Networking Hardware and Components By: Sean Bell
Hubs An Ethernet hub is a networking device that allows multiple devices to connect and communicate with each other via Ethernet. All ports on a hub support both input and output, and works by forwarding any signal received from the input of one port to the output of all other ports. For example, if 3 computers are connected to the hub pictured to the right in ports 1, 2, and 3, and the computer at port 1 sends a packet out to the hub, the computers on ports 2 and 3 would both receive the packet from the computer on port 1. Hubs work only on the physical layer of the OSI model, simply passing data through regardless of content. Ethernet hubs are generally considered obsolete in modern networking. Since a hub simply repeats any input to all other outputs, collision is a major problem that is better addressed by network switches (explained later). Early on, switches were much more expensive than hubs, for a seemingly small benefit in comparison. However, as switches have continued to decrease in price, they have also all but replaced hubs for managing multiple Ethernet connections. If you can find a non-switching hub, it will likely run less than $10.
Switch A networking switch is seen by some as a “Smart Hub”. It is used, like a hub, to connect multiple devices and allow intercommunication via Ethernet connection. Unlike a hub, however, a switch processes packets at the data link layer (layer 2), allowing it to send a packet only to its intended destination, preventing the sort of data collision that plagued simple hubs. These days, a switch can be used anywhere a single Ethernet connection needs to be used to communicate with more than one device. It can be used for an isolated network, allowing communication only between connected local machines (such as a LAN party, or local networked video gaming party), or it can connect multiple machines to a single outgoing Internet-connected data port. For Internet connection, other network hardware is needed (described later), though nothing else is needed for an isolated connection. However, it should be noted that presently, many of the listed items in this presentation are often sold as hybrid devices which combine functionality of multiple pieces of hardware necessary for Internet connection. Simple switches can range from around $8 to well in the thousands for high-end rack-mount switches, but average in the $30 range.
Router Routers are devices designed to direct packets sent from computers and other connected devices by calculating the fastest route for the packet to reach its destination. Unlike a switch, a router utilizes Level 3 information in packets to figure out the most efficient path for the packet to take, even outside the immediate network. When a router receives an outgoing packet, it consults its routing tables, which contain possible node options between the router and the intended destination, as well as its preset routing rules, and calculates the shortest path for the packet to reach its destination. The packet is then sent to the next node as determined by the router’s calculations. A packet will likely pass through several routers from start to finish, as each node dynamically forwards incoming packets within the ISP internetworks, forming the backbone of the Internet. Note that a home or business router often contains a switch, gateway, firewall, and wireless access point internally, allowing all these necessary functions to be performed by a single device. A router can range between $20 to several hundred for more cutting-edge home routers, but a good one will average about $100 or so. Router Node A Node B Node C Node B Selected!
Bridge An increasingly rarer piece of hardware, a bridge simply connects two separate network segments to act as a single network. All it does is forward any packets received from one port through to the other port. Both networks must be of the same type, as the bridge deals only with Layers 1 and 2. A bridge may be used in instances where a network is divided geographically into various parts. Simply put, a bridge is essentially like a switch, but with only two ports for connections. However, a bridge (typically) routes data using only MAC addresses, and, thanks to there only being one possible outward port for each incoming packet, a bridge does not need to manage which port to send packets to internally like a switch does. As mentioned, a dedicated Ethernet bridge is somewhat difficult to find, but as many devices combine bridging capability with other networking capabilities, hybrid devices may be your only option. But if you manage to find a dedicated Ethernet bridge, it will likely run cheap (<$10) as, on its own, it is generally regarded as an obsolete technology.
Gateway A network gateway is very similar to a router in that it is designed to connect two separate networks and allow them to communicate. The difference lies in the fact that a router can only connect two networks of the same type (ie. TCP/IP). A gateway, however, connects two dissimilar networks and allows communication. This comparison is similar (abstractly) to that of a telephone line used to by two people to talk over long distances versus a TTY device (a keyboard=>telephone interface used by deaf people to make a phone call) – the two hearing people can simply talk to one another directly (like a router), while the TTY has to translate the typed words into speech for the hearing caller and vice versa for the deaf caller (like a gateway). The most common type of gateway found in the general market is the Residential Gateway, which typically comes in the form of a Cable or DSL modem. This device connects a local area network (LAN) to a wide area network (WAN) or the internet, often also converting the physical connection type from Ethernet to Coaxial or RJ-11 Phone Line. The most common Cable Modem as of now, the DOCSIS 3.0 Motorola SB6121, runs about $70.
Firewall In networking, a firewall is a network security system that controls incoming and outgoing network traffic according to a specified set of rules. Though dedicated physical firewall devices exist (as shown), more commonly found are software firewalls, which are often built into most operating systems, routers, and other devices. The firewall acts as a shield intended to prevent any sort of unwanted packets to cross between trusted and untrusted networks or network segments. Dedicated hardware firewalls, typically found only in corporate environments, run upwards of $200.
Wireless AP (Access Point) Wireless Access Points allow intercommunication between wired (Ethernet) networks and wireless (Wi-Fi) networks. Except in corporate environments, WAPs are mostly found in the form of Wireless Routers, combining the functionality of the two devices. A dedicated WAP is only needed when a router is already present on a network, but either doesn’t have a built-in WAP, or the network covers a physical area larger than the range of the router’s WAP. A dedicated WAP can cost from around $25 to a couple hundred dollars, averaging around $80. WAP Computer
Diagram of All Devices Computer Hub Bridge Wireless AP Switch Hub Router Computer Computer Firewall Computer Gateway