provisioned separate networks for voice, video,
and data applications. In most cases, enterprises deployed
voice, video, and data networks autonomously and operated them
in isolation. Enterprises managed and implemented these
networks with separate teams. The separate networks encompass
the enterprise local and wide-area networks. In simple terms,
voice traffic used PBXs and data used routers. PBXs connected
to dedicated leased lines. Data used a combination of leased
lines, Frame Relay, and ATM. Figure depicts a typical
deployment of these disparate networks. Video relied on special
and very expensive leased line connections. This use of
disparate facilities for each application transport is
extremely inefficient. The volume of data traffic is growing
faster than the volume of voice traffic, driven by emerging and
evolving technological innovations such as the World Wide Web
(WWW), e-commerce, and applications such as videoconferencing
or video streaming using IP multicast. While growth rates vary
by country and carrier, it is certain that data transport will
soon dominate telephony networks. Data has already surpassed
voice on some U.S. service provider networks. Data is the
driving force behind global network growth. The challenge for
the enterprise is to optimize networking to carry data, voice,
and, most recently, video traffic. It is widely accepted and
acknowledged by the communications industry and industry
analysts as a whole that IP will become the universal transport
of the future. The rapid adoption and migration of vendors to
the use of IP as a transport for data, voice, and video
applications further endorses the transition to a converged
networking paradigm. The vendors changing to IP includes those
vendors who have historically used time-division multiplexing
(TDM) infrastructures and relied on old practices. Figure shows
an enterprise network converging over common IP transport.
Using IP as the form of transport offers the enterprise
significant statistical gains in bandwidth efficiency, lower
overall bandwidth requirements, ease of management, and the
ability to deploy new applications rapidly. There are fewer WAN
facilities and fewer devices required to terminate those
facilities. Enterprises add bandwidth incrementally as required
and statistically share bandwidth between applications, adding
efficiency and reducing complexity. Convergence provides an
economic inducement to companies as well. When companies
subscribe to disparate network models, they often pay for
services even though they are not being used. In a converged
environment, bandwidth is shared amongst voice, video, and data
applications. For example, when voice is inactive, data can use
the available bandwidth; when voice or video applications are
active, required bandwidth for these operations is guaranteed.
Content 1.2 Describing Converged Network
Requirements 1.2.1 Hierarchical Network Model
Despite current information technology (IT) investment,
many organizations find that vital networked resources,
applications, and information assets remain largely unlinked.
In fact, it is common for organizations to have hundreds of
applications and databases that cannot communicate with each
other. This is due in part to increasing and often unexpected
demands from internal and external customers. Many enterprises
have to deploy new technologies and applications quickly. This
often leads to the deployment of disparate systems. The result
of these new deployments is an inability to share information
efficiently across the organization. For example, sales,
customer service, or purchasing departments cannot access
customer records easily without creating different overlay
networks that join applications and information. Many
organizations have found that unplanned expansion has left them
with multiple systems and distributed resources that are
uncoordinated and underused. The disparate systems are also
difficult and costly to manage. The Cisco Intelligent
Information Network (IIN) helps IT organizations to solve these
problems and meet new challenges including service-oriented
architectures, web services, and virtualization using network
architectures. IIN articulates the evolving role of the network
in facilitating the hardware and software integration that
makes it possible for organizations to better align IT
resources with business priorities. By building intelligence
into an existing network infrastructure, IIN helps
organizations realize benefits such as reduced infrastructure
complexity and cost. The Cisco Service-Oriented Network
Architecture (SONA) provides a pathway to achieving the IIN
vision. To understand the situation, this lesson reviews the
traditional network design model that many of today’s
enterprises used to build their networks. The traditional model
uses a three-layer hierarchical model. Initially, the model
provided a modular framework that allowed flexibility and made
implementation and troubleshooting easy. The hierarchical model
divides networks or their modular blocks into the access,
distribution, and core layers. Each layer has specific
features: - Access layer: The access layer grants
user access to network devices. In a campus network, the access
layer most often uses switched LAN devices with ports that
provide connectivity to workstations and servers. The access
layer of the corporate network topology is the site where WAN
links associated with remote sites and teleworkers are
aggregated.
- Distribution layer: The
distribution layer aggregates the wiring closets by using
switches to segment workgroups and isolate network problems in
a campus environment. Similarly, the distribution layer
aggregates WAN connections at the edge of the campus and
provides policy-based connectivity.
- Core
layer: The core layer, or backbone design, switches packets
as fast as possible. Because the core layer is critical for
connectivity, this layer must provide a high level of
availability and adapt to changes very quickly.
Network designers can apply the hierarchical model to any
network type including LANs, WANs, wireless LANs (WLANs),
metropolitan-area networks (MANs), and virtual private networks
(VPNs) and to any modular block of the Cisco networking model.
Figure presents an enterprise network using the traditional
hierarchical model design.
Content 1.2
Describing Converged Network Requirements 1.2.2
Cisco Enterprise Architectures Cisco provides the
enterprise-wide systems architecture that helps companies to
protect, optimize, and grow the infrastructure that supports
business processes. The architecture provides for integration
of the entire network—campus, data center, WAN, branches, and
teleworkers—offering staff secure access to tools, processes,
and services . From an Information Technology staff point of
view, the Cisco Enterprise Architecture facilitates planning,
designing, implementing, operating, and troubleshooting (PDIOT)
networks by focusing on network elements and on the
relationships between those elements.The Cisco Enterprise
Architectures consist of five elements: - Cisco
Enterprise Campus Architecture: Cisco Enterprise
Campus Architecture combines a core infrastructure of
intelligent switching and routing with tightly integrated
productivity-enhancing technologies, including IP
communications, mobility, and advanced security. The campus
architecture provides many features:
- High availability
with a resilient multilayer design and redundant hardware and
software features.
- Automatic procedures for
reconfiguring network paths when failures occur.
- Multicast to provide optimized bandwidth consumption.
- Quality of service (QoS) that prevents oversubscription to
ensure the network does not drop or delay real-time traffic,
such as voice and video or critical data.
- Integrated
security to protect against and mitigate the impact of worms,
viruses, and other attacks on the network, even at the switch
port level. Cisco enterprise-wide architecture extends