Cisco Systems Network Router Additional Routing Features in MGX and SES Nodes, Preferred Routing

Chapter 4 Planning Intermediate Route Selection

Additional Routing Features in MGX and SES Nodes

Table 4-3 Link Selection Parameters Required for Various Classes of Service

Service							CLR01	CLR0+12
Class	Address	AW	maxCR	AvCR	CTD	CDV
CBR	Required	Required	Required	Required	Required	Required	Required	Required
rt-VBR	Required	Required	Required	Required	Required	Required	Required	Required
nrt-VBR	Required	Required	Required	Required	Required	—	Required	Required
ABR	Required	Required	Required	Required	—	—	—	—
UBR	Required	Required	Required	—	—	—	—	—

1.CLR0 is the cell loss ratio for cells with the Cell Loss Priority bit set to 0.

2.CLR0+1 is the cell loss ratio for all cells with the Cell Loss Priority bit set to either 0 or 1.

When two parallel links are available along the route, the controller chooses a link based on the configuration of the switch. The link selection options are:

•AW—Selects the link with the least AW in the egress direction. This is the default.

•AvCR—Selects the link with the largest AvCR in the egress direction.

•maxCR—Selects the link with the largest maxCR in the egress direction.

•loadbalance—Selects links randomly so that one link does not become overburdened while the other is idle.

Additional Routing Features in MGX and SES Nodes

The following sections describe additional routing features you might want to consider when planning a PNNI network.

Preferred Routing

Preferred routes allow the switch administrator to define a specific route between the source and destination nodes, and then specify this route as the preferred route when defining SPVCs. If the connection is configured as a directed route, no other route is allowed, even if the route fails. If the connection is not configured as a directed route, other routes are considered when the preferred route is not available. When other routes are required, the switch can use the pre-calculated routing tables or on-demand routing.

Preferred routing was introduced in Release 3.0.00 and is supported on the MGX 8830, MGX 8850 (PXM1E), MGX 8850 (PXM45), and MGX 8950 switches and the MGX 8880 Media Gateway. Release 3.0.20 and later support preferred routing on SES nodes.

Note Preferred routes created with Release 3 software cannot be gracefully upgraded to Release 4 or later preferred routes.

	Cisco PNNI Network Planning Guide for MGX and SES Products, Release 5
Part Number OL-3847-01 Rev. D0, April, 2004		4-7