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For example, the user can send a loopback message (LBM) as a single event or repetitively. The latter includes verifying bandwidth throughput or detecting bit errors.
#Ethernet loopback testing update
LoC can be used to issue traps to the management system, to update the alarm log, and optionally to initiate a switchover to a protection link.įigure 4 shows that loopback tests are necessary when conducting connectivity and diagnostic tests. If the tester misses three CCMs, it declares loss of continuity (LoC), which is cleared when the tester detects two consecutive CCMs.
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#Ethernet loopback testing verification
Some of the more important functions are described below.Ĭontinuity check: Figure 3 illustrates that continuity check message (CCM) verification is among the most important CFM tests because it: They also enable detection and isolation of a connectivity fault to a specific bridge or LAN. These enable discovery and verification of the path through bridges and LANs taken from frames addressed to and from specified network users. This standard specifies protocols, procedures, and managed objects in support of connectivity fault management. These capabilities can be used in networks operated by multiple independent organizations, each with restricted management access to each other's equipment. The Connectivity Fault Management (CFM) standard specifies protocols and protocol entities within the architecture of VLAN-aware bridges that enable the detection, verification, and isolation of connectivity failures in virtual bridged LANs (VBLANs). Link monitoring delivers event notifications, such as status and diagnostics information, that are stored in local management information bases (MIBs), where peers can pull them. The remote loopback is a link-layer mechanism that operates at the frame level. With remote failure indication, network devices can notify peer devices in the event of failures. Low Ethernet capital expenditures (capex) shift the profitability focus to opex, and Ethernet OAM is key to managing Ethernet service opex.ĭuring the network initialization, adjacent devices exchange identification information and OAM capabilities.
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The new standards will provide new OAM capability to the customer premises demarcation point, potentially reducing operating expenses (opex) by more than half.
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However, standards exist to address most of the issues. Thus, any carrier-grade technology must transport TDM-based traffic at performance levels similar to circuit-based technologies.Įthernet OAM provides a key challenge that must be overcome before Ethernet is ready for mass marketing in carrier networks. Also in the event of failures, rapid fault identification and localization are essential in large networks, driving the demand for carrier-grade OAM functions.įinally, while packet traffic represents the fastest-growing segment in user traffic, the demand for TDM traffic remains robust. In the event of hard failures, users expect protection schemes that can deliver performance at or below 50 msec. Carrier Ethernet must provide service differentiation so that those critical applications receive the necessary quality.Īnother attribute related to these critical applications revolves around protection and restoration. Some applications are more critical and, therefore, are delivered at premium prices. The simultaneous use of services by a large number of subscribers and applications leads to resource conflicts and congestion. Native Ethernet was designed with the target of servicing much smaller groups of users in campuses and enterprises, but carrier-grade Ethernet must deliver scalability similar to conventional carrier networks (see Figure 1). These technologies require new methods and tools for qualification in labs and in the field.Ĭarrier Ethernet networks offer transport for millions of end users and connectivity among final users as well as among client networks. Provider Backbone Bridge/Provider Backbone Transport (PBB/PBT) Transport Multiprotocol Label Switching/Multiprotocol Label Switching Transport Profile (T-MPLS/MPLS-TP) Ethernet operation, administration, and maintenance (OAM) Synchronous Ethernet and TDM over IP (TDMoIP) are some examples of major initiatives for carrier-grade Ethernet. The Ethernet community has been continuously adding capabilities to native Ethernet to deliver a carrier-grade transport alternative to legacy TDM technologies.