ALLIED Telesis Resilient Networking with EPSR User Manual

Solutions Guide

Resilient Networking with EPSR

Introduction

IP over Ethernet is now a well-proven technology in the
delivery of converged services. Ethernet-based Triple-Play
services have become an established commercial reality
world-wide, with service providers offering advanced
voice, video and data packages to their customers. This
requires a highly available network infrastructure for
service providers to meet service level agreements,
and meet the expectations of customers for a seamless
multimedia experience.

Now, the convergence of services and applications in the
enterprise has led to increasing demand for high availability
in the Local Area Network (LAN). High bandwidth is also
required for the multiple applications simultaneously using
the network. For many businesses, real-time applications
like surveillance, automated control, video streaming and
voice over IP (VoIP) are used right alongside data and
Internet access.

The key to providing maximum network uptime is
extremely rapid failover in the event of link failure.

Allied Telesis’s carrier-grade resiliency feature, Ethernet
Protection Switching Ring (EPSR), ensures mission critical
services are not interrupted in the event of link or node
outages. EPSR provides failover times as low as 50ms, and
can be coupled with today’s maximum Ethernet standard
of 10Gbps, to provide high bandwidth in multiples of
10GbE.

Equally at home in the enterprise network, or demanding
service provider metro networks, EPSR provides a
solution that meets the modern network requirements of
high bandwidth and high availability. This advanced self­healing network technology provides ‘always-on’ access to
online resources and applications.

Allied Telesis supports this technology on a wide range
of sophisticated switching platforms, as well as advanced
telecommunication chassis.

Ethernet Protection Switching Ring

EPSR is Allied Telesis’ premier solution for providing
extremely fast failover between nodes in a resilient ring. EPSR
enables rings to recover within as little as 50ms, preventing
a node or link failure from affecting customer experience,
even with demanding applications such as IP telephony and
streaming video.

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The Technology

Putting a ring of Ethernet switches and/or iMAP (integrated
Media Access Platform) chassis at the core of a network is a
simple way to increase the network’s resilience - such a network
is no longer susceptible to a single point of failure. However, the
ring must be protected from layer-2 trafc loops. Traditionally,
Spanning Tree (STP)-based technologies were used to protect
rings, but they are relatively slow to recover from link failure.
This can create problems for applications that have strict loss
requirements, such as voice and video trafc, where the speed
of recovery is highly signicant.

EPSR enables rings to recover rapidly from link or node
failures within as little as 50ms, depending on por t type and
conguration. This is much faster than STP at up to 30 seconds,
or even Rapid STP (RSTP) at 1 to 3 seconds. EPSR, much
like STP, provides a polling mechanism to detect ring-based
faults and failover accordingly. But unlike STP, EPSR uses a fault
detection scheme to alert the ring that a break has occurred.
The ring then takes immediate action, instead of going through
an STP-like reconvergence.

Extremely low-latency signalling between the switches in the
ring enables very rapid detection of lost connectivity. The simple

topology enables immediate remedial action by the master
switch, with no requirement to spend any time exchanging
further signalling to conrm the network status. This almost­instant decision making makes EPSR a powerful solution, with
failover under fault conditions unnoticed by network and
application users.

Allied Telesis EPSR solution is extremely robust; its patented
technology providing the ability to handle unlikely complex fault
situations, like multiple failures.

The key proof of technology is customer experience. The
strong uptake of EPSR in demanding applications is testament it
has provided a superior solution to service providers and their
end users.

Diagram 1 shows a ring of switches that could be employed
as a network core or distribution solution for an enterprise
business, or service provider network. EPSR maintains ‘always­on’ network availability by monitoring the health of the ring, and
utilizing a reverse path for trafc almost instantaneously in the
event of a link or node failure.

Transit

Node

Master

Transit

Node

10Gbps Ethernet

Transit

Node

Diagram 1: EPSR in a ring of switches

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In some scenarios it is useful to implement an EPSR multi-ring
topology. For example, a service provider may have an access
ring connecting customers, and a distribution ring connecting
to services. A multi-ring topology is an excellent way to provide
a broadly distributed network that is still high performing,
and may require different bandwidth in different parts of the
network.

The multiple EPSR rings are likely to share a set of protected
VLANs. If these rings share a common segment, as shown in
diagram 2 below, there is the possibility of an undesirable loop

Master

forming out of both EPSR rings if the common segment was to
fail – this is known as a SuperLoop. The resultant SuperLoop
would leave a network storm state, with trafc circling the
SuperLoop indenitely causing performance issues and outages.

To prevent any possibility of a super-loop being formed, Allied
Telesis EPSR solution provides Super Loop Prevention (SLP).
EPSR-SLP ensures that multi-ring topologies are managed, and in
the event of any common segment failure no network loop can
be formed. The network gracefully handles any fault condition,
and ensures access to online services is always maintained.

Transit

Node

Common Segment

Transit

Node

Master

Both EPSR instances carry the same Data VLANs, therefore the

shared link is called a Common Segment, and this is a SuperLoop

topology which requires SuperLoop Prevention.

Diagram 2: Multi-ring topology using EPSR-SLP

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EPSR in the Enterprise

EPSR in enterprise network solutions
makes the benets of this technology
available for corporate, education,
hospitality and other customers
requiring maximum network uptime.
The following enterprise networks
showcase the many benets of EPSR.

Corporate EPSR network

As the corporate world comes to
rely more than ever on Information
Technology resources and applications,
a high availability infrastructure is vital.
An EPSR ring at the core of the network
provides the following key advantages:

■ High bandwidth: An EPSR ring

can run at up to 10Gbps, utilizing
today’s fastest Ethernet standard for
maximum data throughput.

■ Application versatility: High

bandwidth and ultra-fast failover
lend themselves to multiple
applications simultaneously using
the network. Real-time applications
like surveillance, video streaming
and voice over IP can be used right
alongside data and Internet access.

■ Easier troubleshooting: Unlike STP,

EPSR fails over with minimal changes
to network topology. The simplicity
of the ring structure, combined with
useful log messages, makes it easy to
determine the point of failure.

Diagram 3 shows a corporate network
based on a central EPSR ring. The
inclusion of Allied Telesis Vir tual Chassis
Stacking (VCStack) technology at the
core of the network adds a further
layer of resiliency. A single virtual
chassis comprised of two physical
units increases the availability of critical
resources.

■ Immediate access: Seamless

connectivity via voice, video or email
is maintained, and network servers
are accessible with no delay.

■ High availability: With no single point

of failure, continuous access to critical
business data and network resources
is maintained.

x610

x610

SBx908

PoE

PoE

servers

10 Gigabit link
1 Gigabit link
10/100 link
Link Aggregation

Diagram 3: Corporate EPSR network

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Campus EPSR network

Some characteristic requirements in a campus network are:

■ Ability to roam (at least within cer tain zones of the campus)

■ Security against network attacks and virus outbreaks

■ A design for scalable growth

■ Support for converged services

■ Flexibility to allow different sets of users to operate in the

way that best suits their needs

A design that supports these requirements is shown in
diagram 4. In this design, the Campus is partitioned into a set
of layer-2 switching domains, each of which is centred on its
own EPSR ring. To travel from one ring into another, trafc is
layer-3 switched. For example, Art department trafc is layer-3
switched when moving to Science or Administration.

The key advantages of this design are:

■ High availability: Dual points of connection between

neighbouring domains provides resiliency in the inter­domain connectivity.

■ Easier maintenance: Clear demarcation between zones

simplies troubleshooting, and facilitates staged network
upgrades.

■ Fast failover: Use of EPSR throughout the network ensures

ultra fast recovery from link failures, as demanded by
converged services.

■ High bandwidth: The core servers can be provisioned with

a dedicated ring of extremely high bandwidth with high
resiliency.

■ Roaming: Users can easily roam within the zone covered by

any one of the layer-2 domains.

■ Efcient use of bandwidth: The layer-3 switching between

domains will reduce the proliferation of broadcast trafc
through the network.

■ Security: Strict rules can be established for which trafc may

pass between domains, and these rules can be enforced by
the layer-3 switches.

SBx908

x900

Servers

x900

x900

x610

x900

Administration Department

8100S

x600

Servers

x600

Art Department

8100S

Science Department

10 Gigabit link
1 Gigabit link
10/100 link
Link Aggregation

Diagram 4: Campus EPSR network

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EPSR in Metro networks

Service Provider Metro networks require extremely high
reliability, as these city-wide networks provide online access
to many businesses, and multi-media Triple-Play services (data,
voice and video) to many homes. With ser vice level agreements
to meet, any outage is both costly to the service provider, and
disruptive for customers.

EPSR is an ideal solution for the delivery of converged services
in the Metro environment with the following key advantages:

■ Long Distance: Geographically spread out nodes are

supported as bre allows long distance connectivity.

■ High availability: With no discernible outage in the event of

a link or node failure, EPSR provides the perfect solution for
service providers meeting service level agreements.

■ High performance: Connectivity to voice, video and data

services is always maintained for a seamless customer
experience.

■ Multi-speed support: The distribution and access rings

can run at different speeds appropriate to the amount of
network trafc.

■ Network protection: The use of EPSR SuperLoop

Prevention (SLP) ensures there is no chance of a loop
forming, and subsequent network storm in this multi-ring
environment.

A multi-ring EPSR-SLP protected design is shown in diagram 5.
This city-wide Metro network provides high performing online
access for businesses, and advanced Triple-Play services to
residential customers.

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Internet

PSTN

Business

VoIP

Media

Gateway

x900

x900

SBx3112

Management

SBx908

10 Gbps Metro

distribution ring

Application

Services

IP TV

Services

x900

x900

SBx3112

Business

2 Gbps Metro

access ring

10 Gigabit link
1 Gigabit link
10/100 link
Link Aggregation

Diagram 5: Service Provider Metro network using EPSR-SLP

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The ‘always-on’ network

The proven benets of EPSR have been widely deployed in
both enterprise and service provider networks. Advanced
solutions provide high bandwidth and maximum uptime.

Business owners can be sure that their network infrastructure
is always available for the many online activities that are part of
the modern work place. Service providers can condently meet
the demanding requirements of a converged environment, and
provide a superior customer experience.

EPSRs advanced self-healing technology provides ‘always-on’
access to online resources and applications.

EPSR Products

The following products all support EPSR .

SwitchBlade x908

ADVANCED LAYER 3 MODULAR SWITCHES

The Allied Telesis SwitchBlade™ x908 advanced Layer 3
modular switch offers high exibility and port density in a small
physical size, providing scalable and versatile switching solutions
for today’s Enterprise networks. Each chassis supports eight
high-speed 60Gbps expansion bays, and can also be paired in a
VCStack.

x900 12 & 24

ADVANCED LAYER 3 SWITCHES

The Allied Telesis x900 series is one of our most advanced
series of switches and is unmatched in performance, exibility
and reliability. This series provides ne service provisioning
granularity, high availability, and advanced QoS. All x900
switches incorporate a switching core that yields wire speed
IPv4 and IPv6 routing and most switches feature robust
hardware with dual hot swappable power supplies. The x900
series switches share the same expansion modules (XEMs) as
the SwitchBlade x908.

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EPSR Products

x610 Series

ADVANCED LAYER 3 GIGABIT ETHERNET
STACKABLE SWITCHES

x600 Series

The Allied Telesis x610 series is the high performing and scalable
solution for today’s networks, providing an extensive range of
port-density and uplink-connectivity options. 24-port and 48­port versions are available with optional 10 Gigabit uplinks and
PoE+ ports. The ability to stack up to eight units includes using
ber for long distance stacking. The x610 Series can connect
anything from a small workgroup right up to a large business.

ADVANCED LAYER 3 GIGABIT STACKABLE
EDGE SWITCHES

The Allied Telesis x600 series is an advanced series of stackable
switches providing high performance, exibility and reliability.
The x600 series provides high levels of Network Access
Control (NAC) security making them ideal for the entry point
into a corporate network. High speed 10Gbps uplinks and
high speed stacking of up to four switches ensures excellent
performance, while optional redundant power supplies can
ensure network availability.

SwitchBlade x3112

ACCESS EDGE CHASSSIS SWITCH

The Allied Telesis SwitchBlade x3112 is a 12 Slot access edge
chassis switch primarily targeted for service provider ber
access networks, and equally at home at the enterprise
network edge and the data center. The switch was designed to
deliver high availability, maximum per formance with wire speed
non-blocking backplane performance, and high por t count.

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iMAP 9000 series

INTEGRATED MULTISERVICE ACCESS
PLATFO R M (IMAP™)

The Allied Telesis iMAP is the only carrier-grade, IP/Ethernet
networking solution in the industry that effectively supports
IP Triple Play services simultaneously over copper and ber
infrastructure. Deploy high-bandwidth IP Video, POTS, VoIP
and data services over copper or ber using a variety of access
technologies. Allied Telesis iMAPs are available in different sizes
and densities and offer many plug-and-play access capabilities.

About Allied Telesis Inc.

Allied Telesis is a world class leader in delivering IP/Ethernet network solutions to the
global market place. We create innovative, standards-based IP networks that seamlessly
connect you with voice, video and data services.

Enterprise customers can build complete end-to-end networking solutions through
a single vendor, with core to edge technologies ranging from powerful 10 Gigabit
Layer 3 switches right through to media converters.

Allied Telesis also offer a wide range of access, aggregation and backbone solutions
for Service Providers. Our products range from industry leading media gateways
which allow voice, video and data services to be delivered to the home and
business, right through to high-end chassis-based platforms providing significant
network infrastructure.

Allied Telesis’ flexible service and support programs are tailored to meet a wide
range of needs, and are designed to protect your Allied Telesis investment well into
the future.

For further information visit us online at alliedtelesis.com

Americas Headquarters | 19800 Nor th Creek Parkway | Suite 100 | Bothell | WA 98011 | USA | T: [phone] | F: [phone]
Asia-Pacic Headquarters | 11 Tai Seng Link | Singapore | 534182 | T: [phone] | F: [phone]
EMEA Headquarters | Via Motta 24 | 6830 Chiasso | Switzerland | T: +41 91 69769.00 | F: +41 91 69769.11

alliedtelesis.com

© 2012 Allied Teles is Inc. All rig hts reser ved. Inform ation in this d ocument is sub ject to change w ithout not ice. All compa ny names, logos , and produc t designs tha t are trade marks or re gistered t rademar ks are the pro perty of t heir respec tive owner s.

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