Priority Queue is one of the basic scheduling mechanism.
PQ always serves one queue prior to the other. In other words, if there is packet in High priority queue it is served before packet from Low priority queue.
It sounds really good. We can assign VoIP packets to High priority and other packets to Low priority. RTP packets are delay sensitive, so proposed solution seems to be perfect.
And that’s true!
But:
PQ always serves one queue prior to the other. In other words, if there is packet in High priority queue it is served before packet from Low priority queue.It sounds really good. We can assign VoIP packets to High priority and other packets to Low priority. RTP packets are delay sensitive, so proposed solution seems to be perfect.
And that’s true!
But:
- If there is always at least one packet in High priority (meaning its arrival rate is equal or greater than output link rate) then Low priority queue will starve. That could have big impact on whole network.
- Network interface has finite buffer and shares it between two queues (according to example above). If there is no free buffer space for arriving packet it will be dropped, even though it is VoIP packet. It must be taken into consideration especially when in the network there are many applications which uses TCP gready type of transmission, eg. FTP, BitTorrent, etc
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