Support for Resource Availability Indication Over SIP Trunks

The Augmented Backus-Naur Form (ABNF) format of reporting is used to report the status of the report utilization to the monitoring entity. The Cisco IOS gateway may not use all the fields. Provision is also made for adding new resource types and new parameters for the resources.

The following is the format of the header used for reporting:

x-cisco-rai = ("x-cisco-rai") HCOLON resource-param *(COMMA resource-param)
resource-param = resource-name-param SEMI resource-params *(SEMI resource-params)
resource-name-param = "SYSTEM" / "CPU" / "MEM" / "DS0" / "DSP" / token
resource-params =  resource-status-param/resource-total-param/resource-available-param/resource-used-param/resource-extension
resource-status-param = "almost-out-of-resource" EQUAL ("true" / "false")
resource-total-param="total" EQUAL 1*(DIGIT) ["%" / "MB" / token]
resource-available-param = "available" EQUAL 1*(DIGIT) ["%" / "MB" / token]
resource-used-param = "used" EQUAL 1*3DIGIT "%"
resource-extension=generic-param

The rules for constructing the header are as follows:

• SYSTEM is a mandatory parameter that should be the first resource for a given device. Other resource-name-param values are optional parameters.
• The resource-identity-param parameter is a mandatory parameter within the SYSTEM resource-name-param parameter.
• At least one resource parameter (resource-params) should be present. If the resource-available-param parameter is present, the resource-total-param parameter should also be present so that the resource-used-param parameter can be calculated.
• For the SYSTEM resource-name-param parameter, the provision of a resource-status-param parameter is mandatory.

Following are the examples of the reporting format in the SIP OPTIONS message:

x-cisco-rai : SYSTEM; almost-out-of-resource=false
x-cisco-rai : CPU; almost-out-of-resource=false;total=100%;available=60%
x-cisco-rai : MEM; almost-out-of-resource=false;total=100%;available=40%
x-cisco-rai : DSO; almost-out-of-resource=false;total=64;available=20
x-cisco-rai : DSP; almost-out-of-resource=false;total=64;available=20

x-cisco-rai : SYSTEM; almost-out-of-resource=true
x-cisco-rai : CPU; almost-out-of-resource=true;total=100%;available=20%
x-cisco-rai : MEM; almost-out-of-resource=false;total=100%;available=40%
x-cisco-rai : DSO; almost-out-of-resource=false;total=64;available=20
x-cisco-rai : DSP; almost-out-of-resource=false;total=64;available=20

In gateway triggered reporting, the gateway sends the resource utilization information in an OPTION message to the external entity. The gateway includes a supported header with the option tag x-cisco-rai to indicate that this OPTION message carries the resource availability information. The trigger to send the OPTION message can be either periodic, or threshold based, or both.

• Periodic Reporting
• Threshold Triggered Reporting

In routing or monitor triggered reporting, the external entity can extract the resource information from the gateway using the SIP OPTIONS message. The gateway expects the x-cisco-rai tag in either the require: or supported: header fields for an incoming OPTIONS message. The presence of the x-cisco-rai tag in any one of the header fields informs the gateway that this option is to retrieve the gateway resource information.

The following is a sample format of the incoming OPTIONS message and the corresponding response from the Cisco IOS gateway for resource statistics request:

Received:OPTIONS sip:9.13.38.162:5060 SIP/2.0Via: SIP/2.0/UDP 9.13.40.83:5060;branch=z9hG4bK-21983-1-0From: <sip:9.13.40.83:5060>;tag=1To: sut <sip:service@9.13.38.162:5060>Call-ID: 1-21983@9.13.40.83CSeq: 1 OPTIONSContact: sip:sipp@9.13.40.83:5060Max-Forwards: 70Subject: Performance TestSupported: sec-agree, precondition
Require:  x-cisco-rai   Content-Type: application/sdpContent-Length: 0 

The following is a sample format of the OPTIONS message that is sent out from the Cisco IOS gateway to the external entity with resource statistics information in it:

Sent:OPTIONS sip:9.13.38.163:5060 SIP/2.0
Via: SIP/2.0/UDP 9.13.38.162:5060;branch=z9hG4bKE211D
From: <sip:9.13.38.162>;tag=1005B0-1CB
To: <sip:9.13.38.163>
Date: Wed, 16 Dec 2009 05:53:35 GMT
Call-ID: 2EE072F6-E93E11DE-801BBA85-BFCDE3D6@9.13.38.162
User-Agent: Cisco-SIPGateway/IOS-12.x
Max-Forwards: 70
CSeq: 101 OPTIONS
Contact: <sip:9.13.38.162:5060>
X-cisco-rai: SYSTEM ; almost-out-of-resource=true
X-cisco-rai: CPU ; almost-out-of-resource=false;available=99%;total=100%;used=1%
X-cisco-rai: DS0 ; almost-out-of-resource=false;available=23;total=23;used=0%
X-cisco-rai: DSP ; almost-out-of-resource=false;available=96;total=96;used=0%
X-cisco-rai: MEM ; almost-out-of-resource=true;available=51%;total=100%;used=49%
Supported: x-cisco-rai
Content-Length: 0

You can use the show voice class resource-group command to display the configuration parameters for monitoring gateway resources.

You can use the debug raicommand to enable debugging for RAI.