on process involves a number of steps: 1. The exchange of BeginVerify/BeginVerifyAck/BeginVerifyNack messages between the LMP nodes to initiate link verification. The BeginVerify message that is sent by the initiating node includes the ID of the traffic-engineering link whose fibers it intends to test. 2. The sending of Test messages down the links to be tested one after another, together with timer/retry processing. Note that this message is transmitted on the particular data link being verified, not sent via the normal IP control channel. The receiving node checks for light on each fiber that it believes makes up its end of the specified traffic- engineering link. 3. The exchange of TestStatusFail/TestStatusSuccess/TestStatusAck messages to report the results of data link tests. 4. The exchange of EndVerify/EndVerifyAck. The results of the link verification process, as illustrated in Figure 8-8, The determination of which data links have tested successfully The mappings between the local and remote interface IDs for the data links The mappings between the local and remote interface IDs for the traffic-engineering links 8.6.4 Link Property Summarization The main purpose of this function is to discover and agree between two adjacent LMP nodes on interface ID mappings and data link properties. Chapter 8 Figure 8-8 Link verification table. Node A Node B Local Remote Local Remote This is achieved by the exchange of LinkSummary/LinkSummaryAck/ LinkSummaryNack messages, each of which contains multiple subobjects. These subobjects include Traffic-engineering link subobjects indicate the mappings between local and remote traffic-engineering link IDs, together with other information about the traffic-engineering links (such as protection and multiplex capability). Each traffic-engineering link aggregates multiple data links, which is indicated by the subsequent data link subobjects. Data link subobjects indicate the mappings between local and remote interface IDs (as determined by link verification or by manual configura