91. Consider a network connecting two systems located 8000 kilometers apart. The bandwidth of the network is 500 × 10^6 bits per second. The propagation speed of the media is 4 × 10^6 meters per second. It is needed to design a Go-Back-N sliding window protocol for this network. The average packet size is 10^7 bits. The network is to be used to its full capacity. Assume that processing delays at nodes are negligible. Then, the minimum size in bits of he sequence number field has to be ________.
a. 2
b. 4
c. 8
d. 16
Answer: (c).8

92. On a TCP connection, current congestion window size is Congestion Window = 4 KB. The window size advertised by the receiver is Advertise Window = 6 KB. The last byte sent by the sender is LastByteSent = 10240 and the last byte acknowledged by the receiver is LastByteAcked = 8192. The current window size at the sender is  
a. 2048 bytes
b. 4096 bytes
c. 6144 bytes
d. 8192 bytes
Answer: (b).4096 bytes

93. For a host machine that uses the token bucket algorithm for congestion control, the token bucket has a capacity of 1 megabyte and the maximum output rate is 20 megabytes per second. Tokens arrive at a rate to sustain output at a rate of 10 megabytes per second. The token bucket is currently full and the machine needs to send 12 megabytes of data. The minimum time required to transmit the data is _________________ seconds.
a. 1.1
b. 0.1
c. 2.1
d. 2.0
Answer: (a).1.1

94. Consider the following statements about the timeout value used in TCP. i. The timeout value is set to the RTT (Round Trip Time) measured during TCP connection establishment for the entire duration of the connection. ii. Appropriate RTT estimation algorithm is used to set the timeout value of a TCP connection. iii. Timeout value is set to twice the propagation delay from the sender to the receiver. Which of the following choices hold?
a. (i) is false, but (ii) and (iii) are true
b. (i) and (iii) are false, but (ii) is true
c. (i) and (ii) are false, but (iii) is true
d. (i), (ii) and (iii) are false
Answer: (b).(i) and (iii) are false, but (ii) is true

95. Consider a TCP connection in a state where there are no outstanding ACKs. The sender sends two segments back to back. The sequence numbers of the first and second segments are 230 and 290 respectively. The first segment was lost, but the second segment was received correctly by the receiver. Let X be the amount of data carried in the first segment (in bytes), and Y be the ACK number sent by the receiver. The values of X and Y (in that order) are
a. 60 and 290
b. 230 and 291
c. 60 and 231
d. 60 and 230
Answer: (d).60 and 230

96. Which of the following statements are TRUE?

(S1) TCP handles both congestion and flow control
(S2) UDP handles congestion but not flow control
(S3) Fast retransmit deals with congestion but not flow control
(S4) Slow start mechanism deals with both congestion and flow control
a. S1, S2 and S3 only
b. S1 and S3 only
c. S3 and S4 only
d. S1, S3 and S4 only
Answer: (b).S1 and S3 only

97. Consider different activities related to email.

m1: Send an email from a mail client to a mail server
m2: Download an email from mailbox server to a mail client
m3: Checking email in a web browser

Which is the application level protocol used in each activity?
a. ml: HTTP m2: SMTP m3: POP
b. ml: SMTP m2: FTP m3: HTTP
c. ml: SMTP m2: POP m3: HTTP
d. ml: POP m2: SMTP m3: IMAP
Answer: (c).ml: SMTP m2: POP m3: HTTP

98. Identify the correct order in which the following actions take place in an interaction between a web browser and a web server.

1. The web browser requests a webpage using HTTP.
2. The web browser establishes a TCP connection
with the web server.
3. The web server sends the requested webpage
using HTTP.
4. The web browser resolves the domain name
using DNS.
a. 4,2,1,3
b. 1,2,3,4
c. 4,1,2,3
d. 2,4,1,3
Answer: (a).4,2,1,3

99. A graphical HTML browser resident at a network client machine Q accesses a static HTML webpage from a HTTP server S. The static HTML page has exactly one static embedded image which is also at S. Assuming no caching, which one of the following is correct about the HTML webpage loading (including the embedded image)?
a. Q needs to send at least 2 HTTP requests to S, each necessarily in a separate TCP connection to server S
b. Q needs to send at least 2 HTTP requests to S, but a single TCP connection to server S is sufficient
c. A single HTTP request from Q to S is sufficient, and a single TCP connection between Q and S is necessary for this
d. A single HTTP request from Q to S is sufficient, and this is possible without any TCP connection between Q and S
Answer: (b).Q needs to send at least 2 HTTP requests to S, but a single TCP connection to server S is sufficient

100. Consider the following statements: I. telnet, ftp and http are application layer protocols. II.l EJB (Enterprise Java Beans) components can be deployed in a J2EE (Java2 Enterprise Edition) application server. III. If two languages conform to the Common Language Specification (CLS) of the Microsoft.NET framework, then a class defined in any one of them may be inherited in the other. Which statements are true?
a. l and II only
b. II and III only
c. l and III only
d. I, II and III
Answer: (a).l and II only