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MultiVOIP User Guide Overview
35
H. 323, SIP, & SPP. Being H.323 compatible, the BRI MultiVOIP unit
can place calls to telephone equipment at remote IP network locations
that also contain H.323 compatible voice-over-IP gateways. It will
interface with H.323 software and H.323 gatekeeper units. H.323
specifications also bring to voip telephony many special features
common to conventional telephony. H.323 features of this kind that
have been implemented into the MultiVOIP include Call Hold, Call
Waiting, Call Identification, Call Forwarding (from the H.450 standard),
and Call Transfer (H.450.2 from H.323 Version 2). The fourth version of
the H.323 standard improves system resource usage (esp. logical port or
socket usage) by handling call signaling more compactly and allowing
use of the low-overhead UDP protocol instead of the error-correcting
TCP protocol where possible.
The MultiVOIP is also SIP-compatible. (“SIP” means Session Initiation
Protocol.) However, H.450 Supplementary Services features can be
used under H.323 only and not under SIP.
SPP (Single-Port Protocol) is a non-standard protocol developed by
Multi-Tech. SPP is not compatible with the “Proprietary” protocol used
in Multi-Tech’s earlier generation of voip gateways. SPP offers
advantages in certain situations, especially when firewalls are used and
when dynamic IP address assignment is needed. However, when SPP
is used, certain features of SIP and H.323 will not be available and SPP
will not inter-operate with voip systems using H.323 or SIP.
Data Compression & Quality of Service. The BRI MultiVOIP unit
comes equipped with a variety of data compression capabilities,
including G.723, G.729, and G.711 and features DiffServ quality-of-
service (QoS) capabilities.
PSTN Failover Feature. The MultiVOIP can be programmed to divert
calls to the PSTN temporarily in case the IP network fails.
Gatekeeper. At this writing, ISDN-BRI MultiVOIP systems can have
gatekeeper functionality only by adding, as an endpoint, a standalone
gatekeeper (special software residing in separate hardware).
Gatekeepers are optional but useful within voip systems. The
gatekeeper acts as the ‘clearinghouse’ for all calls within its zone.
MultiTech’s embedded and stand-alone gatekeeper software packages
both perform all of the standard gatekeepers functions (address
translation, admission control, bandwidth control, and zone
management) and also support many valuable optional functions (call
control signaling, call authorization, bandwidth management, and call
management). The stand-alone gatekeeper is, however, slightly more
feature-rich than the embedded gatekeeper. For more details, see the
“Embedded Gatekeeper” chapter of this manual and the manual on
MultiTech’s stand-alone gatekeeper.