Cisco BPX 8650, Installation And Configuration Manual

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21-28
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
Figure 21-6 CBR Connection Prompt Sequence
Variable Bit Rate Connections
Variable Bit Rate (VBR) connections can be classified as either:
•
Real-Time Variable Bit Rate (rt-VBR)—Specifies the connections that transmit at a rate varying
with time and can be described as bursty, often requiring large amounts of bandwidth when active.
The rt-VBR class is intended for applications that require tightly constrained delay and delay
variation such as compressed voice video conferencing.
For example, video conferencing requires real-time data transfer with bandwidth requirements that
can vary in proportion to the dynamics of the video image at any given time. The rt-VBR category
is characterized in terms of PCR, SCR (sustained cell rate), and MBS (maximum burst size).
•
Nonreal Time Variable Bit Rate (nrt-VBR)—Specifies the connections that are bursty but not
constrained by delay and delay variation boundaries. For those cells in compliance with the traffic
contract, a low cell loss is expected. Nontime critical data file transfers are an example of an
nrt-VBR connection. A nrt-VBR connection is characterized by PCR, SCR, and MBS.
Table 21-12 CBR Policing Definitions
Connection
Type ATM Forum TM spec. 4.0
conformance definition
PCR Flow
(1st leaky
bucket) CLP tagging
(for PCR
flow) SCR Flow
(2nd leaky
bucket) CLP tagging
(for SCR
flow)
CBR CBR.1
when policing set to 4
(PCR Policing only)
CLP(0+1) no off n/a
CBR When policing set to 5
(off) off n/a off n/a
CBR
PCR(0+1)
%Util
CDVT(0+1)
Policing (4 or 5)
For policing prompt:
4 = PCR policing only
5 = policing off
Note: BW allocation = (PCR)x(%Util)
10224
1
1
Trunk cell routing
restrict (Y/N) [Y]