Services Overview
7705 SAR OS Services Guide Page 67
Processing SAP 0 OAM Packets
Note the following points with respect to processing OAM packets on SAP 0:
• the 7705 SAR transmits untagged OAM frames on SAP 0
• the 7705 SAR does not process OAM frames tagged with VLAN ID 0 on a port
configured with null encapsulation
• (for consistency with the 7710 SR), the 7705 SAR processes double-tagged OAM
frames under the following configuration scenario: there is a SAP Up MEP on a
dot1q encapsulated port, using SAP 0, and having VC-type VLAN
In this case, the top VLAN tag is removed and the bottom VLAN tag is assumed to
be SAP 0. If the bottom VLAN tag is not SAP 0, the VLAN ID is changed to 0. If
the frame is an OAM frame, double-tagged is extracted from the SAP Up MEP and
the reply is with a single-tagged frame with its VLAN ID set to 0.
• on a SAP Down MEP (dot1q), untagged frames are processed on SAP 0
• in general, except for the SAP 0 case above, double-tagged (or more) Ethernet OAM
frames are not processed in the SAP
• in the unlikely case that a SAP Up MEP or a spoke SDP Down MEP on the
7705 SAR receives an untagged Ethernet OAM packet on a tagged VC (that is, the
vc-type configuration for the SAP or spoke SDP is VLAN), then the frame is
processed. The reply sent to the originator is a tagged packet on the VC.
MEG-ID and ICC-Based Format
Similar to an 802.1ag MA-ID, a Y.1731 MEG-ID uniquely identifies a group of MEs that
are associated at the same MEG level in one administrative domain. The features of MEG-
IDs are:
• each MEG-ID must be globally unique
• if the MEG may be required for path setup across interoperator boundaries, then the
MEG-ID must be available to other network operators
• the MEG-ID should not change while the MEG remains in existence
• the MEG-ID should be able to identify the network operator that is responsible for
the MEG
The 7705 SAR supports the ITU Carrier Code (ICC-based) MEG-ID format (TLV value
32). The generic and ICC-based MEG-ID formats are defined in the ITU-T Y.1731 standard.
Figure 12 shows the ICC-based MEG-ID format.
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