IMG 1010 - Local/Remote cause code 34 in Reason Header
- Kelli Higdon
Before the introduction of feature F-5761, if there were no resources available the IMG would send out a 503 Service Unavailable message to the incoming SIP network informing the SIP entity that there were no resources available. The 503 message sent would not give any indication as to whether the IMG itself was out of resources or whether the SS7 network on the outgoing side was out of resources. With the introduction of this feature, a user can distinguish whether the release “503 Service Unavailable” sent by IMG to the SIP entity was caused due to the IMG being out of resources or the outgoing SS7 network is out of resources. This feature will be disabled by default.
Call Flow
With the feature set to Enabled the next two examples display the functionality of the feature.
Example 1
The call flow below displays when the IMG is out of resources and the feature is enabled. In a SIP to SS7 call, when IMG detects no channel at the outgoing side, it shall send “503 Service Unavailable” to the SIP side with Reason-header having the following details: “Reason: Q.850; cause=34; text=”No Circuit/Channel Available, Local”
Example 2
The call flow below displays what is sent back to the SIP network when the SS7 network is out of resources and a cause code of 34 is sent to the IMG. In a SIP to SS7 call, when IMG receives REL with cause code 34 from the SS7 network side, it shall send “503 Service Unavailable” to the SIP side with Reason-header having the following details: “Reason: Q.850; cause=34; text=”No Circuit/Channel Available”
Call Trace
The call trace below is the call trace from Example 1 above where the resources on the IMG 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=a94c095b773be1dd6e8d668a785a9c842326ff21\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 IMG to send a Reason Header to the incoming SIP entity displaying whether the call failed because resources were not available on the IMG or not available in the SS7 network.
Configure these initial objects before proceeding to the procedure below:
Create SIP Profile and SIP Headers object.
Right click on the Profiles object and select New SIP SGP. Modify the SIP Profile Id field so the ID is something other than ID:0. Once ID:0 is changed then the rest of the fields can be modified. Refer to the IMG 1010 - SIP Profile - 10.5.3 topic for more information on configuring this object.
Note: Profile Id:0 is a default ID and the fields cannot be modified while the ID is left as ID:0.
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. See screen capture below.
Create SIP Channel Group
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. Refer to the IMG 1010 - Channel Groups object for more information.
Right click on Channel Groups object and select New Channel Group. Set the Signaling Type field to SIP and enter a name for this channel group. Refer to IMG 1010 - Channel Group topic for more information on configuring a SIP Channel Group.
Create External SIP Gateway
Right click on IMG EMS and select New External Network Elements. No configuration is accomplished here. The External Network Element pane is a parent object to multiple external entities in the network. Refer to IMG 1010 - External Network Elements topic for more information.
Right click on the External Network Elements object and select New External Gateways. Again, no configuration is accomplished here. Refer to IMG 1010 - External Gateways object for more information.
Right click on External Gateways object and select New External Gateway. Enter a name to identify this gateway, modify the Gateway Signaling Protocol field to display SIP, and enter an IP address in the Gateway IP Address field. Refer to the IMG 1010 - External Gateway topic for more information on configuring the gateway object.
In the SIP Profile field, select from the drop down menu, the SIP Profile created earlier . Within the SIP Profile field select the SIP SGP created above for the Local/Remote cause code feature. See screen capture below.
Right click on the SIP channel group created earlier and select New IP Network Element. Select the gateway created above that has the Generic Notification SIP SGP associated with it.
At this point the feature has been configured. Routing and translations can now be accomplished.
Additional Information
This feature is applicable only when the IMG outgoing side (SS7 CICs) are out of resources. No reason header is sent in ‘503 Service Unavailable’ when the IMG incoming side (IP channels) is out of resources.
This feature is applicable for only Release reason 34 and SIP to SS7 calls.