The document discusses High-level Data Link Control (HDLC), a bit-oriented protocol used for point-to-point and multipoint data links. It supports full-duplex communication and defines three types of frames - Unnumbered frames for link setup/disconnection, Information frames to carry data, and Supervisory frames to transport control information. HDLC also specifies different transfer modes including Normal Response Mode (NRM) with balanced and unbalanced configurations, and Asynchronous Balanced Mode (ABM) where each station can function as primary or secondary.

1. PRESENTATION
ON
HIGH-LEVEL DATA LINK
CONTROL
Under The Guidance Of:- Submitted By:-
Mr. Ashok Kr. Chauhan Prince Pal Singh
Senior Lecturer B.Tech (4th Year)
E.C.E Departmant E.C.E Dept.

2. CONTENTS
1. WHAT IS HDLC….?
2. HDLC TRANSFER MODES
3. HDLC FRAMES
4. FRAME FORMAT
(a) Flag Field
(b) Address Field
(c) Control Field
(d) Information Field
(e) FCS Field

3. WHAT IS HDLC…???
 High-level Data Link Control (HDLC) is a bit-
oriented protocol i.e use bits to stuff flags
occurring in data.
 HDLC was defined by ISO for use on both
point-to-point and multipoint data links.
 It supports full-duplex communication i.e
receive and transmit at the same time.

4. HDLC TRANSFER MODES
 Unbalanced Configuration:-
 Balanced Configuration:-
Primary
Secondary Secondary
Commands
Responses
Combined Combined
commands/Responses

5. CONTINUE…..
1. Normal Response Mode:-
 In NRM, the station configuration is
unbalanced i.e a primary station can only
send commands; a secondary station can
only respond.
 The NRM is used for both point-to-point
and multipoint links.
 Here, the secondary station will send only
when primary station instruct it to do so.

6. CONTINUE…..
1. NRM:-
Fig:- Point-to-Point Links
Fig:- Multipoint Links

7. 2. Asynchronous Response Mode:-
 In ARM, the configuration is unbalanced
like NRM only the difference is that here
the secondary station is independent of the
primary station.
CONTINUE…..

8. CONTINUE…..
1. Asynchronous Balanced Mode
 In ABM, the configuration is balanced.
 Here, the link is point-to-point and each
station can function as a primary and a
secondary.

9. HDLC FRAMES
HDLC
FRAMES
U-frame I-frame S-frame

10. CONTINUE…..
 Unnumbered frames (U-frames) :-
These frames are used in link set-up and
disconnection.
 Information frames (I-frames) :-
These frames carry the actual information.
 Supervisory frames (S-frames) :-
S-frames are used only to transport control
information.