An Atm Port; Performance Impact And Scalability Considerations - Juniper JUNOSE 11.2.X BGP AND MPLS Configuration Manual

JunosE 11.2.x BGP and MPLS Configuration Guide
Guidelines for Configuring Cell Concatenation and Cell Packing Timer for an ATM Port

Performance Impact and Scalability Considerations

Related Topics
528
You can specify up to four non-overlapping VPI/VCI ranges on the ATM port that has
been associated with the single pseudowire using the mpls-relay or router interface
tunnel command.
When a VPI/VCI range that you enter overlaps with already specified ranges, the newly
specified range becomes effective.
When a VPI/VCI range that you enter is a subset of an already defined range, the
specified range is not saved and an appropriate message is displayed on the CLI
interface.
When a VPI/VCI range that you enter encompasses one or more of the previously
defined ranges, the configuration attempt fails and an appropriate message is displayed
on the CLI interface.
Observe the following guidelines when you configure the maximum number of ATM cells
that the router can concatenate in a single packet and the identifier of the ATM Martini
cell packing timer that you want to use to detect timeout of the cell collection threshold:
You can configure the mpls-relay atm cell-packing mcpt-timer command on the ATM
port only after you associated a pseudowire with the port by using the mpls-relay or
route interface tunnel command.
You can use this command only on an ATM port (ATM AAL5 over ATM major interface).
When you attempt to run this command on other interface types, such as ATM
subinterfaces or Ethernet interfaces, this setting is not saved and an error message is
displayed.
Because the support for multiple ATM VCs over a single pseudowire requires one
pseudowire per ATM port and the number of ATM ports in a fully populated ERX chassis
is in the order of a few tens of ports, the number of pseudowires required is also of the
same range. As a result, no performance impact is caused by LDP signaling and state
management. The amount of memory needed and initial CPU activity on the line module
for a specified range are proportional to the number of VCs in the range.
You can scale the number of virtual circuits configured on an ATM line module up to
16,000. The VPI/VCI range specification on the ATM ports for this feature is controlled
by this limit. Depending on other VPI/VCI configuration on the ATM line module, the range
specification must not be greater than this scaled limit subtracted from the other VPI/VCI
configuration.
A VPI/VCI range with the maximum number of VCs does not cause the line module to
become unstable. Support for unified ISSU and high availability with a VPI/VCI range
configured with the maximum number of VCs is provided.
Example: Multiple ATM Virtual Circuits over a Single Pseudowire on page 559
mpls-relay atm vpi-range vci-range
mpls-relay atm cell-packing mcpt-timer
Copyright © 2010, Juniper Networks, Inc.