Alcatel Carrier Internetworking Solutions Switch/Router 사용자 설명서

Page 29-6

The 

WSX

 supports Permanent Virtual Circuits (

PVCs

), but not Switched Virtual Circuits (

SVCs

). 

Most service carriers do not currently offer 

SVCs

. 

PVCs

 are either static (configured) or 

dynamic (learned). Static 

PVCs

 are user-configured and consist of Management, or Control, 

PVCs

 and any configured Data 

PVC

s. Management VCs are used by the 

WSX

 to communicate 

with the Frame Relay network. Dynamic 

PVCs

 are usually data circuits, which are controlled 

by the Frame Relay network and not configured in advance. A logical Frame Relay 

DTE

 

device like the 

WSX

 does not create or control dynamic data VCs. It is only informed of their 

status through periodic Status updates from the Frame Relay network.

Each virtual circuit is locally defined by a Data Link Connection Identifier (

DLCI

). The Frame 

Relay network assigns the 

DLCIs

 and informs the 

WSX

 about them.

DLCI

 numbers from 0 to 15 and 992 to 1023 are reserved for Control VCs. If you are using 

Annex A or Annex D as your 

DLCMI

, the management control VC will be assigned DLCI 0. If 

you are using the LMI Revision 1.0 

DLCMI

, then the management control VC will be assigned 

DLCI 1023

.

DLCI

 numbers from 16 to 991 are reserved for Data VCs.

You may have up to 256 virtual circuits and up to 128 virtual ports on a 

WSX

.

A VC may or may not have the same 

DLCI

 on each side of a 

WAN

 link. For example, if a 

WSX

 

physical port contains three Frame Relay VCs on its local network with 

DLCIs

 16, 17, and 18, 

these same VCs on the other side of the Frame Relay network might be 30, 31, and 32. The 
two sets of 

DLCIs

 are technically part of the same virtual circuits, but their values may or may 

not be different. 

DLCIs

 are only significant locally.

At any one time, a virtual circuit will be active, inactive or deleted. If a virtual circuit is Active 
it can transmit and receive data. If it is Inactive, the Frame Relay network still sees the virtual 
circuit, but there is a problem with it and it is discarding data. If the virtual circuit is Deleted, 
then the virtual circuit is not transmitting or receiving data and no 

DLCI

 exists for it.