This post is about computer network devices.
- Endpoints
- Network Interconnection Devices
- Network Control Devices
- Network Security Devices
Endpoints
An endpoint is a physical devices, such as a server, PC, workstation or smartphone, that connect to and exchange information with a computer network.
A virtual desktop infrastructure (VDI) virtualizes an endpoint using software.
Network Interconnection Devices
Network Interconnection Devices:
- Repeater
- Hub
- Bridge
- Switch
- Routers
- Network Gateway
Repeater
They have been substituted by switches.
The 5-4-3 rule was related to hubs and repeaters.
It operates at OSI layer 1 (Physical).
Hub
A hub is a computer network device with multiple ports that replicates a received signal through all ports.
The 5-4-3 rule was related to hubs and repeaters.
They have been substituted by switches.
It does not divide the collision segment nor the broadcast segment.
It operates at OSI layer 2 (Data Link).
Bridge
A bridge joins separated networks within one.
When it receives a frame, it only sends it forward if it detects that it belongs to the other LAN.
A bridge uses a spanning tree algorithm.
It operates on OSI layer 2 (Data Link).
A bridge divides collision segments but it does maintain the broadcast segment.
Switch
A switch is a computer network device with multiple ports that distributes a signal through only the port where the destination computer is connected.
It needs to “learn” where the computers are located.
It performs four primary functions:
- Learn: if the MAC source is unknown, the MAC and the port where it was received is registered in the CAM
- Forward: if the MAC destination port is known, its port is known and it is different to the source port, the frame is sent forward to the port
- Drop: if the MAC destination port is known, its port is known and it the same as the source port, the frame is dropped, as it has been received where it should be
- Flood: if the MAC destination port is
A switch usually operates at OSI layer level 2, but some of them may be equipped to operate at layer 3 (L3 switch) or higher (multilayer switch) for special purposes.
A trunk port is a dedicated port with higher bandwidth capacity than the other standard access port. Switches are connected to each other through the trunk port.
A switch divides collision segments but it does maintain the broadcast segment unless VLANs are used.
It operates on OSI layer 2 (Data Link).
Routers
You can find a list of network routing protocols on this post.
Quality of Service (QoS) is a functionality on routers that allow to limit the bandwidth on certain destination or services.
It divides the collision segment and the broadcast segment.
It operates on OSI layer 3 (Network).
Network Gateway
A network gateway, historically known simply as gateway, translates protocols between different networks. For example, it can link a IPv4 network with a IPv6.
Do not confuse a gateway with an application gateway or secure gateway, that are IT security devices.
Network Gateways operates at OSI levels 4-7 (Transport, Session, Presentation and Application).
Network Control Devices
Network control devices:
- Load Balancer
- Proxy
Load Balancer
A load balancer is the device or service that sits between the user and the server group and acts as an invisible facilitator, ensuring that all resource servers are used equally.
Proxy
A proxy server is a server application that acts as an intermediary between a client requesting a resource and the server providing that resource.
Proxy servers can be either a forward proxy or reverse proxy.
A forward proxy is an Internet-facing proxy used to retrieve data from a wide range of sources (in most cases, anywhere on the Internet). It centralizes calls from internal clients towards external server (i.e., the internet), and manage their replies.
A reverse proxy is usually an internal-facing proxy used as a front-end to control and protect access to a server on a private network. It centralizes calls from multiple clients towards a bunch of internal servers, and address the calls to the corresponding server and its reply.
Network Security Devices
Network Security Devices:
- Firewalls
- IDS / IPS
Firewalls
Firewall are network security devices.
You can read more about firewalls and proxies on this post.
IDS / IPS
Intrusion Detection System (IDS), Intrusion Prevention System (IPS).
Host-based IDS (HIDS). An example of HIDS is OSSEC.