Juniper JUNOS 10.1 - CONFIGURATION GUIDE 1-2010 Configuration Manual page 379

into individual ATM cells and forwarded to the ATM virtual circuit configured for the
far-end router.
The uses for the four transport modes are defined as follows:
To tunnel IP packets over an ATM backbone, use the default standard AAL5
transport mode.
To tunnel a stream of AAL5-encoded ATM SAR-PDUs over an MPLS or IP
backbone, use Layer 2 circuit AAL5 transport mode.
To tunnel a stream of ATM cells over an MPLS or IP backbone, use Layer 2 circuit
cell-relay transport mode.
To transport ATM cells over an MPLS core network that is implemented between
other vendors switches or routers, use Layer 2 circuit trunk transport mode.
NOTE: You can transport AAL5-encoded traffic with Layer 2 circuit cell-relay transport
mode, because Layer 2 circuit cell-relay transport mode ignores the encoding of the
cell data presented to the ingress interface.
When you configure AAL5 mode Layer 2 circuits, the control word carries cell loss
priority (CLP) information by default.
The Layer 2 circuit trunk transport mode is not supported on the ATM2 IQ
OC48c/STM16 PIC.
To configure Layer 2 circuit AAL5, Layer 2 circuit cell-relay, or Layer 2 circuit trunk
mode, you must perform the following tasks:
Identify the interface as an ATM2 IQ interface by including the
1.
statement at the [edit interfaces at-fpc/pic/port atm-options]
[edit interfaces at-fpc/pic/port atm-options]
pic-type atm2;
2. Include the atm-l2circuit-mode
hierarchy level, specifying
pic-number]
[edit chassis fpc slot-number pic pic-number]
atm-l2circuit-mode (aal5 | cell | trunk trunk );
By default, the trunk mode uses user-to-network interface (UNI) mode. The trunk
option can be UNI or network-to-network interface (NNI). For more information
about UNI and NNI, see the JUNOS VPNs Configuration Guide and the JUNOS
Feature Guide.
Transport mode is per PIC, not per port. If you do not include the
statement in the configuration, the ATM2 IQ PIC uses standard
atm-l2circuit-mode
AAL5 transport mode. If you configure Layer 2 circuit cell-relay, Layer 2 circuit
AAL5 transport mode, or Layer 2 circuit trunk mode, the entire ATM2 PIC uses
the configured transport mode.
Chapter 13: Configuring ATM Interfaces
statement at the [edit chassis fpc slot-number pic
, , or
aal5 cell trunk
Configuring Layer 2 Circuit Transport Mode
pic-type atm2
hierarchy level:
:
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