Throttle window is a one-second period that begins at the boundary of an actual clock second. One Standard Throttle provides the throughput of 2 Messages per second (MPS). All in-bound messages such as order submission, quote, trade report, etc. are collectively referred to as messages. Messages exceeding the entitled limit will be rejected by OCG.
Note: OCG will synchronize its system clock with GPS.
• Throttle is 4 (i.e. 8 messages per second)
• BSS sends 12 messages within 1 second (10:23:36 - 10:23:37)
• The first 8 messages will be accepted while the last 4 messages will be rejected immediately
BSS should therefore implement a flow control logic to send their messages according to their entitled throttles to minimize the occurrence of rejections. However, BSS Users are reminded that rejection of message is still possible due to a misalignment of throttle time windows between their BSS and OCG. Therefore, BSS is also necessary to implement a message re-submission mechanism in case of rejection due to throttle violation or other events such as network delay or other unexpected events.
BSS Users are also requested to note that if there is a severe violation of the entitled throttle limit, the corresponding OCG session will be dropped. Therefore, it is recommended that BSS should minimize the occurrence of message rejections byadopting below approaches:
- Implementing a proper flow control and re-submission mechanism. To minimize the occurrence of rejections due to exceeding the throttle limit, BSS should only send the number of messages less than or equal to the entitled throttle limit. In the example above, the BSS should control that no more than 8 messages could be sent to OCG in a single throttle window. Any additional messages should be queued in the BSS and be sent in the next throttle window.
- Synchronizing BSS system clock with GPS. If there is a misalignment of system clock between BSS and OCG, messages considered to be sent in two different throttle windows could be counted as being in the same throttle window in OCG. For example, the entitled throttle limit is 4, and the BSS sends 8 messages in the first window and 1 message in the next window. However, if all 9 messages arrive at OCG in the same throttle window based on OCG system clock, the last message will be rejected. Therefore, it is recommended BSS synchronizes its system clock with GPS to reduce the chance of rejection due to throttle window misalignment, and please note that some exceptional cases such as network delay variance may also cause message arrived at misaligned throttle time window and result in rejection.