In this section:
This section describes several call routing mechanisms.
Username/SIP URI routing allows routing of requests based on the username and/or domain name in the SIP Request-URI. The username may be digits or an actual username. In either case, routing tries to find the most specific match for the (full) username and domain name, followed by less specific matches on suffixes of the domain name.
By default, the SBC Core applies the default time range profile “ALL” to a username route, which specifies all days and times.
The Standard destination based routing supports route lookups based on following parameters:
In a VoIP environment, subscribers can take their phone numbers outside of their original geographic location (local number portability) or use a VoIP adapter to make calls from a remote location. To make an emergency services available to subscribers not tied to fixed geographic locations, Enhanced 911 tracks caller location and the Public Services Answering Point nearest to them by means of a VoIP Positioning Center (VPC).
The SBC supports Enhanced 911 emergency services using both IPv4 and IPv6 IP addresses when sending Emergency Services Routing requests to an external VPC. The VPC reply contains the routing information for the appropriate emergency services dispatcher nearest the VoIP subscriber dialing 911. SIP to SIP-I call routing is also supported.
SBC standard routing performs a leading digits prefix match to determine the best route available. Routes are defined based on either the entire called number or the leading digits of the number.
The SBC supports the capability to configure test routes for routes simulation using the ‘routingLabelRoute’ parameter and ‘testing’ sub-parameter of global call routing feature.
CLI command example:
% set global callRouting routingLabel 1 routingLabelRoute 2 testing test
Where testing parameter has three options:
The SBC supports route prioritization in a routing label based on the methods:
The HD codec based prioritization method is invoked after executing the existing route prioritization methods.
The HD Codec Based Routing works only with a centralized PSX.
HD codec based prioritization is an end-to-end routing feature on the ingress offer. To configure the codec priority to remain constant throughout SBC processing (e.g., wide band remains the highest priority codec), enable the following settings in Packet Service Profile screen.
Use a wideband codec with Ingress Route PSP to facilitate end-to-end wideband calls. Any deviation from the above settings may not prioritize the route appropriately.
In Codec based prioritization, the PSX prioritizes the egress routes for the following High Definition (HD) codecs:
The PSX receives the list of HD codecs and their sampling rates in the policy request sent by the SBC. If the ingress PSP contains any of the above mentioned HD codecs, then the PSX reorders the egress routes as follows:
If the ingress PSP does not contain any of the above mentioned codecs, then the PSX configures the routes normally based on the existing logic.
A SIP-to-PSTN gateway can have trunks connected to different carriers. Plus, a SIP proxy may choose (based on proprietary routing logic) a carrier in which a call is sent when it proxies a session setup request to the gateway. Since, multiple carriers can transport a call to a particular phone number, a phone number by itself is not sufficient to identify the carrier at the gateway. To overcome this, the ERE routing logic uses “tgrp” and “trunk-context” parameters in the Request URI header as described below.
The SBC supports processing Destination Trunk Group (DTG) and Originating Trunk Group (OTG) parameters received in Contact and Request-URI messages, and transparently passing this information or inserting it in response messages or egress INVITE headers. When configured this way, even if OTG or DTG values are included in the received messages they are not used in processing of trunk group values for response and egress.
When configuring the SBC for DTG routing, trunk group names must use all UPPERCASE letters.
If the PES receives destination trunk group parameters (tgrp and trunk-context) in the policy request and if “Process Destination Tgrp” and “Process Destination Trunk Context” flags are enabled for the ingress trunk group, PES performs a light policy lookup and skips full policy dip. In this scenario, the ERE uses the trunk group name received in the tgrp parameter (similar to the dtg parameter). Also, the trunk-context parameter value is ignored. If DTG is present, it is also ignored.
The IP address is unique within a zone. To perform a reverse lookup against an IP peer, the IP address and zone are required. When trunk-context contains an IP address, use a default zone to look up the IP peer.
Two options are available to identify the zone name:
Since the local trunk group is not returned in the policy response, the local trunk group in the zone is determined by the SBC to ensure the call is sent to the destination IP Peer. The Trunk Resource Manager (TRM) looks up the Network Selector Table (NST) associated with the zone to determine the local trunk group.
After determining IP peer based on the trunk-context, the zone name to which this IP peer belongs is determined by fetching IP peer table. The ERE can send back the egress zone information in the policy response by populating zone ID in the zoneIndex attribute in the route4Attributes table.
A CLI configuration example is shown below.
Allow processing of “tgrp” and “trunk-context” for feature control profile “DEFAULT_IP”:
% set profiles featureControlProfile DEFAULT_IP processDestinationTrunkGroupAndTrunkContext enable
Associate the profile with a SIP trunk group:
% set addressContext default zone defaultSigZone sipTrunkGroup DEFAULT_TG policy featureControlProfile DEFAULT_IP
Trunk Groups are identified by two parameters: tgrp and trunk-context
.
The trunk-context
establishes the scope of the trunk group specified in the tgrp
parameter and determines if it is for a single gateway, a set of gateways, or an entire domain managed by the service provider.
The value in the trunk-context
identifies a gateway.
When the remote party sends the invite with both tgrp =
egress_tg, trunk_context
= Egress IP / Egress IP + Port / FQDN
, the SBC chooses the egress trunk group based on the tgrp
parameter in the Request-URI (R-URI). The SBC uses the trunk-context as destination, if there is no IP Peer or IP Signaling Peer Group is not configured.
The SBC does not provision the IP peer when the remote IP address is already provisioned in some other system and the user does not want duplicate provisioning, or when the user does not know the remote IP address.
A zone cannot have two trunk groups with the same ingress prefix information, but two different trunk group can be used towards the same destination.
You can use a trunk group for multiple destinations without having the IP address in its list of ingress prefixes.
How it works
When you disable processTgrpContext
at the SBC, the SBC sends tgrp
and trunk-context
to the PSX.
In this case, when you enable the processDestinationTgrp
in Feature Control Profile, the PSX does light policy lookup and skips all the SSG-based services, number translation, and routing functions.
If you configure the ipSignalingPeerGroup
in the Trunk Group, the SBC routes the request to the configured ipSignalingPeerGroup
.
If you do not configure the ipSignalingPeerGroup/ipPeer
in the Trunk Group and the trunk-context
is available, then the SBC routes the request to trunk-context.
Prior to SBC 8.0, the SBC supported the tgrp/trunk-context
functionality in R-URI for INVITE only. The SBC now supports the tgrp/trunk-context
functionality in R-URI for NON-INVITE messages (same as DTG).
The light dip principle instructs the Diameter+ PSX to skip most of the services and return a single route for the specified trunk group. This is useful for networks where an upstream SIP device (for example, the PSX Proxy which anchors the SIP session) performs crank back / route advance and sends the profile.
For more information, refer to the following PSX documents:
The SBC uses the R-URI tgrp/trunk-context as a replacement for the Destination Trunk Group (DTG) parameter. With this enhancement, the SBC treats the tgrp
parameter for INVITE and NON-INVITE transactions ( the same as if it received the DTG parameter) allowing a light dip at the D+ PSX, for all INVITE and NON-INVITE out-of-dialog SIP transactions.
The following figure depicts the example of NON-INVITE OOD transaction.
When configuring the SBC for DTG routing, trunk group names must use all UPPERCASE letters.
The SBC is capable of routing calls to an ASX or SIP Server using defaultSigZone, a named IP trunk group and a sipSigPort in the defaultSigZone.
When the SBC queries the PSX for routing a call to the ASX/SIP Server (no zone or Zone Index 0 configured on the PSX), the ASX/SIP Server IP address, virtual trunk group and Zone Index 0 is returned in the response. The SBC will map PSX Zone Index 0 to the SBC defaultSigZone
, and use customer-provisioned named sipTrunkGroup (the ingress IP Prefix of which matches the ASX/ SIP Server IP address) and customer-provisioned sipSigPort in the defaultSigZone for routing the call.
Example:
SIP Trunk Group
% set addressContext default zone defaultSigZone sipTrunkGroup defaultSipTrunkGroup ingressIpPrefix 10.7.6.40 32 % set addressContext default zone defaultSigZone sipTrunkGroup defaultSipTrunkGroup media mediaIpInterfaceGroupName DLIG % set addressContext default zone defaultSigZone sipTrunkGroup defaultSipTrunkGroup state enabled mode inService
SIP Signaling Port
% set addressContext default zone defaultSigZone sipSigPort 1 ipAddressV4 10.7.15.146 portNumber 5060 transportProtocolsAllowed sip-udp % set addressContext default zone defaultSigZone sipSigPort 1 ipInterfaceGroupName DLIG % set addressContext default zone defaultSigZone sipSigPort 1 mode inService state enabled
Refer to Zone - SIP Trunk Group - CLI for command syntax and parameter descriptions.
The SBC Core also supports multiple named non-routable IP trunk groups created in the defaultSigZone for GW-GW, SIP Servers/ASX SIP Core routing and H.323 calls. The following routes are supported in defaultSigZone and default addressContext:
(SIP hop-by-hop routing and SIP core optimized routing)