Some of the typical requirements for a small office LAN are:

• Often more balanced data transfers (downloads compared to uploads);
• A limited number of people requiring access, typically with desktops and/or laptops;
• Access by smartphones/tablets may be required;
• Telephone access between office staff members without additional call charges;
• Outgoing telephone connectivity from each staff to the general public;
• Incoming telephone access (either directed to a receptionist or direct to each staff member).

In this scenario, your network would typically comprise of a router/firewall connecting to your ISP with a large switch connecting all your desktops/laptops, plus a small VoIP PABX. Usually wireless connectivity is not required.

The firewall/router will normally be a business-grade model (eg: An appropriate Cisco router) or may be a server or desktop PC configured as a router and firewall and dedicated to that role (NOT used by any staff as a desktop PC), optionally providing additional functionality (such as email mailboxes for staff).