Chapter 2. Technology Overview
61200263L1-1.1
ATLAS Frame Relay User Manual
2-5
Data Link Connection Identifier (DLCI)
An address called a Data Link Connection Identifier (DLCI) uniquely iden-
tifies each of the virtual circuits in the frame relay network. A DLCI does not
address the equipment at the far end of the virtual circuit, but addresses the
next piece of frame relay equipment within the network. The next piece of
frame relay equipment now becomes responsible for transporting all frames
from the incoming port to the appropriate outgoing port.
Figure 2-3 illustrates a network using DLCI assignments. In this example,
the router at site A sends a frame packet to site B, by placing the data on
DLCI 100. Knowing that all packets coming in DLCI 100 must go out DLCI
225, Frame Relay Switch A places the packets on DLCI 225 and sends them
out to Frame Relay Switch B. Frame Relay Switch B then takes the frame
packets from DLCI 225 and places them on DLCI 35 for delivery to the site
B router. From this example, you can see that each piece of frame relay
equipment only knows about the DLCIs local to it. Hence, you will hear
“DLCIs only have local significance.”
Figure 2-3. Network Using DLCI Assignments
User-to-Network Interface
The interface between the customer and the frame relay switch is called the
User-to-Network Interface (UNI). Three different types of signaling can
transmit across this interface: LMI (Group of Four), Annex A
(ITU-T Q.933-A), and Annex D (ANSI T1.617-D). Unfortunately, due to sig-
naling differences among the three types, they are incompatible with one an-
other, and DLCI assignments vary among the three types. Tables 2-2 and
2-3 give the assignments for the three types.
DLCI 100
A
Frame Relay/Router
C
Frame Relay/Router
DLCI 200
DLCI 225
DLCI 35
DLCI 650
DLCI 501
B
Frame Relay/Router
Frame Relay
Switch B
Frame Relay
Switch A
Summary of Contents for ATLAS
Page 1: ...ATLAS Frame Relay User Manual Part Number 1200263L1 1 61200263L1 1 1D May 2000...
Page 10: ...List of Figures x ATLAS Frame Relay User Manual 61200263L1 1 1...
Page 12: ...List of Tables xii ATLAS Frame Relay User Manual 61200263L1 1 1...
Page 16: ...Chapter 1 Introducing ATLAS Frame Relay 1 4 ATLAS Frame Relay User Manual 61200263L1 1 1...
Page 28: ...Chapter 3 Enabling Frame Relay 3 4 ATLAS Frame Relay User Manual 61200263L1 1 1...
Page 52: ...Chapter 4 Defining Packet Endpoints 4 24 ATLAS Frame Relay User Manual 61200263L1 1 1...
Page 82: ...Chapter 6 Frame Relay Configuration Examples 6 22 ATLAS Frame Relay User Manual 61200263L1 1 1...
Page 90: ...Chapter 7 Using Frame Relay IQ 7 8 ATLAS Frame Relay User Manual 61200263L1 1 1...
Page 104: ...Index Index 6 ATLAS Frame Relay User Manual 61200263L1 1 1...
Page 106: ......