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Routing Engine Ar
chitecture
Figure 14: Routing Engine Architecture
JUNOS
software
System
management
processes
Routing
protocols
Control
functions
System processes
Operating system
Kernel
Intel-based PCI platform
1164
Routing En
gine Functions
The Routing Engine handles all routing protocol processes, as well as the software processes
that contr
ol the router’s interfaces, the chassis components, system man agement, 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 “Rout
ing Engine Software Components” on page 21.
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 t
hat represent Internet traffic.
• Software modularity—Because each software process is devoted to a different
function
and uses a separate process space, the failure o f 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 pol icies 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.
• Managem
ent 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.
• Storage and change management—Configuration files, s ystem images, and microcode
can be held and maintained in primary and secondary storage systems, permitting
local o
rremoteupgrades.
32 M5 and M10 Internet Routers Hardware Guide