Avaya Communication Manager Administrator's Manual page 1772

Feature Reference
Wideband Switching
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Flexible — In the flexible scheme, an N x DS0 call is placed on any set of B-channels as long as
the requested bandwidth is satisfied. There is absolutely no constraint such as contiguity of
B-channels or fixed starting points. Of course, as with all wideband calls, all the B-channels
comprising the wideband call must reside on the same ISDN facility.
Regardless of the allocation scheme employed, the N x DS0 algorithm, like the H11 and H12
algorithms, attempts to preserve idle facilities when offered B, H0, and N x DS0 calls. This is
important so that N x DS0 calls, for large values of N, have a better chance of being satisfied by a
given trunk group. However, if one of these calls cannot be satisfied by a partially-contaminated
facility and an idle facility exists, a trunk on that idle facility is selected, thus contaminating that
facility.
There are additional factors to note regarding specific values of N and the N x DS0 service:
— N = 1 — this is considered a narrowband call and is treated as any other voice or
narrowband-data (B-channel) call.
— N = 6 — if a trunk group is optioned for both H0 and N x DS0 service, a 384-kbps call
offered to that trunk group is treated as an H0 call and the H0 constraints apply. If the H0
constraints cannot be met, then the call is blocked.
— N = 24 — if a trunk group is optioned for both H11 and N x DS0 service, a 384-kbps call
offered to that trunk group is treated as an H0 call and the H0 constraints apply. If the H0
constraints cannot be met, then the call is blocked.
— N = 24 — if a trunk group is optioned for both H11 and N x DS0 service, a 1,536-kbps call
offered to that trunk group is treated as an H11 call and the H11 trunk allocation
constraints apply.
— N = 30 — if a trunk group is optioned for both H12 and N x DS0 service, a 1,920-kbps call
offered to that trunk group is treated as an H12 call and the H12 trunk allocation
constraints apply.
Glare prevention
Glare occurs when both sides of an ISDN interface select the same B-channel for call initiation. For
example, a user side of an interface selects the B-channel for an outgoing call and, before
Communication Manager receives and processes the SETUP message, it selects the same B-channel for
call origination. Since wideband calls use more channels, the chances of glare are greater. Glare
conditions can be limited with proper channel administration, but they may never be eliminated and some
calls may still be dropped.
Some glare situations might not be resolvable. In one case, the network and the user side may send
SETUP messages simultaneously or nearly simultaneously. Another glare scenario can occur in the brief
window after the SETUP message has been sent but before the first response is received from
Communication Manager at the other side of the interface. If an incoming SETUP arrive during this
window, the incoming SETUP message is allowed to proceed and the outgoing call is dropped. Various
glare situations and their resolution are described in the following table.
Communication Manager does not negotiate channels for wideband calls.
1772 Administrator's Guide for Avaya Communication Manager
November 2003