7-22 Cisco BPX 8600 Series Reference
ATM Connection Configuration
UBR Connections
The unspecified bit rate (UBR) connection service is similar to the ABR connection service for
bursty data. However, UBR traffic is delivered only when there is spare bandwidth in the network.
This is enforced by setting the CLP bit on UBR traffic when it enters a port.
Therefore, traffic is served out to the network only when no other traffic is waiting to be served first.
The UBR traffic does not affect the trunk loading calculations performed by the switch software.
The parameters for a UBR connection are shown in Figure 7-10 in the sequence in which they occur
during the execution of the addcon command.
The UBR policing definitions are summarized in Table 7-7.
Figure 7-10 UBR Connection Prompt Sequence
Table 7-7 UBR 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)
UBR
UBR.1
when CLP setting =
no
CLP(0+1)
no off n/a
UBR
UBR.2
when CLP setting =
yes
CLP(0+1)
no
CLP(0)
yes
UBR
PCR(0+1)
%Util (default to 1%)
CDVT(0+1)
FBTC (AAL5 Frame based traffic control, enable/disable)
CLP Setting (yes, no) (same as CLP tagging)
10228
Trunk cell routing
restrict (Y/N) [Y]
