Routing Engine Functions - Juniper M10i Hardware Manual

M10i Internet Router Hardware Guide

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 JUNOS System Basics and Services Command
Reference.
The Routing Engine includes the following functions and features:
The Routing Engine constructs and maintains one or more routing tables (see
Figure 14
called the forwarding table, which is then copied into the Packet Forwarding Engine.
The design of the ASICs allow the forwarding table in the Packet Forwarding Engine
to be updated without interrupting forwarding performance.
36
Routing Engine Architecture
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.
Storage and change management—Configuration files, system images, and
microcode can be held and maintained in primary and secondary storage
systems, permitting local or remote upgrades.
Monitoring efficiency and flexibility—The router supports functions such as alarm
handling and packet counting on every port, without degrading packet-forwarding
performance.
). From the routing tables, the Routing Engine derives a table of active routes,