Title: Ping and traceroute
1Ping and traceroute
- Lab/Homework exercise
- Assigned 9/12/2006
- Due 9/19/2006
- CSIT 220 Fall, 2006Based on T. Blum Exercises
2Exercise/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.
3Pinging
- 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
4Pinging (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)
5Breaking 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
6host
- 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
7Usual 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
8How 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
9IP 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.
10Domain 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.
11Packet
- 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. -
12Packet 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.
13Pinging Start/Run
14Pinging Type command in Run dialog box
Actually cmd is preferred
15Pinging type ping followed by domain name
16Pinging a host which was off at the time
Timed out
Can use IP instead of domain name
17Pinging webopedia, also timed out
18Webopedia ping timed out, even though site was up
19Denial 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.
20Ping 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?
21Type ping /? To find the various options there
are
22Using the count request option to send 5 instead
of 4
23Useful 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)
24Pinging yourself using localhost or 127.0.0.1
verifies that TCP/IP has been installed and
started correctly
Reserved IP address
25Pinging yourself using your IP, checks that the
IP is valid
26You can use another utility ipconfig to find your
IP if you dont know it
27 - 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?
28Pinging the Gateway timing out here may
indicate a problem with the router
29Gateway
- 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).
30Host/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.
31Traceroute
- 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
32hop
- 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)
33Traceroute (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.
34Traceroute (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
35tracert www.whatis.com
36Tracert 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.
37Other 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.
38Another 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?
39Other sources
- http//www.webopedia.com
- http//www.whatis.com