User`s manual

MediaPack
SIP User's Manual 100 Document #: LTRT-65408
5.5.5.2 Tel to IP Routing Table
The Tel to IP Routing Table is used to route incoming Tel calls to IP addresses. This
routing table associates a called / calling telephone number’s prefixes with a destination IP
address or with an FQDN (Fully Qualified Domain Name). When a call is routed through
the VoIP gateway (Proxy isn’t used), the called and calling numbers are compared to the
list of prefixes on the IP Routing Table (up to 50 prefixes can be configured); Calls that
match these prefixes are sent to the corresponding IP address. If the number dialed does
not match these prefixes, the call is not made.
When using a Proxy server, you do not need to configure the Tel to IP Routing Table.
However, if you want to use fallback routing when communication with Proxy servers is
lost, or to use the ‘Filter Calls to IP’ and ‘IP Security’ features, or to obtain different SIP URI
host names (per called number) or to assign IP profiles, you need to configure the IP
Routing Table.
Note that for the Tel to IP Routing table to take precedence over a Proxy for routing calls,
set the parameter ‘PreferRouteTable’ to 1. The gateway checks the 'Destination IP
Address' field in the 'Tel to IP Routing' table for a match with the outgoing call. Only if a
match is not found, a Proxy is used.
Possible uses for Tel to IP Routing can be as follows:
 Can fallback to internal routing table if there is no communication with the Proxy
servers.
 Call Restriction – (when Proxy isn’t used), reject all outgoing TelÆIP 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 IPÆTel calls with a source IP address identical to
one of the IP addresses entered in the Tel to IP Routing Table.
 Filter Calls to IP – When a Proxy is used, the gateway checks the TelÆIP 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 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, refer to
Section 8.7 on page 231.
• 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’, refer to Section 5.5.5.5 on page 106
.
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’.