[e2e] Policing TCP flows

[Reuven Zeitak]

Dear all,

please be patient with me. I'm a newbie here:

Simply stated, I want to know what the effect of "policing"
tcp traffic would be, compared to "shaping" it.

Naively, tcp squirts "bursts" into the network, which get spread
out by the network properties. Then self clocking sets in, and tcp
sends packets at the speed of ack.

Policers just discard packets that are non conforming, but the conforming
packets are not paced according to the policer's rate.  It seems to
me that a single tcp flow that is going through a single policer, will settle
down to something like one policer allowed "burst" per RTT instead of 
adjusting itself to a smooth packet rate ( please excuse my terminology).

On the other hand, a stream that is running at a smooth rate, and is conforming,
will send ack's at the correct speed, and ( window growth notwithstanding) the correct
rate is maintained.

For completeness, I'll note that if the flow was "shaped", there are no "bursts", since
the spread is set by the shaper, not by the entire network.

questions:

a) Is the smooth rate unstable towards the burst per RTT? I mean, supposing the
window is slightly increased, such that the policer discards a single packet-
does the congestion response of tcp drive it to the burst pre RTT, or does it
pull itself back into the "smooth rate" state?

b) Suppose there are several tcp flows being policed together?

c) any literature on this subject?  I saw some papers about how ABR is bad for tcp,
but is this really the same thing?

Thank you for your patience

reuven