CS472 Computer NetworksWinter 2020-2021Homework Assignment # 1Due Date: Wednesday, January 20th, 2021 at 6:29pmNOTE: Assignments must be submitted in electronic format via Drexel Learn (pdf, doc, etc.).All of the work must be original, no team work. Late assignments WILL NOT be accepted.Please submit your assignment as your first initial and last name as a zip file (e.g. mine would bemkain_hw1.zip). PLEASE MAKE SURE THAT YOU ANSWER ALL PARTS OF THEQUESTIONS and in your own words!1. [25 points] Think about ordering food from a restaurant or pizza place or whatever (whatare the odds of that on a college campus?) Food Trucks also work here. Imagine theconversation between you and the clerk/waiter and answer the following questions: What do you think the “messages” are sent from the clerk/waiter to you, and what areyour responses? (messages could be in either direction) Do you start or him? Doesit matter? Try to think about how the conversation would go to start. Are there standard questions and answers? (e.g. “I’d like ten wings, two slices ofmushroom pizza, and a twelve-pack of OE 800”, “for here or to go?”) How does each side know when the other side is finished talking? Are there different states of the “conversation” (for example, a message in the“Greeting” state could be “Hello, Powelton Pizza”) between you and the clerk? Any assumptions made in your protocol? (for example, language, etc.) Is there any security present in this protocol? (verifying who you are, etc.). Does itmatter on other choices in the protocol? Do you think there is a STANDARD ordering protocol that could be used? Do youthink that DOORDASH or GRUBHUB would be able to have a protocol for this?What about a common protocol for all delivery services? Do you think that the conversation/protocol would be the same in the followingconfigurations: In person, over a phone, and from an app to their server? Is there anydata that you would be worried about if anyone else would hear it (and is it dependenton which way you’re talking with them?)Sketch out as many of the messages and responses (make sure that you include errormessages) of this protocol that you can.2. [25 points] Now abstract what you think exists in a protocol/conversation between acomputer and an update server (like Windows Update for your PC), assuming a reliableconnection (all messages are sent and received correctly). Answer the samequestions/bullet points as in question #1 and sketch out as many of the messages andresponses that you think would be present. Think about authentication and licensing aswell.3. [25 points] Download the free packet analyzer WireShark fromhttp://www.wireshark.org/ and install it on your PC/workstation. Capture packetsbetween your PC and the network (for example, when browsing to a website and one
other activity). Analyze the packets (submit screenshot of a web access (HTTP GET)and two other activities, like sending an email, IM and/or BitTorrent, video streaming)and show all of the layers decoded and match them to the TCP/IP model (try to showunencrypted traffic). How is the right computer module addressed at each layer? Howdoes one layer know which layer to give the information to next? Is there more than oneprotocol at any layer?Now capture packets of traffic that uses encryption (SSL, SSH, etc.) and analyze thepackets. What is encrypted and what isn’t? What can WireShark decode and what can’tit? Do you think WireShark should be able to decode the rest – and what would it need?Do you think that this could happen?4. [15 points] What is an RFC (and don’t just answer what’s in Wikipedia! Go past whatGoogle says – c’mon - REALLY what do they contain?) What does it have to do?Describe some of the major pieces of an RFC. Now think about what you’d need if youwere to implement a network protocol and discuss briefly what must be defined for anetwork protocol (look at some of the classic application layer protocols of the Internet).Think about this in the same context as the questions in Question 1.Some popular protocols:FTP: RFC 959 (https://www.rfc-editor.org/rfc/pdfrfc/rfc959.txt.pdf)DNS: RFC 1034 (https://www.rfc-editor.org/rfc/pdfrfc/rfc1034.txt.pdf)TLS 1.0: RFC 2246 (https://www.rfc-editor.org/rfc/pdfrfc/rfc2246.txt.pdf)HTTP 1.1: RFC 2616 (https://www.rfc-editor.org/rfc/pdfrfc/rfc2616.txt.pdf)SMTP: RFC 2821 (https://www.rfc-editor.org/rfc/pdfrfc/rfc2821.txt.pdf)XMPP: RFC 3920 (https://www.rfc-editor.org/rfc/pdfrfc/rfc3920.txt.pdf)SSH: RFC 4250 (https://www.rfc-editor.org/rfc/pdfrfc/rfc4250.txt.pdf)TLS 1.2: RFC 5246 (https://www.rfc-editor.org/rfc/pdfrfc/rfc5246.txt.pdf)HTTP 2.0: RFC 7540 (https://www.rfc-editor.org/rfc/pdfrfc/rfc7540.txt.pdf)5. [10 points] There is a big difference between an application and an application protocol.Use the standard FTP client on most operating systems (on Windows and Linux, type ftpfrom a command prompt) and look at what the program can do. Then download thefreeware client FileZilla (FileZilla - The free FTP solution (filezilla-project.org) and lookat what this program can do. Both programs transfer files between client and server, butin different ways. Do you think that the user needs to know the details of the applicationprotocol in order to perform the function of transferring a file? Summarize thedifferences between an application and an application protocol.6. [no points for this one] – What do you want to get out of this course? What topics areyou most interested in?