Find out how virtual chassis technology is breaking boundaries and enabling the network to reach new capabilities.

1. Multiple Chassis:
Virtual is Now
a Reality
Service providers require scalable, highly
available network elements that lower operating
costs and increase revenue potential. Network
equipment vendors respond with equipment
that increases system capacity, density and port,
subscriber and session scale.
But there are practical limits to just how large
equipment can get—standardized rack sizes,
power, and cooling constraints all limit the
size of a single system. The solution to this
issue has always been to add more systems,
an approach that also reduces single points of
failure by allowing chassis’s to provide backup
for one another in the case of a catastrophic
failure. Unfortunately, this adds operational
complexity by increasing the number of routing
entries and chassis that must be managed; and
failure scenarios, existing sessions are disrupted
as subscribers are forced to reconnect and reauthenticate to a backup system or site.
Real challenges, virtual solutions
New apps, increased network usage, and
user density are straining the edges of service
provider and data center networks. Video
and voice applications (and the users of
these apps) are very demanding, expecting
telephone-call quality and dependability every
time, all the time.
With traditional edge network architectures
and equipment, meeting these customers
expectations can be expensive and at odds with
a service provider’s operating reality. Designing
for ‘always-available’ services at scale typically
requires layers of redundant equipment to
manage, and margins suffer when networks
costs increase at a faster pace than revenue
growth. This is not a sustainable trend.
Greater chassis density helps, but on it’s own
doesn’t address management and operations
challenges and density improvements typically
lag traffic and subscriber growth. Skimping on
resiliency reduces CapEx costs, but increases
downtime risks that result in lost customers,
penalties and reduced revenue.
What if you could extend the concept of chassis
beyond the sheet metal to a large virtual
system, creating a virtual chassis?
Virtually Efficient
Logically combining multiple physical chassis
into one virtual chassis increases port count
without changing the number of routing table
entries or manageable devices. In fact, managing
the chassis and resources as a single logical
element simplifies operations and reduces Opex.
Upstream capacity is shared across a broader
base, improving bandwidth efficiency. For
example, with traditional redundancy schemes,
if two chassis were previously configured with
redundant backhaul links, one set of links is
unused to prevent loops by the layer 2 spanning
tree protocol. Now, operating as a single virtual
chassis, spanning tree is not required and all
backhaul links can be used, increasing backhaul
bandwidth without additional cost, and with no
penalty to resiliency , and service providers can
take full advantage of their network capacity.
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2. Long distance relationships can work
In the event of a catastrophic failure that
affects an entire central office, such as a fire
or a physical cable cut, traditional redundancy
schemes usingchassis failover is insufficient.
Subscriber sessions will time out, and it can take
an unacceptably long amount of time to restore
sessions. Major service disruptions will occur to
voice and video users, negatively impacting their
online experience. However, two geographically
separate physical chassis’s, operating as a
single virtual entity, preserve business continuity.
Subscriber traffic quickly switches from the
primary to the backup, with no degradation
of experience and no calls to the operator’s
support line. Without this capability, subscriber
equipment would eventually time out with the
loss of connectivity, and then request a new
connection from the backup site. These steps
can could take several minutes, time that will be
noticed by voice and video users.
Virtual solutions, real software
With the Juniper ‘virtual chassis’ approach to
network and service resiliency, two chassis,
each with dual routing engines, communicate
and dynamically elect a master system that
acts as the central configuration and control
point. A virtual chassis control protocol
(VCCP), based on the robust intermediate
system routing protocol (IS-IS), maintains
configuration information across both chassis.
The result is a single, combined virtual chassis
that simplifies operations by appearing as one
device with more slots, flattening the network
configuration with one routing table. If the
chassis each have 11 slots, one has slots 1-11,
and the other slots 12-22.
To, enhance the performance of the virtual
chassis and the network Juniper’s MX Series
architecture offers a clean separation of the
forwarding plane and the control plane. Even
in the event of a failover, forwarding continues
non-stop, and packets appear to the rest of the
network as if they are still coming from the same
port and same IP address. No routing updates
or other control messages are triggered and
propagated on the network, and sessions are not
forced to wait for routes to converge.
Service providers achieve configuration and
ease of management, and continuous, realtime updates of the state of every service
and subscriber is also maintained. The virtual
chassis protocol ensures that all of the routing
engines have the info they need to assume
control of the virtual chassis group at any time,
without any service disruption. As long as the
latency of the VCCP link is less than 100 ms,
the two chassis do not have to be collocated,
allowing them to be installed up to 70 km apart.
Real software, real deployments
Business and residential customers are
a demanding group with ever-increasing
expectations of service levels and experience.
What was once a best-effort network is now
handling large quantities of voice and video
traffic, and service disruptions of even a few
seconds may trigger a service call. In fact,
many Internet phone packages are required by
regulatory authorities to provide emergency
services, and any disruption of those calls could
be life threatening. Of course, non-stop services
have always been a requirement for business
class services, frequently backed by servicelevel agreements.
Juniper’s innovative virtual chassis solution
appeals to both residential and business
markets. By aggregating subscriber traffic
through two geographically separate virtual
routers, resiliency improves from card and
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3. routing engine failures to protection from chassis
and even central office failures. Continuous
maintenance of state information ensures that
subscribers do not lose their connection, and
sub-second failover means no service disruption
at all. Video continues to play. Voice calls are
maintained. Service level agreements are upheld.
Fewer calls to the support center are made, and
lower operating costs are achieved. Customers
are happier, and the service provider’s brand
image remains intact.
Implementing a virtual chassis solution for
failure avoidance at scale provides benefits that
cannot be ignored. As broadand subscribers
and access bandidth continues to increase,
requiring more edge capacity and greater
platform density at network aggregation points.
Aggregate subscriber loads are moving from
tens of thousands to hundreds of thousands
of active connections per system and beyond.
Minor problems can cause major disruptions,
affecting large numbers of subscribers. Making
a single large virtual chassis system out of
smaller physical ones alleviates these risks.
Acting as a single entity, the two interconnected
chassis are configured, managed, and operated
as one, streamlining the edge architecture
and fully sharing network resources. Failures
in downstream equipment are handled with
little or no disruption to upstream devices and
routing tables. Hardware and software upgrades
are done in-service, without affecting end
users. Operational excellence is realized, and
operational costs are contained.
Traditional Redundancy
Schemes
Juniper Networks MX Series
Virtual Chassis Technology
Management View
Management View
Multiple Managed
Elements
Single Manageable
Resource
Single Control Plane
Independent Control Planes
Network Topology
Physically independent, co-located systems
Network Topology
Physically independent, geographically
separated systems
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4. Real deployments, Juniper Networks
Juniper Networks MX Series Universal Edge
Routers are field proven in virtual chassis
configurations, providing stateful protection at the
link, port, card, routing engine, and chassis level,
with no impact to subscriber sessions in case of
failure. Traffic is automatically balanced across
all links, without the added design, maintenance
and management complexity and increased costs
associated with load balancing appliances. The
MX Virtual Chassis makes simplified operations
and greater resiliency a reality.
To learn more about Juniper’s virtual chassis
solution and universal edge solutions, visit:
www.juniper.net/us/en/dm/edge/servicescalability/
About Juniper Networks
Juniper Networks is in the business of network
innovation. From devices to data centers, from
consumers to cloud providers, Juniper Networks
delivers the software, silicon and systems that
transform the experience and economics of
networking. The company serves customers and
partners worldwide. Additional information can
be found at www.juniper.net
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Fax: +1.408.745.2100
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Copyright 2013 Juniper Networks, Inc. All rights reserved. Juniper Networks, the Juniper Networks logo, Junos and QFabric are registered trademarks of
Juniper Networks, Inc. in the United States and other countries. All other trademarks, service marks, registered marks, or registered service marks are
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