Pinging Around the World

Answer and discuss the following questions with a partner:

  • What does HTTP stand for?
  • Which protocol is used to resolve a domain name to an IP address?
  • How do clients compare to hosts?
  • Compare different HTTP status codes.
  • Draw your own diagram of a request/response cycle and label where the following would come into play: client, host/server, URL, client-side languages, server-side languages, data
  • T/F: HTTP headers can be changed by a user before executing a request.
  • T/F: Every HTTP request has a domain and a path.
  • T/F: Email uses the HTTP Protocol.

Use the ping command to see how long it takes for servers to respond to your computer:

All requests sent from your computer must travel across the internet, going through various servers, in order to make the delivery. Using the ping command in the terminal window, try to find servers that respond quickly, and find some that take longer to respond. Hit CTRL + C if you need to exit ping. What are the fastest and slowest sites you can ping?

University servers are usually hosted on their actual campuses. Use university servers to estimate how long it takes requests to travel around the world. Look up the distance between cities and calculate kilometers / time in milliseconds to calculate how fast these requests travel.

# Less than 10 km away from GA Singapore campus
ping www.nus.edu.sg
National University of Singapore
PING www.nus.edu.sg (137.132.21.27): 56 data bytes
64 bytes from 137.132.21.27: icmp_seq=0 ttl=42 time=5.442 ms
64 bytes from 137.132.21.27: icmp_seq=1 ttl=42 time=6.124 ms
64 bytes from 137.132.21.27: icmp_seq=2 ttl=42 time=5.114 ms
^C
--- www.nus.edu.sg ping statistics ---
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 5.114/5.560/6.124/0.421 ms
University of Washington in Seattle
PING washington.edu (128.95.155.135): 56 data bytes
64 bytes from 128.95.155.135: icmp_seq=0 ttl=45 time=306.515 ms
64 bytes from 128.95.155.135: icmp_seq=1 ttl=45 time=224.400 ms
64 bytes from 128.95.155.135: icmp_seq=2 ttl=45 time=207.356 ms
^C
--- washington.edu ping statistics ---
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 207.356/246.090/306.515/43.290 ms
Stanford University in California
PING stanford.edu (171.67.215.200): 56 data bytes
64 bytes from 171.67.215.200: icmp_seq=0 ttl=235 time=173.482 ms
64 bytes from 171.67.215.200: icmp_seq=1 ttl=235 time=201.556 ms
64 bytes from 171.67.215.200: icmp_seq=2 ttl=237 time=186.975 ms
^C
--- stanford.edu ping statistics ---
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 173.482/187.338/201.556/11.464 ms
Other World Wide Campuses

Try pinging these other campuses around the world.

$ ping www.u-tokyo.ac.jp # The University of Tokyo: 5,312 km from Singapore, in the other direction!
$ ping www.cam.ac.uk # Cambridge University in London: 10,841 km from Singapore
$ ping sydney.edu.au # The University of Sydney in Australia: 7,822 km from Singapore
$ ping www.hbc.ac.za # Helderberg College in Cape Town, South Africa: 9,661 km from Singapore
$ ping www.cs.nyu.edu # New York University: 15,323 km from Singapore
$ ping www.uce.edu.ec # Central University of Ecuador in South America: 19,774 km from Singapore
Mystery IP Address

Ping this specific IP address and see how long it takes the server to respond.

Google this IP to find out what makes it unique. Be sure to use the Google homepage. IP addresses are hard to quick-search from your browser's location bar! If you type in an IP address your browser will try to load it as if it were a web page!

ping 127.0.0.1

Experiment with the traceroute command to see how internet traffic flows between your computer and servers:

# the traceroute command will show which servers routed the traffic
traceroute washington.edu
Sample Output
$ traceroute www.nus.edu.sg 
traceroute to www.nus.edu.sg (137.132.21.27), 64 hops max, 52 byte packets
 1  192.168.85.1 (192.168.85.1)  1.738 ms  1.989 ms  1.157 ms
 2  bb118-200-215-254.singnet.com.sg (118.200.215.254)  3.496 ms  2.870 ms  2.928 ms
 3  202.166.120.58 (202.166.120.58)  4.530 ms  4.225 ms  4.371 ms
 4  202.166.120.57 (202.166.120.57)  2.599 ms  2.401 ms  2.406 ms
 5  xe-9-2-1.tp-ar11.singnet.com.sg (202.166.120.29)  58.050 ms  4.321 ms  2.436 ms
 6  ae8-0.tp-cr03.singnet.com.sg (202.166.122.50)  3.603 ms  6.846 ms  3.853 ms
 7  202.166.120.110 (202.166.120.110)  4.142 ms
    ae6-0.qt-cr03.singnet.com.sg (202.166.120.185)  68.517 ms
    202.166.120.110 (202.166.120.110)  4.784 ms
 8  ae12-0.qt-er05.singnet.com.sg (202.166.120.221)  6.161 ms  3.113 ms  4.599 ms
 9  202.166.126.114 (202.166.126.114)  3.183 ms  3.548 ms  3.916 ms
10  ten-4-1.sn-sintp1-au301.singnet.com.sg (165.21.12.44)  4.497 ms  4.706 ms  3.715 ms
11  118.201.215.82 (118.201.215.82)  4.548 ms  7.821 ms  4.359 ms
12  202.51.240.230 (202.51.240.230)  4.612 ms  23.792 ms  4.559 ms
13  nus-gw1.gigapop.nus.edu.sg (202.51.241.14)  5.183 ms  4.567 ms  4.835 ms
14  * * *
15  *^C

traceroute: Warning: washington.edu has multiple addresses; using 128.95.155.135
traceroute to washington.edu (128.95.155.135), 64 hops max, 52 byte packets
 1  10.1.4.1 (10.1.4.1)  2.372 ms  2.008 ms  1.976 ms
 2  209.63.143.50 (209.63.143.50)  4.526 ms  4.797 ms  4.356 ms
 3  209.63.101.2 (209.63.101.2)  6.384 ms  5.994 ms
    209.63.101.6 (209.63.101.6)  6.123 ms
 4  six.tr-cps.internet2.edu (206.81.80.77)  11.866 ms  5.300 ms  5.357 ms
 5  ae-1.80.rtr.seat.net.internet2.edu (64.57.20.212)  4.118 ms  6.208 ms  4.382 ms
 6  198.71.47.6 (198.71.47.6)  4.226 ms  6.278 ms  6.259 ms
 7  ae0--4000.icar-sttl1-1.infra.pnw-gigapop.net (209.124.188.132)  6.270 ms  9.782 ms  9.148 ms
 8  ae0--4000.uwbr-ads-1.infra.washington.edu (209.124.188.133)  8.508 ms  5.471 ms  5.914 ms
 9  * * *
10  * * * (ignore asterisks and press CTRL+C to quit)

Experiment with cURL and send requests to various web pages. Here are some

useful flags you can use:

Headers flag
# -I returns the response headers only
curl -I http://www.google.com
Sample Output
HTTP/1.1 200 OK
Date: Sun, 27 Sep 2015 02:28:12 GMT
Expires: -1
Cache-Control: private, max-age=0
Content-Type: text/html; charset=ISO-8859-1
...
Verbose mode
# -v is verbose mode and returns the entire request and response (along with some additional info)
curl -v http://www.google.com
Sample Output
* Rebuilt URL to: http://www.google.com/
*   Trying 2607:f8b0:400a:806::2004...
* Connected to www.google.com (2607:f8b0:400a:806::2004) port 80 (#0)
...

Using cURL and the -I flag, get the following response codes from some webpages:

  • 2xx - examples include 200 (OK), 201 (Created)
  • 3xx - examples include 301 (Moved permanently)
  • 4xx - examples include 400 (Bad request), 404 (Not found)

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