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iSPAN Serial WAN Adapter Users Guide 199
(ANSI) Standard T1.618 and the International Telegraph and Tele-
phone Consultative Committee (CCITT) Standard Q.922, indicates the
functions associated with certain DLCI values:
DCD (Data Carrier Detect) ◆ See CD (Carrier Detect).
DCE (Data Communications Equipment, Data Circuit-Terminating
Equipment)
◆ Equipment that provides the functions required to
establish, maintain, and terminate a connection (including signal con-
version) for communications between the data terminal equipment and
the telephone line or data circuit. Also, interface signals typically pre-
sented by this equipment.
D Channel ◆ Standard channel on an ISDN PRI or BRI line. At 16
Kbps, a D channel carries all signalling information and can carry low-
speed packet data such as X.25 packet switching.
DE ◆ See Discard Eligibility (DE).
Demarc (Demarcation Point) ◆ The point on a customer's premises
where the line from the telephone company meets the customer's wir-
ing at the customer's premises.
DFT ◆ See Distributed Function Terminal (DFT).
Directory Number ◆ Your seven-digit telephone number (without the
area code), as found in the telephone directory. Each BRI connection
can have up to two Directory Numbers, one for each B channel.
Discard Eligibility (DE) ◆ A bit indicating that a frame may be dis-
carded in preference to other frames if congestion occurs to maintain
the committed information rate. See also Excess Burst Size and CIR.
DLCI Values Function
0 In-channel signalling
1-15 Reserved
16-991 Assigned using frame-relay connection procedures
992-1007 Layer 2 management of frame-relay bearer service
1008-1022 Reserved
1023 In-channel layer management