June 2012
11.
X.25 is ________ Network.
(A)
Connection Oriented Network
(B)
Connection Less Network
(C)
Either Connection Oriented or
Connection
Less
(D)
Neither Connection Oriented nor
Connection Less
june
2008
26.
The ATM cells ------ byte long
(a)48
(b)53 (c) 64 (d)69
1. Which
of the following network acess standard is used for connecting station to a
packet switched network?
A. X.3 B. X.21
C. X.25 D. X.75
2. How
many layers covered in X.25 standards?
a.3 b.4
c.2 d.7
3.
RS-232 RS-449 RS-530 V-24 and X-21 are
examples of
a. Standard
for various type of transmission channels
b. standards
for interface between terminals and modems
c. methods
for error detection and correction
d. Standard
for end to end performance of data communication system
4. An
example of network layer protocol is
a. Internet
protocol
b. X-25
packet level protocol
c. source
routing and domain naming
d. all
of the above
5. Standard
of electronic Industries association of America . what do the letter RS
stands for
a. Recognized
standard
b. Random
sequence
c. Recommended
standard
d. Registered
source
6. The
interface between the computer or terminal and the modem is an example of
a. Physical
layer protocol
b. Data
link layer protocol
c. Network
layer protocol
d. Transport
layer protocol
7. X.21
is
a. a
method of determining which device has access to transmission medium at any
time
b. a
method access control technique for multiple access transmission media
c. a
very common bit oriented data link protocol issued by ISO
d. network
access standard for connecting stations to a circuit switched network
8.
The address field of a Frame Relay frame is 1011000000010111. What is the DLCI
(in
decimal)?
9.
The address field of a Frame Relay frame is 101100000101001
10.
Find the DLCI value if the first 3 bytes received is 7C 74 El in hexadecimal.
Answers
8. We first need to look at the EA bits. In each byte,
the EA bit is the last bit (the eight bit from the left). If EA bit is 0, the
address ends at the current byte; if it 1, the address continues to the next
byte.
Address = 10110000 00010111
The first EA bit is 0 and the second is 1. This means
that the address is only two bytes (no address extension). DLCI is only 10
bits, bits 1 to 6 and 9 to 12 (from left).
Address →10110000 00010111
DLCI →1011000001 → 705
10. We first need to look at the EA bits. In each byte, the EA bit is
the last bit (the eight bit from the left). If the EA bit is 0, the address
ends at the current byte; if it 1, the address continues to the next byte.
Address = 0x7C74E1 =
01111100 01110100 11100001
The first two EA bit are 0s and the last
is 1. This means that the address is three bytes (address extension). DLCI is
16 bits, bits 1 to 6, 9 to 12, and 17 to 22.
Address = 01111100 01110100 111000
DLCI =
0111110111111000 = 32248
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