Juniper JUNOSE 11.2.X BGP AND MPLS Configuration Manual page 596

JunosE 11.2.x BGP and MPLS Configuration Guide
Related Topics
560
the ATM cells with a control word, adds the pseudowire label and transport label, and
forwards the resulting MPLS labeled packet to be delivered to PE2.
PE2 receives the MPLS-labeled packet and strips the labels on the packet. The
bottommost label indicates to PE2 that the packet contains ATM cells to be forwarded
on the ATM port connected to CE2. PE2 extracts the ATM cells from the packet, checks
whether the VPI/VCI value on the ATM cells fall within the configured VPI/VCI range on
the ATM port, and forwards those ATM cells whose VPI/VCI values fall within the
configured range to CE2. PE2 discards the ATM cells that do not fall within the configured
VPI/VCI range. For data traffic traversing from CE2 to CE1, the same workflow is followed
with the roles reserved—PE2 as the transmitter of MPLS labeled packet and PE2 as the
receiver of MPLS labeled packet.
NOTE: The support for multiple VCs over a single pseudowire uses the the ATM n-to-one
VCC cell transport (0x0009) pseudowire (PW) type in LDP signalling messages. This
PW type is also used in the signaling messages by the ATM Martini circuit feature, which
enables cell relay encapsulation on an ATM subinterface, that transports ATM cells
associated with an ATM subinterface on a single pseudowire.
Because the same PW type is used for both the cell relay encapsulation for a single VC
and multiple VCs, you can successfully configure an ATM subinterface Martini circuit
(cell relay for a single VC) on one PE router and an ATM port Martini circuit (cell relay
for multiple VCs) on another PE router, and bring up the pseudowires for this
configuration. In such a scenario, traffic black holes might occur and rewriting of the
ATM cell header takes place. In this topology, on the PE router configured with an ATM
subinterface Martini circuit, the VPI/VCI values of all the ATM cells received on the
pseudowire are rewritten to match with the configuration on the ATM subinterface. On
the PE router configured with an ATM port Martini circuit, all the ATM cells received on
the pseudowire are examined to determine whether they fall within the configured
VPI/VCI range. If the ATM cells do not fall within the configured VPI/VCI range, they
are discarded.
Multiple ATM Virtual Circuits over a Single Pseudowire Overview on page 524
mpls-relay atm vpi-range vci-range
mpls-relay atm cell-packing mcpt-timer
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