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BROCADE
ISL TRUNKING
STORAGE AREA
NETWORK
HIGHLIGHTS
•Combines up to eight Inter-Switch Links
(ISLs) into a single logical trunk that
provides up to 128 Gbps data transfers
(with 16 Gbps solutions)
•Optimizes link usage by evenly
distributing traffic across all ISLs at the
frame level
•Maintains in-order delivery to ensure
data reliability
•Helps ensure reliability and availability
even if a link in the trunk fails
•Optimizes fabric-wide performance and
load balancing with Dynamic Path
Selection (DPS)
•Simplifies management by reducing the
number of ISLs required
Higher Performance for
Demanding Applications
INCREASED PERFORMANCE WITH
ISL TRUNKING
Brocade® ISL Trunking is an optional
software product available for all Brocade
Fabric OS®-based Fibre Channel switches,
directors, and the Brocade DCX® Backbone
family. This technology is ideal for optimizing
performance and simplifying the management
of multiswitch Storage Area Network (SAN)
fabrics containing Brocade 4 and 8 Gbps
switches and directors and the latest
16 Gbps solutions. When two or more
adjacent Inter-Switch Links (ISLs) in a port
group are used to connect two switches
with trunking enabled, the switches
automatically group the ISLs into a single
logical ISL, or “trunk.” The throughput of
the resulting trunk can be anywhere from
8 Gbps to as much as 128 Gbps.
•Provides a high-performance solution for
network- and data-intensive applications
ISL Trunking is designed to significantly
reduce traffic congestion in storage
networks. As shown in Figure 1, up to eight
ISLs can be combined into a single logical
ISL with a total bandwidth of 128 Gbps that
can support any number of devices.
To balance workload across all of the ISLs in
the trunk, each incoming frame is sent across
the first available physical ISL in the trunk.
As a result, transient workload peaks are
much less likely to impact the performance
of other parts of the SAN fabric, and
bandwidth is not wasted by inefficient traffic
routing. ISL Trunking can also help simplify
fabric design, lower provisioning time, and
limit the need for additional ISLs or switches.
Optimal bandwidth
using up to eight
4 or 8 Gbps links
4 Gbps
4 Gbps
1.5 Gbps
4 Gbps
1.5 Gbps
4 Gbps
Without trunking
16 Gbps with eight trunks
5.5 Gbps
4.5 Gbps
With trunking
With trunking
Up to
8.5 Gbps
128 Gbps
6 Gbps
2 Gbps
10.5 Gbps
4.5 Gbps
9 Gbps
...n Gbps
congestion
The Brocade One™ strategy helps
simplify networking infrastructures
through innovative technologies
and solutions. Brocade ISL Trunking
supports this strategy by optimizing
application performance and
availability across the network,
and simplifying network design
and management.
5.5 Gbps
4 Gbps
1.5 Gbps
4.5 Gbps
Three individual
8.5 Gbps links
5.5 Gbps
68 Gbps
4 Gbps
1.5 Gbps
4.5 Gbps
Figure 1.
Optimal bandwidth using up to eight
4, 8, or 16 Gbps links.
ASIC preserves
in-order delivery
8.5 Gbps
6 Gbps
2 Gbps
10.5 Gbps
4.5 Gbps
Up to
128 Gbps
9 Gbps ...n Gbps
ASIC preserves
in-order delivery
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DYNAMIC PATH SELECTION FOR
OPTIMIZED PERFORMANCE
To further optimize network performance,
Brocade 4, 8, and 16 Gbps switches and
directors support optional Dynamic Path
Selection (DPS). Available as a standard
feature in Brocade Fabric OS, exchange-based
DPS optimizes fabric-wide performance by
automatically routing data to the most efficient
available path in the fabric (see Figure 2).
DPS augments ISL Trunking to provide more
effective load balancing. With DPS, traffic
loads are distributed at the exchange level
across independent ISLs or trunks, and
in-order delivery is guaranteed within the
exchange. The combination of trunking
and DPS provides immediate benefits to
network performance—even in the absence
of 16 Gbps devices—and DPS in particular
can provide performance advantages when
connecting to lower-speed 4 Gbps switches.
As a result, this combination of technologies
provides the greatest design flexibility and
the highest degree of load balancing.
TRUNKING OVER DISTANCE
To provide maximum flexibility, trunking is
also supported over long distance Fibre
Channel links. The actual distance supported
depends on the specific configuration,
Frame-based trunking
ASIC preserves in-order delivery
Up to
8.5 Gbps
128 Gbps
6 Gbps
2 Gbps
10.5 Gbps
4.5 Gbps
9 Gbps
...n Gbps
including number of links and link speeds
employed. But as long as the ports belong
to the same trunk group, they can be trunked
at any supported distance and speed. Refer
to the Brocade Fabric OS Administrator’s
Guide for additional information.
SIMPLIFIED MANAGEMENT
AND DESIGN
In almost any network, management costs
increase with complexity—rising with the
number of elements being managed. With
ISL Trunking, Brocade Fabric OS views the
group of physical ISLs as a single logical ISL,
a design that:
•Lowers the number of entities to manage
•Reduces the number of lines on a logical
topology map
•Improves traffic and capacity provisioning
to keep systems and applications running
at full speed
•Simplifies network design, capacity
planning, and fabric administration
ISL Trunking can be managed through
a small number of commands with the
Brocade Command Line Interface (CLI)
or through the graphical Brocade Web
Tools utility.
Dynamic Path Selection (DPS)
Balancing data flow between
multiple trunk groups
Trunk group
Trunk group
8.5 Gbps
6 Gbps
2 Gbps
10.5 Gbps
4.5 Gbps
Up to
128 Gbps
9 Gbps ...n Gbps
DPS
Trunk group
The failure of a link in a route causes the
network to reroute any traffic that was using
that particular link—as long as an alternate
path is available. Brocade Fabric Shortest
Path First (FSPF) is a highly efficient routing
algorithm that reroutes around failed links
in less than a second.
ISL Trunking improves on this concept by
helping to prevent the loss of the route. A link
failure merely reduces the available bandwidth
of the logical ISL trunk. In other words, a failure
does not completely “break the pipe,” but
simply makes the pipe thinner. As a result, data
traffic is much less likely to be affected by link
failures, and the bandwidth automatically
increases when the link is repaired.
AUTOMATIC CONFIGURATION
As with all Brocade optional software products,
the license for ISL Trunking can be factoryinstalled or added later. No software installation
is required. ISL Trunking is automatically
invoked when ISLs are added between any
two Brocade 4, 8, or 16 Gbps solutions.
BROCADE GLOBAL SERVICES
Brocade Global Services delivers world-class
professional services and technical support
to enable the transition to virtualized data
centers and cloud-optimized architectures.
Brocade Professional Services offers
assessment, design, and implementation
services to help organizations optimize their
SAN architectures in cloud-optimized data
centers. Brocade Premier Support and
onsite residencies help organizations
maximize availability of mission-critical data
in SAN environments through personalized,
preferential, and proactive technical support.
Trunk group
MAXIMIZING INVESTMENTS
Figure 2.
Dynamic Path Selection augments ISL Trunking to route
data efficiently between multiple trunk groups.
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© 2011 Brocade Communications Systems, Inc. All Rights Reserved. 05/11 GA-DS-134-08
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