Juniper MX240 Hardware Manual page 36

MX240 Ethernet Services Router Hardware Guide
Midplane
The midplane is located toward the rear of the chassis and forms the rear of the DPC
card cage (see Figure 5 on page 8). The DPCs and SCBs install into the midplane
from the front of the chassis, and the power supplies install into the midplane from
the rear of the chassis. The cooling system components also connect to the midplane.
The midplane performs the following major functions:
Figure 5: Midplane
Dense Port Concentrators (DPCs)
A Dense Port Concentrator (DPC) is optimized for Ethernet density and supports up
to 40 Gigabit Ethernet or four 10-Gigabit Ethernet ports (see Figure 6 on page 9).
The DPC assembly combines packet forwarding and Ethernet interfaces on a single
board, with four 10-Gbps Packet Forwarding Engines. Each Packet Forwarding Engine
consists of one I-chip for Layer 3 processing and one Layer 2 network processor. The
DPCs interface with the power supplies and Switch Control Boards (SCBs).
The router has two dedicated DPC slots. DPCs install horizontally in the front of the
router (see Figure 6 on page 9). One multifunction slot numbered
either one DPC or one SCB. The DPC slots are numbered
top. A DPC can be installed in any slot on the router that supports DPCs.
You can install any combination of DPC types in the router.
DPCs are hot-removable and hot-insertable, as described in "Field-Replaceable Units
(FRUs)" on page 87. When you install a DPC in an operating router, the Routing
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Midplane
Data path—Data packets are transferred across the midplane between the DPCs
through the fabric ASICs on the SCBs.
Power distribution—The router power supplies connect to the midplane, which
distributes power to all the router components.
Signal path—The midplane provides the signal path to the DPCs, SCBs, Routing
Engines, and other system components for monitoring and control of the system.
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