PointRed Telecom Ltd. MCRD-2458 Manuale Utente
M i c r o R e d & M i c r o V i e w N M S U s e r M a n u a l v 1 . 0
Page 85
of bytes continuously, for some time, without being interrupted. As soon as EBC
bytes have been sent, the application is forced back to normal behavior (average
rate ranging between CIR and PIR).
bytes have been sent, the application is forced back to normal behavior (average
rate ranging between CIR and PIR).
9.3.4.
Committed Burst Size (CBS)
The CBS corresponds to the minimum number of bytes that have to be available
in order for a transmission to start. By the time that the transmission starts, it is
not possible to be interrupted, until there are no other data to send. By default
this value is the smallest possible (a single packet size ideally) and scarcely will
you have to set a different value.
in order for a transmission to start. By the time that the transmission starts, it is
not possible to be interrupted, until there are no other data to send. By default
this value is the smallest possible (a single packet size ideally) and scarcely will
you have to set a different value.
In order to better understand the concept of rate and burst, consider the
analogy: Each class (or subclass as we will see later) is like a bucket with size
EBS. The bucket is filled up at a rate which ranges between CIR and PIR. In
accordance with this analogy, transmission starts when we throw water out of
the bucket. The minimum quantity of water (traffic) that we can be thrown out is
CBS. Therefore, when a class is idle for a while, it's possible for an application
later on, to send a large burst of data, until the “bucket” is empty. Similarly, for a
class that sends traffic at a steady rate, lower than CIR, its “bucket” will always
be filled up.
analogy: Each class (or subclass as we will see later) is like a bucket with size
EBS. The bucket is filled up at a rate which ranges between CIR and PIR. In
accordance with this analogy, transmission starts when we throw water out of
the bucket. The minimum quantity of water (traffic) that we can be thrown out is
CBS. Therefore, when a class is idle for a while, it's possible for an application
later on, to send a large burst of data, until the “bucket” is empty. Similarly, for a
class that sends traffic at a steady rate, lower than CIR, its “bucket” will always
be filled up.
9.3.5.
Priority
The Priority value dictates which class, among those at the same layer, will get
the unused bandwidth. This bandwidth comes from those classes that are not
fully utilizing their CIR. This extra bandwidth is delivered first to the class with
the highest priority and as soon as the PIR (or EBS) of this class is reached, the
distribution continues to the next class in order of priority. Priority value can vary
between 0 (higher priority) and 7 (lower priority).
the unused bandwidth. This bandwidth comes from those classes that are not
fully utilizing their CIR. This extra bandwidth is delivered first to the class with
the highest priority and as soon as the PIR (or EBS) of this class is reached, the
distribution continues to the next class in order of priority. Priority value can vary
between 0 (higher priority) and 7 (lower priority).
Consider the scenario: We have a standard 11mbps wireless link, and we want to
guarantee half of it, to outgoing TCP traffic. Then we further divide it to TCP
traffic destined for host x, and that destined to host y. This scenario is depicted
in the following table.
guarantee half of it, to outgoing TCP traffic. Then we further divide it to TCP
traffic destined for host x, and that destined to host y. This scenario is depicted
in the following table.
Classes in the table denoted as “auto”, are classes that are automatically (and
transparently) created by the system to handle unclassified traffic. These
automatically generated classes, get the rest of the bandwidth (as its CIR), which
is not reserved for any of the user-defined ones. System generated classes are
always of priority 7.
transparently) created by the system to handle unclassified traffic. These
automatically generated classes, get the rest of the bandwidth (as its CIR), which
is not reserved for any of the user-defined ones. System generated classes are
always of priority 7.