3Com CoreBuilder 7000 Operation Manual page 123

The bandwidth available from the network may vary, but does not
become less than MCR.
The CoreBuilder 7000 switch forwards the ABR information to the end
users.
Three information elements are involved in the signaling of ABR
capability:
1 ATM traffic descriptor. includes:


Peak Cell Rate


Sustain Cell Rate


Max Burst Size


ABR Min Cell Rate.
2 ABR setup parameters include:


ABR Initial Cell Rate (ICR) — The rate at which each source may
initially commence transmitting.


ABR Transient Buffer Exposure (TBE) — The number of cells which can
be supported for a VC starting up before the control loop is
established.


Cumulative RM Fixed Round Trip Time (FRTT — The sum of the fixed
and propagation delays from the source to a destination and back.


Rate Increase Factor (RIF) — Controls the amount by which the cell
transmission rate may increase upon receipt of an RM-cell.


Rate Decrease Factor (RDF) — Controls the decrease in the cell
transmission rate.
3 ABR additional parameters include:


Nrm — Nrm is the maximum number of cells a source may send for
each forward RM-cell


Trm — Trm provides an upper bound on the time between forward
RM-cells for an active source.


CDF — The Cutoff Decrease Factor, CDF, controls the decrease in ACR
associated with CRM


ADTF — The ACR Decrease Time Factor is the time permitted between
sending RM-cells before the rate is decreased to ICR.
Quality of Service Parameters 123