Maintenance strategy
Protocols
36
Maintenance Procedures
December 2003
Both the physical-layer protocol and the Digital Multiplexed Interface (DMI) mode used in the
connection are dependent upon the type of 8-bit code used at layer 2 between the DTE and DCE
equipment, as listed in
Table 7, Physical-layer protocol versus character code,
on page 36 and
Digital Multiplexed Interface (DMI) mode versus character code,
Connectivity rules
Figure 3, Intra-port and Inter-port data transmission states,
on page 33 implies the following connectivity
rules:
•
Only the DS1 port and the analog trunk port are trunking facilities (every other port is a line port).
For communication over these facilities, the destination DCE equipment can be a hemisphere
away from the system, and the signal can traverse any number of intervening switching systems
before reaching the destination equipment.
•
Data originating at any type of digital device, whether DCP or BRI, can exit the system at any
type of digital port — BRI, digital-line, PRI, DS1, and others; as long as the call destination is
equipped with a data module using the same DMI mode used at the call origin. This is because
once the data enters the system through a digital port, its representation is uniform (raw bits at
layer 1, and DMI at level 2), regardless of where it originated.
•
Although data entering the system through an EIA port has not been processed through a data
module, the port itself has a built-in data module. Inside the system, port data is identical to
digital line data. Data entering the system at a DCP line port can exit at an EIA port. Conversely,
data entering the system at an EIA port can exit at any DCP line port. The destination data
module must be set for Mode-2 DMI communication.
•
Voice-grade data can be carried over a DS1 facility as long as the destination equipment is a
modem compatible with the originating modem.
•
If a mismatch exists between the types of signals used by the endpoints in a connection (for
example, the equipment at one end is an analog modem, and the equipment at the other end is a
digital data module), a modem-pool member must be inserted in the circuit. When the endpoints
are on different switches, it is recommended that the modem-pool member be put on the
Table 7: Physical-layer protocol versus character code
Protocol
Code
RS-232
Asynchronous 8-bit ASCII, and synchronous
RS-449
Asynchronous 8-bit ASCII, and synchronous
V.35
Synchronous
Table 8: Digital Multiplexed Interface (DMI) mode versus
character code
DMI Mode
Code
0
Synchronous (64 kbps)
1
Synchronous (56 kbps)
2
Asynchronous 8-bit ASCII (up to 19.2 kbps), and synchronous
3
Asynchronous 8-bit ASCII, and private proprietary
Summary of Contents for CMC1
Page 1: ...Maintenance Procedures 555 245 103 Issue 1 1 December 2003 ...
Page 14: ...Contents 14 Maintenance Procedures December 2003 ...
Page 416: ...Additional maintenance procedures IP Telephones 416 Maintenance Procedures December 2003 ...
Page 426: ...Index X 426 Maintenance Procedures December 2003 ...
