5-110
Cisco MGX 8850 Routing Switch Command Reference
Release 2.0, Part Number 78-10467-04 Rev C0, October 2001
Chapter5 PNNI Commands
dsppnni-routing-policy
Related Commands
cnfpnni-routing-policy
On demand routing The current rule for on-demand routing is firstfit or bestfit.
The firstfit routing policy selects th e firs t r o ut e f o und th at goes to the
destination. The time for fin di ng a ro u te is the least possible, but the optimal
route may not be selected.
The bestfit policy selects a route based on:
•The least-cost route, where the su m o f al l administrative weights in both
directions of the rou te m u s t b e les s th a n maxCost.
•Link verification.
•Path constraint checks.
•Avoidance of blocked nodes and links.
•Checking limits in the desig nat ed t ra nsi t l ist (DTL).
SPTpath holddown
time The minimum time that can ela pse between consecutive calculations that
generate routing tables on border nodes.
Units:100 milliseconds.
Range: 1 (0.1 seconds)–600 (60 seconds).
Note The current release does not support border nodes, so this value
must remain off.
AW Bac k-
groundTable The flag that enables or disabl es a dm inistrative weight (AW) for the
background routing table. The AW is the cost to t raffic that traverses that path.
The metric AW can be specified on the in ter fa ce an d by t h e ser v ic e cl ass (or
QoS class), and it is associa ted w i th ea ch li nk. AW is a defining factor when
routes are selected. The AW parameters inf lu en ce how P N NI s el ect s p ath s i n
the peer group, and therefore how it distributes each SVC and SPVC. PNNI
route selection can also key on AW to exclude certain links from routing, such
as defining a backup link for use onl y wh en the re is no av ai la ble ban dwidt h on
the primary link.
The AW for a path is the sum of all AWs at each port egr ess for both directions
on the path.
CTD Back-
groundTable The flag that enables or disables cell t ransfer delay (CTD) for the background
routing table. CTD is the time interval between a cell exiting s ource node and
entering the destination node.
CDV Back-
groundTable The flag that enables or disables ce ll dela y vari ation (CD V) for th e backgr ound
routing table. CDV is a component of cell transfer delay, and is a quality of
service (QoS) delay parameter associated with CBR and VBR service. Cell
Delay Variation is the variation of de lay between cells, measured peak to peak.