Local Management Interface (Lmi); Annex A And Annex D; Committed Information Rate (Cir); Table 2-2. Lmi (Group Of Four) Dlci Assignments - ADTRAN ATLAS User Manual

Chapter 2. Technology Overview

Local Management Interface (LMI)

Annex A and Annex D

Committed Information Rate (CIR)

2-6
LMI is the standard published by the Frame Relay Consortium in 1990 to
create a defined interface on the UNI. The Consortium, composed of Cisco
Systems, DEC, Nortel, and StrataCom, is commonly referred to as the Group
of Four.

Table 2-2. LMI (Group of Four) DLCI Assignments

The International Telecommunications Union Telecommunication Stan-
dardization Sector (ITU-T) adopted Annex A as the interface standard for in-
ternational frame relay applications. The American National Standards
Institute (ANSI) modified the Frame Relay Consortium's interface specifica-
tion and ratified it as Annex D—an interface standard for the United States.

Table 2-3. Annex A and Annex D DLCI Assignments

DLCI
0
1-15
16-991
992-1007
1008-1022 Reserved for future use.
1023
Customers can order a circuit with a guaranteed amount of bandwidth for
their virtual connections. This amount is called the Committed Information
Rate (CIR), and it defines how much bandwidth the customer is guaranteed
during normal network operation. Any data transmitted above this pur-
chased rate is discard eligible (DE) by the network. That is, this data can be
discarded in the event of network congestion.
The CIR can be thought of as the size of the virtual connection from end to
end. The CIR can be purchased in different increments up to the wire speed
of the slowest link. For example, if the circuit in Figure 2-3 had T1 access
from site A to the frame relay network and a 56-kbps DDS line from site B to
the frame relay network, the largest CIR available for purchase would be
ATLAS Frame Relay User Manual
DLCI
0 Call control signaling channel.
1-15 Reserved for future use.
16-1007 Available for customer data.
1008-1022 Reserved for future use.
1023 LMI channel.
Use
Carries frame relay signaling (LMI channel).
Reserved for future use.
Available for customer data.
Management DLCIs for layer 2.
Higher layer protocol communication channel.
Use
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