Course: EE407
Name: Zachary Rauen
Number: 36
Assignment: 5
R1. List five nonproprietary Internet applications and the application-layerprotocols that they use.
- E-mail - SMTP
- Website/Forum - HTTP
- Remote access – Telnet
- Media Steam - HTTP
- File Transfer - FTP
R5. What information is used by a process running on one host to identify aprocess running on another host?
IP Addresses and port numbers for source and destination.
R19. Is it possible for an organization’s Web server and mail server to have exactlythe same alias for a hostname (for example, foo.com )? What would be thetype for the RR that contains the hostname of the mail server?
Yes they can have the same alias, they just use different ports. The type would be MX pointing to the IP address of the server.
P4. Consider the following string of ASCII characters that were captured byWireshark when the browser sent an HTTP GET message (i.e., this is the actualcontent of an HTTP GET message). The characters <cr<lf> are carriagereturn and line-feed characters (that is, the italized character string <cr inthe text below represents the single carriage-return character that was containedat that point in the HTTP header). Answer the following questions,indicating where in the HTTP GET message below you find the answer.
GET /cs453/index.html HTTP/1.1<cr<lf> Host: gaia.cs.umass.edu<cr<lf> User-Agent: Mozilla/5.0 (Windows;U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax) <cr<lf> Accept:ext/xml, application/xml, application/xhtml+xml, text/html;q=0.9, text/plain;q=0.8,image/png,*/*;q=0.5<cr<lf> Accept-Language: en-us,en;q=0.5<cr<lf> Accept-Encoding: zip,deflatecr<lf> Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7<cr<lf> Keep-Alive: 300<cr<lf> Connection:keep-alivecr<lf<cr<lf>
- What is the URL of the document requested by the browser?
Gaia.cs.umass.edu/cs453/index.html from GET and HOST
- What version of HTTP is the browser running?
http version 1.1 from the GET message
- Does the browser request a non-persistent or a persistent connection?
Persistent because it tells the connection to keep-alive from “Connection: keep-alive”
- What is the IP address of the host on which the browser is running?
Localhost? (I don’t see any IP addresses above)
- What type of browser initiates this message? Why is the browser typeneeded in an HTTP request message?
Mozilla was the browser. This is used by web developers to make sure their website is displayed properly in all browsers. They can change the style accordingly.
P7. Suppose within your Web browser you click on a link to obtain a Web page.The IP address for the associated URL is not cached in your local host, so aDNS lookup is necessary to obtain the IP address. Suppose that n DNSservers are visited before your host receives the IP address from DNS; thesuccessive visits incur an RTT of RTT1 , . . ., RTTn . Further suppose that theWeb page associated with the link contains exactly one object,consisting of asmall amount of HTML text. Let RTT0 denote the RTT between the local hostand the server containing the object. Assuming zero transmission time of theobject, how much time elapses from when the client clicks on the link untilthe client receives the object?
RTT0*2+RTT1+RTT2+…RTTn. (RTT0 *2) to go there and back
P20. Suppose you can access the caches in the local DNS servers of your department.Can you propose a way to roughly determine the Web servers (outside yourdepartment) that are most popular among the users in your department? Explain.
If you continually check the DNS cache, then you can see which web servers are accessed. The one that comes up the most is the most popular
P21. Suppose that your department has a local DNS server for all computers in thedepartment. You are an ordinary user (i.e., not a network/system administrator).Can you determine if an external Web site was likely accessed from acomputer in your department a couple of seconds ago? Explain.
Yes you can. You can send a query to the local DNS server and view the cache. Recently visited sites are stored in the cache.