Commit 1b95cb8d authored by Stephen Hemminger's avatar Stephen Hemminger

tc-tbf: remove ancient references to Alpha

In older versions of traffic shaping the Alpha kernel was special
and had higher HZ. This no longer matters, TC is based on high
resoulution timers in kernel.
parent 0c5982fd
......@@ -28,24 +28,20 @@ command.
TBF is a pure shaper and never schedules traffic. It is non-work-conserving and may throttle
itself, although packets are available, to ensure that the configured rate is not exceeded.
On all platforms except for Alpha,
it is able to shape up to 1mbit/s of normal traffic with ideal minimal burstiness,
sending out data exactly at the configured rates.
It is able to shape up to 1mbit/s of normal traffic with ideal minimal burstiness,
sending out data exactly at the configured rates.
Much higher rates are possible but at the cost of losing the minimal burstiness. In that
case, data is on average dequeued at the configured rate but may be sent much faster at millisecond
timescales. Because of further queues living in network adaptors, this is often not a problem.
Kernels with a higher 'HZ' can achieve higher rates with perfect burstiness. On Alpha, HZ is ten
times higher, leading to a 10mbit/s limit to perfection. These calculations hold for packets of on
average 1000 bytes.
.SH ALGORITHM
As the name implies, traffic is filtered based on the expenditure of
.B tokens.
Tokens roughly correspond to bytes, with the additional constraint that each packet consumes
some tokens, no matter how small it is. This reflects the fact that even a zero-sized packet occupies
the link for some time.
Tokens roughly correspond to bytes, with the additional constraint
that each packet consumes some tokens, no matter how small it is. This
reflects the fact that even a zero-sized packet occupies the link for
some time.
On creation, the TBF is stocked with tokens which correspond to the amount of traffic that can be burst
in one go. Tokens arrive at a steady rate, until the bucket is full.
......@@ -106,8 +102,9 @@ Furthermore, if a peakrate is desired, the following parameters are available:
.TP
peakrate
Maximum depletion rate of the bucket. Limited to 1mbit/s on Intel, 10mbit/s on Alpha. The peakrate does
not need to be set, it is only necessary if perfect millisecond timescale shaping is required.
Maximum depletion rate of the bucket. The peakrate does not
need to be set, it is only necessary if perfect millisecond timescale
shaping is required.
.TP
mtu/minburst
......
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