LLDP-MED simplifies VoIP deployments

Many companies seeking cost-effective, easily managed VoIP systems face deployment obstacles because of the diversity of convergence products in the marketplace. Corporations also are challenged by the obligation to support Emergency Calling Services (ECS) that include E911, which is often made more difficult by the lack of standards.

The Telecommunications Industry Association (TIA) aims to make it easier to deploy and troubleshoot VoIP networks. The draft TIA standard, Link Layer Discovery Protocol-Media Endpoint Discovery (LLDP-MED), facilitates information sharing between endpoints and network infrastructure devices. Such data will simplify the deployment of endpoints, enable advanced device firmware management and boost support for E911 in enterprise networks.

LLDP-MED is based on the IEEE's 802.1AB LLDP, which is slated to become a standard this month. LLDP is IEEE's neighbor discovery protocol, which can be extended by other organizations. (Click here for a Technology Update on LLDP.) Information gleaned from network devices such as switches and wireless access points aids in troubleshooting and enables management systems to create accurate views of the network's topology.

LLDP-capable devices periodically transmit information in messages called Type Length Value (TLV) fields to neighbor devices. This information includes chassis and port identification, system name, system capabilities, system description and other attributes. LLDP-MED builds upon these capabilities by adding media- and IP telephony-specific messages that can be exchanged between the network and endpoints. The new TLV messages will provide detailed information on Power over Ethernet, network policy, media endpoint location for Emergency Call Services and inventory.

The Power over Ethernet Management TLV lets endpoints advertise the power level and power priority they require, and lets network connectivity devices advertise how much power they can supply. These advertisements let switch vendors support advanced power management. For example, a switch could compare the power required by the endpoint with what it can offer. If it does not have the capacity to meet the demand, it selectively could provide power to endpoints designated as having high priority, such as a lifeline IP phone.

The Network Policy Discovery TLV simplifies deployment of large multivendor networks and aids in troubleshooting. This TLV lets endpoints and switches advertise their virtual LAN ID, IEEE Priority and Differentiated Services Code Point (Layer 3 Priority) assignments to each other. Network administrators can quickly locate misconfigured endpoints. While IEEE 802.1AB is not designed to be used for configuration, it is possible for vendors of endpoints to let these devices modify their settings when a mismatch is discovered between the endpoint and network.

LLDP-MED's Inventory Management Discovery TLV lets an endpoint transmit detailed inventory information about itself to the switch to which it is attached. This information can include vendor name, model number, firmware revision and serial number. When a switch receives this information, it will be stored and be made accessible to the network management system for inventory reporting.