Level 1 - network servers

Common servers and functions

DNS server

DNS names to IP addresses

DNS load is spread across many servers

Managed by ISP or IT department

DHCP server

Automatic IP address config

Available on most home servers

Enterprise DHCP on central servers, redundancy

File server

Centralized file storage (videos, pics, docs, spreadsheets)

Uses standard system for management (SMB or AFP)

Front-end hides protocol (copy, delete, rename, etc)

Print server

Provide printing services for all connected devices

Can be built-in to printer or computer software

Uses standard protocol (SMB, IPP, LPD)

Mail server

Store incoming mail and send outgoing mail

Important to have 24/7 support

Usually managed by ISP or IT

Syslog

A consolidated log for messages

Requires large disk space

usually a central logging receiver

Web server

Responds to browser requests using standard protocol (HTTP/S)

Web pages are stored on the server - both static and dynamic pages

Authentication server

Centralized management of resources that requires authentication

Mostly on enterprise services, very important and redundant

Spam gateway

Stop unsolicited email before it reaches user

Blocks unsolicited ads, phishing, storage costs, etc

Can be on-site or cloud-based

All-in-one security appliance

Can be firewall, unified threat management (UTM), or web security gateway

Functions: URL filter/content inspection, malware inspection, spam filter, CSU/DSU, router/switch, firewall, IDS/IPS, Bandwidth shaper, VPN endpoint

Load balancer

Multiple servers used for large scale implementation

Invisible to end-user

Good for fault tolerance / outages

Features: can configure load across multiple servers, TCP offload, SSL offload (encryption/decryption), caching for fast response, prioritize data (QoS), content switching (App-centric balancing)

Proxy server

Intermediate server

Client makes request to proxy, proxy performs request, proxy provides results to client

Features: Access control, caching, URL filter, content scanning

SCADA / ICS

Supervisory Control and Data Acquisition System, large scale Industrial Control System

PC manages industry equipment: power generator, refining, manufacturing, energy, logistics, facilities, etc

Distributes control systems: Extensive segmentation, no outside access, real-time info

Legacy / embedded systems

Legacy systems are old and important

Embedded systems are purpose built - do not have direct access to OS
Such as alarm system, door security, time card system

Internet of Things (IoT)

Appliances, Smart home devices, thermostat/temp control, smart doorbell

Recommend segmented network to limit security breaches