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Posts about Ethernet

Ethernet Linktrace (ETH-LT)

Networking software Layer 2 OAM (Operations, Administration and Maintenance) Ethernet

The IEEE 802.1ab Ethernet linktrace (ETH-LT) function is primarily responsible for restarting the adjacency relationship and helping to locate faults. Otherwise known as a MAC trace route, ETH-LT are multicast messages that a source endpoint sends to track the hop-by-hop path to a destination device. Within a 5 second period, each intermediate device the received the linktrace datagram returns a trace route reply to the originating equipment and regenerates the ETH-LT message on to its destination. The ETH-LT PDU includes fields for a Transaction ID, Time-to-Live (TTL), origin and target MAC addresses.

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Ethernet Frame Loss Measurement (ETH-LM)

Networking software Layer 2 OAM (Operations, Administration and Maintenance) Ethernet

One of the key objectives of OAM is to measure quality-of-service (QoS) attributes, such as frame delay, frame delay variation (“frame jitter”) and frame loss. Such measurements enable you to identify network problems before customers are impacted by network defects. IEEE 802.1ab Ethernet frame loss measurement (ETH-LM) operates between associated end points configured on either physical Ethernet or logical VLAN interfaces. Near end and far end frame loss measurements are performed by sending frames with ETH-LM information to a peer endpoint and similarly receiving frames with ETH-LM information from the that peer. This type of frame loss measurement is also known as single-ended Ethernet loss measurement.

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Ethernet Loopback (ETH-LB)

Networking software Layer 2 OAM (Operations, Administration and Maintenance) Ethernet

The IEEE 802.1ab ETH-LB is unicast message used to check whether a fault occurs on the link between the local and peer terminal equipment. On receiving the loopback message, the endpoint checks whether conditions are met. If so, the receive node returns a loopback reply (LBR) packet (another unicast MAC message) to the originating device. The source node reports an alarm if it does not receive any LBR within five seconds after sending the LBM. As intermediate nodes perform only Layer 2 forwarding, LBMs can carry additional data that must be returned in LBRs without change. LBMs can therefore also be used for traffic test purposes.

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Ethernet Delay Measurement (ETH-DM)

Networking software Layer 2 OAM (Operations, Administration and Maintenance) Ethernet

The IEEE 802.1ab frame delay measurement (ETH-DM) function is used for on-demand operation administration and maintenance (OAM). ETH-DM is employed when measuring the frame delay (FD) and frame delay variation (FDV), where the FD refers to the interval between the time when the first bit of a frame is transmitted by a source node and the time when the last bit of the frame is received by the same source node after the frame is looped back. Frame loopback is performed by the destination node of the test. ETH-DM allows the FD and FDV measurements to be performed on each endpoint in two distinct modes: one way, or unidirectional, where the endpoint clocks are not synchronized and two-way, or bidirectional, where they are.

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Ethernet Continuity Check (ETH-CC)

Networking software Layer 2 OAM (Operations, Administration and Maintenance) Ethernet

Confined to a domain or VLAN, multicast IEEE 802.1ag Ethernet Continuity Check (ETH-CC) heartbeat messages are exchanged periodically between endpoints, thereby allowing them to discover each other or any intermediary devices. These OAM messages can detect the loss of a link and incorrect network connections. When these connectivity failures occur within a specific maintenance association, ETH-CC and can be used to trigger protection switching within 3.33ms. Hardware and software faults can also be detected with continuity check messages. Read More

Link Management Protocol (LMP)

Networking software MPLS (Multi-Protocol Label Switching) Ethernet Link Management Protocol (LMP)

Link Management Protocol (LMP) is designed to ease the configuration and management of optical network devices. Such devices may be interconnected by thousands of data-bearing links, which are aggregated into a smaller number of traffic engineering (TE) links. LMP provides automatic configuration of such devices, negotiation of capabilities, and localization of faults.

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Spanning Tree Protocol (STP)

Networking software Layer 2 Ethernet

Ethernet frames may be broadcast through the network with a header that does not contain a TTL. If the topology contains a loop, this leads to a broadcast storm with frames being broadcast indefinitely. The IEEE 802.1D Spanning Tree Protocol (STP) prevents bridge loops and the broadcast storms that result from them by disabling links and leaving a single active path between two network nodes. STP also facilitates a redundant link that is automatically instantiated in the event a primary link fails. STP variants include Rapid Spanning Tree Protocol (RSTP) for rapid convergence and Multiple Spanning Tree Protocol (MSTP) that enables load-balancing across different groups of VLANs.

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Link Layer Discovery Protocol (LLDP)

Networking software Layer 2 Ethernet

Specified within the IEEE 802.1AB standard, the Link Layer Discovery Protocol (LLDP) is used by network devices in Ethernet segments and networks for advertising their identity, capabilities, and neighbors. The Link Layer Discovery Protocol may be used as a component in network management and monitoring applications, such as data center bridging. Providing a mechanism for endpoints to exchange configuration information, the implementation of LLDP is critical for preventing configuration mismatches.

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Link Aggregation Control Protocol

Networking software Layer 2 Ethernet

Defined within IEEE 802.3ad, the Link Aggregation Control Protocol (LACP) is a standards-based method to control the bundling of several physical network links together to form a logical channel for increased bandwidth and redundancy purposes. LACP enables a network device to negotiate an automatic bundling of links by sending LACP packets to the peer. By sending specialized frames down links with the protocol enabled, LACP dynamically configures these peers and failover occurs automatically when a link fails.

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Ethernet Ring Protection Switching

Networking software Layer 2 Ethernet

In network operator infrastructures around the globe, cost-effective optical Ethernet services are increasingly replacing classic SONET/SDH technology in the metro/access network layers and beyond. Truly substituting SONET or Ethernet, however, demands replicating the resilient ring topologies to reduce the number of links required in multipoint configurations while also matching the sub 50ms automatic protection switching timeframes required of the attached devices without an underlying SONET/SDN transport layer in place.

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