Different Network Devices Explained in OSI Layers
When you first begin your journey in the networking world, you will be faced with many different device types. Here we discuss the fundamental networking devices to begin understanding where you stand.
What are Network Devices?
Network devices are physical hardware with software component that essentially allows the network devices to make decisions. In principle, network devices are the physical hardware that helps data move from source to destination. The network devices will support a particular OSI model layer, for example, switches operate on the Layer 2 of the OSI model layer. Routers, on the other hand, support the Layer 3 aspect of the OSI model layer. Regardless, network devices, depending on what it does, operates and functions to transmit data. We can use the OSI reference model to better understand where and how the devices function.
In this article, we will focus on a few important network devices.
5 Basic Network Devices:
- Wireless Access Point (AP)
What is a Hub?
A hub is a network device supporting Layer 1 (Physical Layer) communication.
Switches and ultimately routers were built on the idea of a hub. Hubs are devices that link several computer networking devices together. A hub also functions as a repeater, amplifying signals that deteriorate after traveling long distances over connecting cables. A hub is the most basic network networking system since it links LAN components that use the same protocols.
Hubs don’t do packet filtering or addressing — they simply send data packets to all connected devices. We can call this a ‘dumb’ device as the software component is very minimal. Hubs run at the Open Systems Interconnection (OSI) model’s Physical layer (Layer 1), as mentioned in the introduced.
A Switch is a network device supporting Layer 2 (Data Layer) communication.
Switches are a step up from a hub. A switch utilizes multiple ports and have more control over the source and destination of traffic. This allows for more agility and efficiency. Switches stores very minimal routing information (we’ll go over this more in detail later but a lot of switches allow for simple static routes, default gateways, etc) about internal network nodes and can connect to networks such as hubs or routers. Switches are commonly used to bind LAN networks.
- Switches can read the hardware addresses of incoming packets in order to route them to the correct destination.
- Switches outperform hubs and routers in terms of network performance.
- Switches enhances network security by making virtual segmentation (Vlans) more difficult to inspect with network monitors.
- Switches also allow for additional security such as Flood Guards. Flood Guards are used to prevent malicious traffic from bringing the switch to a halt as it is subjected to distributed denial of service (DDoS) attacks.
- Switches also have port security. Port Security is critical. Techniques such as DHCP snooping, ARP inspection, and MAC address filtering address Physical Port Security.
- Though we mention a Switch is in the Data Layer (Layer 2) of the OSI Reference Model, it can function at the Layer 3 (Network Layer) as well. We call this a multilayer switch, we’ll go over this as we progress in this course.
A Router is a network device supporting Layer 3 (Network Layer) communication.
Going beyond a hub and switch, the next network device on top of these two are Routers. Routers are multi-purpose devices that link two or more networks. Routers aid in the transmission of packets by creating a route across a network of interconnected networking devices using various network topologies. We call these techniques, routing protocols.
Routers are intelligent devices that store information about the networks to which they are linked. Most routers can be set up to act as packet-filtering firewalls with access control lists (ACLs). Routers are often used to convert from LAN framing to WAN framing in combination with a channel service unit/data service unit (CSU/DSU). Since LANs and WANs use different network protocols, this is needed. Border routers are the name given to such routers. They function as the outside link between a LAN and a WAN, and they run at the network’s perimeter.
Each router interface has its own Address Resolution Protocol (ARP) module, network card address, and Internet Protocol (IP) address. Routers, using a routing table and routing protocols, know which routes a packet might take from its origin to its destination. Like the bridge and switch, the routing table grows dynamically. When a packet arrives, the router removes the packet headers and trailers before analyzing the IP header to determine the source and destination addresses, data type, and arrival time. It also adds additional addresses to the router table that aren’t already there. The routing table is updated with the IP header and arrival time information.
- Routing Information Protocol (RIP)
- Interior Gateway Protocol (IGRP)
- Open Shortest Path First (OSPF)
- Exterior Gateway Protocol (EGP)
- Enhanced Interior Gateway Routing Protocol (EIGRP)
- Border Gateway Protocol (BGP)
- Intermediate System-to-Intermediate System (IS-IS)
We go over routing protocols in details later on in this course.