VPWS Binding Config Table. This table configures bindings of Attachment Circuits (ACs) to VPWS instances, pseudowires (PWs), and layer 2 local switching rules (hairpins). Multiple ACs can be associated with a single VPWS. If the binding corresponds to two VPWS sites that are hosted by a single PE router, a hairpin can be created between the two sites' ACs. Otherwise, a PW set is used to establish connectivity. The method for associating ACs with PWs depends on whether auto-discovery is enabled. - If auto-discovery is disabled (vpwsConfigADType = none) then PWs are provisioned in the pwTable. In this case, each AC is bound to a set of provisioned PWs, that are identified by a PW Set Index. PW redundancy configuration is not yet supported by L2VM provisioned PWs, therefore the PW Set will have a single member, and this set index can be set to the pwIndex in the pwTable of that PW. This form of binding is known as a double-sided binding since the PW(s) must be provisioned in the pwTable at each end of the virtual circuit. - If auto-discovery is enabled (vpwsConfigADType = bgp) then the VPWS service establishes a PW between each pair of VPWS sites within the VPWS, using BGP auto-discovery to determine which PE router hosts each VPWS site. In this case, each AC is bound to a PW that is identified by the local and remote site IDs. The PE router creates these PWs automatically as a result of the BGP auto-discovery process. This form of configuration is sometimes known as 'colored pools'. In this approach the operator configures a pool of ACs for each local site, and each pool is identified by a site ID or 'color'. The VPWS service establishes a PW between each pair of 'colored pools' (VPWS sites), and each AC is bound to a PW associated with the same 'colored pool' (local site ID). - If auto-discovery is enabled (vpwsConfigADType = bgp) then an AC can still be bound to a PW that is provisioned in the pwTable MIB, for example to incorporate a legacy PE router that does not support auto-discovery into the VPWS. The method for associating ACs with other ACs in a hairpin also depends on whether auto-discovery is enabled. - If auto-discovery is disabled, the AC is bound to another AC directly, by configuring its interface index in this table. In this case the PW set index can also optionally be specified to provide redundant connectivity to the other site. - If auto-discovery is enabled, the BGP auto-discovery process ascertains that this PE router also hosts the remote site, and automatically binds the two ACs. In either case a row in this table only establishes unidirectional connectivity for a hairpin. For full connectivity, the opposite direction will need to be configured in the same manner (though this need not be in the same VPWS instance). Each VPWS Binding is configured with a PW binding type, given by vpwsBindCfgPwBindType, which specifies whether the PW Set to which the AC is bound is identified by a PW Set index and/or hairpin interface index (and so is provisioned) or by a local and remote site ID (and so is auto-created as a result of BGP auto-discovery). This table is indexed on AC interface index to ensure that each AC is only ever bound to a single VPWS. The read-only vpwsBindTable can be used to show the ACs bound to each VPWS. Note that changes to this table may cause the corresponding AC to go operationally down as it may involve re-programming the AC in the data plane.