Functions of a SOHO Router

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Small office/home office (SOHO) is a category of LAN with a small number of computing hosts that typically rely on a single integrated appliance for local and Internet connectivity.

• powered by SOHO router
  • primary function is to forward traffic between LAN and WAN
• can use the OSI model to analyze each of the functions of a SOHO router

Physical Layer Functions

• At physical layer, the SOHO router provides the following interfaces:
  • RJ45 ports (usually 4)
    • for local cabled network
    • typically labeled as LAN ports
  • Radio antennae
    • transmit and receive wireless signals
  • type of modem
    • connect to the ISP’s network
    • typically labeled as WAN port

Data Link Layer Functions

• Layer 2 functions:
  • Ethernet switch
    • RJ45 jacks connected internally by an Ethernet switch
  • Wireless access point
    • radio antennae implements a version of Wi-Fi standard
    • access point functions as a wireless hub
    • access point is wired to the Ethernet switch via internal port
    • forms a bridge between cabled and wireless segments, creating a single logical Data Link network
• each host interface is identified by a media access control (MAC) address

Network Layer Functions

• SOHO router makes forwarding decisions between private local network and public internet
• zones are distinguished by IP addresses
  • local network uses private address range
• router runs a DHCP server to allocate a unique address to each host
• router’s WAN interface is allocated a public IP address by the ISP

Transport and Application Layer and Security Functions

• network security is a matter of allowing or preventing devices, users, and services from using the network
• WAN interface is the network perimeter
• SOHO router can implement a firewall with filtering rules
• At transport layer, each application is identified by a port number
  • firewall can specify rules for each port