Hi,
When we say "a link with capacity 𝒄 packets per second", is this link directed? If a link between h1 and h2 has capacity 5mb/s, is that for one direction or both direction?
I am not familiar with the signal processing stuff at all. In a link between h1 and h2, does bitrate from h1 to h2 impact the bitrate from h2 to h1?
Does 1-archi.pdf slide 33 mean to say bandwidth should refer to the same thing as capacity? (but is usually used as bitrate)
Hello and thank you for your question,
When we refer to the link capacity of a line, we need to specify which interface of the line we refer to. The capacity (or bitrate) of the interface is the maximum number of bits per second that can exit the interface into the line. One line can have different bitrates in each direction. If we simply say "a link with capacity 
packets per second", then we mean that this is the capacity in each direction. The bitrate from h1 to h2 does not affect the bitrate from h2 to h1 (unless you use tcp, where you also have ACK packets in the opposite direction).
Slide 33 refers to the capacity of a channel. This is indeed related to signal processing, but by "channel" we mean a specific range of frequencies that can transmit any signal within this range of bandwidth 
(Hz). In a given line, the messages of each direction are transmitted in different channels, which can have different bandwidths, hence different bit rates.
As it is also mentioned in slides 32 and 33, the terms bandwidth and bit rates are sometimes used interchangeably.
I hope this answer your question.
Best,
Plouton
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