Cisco BPX 8650, Installation And Configuration Manual

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Cisco BPX 8600 Series Installation and Configuration
Release 9.3.30, Part Number 78-12907-01 Rev. E0, May 2005
Chapter 21 Configuring ATM Connections
ATM Connection Configuration
Minimum SCR and PCR
The minimum Sustainable Cell Rate (SCR) and Peak Cell Rate (PCR) of a connection supported by the
BXM card used to be 50 cells per second (cps) or 19.2 Kbps. These values were set to maintain a policing
accuracy with 1% when policing is performed on a BXM or UXM card. Because of this limitation, it was
impossible to offer and differentiate connection services on the BXM at speeds less than 19.2 Kbps
(50 cps).
The BPX supports connection policing with SCR and PCR values as low as 12 cps on the BPX switch,
with certain card limitations.
FCES (Flow Control External
Segments) See Meaning of VS/VD and Flow Control External Segments, Figure 21-9.
SCR Sustainable Cell Rate: Long term limit on the rate a connection can sustain
MBS Maximum Burst Size: Maximum number of cells which may burst at the PCR but still
be compliant. Used to determine the Burst Tolerance (BT) which controls the time scale
over which the SCR is policed
Policing See the definitions of Traffic Policing in Table 21-8.
VC QDepth VC Queue Depth
CLP Hi Cell Loss Priority Hi threshold (% of VC QMax)
CLP Lo/EPD Cell Loss Priority Low threshold (% of VC QMax)/Early Packet Discard. If AAL5
FBTC = yes, then for the BXM card this is the EPD threshold setting.
EFCI Explicit Forward Congestion Indication threshold (% of VC QMax)
ICR Initial Cell Rate:
The rate at which a source should send initially and after an idle period
ADTF (ATM Forum TM 4.0
term) The Allowed-Cell-Rate Decrease Factor: Time permitted between sending RM-cells
before the rate is decreased to ICR
Trm (ATM Forum TM 4.0 term) An upper bound on the time between forward RM-cells for an active source, that is, RM
cell must be sent at least every Trm msec
RIF (ATM Forum TM 4.0 term) Rate Increase Factor: Controls the amount by which the cell transmission rate may
increase upon receipt of an RM cell
RDF (ATM Forum TM 4.0 term) Rate Decrease Factor: Controls the amount by which the cell transmission rate may
decrease upon receipt of an RM cell
Nrm (ATM Forum TM 4.0 term),
BXM only. Nrm: Maximum number of cells a source may send for each forward RM cell, that is, an
RM cell must be sent for every Nrm-1 data cells
FRTT (ATM Forum TM 4.0
term), BXM only. Fixed Round Trip Time: the sum of the fixed and propagation delays from the source to
a destination and back
TBE (ATM Forum TM 4.0 term),
BXM only. Transient Buffer Exposure: The negotiated number of cells that the network would like
to limit the source to sending during start-up periods, before the first RM-cell returns.
IBS Initial Burst Size
Trunk cell routing restriction
(Y/N) [Y] The default (Y) restricts ATM connection routes to include only ATM trunks. Selecting
(N) allows the network to route these connections over non-ATM trunks (such as
Fastpacket trunks).
Table 21-10 Connection Parameter Descriptions (continued)
Parameter Description