Reason Header - Local/Remote Resource Availability

1 Call Flow Diagrams
- 1.1 Example 1
- 1.2 Example 2
2 Call Trace
3 Configuration
- 3.1 Configure SIP SGP Profile
- 3.2 Create SIP Channel Group
- 3.3 Create an External Gateway
4 Additional Information

Before the introduction of the Reason Header - Local/Remote Resource Availability feature, if there were no resources available on the outgoing TDM side, the IMG 2020 would respond to the incoming SIP network with a 503 Service Unavailable response. The 503 response sent would not give any indication whether the IMG 2020 itself was out of resources or whether the SS7 network was out of resources. With the introduction of this feature, a user can distinguish whether the 503 Service Unavailable response sent to the SIP network was caused due to a lack of resources on the IMG 2020 or lack of resources in the outgoing SS7 network. Refer to the links in the Related Topics section below.

Call Flow Diagrams

With the feature enabled, the next 2 examples display the functionality of the feature.

Example 1

The call flow diagram below displays what happens when the IMG 2020 is out of resources. In a SIP to SS7 call, if the 2020 there are no available DS-0s on the outgoing side, the IMG 2020 will respond to the incoming SIP side with a 503 Service Unavailable. In this example the Reason-header in the response will display the following details: Reason: Q.850; cause=34; text=”No Circuit/Channel Available,Local

Example 2

The call flow below displays what happens when the SS7 Network is out of resources. In a SIP to SS7 call, the SS7 Network responds with a cause code of 34 when it is out of resources. When the IMG 2020 receives the REL with cause code 34 from the SS7 network side, it will respond to the incoming SIP network with a 503 Service Unavailable response to the incoming SIP side. The Reason-Header in the response will display the following Reason-Header details: Reason: Q.850; cause=34; text=”No Circuit/Channel Available.

Call Trace

The Call Trace below is from example 1 above where the resources on the IMG 2020 are unavailable.

17:04:16.083 CALL(L4)  (00:00018:00) SENT Route Control Rej to SIP
17:04:16.083 CALL(SIP) (00:00018:00) RCVD Route Control Rej from L4
17:04:16.083 CALL(SIP) (00:00018:00) NO CHANNEL AVAILABLE!!!
17:04:16.083 CALL(SIP) (00:00018:00) Reason Hdr: "No circuit/channel available,Local"
17:04:16.083 CALL(SIP) (00:00018:00) Channel query rejected
17:04:16.083 CALL(SIP) (00:00018:00) SENT 503 Service Unavailable to 10.129.39.
                       101:8000 Cseq:1
17:04:16.083 CALL(SIP) (00:00018:00)
                        <--- [10.129.39.101, 8000 <- 10.129.39.51, 5060]
                       SIP/2.0 503 Service Unavailable [Channel query rejected]
                       \r\n
                       Via: SIP/2.0/UDP 10.129.39.101:8000;received=10.129.39.101\r\n
                       Call-ID: 1-8464@10.129.39.101\r\n
                       From: "1111" <sip:anonymous@10.129.39.101:8000>;tag=1\r\n
                       To: 3333 <sip:3333@10.129.39.51:5060>;tag=a94c095b773be1
                       dd6e8d668a785a9c842326ff21\r\n
                       Contact: <sip:3333@10.129.39.51:5060>\r\n
                       CSeq: 1 INVITE\r\n
                       Server: Dialogic-SIP/10.5.3.83 img51 0\r\n
                       Reason: Q.850 ;cause=34 ;text="No circuit/channel available,Local"\r\n
                       Content-Length: 0\r\n
                       \r\n

Configuration

Below are instructions on how to configure the functionality for this feature. Before configuring, an initial configuration must be created on it. Refer to the Basic Configurations procedure and verify the required basic functionality has been configured prior to configuring this feature. Also, the feature is supported when going from a SIP network to an SS7 network which requires both SS7 and SIP signaling to be configured. Refer to the Configure SS7, Configure SIP (Multiple SIP IP) or Configure SIP (Single SIP IP) topics as required.

Configure SIP SGP Profile

Configure a SIP Profile and enable the Reason Header Local field.

Right click on the Profiles object and select New SIP Profiles. The SIP Profiles object is a parent or container object and no configuration is required in this object. Refer to the SIP Profiles topic for more information on this object.
Right click on the Profiles object again and select New SIP Profile. The first SIP Profile created is a default profile and cannot be modified. Disregard this profile.
Right click on the Profiles object again and select New SIP Profile. In the Name field, enter a name that describes the SIP Profile being created. In this procedure the SIP Profile was labeled SIP_Prof_ReasonHeader. Refer to SIP Profile - SGP topic for more information on configuring the remaining fields within this object.
Right click on the SIP Profile created and select New SIP Headers. To enable the feature, select Enable in the drop down menu of the Reason-header Local field. Refer to the screen capture below.

Create SIP Channel Group

Create a SIP channel group and link the SIP profile just created to it.

Right click on the Routing Configuration object and select New Channel Groups. The Channel Groups object is a container object for multiple channel group objects and no configuration is required here. Refer to the Channel Groups topic for more information on this object.
Right click on Channel Groups object and select New Channel Group. In the Name field, enter a name that describes the channel group being created.
Set the Signaling Type field to SIP. Refer to Channel Group topic for more information on configuring the remaining fields in the SIP Channel Group object.

Create an External Gateway

The external gateway being created will communicate with the SIP channel group configured above.

Right click on the Dialogic object and select New External Network Elements. The External Network Element pane is a parent or container object and no configuration is required here. Refer to External Network Elements topic for more information on this object.
Right click on the External Network Elements object and select New External Gateways. Again, the External Gateways object is a container or parent object and no configuration is needed here. Refer to External Gateways topic for more information on this object.
Right click on External Gateways object and select New External Gateway. Refer to screen capture below.

Field Descriptions

In the Name field, enter a name to identify the gateway being configured. In this procedure ReasonHeader_GW was entered.
Select SIP from the Gateway Signaling Protocol field drop down menu.
Enter an IP address in the Gateway IP Address field.
In the SIP Profile field, select the Reason Header Profile created earlier. Refer to the topic for more information on configuring the remaining fields.

Right click on the SIP channel group created earlier and select New IP Network Element. Select the gateway configured above from the drop down menu.

The feature, at this point, has been configured on the SIP side. The TDM channel group can now be configured along with routing and translations.

Additional Information

This feature is applicable when the outgoing side is out of resources (SS7 CICs). The reason header is not sent in the ‘503 Service Unavailable’ message when the IMG 2020 is out of resources on the incoming side (IP channels).
This feature is applicable for only the Release reason cause 34 on a SIP to SS7 call.

Dialogic Integrated Media Gateways