Cisco Systems Network Router manual Ctd Cdv, Traffic Metric, Class of Service Tables

Chapter 4 Planning Intermediate Route Selection

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:

•Destination address

•AW

•CTD

•CDV

•Available bandwidth

•Available logical connection numbers (LCNs)

•Port ID

The end result is the set of SPTs shown in Table 4-1.

Table 4-1 Pre-calculated Routing Tables

Traffic Metric

AW

CTD

CDV

Class of Service Tables

CBR, rt-VBR, nrt-VBR, ABR, UBR

CBR, rt-VBR, nrt-VBR

CBR, rt-VBR

The SPTs can be divided into the three groups listed in the Traffic Metric column in Table 4-1. For each 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.

Table 4-2 Supported Service Classes for MGX and SES Nodes

Service
Class	Acronym Definition	Guidelines
CBR	Constant bit rate	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.
rt-VBR	Real-time variable bit rate	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).
nrt-VBR	Non-real-time variable bit	Use for non-real-time applications with bursty traffic. Category is characterized
	rate	in terms of a PCR, SCR, and MBS.
ABR	Available bit rate	Use to allow ATM layer transfer characteristics provided by the network to
		change after the connection is established. Flow control mechanism is specified.
UBR	Unspecified bit rate	Use for unspecified bit-rate ranges. This setting provides only maximum bit-rate
		configuration—no bit rate is guaranteed.

	Cisco PNNI Network Planning Guide for MGX and SES Products, Release 5
4-4	Part Number OL-3847-01 Rev. D0, April, 2004