CCNA2 capitulo 1.

Growing complexity of networks

The digital world is changing. The ability to access the Internet and corporate network is no longer limited to physical offices, geographic locations or time zones. In the current globalized work place, employees can access resources from anywhere in the world, and the information should be available at any time and on any device. These requirements are driving the need to build next-generation networks that are safe, reliable and highly available.

These next-generation networks must not only be consistent with the expectations and the current equipment, but should also be able to integrate old platforms.

Elements of a converged network

 To support collaboration, commercial networks use converged voice solutions through systems, IP phones, voice gateways, video support and video conferencing. Converged networks with collaborative support, including data service may include features such as:

Call Control: processing telephone calls, caller ID, call forwarding, call waiting and conference.

- Voicemail: Voicemail.

- Mobility: receiving important calls anywhere.

- Answering machine: it caters to customers more quickly, since calls are routed directly to the department or corresponding person.

One of the main benefits of the transition to a converged network is to be set up and manage a single physical network. This saves considerably in the installation and management of networks of voice, video and data independent. These converged network solutions integrated IT management for every move, addition and modification is complete with an intuitive administration. In addition, converged network solutions supported softphone applications for PC as well as point-to-point video, so that users can enjoy personal communications with the same ease of administration and use of a voice call.

The convergence of services on the network led to an evolution of networks, traditional data transport function to a major highway for communication of data, voice and video. This physical network must be properly designed and implemented to allow reliable operation of various types of information to be conveyed. To allow administration of this complex environment, a structured design is required.

Switched networks without borders

With the increasing demands of converged networks, the network must be developed with an architectural approach that integrates intelligence, simplify operations and is scalable to meet future demands. The Cisco Borderless Network Architecture, is an example of one of the latest developments in network design.

Cisco Borderless Network is a network architecture which combines several innovations and design considerations to allow organizations to connect with anyone, anywhere, anytime and on any device safely, confidently and smoothly. This architecture is designed to meet the business and IT challenges, such as the admission of converged networks and changing work patterns.

The Cisco Borderless Network Architecture is built on an infrastructure of scalable and resilient hardware and software. This architecture allows different elements, from access switches to wireless access points, work together and allow users to access resources at any time and place, providing optimization, scalability and security to collaboration and virtualization.

Hierarchy switched networks without borders

Creating a switched network without borders requires the use of solid design principles to ensure maximum network availability, flexibility, security and ease of administration. Borderless switched networks must operate according to current requirements and services and technologies that will be required in the future. The design guidelines borderless switched networks are based on the following principles:

- Hierarchical: facilitates understanding of the function of each device on each level, simplifies deployment, operation and administration, and reduces the error domains at each level.

- Modularity allows for expansion of the network and enabling seamless and integrated service request.

- Resistance: satisfies user expectations to maintain always-on network.

- Flexibility: share the traffic load intelligently using all network resources.

These are not independent principles. It is essential to understand how it fits every principle in the context of others. The hierarchical design of a switched network without borders provides a basis that allows network designers overlapping security features, mobility and unified communications. Models of three layers and two levels, as shown in the illustration, are double checked frames hierarchical design for campus networks.

The three fundamental layers within these designs levels are layers of access, distribution and core. Each layer can be considered a well-defined structured module with specific functions and roles in campus network. The introduction of modularity in the hierarchical campus design further ensures that the campus network maintains sufficient strength and flexibility to provide basic network services. The modularity also allows for growth and changes that occur over time.

Function switched networks

Function switched networks evolved significantly over the past two decades. Not long ago, flat Layer 2 switched networks were the norm. Data networks flat layer 2 of the basic properties depended Ethernet and widespread use of repeaters to propagate hub LAN traffic across an organization. As shown in Figure 1, networks are basically changed by LAN switched in hierarchical networks. Switched LANs provide more flexibility, traffic management and additional features, such as:

Quality of service

Additional security

Support networks and wireless technology connectivity

Compatibility with new technologies such as IP telephony and mobility services

Switching as a general concept in networking and telecommunications

 The concept of switching and frame forwarding is universal networking technology and telecommunications. In the LAN, WAN networks and public switched telephone network (PSTN), various types of switches are used. The fundamental concept of switching refers to a device that makes a decision on two criteria:

-        Port of entry

- Destination address

The decision on how a switch forwards traffic taken in connection with the traffic flow. The term "gateway" is used to describe the location of a port where a frame enters the device. The term "output" is used to describe the frames leaving the device from a particular port.

When a switch makes a decision, it does so on the basis of the input port and the destination address of the message.

LAN switches maintain a table used to determine how to forward traffic through the switch. Click the Play button on the illustration to see an animation of the process of switching. In this example:

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