Bug ID 939529: Branch parameter not parsed properly when topmost via header received with comma separated values

Last Modified: Nov 07, 2022

Affected Product(s):
BIG-IP LTM(all modules)

Known Affected Versions:
11.6.0, 11.6.0 HF1, 11.6.0 HF2, 11.6.0 HF3, 11.6.0 HF4, 11.6.0 HF5, 11.6.0 HF6, 11.6.0 HF7, 11.6.0 HF8, 11.6.1, 11.6.1 HF1, 11.6.1 HF2, 11.6.2, 11.6.2 HF1, 11.6.3,,,,, 11.6.4, 11.6.5,,, 12.0.0, 12.0.0 HF1, 12.0.0 HF2, 12.0.0 HF3, 12.0.0 HF4, 12.1.0, 12.1.0 HF1, 12.1.0 HF2, 12.1.1, 12.1.1 HF1, 12.1.1 HF2, 12.1.2, 12.1.2 HF1, 12.1.2 HF2, 12.1.3,,,,,,,, 12.1.4,, 12.1.5,,, 13.0.0, 13.0.0 HF1, 13.0.0 HF2, 13.0.0 HF3, 13.0.1, 13.1.0,,,,,,,,, 13.1.1,,,,, 13.1.3,,,,,, 14.0.0,,,,,, 14.0.1,, 14.1.0,,,,,, 14.1.2,,,,,,,,, 14.1.3,, 15.0.0, 15.0.1,,,,, 15.1.0,,,,,, 15.1.1, 15.1.2, 16.0.0,, 16.0.1

Fixed In:
16.1.0,,, 14.1.4,,,

Opened: Aug 24, 2020

Severity: 3-Major


MRF SIP in LoadBalancing Operation Mode inserts a VIA header to SIP request messages. This Via header is removed from the returned response message. The VIA header contains encrypted routing information to route the response message. The SIP specification states that INVITE/CANCEL messages in a dialogue should contain the same branch header. The code used to encrypt the branch field returns a different branch ID for INVITE and CANCEL messages.


Some SIP clients have code to verify the branch fields in the Via header. These clients expect the branch to be same for INVITE and CANCEL in a dialogue. Because the branch received is different, these clients are unable to identify the specific INVITE transaction. CANCEL is received and client sends a 481 error: SIP/2.0 481 Call/Transaction Does Not Exist.


-- Enabling SIP Via header insertion on the BIG-IP system. -- SIP MRF profile. -- Need to cancel an INVITE. -- INVITE Via header received with multiple comma-separated values.


Use iRules to remove the topmost Via header and add new a new Via header that uses the same branch as INVITE and CANCEL while sending messages to SIP clients.

Fix Information

The BIG-IP system now ensures the branch field inserted in the via header same for INVITE and CANCEL messages.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips