Version 5.2 123 September 2007
SIP User's Manual 5. Web-based Management
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 include the following:
îš„ Can fallback to internal routing table if there is no communication with the Proxy
servers.
 Call Restriction (when Proxy isn't used): rejects all outgoing TelÆIP calls that are
associated with the destination IP address: 0.0.0.0.
îš„ 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 is applied), the call is released.
îš„ 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.
îš„ Assign Profiles to destination address (also when a Proxy is used).
îš„ 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. The 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
'Configuring Alternative Routing (Based on Connectivity and QoS)' on page 351.
• 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 'Reasons for Alternative Routing' on page 130.
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'.
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