DEFINITY Enterprise Communications Server Release 7
Maintenance for R7r
555-230-126 Issue 4
June 1999
Maintenance Architecture
1-31Protocols
1

Usage

The following is a list of the protocols when d ata is transmitted to and through th e
system. The list is organized by p rotocol layers. Refer to Figure 1-9.

Layer-1 Protocols

Layer-1 protocols are used b etween the terminal or host DTE and the DCE, used
between the DCE equipment and t he system port, and used insid e the system.
The following layer-1 protocols are used between the DTE equipment and the
DCE equipment. DCE equipment can b e data modules, modems, or Da ta
Service Units (DSUs). A DSU is a device that transmits d igital data to a partic ular
digital endp oint over the public network without p rocessing the data throug h any
intervening private network switc hes.
â– 

RS-232

— A common physical inter face used to connect DTE to DCE.
This protocol is typically used for communicating up to 19.2 kbps
â– 

RS-449

— Designed to overcome the RS-232 distanc e and speed
restrictions and lack of mod em control
â– 

V.35

— A physical interface u sed to connect DTE to a DCE. This protocol
is typically used for tr ansmissions at 56 or 64 kbps
The following protocols are used at layer 1 to govern communic ation between the
DCE equipment and the port. These protocols consist of codes inserted at the
originating DCE and stripp ed at the port. The DS1 protocol c an be inserted at the
originating, outgoing trunk port and strip ped at the destination p ort.
â– 

Digital Communications Protocol (DCP)

— A standard for a 3-channel link.
This protocol sends dig itized voice and d igital data in frames at 160 kbp s.
The channel structure consists of two information (I) channels and one
signaling (S) channel. Each I-c hannel provides 64 kbp s of voice and/or
data communication an d the S-channel provides 8 kb ps of signaling
communication between the s ystem and DTE equipment. DCP is similar to
ISDN-BRI
â– 

Basic Rate Interface (BRI)

— An ISDN standard for a 3-channel link,
consisting of two 64-kbp s bearer (B) channels and one 16-kb ps signaling
(D) channel. For the implementation of this stand ard, see

DEFINITY

Communications System and System 75 and System 85 ISDN BRI

Refere nce

, 555-025-103
â– 

Primary Rate Interface (PRI)

— An ISDN standard that sends dig itized
voice and dig ital data in T1 frames at 1.544-Mbps or, for c ountries outside
the United States, in E1 frames at 2.048-Mbps. Layer 1 (p hysical), layer 2
(link), and layer 3 (network) ISDN PRI protocols are defined in

AT&T

System 75 and 85

—

DS1/DMI/ISDN-PRI

—

Reference Manual

,
555-025-101. At 1.544 Mbps, eac h frame consists of 24 64-kbps channels
plus 8 kbps for framing . This represents 23 B-channels plus 1 D-c hannel.