Summary of Ethernet Hub Specifications

[Note: Additional information regarding these specifications can be viewed by selecting the highlighted text.]

• "hot swappable" (module can be replaced without disrupting chassis unit functionality)
• SNMP manageability
• RMON capabilities (may require additional chassis RAM to accomodate all levels of RMON)
• support for auto-partitioning of ports
• chassis protected by UPS

Standalone Hubs

• first hub in stack is SNMP manageable and distributes manageability across hub stack
• RMON capabilities (may require additional RAM to accomodate all levels of RMON)
• support for auto-partitioning of ports
• hub/stack is protected by UPS

OPTIONAL:

• bridging functions (based on IEEE 802.1d Spanning Tree Protocol) at backbone/uplink interface
• rack-mount capability (if used in distributed wiring closet)
• redundant power supplies (if available)
• uplink interface flexibility (to accomodate a variety of backbone media types)

• SNMP Management - See the section on SNMP management in the full UGA Networking Specifications document for a discussion of the critical features needed to manage a switched hub via SNMP.

• Per Port RMON - Each port on the switch must minimally support the first four levels of RMON. See the section on RMON management in the full UGA Networking Specifications document for details.

• Port Mirroring - Hubs that have the ability to mirror at least one port at a time are recommended.

• Spanning Tree - All switches must use IEEE 802.1d spanning tree to detect and eliminate bridging loops.

• MAC Address Table - A switch should have a MAC address table with a minimum of 8,192 entries.

• ASIC Switching - It is imperative that application specific integrated circuits (ASICs) be utilized at the core of the switching engine.

• (No) Back Pressure - Switches that utilize back pressure for congestion control should be avoided.

• Buffering - Given the bursty nature of Ethernet, the best buffering scheme is usually a combination of output buffering with dynamic memory assigned to ports on an as needed basis. [Note: There is no single superior methodology with regard to buffering, and any switch could drop packets if the traffic demands are sufficiently high.]

• Store-and-Forward vs Cut-Through - Switches that only employ store-and-forward methods are strongly recommended. If the switch has both 10 and 100 Mbps ports (asymmetric switching), then store-and-forward switching is *mandatory*.

• Internal Module Bandwidth - See the discussion on internal module bandwidth in the full UGA Networking Specifications document.

• Backplane Bandwidth - See the discussion on backplane bandwidth in the full UGA Networking Specifications document.

• Uplink Options - See Uplink Options in the full UGA Networking Specifications document for a discussion of uplink issues.

• Full Duplex Support - See the discussion on full duplex support in the full UGA Networking Specifications document.

• VLAN Support - See the discussion on virtual LANs in the full UGA Networking Specifications document.

• Broadcast Reduction - It is highly desirable to purchase a switch that can detect broadcast storms and limit the number of broadcast frames that are forwarded to its ports when this condition occurs.

• Filtering - See the discussion on filtering in the full UGA Networking Specifications document.

• Supervisory Modules - See the discussion on supervisory modules in the full UGA Networking Specifications document.