Bug ID 603019: Inserted SIP VIA branch parameter not unique between INVITE and ACK

Last Modified: Oct 06, 2020

Bug Tracker

Affected Product:  See more info
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, 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

Fixed In:
13.0.0, 12.1.2, 11.6.3

Opened: Jul 06, 2016
Severity: 3-Major


The branch parameter of the inserted VIA header is sometimes the same between an INVITE and ACK message.


SIP proxy servers which perform strict message validations may reject the call.


If the CSEQ number of a SIP message is the same, the inserted VIA header will contain the same branch parameter.



Fix Information

Included a hash of the branch parameter of the received top-most via header into the branch parameter of the inserted via header. Thus is the received top-most via conforms to the spec and generates a different branch parameter between INVITE and ACK, the inserted via will have a different branch parameter.

Behavior Change