3Com V7122 User Manual page 84

Call Restriction – (when Proxy isn't used), reject all outgoing Tel IP calls that are
associated with the destination IP address: 0.0.0.0.
IP Security – When the IP Security feature is enabled (SecureCallFromIP = 1), the VoIP
gateway accepts only those IP Tel calls with a source IP address identical to one of the
IP addresses entered in the Telephone to IP Routing Table.
Filter Calls to IP – When a Proxy is used, the gateway checks the Tel IP routing table
before a telephone number is routed to the Proxy. If the number is not allowed (number
isn't listed or a Call Restriction routing rule was applied), the call is released.
Always Use Routing Table – When this feature is enabled (AlwaysUseRouteTable = 1),
even if a Proxy server is used, the SIP URI host name in the sent INVITE message is
obtained from this table. Using this feature, users are able to assign a different SIP URI
host name for different called and/or calling numbers.
Assign Profiles to destination address (also when a Proxy is used).
Alternative Routing – (When Proxy isn't used) an alternative IP destination for telephone
number prefixes is available. To associate an alternative IP address to called telephone
number prefix, assign it with an additional entry (with a different IP address), or use an
FQDN that resolves to two IP addresses. Call is sent to the alternative destination when
one of the following occurs:
No ping to the initial destination is available, or when poor Quality of Service (QoS)
(delay or packet loss, calculated according to previous calls) is detected, or when a
DNS host name is not resolved. For detailed information on Alternative Routing, see
Fax & Modem Transport
When a release reason that is defined in the 'Reasons for Alternative Tel to IP
Routing' table is received. For detailed information on the 'Reasons for Alternative
Routing Tables', see
Alternative routing (using this table) is commonly implemented when there is no response to
an INVITE message (after INVITE retransmissions). The gateway then issues an internal
408 'No Response' implicit release reason. If this reason is included in the 'Reasons for
Alternative Routing' table, the gateway immediately initiates a call to the redundant
destination using the next matched entry in the 'Tel to IP Routing' table. Note that if a domain
name in this table is resolved to two IP addresses, the timeout for INVITE retransmissions
can be reduced by using the parameter 'Number of RTX Before Hotswap'.
If the alternative routing destination is the gateway itself, the call can be configured
to be routed back to PSTN. This feature is referred to as 'PSTN Fallback', meaning
that if sufficient voice quality is not available over the IP network, the call is routed
through legacy telephony system (PSTN).
Tel to IP routing can be performed either before or after applying the number
manipulation rules. To control when number manipulation is done, set the
RouteModeTel2IP parameter. For information on this parameter, see
84
Modes.
Reasons for Alternative Routing.
V7122 GatewayUser Guide
Table 44.