L2CP over Epipe and VPLS (7210 SAS-X)

Layer 2 Control Processing (L2CP):

Operators providing Epipe service need to be able to transparently forward Layer-2 control frames received from the customers. This allows their customers to run these control protocols between the different locations which are part of the L2 VPN service. The 7210 SAS platforms provide user with the following capability:

• An option to tunnel, discard or peer for EFM OAM, LLDP, Dot1x, and LACP.

• BPDU translation and Layer 2 Protocol Tunnelling support for xSTP and CISCO control protocols. This is supported only in a VPLS service. For more information, see the “L2PT and BPDU Translation on page 284”.

NOTE: The CDP, VTP, DTP, PAgP, and UDLD management protocols, are forwarded transparently in an Epipe service.

 

By default, LACP, LLDP, EFM OAM, and Dot1x Layer-2 control protocol untagged packets are discarded if the protocol is not enabled on the port where these frames are received. User has an option to enable peering by enabling the protocol on the port and configuring the appropriate parameters for the protocol. User also has an option to tunnel these packets using an Epipe or VPLS service.

 

In a VPLS service, the layer-2 control frames are sent out of all the SAPs configured in the VPLS service. It is recommended to use this feature carefully and only when an VPLS is used to emulate an end-to-end Epipe service (that is, an Epipe configured using a 3-point VPLS Service, with one access SAP and 2 access-uplink SAP/SDPs for redundant connectivity). In other words, if the VPLS service is used for multipoint connectivity, it is not recommended to use this feature. When a layer-2 control frame is forwarded out of dot1q SAP or a QinQ SAP, the SAP tags of the egress SAP are added to the packet.

 

The following SAPs can be configured for tunnelling the untagged L2CP frames (corresponding protocol tunnelling needs to be enabled on the port):

• If the port encapsulation is null, user has an option to tunnel these packets by configuring a NULL SAP on a port

• If the port encapsulation is dot1q, user an option to use dot1q explicit null SAP (e.g. 1/1/ 10:0) or a dot1q default SAP (For example: 1/1/11:*) to tunnel these packets.

• If the port encapsulation is QinQ, user has an option to use 0.* SAP (For example 1/1/ 10:0.*) to tunnel these packets.

 

In addition to the protocols listed above, protocols that are not supported on 7210, For example: GARP, GVRP, ELMI, and others are transparently forwarded in case of a VPLS service. These protocols are transparently forwarded if a NULL SAP, dot1q default SAP , dot1q explicit null SAP or 0.* SAP is configured on the port and received packet is untagged. If the received packet is tagged and matches the tag of any of the SAPs configured on the port, it is forwarded in the context of the SAP and the service. Else if the received packet is untagged and none of the NULL or dot1q default or dot1q explicit null or 0.* SAP is configured, it is discarded.

 

If a 7210 receives a tagged L2CP packet on any SAP (includes NULL, dot1q, dot1q range, QinQ, QinQ default), it is forwarded transparently in the service similar to normal service traffic (xSTP processing behaviour is different in VPLS service and is listed below).

 

The xSTP processing behaviour in a VPLS service is as follows:

• If xSTP is enabled in the service , and if the tag in the STP BPDU matches the tag of the configured SAP, the received xSTP BPDU is processed by the local xSTP instance on the node for that service when xSTP is enabled on the SAP and discarded when xSTP is disabled on the SAP.

• If the tags do not match, xSTP BPDU packets are transparently forwarded in the service similar to normal service traffic.

• If xSTP is disabled in the service, STP BPDU packets are transparently forwarded in the service similar to normal service traffic

 

Packet Type                7210 SAS-X

LACP                           Option to Tunnel or Discard or Peer

Dot1x                          Option to Tunnel or Discard or Peer

LLDP                           Option to Tunnel or Discard or Peer (see Notes1)

EFM                            Option to Tunnel or Discard or Peer

L2PT                           Supported (see Note2)

BPDU Tunnelling Supported

xSTP                          Option to Peer or Tunnel

 

Note1: For more information read the 7210 SAS Interfaces guide to know more about options available for LLDP tunnelling.

Note2: L2TP support on 7210 SAS platforms varies among the platforms. Not all platforms support tunnelling of all CISCO protocols. For more information, see “L2PT and BPDU Translation on page 284”.

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