If i set the timeout multiplier to be 3 on a content rule so it's 48 seconds, why when i look at the 'flow-agent show fcb' information does it give me the correct inactiveTimout but then allocate a 'New FCB time' of 120 which overrides my configured 48 seconds?
May timeout due to inactivity: Yes , inactiveTimeout: 48
New FCB time: 120, will consider inactivity in 86 secs
A. FCB is a term used for two different things. There is a fastpath FCB that is used to map a flow and allow transformations on each frame in the flow to be done entirely by the fastpath microcode running on either the etherPIF (for 10/100 ports) or the XPIF (for Gigabit ports). Fastpath FCBs come out of memory that is local to the chip used for the port. For an etherPIF, this chip contains 4 10/100 Ethernet port interfaces. The memory used for FCBs is shared for each port in the etherPIF. In the CSS 11150 and CSS 11050 products, the ports 1-4 share memory, ports 5-8 share memory, and so on. For XPIF ports, the memory is not shared between ports. If you have uplink 10/100 ports, you will want to keep them isolated from any other ports that are occupied (like server ports) if you have that option. Obviously, if all ports are populated, you do not get to make this decision.
The flow manager also has FCBs. The flow manager FCBs contain all the information in the fastpath FCB, plus additional information to allow the flow manager to properly manage the flow. There is one FCB used per ingress direction of a flow. Thus, a TCP connection is going to take two FCBs, and a UDP flow is going to take one. UDP flows can be bi-directional, however, they often are not (for example, streaming audio).