1.3 Overview
This document specifies the Link Layer Topology Discovery (LLTD) Protocol, which operates over Ethernet-like media, including both wired (802.3 Ethernet) and wireless (802.11) media. As the protocol name suggests, its core functions enable applications to discover the link-layer topology of a single link in a network. That is, it is used to facilitate discovering the set of switches and segments that constitute the link. This protocol also has Quality of Service (QoS) extensions that applications can use to diagnose problems, such as those problems that involve signal strength on wireless networks or bandwidth constraints in home networks.
This protocol offers the following services, which operate independently on the network (except as noted in this document):
QoS diagnostics for network tests.
QoS diagnostics for cross-traffic analysis.
There are no dependencies or ordering restrictions between these services, except that the topology discovery test requires that quick discovery is performed first.
Additionally, the concept of charge is central to this protocol. Charge is described in section 1.3.5.