User guide

Chapter 4—Configuring your VOIP
Multi-Tech Systems, Inc. 41
Field Name
Values
Description
Use Online
Alternate
Gatekeeper List
When selected, VOIP will seek an alternate gatekeeper (when none of the 3 gatekeepers shown on
this screen are available) from a list. The list will reside on the Primary gatekeeper or one of the
Alternate gatekeepers. The gatekeeper holding the list would download that list onto the VOIP
gateways within the system.
H.323 Version 4 Options
H.323 Multiplexing
Y/N
Signaling for multiple phone calls can be carried on a single port rather than opening a
separate signaling port for each. This conserves bandwidth resources.
H.245 Tunneling
(Tun)
Y/N
H.245 messages are encapsulated within the Q.931 call-signaling channel. Among other
things, the H.245 messages let the two endpoints tell each other what their technical
capabilities are and determine who, during the call, will be the client and who the server.
Tunneling is the process of transmitting these H.245 messages through the Q.931
channel. The same TCP/IP socket (or logical port) already being used for the Call Signaling
Channel is then also used by the H.245 Control Channel. This encapsulation reduces the
number of logical ports (sockets) needed and reduces call setup time.
Parallel H.245
(FS + Tun)
Y/N
FS (Fast Start) is a Q.931 feature of H.323v2 to hasten call setup as well as ‘pre-opening’
the media channel before the CONNECT message is sent. This pre-opening is a
requirement for certain billing activities. Under Parallel H.245 FS + Tun, this Fast Connect
feature can operate simultaneously with H.245 Tunneling.
Annex –E (AE)
Y/N
Multiplexed UDP call signaling transport. Annex E is helpful for high-volume VOIP system
endpoints. Gateways with lesser volume can afford to use TCP to establish calls.
However, for larger volume endpoints, the call setup times and system resource usage
under TCP can become problematic. Annex E allows endpoints to perform call-signaling
functions under the UDP protocol, which involves substantially streamlined overhead
(this feature should not be used on the public Internet due to potential problems with
security and bandwidth usage).
SIP
Session Initiation Protocol is the second option available for application layer control of the MultiVOIP. The fields
are detailed in the table below.
SIP call signaling