Layer 2 Control Protocols (L2CPs) are used for several purposes in IEEE 802 standard networks, including link maintenance, aggregation, [fllig ]ow control, authentication, identity/capability discovery and management. L2CPs are also used for managing the behavior of LAN bridges, including STP/RSTP/MSTP and GARP/MRP. The VLNC40/42/42B circuit packs support L2CP tunneling. A L2CP frame is identified by the destination MAC address.
Ethernet service provider LAN bridging equipment is normally prohibited (by standards) from forwarding L2CP messages/frames across the network, to other LAN segments. An Ethernet service provider’s equipment is required to either participate in L2CPs with customer equipment, or discard all such L2CP frames. When a supported VLNC40/42/42B protocol is enabled on a port, software interprets customer L2CP frames of the relevant type on that port, and sends response(s) to peer NEs, as appropriate. This capability is called “peering.”
Each supported protocol may be selectively disabled on an individual port. In this case, the VLNC40/42/42B simply discards (does not forward them to any other NE) received L2CP frames of the relevant type.
The VLNC40/42/42B discards any received L2CP frames associated with all unsupported protocols.
|
Supported protocols |
Enable/Disable command |
|---|---|
|
Flow Control: 802.3x 1 |
storm-control flowcontrol |
|
Spanning Tree: xSTP 1 |
spanning-tree port mode |
|
Link aggregation control: LACP 1 |
port lacpmode |
|
Link OA&M: 802.3 Clause 57 |
linkoam enable |
If a network operator wants to provide its customer a LAN segment interconnect hub service, or a direct host-to-host Ethernet interconnect service, it needs to be able to tunnel L2CP frames between customer endpoints. The Alcatel-Lucent 1850 TSS-5 VLNC40/42/42B can be configured to support this capability.
On the VLNC40, L2CP Tunneling (l2cp-tunnel) can be enabled or disabled on a port-by-port basis. When the mode is disabled, all the rules and characteristics described for the peering of supported protocols apply. When the l2cp-tunnel mode is enabled on a port, all customer L2CP frames/messages for supported and unsupported protocols that are received at that port are forwarded. Because the tunneled protocol is either disabled or unsupported, VLNC40/42/42B does not interpret any of the frames associated with a tunneled protocol.
L2CP Tunneling must be enabled on the terminating customer LAN/host port, as well as all Ethernet ports carrying the tunneled frames at all nodes through the network. Layer 2 control protocol tunneling may not be enabled on ports that are part of a protected Ethernet ring. Beginning in R6.0, PAUSE frames (Ethernet Flow Control) and SSM frames (Synchronous Ethernet source Management) are not tunneled.
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