Hdlc Overview; Hdlc Frame Structure - Alcatel-Lucent OmniAccess 700 Cli Configuration Manual

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Chapter name (automatic)
High-level Data Link Control
HDLC O
VERVIEW
Layer 2 of the OSI model is the data link layer. One of the most common layer 2
protocols is the High-level Data Link Control (HDLC) protocol. In fact, many other
layer 2 protocols are based on HDLC, particularly its framing structure.
Note: The OA-700 supports only Cisco HDLC.
The following sections describe HDLC:
•

"HDLC Frame Structure"

•
"HDLC Frame Formats"
•
"HDLC Protocol Operation"
HDLC F S
RAME TRUCTURE
HDLC data units transmitted from one station to another are referred to as
"frames". The figure shown below is a graphical representation of an HDLC frame
with information field.
F
Figure 26: An HDLC frame with an information field
Flag Field(F)
Address Field(A)
Control Field(C)
Information Field(I)
Frame Check Sequence(FCS)
Closing Flag Field(F)
284
Beta
C
A
Field Name
Alcatel-Lucent
FCS
I
Size (in bits)
8 bits
8 bits
8 or 16 bits
Variable; Not used in some frames
16 or 32 bits
8 bits
CLI Configuration Guide
Beta
F