What is Hierarchical Network Design? - Visualpath

1. What is Hierarchical Network Design? - Visualpath A network must align with the existing requirements of an organization, but it must also be flexible enough to easily integrate new technologies, which is where hierarchical network design comes in. What is hierarchical network design First proposed by Cisco in 2002, hierarchical network design has become an industry-wide best practice for developing reliable, scalable, and cost-effective networks. Initially, networks had a flat design and could only be expanded in one direction through hubs and switches, making it challenging to filter out undesirable traffic and control broadcasts. As a network grew in size, response times would degrade. A new network design was necessary, resulting in the hierarchical approach. A hierarchical design separates a network into distinct layers, where each layer has a series of functions that define its role in the network. Because of this, a network designer can choose the optimal hardware, software, and features to take on a particular role for that network layer. Data management is also far more efficient. In a hierarchical design, local traffic stays local and only moves to a higher layer when it is headed for another network. What are the typical layers in hierarchical network design? The layers in a hierarchical network design are usually mapped according to the network’s physical layout. They can differ, however, so it’s best to consider them as logical layers. A three-layer design is most common, but not mandatory. A three-layer hierarchical networks typically consist of: A core layer. This is the backbone of your network. It offers fast transport between distribution switches in the network. A distribution layer. This middle layer offers policy-based connectivity and regulates the boundary between the other two layers. It’s where routing and data filtering take place, and is sometimes referred to as the “Workgroup” layer. A access layer. Where endpoints and local servers access the network, and is often referred to as the “Workstation” layer. The basic outbound data flow starts from the endpoint into the access layer of the network. Data leaving the access layer is then fed into the distribution layer. If the destination is outside the local network, it’s routed into the core layer and, finally, to the destination, be it on the LAN, WAN, or to the outside world. The return trip is the same: the powerful, high-speed backbone of the core layer transports the data to the distribution layer, where it is intelligently routed to local access layers before hitting the endpoint. Let’s take a closer look at each layer’s functions as they relate to hierarchical network design. Core layer The core layer is essential as it connects multiple network components and is made up of your highest- speed, most powerful network devices. However, since it only has one purpose, it doesn’t require too many features (just be fast!).

2. The core must be reliable and efficient to maximize performance, and also available at all times. It should be designed with redundancies so it doesn’t have a single point of failure. If a catastrophic problem should occur, recovery needs to be quick. High-speed switching is essential, as well as fault tolerance. The core layer should be scaled through quality (better equipment) rather than quantity (number of devices). CPU-intensive packet manipulation, such as restrictive ACLs and QoS classifications, should be avoided at this level. Essentially, the core layer should be as lean as possible to minimize the potential for failure and maximize efficiency. Distribution layer Distribution layers aggregate the traffic from access layers and, well, distribute it into the rest of the network. This layer will usually have multiple switches and routers (or layer 3 switches performing routing functions), with each switch connected to multiple devices in the access layer. The distribution layer itself acts as a border, creating self-contained networks within the more extensive network. These distribution blocks can then route traffic to each other through the core layer. The advantage of separate blocks is that a problem in one block won’t affect the rest of the network. Distribution blocks are where network policies should be applied and act as an additional layer of security between access layers and the whole network. Access layer The access layer can be considered the entry point into the network (or the exit, depending on the direction of data flow!). It’s where end-user devices connect, feeding into access layer switches. Due to the number of end-user devices connecting to the network, there tends to be more switches on the access layer than any other in a typical hierarchical network design. They require high port density to support the large number of connecting devices, but generally don’t need a high throughput on them, as each port is connecting to just one specific device. These devices can be anything that requires a network connection, including laptops, smartphones, tablets, and printers. As it must support so many devices, the access layer tends to have the most features. It’s also where admins tend to spend a lot of their time. And with so many users and ad hoc devices, this layer also requires intensive security, as it’s the first border between the external world and the network. Some services you can typically find in the access layer include: Discovery and configuration: CDP, LLDP Security and network identity: 802.1x, DHCP, port security Application recognition: QoS marking, policing, queuing Network control: routing protocols, spanning-tree, DTP Physical infrastructure: PoE The access layer feeds into the distribution layer via OSI Layer 2 trunk ports, or Layer 3 routed ports. End-user devices connect to switches in the access layer at Layer 2.

3. Why is hierarchical network design so important? Hierarchical networks offer a wide range of benefits, such as enhanced performance, reliability and scalability, better security, easier management and design, and improved cost-efficiency. Let’s focus a bit on each one below. Enhanced performance A hierarchical network design means data is routed through aggregated switchport links at close to wire rate, instead of being sent through lower performance intermediary switches. The distribution and core layers consist of high-performance switches, which means higher speeds and fewer issues with network bandwidth. Therefore, if the network is designed correctly, data should travel at close to wire-speed between every device on the network for most of its journey within the network. Improved reliability The modular nature of a hierarchical network translates into a more reliable network as a whole, as segments that fail or become degraded can be isolated and routed around. The rest of the network won’t be affected. Availability also increases because it is easier to implement network redundancies. For example, switches in the access layer can be connected to two switches in the distribution layer. If one fails, the other comes into play. Likewise, the distribution switches connect to multiple core switches, providing yet another layer of redundancy. The only redundancy limitation is at the access level, since most end-user devices cannot link to multiple switches simultaneously. However, even if an access switch were to fail, only the devices using that switch would experience an outage and not the entire network. For more information Click Here Contact us: 9989971070