Converged networks, known also as triple-play services networks, are networks that have the ability to transmit data, voice, and video, or any combination of these services over the same networks. Converged networks are considered modern networks compared to traditional networks, where only dedicated services were provided on the networks. That has been the reason why we have existing networks such as telephone networks for transmitting voice, broadcast networks for transmitting video, and computer networks for transmitting data.

To understand the growing complexity of networks, let's compare the classic phone devices of many decades ago with today's smartphones. Obviously, the great potential that the smartphones offer compared to the classic phones makes this comparison sound naive; however, it is worth mentioning the fact that while the classic phones have used a dedicated voice communication network that understandably must have been less complex, by contrast the smartphones use a more complex communication network. That is because today’s communications networks, from frontend devices to backend devices, are various vendor technologies, resulting in more complexity when it comes to network scaling, upgrading, or patching.

As explained earlier, the converged network integrates data, voice, and video into a single network. This is achieved thanks to the technologically advanced equipment and the TCP/IP protocol. Thus, it can be said that the elements of converged networks are a convergent device and a converged service. An example of a convergent device is the multiplexer (as in Figure 1.26) that, at its input, merges multiple communication signals into a single signal at its output. For the converged service, it can be said that it is a service that provides voice, data, and video signals in a single network, thus providing services for all modes of communication:

Cisco's three-layered architecture helps defining the enterprise networks by simplifying the process of designing a reliable, highly-redundant, and scalable hierarchical inter-network. The three layers of Cisco architecture are as follows:

• Access layer, as the name indicates, is the layer in which network services are accessed. This layer mainly consists of computers, servers, hubs, layer 2 switches, access points, and other network end devices. A LAN network can be considered as an access layer analogy.
• Distribution layer is the middle layer that plays the role of the bridge by interconnecting the access layer and the core layer. This layer mainly uses layer 3 switches and routers. Extended LANs that form the MAN can be considered as a distribution layer analogy.
• Core layer is a fast and highly redundant network that is managed by core switches and routers. It is a backbone of the corporate network that enables the packet's movement between distribution-layer devices in different segments of the network. A WAN network can be considered as a core layer analogy.