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Routing Engine Architecture
M40 Internet Router Hardware Guide
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Figure 13:  Routing Engine Architecture
Routing Engine Functions
The Routing Engine handles all routing protocol processes, as well as the software processes 
that control the router’s interfaces, the chassis components, system management, and user 
access to the router. These routing and software processes run on top of a kernel that 
interacts with the Packet Forwarding Engine. For more information about the processes, see 
“Routing Engine Software Components” on page 26.
The Routing Engine includes the following functions and features:
„ Processing of routing protocol packets—The Routing Engine handles all packets that 
concern routing protocols, freeing the Packet Forwarding Engine to handle only packets 
that represent Internet traffic.
„ Software modularity—Because each software process is devoted to a different function 
and uses a separate process space, the failure of one process has little or no effect on the 
others. 
„ In-depth Internet functionality—Each routing protocol is implemented with a complete 
set of Internet features and provides full flexibility for advertising, filtering, and 
modifying routes. Routing policies are set according to route parameters (for example, 
prefix, prefix lengths, and Border Gateway Protocol [BGP] attributes).
„ Scalability—The JUNOS routing tables have been designed to hold all the routes in 
current networks with ample capacity for expansion. Additionally, the JUNOS Internet 
software can efficiently support large numbers of interfaces and virtual circuits.
„ Management interface—Different levels of system management tools are provided, 
including the JUNOS command-line interface (CLI), the JUNOScript application 
programming interface, the craft interface, and SNMP.
JUNOS
System
management
processes
Routing
protocols
Control
functions
System processes
Operating system
Kernel
Intel-based PCI platform
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