an IP
  address or domain name
• If the destination responds, you have a good
  TCP/IP connection (working route).
• There are many freeware and shareware PING
  utilities available for personal computers (see
  for example http//www.shareware.com)

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Breaking it down

• Pinging consists of the command ping followed
  by an IP address or domain name
• ping 139.84.10.250
• ping www.lasalle.edu
• It sends out special packets which request a
  response (echo reply) if the destination host is
  reached

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host

• A computer that is connected to a TCP/IP network,
  including the Internet.
• Each host has a unique IP address.
• A computer may always have the same address or
  may have a different address each time it
  connects to the networks
• Two computers on the same network or internet at
  the same time should not have the same address

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Usual form

• Instead of writing out a string of thirty-two 1s
  and 0s, IP addresses are usually written as four
  numbers between 0 and 255 separated by periods
  (the dotted decimal notation)
• For example
• 139.84.10.250

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How many?

• With 32 bits, 232 devices could be distinguished
• Actually the number of valid IP addresses is less
  than 232 because certain addresses are reserved
  for special purposes (127.0.0.1 is one example
  well see later)
• Another problem is that addresses are owned by
  people not using them

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IP Address (cont.)

• In an isolated network, any set of IP addresses
  can be assigned.
• On the other hand, connecting a network to the
  Internet requires using registered IP addresses
  to avoid duplications.
• The InterNIC Registration Service assigns
  Internet addresses.

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Domain name

• A domain name is a string of characters standing
  in for an IP address
• Can have
• One Name ? Multiple Addresses
• One Address ? Multiple Names
• Domain names are used in URLs to identify
  particular Web pages. For example, in the URL
  http//www.pcwebopedia.com/index.html, the domain
  name is pcwebopedia.com.

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Packet

• A packet is a message (protocol some data) or
  a piece of a message transmitted over a
  packet-switching network.
• A packet must also contain an address
  (identifier) so that it can be routed to its
  destination.

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Packet switching

• A set of protocols (rules for communication) in
  which messages are broken into pieces called
  packets before being sent.
• The packets are transmitted individually
  (connectionless).
• They may follow different routes
• They can arrive out of order
• Share the medium with other packets from other
  transmissions
• When the packets arrive, they are reassembled
  into the original message.

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Pinging Start/Run
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Pinging Type command in Run dialog box
Actually cmd is preferred
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Pinging type ping followed by domain name
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Pinging a host which was off at the time
Timed out
Can use IP instead of domain name
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Pinging webopedia, also timed out
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Webopedia ping timed out, even though site was up
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Denial of service

• One possibility is that some companies block
  pings because their systems could become clogged
  with ping requests.
• Rejecting pings could make a site less vulnerable
  to a Denial of Service (DoS) attack, in which a
  site is flooded with so many requests that it
  cannot answer them all.

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Ping Exercise Part 1 (30 points)

• Pick the address of a site you visit. You are
  going to use it to test some network diagnostics.
  What happened when you ping your site?
• Try it with a few more examples. What is
  happening?
• How can ping be useful?

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Type ping /? To find the various options there
are
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Using the count request option to send 5 instead
of 4
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Useful or not?

• Simply pinging a remote host (a computer that is
  on ones internet but not on ones network)
  usually has an all or nothing outcome and as such
  can provide somewhat limited information
• A sequence of pinging can provide more
  information (see MCSE TCP/IP for Dummies)

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Pinging yourself using localhost or 127.0.0.1
verifies that TCP/IP has been installed and
started correctly
Reserved IP address
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Pinging yourself using your IP, checks that the
IP is valid
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You can use another utility ipconfig to find your
IP if you dont know it
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• Go to the start command
• Select the option run and type
• command.com
• You now have the black window and we are going to
  use this to check our connection.
• Run ipconfigwhat is your address? What can you
  tell from your about your connection?

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Pinging the Gateway timing out here may
indicate a problem with the router
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Gateway

• Recall that one gets an internet by connecting
  more networks
• The point at which data leaves one (local)
  network and enters another is known as a gateway
  
• A node (a device on the Internet) can be either a
  gateway, router, or a host (end-point).

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Host/Gateway

• When you are looking at some site on the net,
  your computer and the one containing the site are
  hosts
• On the other hand, the computers that direct the
  traffic, for example your Internet service
  provider (ISP) are gateway/router nodes.

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Traceroute

• A utility that traces (determines the route taken
  by) a packet from your computer (the local host)
  to some other host on the network
• It doesnt actually follow a single packet but
  sends out a series of packets
• The packets are restricted in the number of
  hops they can take
• It is limited by the time-to-live (TTL) field
• When the limit is reached, information about the
  node is (should be) returned
• Each consecutive packet is allowed one more hop
  

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hop

• A hop is when a packet is transmitted from one
  node to the next.
• Some Internet Service Providers (ISPs) advertise
  how many hops away from Internet backbone they
  are. Theoretically, the fewer hops it takes to
  get your data onto the backbone, the faster your
  access will be. (webopedia)

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Traceroute (Cont.)

• Traceroute shows how many hops were required to
  reach the destination as well as the length of
  time for each hop.
• When the web is sluggish, you can use traceroute
  to determine where the congestion lies.

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Traceroute (Cont.)

• The original traceroute was for UNIX utility
• Windows has a traceroute utility called tracert.
• Go to Start/Run, type cmd, and then type
  tracert followed by the domain name of the
  host.
• For example
• tracert www.webopedia.com

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tracert www.whatis.com
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Tracert Exercise Part 2 (40 points)

• Using the command.com and tracert command, find
  the command to
• www.whatis.com
• 139.84.19.200
• Ask your neighbor for their ip addresstrace the
  route to them.

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Other TCP/IP diagnostic commands

• Nbtstat
• Netstat
• Ipconfig
• Arp
• Hostname
• Route
• Look up these commands and see what they mean.
  Prepare a table with the list and the job of each
  command.site your sources.

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Another Exercise part 3 (30 points)

• Find the ipconfig for your machine.
• Open the command window
• Look at the options for the NBTSTAT command.
• Run the NBTSTAT command using your ip address for
  your machine. Use the A option. What did you
  find out?

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Other sources

• http//www.webopedia.com
• http//www.whatis.com