Cisco Network Router User Manual page 74

How MGX and SES Nodes Select Routes
an external network, the use of the 0-length prefix allows the administrator to specify that all calls that
do not match a longer prefix should be routed to the external network. If the 0-length prefix is not used,
the administrator must manually configure static addresses for all external destinations.
MGX and SES nodes generate routing tables using PTSE information from other nodes and the Dijkstra
SPF Algorithm. The pre-computed routing tables are derived by applying the following information
from the PTSEs:
•
•
•
•
•
•
•
The end result is the set of SPTs shown in
Table 4-1
Traffic Metric
AW
CTD
CDV
The SPTs can be divided into the three groups listed in the Traffic Metric column in
traffic metric, a class of service SPT is created for each class of service listed in the Class of Service
Tables column. The service classes are defined in
Table 4-2 Supported Service Classes for MGX and SES Nodes
Service
Class Acronym Definition
CBR Constant bit rate
rt-VBR Real-time variable bit rate
nrt-VBR Non-real-time variable bit
rate
ABR Available bit rate
UBR Unspecified bit rate
Cisco PNNI Network Planning Guide for MGX and SES Products, Release 5
4-4
Destination address
AW
CTD
CDV
Available bandwidth
Available logical connection numbers (LCNs)
Port ID
Pre-calculated Routing Tables
Guidelines
Use to limit connections to a static amount of bandwidth that is continuously
available until the connection is torn down. The amount of bandwidth is
characterized by the peak cell rate (PCR) value.
Use for real-time applications that require tightly constrained delay and delay
variation (voice/video applications). Category characterized in terms of a PCR,
sustainable cell rate (SCR), and maximum burst size (MBS).
Use for non-real-time applications with bursty traffic. Category is characterized
in terms of a PCR, SCR, and MBS.
Use to allow ATM layer transfer characteristics provided by the network to
change after the connection is established. Flow control mechanism is specified.
Use for unspecified bit-rate ranges. This setting provides only maximum bit-rate
configuration—no bit rate is guaranteed.
Chapter 4
Table 4-1.
Class of Service Tables
CBR, rt-VBR, nrt-VBR, ABR, UBR
CBR, rt-VBR, nrt-VBR
CBR, rt-VBR
Table 4-2.
Part Number OL-3847-01 Rev. D0, April, 2004
Planning Intermediate Route Selection
Table 4-1. For each