Information Technology Reference
In-Depth Information
Foundation Summary
The Foundation Summary is a condensed collection of material that provides a convenient
review of key concepts in this chapter. If you are already comfortable with the topics in this
chapter, this summary will help you recall a few details. If you just read the Foundation Topics
section, this review should help solidify some key facts. If you are doing your final preparation
before the exam, these materials are a convenient way to review the day before the exam.
Frame Relay Concepts
Table 5-5
Item
Description
CIR
Defines the average upper limit of the PVC
DE
Specifies frames that can be discarded
FECN
Notifies the receiving DTE that the frame experienced congestion
BECN
Notifies the sending DTE that frames headed toward the destination are experiencing
congestion
FRTS
Receives BECN as input to manage Frame Relay Traffic by specifying parameters for
different classes
FRF.9
Standards based Frame Relay compression
Frame Relay LAPF Frame Address Field
Table 5-6
Bit
Description
DLCI
10-bit PVC identifier
C/R
Not used
EA
Extended Address; indicates if the containing byte is the last in the addressing field;
a mechanism to extend DLCI length beyond 10 bits
FECN
Bit set in frames traveling to the destination, when there is congestion on traffic from
source to destination
BECN
Bit set in frames traveling to the source, when there is congestion on traffic from source
to destination
DE
Bit set to indicate frame is eligible for discard
 
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