Cisco IOS XR Session Border Controller Configuration Guide Release 3.6
SIP Timer
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SIP Timer

Table Of Contents

SIP Timer


Information About SIP Timer

How to Configure SIP Timer

Configuring SIP Timer

Additional References

Related Documents




Technical Assistance

SIP Timer

The SIP Timer feature allows the user to configure a number of SIP timers that were hard-coded in the previous releases of Cisco IOS XR software. The ability to configure SIP timers enables users to improve the interoperability and performance of their devices and network environment.

Feature History for SIP Timer Functions


Release 3.4.1

This feature was introduced on the Cisco XR 12000 Series Router.

Release 3.5.0

No modification.

Release 3.6.0

No modification.


This module contains the following sections:

Information About SIP Timer

How to Configure SIP Timer

Related Documents

Information About SIP Timer

The SIP timer feature allows the user to configure some of the SIP timers that were hardcoded to default values in the previous releases of Cisco IOS XR software. In the previous releases, the SBC used the default SIP timer values recommended by RFC 3261. See Table 8.

Table 8 Default Values of the Timers 



500 ms default

RTT Estimate


4 s

The maximum retransmit interval for non-INVITE requests and INVITE responses


5 s

Maximum duration a message will remain in the network

Timer A

initially T1

INVITE request retransmit interval, for UDP only

Timer B

64* T1

INVITE transaction timeout timer

Timer C

> 3 min

proxy INVITE transaction timeout

Timer D

> 32 s for UDP
0 s for TCP/SCTP

Wait time for response retransmits

Timer E

initially T1

non-INVITE request retransmit interval, UDP only

Timer F

64* T1

non-INVITE transaction timeout timer

Timer G

initially T1

INVITE response retransmit interval

Timer H

64* T1

Wait time for ACK receipt

Timer I

T4 for UDP
0 s for TCP/SCTP

Wait time for ACK retransmits

Timer J

64* T1 for UDP
0 s for TCP/SCTP

Wait time for non-INVITE request retransmits

Timer K

T4 for UDP
0 s for TCP/SCTP

Wait time for response retransmits

The SBC allows the user to modify T1, T2 and Timer D, using: udp-first-retransmit-interval, udp-max-retransmit-interval and udp-response-linger-period accordingly. Another timer also introduced in this release is invite-timeout parameter, which lets the user choose how long SBC should wait for the remote SIP endpoint to respond to the SBC's outgoing INVITE or Timer B in an outgoing transaction.

In addition to the SIP protocol-level timers, SBC also allows modification of transport-related timers: tcp-connect-timeout (how long TCP SYN will wait for the reply); tcp-idle-timeout (how long TCP connection should stay active while idle), and tls-idle-timeout (how long TLS connection should stay active while idle). Although these timers are transport-level values, IOS-XR supports these timers in SIP only, but not in H.323, nor H.248.

Note The incorrect configuration of the SIP timer values may lead to unexpected behavior in certain cases.

How to Configure SIP Timer

This section contains the steps for configuring SIP timers.

Configuring SIP Timer


1. configure

2. sbc service-name

3. sbe

4. sip timer

5. tcp-connect-timeout interval

6. tcp-idle-timeout interval

7. tls-idle-timeout interval

8. invite-timeout interval

9. udp-first-retransmit-interval interval

10. udp-max-retransmit-interval interval

11. udp-response-linger-period interval

12. commit

13. exit

14. show services sbc service-name sbe sip timers


Command or Action

Step 1 



RP/0/0/CPU0:router# configure

Enables global configuration mode.

Step 2 

sbc service-name


RP/0/0/CPU0:router(config)# sbc mysbc

Enters the mode of an SBC service.

Use the service-name argument to define the name of the service.

Step 3 



RP/0/0/CPU0:router(config-sbc)# sbe

Enters the mode of the signaling border element (SBE) function of the SBC.

Step 4 

sip timer


RP/0/0/CPU0:router(config-sbc-sbe)# sip timer

Enters the mode of the SIP timer function of the SBC.

Step 5 

tcp-connect-timeout interval


RP/0/0/CPU0:router(config-sbc-sbe-sip-tmr)# tcp-connect-timeout 3000

Configures the time (in milliseconds) that SBC waits for a SIP TCP connection to a remote peer to complete before failing that connection. The default timeout interval is 1000 milliseconds.

Step 6 

tcp-idle-timeout interval


RP/0/0/CPU0:router(config-sbc-sbe-sip-tmr)# tcp-idle-timeout 30000

Minimum time (in milliseconds) a TCP socket has not processed any traffic, before it is closed. The default is 2 minutes.

Note The value for this command might not be precise since the idle timers are checked every 12 seconds.

Step 7 

tls-idle-timeout interval


RP/0/0/CPU0:router(config-sbc-sbe-sip-tmr)# tls-idle-timeout 1800000

Minimum time (in milliseconds) a TLS socket can remain idle before it is closed. The default is one hour.

Step 8 

invite-timeout interval


invite-timeout 60

Configures the time (in seconds) that SBC waits for a final response to an outbound SIP INVITE request. The default is 180 seconds. If no response is received during that time, an internal "408 Request Timeout" response is generated and returned to the caller.

Step 9 

udp-first-retransmit-interval interval


RP/0/0/CPU0:router(config-sbc-sbe-sip-tmr)# udp-first-retransmit-interval 1000

Configures the time (in milliseconds) that SBC waits for a UDP response or ACK before sending the first retransmission of the relevant signal.

If SBC keeps getting no responses, it doubles subsequent retransmission intervals each time until they reach the udp-max-retransmit-interval duration. SBC ceases retransmitting the request and time out the signal if 64 times this duration passes without the receipt of a response/ACK.

The default first UDP retransmission interval is 500 milliseconds.

Step 10 

udp-max-retransmit-interval interval


RP/0/0/CPU0:router(config-sbc-sbe-sip-tmr)# udp-max-retransmit-interval 8000

Configures the maximum time interval (in milliseconds) at which SBC will retransmit (see udp-first-retransmit-interval above). The default maximum UDP retransmission interval is 4 seconds.

Step 11 

udp-response-linger-period interval


RP/0/0/CPU0:router(config-sbc-sbe-sip-tmr)# udp-response-linger-period 10000

Configures the time (in milliseconds) for which SBC will retain negative UDP responses to INVITE requests.

All subsequent retransmitted responses received within this time will be answered with a negative ACK. Thereafter, any further retransmitted responses are ignored.

The default UDP response linger period is 32 seconds.

Step 12 



RP/0/0/CPU0:router(config-sbc-sbe-sip-tmr)# commit

Saves configuration changes. Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.

Step 13 



RP/0/0/CPU0:router(config-sbc-sbe)# exit

Exits the sip timer mode and returns to the SBE mode.

Step 14 

show services sbc service-name sbe sip timers


RP/0/0/CPU0:router(config-sbc)# show services sbc mysbc sbe sip timers

Shows the currently configured SIP-related timers.

Additional References

The following sections provide references related to SIP timer support in SBC.

Related Documents

Related Topic
Document Title

Cisco IOS XR master command reference

Cisco IOS XR Master Commands List

Cisco IOS XR SBC interface configuration commands

Cisco IOS XR Session Border Controller Command Reference

Initial system bootup and configuration information for a router using the Cisco IOS XR Software

Cisco IOS XR Getting Started Guide

Cisco IOS XR command modes

Cisco IOS XR Command Mode Reference



No new or modified standards are supported by this feature, and support from existing standards has not been modified by this feature.


MIBs Link

To locate and download MIBs using Cisco IOS XR software, use the Cisco MIB Locator found at the following URL and choose a platform under the Cisco Access Products menu:



RFC 3261

SIP: Session Initiation Protocol

RFC 2543

Session Initiation Protocol

Technical Assistance


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