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Author(s) Bonaventure Olivier
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Two flows multiplexed through a queue

A router has three 1 Mbps interfaces :

  • a downstream interface
  • two upstream interfaces

The two upstream interfaces carry packets of fixed size (1000 bits). The traffic pattern that arrives on a given interface is represented as a sequence of characters, each letter represents a fixed size packet. A dot (.) indicates that no packet was received during one millisecond.

Question 1: Traffic pattern

The first interface receives the following traffic pattern :

.j.i.h.g.f.e.d.c.b.a (packet a is the first received packet)

The second interface receives the following traffic pattern : JIHGFEDCBA

When the router receives two packets from the input links at the same time, it always places the packet received from the second link (represented by the capital letter) first in its buffer. What are the first 12 packets that we will observe on the output link ?

Question 2: Traffic pattern

The first interface receives the following traffic pattern : .j.i.h.g.f.e.d.c.b.a (packet a is the first received packet)

The second interface receives the following traffic pattern : ..JI....HGFE....DCBA

When the router receives two packets from the input links at the same time, it always places the packet received from the second link (represented by the capital letter) first in its buffer. What is the traffic pattern that we will observe on the output link ?

What are the first 12 packets that we will observe on the output link ?