New PCQ implementation in v5rc5

RouterOS General
1

Now as soon as new stream activates it will get 1/4th of rate with highest priority. If rate is “0” sub-stream will not have this feature (as 1/4th of “0” is “0”)

What does that mean? What priority? For how long will the new stream be guaranteed .25 of the rate?

2

This is done to ensure that new streams do not have hard time getting traffic if all traffic was used before they arrive.

Example: you have 20Mbps throughput available and PCQ-limit is 8Mbps, and there are 4 clients getting max (P2P downloaders)and then 5th logs in (wanna make VOIP call):

With PCQ before v5.0rc4:

  1. 5Mbps 5Mbps 5Mbps 5Mbps (not logged)
  2. 5Mbps 5Mbps 4.9Mbps 4,9Mbps 0,2Mbps
  3. 5Mbps 5Mbps 4.8Mbps 4,9Mbps 0,3Mbps
    and after some time streams actually equalize
  4. 4Mbps 4Mbps 4Mbps 4Mbps 4Mbps

So 5th client had a late start and as priority is same for all streams it has hard time to get his traffic cause others have strong position already.

With PCQ after v5.0rc4:

  1. 5Mbps 5Mbps 5Mbps 5Mbps (not logged)
  2. 4.5Mbps 4.5Mbps 4.5Mbps 4,5Mbps 2Mbps (1/4th of rate-limit)
  3. 4Mbps 4Mbps 4Mbps 4Mbps 4Mbps

So in other words - that feature is bonus for late starters to get those streams up to speed faster