Anna University Coimbatore 2009 B.E Electronics

which means retransmission of data in three cases.
a) Damaged frame
b) Lost frame
c) Lost acknowledgment.
24. Mention the function of go-back N-ARQ.
It is the popular mechanism for continuous transmission fault control. In the
method, if our frame is lost or damaged, all frames sent since the last frame
acknowledged are retransmitted.
25. What is selective reject ARQ?
In selective reject ARQ only the specific damaged or lost frame is retransmitted.
If a frame is corrupted in transit, a NAK is returned and the frame is resent out of
sequence.
26. describe HDLC.
It is a bit-oriented data link protocol designed to support both half-duplex and full
duplex communication over point to point and midpoint links.
27. List the kinds of stations is HDLC.
HDLC differentiates ranging from three kinds of stations.
a) Primary
b) Secondary
c) Combined
28. describe configuration.
The bond configuration refers to the relationship of hardware devices on a link.
29. List the different ways of station configuration.
The stations are configured in three ways
a) Unbalanced configuration
b) Symmetrical configuration
c) Balanced configuration
30. elaborate the various communication modes in HDLC?
HDLC supports three modes of communication ranging from stations.
a) Normal response mode (NRM)
b) Asynchronous response mode (ARM)
c) Asynchronous balanced mode (ABM)
31. Mention the kinds of frames in HDLC.
There are three kinds of HDLC frames.
a) info frames (I-frames)
b) Supervisory frames (S-frames)
c) Unnumbered frames (U-frames)
32. provide the usage of I, S, U frames.
I frames – used to transport user data and control info relating to user data.
S frames – used only to transport control information, primarily data link layer
and fault controls.
U frames – reserved for systems management.
33. Write the kinds of frame fields contained in HDLC.
every frame in HDLC may contain up to six fields.
a) Beginning flag field
b) An address field
c) A control field
d) An info field
e) A frame check sequence (FCS) field
f) An ending flag field.
34. What is meant by bit stuffing?
Bit stuffing is the process of adding 1 extra 0 whenever there are five consecutive

Earning:   Approval pending.