Web Services Protocols - Essay Example

Labs List up to 10 different protocols that appear in the protocol column in the unfiltered packet-listing windowin step 7 above. HTTP TCP DNS HTTP ARP BitTorro Bit-uTP ICMP SSDP RELOAD DHCPv6 GNutell 2. How long did it take from when the HTTP GET message was sent until the HTTP OK reply was received? (By default, the value of the Time column in the packetlisting window is the amount of time, in seconds, since Wireshark tracing began. To display the Time field in time-of-day format, select the Wireshark View pull down menu, then select Time Display Format, then select Time-of-day.) Time taken: 09:21:12.488693000 -09:21:12.540971000 3. What is the Internet address of the gaia.cs.umass.edu (also known as wwwnet. cs.umass.edu)? What is the Internet address of your computer? Internet address of gaia.cs.umass.edu: 128.119.245.12 My computer internet address: 192.168.0.102 4. Print the two HTTP messages displayed in step 9 above. To do so, select Print from the Wireshark File command menu, and select “Selected Packet Only” and “Print as displayed” and then click OK. No. Time Source Destination Protocol Length Info 5480 09:21:12.083204000 192.168.0.102 128.119.245.12 HTTP 527 GET /wireshark- Frame 5480: 527 bytes on wire (4216 bits), 527 bytes captured (4216 bits) on interface 0 Ethernet II, Src: Hewlett-_3c:31:68 (00:24:81:3c:31:68), Dst: D-Link_c0:d7:4c (34:08:04:c0:d7:4c) Internet Protocol Version 4, Src: 192.168.0.102 (192.168.0.102), Dst: 128.119.245.12 (128.119.245.12) Transmission Control Protocol, Src Port: 49636 (49636), Dst Port: http (80), Seq: 1, Ack: 1, Len: 461 Hypertext Transfer Protocol GET /wireshark-labs/INTRO-wireshark-file1.html HTTP/1.1\r\n Host: gaia.cs.umass.edu\r\n User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:7.0.1) Gecko/20100101 Firefox/7.0.1\r\n Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n Accept-Language: en-us,en;q=0.5\r\n Accept-Encoding: gzip, deflate\r\n Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\n Connection: keep-alive\r\n If-Modified-Since: Sat, 28 Apr 2012 06:14:01 GMT\r\n If-None-Match: "8734b-51-20893c40"\r\n \r\n [Full request URI: http://gaia.cs.umass.edu/wireshark-labs/INTRO-wireshark-file1.html] Note: the printed file is in pdf called lab print. Lab 2: 1. Select one packet. From this packet, determine how many fields there are in the UDP header. Name these fields. There are six fields namely: Time, Source, Destination, Protocol, Length, Info 2. From the packet content field, determine the length (in bytes) of each of the UDP header fields. Differentiated service field: 147 bytes, User Datagram protocol : 127, Data 119 , Internet protocol : 20 bytes. 3. The value in the Length field is the length of what? Verify your claim with your captured UDP packet. The length represents Frame length for the packet. Lab 3 1. What is the IP address and TCP port number used by the client computer (source) that is transferring the file to gaia.cs.umass.edu? To answer this question, it’s probably easiest to select an HTTP message and explore the details of the TCP packet used to carry this HTTP message, using the “details of the selected packet header window” (refer to Figure 2 in the “Getting Started with Wireshark” Lab if you’re uncertain about the Wireshark windows) Ip address of client computer(source): 192.168.0.102 TCP port number: 59378 2. What is the IP address of gaia.cs.umass.edu? On what port number is it sending and receiving TCP segments for this connection? IP address : 128.119.245.12 http port number: 80 3. What is the IP address and TCP port number used by your client computer (source) to transfer the file to gaia.cs.umass.edu? Ip address of client computer (source): 192.168.0.102 TCP port number: 59378 4. What is the sequence number of the TCP SYN segment that is used to initiate the TCP connection between the client computer and gaia.cs.umass.edu? What is it in the segment that identifies the segment as a SYN segment? Sequence number:0 Stream index:178 5. What is the sequence number of the SYNACK segment sent by gaia.cs.umass.edu to the client computer in reply to the SYN? What is the value of the ACKnowledgement field in the SYNACK segment? How did gaia.cs.umass.edu determine that value? What is it in the segment that identifies the segment as a SYNACK segment? Sequence number:4176475 Acknowledgement number :4644 6. What is the sequence number of the TCP segment containing the HTTP POST command? Note that in order to find the POST command, you’ll need to dig into the packet content field at the bottom of the Wireshark window, looking for a segment with a “POST” within its DATA field. Sequence number: 1 Next sequence number 754 7. Consider the TCP segment containing the HTTP POST as the first segment in the TCP connection. What are the sequence numbers of the first six segments in the TCP connection (including the segment containing the HTTP POST)? At what time was each segment sent? When was the ACK for each segment received? Given the difference between when each TCP segment was sent, and when its acknowledgement was received, what is the RTT value for each of the six segments? What is the EstimatedRTT value after the receipt of each ACK? Assume that the value of the EstimatedRTT is equal to the measured RTT for the first segment, and then is computed using the EstimatedRTT equation as below for all subsequent segments Estimated RTT = 0.875*Estimated RTT + 0.125*SampleRTT Note: Wireshark has a nice feature that allows you to plot the RTT for each of the TCP segments sent. Select a TCP segment in the “listing of captured packets” window that is being sent from the client to the gaia.cs.umass.edu server. Then select: Statistics->TCP Stream Graph->Round Trip Time Graph. Sequence number: 1 Next sequence number 340 Next sequence number 427 8. What is the length of each of the first six TCP segments? ASY- 4 ACK – 4 PSH -6 9. What is the minimum amount of available buffer space advertised at the received for the entire trace? Does the lack of receiver buffer space ever throttle the sender? 10. Are there any retransmitted segments in the trace file? What did you check for (in the trace) in order to answer this question? Yes there were retransmissions: by checking the details on TCP Retransmission. 11. How much data does the receiver typically acknowledge in an ACK? Can you identify cases where the receiver is ACKing every other received segment. Header length of 20 bytes 12. What is the throughput (bytes transferred per unit time) for the TCP connection? Explain how you calculated this value. - Windows size value: 16544 convert bytes to bits 16544/64 =258 258/60= 4 seconds The RTT to ACK the segment was: 0.000040000 seconds Lab 4 1. Is your browser running HTTP version 1.0 or 1.1? What version of HTTP is the server running? Request version: HTTP version/ 1.1 2. What languages (if any) does your browser indicate that it can accept to the server? Accept –Language: en-us;q=0.5\r\n. The language is English. 3. What is the IP address of your computer? Of the gaia.cs.umass.edu server? a. Internet address of gaia.cs.umass.edu: 128.119.245.12 b. My computer internet address: 192.168.0.102 4. What is the status code returned from the server to your browser? Status code: 200 Response phrase: Ok 5. When the HTML file that you are retrieving was last modified at the server? Last Modified: Sat, 28 Apr 2012 06:21:01 GMT\r\n 6. How many bytes of content are being returned to your browser? Content length: 81 Content type: text/html; charset=UTF-8\r\n Lab 5: DHCP 1. Are DHCP messages sent over UDP or TCP? UDP 2. Draw a timing datagram illustrating the sequence of the first four-packet Discover/Offer/Request/ACK DHCP exchange between the client and server. For each packet, indicated the source and destination port numbers. Are the port numbers the same as in the example given in this lab assignment? Source Port Number Destination Port Number Time (sec) Discover 68 67 0 Offer 67 68 0 Request 68 67 0 ACK DHCP 67 68 0 The ports do not change but alternate 3. What is the link-layer (e.g., Ethernet) address of your host? Address: D-Link_c0:d7:4c (34:08:04:c0:d7:4c) 4. What values in the DHCP discover message differentiate this message from the DHCP request message? Source and destination address. 5. What is the value of the Transaction-ID in each of the first four (Discover/Offer/Request/ACK) DHCP messages? What are the values of the Transaction-ID in the second set (Request/ACK) set of DHCP messages? What is the purpose of the Transaction-ID field? DHCP Transaction ID Discover 0x5171459 Offer 0x5171459 Request 0x5171459 Second Set Discover 0x969c3dfc Offer 0x969c3dfc Request 0x969c3dfc transaction id is used for both the DISCOVER/OFFER and REQUEST/ACK phases 6. A host uses DHCP to obtain an IP address, among other things. But a host’s IP address is not confirmed until the end of the four-message exchange! If the IP address is not set until the end of the four-message exchange, then what values are used in the IP datagram in the four-message exchange? For each of the four DHCP messages (Discover/Offer/Request/ACK DHCP), indicate the source and destination IP addresses that are carried in the encapsulating IP datagram. Source Address Destination Address Discover 00:24:81:3c:31:68 ff:ff:ff:ff:ff:ff Offer 34:08:04:c0:d7:4c ff:ff:ff:ff:ff:ff Request 00:24:81:3c:31:68 ff:ff:ff:ff:ff:ff ACK DHCP 34:08:04:c0:d7:4c ff:ff:ff:ff:ff:ff 7. What is the IP address of your DHCP server? 192.168.0.1 8. What IP address is the DHCP server offering to your host in the DHCP Offer message? Indicate which DHCP message contains the offered DHCP address. 192.168.0.102 Your (client) IP address: 192.168.0.102 9. In the example screenshot in this assignment, there is no relay agent between the host and the DHCP server. What values in the trace indicate the absence of a relay agent? Is there a relay agent in your experiment? If so what is the IP address of the agent? Relay agent IP Address: 0.0.0.0 10. Explain the purpose of the router and subnet mask lines in the DHCP offer message. The router is acting as a gateway. The IP address is 192.168.0.2 The subnet mask is used to indicate the class of the IP address used which is class C. 11. In the example screenshots in this assignment, the host requests the offered IP address in the DHCP Request message. What happens in your own experiment? In my experiment the host requests the offered IP address in the DHCP Request message. 12. Explain the purpose of the lease time. How long is the lease time in your experiment? Is the time it takes the DHCP server to renew an IP address. In my experiment it is 1 day (24 hours) 13. What is the purpose of the DHCP release message? Does the DHCP server issue an acknowledgment of receipt of the client’s DHCP request? What would happen if the client’s DHCP release message is lost? Release message is used to let go of IP address from the DHCP client computer. 14. Clear the bootp filter from your Wireshark window. Were any ARP packets sent or received during the DHCP packet-exchange period? If so, explain the purpose of those ARP packets. Yes there where ARP packets sent. ARP is used to determine hardware address that corresponds to an IP address. Lab 6: Repeat of lab 5 Read More