Packet Flow On Acx Series Routers - Juniper ACX4000 Hardware Manual

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Figure 3: ACX4000 Interface Port Mapping

Packet Flow on ACX Series Routers

The class-of-service (CoS) architecture for ACX Series routers is in concept similar to that for MX Series
routers. The general architecture for ACX Series routers is shown in Figure 4 on page 7.
Figure 4: ACX Series Router Packet Forwarding and Data Flow
Based on the model, ACX Series routers contain a built-in Routing Engine and Packet Forwarding Engine
and can contain both T1/E1 and Gigabit Ethernet Ports.
The Packet Forwarding Engine has one or two "pseudo" Flexible PIC Concentrators. Because there is no
switching fabric, the single Packet Forwarding Engine takes care of both ingress and egress packet
forwarding.
Fixed classification places all packets in the same forwarding class, or the usual multifield (MF) or
behavior aggregate (BA) classifications can be used to treat packets differently. BA classification with
firewall filters can be used for classification based on IP precedence, DSCP, IEEE, or other bits in the
frame or packet header.
However, the ACX Series routers can also employ multiple BA classifiers on the same physical interface.
The physical interfaces do not have to employ the same type of BA classifier. For example, a single
physical interface can use classifiers based on IP precedence as well as IEEE 802.1p. If the CoS bits of