Topic
The purpose of this article is to explain how the licensed throughput rate is enforced on a BIG-IP Virtual Edition (VE) system.
Description
The BIG-IP VE product license determines the maximum allowed throughput rate. When calculating throughput, the BIG-IP VE system accounts for packets ingressing and egressing the system separately. Additionally, the licensed throughput rate for ingress and egress is enforced separately. For example, if you have a 200 Mbps license, ingress into the Traffic Management Microkernel (TMM) has a limit of 200 Mbps and egress from TMM also has a limit of 200 Mbps.
Ingress packets reach a buffer that is polled periodically for queued bytes. When the queued number of bytes reaches the limit, as determined by a sliding mechanism, the rate shaper begins limiting ingress traffic. Throughput for egress traffic is determined by the amount of bytes sent over predefined sliding time windows. If the number of bytes sent surpasses the limit for a given time window, the rate shaper starts limiting the egress traffic.
The rate shaper throttles throughput to the licensed rate at the packet level, rather than at the connection level. Ingress and egress packets are dropped during the limiting process and no management is done at the connection level.
Important: For BIG-IP versions prior to 12.1.0, promiscuous traffic received on the BIG-IP interface is considered when determining the throughput rate. Starting with BIG-IP 12.1.0 and later, the throughput calculation no longer includes promiscuous traffic (for example: for BIG-IP 12.1.0 and later, failover, heartbeat, mirroring, configsync, and monitors are no longer counted as throughput traffic. Regular BIG-IP traffic is still counted (including ARP, broadcasts, UDP, and TCP). Note: The limit is divided by the number of Traffic Management Microkernels (TMM). Therefore, each TMM is capped at a fraction of the total licensed limit. For example, with a 200 Mbps license with two TMMs, the expected throughput would be 100 Mbps per TMM instance. No single connection can exceed the limit for a TMM instance. Beginning in BIG-IP 12.0.0, BIG-IP 11.6.1 HF2, and BIG-IP 11.5.4 HF2 when TMM is operating in multi-threaded mode, the total licensed limit is divided by each TMM process and not the total TMM instances; therefore, all instances executed by a TMM process share the limit. Continuing with the previous example, a BIG-IP VE with a single TMM process running two threads, a single connection on one of the two TMM instances can use the full limit of 200 Mbps. For a better understanding of TMM multi-threading, refer to the following articles: Beginning in BIG-IP 11.4.0, when the throughput rate exceeds 75 percent of the maximum allowed throughput rate licensed, a notification similar to the following example is logged in the /var/log/ltm file: 01010045:5: Bandwidth utilization is 8 Mbps, exceeded 75% of Licensed 10 Mbps Note: Due to a difference in polling intervals, the calculations displayed in the performance graph will not match real-time statistics and should only be used as a gauge for throughput limits in BIG-IP VE. Determining licensed throughput To determine the maximum allowed throughput rate for a BIG-IP VE system, perform the following procedure: Impact of procedure: Performing the following procedure should not have a negative impact on your system. Viewing dropped ingress/egress packets To view the number of ingress or egress packets that have been dropped, perform the following procedure: Impact of procedure: Performing the following procedure should not have a negative impact on your system. The output of the command appears similar to the following example: Note: The following output is from an idle system that has not experienced any ingress or egress packet drops.Recommendations
shaper_tid ingress_max ingress_avg ingress_red ingress_drops egress_drops 1 0 100 0 0 0 0 0 100 0 0 0 Supplemental Information
