Fleksibilni Internet servisi na bazi kontrole kašnjenja i

est-effort network. If its duplicate is accepted into the virtual queue, a blue packet is
assigned a deadline based on the expected finish time of the duplicate and it is placed in
the blue queue. A green packet is accepted into the green queue if it passes the so-called
“green acceptance test”. A green packet arriving to the queue passes the test if there is a
possibility that it will be served before a specified delay bound d expires, and fails
otherwise. This possibility is evaluated based on the number of green and blue packets
that are already waiting in queues. Blue packets are always served no later than their
deadline. Green packets are served in the meantime if they have been in the queue for
less than the specified delay bound d and are dropped otherwise. A control loop is used to
decide which packet should be served first if the deadlines of both head-of-line packets
still can be met, even if the other queue is served beforehand.
Fig. 3. DSD architecture: duplicates of all incoming packets are sent to a virtual queue. Original
packets are classified according to their colours into the blue or green queue.
3.2. Best-Effort Differentiated Services (BEDS)
BEDS [4] defines two types of services: drop-conservative for TCP and delay-
conservative for UDP flows. TCP and UDP packets are queued in two Random Early
Detection (RED) [29] queues with distinct sets of parameters.
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