JUNOS Advance

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Solution Brief
Carrier Class
Routing with the
JUNOS Advantage

Carrier Class Routing with the JUNOS Advantage
Page 2

Triple-play applications have rigorous uptime requirements
– requirements more commonly associated with Layer 1
transport such as SONET/SDH. JUNOS supports features like
nonstop forwarding (NSF), graceful restart, in-service software
upgrade (ISSU), Bidirectional Forwarding Detection (BFD),
and other features, which together make IP networking as
failure-safe and reliable as telephony networks. JUNOS had
led the way towards enabling the convergence of the most
demanding applications in service-provider core networks.

Security

Juniper Networks JUNOS operating system is the first routing
OS designed specifically for deployment in rigorous serviceprovider networks. It forms a fundamental building block of the
Infranet, transcending the monolithic software architectures
of older Internet operating systems. JUNOS was designed
for today’s dynamic IP routing and services, and it has
continued to thrive in the largest IP networks in the world.

SNMP

The JUNOS operating system was conceived and implemented
as a modular design, wherein each process runs in protected
memory to guard against system crashes and to ensure
that runaway applications do not corrupt each other
— the failure of one module does not adversely impact the
entire operating system. Between these independent
modules are clean, well-defined interfaces that provide
inter-process communication, resulting in highly reliable
software architecture. By eliminating the security, stability,
performance, and operational issues that are inherent in
legacy operating systems, routers running JUNOS meet the
advanced requirements of distributed converged networks.

Chassis Mgmt

Demands on IP networks have evolved dramatically over the
last decade. This is most apparent in core networks, where
service providers continue to make the transition from best-effort
Internet to a singular IP/MPLS infrastructure that delivers assured
experiences for the triple play of data, voice, and video. This new
network paradigm is the Infranet, where the performance and
assurance guarantees of private networks are extended to the
public network infrastructure. This inevitable evolution increases
the technical demands on network hardware and software,
and particularly on the operating system of core routers.

Interface Mgmt

JUNOS: The Foundation of Secure and Assured Networks

Protocols

Executive Summary

Operating System
TM

The advantage of JUNOS over competitive alternatives revolves
around security, uptime, performance, and operational benefits.

Page 3 Solution Brief

Security

Operations

Network security is only as strong as the weakest link _ the
most readily compromised device sets the bar for the entire
network. Juniper Networks delivers the most advanced set of
mechanisms for fully protecting routers from outside attack.

Purposely designed to reduce operational complexities and issues
that occur in networks, JUNOS includes a broad set of tools and
features to simplify deployment, ease remote management and
support, and facilitate fast restoration. Juniper Networks routers
are far easier to upgrade than competitive alternatives, which
contain thousands of software images for their enterprise-class
product lines to evaluate, analyze, and test for interoperability.

JUNOS ensures that full router control is maintained when
under attack, so that the system can quickly be accessed to add
needed filters and policies for blocking destructive traffic. Juniper
Networks routers also provide dynamic filter updates during
attack. Network managers can quickly modify policies to drop or
to rate-limit traffic of a particular profile. Finally, JUNOS supports
a large number of filtering terms with protected resources, so that
performance won’t degrade when security features are activated.

TM

Uptime
JUNOS separates software functions into modular components,
which prevents minor problems from progressing to full system
crashes – a common chain of events in traditional, commingled
OS architectures. A next-generation command-line interface
(CLI) and configuration tool allows operators to build and
review CLI changes offline. Other high-availability features are
discussed in the section Building High-Availability Services.
Performance
Configuring simple prioritization mechanisms in legacy
routing systems can quickly degrade performance. JUNOS
maintains high levels of quality of service (QoS) control
and throughput when they are needed most – during
the most demanding periods of network congestion.

% of Line Rate

Juniper

6.4

7.0

7.1

One Train!
With one code train, the JUNOS operating system is standard
across the entire Juniper Networks routing product line. Features
are available on all appropriate platforms, enabling rapid feature
development and consistency throughout the network.
A unique operational advantage of JUNOS is the commit
process of the CLI. This is useful for verifying that a
configuration change works correctly and that it does
not prevent management access to the router.

Addition of
new service
features

Interim
Configuration
Commit Check
and
Confirmed

Traditional
Router

Y
Configuration
in Text File

Complexity of Packet Processing

Modular software architectures are essential for the
sorting and scheduling of traffic, to ensure that the most
important applications have first priority with limited
link resources. With JUNOS, network operators can
support growing traffic volume and applications on the
network, without impacting existing business needs.

Load

Copy,
Save

Candidate
Configuration

Active
Configuration
“X” minutes
without
commiting

Commit?

N

Automatic
Rollback

If the change prevents access or causes other errors, an
automatic rollback to the previous configuration restores
access, after the rollback confirmation timeout expires. Juniper
Networks J-series routers even have a hardware “rescue button”
that any onsite staff can engage to roll back to a known,
working configuration – without a system reboot – eliminating
the need for a truck roll when systems become isolated.

Carrier Class Routing with the JUNOS Advantage
Page 4

Building High-Availability Services
Multiservice IP/MPLS networks take advantage of the favorable
economics and scalability of IP/MPLS data platforms. Leading
the charge to bring diverse networks together on an IP/MPLS
infrastructure, Juniper Networks developed JUNOS around the
critical requirements of network availability and reliability. The
IP infrastructure must continue to serve the needs of legacy
applications as well as new service offerings such as video,
voice, and virtual private networks (VPNs) for enterprise data.
These networks are rated based on performance characteristics
such as latency, jitter, dropped packets, and availability. To
deliver value-added IP services that are backed by service
level agreements (SLAs), the service provider’s network
must maintain a very high level of service availability.
A Holistic Approach to Dependable IP Services
When a link or line card fails, there are generally alternative
paths available and the stress of routing protocol updates on
the control plane is minimal. But software can also contribute
to network element failures, whether due to operation errors,
routing protocol failures, or other software faults. Service
providers depend on reliable software, and the stability
features of a router’s OS must be designed into the system
architecture during the earliest stages of development.
The main requirement of core networking environments is
high availability. JUNOS provides software-based resiliency
that prevents hardware failures from occurring in the first
place. This gives Juniper Networks routers unparalleled
stability in large service-provider networks. JUNOS software
takes a holistic approach to providing stability, which is
based on the four cornerstones of stable router design:
• An extremely resilient system architecture, which
provides a clean separation between the control
plane and the packet forwarding plane
• A modular router OS composed of loosely coupled
functional modules, which are controlled and
monitored by a master executive module
• Robust, scalable, routing protocol implementations,
which are designed to converge quickly and
support nonstop packet forwarding (NSF)
• A comprehensive set of industry-standard protection
mechanisms such as SONET Automatic Protection
Switching (APS), MPLS Fast Reroute (FRR), and BFD

While the stability of a router OS can be tested in an
experimental network, the ultimate test of OS stability can
occur only in a production network. With over seven years
of operational experience in the world’s largest serviceprovider networks, JUNOS has demonstrated its stability
during the most explosive period of Internet growth.
A Uniform Code Base to Ensure Reliability
Juniper Networks holistic approach to IP/MPLS begins
with the software design process. While other vendors
maintain a patchwork of router code that may be tied to
selected platforms, features, applications, or interfaces, each
quarterly release of JUNOS OS runs consistently across all
Juniper Networks routing platforms and feature sets.
The uniformity of JUNOS software greatly simplifies the
upgrade and maintenance process for service providers. A
customer can readily apply new releases without risking
configuration errors from incompatible versions and releases.
Instead of requiring that customers perform a “feature
versus hardware” compatibility process, JUNOS guarantees
full feature carry-forward across platforms and interfaces.
This uniform code base allows Juniper Networks
software developers to perform rigorous regression
testing between JUNOS OS releases. Features are added,
supported, tested, and carried forward consistently.
Built for IP/MPLS Reliability
Juniper Networks pioneered modern router architecture by
cleanly separating the control plane from the forwarding
plane for high resiliency. As previously described, this
service-provider-class architecture consists of separate
components for the Routing Engine (control plane) and
the Packet Forwarding Engine (forwarding plane).
The control plane, implemented in JUNOS software running
on the Routing Engine, maintains peer relationships, runs
routing protocols, builds the routing table, and creates the
forwarding table. It then exports the table to the Packet
Forwarding Engine, the key component of the forwarding
plane, which forwards the packets in hardware.
The separation of routing from forwarding provides resiliency
by isolating failures. For example, Denial of Service (DoS)
attacks that occur in the traffic flow do not affect the control
plane. If a routing protocol process needs to be restarted,
forwarding can continue using protocol graceful restart.

Page 5 Solution Brief

Modular Software Design
Rather than placing all routing code in a monolithic OS, JUNOS
software consists of a set of individual processes. JUNOS
was built for scale, using modern operating system design
principles that include a robust, protected-memory architecture,
which allocates protected address space for each process.
The modular JUNOS architecture is more dependable than
the monolithic architecture. If any part of the monolithic
program fails, the operating system crashes. A bug in
Simple Network Management Protocol (SNMP), for example,
crashes the operating system. Such a fault can cause the
line cards to crash or restart, resulting in hundreds of
seconds of downtime. In contrast, the automatic software
process failover mechanism in JUNOS software supports
nonstop forwarding while the process is restarted.
JUNOS Modular Operating System

Monolithic Operating System

JUNOS Kernal

Interface
Process

Chassis
Process

OS

Chassis Process

Routing
Process

Interface Process

SNMP
Process

Routing Process

Modularity also allows users to upgrade a specific JUNOS
module without rebooting the system, and allows software
developers to make modular upgrades to the software.
Control Plane Reliability
Another way that JUNOS ensures high availability is by
prioritizing routing updates and Interior Gateway Protocol
(IGP) signaling, even during periods of network congestion or
instability. When the router receives routing updates, its control
plane responds rapidly, even when the forwarding plane is
under heavy load. In legacy architectures, the update process
can be delayed when large traffic bursts are being processed.
Troubleshooting Features
Due to its modularity, the JUNOS operating system provides
visibility of the CPU and memory utilization of individual
processes for diagnostic purposes. To ensure dependable
operation, JUNOS software automatically restarts failed
processes. JUNOS also logs error conditions and can identify
“resource hogging” processes (such as memory or CPU).
Armed with this information, system administrators can
discern when to proactively restart software processes, and
prevent problems before they cause service outages.

For example, a routing configuration error can lead to a huge
routing table that consumes all of a router’s real memory. With
virtual memory, Juniper Networks routers remain operational.
After living through the sort of condition that would cause an
outage on legacy platforms, Juniper Networks routers can be used
to debug the problem and get the whole network back online.
Robust Routing Protocols

SNMP Process
Peridoc
Packet
Mgmt.
Process

The virtual memory in JUNOS enables it to operate
after it has run out of real memory. When network
messaging becomes unstable and excessive memory
is consumed, the router remains operational while the
cause of the memory overrun is being debugged.

Industrial-strength routing protocol implementations are
required for the successful operation and growth of large
service-provider networks. Routers implement routing protocols
to exchange information used to calculate forwarding paths
through the provider’s network and across the Internet. The
forwarding paths must support the delivery of IPv4, IPv6, and
MPLS traffic. Among the standards-based routing protocols
that must be supported by a carrier-class router are the BGP4, RIPv2, OSPF, and IS-IS. Since MPLS is being used within
core IP networks to manage bandwidth and implement
QoS for IP flows, MPLS constraint-based routing, traffic
engineering (TE), and FRR features must also be supported.
JUNOS software provides feature-rich, robust, and stable
implementations of these protocols. JUNOS benefits from
an experienced engineering staff and from seven years
of industry feedback on our implementation. No other
router OS implementations can match the feature set,
scalability, performance, security, and robustness of the
JUNOS software routing protocol implementations.
Upgrading with Sanity
The upgrade process in a service-provider network needs
to be predictable and side effects must be minimized, or
the consequences (in terms of angry customers) can be
devastating. Toward this end, software releases must function
properly with other routers, and must not contain the
serious regressions that come from unscheduled releases.

Carrier Class Routing with the JUNOS Advantage
Page 6

Cross-Platform Support

Multivendor Interoperability

To successfully manage their software-upgrade schedule,
service providers require an operating system that is based on
a single release train and that executes on multiple platforms.
Support for a single release train eliminates the problem of
trying to determine whether a particular service-enabling
feature is supported by a specific software release, hardware
chassis, and line-card combination. Providing a consistent set
of features that execute on multiple platforms means that the
services supported by the router operating system run reliably
in the core, at the edge, and at individual customer sites.

Another facet of cross-platform support is the ability
to interoperate with other vendors’ operating systems.
Juniper Networks has many years of experience in
providing, designing, and implementing solutions
that interoperate with other routing platforms.

Unlike router operating systems from other vendors,
JUNOS software simplifies the mix of knowledge that is
necessary to remain current with router code updates. Each
router operating system from other core router vendors
operates on only a single platform, which forces providers
to add yet another operating system into the matrix.
In contrast, JUNOS software allows service providers to
leverage a single router operating system that runs on core
routers (T-series platforms), edge routers (M-series platforms),
and customer premises equipment (J-series platforms). This
approach simplifies network operations and provides service
continuity. For example, the configuration of VPN services and
QoS classification and marking is consistent across all platforms.

Our interoperability in multivendor environments has been
a key element in our success to date, with Juniper Networks
systems deployed side-by-side with equipment from other
vendors (such as Cisco) in many enterprises worldwide – in
government, research, and education networks, as well as
the 25 largest service-provider networks in the world.
Dependable Software Release Schedule
Service providers demand a reliable and consistent software
update schedule, to successfully manage growth and support
the rollout of new services in their networks. Because software
features and router hardware support are tightly coupled,
router vendors must have the foresight to envision future
carrier requirements and support those software needs in
hardware. For example, Juniper Networks implemented IPv6
forwarding in its processor hardware before carrier demand.
We also maintain a stable IPv6 protocol suite in JUNOS software
while delivering support for IPv6 traffic – without requiring
special builds, software branches, or hardware updates.

TM

Other

TM

Other

TM

Other

Other

Other

TM

Other

TM

Other

Other

TM

TM

TM

Page 7 Solution Brief

Many vendors issue software updates on a haphazard schedule,
with missing or late features. JUNOS software updates are
released on a regular schedule, with the promised feature set.
JUNOS software updates run on all T-series, M-series, and Jseries routers, facilitating the seamless and rapid deployment
of new services by supporting IP/MPLS functionality on
provider, provider edge, and CPE routers. In addition, JUNOS
software includes a feature-rich IP services toolkit.
Juniper Networks Leadership Role with JUNOS
JUNOS software was first released in 1998, with the
launch of the M40 Internet backbone router. Since
then, the Internet has experienced tremendous growth,
with a consequent increase in the number of hosts, the
speed of core trunks, application complexity, and the
economic value and importance of IP services.
Throughout this expansion, service providers have required
frequent routing software updates to provide new features
and support the rollout of revenue-generating services. Service
providers continue to experience enormous competitive and
economic pressures: to deploy the latest feature set for the
enhanced reliability and security of their network, to satisfy
subscriber demands for new services, to retain existing
customers, and to attract new subscribers. JUNOS consistently
demonstrates its engineering discipline by providing on-time
delivery of new features and production-ready implementations
of new technologies _ such as MPLS to provide the “circuitlike” delivery of IP services across provider-defined explicit
routes. Traffic engineering and constraint-based routing have
allowed providers to use available bandwidth effectively
from end to end, while QoS has ensured that mission-critical
applications can access network resources during periods
of network congestion and other types of network stress.
JUNOS software has facilitated a variety of data services on the
forwarding plane. VPN services at Layers 2 and 3 have provided
both multipoint and point-to-point support for enterprises,
by separating private data from public data transmitted over

a common infrastructure. ATM and TDM interworking have
allowed providers to maintain their existing revenue streams
and support the transport of these services over a converged IP
infrastructure. Finally, Generalized MPLS (GMLPS) has provided
a common control plane between the optical transport and IP
data layers, resulting in faster and simpler provisioning, lower
overall cost of operations, and improved capacity utilization.
Juniper Networks played a leading role in developing the IETF
standards that define how these essential technologies should
be implemented and deployed in service-provider networks.
Today, the IP core is significantly more complex than it was
in 1998, and the technical challenges and economic risks are
even greater. JUNOS has benefited from the experience of
growing with the Internet, because failure is not an option in
the service-provider community. One false step can have a
huge economic impact, severely damaging a service provider’s
hard-earned reputation for delivering quality services.
The first router OS designed specifically for carrier environments,
JUNOS runs today on all Juniper Networks T-series, M-series,
and J-series routers, and is currently deployed in the largest
and fastest growing networks worldwide. Its full suite of robust
routing protocols, flexible routing policy language, and leading
MPLS implementations can scale efficiently to the largest
numbers of network interfaces and routes of any vendor.
Conclusion
The hallmarks of carrier-class platforms are reliability, scalability,
performance, and security. JUNOS was developed with these
requirements in mind, and has been proven in the world’s
largest IP networks. By running the modular JUNOS software
on protected system resources, Juniper Networks routers
combine reliability with the flexibility to enable the triple-play
applications of voice, video, and data, and to meet their rigorous
requirements for resiliency, advanced routing, QoS, scalability,
and high performance in the largest IP networks in the world.

Page 8

CORPORATE HEADQUARTERS
AND SALES HEADQUARTERS
FOR NORTH AND SOUTH AMERICA
Juniper Networks, Inc.
1194 North Mathilda Avenue
Sunnyvale, CA 94089 USA
Phone: 888-JUNIPER (888-586-4737)
or 408-745-2000
Fax: 408-745-2100

EAST COAST OFFICE
Juniper Networks, Inc.
10 Technology Park Drive
Westford, MA 01886-3146 USA
Phone: 978-589-5800
Fax: 978-589-0800

ASIA PACIFIC REGIONAL
SALES HEADQUARTERS

EUROPE, MIDDLE EAST, AFRICA
REGIONAL SALES HEADQUARTERS

Juniper Networks (Hong Kong) Ltd.
Suite 2507-11, Asia Pacific Finance Tower
Citibank Plaza, 3 Garden Road
Central, Hong Kong
Phone: 852-2332-3636
Fax: 852-2574-7803

Juniper Networks (UK) Limited
Juniper House
Guildford Road
Leatherhead
Surrey, KT22 9JH, U. K.
Phone: 44(0)-1372-385500
Fax: 44(0)-1372-385501

www.juniper.net
Copyright 2005, Juniper Networks, Inc. All rights reserved. Juniper Networks, the Juniper Networks logo, NetScreen, NetScreen Technologies, the NetScreen logo, NetScreen-Global Pro, ScreenOS, and GigaScreen are registered trademarks
of Juniper Networks, Inc. in the United States and other countries.
The following are trademarks of Juniper Networks, Inc.: ERX, ESP, E-series, Instant Virtual Extranet, Internet Processor, J2300, J4300, J6300, J-Protect, J-series, J-Web, JUNOS, JUNOScope, JUNOScript, JUNOSe, M5, M7i, M10, M10i, M20,
M40, M40e, M160, M320, M-series, MMD, NetScreen-5GT, NetScreen-5XP, NetScreen-5XT, NetScreen-25, NetScreen-50, NetScreen-204, NetScreen-208, NetScreen-500, NetScreen-5200, NetScreen-5400, NetScreen-IDP 10, NetScreen-IDP
100, NetScreen-IDP 500, NetScreen-Remote Security Client, NetScreen-Remote VPN Client, NetScreen-SA 1000 Series, NetScreen-SA 3000 Series, NetScreen-SA 5000 Series, NetScreen-SA Central Manager, NetScreen Secure Access,
NetScreen-SM 3000, NetScreen-Security Manager, NMC-RX, SDX, Stateful Signature, T320, T640, and T-series. All other trademarks, service marks, registered trademarks, or registered service marks are the property of their respective
owners. All specifications are subject to change without notice.
Juniper Networks assumes no responsibility for any inaccuracies in this document. Juniper Networks reserves the right to change, modify, transfer, or otherwise revise this publication without notice.

351081-001

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