ITU‐T's Technical Reports and Specifications 485 7.2.2 Networking Infrastructure The Local Area Network (LAN) is the mechanism by which access to network communication services and resources is enabled for end users and devices spread over a single floor or entire building. Since doing this in a \"flat\" manner is not efficient, a hierarchy or tiered model is often used. This allows the network to be broken up into groups or layers. Such a modular approach allows each layer to implement specific functions, thereby simplifying the network design, deployment and management of the network. Modularity enables the creation of elements that can be replicated throughout the network and therefore a simple way to scale the network for the entire building. Another advantage of such a modular and hierarchical approach is that if there are some fixes due to faults to be made to a given subset of the network, such changes are contained to that subset and the other parts of the network are not impacted. This improves network efficiency and resiliency. A common approach to LAN design includes the following three layers: Access layer—Provides endpoints and users direct access to the network; Distribution layer—Aggregates access layers and provides connectivity to services; Core layer—Provides connectivity between distribution layers for large LAN environments. Such a network would run throughout the building. 7.2.3 Access Switches At the bottom Access Layer, the Access Switches aggregate all the end user's traffic from Desktops, Laptops, Smartphones, IP Phones, and Videoconferencing terminals. Typically Access Switches can be placed on a per floor basis. One expects 1600 users, an average of 65/floor, and the switching bandwidth and port stacking needs to be sized accordingly. 7.2.4 Wireless Access Points As a result of increasing use of Laptops, Tablets, Smartphones, it is also imperative that Wi‐Fi access be provided. The average area of a floor is around 4000 sq. ft. This area and wall partitioning and users/floor should be considered while sizing the Access Point count and placement on every floor. The Wi‐Fi controllers can be placed in the Server Room. 7.2.5 Core Switches The Core Switch performs the function of interlinking the access switches and providing user connectivity to servers and also to the Internet (shown as WAN in the picture). The core switch placement must be optimized such that LAN/Ethernet cable runs from all the floors to the core switch do not cross the specifications. Where there is issue, fiber connectivity must be considered. 7.2.6 Firewalls They protect in following ways: Protect servers (e.g., email servers, web servers) from malicious externals attacks such as email spamming, website defacing etc. Protect network from malicious external Denial of Service attacks through incorrect or malformed IP packets. Protect users from malicious external attacks through incorrect or malformed HTTP data.