Juniper JUNOSE 11.2.X BGP AND MPLS Configuration Manual page 562

JunosE 11.2.x BGP and MPLS Configuration Guide
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For more information on the guidelines to be followed when you configure VCI/VPI ranges
for transportation of a subset of ATM VCs on a single pseudowire, see "Guidelines for
Configuring VPI/VCI Ranges of ATM Virtual Circuits" on page 527.
You can also specify concatenation of multiple ATM cells to be sent in a single
MPLS-labeled packet for efficient usage of the backbone bandwidth. If you do not specify
cell concatenation, each individual ATM cell is MPLS-labeled and transmitted on the
pseudowire. You can use the mpls-relay atm cell-packing mcpt-timers command to
configure the following parameters that control how the router performs cell
concatenation:
Maximum number of ATM cells that the router can concatenate in a single packet.
Values (in microseconds) for each of the three ATM Martini cell packing timers
maintained on the router. These timers define the time threshold that the router uses
to concatenate ATM cells and transmit the cells in an MPLS packet on the pseudowire.
Based on this configuration, the router attempts to concatenate the specified maximum
number of ATM cells into an MPLS packet within the time interval allowed by the ATM
Martini cell packing timer you selected. When the router detects that the allotted time
interval has expired, the router forwards the MPLS packet even if it contains fewer than
the specified maximum number of aggregated cells per packet. The cell concatenation
functionality is controlled by the timer values and the maximum number of cells to be
concatenated. The LDP signaling protocol option to negotiate cell concatenation
(maximum number of concatenated ATM cells) is not used.
For more information on the guidelines to be followed when you configure cell
concatenation and cell packing timer identifiers for transporation of ATM VCs on a single
pseudowire, see "Guidelines for Configuring Cell Concatenation and Cell Packing Timer
for an ATM Port" on page 528.
When you add the MPLS Martini circuit configuration on an ATM port, you cannot add
the interface label space RSVP configuration on the same ATM port. Therefore, you can
configure an ATM port with either the interface label space RSVP configuration or the
MPLS Martini circuit at the same time. You cannot configure both the interface label
space RSVP configuration or the MPLS Martini circuit on the same ATM port at the same
time.
The ATMx port is not changed to the Loss of Signal (LOS) state, which denotes the
number of times for which the incoming optical signal is all zeros for at least 100
microseconds, when a failure is detected on the pseudowire. Possible causes might
include a cable disconnection, excessive attenuation of the signal, or faulty equipment.
The changeover to the LOS state for the ATM port is not performed because only a subset
of the ATM virtual circuits are configured to be transported on the pseudowire. The ATM
virtual circuits on the same ATM port that are not associated with the single pseudowire
and are not present in the specified subset continue to function in the desired manner,
without being affected by the failure detected on the pseudowire. If the ATM port was
moved to an LOS state, all ATM virtual circuits on the same port that are configured for
functionality other than the multiple VCs over single pseudowire functionality are also
disrupted.
Copyright © 2010, Juniper Networks, Inc.