Global SIP Timers

This section explains how to configure SIP retransmission and expiration timers.

Note:

you can also set timers and counters per SIP interface.

Overview

SIP timers define the transaction expiration timers, retransmission intervals when UDP is used as a transport, and the lifetime of dynamic TCP connections. The retransmission and expiration timers correspond to the timers defined in RFC 3261.

init timer: is the initial request retransmission interval. It corresponds to Timer T1 in RFC 3261.
This timer is used when sending requests over UDP. If the response is not received within this interval, the request is retransmitted. The retransmission interval is doubled after each retransmission.
max timer: is the maximum retransmission interval for non-INVITE requests. It corresponds to Timer T2 in RFC 3261.
The retransmission interval is doubled after each retransmission. If the resulting retransmission interval exceeds the max timer, it is set to the max timer value.
trans expire: is the transaction expiration timer. This value is used for timers B, D, F, H and J as defined in RFC 3261.
invite expire: defines the transaction expiration time for an INVITE transaction after a provisional response has been received. This corresponds to timer C in RFC 3261.
If a final response is not received within this time, the INVITE is cancelled. In accordance with RFC 3261, the timer is reset to the invite expire value when any additional provisional responses are received.
Inactive dynamic conn timer defines the idle time of a dynamic TCP connection before the connection is torn down. Idle is defined as not transporting any traffic. There is no timer in RFC 3261 corresponding to this function.

Timers Configuration

To configure timers:

In Superuser mode, type configure terminal and press Enter.
```
ORACLE# configure terminal
```
Type session-router and press Enter.
```
ORACLE(configure)# session-router
```
Type sip-config and press Enter. The system prompt changes to let you know that you can begin configuring individual parameters.
```
ORACLE(session-router)# sip-config
ORACLE(sip-config)#
```
init-timer—Enter the initial timeout value in milliseconds for a response to an INVITE request, and it applies to any SIP request in UDP. In RFC 3261, this value is also referred to as TIMER_T1. The default is 500. The valid range is:
- Minimum—0
- Maximum—999999999
max-timer—Enter the maximum transmission timeout (T2) for SIP in milliseconds.

When sending SIP over UDP, a re-transmission timer is used. If the timer expires and the message is re-transmitted, the re-transmission timer is then set to twice the previous value (but will not exceed the maximum timer value). Using the default values of 500 milliseconds and 4000 milliseconds, the re-transmission timer is 0.5, then 1, 2, and finally 4. The incrementing continues until the transmission expire timer activates. The default is 4000. The valid range is:
- Minimum—0
- Maximum—999999999
trans-expire—Enter the transaction expire timeout value (Timer B) in seconds to set the time for SIP transactions to live. The same value is used for Timers D, F, H and J. The default is 32. The valid range is:
- Minimum—0
- Maximum—999999999
invite-expire—Enter the invite expire timeout value (Timer C) in seconds to indicate the time for SIP client transaction will live after receiving a provisional response. The default is 180. The valid range is:
- Minimum—0
- Maximum—999999999
inactive-dynamic-conn—Enter the inactive dynamic connection value in seconds to set the time limit for inactive dynamic connections.

If the connection between the SIP proxy and a session agent is dynamic (for example, through dTCP), and the connection has been idle for the amount of time specified here, the SIP proxy breaks the connection. Idle is defined as not transporting any traffic. The default value is 32. The valid range is:
- Minimum—0
- Maximum—999999999
  
  Note:
  Setting this parameter to 0 disables this parameter.
The following example shows SIP config timer values for a peering network. Some parameters are omitted for brevity.
```
sip-config
        state                          enabled
        operation-mode                 dialog
dialog-transparency		disabled
home-realm-id                  acme
        egress-realm-id
        nat-mode                       Public
        registrar-domain
        registrar-host
        registrar-port                 0
        init-timer                     500
        max-timer                      4000
        trans-expire                   32
        invite-expire                  180
        inactive-dynamic-conn          32
```