Computer Networks: TCP Connection Termination Process

The client wants to retrieve some information about toys from the besttoys.com website, so GET is used because the client want to retrieve or get something (Howard, 2008.). The besttoys.com web server loads the information as per the client request and a customer file is saved in the webserver with an ID 12343 to identify that specific client which is a shopping cart where list of what client wants to shop is stored. 

The server responds to the client request with the web page having different types of toys. At the same time, a vendor file is created and in the client browser with the same ID 12343 as the customer file saved in the web server of the besttoys.com and keeps on updating with client information. Also a cookie is set which will be used to track the client (Huang, 2010). Whenever the client requests for something from that specific website, it would be fast to log in. That cookie may last forever provided it is not destroyed. The web page the client is displayed contains different toys’ images which may act like links.The client clicks an image of a certain toy on that web page, that image acts as a link to retrieval of more information concerning that image which in turn is sent a request to the server where that request is send together with the cookie: 12343. 

After the server receives the request from the client, it displays back the page containing all the information about the price of the image toy the client clicked. Then, that information is updated in the customer file which is saved in the web server side (Lund et al., 2010). The cookie which was sent together with the request is the one that helps the web server to track that specific client file from their server and then is updated until the customer or client finishes to shop.

Then, the customer requests from the same site information about the payment of the toy clicked, the same thing happens, the request is sent together with the cookie: 12343, thus helping the server in updating the file for that specific client.

All through the cookie has been getting information about the client, so the request of the client about the payment, is responded efficiently where an order confirmation web page is displayed on the client browser according to what the client has selected from the webpage. 

1. B).The banner advert is not hosted at the web server of the current website that it is being advertised from. Deakin University is displaying an advert of a product in its website where it is paid by the advertising company in accordance with the number of clicks of that advert which is linked to the manufacturers’ web server.

The advertising company has to keep tracks of the number of clicks or visitors to the manufacturer’s website using that banner advert, so application of cookies is a preferred option to track the visitors.  

i). Client request for a web page of Deakin University website from the client web browser, at the same time a cookie set with an ID 5252 and is saved in the client web browser (Jeffres and Lin, 2012). The web page that the client has requested contains banner ad of product which is not hosted from the deakin web server.

ii). When the client want to view that banner ad, the client is redirected to manufacturer website through his/her web browser. From here, the client will be directly linked to the manufacturer website from his/her browser.

iii). After the client is redirect, a request of the manufacturers web page containing the information about their product is sent. While this request is sent, a new cookie is created in the client browser where this cookie is the same as the previous cookie created while requesting deakin university website.

iv). Now the client is able to view the page about the product on the banner ad. So, the advertising company now is able to keep track of the clicks from the Deakin university website using those cookies IDs assigned on both sides which are the same. 

The segment tables below have port numbers where port 51000 signifies that it’s the client initiating that segment while the port 80 signifies that it’s the client initiating that segment.

Each table represent every segment that is used in the TCP connection establishment, data transfer and connection  termination with the appropriate header information; starting with the source and destination ports, sequence numbers, acknowledgment numbers, window and the Bytes of data transferred (Janse and Konijnendijk, 2011).

1. SYN segment

This is the first segment that is sent by the client to the server As it they want to establish a connection. Basically, the client Sends a sync message as it wants to initiate a TCP connection Where the acknowledgement is 0 and no data bytes of data is Sent because there is no connection.

2. SYN+ACK segment

This segment is sent by the server to notify the client that it has Accepted by sending back the syn and an acknowledgement That is SYN + ACK. To get another acknowledgement number, The sequence number of the client is incremented by 1. Also in this stage there is no data to be sent until connection is Successfully established.

ACK segment + Bytes of data

This segment is initiated by the client after the sever sends the Syn + ack which is an indication that it has already Acknowledged.  Now from this point the client is ready to send the bytes of Data because the connection is already established with the acknowledgement attached. The ACK No. is the initial sequence number destination incremented by one.

4. ACK segment  + Bytes of Data

Here, the client also wants to send another data. So, the client

has to send those bytes of data together with the

acknowledgement just like in the previous segment. Also as you

can note the segment takes the window of 4000 which is the

same as the server’s window. 

5. ACK segment + bytes of data

In this segment , the server responds by sending 1000 bytes of data  with a sequence number of 21733 and an acknowledge- ment number of 3049 which is gotten by adding the last two segments bytes of data lengths which add up to 1000 (Rose,  Basdas and Degen, 2009). The window size reduces from 4000 to 3000 as a result of subtraction of the bytes of data being sent. These bytes of data are sent with an acknowledgement.

6. FIN segment

FIN is initiated by the client when there is no more data to be sent. So, the client sends a FIN segment to signify the TCP connection termination (Walther and Jang 2012). After sending it, it holds back for the server to acknowledge whether to terminate that connection. That means it can’t terminate without receiving an acknowledgement. There is not data to be sent.  

7. FIN + ACK segment

When the server receives the Fin message from the client, it re-send FIN segment having acknowledgement if it is done transmitting data. This is to basically, accept that it is ready for TCP connection termination.   

8. ACK Segment

This is an acknowledgement from the client that shows that the client has got an acknowledgment from the server that it’s okay with the client terminating the TCP connection.   

Braun, L., Münz, G. and Carle, G., 2010, April. Packet sampling for worm and botnet detection in TCP connections. In Network Operations and Management Symposium (NOMS), 2010 IEEE (pp. 264-271). IEEE.

Howard, R.G., 2008. The vernacular web of participatory media. Critical Studies in Media Communication, 25(5), pp.490-513.

Huang, M.H., 2010. Designing website attributes to induce experiential encounters. computers in Human Behavior, 19(4), pp.425-442.

Lund, P.K., Petry, S.M., Croteau, C.S., Okumura, K.K. and Carroll, D.A., Google Inc, 2010. Source reputation information system with blocking of TCP connections from sources of electronic messages. U.S. Patent 7,788,359.

Janse, G. and Konijnendijk, C.C., 2011. Communication between science, policy and citizens in public participation in urban forestry websites—Experiences from the Neighbourwoods project. Urban Forestry & Urban Greening, 6(1), pp.23-40.

Jeffres, L.W. and Lin, C.A., 2012. Metropolitan websites as urban communication. Journal of Computer-Mediated Communication, 11(4), pp.957-980.

Rose, G., Basdas, B. and Degen, M., 2009. Using websites to disseminate research on urban spatialities. Geography Compass, 3(6), pp.2098-2108.

Walther, J.B. and Jang, J.W., 2012. Communication processes in participatory websites. Journal of Computer-Mediated Communication, 18(1), pp.2-15.