HIGH-LEVEL DATA LINK
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.
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
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.
1. Normal Response Mode:-
In NRM, the station configuration is
unbalanced i.e a primary station can only
send commands; a secondary station can
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.
Unnumbered frames (U-frames) :-
These frames are used in link set-up and
Information frames (I-frames) :-
These frames carry the actual information.
Supervisory frames (S-frames) :-
S-frames are used only to transport control