IMG 1010 - SIP Options Keep Alive Overview - Busy Out

The IMG can monitor the status of external SIP gateways by sending periodic SIP OPTIONS messages. If the gateway does not respond to one OPTIONS message the gateway will be considered down or unreachable and attempt to re-route the call to a different gateway. Once the gateway is down or considered unreachable it will take the configured amount of responses to show the gateway as UP or Reachable.

RFC

RFC 3261 SIP: Session Initiation Protocol, Section 11.

Configuration

Enable the SIP Busy Out feature on a specific gateway by executing the following.

If the Options Keep Alive property is enabled, disable it before changing other Properties in the SIP External Gateway object. Then, re-enable it once the other changes have been made. This sequence will insure the IMG is configured correctly.

In the External Gateway Pane in Clientview select "enable" from the drop down menu in the "SIP Options Keep Alive" field. See below.
10.3.3

10.5.0
Once the Options Keep Alive is enabled then the Parameters can be configured. Right click on SIP SGP profiles object pane and select New Options Keep Alive and the SIP Options Keep Alive pane will appear.

Number of Responses

Number of responses received before marking the gateway as reachable. Drop down menu has selections from 1 to 10 (Default 3).

Up Timer (s)

Timer to define the interval the IMG will send the OPTIONS message to the gateway when the gateway up and responsive. Timer is in seconds (Default=120 seconds)

Down Timer (s)

Timer to define the interval the IMG will send the OPTIONS message to the gateway when the gateway is down or non responsive. Timer is in seconds (Default=30 seconds)

EventView Alarm

A SIP gateway Alarm that will appear in both EventView and alarm.log. The alarm indicates the status of a particular SIP Gateway. This alarm will contain the status (either 'unreachable' or 'reachable') and the IP address of the Gateway. The SIP Gateway Alarm is first sent if the Gateway is considered 'unreachable'. Below are samples of the alarm messages

SIP Gateway Alarm

Sep 19 2007 11:08:36.838 X0\[88.235.44.169]\->H : 00 b9 04 0a 00 03 0a 04 07 00 04 07 cc 09 c9 4a

Sep 19 2007 11:08:36 **Major: Node 0: Entity 0xa Alarm: Unrecognized Alarm 0x4

00 b9 - Alarm Message

04 - Reserved

0a - Sequence Number

00 - Logical Node ID

03 - Severity (3=Major)

0a - Alarm Type ALARMentGATEWAY

04 - Gateway Unreachable 03=Gateway Reachable

07 - DATA Length

00 - Gateway Status 0=Down 1=Up

04 07 - GATEWAY ID (1031)

cb 07 65 41 - GATEWAY IP Address (203.7.101.65)

Alarm Cleared

This alarm is sent when the Gateway is considered 'reachable' again.

Sep 19 2007 11:12:38.048 X0\[88.235.44.169]\->H : 00 c1 02 77 00 03 0a 03 07 01 04 07 cc 09 c9 4a

Sep 19 2007 11:12:38 Major: Node 0: Entity 0xa Alarm: Unrecognized Alarm Cleared 0x3

00 c1 - Alarm Cleared

02 - Reserved

77 - Sequence Number

00 - Logical Node ID

03 - Severity (3=Major)

0a - Alarm Type Alarm Cleared

03 - Gateway Reachable 04=Unreachable

07 - DATA Length

01 - Gateway Status 0=Down 1=Up

04 07 - Gateway ID

cb 07 65 41 - Gateway IP address

Call Tracing

Call Tracing will capture the sending/reception of the OPTIONS method and indicate that re-routing has taken place because the gateway is down.

Example Call Trace:

21:24:03.305 SIP (W)

<--- [10.129.43.154, 5060 <- 10.129.43.23, 5060]

OPTIONS sip:10.129.43.154:5060;ttl=0 SIP/2.0

Via: SIP/2.0/UDP 10.129.43.23:5060; rport;branch=z9hG4bK-

6df4-1156281802-19999-423

Call-ID: 5aa9-1e61-7222006212322-chiloe-0@10.129.43.23

CSeq: 1 OPTIONS

Max-Forwards: 70

To: <sip:10.129.43.154;ttl=0>

From: <sip:10.129.43.23>;tag=95ffcd055e0f78f7d5d397020e8

9288db5f2

User-Agent: Dialogic-SIP/10.3.2.57 chiloe 0

Contact: <sip:10.129.43.23:5060>

Accept: application/ sdp

Content-Length: 0

Example entry in Call Trace:

13:12:48.804 CALL(GCL) (01:00003:01) WARNING: Channel Group [Lap_PC],GWIP [10.129.51.137] DOWN, trying next one

Additional Information

The SIP Options message being sent is supported on UDP only. When SIP Options Keep Alive is configured, verify the Default Transport type within the SIP Signaling object is set to UDP.
When sending a 200 OK to an OPTIONS request the IMG will not include SDP information.
If an OPTIONS message is not answered the corresponding gateway will be marked as “down or unreachable”.
When a call is attempted to an “unreachable” gateway, the IMG will automatically trigger the re-attempt logic if the gateway is part of a route list.
A gateway will only be marked as “reachable” when the number of sequential responses meet the configured value. (SIP Options "Keep Alive" Pane = Profiles/SIP SGP/SIP Options Keep Alive Pane)
The IMG will keep sending OPTIONS request at a configured rate. (SIP Options "Keep Alive" Pane = Profiles/SIP SGP/SIP Options Keep Alive Pane)