Fleksibilni Internet servisi na bazi kontrole kašnjenja i

in each queue are scaled by corresponding queue weights. WFQ can be then implemented
by serving the head-of-line packets in the increasing order of their scaled finishing times.
In BEDS with forced delay ratio, WFQ’s weights wTCP and wUDP are adjusted at each
packet arrival so that:
w
w
UDP
TCP
q
= δ , (5)
q
+
where q TCP = max( qTCP
, 1)
. If the queue weights for TCP and UDP queues satisfy (5), the
ratio of queuing delays in these two queues will be close to the specified value δ [4].
The deficiency of BEDS with forced delay ratio is that only UDP traffic benefits from the
proposed mechanism. TCP traffic suffers from increased queuing delay and,
consequently, lower throughput compared to the throughput achieved in a best-effort
network. This type of service differentiation does not comply with the concept of non-
elevated services because traffic classes do not receive “different but equal” quality of
service.
21
UDP
+
TCP
BEDS with forced loss ratio employs strict priority scheduling, with UDP queue
having higher priority. Drop probability for a packet is calculated on every packet arrival
to the TCP or UDP queue. For TCP packets, drop probability pTCP is calculated based on
the drop-conservative RED control function in the TCP queue. For UDP packets, the
drop probability pUDP is calculated from the TCP drop probability pTCP as:
p = λ p , (6)
UDP
where λ is the desired loss rate ratio. However, enforcing the loss ratio λ might be futile,
considering the different effect of packet losses on the performance of TCP and UDP
TCP