Specifications

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sections of the software. In addition, having clean software interfaces between
modules facilitates software development and maintenance, enabling faster
customer response and delivery of new features.
Other fail-over capabilities supported are in context of Circuit or Router failure:
4.3.2 Automatic Protection Switching (APS)
APS is used by SONET add/drop multiplexors (ADMs) to protect against circuit
failures. APS is commonly used to protect against failures between the ADM and
a router. With the JUNOS implementation of APS, you can also use APS to
protect against failing routers when more than one router is connected to an APS.
When a circuit or router fails, a backup circuit or router immediately takes over.
4.3.3 Virtual Router Redundancy Protocol (VRRP)
On Gigabit Ethernet interfaces, VRRP allows hosts on a LAN to make use of
redundant routers on that LAN without requiring anything more than the static
configuration of a single default route on the hosts. The VRRP routers share the
IP address corresponding to the default route configured on the hosts. At any
instant in time, one of the VRRP routers is the master (active) and the others are
backups. If the master fails, one of the backup routers is elected to become the
new master router, thus always providing a virtual default router and allowing
traffic on the LAN to be routed without relying on a single router.
4.3.4 MPLS Traffic Engineering and Fast Reroute
The traffic engineering features supported by the JUNOS Internet software allow
ISPs to manage around network failures. Lacking the pre-failure transmission
capacity, the M40 system provides tools that permit an ISP to determine the best
method for distributing the current traffic load over available resources without
creating congestion and further destabilizing the network.
MPLS Fast reroute provides a mechanism for automatically rerouting traffic if a
node in an LSP fails, thus minimizing the loss of packets traveling over the LSP.
When you establish primary and secondary LSPs, alternate sessions to be used
for rerouting are established at the same time. If a node in an LSP fails, the
packets are automatically rerouted to the path by the alternate session. The
rerouting remains in effect until the primary LSP or one of the secondary LSPs
again becomes operational.
4.4 Mean-Time Between Failure Data for Juniper Networks’ Components
4.4.1 Mean-Time Between Failure Data for the M20 and M40
Predicted Board MTBF
Component
MTBF in (khrs) at
40°° C
MTBF in (khrs) at
25°° C
M20 SSB (1:1) 306 515
M20 Backplane 378 686
M20 Routing Engine (1:1) 450 750
M20 Power Supplies (1:1) 295 705
M20 Fan Trays (2:3) 2100 3700
M40 SCB 262 440
M40 Back plane 425 686
M40 Power Supplies (1:1) 300 675
M40 Fan Trays (1:1) 3000 5250
Flexible PIC Concentrator 406 704
POS OC12-1 SMF 707 1158
POS OC12-1 MMF 881 1434
POS OC3-A SMF PIC 464 769
POS OC3-B SMF PIC 643 1078
POS OC3-A MMF PIC 597 985
OC3-B POS OC3-B MMF PIC 931 1555
OC48 Module 788 1300