Nortel Networks CG030601 User Manual

Frame Relay on Contivity Secure IP Services Gateway 
 

CG030601  

           

2.00         July 2003

 

 

Page: 2 of 14 

 

ITU-T (formerly CCITT) standards do not use this bit. 
 

The FECN and BECN indicate congestion on the network. For information about how the 
frame relay software uses these bits, see “Congestion Control”. 
 

The DE bit allows the router to mark specific frames as low priority (discard eligible) 
before transmitting them to the frame relay network. 
 

The EA bit signals whether the next byte is part of the address. This bit indicates the last 
byte of the DLCI. 
 

Frame relay is an access protocol that runs between a CES or data terminal equipment 
(DTE) and a switch or data communications equipment (DCE). The CES and the switch 
use the Data Link Control Management Interface (DLCMI) to exchange information 
about the interface and the status of each virtual circuit. 
 
DLCMI supports three standard data link management specifications: LMI, ANSI T1.617 
Annex D, and CCITT (now ITU-T) Q.933 Annex A. 
 

•

  The networking industry first developed the local management interface (LMI) 

specification. The LMI approach is asymmetric; the router sends a status-inquiry 
message to the network, signaling that the router’s connection to the network is 
functioning. The network replies with a status response. 

•

  ANSI modified the LMI specification and incorporated it as Annex D to ANSI 

standard T1.617. The ANSI method is generally similar to the LMI approach. 

•

  The CCITT (now ITU-T) modified the ANSI standard and adopted it as Annex A 

to Q.933. The CCITT Annex A specification is similar to Annex D, but it uses an 
international numbering scheme. 

 
Be sure to configure the frame relay interface on the CES to use the same management 
protocol as the switched network to which it is connected.