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DEFINITY ECS Release 8.2
Administrator’s Guide
555-233-506
Issue 1
April 2000
Features and technical reference
1590Wideband Switching
20
The terminal adapter also must adhere to the PRI-endpoint boundaries as
administered on the DEFINITY ECS switch when handling both incoming (to the
endpoint) applications and outgoing calls.
The terminal adapter passes calls to and receives calls from the line-side
ISDN-SETUP messages indicating the data rate and specific B-channels (DS0) to
be used and communicates all other call status information via standard ISDN
messages. Refer to DEFINITY Line-Side ISDN Primary Rate Interface Technical
Reference for more information.
Line-side (T1 or E1) ISDN-PRI facility
A line-side ISDN-PRI (T1 or E1) facility is comprised of a group of DS0s (24 for
a T1 facility and 32 for an E1 facility). In this context, these DS0s are also called
channels. T1 facilities have 23 B-channels and a single D-channel. E1 facilities
have 30 B-channels, 1 D-channel, and a framing channel. Data flows
bi-directionally across the facility between the switch and the ISDN-PRI terminal
adapter.
PRI-endpoints
A PRI-endpoint (PE) is a combination of DS0 B-channels on a line-side
ISDN-PRI facility that has been assigned an extension.
A PRI-endpoint can support calls of lower bandwidth. In other words, a PE having
a width 6 (six DS0s) can handle a call of one channel (64 Kbps) up to and
including six channels (384 Kbps). Also, a PE can support calls on non-adjacent
channels. For example, an endpoint application connected to a PE defined as using
B-channels 1 through 6 of an ISDN-PRI facility could originate a call using
B-channels 1, 3, and 5 successfully. If the PE has been administered to use flexible
channel allocation, the algorithm for offering a call to the PE starts from the first
DS0 administered to the PE. Since only one active call is permitted on a PE,
contiguous B-channels are always selected unless one or more B-channels are not
in service.
A PE remains in service unless all of its B-channels are out of service. In other
words, if B-channel 1 is out of service and the PE is five B-channels wide, the PE
could still handle a wideband call of up to four B-channels in width. A PE can
only be active on a single call at any given time; that is, it is either considered idle,
active (busy), or out of service.
One facility can support multiple separate and distinct PRI-endpoints (several
extensions) within a single facility. Non-overlapping contiguous sets of DS0s
(B-channels) are associated with each PE.