User`s manual

MediaPack SIP
MediaPack SIP User’s Manual 180 Document #: LTRT-65405
is found; the prefix’s corresponding destination IP address is checked. If the destination IP
address is disallowed, an alternative route is searched for in the following table entries.
Destination IP address is disallowed if no ping to the destination is available (ping is continuously
initiated every 7 seconds), when an inappropriate level of QoS was detected, or when DNS host
name is not resolved. The QoS level is calculated according to delay or packet loss of previously
ended calls. If no call statistics are received for two minutes, the QoS information is reset.
The MediaPack gateway matches the rules starting at the top of the table. For this reason, enter
the main IP route above any alternative route.
8.7.2 Determining the Availability of Destination IP Addresses
To determine the availability of each destination IP address (or host name) in the routing table,
one (or all) of the following (configurable) methods are applied:
• Connectivity - The destination IP address is queried periodically (currently only by ping).
• QoS - The QoS of an IP connection is determined according to RTCP statistics of previous
calls. Network delay (in msec) and network packet loss (in percentage) are separately
quantified and compared to a certain (configurable) threshold. If the calculated amounts (of
delay or packet loss) exceed these thresholds the IP connection is disallowed.
• DNS resolution – When host name is used (instead of IP address) for the destination route, it
is resolved to an IP address by a DNS server. Connectivity and QoS are then applied to the
resolved IP address.
8.7.3 Relevant Parameters
The following parameters (described in Table 5-10) are used to configure the Alternative Routing
mechanism:
• AltRoutingTel2IPEnable
• AltRoutingTel2IPMode
• IPConnQoSMaxAllowedPL
• IPConnQoSMaxAllowedDelay
8.8 Mapping PSTN Release Cause to SIP Response
The MediaPack FXO gateway is used to interoperate between the SIP network and the
PSTN/PBX. This interoperability includes the mapping of PSTN/PBX Call Progress Tones to SIP
4xx or 5xx responses for IPÆTel calls. The converse is also true: For TelÆIP calls, the SIP 4xx
or 5xx responses are mapped to tones played to the PSTN/PBX.
When establishing an IPÆTel call the following rules are applied:
If the remote party (PSTN/PBX) is busy and the FXO gateway detects a Busy tone, it sends 486
busy to IP. If it detects a Reorder tone, it sends 404 not found (no route to destination) to IP. In
both cases the call is released. Note that if ‘DisconnectOnBusyTone = 0’ the FXO gateway
ignores the detection of Busy/Reorder tones and doesn’t release the call.
For all other MediaPack FXS/FXO releases (caused when there are no free channels in the
specific hunt group, or when an appropriate rule for routing the call to a hunt group doesn’t exist,
or if the phone number isn’t found), the MediaPack sends SIP response (to IP) according to the
parameter ‘DefaultReleaseCause’. This parameter defines Q.931 release causes. Its default
value is ‘3’, that is mapped to SIP 404 response. By changing its value to ‘34’ SIP 503 response
is sent. Other causes can be used as well.