Manual Chapter : The effect of message pipelining on iRule variables

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BIG-IP LTM

  • 15.1.0, 15.0.1, 15.0.0, 14.1.2, 14.1.0, 14.0.1, 14.0.0, 13.1.3, 13.1.1, 13.1.0
Manual Chapter

The effect of message pipelining on iRule variables

SIP can pipeline messages by allowing messages that require less processing to be forwarded without waiting for earlier messages that require more processing. For this reason, it is not recommended to store state in tcl variables to be used by subsequent iRule events. There is no guarantee that the next event raised after the protocol's message event will be the MR_INGRESS for the same message. For example, saving the SIP uri in a tcl variable during a SIP_REQUEST event to use for making a routing decision during MR_INGRESS is not recommended. The next MR_INGRESS event may not be for the same message as the last SIP_REQUEST event.
MRF SIP implementation allows accessing the SIP iRule commands during the MR events. This is the recommended method to make routing and delivery decisions based on attributes of a message.
For example:
when MR_INGRESS { if {[URI::host [SIP::uri]] equal "othersp.com"} { MR::message route config "/Common/othersp_tc" pool "/Common/othersp_pool" } }