You could think of IMA as the unknown factor that adds cost effectiveness
into the ATM WAN equation. And because the result equals ATM benefits for all WAN
users, not just those with very high traffic loads, it’s worthwhile to quickly review
ATM’s WAN benefits.
Highly scalable bandwidth. ATM’s biggest claim to fame is its speed—from £ 1.544
Mbps to gigabit ranges, with 1.2 Gbps (SONET OC-12) as the maximum customer
premise bandwidth available. The benefit: incremental costs for incremental bandwidth,
resulting in increased efficiency on hightraffic WAN links and an opportunity to
“right-size” bandwidth needs even to very high user demand.
Network simplification through consolidation. ATM is the answer for combining
applications that traditionally required different networks because of the different
transport requirements of their traffic. This in turn lets network planners stop the
proliferation of complex parallel networks: for example; one carrying data, another
carrying voice, and another carrying video. ATM’s ability to consolidate all types
of traffic onto a single WAN link greatly reduces complexity, and simplifies network
management by eliminating these separately managed lines.
Bandwidth efficiency. Consolidation of diverse traffic types also lets network
managers with high volumes of traffic fully utilize high-speed WAN links, instead of
partially filling separate links with different types of traffic.
Quality of service. ATM offers bandwidth allocation based on user-defined needs and
prioritization, as well as load sharing of multiple technology types for guaranteed
quality of service (QoS). ATM’s traffic management controls enable seamless integration
of voice, video, and data while providing the separate management techniques
required by each type of traffic.
Open connectivity. Because ATM is not based on a specific type of physical
transport, it is compatible with all currently deployed physical networks. It can be
transported over twisted pair, coax, and fiber optics. And since ATM is a standard rather
than a proprietary protocol, it can run on any vendor’s standards-compliant products or be
purchased from any carrier.
Excellent fault tolerance. ATM networks can be built with very high levels of fault
tolerance at relatively low cost. IMA, for example, allows for load sharing and maximum
ATM infrastructure availability. Service providers have invested heavily in the ATM
infrastructure for reasons similar to those of enterprises: consolidation of traffic/backbones,
better bandwidth utilization, and so on. ATM can also be deployed as a private
network built from leased lines such as T1/E1, T3/E3, or OC-3/STM-1.
Taken in sum, ATM’s capabilities— scalable bandwidth, network simplification,
bandwidth efficiency, guaranteed QoS, open connectivity, fault tolerance, and infrastructure
availability—make it invaluable for corporate WANs. ATM is also a stable WAN technology
with an extensive public infrastructure. Up until now, the primary barrier to securing
ATM benefits in the WAN has been the limited availability of carrier service.