Communications and Networking

Running head: COMMUNICATIONS AND NETWORKING
Communications and Networking
Student Name
University Name
Note by the Author

COMMUNICATIONS AND NETWORKING1
Summary
This report aims to record and study the pinging, and tracing activities of three different
websites located in a different continent (Europe and North America) than the place from
where the network analysis is being conducted that is Asia. First the report performs a ping of
the website www.ece.ust.eu and discusses the IP address and ports of the source and
destination hosts as well as goes in depth into the protocol contents of ping request and reply
packets. Then the trace of another website www.inria.fr is conducted and thorough research
on ICMP packets and their comparison with that of the ping are made before finding the link
with the longest delay. Thereafter, a trace is performed on gaia.cs.umass.edu is performed in
PingPlotter to get a more comprehensive look at the nearest first hop routers, their location as
also the graph of the latencies of each step. This is a composite process conducted for three
different packet sizes (56 bytes, 2000 bytes, 3500 bytes). Here, the contents of the IP protocol
get further analysed and it is checked if datagrams got fragmented and also details and
comparison of the identified fragments for different packet sizes are performed after which
the report ends with concluding notes.

COMMUNICATIONS AND NETWORKING2
Table of Contents
Introduction................................................................................................................................5
Analysis of Traces......................................................................................................................5
Part A: Ping of website of another continent.........................................................................5
1. IP addresses of local host and that of destination host...................................................8
2. Reason for ICMP packets not having source port or destination port numbers.............8
3. Examining a ping request packet sent by local host (ICMP Type, Code numbers and
rest of the fields, number of bytes for checksum, sequence number and identifier fields)9
4. Examining a ping request packet sent by local host (ICMP Type, Code numbers and
rest of the fields, number of bytes for checksum, sequence number and identifier fields)
..........................................................................................................................................10
Part B: Trace route...............................................................................................................11
5. IP addresses of local host and that of destination host.................................................13
6. IP Protocol number if system was Linux or UNIX based and ICMP sent UDP
packets..............................................................................................................................13
7. Examining ICMP echo packet and whether it is different from ICMP ping query
packets..............................................................................................................................14
8. Examining contents of ICMP error packets which have more fields than ICMP echo
packets..............................................................................................................................15
9. Examining last 3 ICMP packets...................................................................................16
10. Link among tracert measurements where delay is significantly longer than the rest 17
Part C: Trace with PingPlotter and Latency Graph..............................................................17

COMMUNICATIONS AND NETWORKING3
1. Select the first ICMP Echo Request message sent by your computer, and expand the
Internet Protocol part of the packet in the packet details window. What is the IP address
of your computer?............................................................................................................25
2. Within the IP packet header, what is the value in the upper layer protocol field?.......26
3. How many bytes are in the IP header? How many bytes are in the payload of the IP
datagram? Explain how you determined the number of payload bytes...........................26
4. Has this IP datagram been fragmented? Explain how you determined whether or not
the datagram has been fragmented...................................................................................27
5. Which fields in the IP datagram always change from one datagram to the next within
this series of ICMP messages sent by your computer?....................................................29
6. Which fields stay constant? Which of the fields must stay constant? Which fields must
change? Why?..................................................................................................................30
7. Describe the pattern you see in the values in the Identification field of the IP datagram
..........................................................................................................................................30
8. What is the value in the Identification field and the TTL field?..................................31
9. Do these values remain unchanged for all of the ICMP TTL-exceeded replies sent to
your computer by the nearest (first hop) router? Why?...................................................34
10. Find the first ICMP Echo Request message that was sent by your computer after you
changed the Packet Size in pingplotter to be 2000. Has that message been fragmented
across more than one IP datagram?..................................................................................35
11. Print out the first fragment of the fragmented IP datagram. What information in the
IP header indicates that the datagram been fragmented? What information in the IP

COMMUNICATIONS AND NETWORKING4
header indicates whether this is the first fragment versus a latter fragment? How long is
this IP datagram?..............................................................................................................36
12. Print out the second fragment of the fragmented IP datagram. What information in
the IP header indicates that this is not the first datagram fragment? Are the more
fragments? How can you tell?..........................................................................................38
13. What fields change in the IP header between the first and second fragment?...........39
14. How many fragments were created from the original datagram?..............................40
15. What fields change in the IP header among the fragments?......................................41
Conclusion................................................................................................................................41
Bibliography.............................................................................................................................42

COMMUNICATIONS AND NETWORKING5
Introduction
The following report records and studies the ping, and traceroute activities of three
different websites located in different continents (Europe and North America) than the place
from where the network analysis is being conducted that is Asia. The report begins by
performing a ping of the website www.ece.ust.eu and discusses the IP address and ports of
the source and destination hosts as well as goes in depth into the protocol contents of ping
request and reply packets. Then the trace of another website www.inria.fr is conducted and
thorough research on ICMP packets and their comparison with that of the ping are made
before finding the link with the longest delay. Thereafter, a trace is performed on
gaia.cs.umass.edu is performed in PingPlotter to get a more comprehensive look at the
nearest first hop routers, their location as also the graph of the latencies of each step. This is a
composite process conducted for three different packet sizes (56 bytes, 2000 bytes, 3500
bytes). Here, the contents of the IP protocol get further analysed and it is checked if
datagrams got fragmented and also details and comparison of the identified fragments for
different packet sizes are performed after which the report ends with concluding notes.

COMMUNICATIONS AND NETWORKING6
Analysis of Traces
Part A: Ping of website of another continent
Figure 1: Selecting the network for recording
Wireshark is launched and the above window opens when clicked on capture options.
Here the Ethernet network is selected as that is the network interface through which the
system accesses the Internet. When clicked on Start, the recording begins.

COMMUNICATIONS AND NETWORKING7
Figure 2: Pinging website of another continent
The Windows command prompt is opened and the website www.ece.ust.eu is being
traced as the tracing activity is being conducted from Asia and because the website to be
pinged has to be from a different continent.
Figure 3: Complete ping of website
The pinging activity completes with 10 packets being sent and all of them getting
received successfully.