2.2 Network Communication Devices and Protocols

Data Center Devices and Their Functions

• Types of Network Devices

  • Data centers contain various devices for network communication, including:

  • Single-use devices (e.g., switches)

  • Combination devices (e.g., SoHo routers - integrates switch, router, and wireless access point functionality).

Routers

• Definition: A router forwards network traffic between different IP subnets.

• Functionality:

  • Uses the IP address in packets to identify the next hop toward the destination.

  • Operates at Layer 3 of the OSI model (referred to as Layer 3 devices).

  • Can connect various network types (LAN, WAN, copper, fiber).

Switches

• Definition: A switch connects devices within the same network.

• Functionality:

  • Forwards traffic based on the MAC address of packets (Layer 2 operation).

  • High-speed forwarding due to application-specific integrated circuit (ASIC).

  • Core switches can have multiple interfaces; may support Power over Ethernet (PoE).

Types of Switches

• Unmanaged Switches:

  • Minimal configuration options; connects all devices in one VLAN.

  • No SNMP capabilities for performance checking or error querying.

• Managed Switches:

  • Offer extensive configuration for VLANs and traffic prioritization (e.g., prioritize VoIP over file transfers).

  • Support Spanning Tree Protocol (STP) to prevent loops.

  • Features like port mirroring for troubleshooting and packet analysis.

Access Points

• Definition: Access points extend wired networks into wireless connections.

• Operation:

  • Forwards traffic based on MAC addresses similar to switches.

  • Does not perform routing or network address translations.

Patch Panels

• Purpose: Organize and manage network cable connections between devices.

• Functionality:

  • Permanent cable runs from desks terminate at patch panels, allowing easier device connections.

  • Facilitates quick changes without moving main cables.

Firewalls

• Definition: Control traffic through IP addresses and port numbers (Layer 4 device).

• Advanced Functions:

  • Layer 7 capabilities to understand application layer traffic.

  • Can act as encrypted tunnels (VPN) or proxy servers for secure browsing.

Power over Ethernet (PoE)

• Definition: Technology that delivers electrical power along with data over Ethernet cables.

• Uses: Commonly used with access points, cameras, etc.

• Types of PoE:

  • IEEE 802.3af: 15.4 watts, existing standard.

  • IEEE 802.3at: 25.5 watts, improved standard.

  • IEEE 802.3bt: Type 3 (51 watts) and Type 4 (71.3 watts), designed for high power applications.

Hub vs. Switch

• Hub:

  • Basic device that retransmits data to all interfaces (multiport repeater).

  • Not efficient, operates at half duplex, leading to reduced performance with more devices.

• Switch:

  • Intelligent device that forwards data specifically to intended devices based on MAC addresses.

Internet Connection Devices

• Cable Modem: Enables broadband communication through cable networks (DOCSIS standard).

• DSL Modem: Asymmetric connection over telephone lines; speed varies based on distance from the central office.

• Fiber Connectivity: Utilizes OTNs (Optical Network Terminal) for conversion from fiber to copper Ethernet; establishes demarcation points between ISP and internal networks.

Network Interface Cards (NIC)

• Definition: Hardware that enables Ethernet connections in devices (desktops, servers, etc.).

• NICs can support various connection types (copper, fiber, wireless).