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Link Load Balancing |
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An increasing number of enterprises are using Internet medium for
delivering mission-critical content and applications. Maintaining a
single link to the public network exposes a single point of failure
& is considered as serious network vulnerability. In the event of a
link outage, all investments made towards redundant systems are
rendered useless. The organization and its customers are left with
significant downtime and financial losses.
Some organizations consider multi-site deployments to address their
availability concerns. However, this option is too expensive for small
to mid-sized enterprises. Multi-site deployments have many technical
complexities and also require considerable investments.
Traditionally, enterprises chose to address their network reliability
issues by installing a multiple public network connections to a site.
This approach is called multi-homing.
Some alternatives to multi-homing networks include:
- Multi-home with two links and one ISP link - Multi-homing
with two links from the same ISP. This is a cheaper solution to deploy,
but not very efficient because an outage at the ISP creates a
bottleneck as both links become unavailable.
- Multi-home with two links and two ISP links - Multihoming with two links from two separate ISPs can be implemented
using BGP protocol to route between them. Although BGP can provide link
availability it is a complex routing protocol that is not best suited
to provide multihoming and link routing. BGP is expensive and complex
to deploy because it needs special Autonomous System Numbers (ASN) from
the ISPs and router upgrades to be installed. In the case of a failure,
ISP cooperation is needed many times for link recovery. Secondly, BGP
propagation is extremely slow for different routes to converge. This
causes long and unpredictable failover times and does not meet the high
availability requirements for a business.
SNA recommends a cost effective solution called Link
load balancer. This provides high availability for applications with
multiple Internet links. The Link Load balancer seamlessly monitors
availability and performance of multiple WAN ISP connections to
intelligently manage bi-directional traffic flows to an application,
providing fault tolerant and optimized Internet access. |
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