B-13
Appendix B: Glossary
DB/E-9 A nine-pin serial connector with a roughly trapezoidal (D) shape. This
connector is often used for serial interfaces.
D-sub 9 connector
DB-25 A 25-pin D-shaped serial connector. This connector is often used with printer
serial cables and serial connections.
DB-25 connector
DCE Data Communications Equipment. A device that communicates with a DTE
device. In a Frame Relay network, the DCE is the Frame Relay switch, which
establishes and maintains the Frame Relay connection. When the DCE
receives frames from the DTE, it converts the frames into signals supported
by the physical media of the Frame Relay network. The DCE also reads the
DLCI on incoming packets, checks its switch lookup table, and then forwards
data to the appropriate outgoing port—which leads to the correct virtual
endpoint. See also DTE.
DE bit Discard Eligibility bit. A Frame Relay header mark indicating that a particular
frame may be discarded in preference to other frames if congestion occurs.
When a subscriber exceeds the CIR, the packets transmitted over the CIR are
marked with the DE bit. See also CIR.
Decryption The process of decoding data that has been encrypted. Decryption requires a
string of characters, called a key, and an algorithm.
15
69
D-sub 9 male
D-sub 9 female
51
96
113
14 25
DB-25 male DB-25 female
13 1
25 14
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