CompTIA A+ 220-1201 (2.3 - Network Services)

DNS server

• Domain Name System

- Convert names to IP addresses

- And vice versa

• Distributed naming system

- The load is balanced across many different servers

• Usually managed by the ISP or IT department

- A critical resource

DHCP server

• Dynamic Host Configuration Protocol

- Automatic IP address configuration

• Very common service

- Available on most home routers

• Enterprise DHCP will be redundant

- Usually running on central servers

File share

• Centralized storage of documents,spreadsheets,

videos, pictures, and any other files

- A fileshare

• Standard system of file management

- SMB (Server Message Block), Apple Filing Protocol (AFP), etc.

• The front-end hides the protocol

- Copy, delete, rename, etc.

Print server

• Connect a printer to the network

- Provide printing services for all network devices

• May be software in a computer

- Computer is connected to the printer

• May be built-in to the printer

- Network adapter and software

• Uses standard printing protocols

- SMB (Server Message Block), IPP (Internet

Printing Protocol), LPD (Line Printer Daemon)

Mail server

• Store your incoming mail

- Send your outgoing mail

• Usually managed by the ISP or the IT department

- A complex set of requirements

• Usually one of the most important services

- 24 x 7 support

Syslog

• Standard for message logging

- Diverse systems, consolidated log

• Usually a central logging receiver

- Integrated into the SIEM

• You're going to need a lot of disk space

- No, more. More than that.

Web server

• Respond to browser requests

- Using standard web browsing protocols - HTTP/HTTPS

- Pages are built with HTML, HTML5

• Web pages are stored on the server

- Downloaded to the browser

- Static pages or built dynamically in real-time

Authentication server

• Login authentication to resources

- Centralized management

• Almost always an enterprise service

- Not required on a home network

• Usually a set of redundant servers

- Always available

- Extremely important service

Database servers

• Database table storage

- Save information in columns and rows

- Similar to a spreadsheet

• Relational database

- Link tables together

- These links are relationships

- Flexible and fast

• Structured Query Language (SQL)

- Access data using a standard language

- Microsoft SQL Server, MySQL, etc.

NTP servers

• The time of day is more important than you might think

- Encryption, logins, backups, log timestamps

- Everything needs to work from the same clock

• NTP server

- Listens on udp/123

- Responds to time requests from NTP clients

• NTP client

- Requests time updates from NTP server

- Daily synchronization is common

Spam gateways

• Unsolicited messages

- Email, forums, etc.

• Various content

- Commercial advertising

- Non-commercial proselytizing

- Phishing attempts

• Significant technology issue

- Security concerns, resource utilization,

storage costs, managing the spam

• Unsolicited email

- Stop it at the gateway before it reaches the user

- On-site or cloud-based

All-in-one security appliance

• Next-generation firewall, Unified Threat

Management (UTM) / Web security gateway

• URL filter / Content inspection

• Malware inspection

• Spam filter

• CSU/DSU

• Router, Switch

• Firewall

• IDS/IPS

• Bandwidth shaper

• VPN endpoint

Load balancers

• Distribute the load

- Multiple servers - Invisible to the end-user

• Large-scale implementations

- Web server farms, database farms

• Fault tolerance

- Server outages have no effect - Very fast convergence

Proxy server

• An intermediate server

- Client makes the request to the proxy

- The proxy performs the actual request

- The proxy provides results back to the client

• Useful features

- Access control, caching, URL filtering, content scanning

SCADA / ICS

• Supervisory Control and Data Acquisition System

- Large-scale, multi-site Industrial Control Systems (ICS)

• PC manages equipment

- Power generation, refining, manufacturing equipment

- Facilities, industrial, energy, logistics

• Distributed control systems

- Real-time information

- System control

• Requires extensive segmentation

- No access from the outside

Legacy and embedded systems

• Legacy systems

- Another expression for "really old"

- May also be "really important"

- Learning old things can be just as important as

learning the new things

• Embedded systems

- Purpose-built device

- Not usual to have direct access to

the operating system

- Alarm system, door security, time card system

IoT (Internet of Things) devices

• Appliances

- Refrigerators

• Smart devices

- Smart speakers respond to voice

• Air control

- Thermostats, temperature control

• Access

- Smart doorbells

• May require a segmented network

- Limit any security breaches