1. What is the difference between MAIL FROM: in SMTP and From: in the mail message itself? (10 pts) 2. Suppose you wanted to do a transaction from a remote client to a server as fast as possible. Would you use UDP or TCP? Why? (15 pts) 3. In BitTorrent, suppose Alice provides chunks to Bob throughout a 30-second interval. Will Bob necessarily return the favor and provide chunks to Alice in this same interval? Why or why not? (10 pts) 4. Web caching has the ability to reduce the delay in receiving a requested object. Why? Web caching has the ability to reduce the delay for all objects requested by a user or for only some of the objects? Why? (15 pts) 5. From a user's perspective, what is the difference between the download-and-delete mode and the download-and-keep mode in POP3? (10 pts) 6. Is it possible that an organization's Web server and mail server have exactly the same alias for a hostname (e.g., kdd.com)? What would be the type for the RR that contains the hostname of the mail server? (10 pts) 7. Fill in the table based on the following HTTP GET message captured by Wireshark: (25 pts) GET /cs453/index.html HTTP/1.1Host: gai a.cs.umass.eduUser-Agent: Mozilla/5.0 ( Windows;U; Windows NT 5.1; en-US; rv:1.7.2) Gec ko/20040804 Netscape/7.2 (ax) Accept:ex t/xml, application/xml, application/xhtml+xml, text /html;q=0.9, text/plain;q=0.8, image/png,*/*;q=0.5 Accept-Language: en-us, en;q=0.5Accept- Encoding: zip,deflateAccept-charset: ISO -8859-1, utf-8;q=0.7,*;q=0.7Keep-Alive: 300 Connection: keep-alive Answer Question URL of the document requested by the browser: HTTP version: non-persistent or persistent connection: Browser type: The purpose of the browser type in an HTTP request message