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11.4.7 Internet Appliances

Learn about the different Internet appliances network administrators use to promote safety, speed and efficiency for their enterprise networks.

The following appliances ensure network uptime, security, and resource availability. They come in two forms: embedded or software-based. Embedded Internet appliances come with an entire system, combining the necessary hardware and software into one device. Software-based appliances are just as they sound - they come in software. They can also run on two layers, the network and the application layer.

Load Balancers

Load balancers are appliances that split incoming traffic across the multiple servers larger enterprise networks have to handle those requests. They use a specific algorithm to determine which server handles the most recent request.

Algorithm Description Risky?
Round Robin The load balancer gives the latest requests to the servers in sequential order. Yes
Weighted Round Robin The same as round robin, but now the algorithm considers each server's power. More powerful servers are sent more requests. Not really
Least Connections The load balancer sends incoming requests to the server that currently has the least amount of connections. Yes
Weighted Least Connections Considers both the connection count and the processing power available by each server before choosing a server to send the incoming request to. Not really
Source IP Hash Upon a new connection, the load balancer creates a hash from the Source IP and the Target IP, and assigns a server to handle requests matching that hash from now on. Not really
Least Pending Requests Sends incoming requests to the most available server, allowing for adjustments in case of a sudden rise in requests.
This algorithm only runs in application-layer load balancers.		 No

Spam Gateways

Spam gateway appliances monitor incoming and outgoing emails to reduce the amount of spam requests that might actually get processed by the server.

  • Ensuring incoming email sender addresses aren't part of a blocklist
  • Using email authentication technologies like Domain-based-Message-Authentication,-Reporting,-and-Conformance
  • Checking all embedded links in an email for malicious destinations

Proxy Servers

Proxy servers act as a guardian shield between the incoming traffic and the servers that will be processing them. Network administrators can configure proxy servers to check the type of incoming traffic, and block or allow them through if they meet certain conditions.

  • When a client computer requests an allowed website, the proxy server lets the traffic through and caches a copy of the website
  • When a second request of the website is made, the proxy server returns the cached site instead of letting the traffic through (performance boost; eliminates repetitive queries/requests)
  • Sites are re-cached at predetermined intervals so outdated site info doesn't get sent off to the client computers

Unified Threat Management (UTM) Appliances

A UTM appliance combines the function of several network safety features:

  • firewalls
  • intrusion prevention systems
  • anti-malware / antivirus
  • content filters
  • routing functions
  • VPN support

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