From the blog.

Managing Digital Racket
The more I tune out, the less I miss it. But that has presented me with some complex choices for a nuanced approach to curb

OECG – Chapter 16

452 Words. Plan about 2 minute(s) to read this.

adaptive shaping – a reduction in the shaping rate on frame because the frame switch is sending BECN or ForeSight messages

Bc – committed burst – the number of bits allowed to be sent for every Tc time interval.

Bc bucket – the first of the 2 buckets in the dual-bucket policing model

Be – excess burst – the number of bits that can be sent after it’s been quiet for a little while

Be bucket – the second of the 2 buckets in the dual-bucket policing model

BECN – backward explicit congestion notification – tells a frame router of upstream congestion

CIR – committed information rate – in the context of QoS, this is the rate at which traffic is being shaped or policed.

conform – a packet that is within the contract is said to conform

dual token bucket – used instead of a single bucket to accommodate bursting

dual-rate three-color policer – there’s a main rate, a peak rate, and packets can conform, exceed, or violate

ELMI – enhanced local management interface – Cisco proprietary LMI where a switch can tell a router about virtual circuit parameters with info like CIR, Bc and Be

exceed – this is higher than the base policing rate, but if a burst rate has also been defined, it’s below the burst rate

ForeSight – like a BECN, except Cisco proprietary

map class – used in frame-relay traffic shaping.
marking down – what happens when an action to set the IPP or DSCP bit to some lower value is performed, rather than discarding an exceeding packet. The lower value makes the packet more likely to be discarded downstream.

mincir – minimum CIR – the basement for adaptive shaping. We don’t limbo lower than this value.

multi-action policing – tweaking more than one thing on packets that meet a certain categorization

nested policy maps – where one policy-map calls another. A shaper can call a low-latency queue, for example.

PIR – peak information rate – the sustainable burst rate in 2-rate policing

policing rate – the rate we’re limiting the traffic to as it flows through the policer. The speed limit, if you will.

shaping rate – the speed limit

single-rate three-color policer – one speed limit, with packets either conforming, exceeding or violating

single-rate two-color policer – one speed limit, with packets either conforming or exceeding

Tc – time interval used by shapers and CAR (but not policing)
token bucket – a concept used to describe how shapers and policers make traffic conform to a specific bit rate

traffic contract – how fast we can go normally, and the burst rate.

violate – packets that neither conform nor exceed are said to violate the traffic contract.

Ethan Banks writes & podcasts about IT, new media, and personal tech.
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