E-11
3170-A2-GB20-20
December 1996
The DS1 Fractional Group, DS1/E1 MIB
The DS1 Fractional group consists of the DS1
fractional table. This table (dsx1FracTable) is fully
supported by the E1 DSU/CSU and allows channel (time
slots) to be mapped between the E1 interfaces and data
ports. If an invalid channel map (e.g., two interfaces
mapped to a single time slot, one interface mapped to two
E1s, etc.) is received, an error is returned to the SNMP
manager. The E1 DSU/CSU validates all channel
configurations before applying them.
Operational Note: The fractional E1 group only allows
specification of an entire interface to a particular time slot
on another interface (i.e., a time slot on one interface
cannot be mapped to a time slot on another interface).
This prevents complete mapping of time slots on the DTE
Drop/Insert interface to time slots on the network E1
interface. For mapping time slots between the network
and DTE E1 interfaces, the following convention is used:
Time slots on the E1 interface that are mapped to another
E1 interface (i.e., not a data port) are connected in
ascending order. For example, if the fractional table for
the network E1 interface maps time-slots 1, 3 and 5 to the
DTE E1 interface and the DTE E1 interface maps time
slots 10, 11 and 15 to the network the following time slots
are connected: N1 to D10, N3 to D11, and N5 to D15.
When time-slot 16 is reserved for signaling, allocated
DTE channels must be mapped to the corresponding
network channels (e.g., D1 to N1, etc.), otherwise an error
is returned to the SNMP manager.
RS-232-like MIB (RFC 1317)
The “rs232” object defined by RFC 1317 is supported
for all of the synchronous data ports, the COM port, and
the AUX port. The RS-232-like MIB consists of one
object and five tables, as follows:
•
Number of RS-232-like ports
•
The General Port Table
•
The Asynchronous Port Table
•
The Synchronous Port Table
•
The Input Signal Table
•
The Output Signal Table
The Asynchronous Port table is not supported by the
E1 DSU/CSU for the synchronous data ports. The Input
Signal and Output Signal tables are not supported for the
AUX and COM ports. The following sections provide
clarification for objects contained in the RS-232-like MIB
when it is not clear how the object definition in MIB is
related to the E1 DSU/CSU.
Number of Ports – “rs232Number” Object
(rs232 1)
This object contains the number of ports in the
RS-232-like general port table. This number is 4 for the
3172 DSU/CSU and 6 for the 3174 DSU/CSU.
General Port Table, RS-232-like MIB
The general port table contains general configuration
objects for the RS-232-like interfaces.
General Port Table – “rs232PortIndex” Object
(rs232PortEntry 1)
This object contains a unique value for each port and is
used as an index into the general port table
(rs232PortTable). The values of the rs232PortIndex object
vary between models and are listed below.
The values of rs232PortIndex for the 3172 DSU/CSU
are:
•
1 – COM port
•
2 – Auxiliary RS-232 port
•
3 – DCE port 1
•
4 – DCE port 2
The values of rs232PortIndex for the 3174 DSU/CSU
are:
•
1 – COM port
•
2 – Auxiliary RS-232 port
•
3 – DCE port 1
•
4 – DCE port 2
•
5 – DCE port 3
•
6 – DCE port 4
