TCP/IP Free Networking Solution With Microsoft

Questions: a) 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 a DNS lookup is necessary to obtain the IP address. Suppose that n DNS servers are visited before your host receives the IP address from DNS; the successive visits incur an RTT of RTT1, RTT2, , RTTn. Further suppose that the Webpage associated with the link contains exactly one object, consisting of a small amount of HTML test. Let RTT0 denote the RTT between the local host and the server containing the object. Assuming zero transmission time of the object, how much time elapses from when the client clicks on the link until the client receives the object? Suppose the HTML file references four very small objects on the same server. Neglecting transmission times, how much time elapses with : a. Non-persistent HTTP with no parallel TCP connections? b. Persistent HTTP? b) Below is a portion of a possible DNS database for cs.vu.nl. Give you understanding of the function of the following resource record. And give explanation of the meaning for each field in this resource record. www.cs.vu.nl 86400 IN CNAME star.cs.vu.nl What is a whois database? Use various whois databases on the internet to obtain the names of two DNS servers. Indicate which whois databases you used. Use nslookup on centralops.net/co to send DNS queries to DNS servers with the IP address of a public google DNS for a domain name. Try querying for Type A, NS, and MX reports. List a record of each query and explain the meaning of the resource record you have listed. c) TCP and UDP are transport layer protocols. (a) What is Round Trip Time (RTT)? Do you need to set a timer for data transmission using UDP? Give your reasoning. (b) Consider the TCP procedure for estimating RTT. Suppose that we use exponential weighted moving average (EWMA) for estimating RTT using formula: EstimatedRTT(n) = (1- )*EstimatedRTT(n-1) + *SampleRTT(n-1), The margin is esti mated by formula: DevRTT(n) = (1-)*DevRTT(n-1) + *|SampleRTT(n-1)-EstimatedRTT(n-1)|, Where n is the transmission round. Suppose that = 0.25, = 0.3. Let initial Estimated RTT at transmission round 3 be 90 ms, let estimated margin DevRTT at transmission round 4 be 15 ms. The observed SampleRTT at transmission round 3 is 75ms, the observed SampleRTT at transmission round 4 is 95ms. What is the Estimated RTT at transmission round 5? What is the Estimated margin DevRTT at transmission round 5? If the TCP timeout interval is set using the formula TimeoutInterval(n) = EstimatedRTT(n) + 4* DevRTT(n), what is the TimeoutInterval for transmission round 5 (round to the nearest integer)? d) The UDP checksum provides for error detection. Suppose that we have the following 16-bit words: Word 1: ********11001100 Word 2: ********00000110 Word 3: ********01101100 Question: What is the checksum field in the UDP segment, if the three words are transferred via UDP? Explain in detail how you obtain you r result? Answer: a)a) Initially we ascertain the aggregate sum of time to get the IP address which is: RTT1 + RTT2 + + RTTn . Presently, once we get we the IP address, one RTT0 is utilized to situated up the TCP association and one more RTT0 is utilized to demand and get the little question.Therefore the aggregate reaction time is 2RTTo + RTT1 + RTT2 + + RTTn. a) RTT1 + + RTTn + 2 RTTo + 4 2 RTTo = 10RTTo + RTT1 + + RTTn b) RTT1 + + RTTn + 2 RTTo + RTTo = 3RTTo + RTT1b)a) www.cs.vu.nl 86400 IN CNAME star.cs.vu.nlname - www.cs.vu.nl, this is the host for the domainTTL - 86400, The TTL gives the duration in seconds for which the record may be cached by the client side program. Class IN ,the class defines the type of record, in which IN means the internet and CNAME record makes one domain name alias of another. star.cs.vu.nl is an alias for www.cs.vu.nl.This record is a CNAME type record that is used to make star.cs.vu.nl an alias for www.cs.vu.nl.b) WHOIS is an open database that permits us to d iscover the data around a particular area name. We can discover who enlisted an area name, who the enlistment center was and we discover the contact of the manager of a space.c) We are using who.is and whois.net databasesAddress - 8.8.8.8 Name - Level 3 Communications, Inc. Address 81.218.119.11Name - IL-BEZEQ-INTERNATIONAL-20021018d) 1) yahoo.com IN A 206.190.36.45 1127s (00:18:47)In this record yahoo.com is the domain name or the host name IN specifies it is a type of internet record.A maps the domain name to the IP address206.190.36.45 is the IP address which is mapped to the domain.1127 is the TTL, ie the time for which the record will be cached by the client side program.2) yahoo.com IN NS ns4.yahoo.com 21210s (05:53:30)NS stands for name server and list the name server for a particular domain ns4.yahoo.com is the nameserver for this domain.3) yahoo.com IN MX preference: 1 exchange: mta6.am0.yahoodns.net 635s (00:10:35)MX stands for mail exchange and gives the name of mail ser ver responsible for accepting emails for the domain. Preference is used to specify priority in case of multiple mail servers.mta6.am0.yahoodns.net 635s name of the mail serverc)a) Round-excursion time (RTT), is the time required for a sign or information parcel to head out from source to destination and back again to the beginning source. For eg. a PC A pings a PC B and afterward B retransmits the message to A then the aggregate time expended in this is the round outing time.In UDP there is no need to use timers. UDP is a connectionless and unreliable protocol that does not guarantee the delivery of message to the receiver. UDP is meant for applications where the concern is to keep the messages flowing in a stream rather than guaranteeing that every message is delivered. In TCP timer is used for retransmission of message after the timer has expired and the acknowledgement for the message is not received. But in UDP there is no acknowledgement and retransmission therefore there is no need to use the timer.b) EstimatedRTT(3) =90msDevRTT(4) =15msSampleRTT(3) =75msSampleRTT(4) =95ms = .25, = .3EstimatedRTT(n) = (1- )*EstimatedRTT(n-1) + *SampleRTT(n-1)EstimatedRTT(4) = (1- .25)*EstimatedRTT(3) + *SampleRTT(3) = .75*90 +.25*75 = 86.25msEstimatedRTT(5) = (1- .25)*EstimatedRTT(4) + *SampleRTT(4) = .75*86.25 +.25*95 = 88.43msDevRTT(n) = (1-)*DevRTT(n-1) + *|SampleRTT(n-1)-EstimatedRTT(n-1)|DevRTT(5) = (1-.3)*DevRTT(4) + *|SampleRTT(4)-EstimatedRTT(4)| = (1-.3)*15 + .3*|95-86.25|=13.125msTimeoutInterval(5) = EstimatedRTT(5) + 4* DevRTT(5) = 88.43+4*13.125 = 140.93 =141 msd) UDP checksum is calculated for UDP header and data. UDP checksum contains the source and destination IP and for this a pseudo-header is taken This pseudo-header is added to UDP datagram at the time of checksum calculation. The checksum bits in UDP datagram are all 0 at the time of calculation and the data is padded with 0s with the data is not in multiple of 16. Now we take the pseudo hea der and UDP datagram and divide it into slots of 16 bits each. Next we add all 16 bits one by one. We take the ones compliment of the final answer and this is our checksum.Assuming data to solve the questionsource IP address: 153.18.8.105dest IP address: 172.2.14.10protocol:17length: 14source port: 1087dest port: 13udp length: 14checksum :0calculation10011001 0001001000001000 0110100110101011 0000001000001110 0000101000000000 0001000100000000 0000111000000100 0011111100000000 0000110100000000 0000111000000000 0000000000000000 1100110001100000 0000011010110110 0110110001110110 0011111010001001 11000001 - checksum References Heywood, D., 1998.Networking with Microsoft TCP/IP. Indianapolis, Ind.: New Riders. Sarkar, N., 2006. Teaching TCP/IP Networking Using Practical Laboratory Exercises.International Journal of Information and Communication Technology Education, 2(4), pp.39-50.